Vwop

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/core/nms/v26_2_R1/IrisChunkGenerator.java

@@ -4,7 +4,7 @@ import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.GenerationSessionException;
 import art.arcane.iris.engine.framework.GenerationSessionLease;
 import art.arcane.iris.engine.framework.IrisStructureLocator;
-import art.arcane.iris.engine.framework.NativeStructurePlacementPlanner;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
 import art.arcane.iris.engine.framework.NativeStructureStartPlan;
 import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
 import art.arcane.iris.engine.object.IrisDimension;
@@ -14,11 +14,15 @@ import art.arcane.iris.nativegen.NativeStructureGenerationException;
 import art.arcane.iris.nativegen.NativeStructureStartInjector;
 import art.arcane.iris.nativegen.NativeStructureReferenceEnvelope;
 import art.arcane.iris.nativegen.NativeStructureLocateResults;
+import art.arcane.iris.nativegen.NativeStructureLocatePersistence;
+import art.arcane.iris.nativegen.NativeStructureOwnershipRecovery;
 import art.arcane.iris.nativegen.NativeStructurePostProcessor;
+import art.arcane.iris.nativegen.NativeStructureReferenceRepair;
 import art.arcane.iris.nativegen.NativeStructureSurfaceFitter;
 import art.arcane.iris.nativegen.NativeStructureTerrainIntegrator;
 import art.arcane.iris.nativegen.NativeStructureVegetationClearer;
 import art.arcane.iris.nativegen.NativeStructureVerticalPlacer;
+import art.arcane.iris.nativegen.NativeStructureVanillaLocator;
 import art.arcane.iris.nativegen.WorldgenTerrainHeightmaps;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.iris.util.common.data.IrisCustomData;
@@ -87,6 +91,7 @@ import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -131,55 +136,99 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
     public @Nullable Pair<BlockPos, Holder<Structure>> findNearestMapStructure(ServerLevel level, HolderSet<Structure> holders, BlockPos pos, int radius, boolean findUnexplored) {
         try (GenerationSessionLease lease = requireGenerationLease("bukkit_nms_structure_locate");
              IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
-            Pair<BlockPos, Holder<Structure>> irisPlaced = findNearestIrisStructure(
-                    level, holders, pos, Math.max(1, radius), findUnexplored);
             HolderSet<Structure> reachable = filterReachableStructures(level, holders);
-            Pair<BlockPos, Holder<Structure>> nativeLocated = reachable == null || reachable.size() == 0
-                    ? null
-                    : delegate.findNearestMapStructure(level, reachable, pos, radius, findUnexplored);
-            return NativeStructureLocateResults.nearest(pos, irisPlaced, nativeLocated);
+            NativeStructureVanillaLocator.Candidate nativeCandidate =
+                    reachable == null || reachable.size() == 0 ? null
+                            : NativeStructureVanillaLocator.predict(
+                                    level, reachable, pos, radius, findUnexplored);
+            return findNearestIrisStructure(
+                    level, holders, pos, Math.max(0, radius),
+                    findUnexplored, nativeCandidate);
         }
     }
 
     private Pair<BlockPos, Holder<Structure>> findNearestIrisStructure(ServerLevel level,
                                                                        HolderSet<Structure> holders,
                                                                        BlockPos pos, int radius,
-                                                                       boolean findUnexplored) {
-        if (findUnexplored) {
-            return null;
-        }
+                                                                       boolean findUnexplored,
+                                                                       NativeStructureVanillaLocator.Candidate nativeCandidate) {
+        Pair<BlockPos, Holder<Structure>> nativeLocated =
+                nativeCandidate == null ? null : nativeCandidate.result();
+        Runnable nativeReference = () -> {
+            if (nativeCandidate != null) {
+                nativeCandidate.reference(level.structureManager());
+            }
+        };
         Registry<Structure> registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE);
-        BlockPos best = null;
-        Holder<Structure> bestHolder = null;
-        long bestDist = Long.MAX_VALUE;
+        List<IrisNativeLocateSearch> searches = new ArrayList<>(holders.size());
+        NativeStructureLocatePersistence.ProbeBudget budget = NativeStructureLocatePersistence.probeBudget();
         for (Holder<Structure> holder : holders) {
             Object id = registry.getKey(holder.value());
             if (id == null) {
                 throw new IllegalStateException("Native structure locate received an unregistered structure holder");
             }
             String structureId = id.toString();
-            if (!IrisStructureLocator.isPlaced(engine, structureId)) {
+            if (!IrisStructureLocator.hasNativePlacement(engine, structureId)) {
                 continue;
             }
-            IrisStructureLocator.LocateResult result = IrisStructureLocator.locate(
-                    engine, structureId, pos.getX(), pos.getZ(), radius);
-            if (result.status() == IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED) {
-                throw new IllegalStateException("Iris structure locate reached its safety limit for "
-                        + structureId + " within " + radius + " chunks");
-            }
-            if (!result.found()) {
-                continue;
-            }
-            long dx = (long) result.originX() - pos.getX();
-            long dz = (long) result.originZ() - pos.getZ();
-            long d = dx * dx + dz * dz;
-            if (d < bestDist) {
-                bestDist = d;
-                best = new BlockPos(result.originX(), result.baseY(), result.originZ());
-                bestHolder = holder;
-            }
+            NativeStructureLocatePersistence.Probe probe = NativeStructureLocatePersistence.probe(
+                    level, holder.value(), findUnexplored, budget);
+            searches.add(new IrisNativeLocateSearch(
+                    holder, structureId, NativeStructureLocatePersistence.search(
+                    engine, structureId, pos.getX(), pos.getZ(), radius, probe)));
         }
-        return best == null ? null : Pair.of(best, bestHolder);
+        searches.sort(Comparator.comparing(IrisNativeLocateSearch::structureId));
+        for (int attempt = 0; attempt < NativeStructureLocatePersistence.MAX_SELECTED_CANDIDATE_RETRIES; attempt++) {
+            IrisNativeLocateSearch bestSearch = null;
+            IrisStructureLocator.LocateResult bestResult = null;
+            long bestDistance = Long.MAX_VALUE;
+            for (IrisNativeLocateSearch search : searches) {
+                IrisStructureLocator.LocateResult result = search.search().predict();
+                if (result.status() == IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED) {
+                    throw new IllegalStateException("Iris structure locate reached its safety limit for "
+                            + search.structureId() + " within " + radius + " placement rings");
+                }
+                if (!result.found()) {
+                    continue;
+                }
+                long dx = (long) result.originX() - pos.getX();
+                long dz = (long) result.originZ() - pos.getZ();
+                long distance = dx * dx + dz * dz;
+                if (distance < bestDistance) {
+                    bestDistance = distance;
+                    bestSearch = search;
+                    bestResult = result;
+                }
+            }
+            if (bestSearch == null) {
+                return NativeStructureLocateResults.selectAndReference(
+                        pos, null, () -> { }, nativeLocated, nativeReference);
+            }
+            Pair<BlockPos, Holder<Structure>> predicted = Pair.of(
+                    new BlockPos(bestResult.originX(), bestResult.baseY(), bestResult.originZ()),
+                    bestSearch.holder());
+            if (NativeStructureLocateResults.nearest(pos, predicted, nativeLocated) != predicted) {
+                return NativeStructureLocateResults.selectAndReference(
+                        pos, predicted, () -> { }, nativeLocated, nativeReference);
+            }
+            NativeStructureLocatePersistence.VerifiedStart verified =
+                    bestSearch.search().verify(bestResult);
+            if (verified == null) {
+                bestSearch.search().reject(bestResult);
+                continue;
+            }
+            BlockPos located = new BlockPos(
+                    bestResult.originX(), verified.ownership().locatorY(),
+                    bestResult.originZ());
+            Pair<BlockPos, Holder<Structure>> irisLocated = Pair.of(located, bestSearch.holder());
+            IrisNativeLocateSearch selectedSearch = bestSearch;
+            NativeStructureLocatePersistence.VerifiedStart selectedStart = verified;
+            return NativeStructureLocateResults.selectAndReference(
+                    pos, irisLocated, () -> selectedSearch.search().reference(selectedStart),
+                    nativeLocated, nativeReference);
+        }
+        throw new IllegalStateException("Iris structure locate rejected too many selected candidates within "
+                + radius + " placement rings");
     }
 
     private HolderSet<Structure> filterReachableStructures(ServerLevel level, HolderSet<Structure> holders) {
@@ -323,9 +372,10 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
                         decision.preserveSourceY(),
                         decision.yBand(),
                         (x, z) -> engine.getHeight(x, z, true) + engine.getMinHeight());
-                StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
-                        start, structure, start.getReferences(), templateManager,
-                        NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain()));
+                StructureStart wrapped = NativeStructureReferenceEnvelope.wrapForPublication(
+                        start, structure, start.getReferences(),
+                        NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain()),
+                        structureId);
                 access.setStartForStructure(structure, wrapped);
             } catch (Throwable error) {
                 throw NativeStructureGenerationException.failure(
@@ -341,7 +391,11 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public void createReferences(WorldGenLevel generatoraccessseed, StructureManager structuremanager, ChunkAccess ichunkaccess) {
-        delegate.createReferences(generatoraccessseed, structuremanager, ichunkaccess);
+        try (GenerationSessionLease lease = requireGenerationLease("bukkit_nms_create_references");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            NativeStructureReferenceRepair.createReferences(
+                    engine, generatoraccessseed, structuremanager, ichunkaccess);
+        }
     }
 
     @Override
@@ -474,7 +528,6 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
         int steps = GenerationStep.Decoration.values().length;
         List<NativePlacementGroup> placementGroups = new ArrayList<>();
         List<StructureStart> heightmapStarts = new ArrayList<>();
-        List<StructureStart> nativeStarts = new ArrayList<>();
         List<NativeStructureVegetationClearer.VegetationTarget> vegetationTargets = new ArrayList<>();
         List<NativeStructureTerrainIntegrator.TerrainTarget> terrainTargets = new ArrayList<>();
         for (int step = 0; step < steps; step++) {
@@ -492,10 +545,11 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
                     List<StructureStart> starts = structureManager.startsForStructure(sectionPos, structure);
                     List<NativePlacement> resolvedPlacements = new ArrayList<>(starts.size());
                     for (StructureStart start : starts) {
-                        NativeStructureStartPlan plan = NativeStructurePlacementPlanner.matchingPlan(
-                                engine, structureId, start.getChunkPos().x(), start.getChunkPos().z());
-                        IrisNativeStructureDecision decision = plan == null
-                                ? sourceDecision : NativeStructurePlacementPlanner.decisionFor(plan);
+                        NativeStructureOwnershipRecord ownership =
+                                NativeStructureOwnershipRecovery.resolve(
+                                        engine, world.getLevel(), structureId, structure, start);
+                        IrisNativeStructureDecision decision =
+                                ownership == null ? sourceDecision : ownership.restoredDecision();
                         if (!decision.generate()) {
                             continue;
                         }
@@ -505,9 +559,6 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
                                 structureId, start,
                                 NativeStructureTerrainIntegrator.resolveNativeTerrain(
                                         start, decision.terrain())));
-                        if (plan == null || !plan.placement().isUnderground()) {
-                            nativeStarts.add(start);
-                        }
                         boolean clearEntireFootprint = NativeStructureVegetationClearer
                                 .shouldClearEntireVegetationFootprint(
                                         structure.step(), decision.clearVegetation());
@@ -533,15 +584,6 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
                     "heightmap priming", nativeStructureBatchContext(placementGroups),
                     chunkPos.x(), chunkPos.z(), error);
         }
-        try {
-            NativeStructureSurfaceFitter.prepareSurfaceStructures(
-                    world, area, nativeStarts,
-                    (x, z) -> engine.getHeight(x, z, true) + engine.getMinHeight());
-        } catch (Throwable error) {
-            throw NativeStructureGenerationException.failure(
-                    "terrain integration", nativeStructureBatchContext(placementGroups),
-                    chunkPos.x(), chunkPos.z(), error);
-        }
         try {
             NativeStructureVegetationClearer.clearIntersectingVegetation(
                     world, chunk, area, vegetationTargets);
@@ -550,6 +592,15 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
                     "vegetation cleanup", nativeStructureBatchContext(placementGroups),
                     chunkPos.x(), chunkPos.z(), error);
         }
+        try {
+            NativeStructureSurfaceFitter.prepareSurfaceStructures(
+                    world, area, terrainTargets,
+                    (x, z) -> engine.getHeight(x, z, true) + engine.getMinHeight());
+        } catch (Throwable error) {
+            throw NativeStructureGenerationException.failure(
+                    "terrain integration", nativeStructureBatchContext(placementGroups),
+                    chunkPos.x(), chunkPos.z(), error);
+        }
         try {
             NativeStructurePostProcessor.prepareTerrain(
                     world, area, terrainTargets, this::resolvePaletteBlock);
@@ -641,8 +692,8 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
         ChunkPos cp = chunk.getPos();
         int i = cp.getMinBlockX();
         int j = cp.getMinBlockZ();
-        int minY = chunk.getMinY();
-        int maxY = minY + chunk.getHeight() - 1;
+        int minY = chunk.getMinY() + 1;
+        int maxY = chunk.getMinY() + chunk.getHeight() - 1;
         return new BoundingBox(i, minY, j, i + 15, maxY, j + 15);
     }
 
@@ -827,4 +878,8 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     private record NativeLocateCandidate(Holder<Structure> holder, String key) {
     }
+
+    private record IrisNativeLocateSearch(Holder<Structure> holder, String structureId,
+                                          NativeStructureLocatePersistence.Search search) {
+    }
 }

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/core/nms/v26_2_R1/NMSBinding.java

@@ -15,7 +15,9 @@ import art.arcane.iris.engine.data.chunk.TerrainChunk;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.object.IrisDimensionRuntimeContract;
 import art.arcane.iris.engine.platform.PlatformChunkGenerator;
+import art.arcane.iris.nativegen.NativeStructureFactory;
 import art.arcane.iris.nativegen.NativeStructureGenerationException;
+import art.arcane.iris.spi.PlatformStructureHooks.JigsawSourceMetadata;
 import art.arcane.iris.util.project.agent.Agent;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
@@ -102,6 +104,7 @@ import net.minecraft.world.level.levelgen.Heightmap;
 import net.minecraft.world.level.levelgen.WorldgenRandom;
 import net.minecraft.world.level.levelgen.XoroshiroRandomSource;
 import net.minecraft.world.level.levelgen.structure.StructureCheck;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.structures.JigsawStructure;
 import net.minecraft.world.level.levelgen.feature.AbstractHugeMushroomFeature;
@@ -557,6 +560,62 @@ public class NMSBinding implements INMSBinding {
         return keys;
     }
 
+    @Override
+    public JigsawSourceMetadata getJigsawSourceMetadata(String structureKey) {
+        try {
+            Identifier identifier = Identifier.tryParse(structureKey);
+            if (identifier == null) {
+                throw new IllegalArgumentException("Invalid registered structure key: " + structureKey);
+            }
+            Registry<Structure> structures = registry().lookupOrThrow(Registries.STRUCTURE);
+            Structure structure = structures.getValue(identifier);
+            if (structure == null) {
+                throw new IllegalArgumentException("Registered structure does not exist: " + structureKey);
+            }
+            if (!(structure instanceof JigsawStructure jigsaw)) {
+                throw new IllegalArgumentException("Registered structure is not a jigsaw: " + structureKey);
+            }
+            MinecraftServer server = ((CraftServer) Bukkit.getServer()).getHandle().getServer();
+            return NativeStructureFactory.sourceMetadata(
+                    registry(), server.getStructureManager(), jigsaw);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve live jigsaw metadata for registered structure '"
+                    + structureKey + "'", error);
+        }
+    }
+
+    @Override
+    public int getTemplatePoolHorizontalSpan(String templatePoolKey) {
+        try {
+            MinecraftServer server = ((CraftServer) Bukkit.getServer()).getHandle().getServer();
+            return NativeStructureFactory.templatePoolHorizontalSpan(
+                    registry(), server.getStructureManager(), templatePoolKey);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve the live horizontal span for registered "
+                    + "template pool '" + templatePoolKey + "'", error);
+        }
+    }
+
+    @Override
+    public int getJigsawStartPoolHorizontalSpan(String structureKey, String templatePoolKey) {
+        try {
+            Identifier identifier = Identifier.tryParse(structureKey);
+            if (identifier == null) {
+                throw new IllegalArgumentException("Invalid registered structure key: " + structureKey);
+            }
+            Structure structure = registry().lookupOrThrow(Registries.STRUCTURE).getValue(identifier);
+            if (!(structure instanceof JigsawStructure jigsaw)) {
+                throw new IllegalArgumentException("Registered structure is not a jigsaw: " + structureKey);
+            }
+            MinecraftServer server = ((CraftServer) Bukkit.getServer()).getHandle().getServer();
+            return NativeStructureFactory.jigsawStartPoolHorizontalSpan(
+                    registry(), server.getStructureManager(), jigsaw, templatePoolKey);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve the effective start-pool span for registered "
+                    + "jigsaw structure '" + structureKey + "' and pool '" + templatePoolKey + "'", error);
+        }
+    }
+
     @Override
     public KList<String> getStructureSetKeys() {
         KList<String> keys = new KList<>();
@@ -700,7 +759,7 @@ public class NMSBinding implements INMSBinding {
                 return null;
             }
 
-            net.minecraft.world.level.levelgen.structure.BoundingBox box = start.getBoundingBox();
+            BoundingBox box = start.getBoundingBox();
             int spanX = box.maxX() - box.minX() + 1;
             int spanY = box.maxY() - box.minY() + 1;
             int spanZ = box.maxZ() - box.minZ() + 1;
@@ -717,7 +776,7 @@ public class NMSBinding implements INMSBinding {
                 for (int cz = minCZ; cz <= maxCZ; cz++) {
                     level.getChunk(cx, cz);
                     net.minecraft.world.level.ChunkPos cp = new net.minecraft.world.level.ChunkPos(cx, cz);
-                    net.minecraft.world.level.levelgen.structure.BoundingBox chunkBox = new net.minecraft.world.level.levelgen.structure.BoundingBox(
+                    BoundingBox chunkBox = new BoundingBox(
                             cp.getMinBlockX(), box.minY(), cp.getMinBlockZ(),
                             cp.getMaxBlockX(), box.maxY(), cp.getMaxBlockZ());
                     start.placeInChunk(level, structureManager, generator, random, chunkBox, cp);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/core/nms/v26_2_R1/IrisChunkGeneratorFailureContractTest.java

@@ -49,9 +49,9 @@ public class IrisChunkGeneratorFailureContractTest {
         assertTrue(placement.contains("because structure generation is disabled outside the pack"));
         assertTrue(placement.contains("prepareSurfaceStructures"));
         assertTrue(placement.contains("clearIntersectingVegetation"));
-        assertTrue(placement.indexOf("prepareSurfaceStructures")
-                < placement.indexOf("clearIntersectingVegetation"));
         assertTrue(placement.indexOf("clearIntersectingVegetation")
+                < placement.indexOf("prepareSurfaceStructures"));
+        assertTrue(placement.indexOf("prepareSurfaceStructures")
                 < placement.indexOf("for (NativePlacementGroup group"));
         assertFalse(placement.contains("IrisLogging.reportError"));
     }
@@ -66,6 +66,20 @@ public class IrisChunkGeneratorFailureContractTest {
         assertTrue(source.contains("catch (GenerationSessionException e)"));
     }
 
+    @Test
+    public void structureReferenceRepairIsGenerationLeased() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.nmsChunkGeneratorSource")));
+        int referencesStart = source.indexOf("public void createReferences");
+        int referencesEnd = source.indexOf("public CompletableFuture<ChunkAccess> createBiomes", referencesStart);
+        String references = source.substring(referencesStart, referencesEnd);
+
+        assertTrue(references.contains("requireGenerationLease(\"bukkit_nms_create_references\")"));
+        assertTrue(references.contains("IrisContext.open(engine, lease.sessionId(), null)"));
+        assertTrue(references.contains("NativeStructureReferenceRepair.createReferences("));
+        assertFalse(references.contains("delegate.createReferences("));
+        assertFalse(references.contains("catch ("));
+    }
+
     @Test
     public void terrainWritesPrimeTheWorldgenHeightmapsForEveryChunk() throws IOException {
         String source = Files.readString(Path.of(System.getProperty("iris.nmsChunkGeneratorSource")));
@@ -89,6 +103,7 @@ public class IrisChunkGeneratorFailureContractTest {
         assertTrue(placement.indexOf("WorldgenTerrainHeightmaps.primeStructurePlacement(")
                 < placement.indexOf("prepareSurfaceStructures"));
         assertTrue(source.contains("engine.acquireGenerationLease(\"bukkit_nms_worldgen_heightmaps\")"));
+        assertTrue(source.contains("int minY = chunk.getMinY() + 1;"));
     }
 
     @Test
@@ -112,6 +127,38 @@ public class IrisChunkGeneratorFailureContractTest {
         assertTrue(source.contains("import art.arcane.iris.nativegen.WorldgenTerrainHeightmaps;"));
     }
 
+    @Test
+    public void onlySidecarOwnedInjectedStartsUsePersistedPlacementPolicy() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.nmsChunkGeneratorSource")));
+        int placementStart = source.indexOf("private void placeVanillaStructures");
+        int placementEnd = source.indexOf("private static String nativeStructureBatchContext", placementStart);
+        String placement = source.substring(placementStart, placementEnd);
+        int ownershipResolution = placement.indexOf(
+                "NativeStructureOwnershipRecovery.resolve(");
+        int persistedDecision = placement.indexOf("ownership.restoredDecision()", ownershipResolution);
+        int adjustmentStart = source.indexOf("private void adjustGeneratedStructures");
+        int adjustmentEnd = source.indexOf("public ChunkGeneratorStructureState createState", adjustmentStart);
+        String adjustment = source.substring(adjustmentStart, adjustmentEnd);
+        Path nativegen = Path.of(System.getProperty("iris.nativeStructurePostProcessorSource")).getParent();
+        String factory = Files.readString(nativegen.resolve("NativeStructureFactory.java"));
+        String injector = Files.readString(nativegen.resolve("NativeStructureStartInjector.java"));
+        String recovery = Files.readString(nativegen.resolve("NativeStructureOwnershipRecovery.java"));
+        int ownershipRecord = injector.indexOf("NativeStructureOwnershipStore.record(");
+        int startPublication = injector.indexOf(
+                "context.structureManager().setStartForStructure(", ownershipRecord);
+
+        assertTrue(ownershipResolution >= 0);
+        assertTrue(persistedDecision > ownershipResolution);
+        assertTrue(recovery.contains("NativeStructureOwnershipStore.findPersisted("));
+        assertTrue(recovery.contains("NativeStructureOwnershipStore.record("));
+        assertTrue(ownershipRecord >= 0);
+        assertTrue(startPublication > ownershipRecord);
+        assertTrue(factory.contains("NativeStructureReferenceEnvelope.wrapForPublication("));
+        assertTrue(adjustment.contains("NativeStructureReferenceEnvelope.wrapForPublication("));
+        assertFalse(source.contains("wrapManaged("));
+        assertFalse(source.contains("isIrisManagedStart("));
+    }
+
     private static int occurrences(String source, String needle) {
         int count = 0;
         int index = source.indexOf(needle);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/core/nms/v26_2_R1/IrisChunkGeneratorMonumentLocateContractTest.java

@@ -10,7 +10,9 @@ import org.junit.Test;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.concurrent.atomic.AtomicInteger;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertSame;
@@ -27,17 +29,19 @@ public class IrisChunkGeneratorMonumentLocateContractTest {
         assertTrue(filterStart > irisHelperStart);
         String outerMethod = source.substring(findStart, irisHelperStart);
         String irisHelper = source.substring(irisHelperStart, filterStart);
-        int unexploredGuard = irisHelper.indexOf("if (findUnexplored)");
         int registryLookup = irisHelper.indexOf("level.registryAccess().lookupOrThrow(Registries.STRUCTURE)");
         int placedCheck = irisHelper.indexOf(
-                "if (!IrisStructureLocator.isPlaced(engine, structureId))");
-        int irisLocate = irisHelper.indexOf("IrisStructureLocator.locate(", placedCheck);
+                "if (!IrisStructureLocator.hasNativePlacement(engine, structureId))");
+        int irisLocate = irisHelper.indexOf("NativeStructureLocatePersistence.search(", placedCheck);
         int searchLimit = irisHelper.indexOf("LocateStatus.SEARCH_LIMIT_REACHED", irisLocate);
-        int limitSkip = irisHelper.indexOf("continue;", searchLimit);
         int nativeFilter = outerMethod.indexOf("filterReachableStructures(level, holders)");
-        int delegateLocate = outerMethod.indexOf("delegate.findNearestMapStructure(level, reachable");
-        int nearestSelection = outerMethod.indexOf(
-                "NativeStructureLocateResults.nearest(pos, irisPlaced, nativeLocated)");
+        int nativePrediction = outerMethod.indexOf("NativeStructureVanillaLocator.predict(", nativeFilter);
+        int irisResolution = outerMethod.indexOf("return findNearestIrisStructure(", nativePrediction);
+        int nearestSelection = irisHelper.indexOf(
+                "NativeStructureLocateResults.nearest(pos, predicted, nativeLocated)");
+        int selectedVerification = irisHelper.indexOf("bestSearch.search().verify(bestResult)", nearestSelection);
+        int selectedReference = irisHelper.indexOf(
+                "selectedSearch.search().reference(selectedStart)", selectedVerification);
         int reachabilityStart = source.indexOf("private Set<String> reachableStructureKeys", filterStart);
         assertTrue(reachabilityStart > filterStart);
         String filterMethod = source.substring(filterStart, reachabilityStart);
@@ -46,22 +50,28 @@ public class IrisChunkGeneratorMonumentLocateContractTest {
         int emptyNativePartition = filterMethod.indexOf("if (candidates.isEmpty())", filterContinue);
         int reachabilityLookup = filterMethod.indexOf("reachableStructureKeys(level)", emptyNativePartition);
 
-        assertTrue(unexploredGuard >= 0);
-        assertTrue(registryLookup > unexploredGuard);
+        assertTrue(registryLookup >= 0);
         assertTrue(placedCheck > registryLookup);
         assertTrue(irisLocate > placedCheck);
         assertTrue(searchLimit > irisLocate);
-        assertTrue(limitSkip > searchLimit);
         assertTrue(nativeFilter >= 0);
-        assertTrue(delegateLocate > nativeFilter);
-        assertTrue(nearestSelection > delegateLocate);
+        assertTrue(nativePrediction > nativeFilter);
+        assertTrue(irisResolution > nativePrediction);
+        assertTrue(nearestSelection > irisLocate);
+        assertTrue(selectedVerification > nearestSelection);
+        assertTrue(selectedReference > selectedVerification);
         assertTrue(policyFilter >= 0);
         assertTrue(filterContinue > policyFilter);
         assertTrue(emptyNativePartition > filterContinue);
         assertTrue(reachabilityLookup > emptyNativePartition);
         assertFalse(filterMethod.contains("NativeStructureLocateCapability"));
         assertFalse(irisHelper.contains("NativeStructureLocateCapability.isPaperUnavailable(structureId)"));
-        assertTrue(irisHelper.contains("new BlockPos(result.originX(), result.baseY(), result.originZ())"));
+        assertTrue(irisHelper.contains("NativeStructureLocatePersistence.probe("));
+        assertTrue(irisHelper.contains("NativeStructureLocateResults.selectAndReference("));
+        assertTrue(irisHelper.contains("selectedSearch.search().reference(selectedStart)"));
+        assertTrue(irisHelper.contains("findUnexplored"));
+        assertTrue(irisHelper.contains("verified.ownership().locatorY()"));
+        assertFalse(outerMethod.contains("delegate.findNearestMapStructure("));
     }
 
     @Test
@@ -77,6 +87,50 @@ public class IrisChunkGeneratorMonumentLocateContractTest {
         assertSame(nativeTie, NativeStructureLocateResults.nearest(origin, irisNear, nativeTie));
     }
 
+    @Test
+    public void mixedUnexploredLocateReferencesOnlyTheSelectedProvider() {
+        BlockPos origin = BlockPos.ZERO;
+        Pair<BlockPos, Holder<Structure>> irisNear = Pair.of(new BlockPos(4, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeFar = Pair.of(new BlockPos(8, 70, 0), null);
+        AtomicInteger irisReferences = new AtomicInteger();
+        AtomicInteger nativeReferences = new AtomicInteger();
+
+        Pair<BlockPos, Holder<Structure>> irisSelected =
+                NativeStructureLocateResults.selectAndReference(
+                        origin,
+                        irisNear, () -> irisReferences.incrementAndGet(),
+                        nativeFar, () -> nativeReferences.incrementAndGet());
+
+        assertSame(irisNear, irisSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(0, nativeReferences.get());
+
+        Pair<BlockPos, Holder<Structure>> nativeNear = Pair.of(new BlockPos(2, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeSelected =
+                NativeStructureLocateResults.selectAndReference(
+                        origin,
+                        irisNear, () -> irisReferences.incrementAndGet(),
+                        nativeNear, () -> nativeReferences.incrementAndGet());
+
+        assertSame(nativeNear, nativeSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(1, nativeReferences.get());
+    }
+
+    @Test
+    public void nativePredictionIsReadOnlyUntilTheWinnerIsCommitted() throws IOException {
+        Path nativegen = Path.of(System.getProperty("iris.nativeStructurePostProcessorSource")).getParent();
+        String source = Files.readString(nativegen.resolve("NativeStructureVanillaLocator.java"));
+        int predictionStart = source.indexOf("private static Candidate predictAt(");
+        int candidateStart = source.indexOf("public static final class Candidate", predictionStart);
+        String prediction = source.substring(predictionStart, candidateStart);
+        String candidate = source.substring(candidateStart);
+
+        assertFalse(prediction.contains("addReference("));
+        assertTrue(candidate.contains("structureManager.addReference(referenceStart)"));
+        assertTrue(candidate.contains("committed.compareAndSet(false, true)"));
+    }
+
     @Test
     public void stiltSupportUsesPlacedSolidOccupancyWithoutSnapshotDifferenceRequirement() throws IOException {
         Path processor = Path.of(System.getProperty("iris.nativeStructurePostProcessorSource"));

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureFactoryTest.java

@@ -1,11 +1,23 @@
 package art.arcane.iris.nativegen;
 
 import art.arcane.iris.engine.object.IrisJigsawConfiguration;
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import com.mojang.datafixers.util.Either;
+import com.mojang.datafixers.util.Pair;
 import com.mojang.serialization.MapCodec;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Holder;
+import net.minecraft.core.HolderOwner;
 import net.minecraft.core.HolderSet;
+import net.minecraft.core.Vec3i;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.server.Bootstrap;
 import net.minecraft.server.level.WorldGenRegion;
 import net.minecraft.util.RandomSource;
@@ -13,10 +25,12 @@ import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.LevelHeightAccessor;
 import net.minecraft.world.level.NoiseColumn;
 import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
 import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.biome.BiomeManager;
 import net.minecraft.world.level.biome.FixedBiomeSource;
 import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkGenerator;
@@ -25,19 +39,40 @@ import net.minecraft.world.level.levelgen.RandomState;
 import net.minecraft.world.level.levelgen.blending.Blender;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
 import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.EmptyPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElementType;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.pools.alias.PoolAliasBinding;
 import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
 import net.minecraft.world.level.levelgen.structure.structures.SwampHutStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
 
 public class NativeStructureFactoryTest {
     @BeforeClass
@@ -67,20 +102,142 @@ public class NativeStructureFactoryTest {
     }
 
     @Test
-    public void forcedGeneratorSuppliesDeterministicPermissiveEnvironment() {
+    public void sourceMetadataReadsScalarAndAxisSpecificJigsawRanges() {
+        CompoundTag scalar = new CompoundTag();
+        scalar.putInt("max_distance_from_center", 80);
+        CompoundTag axisSpecific = new CompoundTag();
+        CompoundTag distance = new CompoundTag();
+        distance.putInt("horizontal", 96);
+        distance.putInt("vertical", 64);
+        axisSpecific.put("max_distance_from_center", distance);
+
+        assertEquals(80, NativeStructureFactory.sourceDistance(scalar, "horizontal"));
+        assertEquals(80, NativeStructureFactory.sourceDistance(scalar, "vertical"));
+        assertEquals(96, NativeStructureFactory.sourceDistance(axisSpecific, "horizontal"));
+        assertEquals(64, NativeStructureFactory.sourceDistance(axisSpecific, "vertical"));
+    }
+
+    @Test
+    public void sourceMetadataIncludesAdjustBoundingBoxExpansion() {
+        Structure none = new SwampHutStructure(new Structure.StructureSettings(HolderSet.empty()));
+        Structure beardBox = new SwampHutStructure(new Structure.StructureSettings.Builder(HolderSet.empty())
+                .terrainAdapation(TerrainAdjustment.BEARD_BOX)
+                .build());
+
+        assertEquals(0, NativeStructureFactory.horizontalReferenceExpansion(none));
+        assertEquals(12, NativeStructureFactory.horizontalReferenceExpansion(beardBox));
+    }
+
+    @Test
+    public void templatePoolSpanIncludesWeightedListsFallbacksAndRotations() {
+        StructurePoolElement narrow = inlineElement(30, 8, 70);
+        StructurePoolElement wide = inlineElement(96, 8, 12);
+        ListPoolElement list = new ListPoolElement(
+                List.of(narrow, wide, EmptyPoolElement.INSTANCE),
+                StructureTemplatePool.Projection.RIGID);
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(
+                fallbackHolder,
+                List.of(Pair.of(inlineElement(110, 8, 20), 1)));
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                fallbackHolder,
+                List.of(Pair.of(list, 5), Pair.of(EmptyPoolElement.INSTANCE, 1)));
+        startHolder.bind(start);
+
+        assertEquals(110, NativeStructureTemplatePoolBounds.horizontalSpan(start, null));
+    }
+
+    @Test
+    public void oversizedInlineStartTemplateReportsItsFullSpan() {
+        BoundPoolHolder holder = new BoundPoolHolder("test:oversized");
+        StructureTemplatePool pool = new StructureTemplatePool(
+                holder,
+                List.of(Pair.of(inlineElement(160, 8, 9), 1)));
+        holder.bind(pool);
+
+        assertEquals(160, NativeStructureTemplatePoolBounds.horizontalSpan(pool, null));
+    }
+
+    @Test
+    public void sourceSpanIncludesOnlyAliasesThatCanReplaceTheStartPool() {
+        BoundPoolHolder emptyHolder = new BoundPoolHolder("test:empty");
+        StructureTemplatePool empty = new StructureTemplatePool(emptyHolder, List.of());
+        emptyHolder.bind(empty);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(20, 8, 12), 1)));
+        startHolder.bind(start);
+        BoundPoolHolder replacementHolder = new BoundPoolHolder("test:replacement");
+        StructureTemplatePool replacement = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(30, 8, 12), 1)));
+        replacementHolder.bind(replacement);
+        BoundPoolHolder unrelatedHolder = new BoundPoolHolder("test:unrelated");
+        StructureTemplatePool unrelated = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(200, 8, 12), 1)));
+        unrelatedHolder.bind(unrelated);
+        ResourceKey<StructureTemplatePool> startKey = startHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> replacementKey = replacementHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> unrelatedKey = unrelatedHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> childAlias = ResourceKey.create(
+                Registries.TEMPLATE_POOL, Identifier.parse("test:child_alias"));
+        List<PoolAliasBinding> aliases = List.of(
+                PoolAliasBinding.direct(startKey, replacementKey),
+                PoolAliasBinding.direct(childAlias, unrelatedKey));
+        Map<ResourceKey<StructureTemplatePool>, StructureTemplatePool> pools = Map.of(
+                replacementKey, replacement,
+                unrelatedKey, unrelated);
+
+        assertEquals(30, NativeStructureTemplatePoolBounds.sourceHorizontalSpan(
+                null, start, startKey, aliases, pools::get));
+    }
+
+    @Test
+    public void sourceStartSpanDoesNotIncludeItsFallbackPool() {
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:large_fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(inlineElement(180, 8, 10), 1)));
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:small_start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(inlineElement(24, 8, 10), 1)));
+        startHolder.bind(start);
+
+        assertEquals(180, NativeStructureTemplatePoolBounds.horizontalSpan(start, null));
+        assertEquals(24, NativeStructureTemplatePoolBounds.sourceHorizontalSpan(
+                null, start, startHolder.unwrapKey().orElseThrow(), List.of(), ignored -> null));
+    }
+
+    @Test
+    public void customPoolElementUsesItsBoundingBoxCapability() {
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:custom_fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(fallbackHolder, List.of());
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder poolHolder = new BoundPoolHolder("test:custom");
+        StructureTemplatePool pool = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(new BoundingPoolElement(37, 11), 1)));
+        poolHolder.bind(pool);
+
+        assertEquals(37, NativeStructureTemplatePoolBounds.horizontalSpan(pool, null));
+    }
+
+    @Test
+    public void forcedGeneratorBypassesBiomeEligibilityWithoutFabricatingTerrain() {
         ChunkGenerator delegate = new TestChunkGenerator();
         Holder<Biome> biome = Holder.direct((Biome) null);
         LevelHeightAccessor heightAccessor = LevelHeightAccessor.create(-64, 384);
         ForcedStructureChunkGenerator generator = new ForcedStructureChunkGenerator(
-                delegate, biome, -20);
+                delegate, biome);
 
-        assertEquals(-63, generator.getSeaLevel());
-        assertEquals(81, generator.getBaseHeight(
+        assertEquals(63, generator.getSeaLevel());
+        assertEquals(64, generator.getBaseHeight(
                 0, 0, Heightmap.Types.WORLD_SURFACE_WG, heightAccessor, null));
         NoiseColumn column = generator.getBaseColumn(
                 0, 0, heightAccessor, null);
         assertSame(Blocks.STONE, column.getBlock(80).getBlock());
-        assertSame(Blocks.AIR, column.getBlock(81).getBlock());
+        assertSame(Blocks.STONE, column.getBlock(81).getBlock());
+        assertNotSame(delegate.getBiomeSource(), generator.getBiomeSource());
     }
 
     @Test
@@ -103,6 +260,96 @@ public class NativeStructureFactoryTest {
         assertEquals(-20, relocated.getBoundingBox().minY());
     }
 
+    @Test
+    public void invalidGeneratedStartIsANormalSkippedCandidate() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        StructureStart valid = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(
+                        new SwampHutPiece(RandomSource.create(23L), 0, 0)))
+        );
+
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(
+                StructureStart.INVALID_START));
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(null));
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(
+                new StructureStart(source, new ChunkPos(0, 0), 0,
+                        new PiecesContainer(List.of()))));
+        assertTrue(NativeStructureStartInjector.isUsableGeneratedStart(valid));
+    }
+
+    @Test
+    public void unrepresentableGeneratedContentBecomesAnUnpublishedInvalidStart() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        SwampHutPiece boundaryPiece = new SwampHutPiece(RandomSource.create(29L), 0, 0);
+        boundaryPiece.move(143 - boundaryPiece.getBoundingBox().maxX(), 0, 0);
+        StructureStart boundary = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(boundaryPiece))
+        );
+        SwampHutPiece oversizedPiece = new SwampHutPiece(RandomSource.create(31L), 0, 0);
+        oversizedPiece.move(144 - oversizedPiece.getBoundingBox().maxX(), 0, 0);
+        StructureStart oversized = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(oversizedPiece))
+        );
+
+        StructureStart boundaryResult = NativeStructureReferenceEnvelope.wrapForPublication(
+                boundary, source, 0, new IrisStructureTerrain(), "test:boundary_content");
+
+        StructureStart result = NativeStructureReferenceEnvelope.wrapForPublication(
+                oversized, source, 0,
+                new IrisStructureTerrain(),
+                "test:oversized_content");
+
+        assertTrue(boundaryResult.isValid());
+        assertSame(StructureStart.INVALID_START, result);
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(result));
+        assertEquals(1, oversized.getPieces().size());
+    }
+
+    @Test
+    public void failedManualGenerationClearsStaleOwnershipAfterReplacementHandling() throws Exception {
+        String source = Files.readString(
+                Path.of(System.getProperty("iris.nativeStructureStartInjectorSource")),
+                StandardCharsets.UTF_8);
+        int failureStart = source.indexOf("if (!isUsableGeneratedStart(generated))");
+        int failureEnd = source.indexOf("continue;", failureStart);
+        String failureBranch = source.substring(failureStart, failureEnd);
+
+        assertTrue(failureBranch.contains("if (replacement)"));
+        assertTrue(failureBranch.indexOf("NativeStructureOwnershipStore.discard(")
+                > failureBranch.lastIndexOf("}") );
+        assertTrue(failureStart < source.indexOf("NativeStructureOwnershipFingerprint.capture("));
+        assertTrue(failureStart < source.indexOf("NativeStructureOwnershipStore.record("));
+    }
+
+    @Test
+    public void failedManualStartPublicationClearsRecordedOwnershipAndPreservesTheFailure() throws Exception {
+        String source = Files.readString(
+                Path.of(System.getProperty("iris.nativeStructureStartInjectorSource")),
+                StandardCharsets.UTF_8);
+        int ownershipRecord = source.indexOf("NativeStructureOwnershipStore.record(");
+        int publication = source.indexOf("context.structureManager().setStartForStructure(", ownershipRecord);
+        int cleanup = source.indexOf("NativeStructureOwnershipStore.discard(", publication);
+        int suppressed = source.indexOf("publicationError.addSuppressed(cleanupError)", cleanup);
+        int rethrow = source.indexOf("throw publicationError;", suppressed);
+
+        assertTrue(ownershipRecord >= 0);
+        assertTrue(publication > ownershipRecord);
+        assertTrue(cleanup > publication);
+        assertTrue(suppressed > cleanup);
+        assertTrue(rethrow > suppressed);
+    }
+
     private static final class TestChunkGenerator extends ChunkGenerator {
         private TestChunkGenerator() {
             super(new FixedBiomeSource(Holder.direct((Biome) null)));
@@ -171,4 +418,91 @@ public class NativeStructureFactoryTest {
                                        BlockPos feetPos) {
         }
     }
+
+    private static StructurePoolElement inlineElement(int sizeX, int sizeY, int sizeZ) {
+        StructureTemplate template = new StructureTemplate();
+        CompoundTag tag = new CompoundTag();
+        ListTag size = new ListTag();
+        size.add(IntTag.valueOf(sizeX));
+        size.add(IntTag.valueOf(sizeY));
+        size.add(IntTag.valueOf(sizeZ));
+        tag.put("size", size);
+        template.load(BuiltInRegistries.BLOCK, tag);
+        return new InlinePoolElement(template);
+    }
+
+    private static final class InlinePoolElement extends SinglePoolElement {
+        private final StructureTemplate inlineTemplate;
+
+        private InlinePoolElement(StructureTemplate template) {
+            super(Either.right(template), Holder.direct(new StructureProcessorList(List.of())),
+                    StructureTemplatePool.Projection.RIGID, Optional.<LiquidSettings>empty());
+            inlineTemplate = template;
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return inlineTemplate.getBoundingBox(
+                    new StructurePlaceSettings().setRotation(rotation), position);
+        }
+    }
+
+    private static final class BoundingPoolElement extends StructurePoolElement {
+        private final int width;
+        private final int depth;
+
+        private BoundingPoolElement(int width, int depth) {
+            super(StructureTemplatePool.Projection.RIGID);
+            this.width = width;
+            this.depth = depth;
+        }
+
+        @Override
+        public Vec3i getSize(StructureTemplateManager templateManager, Rotation rotation) {
+            return new Vec3i(width, 1, depth);
+        }
+
+        @Override
+        public List<StructureTemplate.JigsawBlockInfo> getShuffledJigsawBlocks(
+                StructureTemplateManager templateManager, BlockPos position,
+                Rotation rotation, RandomSource random) {
+            return List.of();
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return new BoundingBox(
+                    position.getX(), position.getY(), position.getZ(),
+                    position.getX() + width - 1, position.getY(),
+                    position.getZ() + depth - 1);
+        }
+
+        @Override
+        public boolean place(StructureTemplateManager templateManager,
+                             WorldGenLevel world,
+                             StructureManager structureManager, ChunkGenerator chunkGenerator,
+                             BlockPos position, BlockPos pivot, Rotation rotation,
+                             BoundingBox area, RandomSource random,
+                             LiquidSettings liquidSettings, boolean keepJigsaws) {
+            return true;
+        }
+
+        @Override
+        public StructurePoolElementType<?> getType() {
+            return StructurePoolElementType.EMPTY;
+        }
+    }
+
+    private static final class BoundPoolHolder extends Holder.Reference<StructureTemplatePool> {
+        private BoundPoolHolder(String key) {
+            super(Type.STAND_ALONE, new HolderOwner<>() {
+            }, ResourceKey.create(Registries.TEMPLATE_POOL, Identifier.parse(key)), null);
+        }
+
+        private void bind(StructureTemplatePool pool) {
+            bindValue(pool);
+        }
+    }
 }

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureLocatePersistenceTest.java

@@ -0,0 +1,197 @@
+package art.arcane.iris.nativegen;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureLocatePersistenceTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void storageProbeScansEachCandidateOnlyOnce() {
+        AtomicInteger reads = new AtomicInteger();
+        CompoundTag chunk = new CompoundTag();
+        chunk.putInt("DataVersion", SharedConstants.getCurrentVersion().dataVersion().version());
+        chunk.putString("Status", "full");
+        CompoundTag start = new CompoundTag();
+        start.putString("id", "minecraft:village_plains");
+        start.putInt("references", 0);
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", start);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            reads.incrementAndGet();
+                            chunk.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        });
+        ChunkPos chunkPos = new ChunkPos(7, -11);
+
+        assertTrue(budget.acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+        assertTrue(budget.acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+        assertEquals(1, reads.get());
+        assertEquals(1, budget.used());
+    }
+
+    @Test
+    public void legacyStoredChunkIsDatafixedBeforeItsStartIsClassified() {
+        AtomicBoolean datafixed = new AtomicBoolean();
+        CompoundTag legacy = new CompoundTag();
+        legacy.putInt("DataVersion", 100);
+        legacy.putString("Status", "full");
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            legacy.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        },
+                        (level, storedChunk) -> {
+                            datafixed.set(true);
+                            CompoundTag fixed = storedChunk.copy();
+                            fixed.putInt("DataVersion",
+                                    SharedConstants.getCurrentVersion().dataVersion().version());
+                            CompoundTag start = new CompoundTag();
+                            start.putString("id", "minecraft:village_plains");
+                            start.putInt("references", 1);
+                            CompoundTag starts = new CompoundTag();
+                            starts.put("minecraft:village_plains", start);
+                            CompoundTag structures = new CompoundTag();
+                            structures.put("starts", starts);
+                            fixed.put("structures", structures);
+                            return fixed;
+                        });
+
+        assertFalse(budget.acceptsStored(
+                null, new ChunkPos(3, 4), "minecraft:village_plains", true));
+        assertTrue(datafixed.get());
+    }
+
+    @Test
+    public void partialDatafixFailureFallsBackToSelectedChunkVerification() {
+        CompoundTag legacy = new CompoundTag();
+        legacy.putInt("DataVersion", 100);
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            legacy.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        },
+                        (level, storedChunk) -> {
+                            throw new IllegalStateException("broken partial datafix");
+                        });
+
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(9, -2), "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void missingStartsContainerFallsBackToSelectedChunkVerification() {
+        CompoundTag chunk = currentChunk();
+        NativeStructureLocatePersistence.ProbeBudget budget = budget(chunk);
+
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(5, 8), "minecraft:village_plains", false));
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(5, 8), "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void presentEmptyStartsContainerRejectsTheCandidateWithoutLoading() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", new CompoundTag());
+        chunk.put("structures", structures);
+        NativeStructureLocatePersistence.ProbeBudget budget = budget(chunk);
+
+        assertFalse(budget.acceptsStored(
+                null, new ChunkPos(-3, 2), "minecraft:village_plains", false));
+    }
+
+    @Test
+    public void collisionTombstoneIsRejectedForNormalAndUnexploredLocate() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag tombstone = new CompoundTag();
+        tombstone.putString("id", "INVALID");
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", tombstone);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        ChunkPos chunkPos = new ChunkPos(12, -9);
+
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", false));
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void malformedNonCompoundStartIsRejectedWithoutLoading() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag starts = new CompoundTag();
+        starts.putInt("minecraft:village_plains", 1);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+
+        assertFalse(budget(chunk).acceptsStored(
+                null, new ChunkPos(1, 1), "minecraft:village_plains", false));
+    }
+
+    @Test
+    public void referencedStoredStartIsOnlyRejectedForUnexploredLocate() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag start = new CompoundTag();
+        start.putString("id", "minecraft:village_plains");
+        start.putInt("references", 1);
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", start);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        ChunkPos chunkPos = new ChunkPos(-4, -7);
+
+        assertTrue(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", false));
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+    }
+
+    private static CompoundTag currentChunk() {
+        CompoundTag chunk = new CompoundTag();
+        chunk.putInt("DataVersion", SharedConstants.getCurrentVersion().dataVersion().version());
+        return chunk;
+    }
+
+    private static NativeStructureLocatePersistence.ProbeBudget budget(CompoundTag chunk) {
+        return new NativeStructureLocatePersistence.ProbeBudget(
+                512,
+                (chunkPos, visitor) -> {
+                    chunk.acceptAsRoot(visitor);
+                    return CompletableFuture.completedFuture(null);
+                });
+    }
+}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipFingerprintTest.java

@@ -0,0 +1,346 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.object.IrisNativeStructure;
+import art.arcane.iris.engine.object.IrisStructurePlacement;
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import art.arcane.iris.engine.object.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.collection.KList;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.Vec3i;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElementType;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureOwnershipFingerprintTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void monumentFingerprintSurvivesSourceYRegenerationWithoutSyntheticPieces() {
+        long seed = 8372619L;
+        ChunkPos origin = new ChunkPos(9, -4);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        int alignedLocatorY = NativeStructureOwnershipFingerprint.locatorY(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                structure,
+                0,
+                terrain);
+        String beforeReload = NativeStructureOwnershipFingerprint.fingerprint(
+                "minecraft:monument", wrapped);
+
+        ListTag serializedPieces = (ListTag) new PiecesContainer(wrapped.getPieces()).save(null);
+        PiecesContainer loadedPieces = PiecesContainer.load(serializedPieces, null);
+        assertEquals(1, loadedPieces.pieces().size());
+        assertTrue(loadedPieces.pieces().getFirst()
+                instanceof OceanMonumentPieces.MonumentBuilding);
+        PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                origin, seed, loadedPieces);
+        StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
+        String afterReload = NativeStructureOwnershipFingerprint.fingerprint(
+                "minecraft:monument", reloaded);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                "minecraft:monument",
+                wrapped,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()),
+                NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain));
+
+        assertEquals(beforeReload, afterReload);
+        assertTrue(NativeStructureOwnershipFingerprint.matches(ownership, reloaded));
+        assertNotEquals(alignedLocatorY, NativeStructureOwnershipFingerprint.locatorY(reloaded));
+        assertEquals(alignedLocatorY, ownership.locatorY());
+        assertEquals(1, reloaded.getPieces().size());
+        assertEquals(1, wrapped.getPieces().size());
+    }
+
+    @Test
+    public void sameKeyAndOriginStillRequiresMatchingContentIdentity() {
+        long seed = 18273L;
+        ChunkPos origin = new ChunkPos(2, 3);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart expected = monumentStart(structure, origin, seed);
+        StructureStart moved = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : moved.getPieces()) {
+            piece.move(1, 0, 0);
+        }
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                "minecraft:monument",
+                expected,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(expected).minY()),
+                expected.getBoundingBox());
+
+        assertFalse(NativeStructureOwnershipFingerprint.matches(ownership, moved));
+    }
+
+    @Test
+    public void persistedEnvelopeRepairsReloadedMonumentReferenceOutsideLiveBounds() {
+        long seed = 772931L;
+        ChunkPos origin = new ChunkPos(4, -7);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                structure,
+                0,
+                terrain);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                "minecraft:monument",
+                wrapped,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()),
+                NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain));
+        PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                origin, seed, new PiecesContainer(wrapped.getPieces()));
+        StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
+        ChunkPos target = outsideLiveBounds(ownership, reloaded);
+
+        assertNotNull(target);
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, ownership));
+        assertFalse(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, null));
+    }
+
+    @Test
+    public void overlappingManualStartsSixteenChunksApartRemainIndependentlyReferenced() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos westOrigin = new ChunkPos(0, 0);
+        ChunkPos eastOrigin = new ChunkPos(16, 0);
+        StructureStart west = monumentStart(structure, westOrigin, 317L);
+        StructureStart east = monumentStart(structure, eastOrigin, 941L);
+        west.getPieces().getFirst().move(112, 0, 0);
+        east.getPieces().getFirst().move(-96, 0, 0);
+        NativeStructureOwnershipRecord westOwnership = ownership(westOrigin, west, structure);
+        NativeStructureOwnershipRecord eastOwnership = ownership(eastOrigin, east, structure);
+        ChunkPos shared = new ChunkPos(8, 0);
+
+        assertTrue(NativeStructureReferenceEnvelope.contentBounds(west).intersects(
+                NativeStructureReferenceEnvelope.contentBounds(east)));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", west, westOwnership));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", east, eastOwnership));
+    }
+
+    @Test
+    public void denseAdjacentManualStartsDoNotSuppressEachOther() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos firstOrigin = new ChunkPos(0, 0);
+        ChunkPos secondOrigin = new ChunkPos(1, 0);
+        StructureStart first = monumentStart(structure, firstOrigin, 17L);
+        StructureStart second = monumentStart(structure, secondOrigin, 23L);
+        NativeStructureOwnershipRecord firstOwnership = ownership(firstOrigin, first, structure);
+        NativeStructureOwnershipRecord secondOwnership = ownership(secondOrigin, second, structure);
+        ChunkPos shared = new ChunkPos(0, 0);
+
+        assertTrue(NativeStructureReferenceEnvelope.contentBounds(first).intersects(
+                NativeStructureReferenceEnvelope.contentBounds(second)));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", first, firstOwnership));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", second, secondOwnership));
+    }
+
+    @Test
+    public void customPoolElementIdentityDoesNotDependOnProcessLocalToString() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos origin = new ChunkPos(3, -2);
+        StructureStart first = poolStart(structure, origin, new IdentityStringPoolElement());
+        StructureStart reloaded = poolStart(structure, origin, new IdentityStringPoolElement());
+
+        assertEquals(
+                NativeStructureOwnershipFingerprint.fingerprint("test:custom_pool", first),
+                NativeStructureOwnershipFingerprint.fingerprint("test:custom_pool", reloaded));
+    }
+
+    @Test
+    public void namedPoolTemplateRemainsPartOfTheStableFingerprint() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos origin = new ChunkPos(3, -2);
+        StructurePoolElement firstElement = StructurePoolElement.single("test:first")
+                .apply(StructureTemplatePool.Projection.RIGID);
+        StructurePoolElement secondElement = StructurePoolElement.single("test:second")
+                .apply(StructureTemplatePool.Projection.RIGID);
+
+        assertNotEquals(
+                NativeStructureOwnershipFingerprint.fingerprint(
+                        "test:named_pool", poolStart(structure, origin, firstElement)),
+                NativeStructureOwnershipFingerprint.fingerprint(
+                        "test:named_pool", poolStart(structure, origin, secondElement)));
+    }
+
+    private static StructureStart monumentStart(OceanMonumentStructure structure,
+                                                  ChunkPos origin, long seed) {
+        WorldgenRandom random = new WorldgenRandom(
+                new LegacyRandomSource(RandomSupport.generateUniqueSeed()));
+        random.setLargeFeatureSeed(seed, origin.x(), origin.z());
+        Direction orientation = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+        OceanMonumentPieces.MonumentBuilding building = new OceanMonumentPieces.MonumentBuilding(
+                random,
+                origin.getMinBlockX() - 29,
+                origin.getMinBlockZ() - 29,
+                orientation
+        );
+        return new StructureStart(
+                structure,
+                origin,
+                0,
+                new PiecesContainer(List.of(building))
+        );
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin, int baseY) {
+        IrisNativeStructure source = new IrisNativeStructure()
+                .setStructure("minecraft:monument")
+                .setWeight(1);
+        IrisStructurePlacement placement = new IrisStructurePlacement()
+                .setPlacementId("monument-test")
+                .setNativeStructures(new KList<IrisNativeStructure>().qadd(source));
+        return new NativeStructureStartPlan(
+                placement,
+                source,
+                origin.x(),
+                origin.z(),
+                baseY
+        );
+    }
+
+    private static NativeStructureOwnershipRecord ownership(
+            ChunkPos origin, StructureStart start, OceanMonumentStructure structure) {
+        return NativeStructureOwnershipFingerprint.capture(
+                "minecraft:monument",
+                start,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(start).minY()),
+                NativeStructureReferenceEnvelope.referenceBounds(
+                        start, structure, new IrisStructureTerrain())
+        );
+    }
+
+    private static StructureStart poolStart(
+            OceanMonumentStructure structure, ChunkPos origin, StructurePoolElement element) {
+        BlockPos position = new BlockPos(
+                origin.getMiddleBlockX(), 64, origin.getMiddleBlockZ());
+        PoolElementStructurePiece piece = new PoolElementStructurePiece(
+                null, element, position, 0, Rotation.NONE,
+                new BoundingBox(position), LiquidSettings.APPLY_WATERLOGGING);
+        return new StructureStart(
+                structure, origin, 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static final class IdentityStringPoolElement extends StructurePoolElement {
+        private IdentityStringPoolElement() {
+            super(StructureTemplatePool.Projection.RIGID);
+        }
+
+        @Override
+        public Vec3i getSize(StructureTemplateManager templateManager, Rotation rotation) {
+            return new Vec3i(1, 1, 1);
+        }
+
+        @Override
+        public List<StructureTemplate.JigsawBlockInfo> getShuffledJigsawBlocks(
+                StructureTemplateManager templateManager, BlockPos position,
+                Rotation rotation, RandomSource random) {
+            return List.of();
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return new BoundingBox(position);
+        }
+
+        @Override
+        public boolean place(StructureTemplateManager templateManager,
+                             WorldGenLevel world, StructureManager structureManager,
+                             ChunkGenerator chunkGenerator, BlockPos position, BlockPos pivot,
+                             Rotation rotation, BoundingBox area, RandomSource random,
+                             LiquidSettings liquidSettings, boolean keepJigsaws) {
+            return true;
+        }
+
+        @Override
+        public StructurePoolElementType<?> getType() {
+            return StructurePoolElementType.EMPTY;
+        }
+
+        @Override
+        public String toString() {
+            return "IdentityStringPoolElement@"
+                    + Integer.toHexString(System.identityHashCode(this));
+        }
+    }
+
+    private static ChunkPos outsideLiveBounds(NativeStructureOwnershipRecord ownership,
+                                              StructureStart start) {
+        for (int chunkX = ownership.referenceMinChunkX();
+             chunkX <= ownership.referenceMaxChunkX(); chunkX++) {
+            for (int chunkZ = ownership.referenceMinChunkZ();
+                 chunkZ <= ownership.referenceMaxChunkZ(); chunkZ++) {
+                ChunkPos candidate = new ChunkPos(chunkX, chunkZ);
+                if (!start.getBoundingBox().intersects(
+                        candidate.getMinBlockX(), candidate.getMinBlockZ(),
+                        candidate.getMaxBlockX(), candidate.getMaxBlockZ())) {
+                    return candidate;
+                }
+            }
+        }
+        return null;
+    }
+}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipRecoveryTest.java

@@ -0,0 +1,185 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.framework.StructurePlacementGrid;
+import art.arcane.iris.engine.object.IrisNativeStructure;
+import art.arcane.iris.engine.object.IrisStructurePlacement;
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import art.arcane.iris.engine.object.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.collection.KList;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureOwnershipRecoveryTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void missingSidecarRecoversExactPolicyEnvelopeAndLocatorAfterReload() {
+        long seed = 5519231L;
+        ChunkPos origin = new ChunkPos(7, -5);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                expected, 0, 80, -64, 320);
+        int expectedLocatorY = NativeStructureOwnershipFingerprint.locatorY(expected);
+        NativeStructureStartPlan plan = plan(origin, "recovery-exact", 24);
+        StructureStart reloaded = new StructureStart(
+                structure,
+                origin,
+                expected.getReferences(),
+                OceanMonumentStructure.regeneratePiecesAfterLoad(
+                        origin, seed, new PiecesContainer(expected.getPieces()))
+        );
+
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, reloaded,
+                        plan, expected, false);
+
+        assertNotNull(recovered);
+        assertEquals(StructurePlacementGrid.placementIdentity(plan.placement()),
+                recovered.placementIdentity());
+        assertEquals(expectedLocatorY, recovered.locatorY());
+        assertNotEquals(NativeStructureOwnershipFingerprint.locatorY(reloaded),
+                recovered.locatorY());
+        assertEquals(IrisStructureTerrainMode.FORCE_CARVE,
+                recovered.restoredDecision().terrain().resolvedMode());
+        assertEquals(24, recovered.restoredDecision().terrain().getHorizontalPadding());
+        assertTrue(recovered.referenceMinChunkX()
+                < NativeStructureReferenceEnvelope.contentBounds(reloaded).minX() >> 4);
+    }
+
+    @Test
+    public void naturalSameKeyStartRemainsUnownedWhenOriginIsAmbiguous() {
+        long seed = 22817L;
+        ChunkPos origin = new ChunkPos(-3, 6);
+        OceanMonumentStructure structure = structure();
+        StructureStart natural = monumentStart(structure, origin, seed);
+        NativeStructureStartPlan plan = plan(origin, "natural-ambiguous", 0);
+
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, natural,
+                        plan, natural, true);
+
+        assertNull(recovered);
+    }
+
+    @Test
+    public void changedPlacementIdentityOrGeometryCannotRecoverOwnership() {
+        long seed = 991723L;
+        ChunkPos origin = new ChunkPos(2, 4);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        StructureStart changedGeometry = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : changedGeometry.getPieces()) {
+            piece.move(1, 0, 0);
+        }
+        NativeStructureStartPlan originalIdentity = plan(
+                origin, "original-identity", 0);
+        NativeStructureStartPlan changedIdentity = plan(
+                new ChunkPos(origin.x() + 1, origin.z()), "changed-identity", 0);
+
+        assertNotEquals(
+                StructurePlacementGrid.placementIdentity(originalIdentity.placement()),
+                StructurePlacementGrid.placementIdentity(changedIdentity.placement()));
+        assertNull(NativeStructureOwnershipRecovery.proveCandidate(
+                "minecraft:monument", structure, expected,
+                changedIdentity, expected, false));
+        assertNull(NativeStructureOwnershipRecovery.proveCandidate(
+                "minecraft:monument", structure, changedGeometry,
+                plan(origin, "geometry-check", 0), expected, false));
+    }
+
+    @Test
+    public void recoveredEnvelopeStillRequiresExactFingerprint() {
+        long seed = 81337L;
+        ChunkPos origin = new ChunkPos(-8, -9);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, expected,
+                        plan(origin, "fingerprint-check", 16), expected, false);
+        assertNotNull(recovered);
+
+        StructureStart moved = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : moved.getPieces()) {
+            piece.move(0, 0, 1);
+        }
+
+        assertFalse(NativeStructureOwnershipFingerprint.matches(recovered, moved));
+    }
+
+    private static OceanMonumentStructure structure() {
+        return new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+    }
+
+    private static StructureStart monumentStart(OceanMonumentStructure structure,
+                                                 ChunkPos origin, long seed) {
+        WorldgenRandom random = new WorldgenRandom(
+                new LegacyRandomSource(RandomSupport.generateUniqueSeed()));
+        random.setLargeFeatureSeed(seed, origin.x(), origin.z());
+        Direction orientation = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+        OceanMonumentPieces.MonumentBuilding building =
+                new OceanMonumentPieces.MonumentBuilding(
+                        random,
+                        origin.getMinBlockX() - 29,
+                        origin.getMinBlockZ() - 29,
+                        orientation
+                );
+        return new StructureStart(
+                structure, origin, 0, new PiecesContainer(List.of(building)));
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin,
+                                                  String placementId,
+                                                  int horizontalPadding) {
+        IrisNativeStructure source = new IrisNativeStructure()
+                .setStructure("minecraft:monument")
+                .setWeight(1);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(horizontalPadding);
+        IrisStructurePlacement placement = new IrisStructurePlacement()
+                .setPlacementId(placementId)
+                .setTerrain(terrain)
+                .setNativeStructures(new KList<IrisNativeStructure>().qadd(source));
+        return new NativeStructureStartPlan(
+                placement,
+                source,
+                origin.x(),
+                origin.z(),
+                NativeStructureReferenceEnvelope.contentBounds(
+                        monumentStart(structure(), origin, 1L)).minY()
+        );
+    }
+}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorEncaseTest.java

@@ -7,22 +7,35 @@ import art.arcane.iris.engine.object.IrisStructureYBand;
 import art.arcane.volmlib.util.math.RNG;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
 import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.server.Bootstrap;
 import net.minecraft.util.RandomSource;
 import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
 import net.minecraft.world.level.WorldGenLevel;
 import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
 import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.dimension.BuiltinDimensionTypes;
 import net.minecraft.world.level.levelgen.GenerationStep;
 import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.StructurePiece;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
 import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
 import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
 import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlockIgnoreProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
@@ -31,14 +44,16 @@ import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Proxy;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.BitSet;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 
 public class NativeStructurePostProcessorEncaseTest {
@@ -98,6 +113,96 @@ public class NativeStructurePostProcessorEncaseTest {
                 state(blocks, bounds.minX(), 0, bounds.minZ()));
     }
 
+    @Test
+    public void defaultEncaseMaterialFollowsVanillaDimensionTerrain() {
+        assertEquals(Blocks.NETHERRACK.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.NETHER, 64));
+        assertEquals(Blocks.END_STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.END, 64));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.OVERWORLD, 64));
+    }
+
+    @Test
+    public void sourceEncaseMaterialFollowsNearbyIrisTerrain() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(4, 64, 8);
+        put(blocks, fill.getX() + 3, fill.getY(), fill.getZ(), Blocks.TUFF.defaultBlockState());
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(world(blocks), fill));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotIgnoresPreviouslyDecoratedAdjacentChunks() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(0, 64, 8);
+        put(blocks, -1, 64, 8, Blocks.OAK_PLANKS.defaultBlockState());
+        put(blocks, 3, 64, 8, Blocks.TUFF.defaultBlockState());
+        WorldGenLevel world = world(blocks);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                sourceSnapshot(world, new BoundingBox(0, 64, 0, 15, 64, 15));
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(
+                        world, fill, sourceTerrain));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotIsStableAcrossEarlierFillsInTheSameChunk() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(0, 64, 8);
+        put(blocks, 3, 64, 8, Blocks.TUFF.defaultBlockState());
+        WorldGenLevel world = world(blocks);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                sourceSnapshot(world, new BoundingBox(0, 64, 0, 15, 64, 15));
+        put(blocks, 1, 64, 8, Blocks.OAK_PLANKS.defaultBlockState());
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(
+                        world, fill, sourceTerrain));
+    }
+
+    @Test
+    public void sourceMaterialRejectsStructureBlocksAndOresBeforeDimensionFallback() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(4, -20, 8);
+        put(blocks, 3, -20, 8, Blocks.OAK_PLANKS.defaultBlockState());
+        put(blocks, 5, -20, 8, Blocks.STONE_BRICKS.defaultBlockState());
+        put(blocks, 4, -20, 7, Blocks.IRON_ORE.defaultBlockState());
+
+        assertEquals(Blocks.DEEPSLATE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(world(blocks), fill));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotOnlyAllocatesActualFillLayers() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox area = new BoundingBox(0, -2032, 0, 15, 2030, 15);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                NativeStructureTerrainIntegrator.captureSourceTerrain(
+                        world(new HashMap<>()), area,
+                        List.of(new NativeStructureTerrainIntegrator.TerrainTarget(
+                                "test:bounded-snapshot", start,
+                                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))));
+
+        assertNotNull(sourceTerrain);
+        assertEquals(23 * 16 * 16, sourceTerrain.sampledCells());
+    }
+
+    @Test
+    public void customDimensionKeyUsesRegisteredVanillaDimensionType() {
+        ResourceKey<Level> customDimension = ResourceKey.create(
+                Registries.DIMENSION, Identifier.parse("iris:custom_nether"));
+
+        assertEquals(Blocks.NETHERRACK.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(
+                        customDimension, BuiltinDimensionTypes.NETHER, null, 64));
+        assertEquals(Blocks.END_STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(
+                        customDimension, BuiltinDimensionTypes.END, null, 64));
+    }
+
     @Test
     public void configuredEncasePaletteReplacesTheDefaultMaterial() {
         StructureStart start = start(TerrainAdjustment.BURY, 64);
@@ -129,58 +234,170 @@ public class NativeStructurePostProcessorEncaseTest {
     }
 
     @Test
-    public void buryAndEncapsulateAdaptationsAutoDefaultToEncase() {
-        for (TerrainAdjustment adjustment : List.of(TerrainAdjustment.BURY, TerrainAdjustment.ENCAPSULATE)) {
+    public void omittedTerrainConfigurationRetainsSourceSemantics() {
+        for (TerrainAdjustment adjustment : TerrainAdjustment.values()) {
             IrisStructureTerrain resolved = NativeStructureTerrainIntegrator.resolveNativeTerrain(
                     start(adjustment, 64), null);
 
-            assertEquals(IrisStructureTerrainMode.ENCASE, resolved.resolvedMode());
-            assertEquals(3, resolved.getHorizontalPadding());
-            assertEquals(3, resolved.getCeilingPadding());
-            assertEquals(3, resolved.getFloorPadding());
-            assertNull(resolved.getEncasePalette());
+            assertEquals(IrisStructureTerrainMode.SOURCE, resolved.resolvedMode());
         }
     }
 
     @Test
-    public void otherAdaptationsNeverAutoDefaultToEncase() {
-        for (TerrainAdjustment adjustment : List.of(
-                TerrainAdjustment.NONE, TerrainAdjustment.BEARD_THIN, TerrainAdjustment.BEARD_BOX)) {
-            assertNull(NativeStructureTerrainIntegrator.resolveNativeTerrain(
-                    start(adjustment, 64), null));
-        }
+    public void sourceBuryUsesTheVanillaSixByTwelveInfluenceEnvelope() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        int groundY = bounds.minY();
+        BoundingBox area = new BoundingBox(
+                bounds.minX() - 7, groundY - 13, bounds.minZ(),
+                bounds.maxX(), groundY + 13, bounds.maxZ());
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), area, "test:bury", start,
+                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE), null);
+
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX() - 5, groundY, bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 11, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 6, groundY, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 12, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 7, groundY, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 13, bounds.minZ()));
+    }
+
+    @Test
+    public void sourceEncapsulateWrapsTheFullPieceBounds() {
+        StructureStart start = start(TerrainAdjustment.ENCAPSULATE, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        BoundingBox area = new BoundingBox(
+                bounds.minX() - 13, bounds.minY(), bounds.minZ(),
+                bounds.maxX(), bounds.maxY() + 13, bounds.maxZ());
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), area, "test:encapsulate", start,
+                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE), null);
+
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX() - 11, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 11, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 12, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 12, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 13, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 13, bounds.minZ()));
+    }
+
+    @Test
+    public void sourceTerrainDensityOnlyUsesRigidPoolPieces() {
+        PoolElementStructurePiece terrainMatching = poolPiece(StructureTemplatePool.Projection.TERRAIN_MATCHING);
+        PoolElementStructurePiece rigid = poolPiece(StructureTemplatePool.Projection.RIGID);
+
+        assertFalse(NativeStructureTerrainIntegrator.isSourceRigidPiece(terrainMatching));
+        assertTrue(NativeStructureTerrainIntegrator.isSourceRigidPiece(rigid));
+    }
+
+    @Test
+    public void sourceJunctionTerrainUsesTheStrictLowerTwelveBlockEnvelope() {
+        assertTrue(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -1, 0));
+        assertTrue(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -11, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, 0, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -12, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(12, -1, 0));
     }
 
     @Test
     public void explicitTerrainConfigurationWinsOverAutoEncase() {
         IrisStructureTerrain configured = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.SOURCE);
+                .setMode(IrisStructureTerrainMode.PRESERVE);
 
         assertSame(configured, NativeStructureTerrainIntegrator.resolveNativeTerrain(
                 start(TerrainAdjustment.BURY, 64), configured));
     }
 
+    @Test
+    public void legacyTemplateAirIsClearedAfterEveryTerrainFillPath() {
+        IrisStructureTerrain source = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.SOURCE);
+        IrisStructureTerrain preserve = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.PRESERVE);
+        IrisStructureTerrain encase = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.ENCASE);
+
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BURY, 64), source));
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BEARD_BOX, 64), source));
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.NONE, 64), encase));
+        assertFalse(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.NONE, 64), source));
+        assertFalse(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BURY, 64), preserve));
+    }
+
     @Test
     public void encaseReservesTheNeighborChunkEnvelope() {
         StructureStart generated = start(TerrainAdjustment.BURY, 64);
-        BoundingBox content = generated.getBoundingBox();
+        BoundingBox sourceBounds = generated.getBoundingBox();
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.ENCASE)
+                .setHorizontalPadding(4);
 
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
                 generated,
                 generated.getStructure(),
                 0,
-                null,
-                new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.ENCASE)
-                        .setHorizontalPadding(4));
+                terrain);
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                wrapped, wrapped.getStructure(), terrain);
 
-        assertEquals(content.minX() - 4, wrapped.getBoundingBox().minX());
-        assertEquals(content.maxX() + 4, wrapped.getBoundingBox().maxX());
-        assertEquals(content.minZ() - 4, wrapped.getBoundingBox().minZ());
-        assertEquals(content.maxZ() + 4, wrapped.getBoundingBox().maxZ());
-        assertEquals(2, wrapped.getPieces().stream()
-                .filter(NativeStructureReferenceEnvelope::isMarker)
-                .count());
+        assertEquals(sourceBounds, wrapped.getBoundingBox());
+        assertEquals(content.minX() - 4, referenceBounds.minX());
+        assertEquals(content.maxX() + 4, referenceBounds.maxX());
+        assertEquals(content.minZ() - 4, referenceBounds.minZ());
+        assertEquals(content.maxZ() + 4, referenceBounds.maxZ());
+        assertEquals(generated.getPieces().size(), wrapped.getPieces().size());
+    }
+
+    @Test
+    public void referenceEnvelopeRejectsChunkCoordinateOverflow() {
+        StructureStart generated = start(TerrainAdjustment.NONE, 64);
+        StructureStart extreme = new StructureStart(
+                generated.getStructure(), new ChunkPos(Integer.MAX_VALUE, 0), 0,
+                new PiecesContainer(generated.getPieces()));
+
+        assertThrows(IllegalStateException.class, () ->
+                NativeStructureReferenceEnvelope.referenceBounds(
+                        extreme, extreme.getStructure(), new IrisStructureTerrain()));
+    }
+
+    @Test
+    public void explicitTerrainEnvelopeDoesNotInheritSourceAdjustment() {
+        StructureStart generated = start(TerrainAdjustment.BURY, 64);
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.ENCASE)
+                .setHorizontalPadding(112);
+
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated, generated.getStructure(), 0, terrain);
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                wrapped, wrapped.getStructure(), terrain);
+
+        assertEquals(content.minX() - 112, referenceBounds.minX());
+        assertEquals(content.maxX() + 112, referenceBounds.maxX());
     }
 
     @Test
@@ -259,6 +476,24 @@ public class NativeStructurePostProcessorEncaseTest {
                 structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
     }
 
+    private static PoolElementStructurePiece poolPiece(StructureTemplatePool.Projection projection) {
+        BlockPos position = new BlockPos(0, 64, 0);
+        StructurePoolElement element = StructurePoolElement.single(
+                "minecraft:empty",
+                Holder.direct(new StructureProcessorList(List.of(
+                        BlockIgnoreProcessor.STRUCTURE_AND_AIR))),
+                LiquidSettings.APPLY_WATERLOGGING
+        ).apply(projection);
+        return new PoolElementStructurePiece(
+                null,
+                element,
+                position,
+                0,
+                Rotation.NONE,
+                new BoundingBox(position),
+                LiquidSettings.APPLY_WATERLOGGING);
+    }
+
     private static WorldGenLevel world(Map<BlockPos, BlockState> blocks) {
         InvocationHandler handler = (proxy, method, arguments) -> {
             String methodName = method.getName();
@@ -275,6 +510,9 @@ public class NativeStructurePostProcessorEncaseTest {
             if (methodName.equals("getSeed")) {
                 return TEST_SEED;
             }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
             if (methodName.equals("hashCode")) {
                 return System.identityHashCode(proxy);
             }
@@ -290,6 +528,14 @@ public class NativeStructurePostProcessorEncaseTest {
                 WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
     }
 
+    private static NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceSnapshot(
+            WorldGenLevel world, BoundingBox area) {
+        BitSet requiredLayers = new BitSet(area.getYSpan());
+        requiredLayers.set(0, area.getYSpan());
+        return NativeStructureTerrainIntegrator.SourceTerrainSnapshot.capture(
+                world, area, requiredLayers);
+    }
+
     private static void put(Map<BlockPos, BlockState> blocks,
                            int x, int y, int z, BlockState state) {
         blocks.put(new BlockPos(x, y, z), state);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorMonumentTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import art.arcane.iris.engine.object.IrisStructureTerrainMode;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.Direction;
 import net.minecraft.core.HolderSet;
@@ -16,7 +18,12 @@ import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStru
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertSame;
@@ -80,6 +87,25 @@ public class NativeStructurePostProcessorMonumentTest {
         assertEquals(51, start.getBoundingBox().maxY());
     }
 
+    @Test
+    public void referenceEnvelopeDoesNotAddMonumentPieces() {
+        StructureStart start = monumentStart(1337L);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                start,
+                start.getStructure(),
+                0,
+                new IrisStructureTerrain()
+                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                        .setHorizontalPadding(4));
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                wrapped, "minecraft:monument", 0, 63, -64, 320,
+                false, false, null, (x, z) -> 0);
+
+        assertEquals(0, offset);
+        assertEquals(1, wrapped.getPieces().size());
+    }
+
     @Test
     public void vanillaReloadRegenerationIsRealignedBeforePlacement() {
         long seed = 1337L;
@@ -101,6 +127,42 @@ public class NativeStructurePostProcessorMonumentTest {
         assertEquals(48, reloaded.getBoundingBox().maxY());
     }
 
+    @Test
+    public void neighboringChunkPlacementRealignsReloadedMonumentOnce() throws Exception {
+        long seed = 1337L;
+        ChunkPos chunkPos = new ChunkPos(0, 0);
+        StructureStart initial = monumentStart(seed);
+        NativeStructureVerticalPlacer.applyVerticalPlacement(
+                initial, "minecraft:monument", 0, 50, -256, 512,
+                false, false, null, (x, z) -> 0);
+        PiecesContainer regenerated = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                chunkPos, seed, new PiecesContainer(initial.getPieces()));
+        StructureStart reloaded = new StructureStart(
+                monumentStructure(), chunkPos, 0, regenerated);
+        ExecutorService executor = Executors.newFixedThreadPool(8);
+        CountDownLatch release = new CountDownLatch(1);
+        List<Future<?>> futures = new ArrayList<>();
+        try {
+            for (int task = 0; task < 16; task++) {
+                futures.add(executor.submit(() -> {
+                    release.await();
+                    NativeStructureVerticalPlacer.ensureMonumentSeaLevelAlignment(
+                            reloaded, "minecraft:monument", 0, 50, -256, 512);
+                    return null;
+                }));
+            }
+            release.countDown();
+            for (Future<?> future : futures) {
+                future.get();
+            }
+        } finally {
+            executor.shutdownNow();
+        }
+
+        assertEquals(26, reloaded.getBoundingBox().minY());
+        assertEquals(48, reloaded.getBoundingBox().maxY());
+    }
+
     @Test
     public void impossibleSeaLevelAlignmentFailsInsteadOfClippingTheMonument() {
         StructureStart start = monumentStart(1337L);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorScatteredFeatureTest.java

@@ -135,6 +135,27 @@ public class NativeStructurePostProcessorScatteredFeatureTest {
         assertTrue(field.trySetAccessible());
     }
 
+    @Test
+    public void datapackOverridesOfSpecialVanillaIdsUseGenericPlacement() {
+        StructureStart pyramidOverride = swampStart(
+                new SwampHutPiece(RandomSource.create(43L), 0, 0));
+        int pyramidMinY = pyramidOverride.getBoundingBox().minY();
+        int pyramidOffset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                pyramidOverride, "minecraft:desert_pyramid", 5,
+                63, -64, 320, false, false, null, (x, z) -> 200);
+
+        assertEquals(5, pyramidOffset);
+        assertEquals(pyramidMinY + 5, pyramidOverride.getBoundingBox().minY());
+
+        StructureStart monumentOverride = swampStart(
+                new SwampHutPiece(RandomSource.create(47L), 0, 0));
+        int monumentMinY = monumentOverride.getBoundingBox().minY();
+        NativeStructureVerticalPlacer.ensureMonumentSeaLevelAlignment(
+                monumentOverride, "minecraft:monument", 0, 40, -64, 320);
+
+        assertEquals(monumentMinY, monumentOverride.getBoundingBox().minY());
+    }
+
     private static StructureStart desertStart(StructurePiece piece) {
         Structure structure = new DesertPyramidStructure(new Structure.StructureSettings(HolderSet.empty()));
         return start(structure, piece);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorSurfaceTerrainTest.java

@@ -5,23 +5,41 @@ import art.arcane.iris.engine.object.IrisStructureCarveShape;
 import art.arcane.iris.engine.object.IrisStructureTerrain;
 import art.arcane.iris.engine.object.IrisStructureTerrainMode;
 import com.mojang.datafixers.util.Either;
+import com.mojang.serialization.Codec;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
 import net.minecraft.core.HolderSet;
+import net.minecraft.core.IdMapper;
 import net.minecraft.server.Bootstrap;
 import net.minecraft.util.RandomSource;
 import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
 import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.Rotation;
 import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.Strategy;
+import net.minecraft.world.level.chunk.UpgradeData;
 import net.minecraft.world.level.levelgen.GenerationStep;
 import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
 import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
 import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
 import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
 import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
 import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
 import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
@@ -35,15 +53,22 @@ import java.lang.reflect.Field;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Proxy;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
 
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 
 public class NativeStructurePostProcessorSurfaceTerrainTest {
@@ -60,34 +85,148 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
     }
 
     @Test
-    public void onlySurfaceBeardThinStructuresPrepareTerrain() {
+    public void sourceBeardAdjustmentsPrepareTerrainAcrossDeclaredSteps() {
         assertTrue(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
                 TerrainAdjustment.BEARD_THIN, GenerationStep.Decoration.SURFACE_STRUCTURES));
-        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
-                TerrainAdjustment.BURY, GenerationStep.Decoration.SURFACE_STRUCTURES));
-        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
-                TerrainAdjustment.BEARD_BOX, GenerationStep.Decoration.SURFACE_STRUCTURES));
-        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
-                TerrainAdjustment.ENCAPSULATE, GenerationStep.Decoration.SURFACE_STRUCTURES));
+        assertTrue(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
+                TerrainAdjustment.BEARD_BOX, GenerationStep.Decoration.FLUID_SPRINGS));
+        assertTrue(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
+                TerrainAdjustment.BEARD_THIN, GenerationStep.Decoration.UNDERGROUND_STRUCTURES));
     }
 
     @Test
-    public void undergroundAdjustmentsNeverPrepareSurfaceTerrain() {
-        for (TerrainAdjustment adjustment : List.of(
-                TerrainAdjustment.BEARD_THIN,
-                TerrainAdjustment.BURY,
-                TerrainAdjustment.BEARD_BOX,
-                TerrainAdjustment.ENCAPSULATE)) {
-            assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
-                    adjustment, GenerationStep.Decoration.UNDERGROUND_STRUCTURES));
+    public void nonBeardAdjustmentsDoNotPrepareSurfaceTerrain() {
+        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
+                TerrainAdjustment.BURY, GenerationStep.Decoration.SURFACE_STRUCTURES));
+        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
+                TerrainAdjustment.ENCAPSULATE, GenerationStep.Decoration.SURFACE_STRUCTURES));
+        assertFalse(NativeStructureSurfaceFitter.shouldPrepareSurfaceTerrain(
+                TerrainAdjustment.NONE, GenerationStep.Decoration.FLUID_SPRINGS));
+    }
+
+    @Test
+    public void explicitTerrainOverrideDisablesSourceBeardFitting() {
+        StructureStart start = desertStart(TerrainAdjustment.BEARD_BOX);
+
+        assertTrue(NativeStructureSurfaceFitter.requiresSurfaceTerrain(
+                new NativeStructureTerrainIntegrator.TerrainTarget(
+                        "test:beard_box", start,
+                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))));
+        assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(
+                new NativeStructureTerrainIntegrator.TerrainTarget(
+                        "test:beard_box", start,
+                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.PRESERVE))));
+    }
+
+    @Test
+    public void beardBoxUsesTheFullRigidHeightWhileBeardThinUsesTheGroundPlane() {
+        NativeStructureSurfaceFitter.SurfaceAnchor thin =
+                new NativeStructureSurfaceFitter.SurfaceAnchor(0, 4, 0, 4, 64, 2);
+        NativeStructureSurfaceFitter.SurfaceAnchor box =
+                new NativeStructureSurfaceFitter.SurfaceAnchor(
+                        0, 4, 0, 4, 64, 2, 65, 90);
+
+        assertEquals(80, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(thin), 2, 2, 80));
+        assertEquals(64, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(box), 2, 2, 80));
+    }
+
+    @Test
+    public void beardInfluenceBeginsAtGroundYRatherThanTheSurfaceBlock() {
+        BoundingBox bounds = new BoundingBox(0, 64, 0, 4, 90, 4);
+        NativeStructureSurfaceFitter.SurfaceAnchor thin =
+                NativeStructureSurfaceFitter.surfaceAnchor(
+                        bounds, 68, 2, TerrainAdjustment.BEARD_THIN);
+        NativeStructureSurfaceFitter.SurfaceAnchor box =
+                NativeStructureSurfaceFitter.surfaceAnchor(
+                        bounds, 68, 2, TerrainAdjustment.BEARD_BOX);
+
+        assertEquals(67, thin.meetY());
+        assertEquals(0, thin.verticalDistance(68));
+        assertEquals(1, thin.verticalDistance(67));
+        assertEquals(0, box.verticalDistance(68));
+        assertEquals(1, box.verticalDistance(67));
+        assertEquals(0, box.verticalDistance(90));
+        assertEquals(1, box.verticalDistance(91));
+    }
+
+    @Test
+    public void rigidFootprintsRaiseTerrainAcrossGapsLargerThanTheBeardKernel() {
+        NativeStructureSurfaceFitter.SurfaceAnchor rigid = anchor(72, 2);
+        NativeStructureSurfaceFitter.SurfaceAnchor junction = anchor(72, 1);
+
+        assertEquals(72, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(rigid), 2, 2, 40));
+        assertEquals(40, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(junction), 2, 2, 40));
+    }
+
+    @Test
+    public void elevatedRigidFootprintsBlendIntoAHorizontalRescueTaper() {
+        int originalY = 40;
+        int kernelEdge = NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(51, 2)), 5, 2, originalY);
+        int gapThirteen = NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(52, 2)), 5, 2, originalY);
+        int gapEighteen = NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(57, 2)), 5, 2, originalY);
+        int gapTwentyFour = NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(63, 2)), 5, 2, originalY);
+
+        assertEquals(originalY, kernelEdge);
+        assertTrue(gapThirteen >= kernelEdge);
+        assertTrue(gapEighteen > gapThirteen);
+        assertTrue(gapTwentyFour > gapEighteen);
+        assertTrue(gapTwentyFour < 63);
+        assertEquals(originalY, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(63, 2)), 16, 2, originalY));
+        assertEquals(originalY, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(63, 1)), 5, 2, originalY));
+        assertEquals(80, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(anchor(64, 2)), 5, 2, 80));
+    }
+
+    @Test
+    public void projectedCenterAndRigidChildrenShareTerrainSupportAcrossTheAssembly() {
+        Structure structure = new DesertPyramidStructure(
+                new Structure.StructureSettings(
+                        HolderSet.empty(), Map.of(),
+                        GenerationStep.Decoration.SURFACE_STRUCTURES,
+                        TerrainAdjustment.BEARD_BOX));
+        PoolElementStructurePiece center = rigidPiece(
+                new BoundingBox(0, 71, 0, 3, 80, 3), 1);
+        PoolElementStructurePiece child = rigidPiece(
+                new BoundingBox(10, 65, 0, 13, 76, 3), 7);
+        StructureStart start = new StructureStart(
+                structure, new ChunkPos(0, 0), 0,
+                new PiecesContainer(List.of(center, child)));
+        BoundingBox area = new BoundingBox(0, 60, 0, 15, 90, 15);
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        for (int x = area.minX(); x <= area.maxX(); x++) {
+            for (int z = area.minZ(); z <= area.maxZ(); z++) {
+                put(blocks, x, 63, z, Blocks.DIRT.defaultBlockState());
+                put(blocks, x, 64, z, Blocks.GRASS_BLOCK.defaultBlockState());
+            }
         }
+
+        NativeStructureSurfaceFitter.prepareSurfaceStructures(
+                world(blocks), area,
+                List.of(new NativeStructureTerrainIntegrator.TerrainTarget(
+                        "nova_structures:tavern_oak", start,
+                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))),
+                (x, z) -> 64);
+
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 1, 71, 1));
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 11, 71, 1));
+        assertEquals(Blocks.DIRT.defaultBlockState(), state(blocks, 11, 70, 1));
     }
 
     @Test
     public void surfaceAnchorIsFlushInsideAndUnchangedAtRadius() {
-        NativeStructureSurfaceFitter.SurfaceAnchor anchor = anchor(80, 2);
+        NativeStructureSurfaceFitter.SurfaceAnchor anchor = anchor(72, 2);
 
-        assertEquals(80, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(72, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(anchor), 2, 2, 64));
         assertEquals(64, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(anchor), 16, 2, 64));
@@ -97,54 +236,88 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
     @Test
     public void surfaceAnchorRaisesAndLowersThroughTheTaper() {
-        NativeStructureSurfaceFitter.SurfaceAnchor raised = anchor(80, 2);
+        NativeStructureSurfaceFitter.SurfaceAnchor raised = anchor(68, 2);
         NativeStructureSurfaceFitter.SurfaceAnchor lowered = anchor(64, 2);
 
-        assertEquals(68, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(64, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(raised), 10, 2, 64));
-        assertEquals(76, NativeStructureSurfaceFitter.resolveSurfaceTarget(
-                List.of(lowered), 10, 2, 80));
+        assertEquals(67, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+                List.of(lowered), 10, 2, 68));
     }
 
     @Test
     public void containingRigidFloorsHaveDeterministicPriority() {
         NativeStructureSurfaceFitter.SurfaceAnchor rigid = anchor(70, 2);
-        NativeStructureSurfaceFitter.SurfaceAnchor junction = anchor(90, 1);
+        NativeStructureSurfaceFitter.SurfaceAnchor junction = anchor(74, 1);
 
         assertEquals(70, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(rigid, junction), 2, 2, 64));
         assertEquals(70, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(junction, rigid), 2, 2, 64));
 
-        NativeStructureSurfaceFitter.SurfaceAnchor weakTie = anchor(48, 1);
-        NativeStructureSurfaceFitter.SurfaceAnchor strongTie = anchor(80, 2);
-        assertEquals(80, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        NativeStructureSurfaceFitter.SurfaceAnchor weakTie = anchor(58, 1);
+        NativeStructureSurfaceFitter.SurfaceAnchor strongTie = anchor(70, 2);
+        assertEquals(70, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(weakTie, strongTie), 2, 2, 64));
-        assertEquals(80, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(70, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(strongTie, weakTie), 2, 2, 64));
     }
 
+    @Test
+    public void stackedRigidPiecesPreserveTheLowerAuthoredSurface() {
+        Structure structure = new DesertPyramidStructure(
+                new Structure.StructureSettings(
+                        HolderSet.empty(), Map.of(),
+                        GenerationStep.Decoration.SURFACE_STRUCTURES,
+                        TerrainAdjustment.BEARD_BOX));
+        PoolElementStructurePiece lower = rigidPiece(
+                new BoundingBox(0, 62, 0, 4, 65, 4), 1);
+        PoolElementStructurePiece upper = rigidPiece(
+                new BoundingBox(0, 66, 0, 4, 78, 4), 1);
+        StructureStart start = new StructureStart(
+                structure, new ChunkPos(0, 0), 0,
+                new PiecesContainer(List.of(upper, lower)));
+        BoundingBox area = new BoundingBox(0, 58, 0, 4, 78, 4);
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        for (int x = area.minX(); x <= area.maxX(); x++) {
+            for (int z = area.minZ(); z <= area.maxZ(); z++) {
+                put(blocks, x, 59, z, Blocks.DIRT.defaultBlockState());
+                put(blocks, x, 60, z, Blocks.GRASS_BLOCK.defaultBlockState());
+            }
+        }
+
+        NativeStructureSurfaceFitter.prepareSurfaceStructures(
+                world(blocks), area,
+                List.of(new NativeStructureTerrainIntegrator.TerrainTarget(
+                        "nova_structures:tavern_oak", start,
+                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))),
+                (x, z) -> 60);
+
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 2, 62, 2));
+        assertEquals(Blocks.AIR.defaultBlockState(), state(blocks, 2, 65, 2));
+    }
+
     @Test
     public void containingFootprintOverridesAnAdjacentPiecesFalloff() {
         NativeStructureSurfaceFitter.SurfaceAnchor local =
-                new NativeStructureSurfaceFitter.SurfaceAnchor(0, 4, 0, 4, 65, 2);
+                new NativeStructureSurfaceFitter.SurfaceAnchor(0, 4, 0, 4, 66, 2);
         NativeStructureSurfaceFitter.SurfaceAnchor adjacent =
-                new NativeStructureSurfaceFitter.SurfaceAnchor(5, 9, 0, 4, 80, 2);
+                new NativeStructureSurfaceFitter.SurfaceAnchor(5, 9, 0, 4, 70, 2);
 
-        assertEquals(77, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(65, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(adjacent), 4, 2, 64));
-        assertEquals(65, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(66, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(local, adjacent), 4, 2, 64));
-        assertEquals(65, NativeStructureSurfaceFitter.resolveSurfaceTarget(
+        assertEquals(66, NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(adjacent, local), 4, 2, 64));
     }
 
     @Test
     public void opposingFalloffsBlendWithoutAnAbruptMidpointSeam() {
         NativeStructureSurfaceFitter.SurfaceAnchor high =
-                new NativeStructureSurfaceFitter.SurfaceAnchor(0, 0, 0, 0, 80, 2);
+                new NativeStructureSurfaceFitter.SurfaceAnchor(0, 0, 0, 0, 70, 2);
         NativeStructureSurfaceFitter.SurfaceAnchor low =
-                new NativeStructureSurfaceFitter.SurfaceAnchor(12, 12, 0, 0, 48, 2);
+                new NativeStructureSurfaceFitter.SurfaceAnchor(12, 12, 0, 0, 58, 2);
         int previous = NativeStructureSurfaceFitter.resolveSurfaceTarget(
                 List.of(high, low), 0, 0, 64);
 
@@ -154,7 +327,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             int reversed = NativeStructureSurfaceFitter.resolveSurfaceTarget(
                     List.of(low, high), x, 0, 64);
             assertEquals(forward, reversed);
-            assertTrue(Math.abs(forward - previous) <= 4);
+            assertTrue(Math.abs(forward - previous) <= 6);
             previous = forward;
         }
         assertEquals(64, NativeStructureSurfaceFitter.resolveSurfaceTarget(
@@ -195,6 +368,44 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(raised, 0, 68, 0));
     }
 
+    @Test
+    public void rigidSurfaceBaseClosesAOneBlockSubsurfaceGap() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        put(blocks, 0, 62, 0, Blocks.STONE.defaultBlockState());
+        put(blocks, 0, 64, 0, Blocks.GRASS_BLOCK.defaultBlockState());
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(blocks), new BlockPos.MutableBlockPos(),
+                0, 0, 64, 64, -64, 319, true);
+
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 63, 0));
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 0, 64, 0));
+    }
+
+    @Test
+    public void rigidSurfaceBaseReconstructsAMissingMeetLayer() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        put(blocks, 0, 62, 0, Blocks.STONE.defaultBlockState());
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(blocks), new BlockPos.MutableBlockPos(),
+                0, 0, 64, 64, -64, 319, true);
+
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 63, 0));
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 64, 0));
+    }
+
+    @Test
+    public void rigidSurfaceBaseReconstructsAMissingMeetLayerAtTheWorldFloor() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(blocks), new BlockPos.MutableBlockPos(),
+                0, 0, -64, -64, -64, 319, true);
+
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, -64, 0));
+    }
+
     @Test
     public void raisedSurfaceTerrainDoesNotSliceTreeBlocks() {
         Map<BlockPos, BlockState> blocks = new HashMap<>();
@@ -213,6 +424,31 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         assertEquals(leaves, state(blocks, 0, 68, 0));
     }
 
+    @Test
+    public void clearedIntersectingTreeCellsBecomeRaisedTerrainSupport() {
+        ProtoChunk chunk = new ProtoChunk(
+                new ChunkPos(0, 0), UpgradeData.EMPTY,
+                LevelHeightAccessor.create(-64, 384), containerFactory(), null);
+        write(chunk, 0, 63, 0, Blocks.DIRT.defaultBlockState());
+        write(chunk, 0, 64, 0, Blocks.GRASS_BLOCK.defaultBlockState());
+        write(chunk, 0, 66, 0, Blocks.OAK_LOG.defaultBlockState());
+        write(chunk, 0, 68, 0, Blocks.OAK_LEAVES.defaultBlockState());
+        WorldGenLevel world = world(chunk);
+        BoundingBox area = new BoundingBox(0, 63, 0, 0, 68, 0);
+
+        NativeStructureVegetationClearer.clearIntersectingVegetation(
+                world, chunk, area, List.of(
+                        new NativeStructureVegetationClearer.VegetationTarget(desertStart(), false)));
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(),
+                0, 0, 64, 68, -64, 319);
+
+        assertEquals(Blocks.DIRT.defaultBlockState(), chunk.getBlockState(new BlockPos(0, 65, 0)));
+        assertEquals(Blocks.DIRT.defaultBlockState(), chunk.getBlockState(new BlockPos(0, 66, 0)));
+        assertEquals(Blocks.DIRT.defaultBlockState(), chunk.getBlockState(new BlockPos(0, 67, 0)));
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), chunk.getBlockState(new BlockPos(0, 68, 0)));
+    }
+
     @Test
     public void loweredFluidColumnsRemainFluidFilled() {
         Map<BlockPos, BlockState> blocks = new HashMap<>();
@@ -437,6 +673,47 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         assertNotSame(first, other);
     }
 
+    @Test
+    public void concurrentCarveRequestsShareOneFootprintBuild() throws Exception {
+        StructureStart start = desertStart();
+        int requestCount = 16;
+        ExecutorService executor = Executors.newFixedThreadPool(requestCount);
+        CountDownLatch ready = new CountDownLatch(requestCount);
+        CountDownLatch release = new CountDownLatch(1);
+        List<Future<StructureCarvingFootprint>> futures = new ArrayList<>();
+        try {
+            for (int request = 0; request < requestCount; request++) {
+                futures.add(executor.submit(() -> {
+                    ready.countDown();
+                    release.await();
+                    return NativeStructureTerrainIntegrator.carveFootprint(
+                            start, 11,
+                            NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
+                }));
+            }
+            assertTrue(ready.await(5, TimeUnit.SECONDS));
+            release.countDown();
+            StructureCarvingFootprint expected = futures.getFirst().get();
+            for (Future<StructureCarvingFootprint> future : futures) {
+                assertSame(expected, future.get());
+            }
+        } finally {
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    public void carveFootprintCacheStaysInsideItsCellBudget() {
+        for (int index = 0; index < 40; index++) {
+            NativeStructureTerrainIntegrator.carveFootprint(
+                    desertStart(), 128,
+                    NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
+        }
+
+        assertTrue(NativeStructureTerrainIntegrator.cachedCarveFootprintCells()
+                <= NativeStructureTerrainIntegrator.maximumCachedCarveFootprintCells());
+    }
+
     @Test
     public void organicCarveNeverCutsBelowTheColumnSupportingFloor() {
         StructureStart start = desertStart();
@@ -594,43 +871,48 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
     public void nativeTerrainEnvelopePersistsHorizontalReferenceCoverage() {
         StructureStart generated = desertStart();
         BoundingBox content = generated.getBoundingBox();
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
 
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
                 generated,
                 generated.getStructure(),
                 0,
-                null,
-                new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
-                        .setHorizontalPadding(24));
+                terrain);
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                wrapped, wrapped.getStructure(), terrain);
 
         assertEquals(content, NativeStructureReferenceEnvelope.contentBounds(wrapped));
-        assertEquals(content.minX() - 24, wrapped.getBoundingBox().minX());
-        assertEquals(content.minZ() - 24, wrapped.getBoundingBox().minZ());
-        assertEquals(content.maxX() + 24, wrapped.getBoundingBox().maxX());
-        assertEquals(content.maxZ() + 24, wrapped.getBoundingBox().maxZ());
-        assertEquals(2, wrapped.getPieces().stream()
-                .filter(NativeStructureReferenceEnvelope::isMarker)
-                .count());
+        assertEquals(content, wrapped.getBoundingBox());
+        assertEquals(content.minX() - 24, referenceBounds.minX());
+        assertEquals(content.minZ() - 24, referenceBounds.minZ());
+        assertEquals(content.maxX() + 24, referenceBounds.maxX());
+        assertEquals(content.maxZ() + 24, referenceBounds.maxZ());
+        assertEquals(generated.getPieces().size(), wrapped.getPieces().size());
     }
 
     @Test
-    public void nativeTerrainEnvelopeClipsToMinecraftReferenceCoverage() {
+    public void nativeTerrainEnvelopeClipsOptionalCoverageWithoutDroppingContent() {
         StructureStart generated = desertStart();
+        ChunkPos origin = generated.getChunkPos();
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(124);
 
-        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
-                generated,
-                generated.getStructure(),
-                0,
-                null,
-                new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
-                        .setHorizontalPadding(128));
+        BoundingBox references = NativeStructureReferenceEnvelope.referenceBounds(
+                generated, generated.getStructure(), terrain, "test:clipped_terrain");
+        StructureStart published = NativeStructureReferenceEnvelope.wrapForPublication(
+                generated, generated.getStructure(), 0, terrain, "test:clipped_terrain");
 
-        assertEquals(-128, wrapped.getBoundingBox().minX());
-        assertEquals(-128, wrapped.getBoundingBox().minZ());
-        assertEquals(143, wrapped.getBoundingBox().maxX());
-        assertEquals(143, wrapped.getBoundingBox().maxZ());
+        assertEquals(Math.max(content.minX() - 124, (origin.x() - 8) << 4), references.minX());
+        assertEquals(Math.min(content.maxX() + 124, ((origin.x() + 8) << 4) + 15), references.maxX());
+        assertEquals(Math.max(content.minZ() - 124, (origin.z() - 8) << 4), references.minZ());
+        assertEquals(Math.min(content.maxZ() + 124, ((origin.z() + 8) << 4) + 15), references.maxZ());
+        assertTrue(references.isInside(content.getCenter()));
+        assertTrue(published.isValid());
+        assertEquals(1, generated.getPieces().size());
     }
 
     @Test
@@ -726,6 +1008,16 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         return new NativeStructureSurfaceFitter.SurfaceAnchor(0, 4, 0, 4, meetY, strength);
     }
 
+    private static PoolElementStructurePiece rigidPiece(BoundingBox bounds, int groundLevelDelta) {
+        StructurePoolElement element = StructurePoolElement.single(
+                "minecraft:empty").apply(StructureTemplatePool.Projection.RIGID);
+        return new PoolElementStructurePiece(
+                null, element,
+                new BlockPos(bounds.minX(), bounds.minY(), bounds.minZ()),
+                groundLevelDelta, Rotation.NONE, bounds,
+                LiquidSettings.APPLY_WATERLOGGING);
+    }
+
     private static NativeStructureTerrainIntegrator.OrganicCarve organicCarve(
             StructureStart start, int horizontalPadding) {
         return organicCarve(start, horizontalPadding, 0.85D);
@@ -831,8 +1123,14 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
     }
 
     private static StructureStart desertStart() {
+        return desertStart(TerrainAdjustment.NONE);
+    }
+
+    private static StructureStart desertStart(TerrainAdjustment adjustment) {
         Structure structure = new DesertPyramidStructure(
-                new Structure.StructureSettings(HolderSet.empty()));
+                new Structure.StructureSettings(
+                        HolderSet.empty(), Map.of(),
+                        GenerationStep.Decoration.SURFACE_STRUCTURES, adjustment));
         DesertPyramidPiece piece = new DesertPyramidPiece(RandomSource.create(7L), 0, 0);
         return new StructureStart(
                 structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
@@ -854,6 +1152,9 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             if (methodName.equals("getSeed")) {
                 return TEST_SEED;
             }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
             if (methodName.equals("hashCode")) {
                 return System.identityHashCode(proxy);
             }
@@ -869,6 +1170,62 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                 WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
     }
 
+    private static WorldGenLevel world(ChunkAccess chunk) {
+        InvocationHandler handler = (proxy, method, arguments) -> {
+            String methodName = method.getName();
+            if (methodName.equals("getBlockState")) {
+                return chunk.getBlockState((BlockPos) arguments[0]);
+            }
+            if (methodName.equals("setBlock")) {
+                return chunk.setBlockState(
+                        ((BlockPos) arguments[0]).immutable(),
+                        (BlockState) arguments[1], (int) arguments[2]) != null;
+            }
+            if (methodName.equals("getSeed")) {
+                return TEST_SEED;
+            }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
+            if (methodName.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (methodName.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (methodName.equals("toString")) {
+                return "surface-test-chunk-world";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
+    }
+
+    private static void write(ProtoChunk chunk, int x, int y, int z, BlockState state) {
+        LevelChunkSection section = chunk.getSection(chunk.getSectionIndex(y));
+        section.setBlockState(x, y & 15, z, state, false);
+    }
+
+    private static PalettedContainerFactory containerFactory() {
+        Strategy<BlockState> blockStates = Strategy.createForBlockStates(Block.BLOCK_STATE_REGISTRY);
+        BlockState air = Blocks.AIR.defaultBlockState();
+        IdMapper<Holder<Biome>> biomeIds = new IdMapper<>();
+        Holder<Biome> defaultBiome = Holder.direct((Biome) null);
+        biomeIds.add(defaultBiome);
+        Strategy<Holder<Biome>> biomes = Strategy.createForBiomes(biomeIds);
+        Codec<Holder<Biome>> biomeCodec = Codec.STRING.xmap(
+                name -> defaultBiome, holder -> "iris-test-biome");
+        return new PalettedContainerFactory(
+                blockStates,
+                air,
+                PalettedContainer.codecRW(BlockState.CODEC, blockStates, air),
+                biomes,
+                defaultBiome,
+                PalettedContainer.codecRO(biomeCodec, biomes, defaultBiome),
+                PalettedContainer.codecRW(biomeCodec, biomes, defaultBiome));
+    }
+
     private static void put(Map<BlockPos, BlockState> blocks,
                             int x, int y, int z, BlockState state) {
         blocks.put(new BlockPos(x, y, z), state);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorVegetationTest.java

@@ -1,14 +1,33 @@
 package art.arcane.iris.nativegen;
 
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.levelgen.GenerationStep;
 import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import org.junit.BeforeClass;
 import org.junit.Test;
 
+import java.util.List;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 public class NativeStructurePostProcessorVegetationTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
     @Test
     public void surfaceStructuresClearTreeColumnsAutomatically() {
         assertTrue(NativeStructureVegetationClearer.shouldClearVegetationColumn(100, 100, false));
@@ -26,6 +45,22 @@ public class NativeStructurePostProcessorVegetationTest {
         assertTrue(NativeStructureVegetationClearer.shouldClearVegetationColumn(20, 100, true));
     }
 
+    @Test
+    public void nonForcedValidTargetsReachIntersectionProcessing() {
+        Structure structure = new DesertPyramidStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        StructureStart start = new StructureStart(
+                structure, new ChunkPos(0, 0), 0,
+                new PiecesContainer(List.of(
+                        new DesertPyramidPiece(RandomSource.create(1L), 0, 0))));
+
+        assertTrue(NativeStructureVegetationClearer.shouldProcessTarget(
+                new NativeStructureVegetationClearer.VegetationTarget(start, false)));
+        assertFalse(NativeStructureVegetationClearer.shouldProcessTarget(
+                new NativeStructureVegetationClearer.VegetationTarget(
+                        StructureStart.INVALID_START, true)));
+    }
+
     @Test
     public void surfaceStructuresPreserveVegetationUnlessConfigured() {
         assertFalse(NativeStructureVegetationClearer.shouldClearEntireVegetationFootprint(

adapters/bukkit/plugin/build.gradle

@@ -58,6 +58,7 @@ tasks.named('jar', Jar).configure {
 tasks.named('test').configure {
     systemProperty('iris.commandFindSource', file('src/main/java/art/arcane/iris/core/commands/CommandFind.java').absolutePath)
     systemProperty('iris.commandStructureSource', file('src/main/java/art/arcane/iris/core/commands/CommandStructure.java').absolutePath)
+    systemProperty('iris.commandIrisSource', file('src/main/java/art/arcane/iris/core/commands/CommandIris.java').absolutePath)
     systemProperty('iris.bukkitChunkGeneratorSource', rootProject.file('core/src/main/java/art/arcane/iris/engine/platform/BukkitChunkGenerator.java').absolutePath)
     systemProperty('iris.pregeneratorJobSource', rootProject.file('core/src/main/java/art/arcane/iris/core/gui/PregeneratorJob.java').absolutePath)
     systemProperty('iris.bukkitEnginePlatformHooksSource', file('src/main/java/art/arcane/iris/core/runtime/BukkitEnginePlatformHooks.java').absolutePath)

adapters/bukkit/plugin/src/main/java/art/arcane/iris/Iris.java

@@ -36,6 +36,7 @@ import art.arcane.iris.core.datapack.DatapackIngestService;
 import art.arcane.iris.core.lifecycle.PaperLibBootstrap;
 import art.arcane.iris.core.lifecycle.WorldLifecycleService;
 import art.arcane.iris.core.runtime.BukkitEnginePlatformHooks;
+import art.arcane.iris.core.runtime.WorldDeletionQueue;
 import art.arcane.iris.core.runtime.WorldRuntimeControlService;
 import art.arcane.iris.api.terrain.IrisTerrainService;
 import art.arcane.iris.core.link.IrisPapiInstaller;
@@ -571,7 +572,7 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         IrisServices.register(EnginePlatformHooks.class, new BukkitEnginePlatformHooks());
         IrisServices.register(EngineWorldManagerProvider.class,
                 (EngineWorldManagerProvider) IrisWorldManager::new);
-        IrisServices.register(art.arcane.iris.core.runtime.WorldDeletionQueue.class, (art.arcane.iris.core.runtime.WorldDeletionQueue) pendingWorldDeletes::queueWorldDeletionOnStartup);
+        IrisServices.register(WorldDeletionQueue.class, pendingWorldDeletes);
         SettingsHotloadWatch watch = new SettingsHotloadWatch(getDataFile("settings.json"));
         settingsHotloadWatch = watch;
         configHotloadEngine = new ConfigHotloadEngine(

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/BukkitWorldReconciler.java

@@ -19,77 +19,381 @@
 package art.arcane.iris.core;
 
 import art.arcane.iris.Iris;
-import art.arcane.iris.core.lifecycle.WorldLifecycleService;
+import art.arcane.iris.core.lifecycle.BukkitWorldConfiguration;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
 import art.arcane.iris.core.nms.INMS;
+import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.platform.bukkit.BukkitEnvironment;
 import art.arcane.iris.util.common.format.C;
-import art.arcane.iris.util.common.scheduling.J;
+import art.arcane.iris.util.common.misc.ServerProperties;
 import art.arcane.volmlib.util.bukkit.WorldIdentity;
-import art.arcane.volmlib.util.collection.KList;
 import org.bukkit.NamespacedKey;
+import org.bukkit.World;
 import org.bukkit.WorldCreator;
 import org.bukkit.generator.ChunkGenerator;
 
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Predicate;
+import java.util.stream.Stream;
 
-/**
- * Loads Iris worlds that are staged in bukkit.yml but not yet present on the server.
- */
 public final class BukkitWorldReconciler {
-    private final Iris plugin;
+    private static final long WORLD_CREATE_TIMEOUT_SECONDS = 120L;
+
+    private final Backend backend;
+    private final LifecycleOperationCoordinator coordinator;
 
     public BukkitWorldReconciler(Iris plugin) {
-        this.plugin = plugin;
+        this(new BukkitBackend(plugin), LifecycleOperationCoordinator.get());
     }
 
-    public void checkForBukkitWorlds(Predicate<String> filter) {
+    BukkitWorldReconciler(Backend backend, LifecycleOperationCoordinator coordinator) {
+        this.backend = Objects.requireNonNull(backend, "backend");
+        this.coordinator = Objects.requireNonNull(coordinator, "coordinator");
+    }
+
+    public CompletableFuture<LoadResult> loadWorld(
+            File configurationFile,
+            String worldName
+    ) {
+        NamespacedKey worldKey;
         try {
-            KList<String> deferredStartupWorlds = new KList<>();
-            IrisWorlds.readBukkitWorlds().forEach((s, generator) -> {
-                try {
-                    NamespacedKey worldKey = IrisWorldStorage.keyFromName(s);
-                    if (WorldIdentity.resolve(worldKey).isPresent() || !filter.test(s)) return;
-
-                    Iris.info("Loading World: %s | Generator: %s", s, generator);
-                    ChunkGenerator gen = plugin.getDefaultWorldGenerator(s, generator);
-                    IrisDimension dim = IrisWorldGeneratorResolver.loadDimension(s, generator);
-                    assert dim != null && gen != null;
-
-                    Iris.info(C.LIGHT_PURPLE + "Preparing Spawn for " + s + "' using Iris:" + generator + "...");
-                    WorldCreator c = WorldCreatorCompat.ofKey(worldKey)
-                            .generator(gen)
-                            .environment(BukkitEnvironment.from(dim.getEnvironment()));
-                    Long stagedSeed = IrisWorlds.readBukkitWorldSeed(s);
-                    if (stagedSeed != null) {
-                        c.seed(stagedSeed);
-                    }
-                    INMS.get().createWorld(c);
-                    Iris.info(C.LIGHT_PURPLE + "Loaded " + s + "!");
-                } catch (Throwable e) {
-                    if (containsCreateWorldUnsupportedOperation(e)) {
-                        if (J.isFolia()) {
-                            if (!deferredStartupWorlds.contains(s)) {
-                                deferredStartupWorlds.add(s);
-                            }
-                            return;
-                        }
-                        Iris.error("Failed to load world " + s + "!");
-                        Iris.error("This server denied Bukkit.createWorld for \"" + s + "\" at the current startup phase.");
-                        Iris.error("Ensure Iris is loaded at STARTUP and restart after staging worlds in bukkit.yml.");
-                        Iris.reportError("Failed to load staged startup world \"" + s + "\".", e);
-                        return;
-                    }
-                    Iris.reportError("Failed to load startup world \"" + s + "\".", e);
-                }
-            });
-            if (!deferredStartupWorlds.isEmpty()) {
-                Iris.warn("Staged Iris worlds could not load on Folia: %s", String.join(", ", deferredStartupWorlds));
-                Iris.warn("Bukkit.createWorld is unsupported on this server and the Iris runtime world backend is unavailable (%s).", WorldLifecycleService.get().capabilities().paperLikeResolution());
-            }
-        } catch (Throwable e) {
-            Iris.reportError("Failed while loading startup Iris worlds.", e);
+            worldKey = IrisWorldStorage.managedKeyFromName(worldName);
+        } catch (Throwable failure) {
+            return CompletableFuture.completedFuture(LoadResult.validationFailure(worldName, failure));
         }
+
+        LifecycleOperationCoordinator.Lease lease;
+        try {
+            lease = acquireWorldLoad(worldKey);
+        } catch (LifecycleOperationCoordinator.BusyException failure) {
+            return CompletableFuture.completedFuture(LoadResult.busy(worldKey, failure));
+        }
+
+        DimensionResolution dimensionResolution;
+        Long configuredSeed;
+        try {
+            dimensionResolution = backend.resolveDimension(worldKey);
+            configuredSeed = dimensionResolution.succeeded()
+                    ? backend.configuredSeed(IrisWorldStorage.logicalName(worldKey))
+                    : null;
+        } catch (Throwable failure) {
+            dimensionResolution = DimensionResolution.failed(failure);
+            configuredSeed = null;
+        }
+        if (!dimensionResolution.succeeded()) {
+            lease.close();
+            return CompletableFuture.completedFuture(LoadResult.dimensionFailure(
+                    worldKey,
+                    dimensionResolution.failure()));
+        }
+        return loadWithLease(
+                configurationFile,
+                worldKey,
+                dimensionResolution.dimension(),
+                configuredSeed,
+                lease);
+    }
+
+    public CompletableFuture<BatchResult> checkForBukkitWorlds(Predicate<String> filter) {
+        Predicate<String> requiredFilter = Objects.requireNonNull(filter, "filter");
+        Map<String, String> configuredWorlds;
+        try {
+            configuredWorlds = backend.configuredWorlds();
+        } catch (Throwable failure) {
+            Iris.reportError("Failed while reading staged Bukkit worlds.", failure);
+            return CompletableFuture.completedFuture(new BatchResult(List.of(), failure));
+        }
+
+        CompletableFuture<List<LoadResult>> chain = CompletableFuture.completedFuture(new ArrayList<>());
+        for (Map.Entry<String, String> entry : configuredWorlds.entrySet()) {
+            String worldName = entry.getKey();
+            boolean selected;
+            try {
+                selected = requiredFilter.test(worldName);
+            } catch (Throwable failure) {
+                Iris.reportError("Failed while filtering staged Bukkit world \"" + worldName + "\".", failure);
+                return CompletableFuture.completedFuture(new BatchResult(List.of(), failure));
+            }
+            if (!selected) {
+                continue;
+            }
+            NamespacedKey worldKey;
+            try {
+                worldKey = IrisWorldStorage.keyFromName(worldName);
+            } catch (Throwable failure) {
+                chain = chain.thenApply(results -> {
+                    results.add(LoadResult.validationFailure(worldName, failure));
+                    return results;
+                });
+                continue;
+            }
+            String dimension = entry.getValue();
+            Long seed;
+            try {
+                seed = backend.configuredSeed(worldName);
+            } catch (Throwable failure) {
+                chain = chain.thenApply(results -> {
+                    results.add(LoadResult.configurationFailure(worldKey, failure));
+                    return results;
+                });
+                continue;
+            }
+            chain = chain.thenCompose(results -> loadConfiguredWorld(
+                            ServerProperties.BUKKIT_YML,
+                            worldKey,
+                            dimension,
+                            seed)
+                    .thenApply(result -> {
+                        results.add(result);
+                        return results;
+                    }));
+        }
+
+        return chain.thenApply(results -> {
+            BatchResult batchResult = new BatchResult(results, null);
+            reportBatch(batchResult);
+            return batchResult;
+        });
+    }
+
+    private CompletableFuture<LoadResult> loadConfiguredWorld(
+            File configurationFile,
+            NamespacedKey worldKey,
+            String dimension,
+            Long seed
+    ) {
+        LifecycleOperationCoordinator.Lease lease;
+        try {
+            lease = acquireWorldLoad(worldKey);
+        } catch (LifecycleOperationCoordinator.BusyException failure) {
+            return CompletableFuture.completedFuture(LoadResult.busy(worldKey, failure));
+        }
+
+        return loadWithLease(configurationFile, worldKey, dimension, seed, lease);
+    }
+
+    private LifecycleOperationCoordinator.Lease acquireWorldLoad(NamespacedKey worldKey) {
+        return coordinator.acquire(
+                LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                LifecycleOperationCoordinator.OperationKind.WORLD_LOAD,
+                worldKey.toString());
+    }
+
+    private CompletableFuture<LoadResult> loadWithLease(
+            File configurationFile,
+            NamespacedKey worldKey,
+            String dimension,
+            Long seed,
+            LifecycleOperationCoordinator.Lease lease
+    ) {
+
+        BukkitWorldConfiguration.Registration registration;
+        String worldName = IrisWorldStorage.logicalName(worldKey);
+        try {
+            registration = BukkitWorldConfiguration.register(
+                    configurationFile,
+                    worldName,
+                    dimension,
+                    seed);
+        } catch (Throwable failure) {
+            lease.close();
+            return CompletableFuture.completedFuture(LoadResult.configurationFailure(worldKey, failure));
+        }
+
+        CompletableFuture<ReconciliationResult> reconciliation;
+        try {
+            reconciliation = reconcile(worldKey, dimension, seed);
+        } catch (Throwable failure) {
+            reconciliation = CompletableFuture.completedFuture(ReconciliationResult.createFailure(worldKey, failure));
+        }
+
+        return reconciliation.handle((result, failure) -> {
+                    ReconciliationResult settled = failure == null
+                            ? result
+                            : ReconciliationResult.createFailure(worldKey, unwrap(failure));
+                    if (settled == null) {
+                        settled = ReconciliationResult.createFailure(
+                                worldKey,
+                                new IllegalStateException("World reconciliation completed without a result."));
+                    }
+                    if (settled.succeeded()
+                            || settled.status() == ReconciliationStatus.RESTART_REQUIRED
+                            || registration != BukkitWorldConfiguration.Registration.CREATED) {
+                        return new LoadResult(settled, registration, false, true, null);
+                    }
+                    try {
+                        boolean rolledBack = BukkitWorldConfiguration.removeIfMatching(
+                                configurationFile,
+                                worldName,
+                                dimension,
+                                seed);
+                        return new LoadResult(settled, registration, true, rolledBack, null);
+                    } catch (Throwable rollbackFailure) {
+                        return new LoadResult(settled, registration, true, false, rollbackFailure);
+                    }
+                })
+                .whenComplete((result, failure) -> lease.close());
+    }
+
+    private CompletableFuture<ReconciliationResult> reconcile(
+            NamespacedKey worldKey,
+            String dimension,
+            Long seed
+    ) {
+        Optional<World> loaded = backend.loadedWorld(worldKey);
+        if (loaded.isPresent()) {
+            return CompletableFuture.completedFuture(verifyLoadedWorld(worldKey, loaded.get(), true));
+        }
+
+        CompletableFuture<World> created;
+        try {
+            created = Objects.requireNonNull(
+                    backend.createWorld(worldKey, dimension, seed),
+                    "World backend returned no creation future.");
+        } catch (Throwable failure) {
+            return CompletableFuture.completedFuture(classifyCreationFailure(worldKey, failure));
+        }
+
+        CompletableFuture<World> guardedCreation = guardCreateCompletion(
+                created,
+                worldKey,
+                TimeUnit.SECONDS.toMillis(WORLD_CREATE_TIMEOUT_SECONDS),
+                () -> ServerConfigurator.restart("World load timed out for \"" + worldKey + "\"."));
+        return guardedCreation.handle((createdWorld, failure) -> {
+            if (failure != null) {
+                return classifyCreationFailure(worldKey, unwrap(failure));
+            }
+            if (createdWorld == null) {
+                return ReconciliationResult.notLoaded(worldKey);
+            }
+
+            NamespacedKey createdKey;
+            try {
+                createdKey = WorldIdentity.key(createdWorld);
+            } catch (Throwable identityFailure) {
+                return ReconciliationResult.createFailure(worldKey, identityFailure);
+            }
+            if (!worldKey.equals(createdKey)) {
+                return ReconciliationResult.identityMismatch(worldKey, createdWorld, createdKey);
+            }
+
+            Optional<World> resolved = backend.loadedWorld(worldKey);
+            if (resolved.isEmpty()) {
+                return ReconciliationResult.notLoaded(worldKey);
+            }
+            return verifyLoadedWorld(worldKey, resolved.get(), false);
+        });
+    }
+
+    private ReconciliationResult verifyLoadedWorld(NamespacedKey worldKey, World loadedWorld, boolean alreadyLoaded) {
+        NamespacedKey loadedKey;
+        try {
+            loadedKey = WorldIdentity.key(loadedWorld);
+        } catch (Throwable identityFailure) {
+            return ReconciliationResult.createFailure(worldKey, identityFailure);
+        }
+        if (!worldKey.equals(loadedKey)) {
+            return ReconciliationResult.identityMismatch(worldKey, loadedWorld, loadedKey);
+        }
+        if (!backend.isIrisWorld(loadedWorld)) {
+            return ReconciliationResult.identityConflict(worldKey, loadedWorld);
+        }
+        return alreadyLoaded
+                ? ReconciliationResult.alreadyLoaded(worldKey, loadedWorld)
+                : ReconciliationResult.loaded(worldKey, loadedWorld);
+    }
+
+    private static ReconciliationResult classifyCreationFailure(NamespacedKey worldKey, Throwable failure) {
+        Throwable cause = unwrap(failure);
+        if (cause instanceof TimeoutException || containsCreateWorldUnsupportedOperation(cause)) {
+            return ReconciliationResult.restartRequired(worldKey, cause);
+        }
+        return ReconciliationResult.createFailure(worldKey, cause);
+    }
+
+    static CompletableFuture<World> guardCreateCompletion(
+            CompletableFuture<World> source,
+            NamespacedKey worldKey,
+            long timeoutMillis,
+            Runnable timeoutAction
+    ) {
+        Objects.requireNonNull(source, "source");
+        Objects.requireNonNull(worldKey, "worldKey");
+        Objects.requireNonNull(timeoutAction, "timeoutAction");
+        if (timeoutMillis < 1L) {
+            throw new IllegalArgumentException("timeoutMillis must be positive");
+        }
+
+        CompletableFuture<World> guarded = new CompletableFuture<>();
+        AtomicBoolean settled = new AtomicBoolean(false);
+        source.whenComplete((world, throwable) -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            if (throwable == null) {
+                guarded.complete(world);
+            } else {
+                guarded.completeExceptionally(unwrap(throwable));
+            }
+        });
+        CompletableFuture.delayedExecutor(timeoutMillis, TimeUnit.MILLISECONDS).execute(() -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            TimeoutException timeout = new TimeoutException(
+                    "World load did not settle within " + timeoutMillis + " milliseconds for \""
+                            + worldKey + "\".");
+            try {
+                timeoutAction.run();
+            } catch (Throwable failure) {
+                timeout.addSuppressed(failure);
+            }
+            guarded.completeExceptionally(timeout);
+        });
+        return guarded;
+    }
+
+    private static void reportBatch(BatchResult batchResult) {
+        for (LoadResult result : batchResult.results()) {
+            if (result.succeeded()) {
+                Iris.info(C.LIGHT_PURPLE + result.message());
+                continue;
+            }
+            if (result.status() == ReconciliationStatus.BUSY) {
+                Iris.warn(result.message());
+                continue;
+            }
+            Iris.error(result.message());
+            Throwable failure = result.failure();
+            if (failure != null) {
+                Iris.reportError("Failed to reconcile staged world \"" + result.worldKey() + "\".", failure);
+            }
+        }
+    }
+
+    private static Throwable unwrap(Throwable failure) {
+        Throwable current = failure;
+        while (current instanceof CompletionException && current.getCause() != null) {
+            current = current.getCause();
+        }
+        return current;
     }
 
     private static boolean containsCreateWorldUnsupportedOperation(Throwable throwable) {
@@ -107,4 +411,321 @@ public final class BukkitWorldReconciler {
         }
         return false;
     }
+
+    interface Backend {
+        Map<String, String> configuredWorlds();
+
+        Long configuredSeed(String worldName);
+
+        Optional<World> loadedWorld(NamespacedKey worldKey);
+
+        CompletableFuture<World> createWorld(NamespacedKey worldKey, String dimension, Long seed);
+
+        boolean isIrisWorld(World world);
+
+        DimensionResolution resolveDimension(NamespacedKey worldKey);
+    }
+
+    public enum ReconciliationStatus {
+        LOADED,
+        ALREADY_LOADED,
+        BUSY,
+        INVALID_WORLD,
+        DIMENSION_UNRESOLVED,
+        CONFIGURATION_FAILED,
+        CREATE_FAILED,
+        RESTART_REQUIRED,
+        IDENTITY_MISMATCH,
+        IDENTITY_CONFLICT,
+        NOT_LOADED
+    }
+
+    public record ReconciliationResult(
+            ReconciliationStatus status,
+            NamespacedKey worldKey,
+            World world,
+            Throwable failure,
+            String message
+    ) {
+        public ReconciliationResult {
+            Objects.requireNonNull(status, "status");
+            Objects.requireNonNull(message, "message");
+        }
+
+        public boolean succeeded() {
+            return status == ReconciliationStatus.LOADED || status == ReconciliationStatus.ALREADY_LOADED;
+        }
+
+        private static ReconciliationResult loaded(NamespacedKey worldKey, World world) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.LOADED,
+                    worldKey,
+                    world,
+                    null,
+                    "Loaded Iris world \"" + worldKey + "\".");
+        }
+
+        private static ReconciliationResult alreadyLoaded(NamespacedKey worldKey, World world) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.ALREADY_LOADED,
+                    worldKey,
+                    world,
+                    null,
+                    "Iris world \"" + worldKey + "\" is already loaded.");
+        }
+
+        private static ReconciliationResult createFailure(NamespacedKey worldKey, Throwable failure) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.CREATE_FAILED,
+                    worldKey,
+                    null,
+                    failure,
+                    "Failed to create Iris world \"" + worldKey + "\": " + failure.getMessage());
+        }
+
+        private static ReconciliationResult restartRequired(NamespacedKey worldKey, Throwable failure) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.RESTART_REQUIRED,
+                    worldKey,
+                    null,
+                    failure,
+                    "The server cannot load exact Iris world \"" + worldKey + "\" at this runtime phase.");
+        }
+
+        private static ReconciliationResult identityMismatch(
+                NamespacedKey worldKey,
+                World world,
+                NamespacedKey actualKey
+        ) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.IDENTITY_MISMATCH,
+                    worldKey,
+                    world,
+                    null,
+                    "World creation returned \"" + actualKey + "\" instead of \"" + worldKey + "\".");
+        }
+
+        private static ReconciliationResult identityConflict(NamespacedKey worldKey, World world) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.IDENTITY_CONFLICT,
+                    worldKey,
+                    world,
+                    null,
+                    "World \"" + worldKey + "\" is loaded, but it is not an Iris world.");
+        }
+
+        private static ReconciliationResult notLoaded(NamespacedKey worldKey) {
+            return new ReconciliationResult(
+                    ReconciliationStatus.NOT_LOADED,
+                    worldKey,
+                    null,
+                    null,
+                    "World creation completed without loading exact Iris world \"" + worldKey + "\".");
+        }
+    }
+
+    public record LoadResult(
+            ReconciliationResult reconciliation,
+            BukkitWorldConfiguration.Registration registration,
+            boolean rollbackAttempted,
+            boolean rollbackSucceeded,
+            Throwable rollbackFailure
+    ) {
+        public LoadResult {
+            Objects.requireNonNull(reconciliation, "reconciliation");
+        }
+
+        public boolean succeeded() {
+            return reconciliation.succeeded() && rollbackFailure == null;
+        }
+
+        public ReconciliationStatus status() {
+            return reconciliation.status();
+        }
+
+        public NamespacedKey worldKey() {
+            return reconciliation.worldKey();
+        }
+
+        public World world() {
+            return reconciliation.world();
+        }
+
+        public Throwable failure() {
+            return rollbackFailure == null ? reconciliation.failure() : rollbackFailure;
+        }
+
+        public String message() {
+            if (rollbackFailure != null) {
+                return reconciliation.message() + " Failed to roll back bukkit.yml: " + rollbackFailure.getMessage();
+            }
+            if (rollbackAttempted && rollbackSucceeded) {
+                return reconciliation.message() + " The new bukkit.yml entry was rolled back.";
+            }
+            if (rollbackAttempted && !rollbackSucceeded) {
+                return reconciliation.message() + " The new bukkit.yml entry was no longer an exact match and was not modified.";
+            }
+            return reconciliation.message();
+        }
+
+        private static LoadResult validationFailure(String worldName, Throwable failure) {
+            ReconciliationResult reconciliation = new ReconciliationResult(
+                    ReconciliationStatus.INVALID_WORLD,
+                    null,
+                    null,
+                    failure,
+                    "Invalid Iris world identifier \"" + worldName + "\": " + failure.getMessage());
+            return new LoadResult(reconciliation, null, false, true, null);
+        }
+
+        private static LoadResult busy(NamespacedKey worldKey, LifecycleOperationCoordinator.BusyException failure) {
+            ReconciliationResult reconciliation = new ReconciliationResult(
+                    ReconciliationStatus.BUSY,
+                    worldKey,
+                    null,
+                    failure,
+                    failure.getMessage());
+            return new LoadResult(reconciliation, null, false, true, null);
+        }
+
+        private static LoadResult configurationFailure(NamespacedKey worldKey, Throwable failure) {
+            ReconciliationResult reconciliation = new ReconciliationResult(
+                    ReconciliationStatus.CONFIGURATION_FAILED,
+                    worldKey,
+                    null,
+                    failure,
+                    "Failed to register Iris world \"" + worldKey + "\" in bukkit.yml: " + failure.getMessage());
+            return new LoadResult(reconciliation, null, false, true, null);
+        }
+
+        private static LoadResult dimensionFailure(NamespacedKey worldKey, Throwable failure) {
+            ReconciliationResult reconciliation = new ReconciliationResult(
+                    ReconciliationStatus.DIMENSION_UNRESOLVED,
+                    worldKey,
+                    null,
+                    failure,
+                    "Could not determine one Iris dimension for world \"" + worldKey + "\": " + failure.getMessage());
+            return new LoadResult(reconciliation, null, false, true, null);
+        }
+    }
+
+    record DimensionResolution(String dimension, Throwable failure) {
+        DimensionResolution {
+            if ((dimension == null) == (failure == null)) {
+                throw new IllegalArgumentException("Dimension resolution must contain exactly one outcome.");
+            }
+        }
+
+        static DimensionResolution resolved(String dimension) {
+            return new DimensionResolution(Objects.requireNonNull(dimension, "dimension"), null);
+        }
+
+        static DimensionResolution failed(Throwable failure) {
+            return new DimensionResolution(null, Objects.requireNonNull(failure, "failure"));
+        }
+
+        boolean succeeded() {
+            return dimension != null;
+        }
+    }
+
+    public record BatchResult(List<LoadResult> results, Throwable failure) {
+        public BatchResult {
+            results = List.copyOf(Objects.requireNonNull(results, "results"));
+        }
+
+        public boolean succeeded() {
+            return failure == null && results.stream().allMatch(LoadResult::succeeded);
+        }
+    }
+
+    private static final class BukkitBackend implements Backend {
+        private final Iris plugin;
+
+        private BukkitBackend(Iris plugin) {
+            this.plugin = Objects.requireNonNull(plugin, "plugin");
+        }
+
+        @Override
+        public Map<String, String> configuredWorlds() {
+            return new LinkedHashMap<>(IrisWorlds.readBukkitWorlds());
+        }
+
+        @Override
+        public Long configuredSeed(String worldName) {
+            return IrisWorlds.readBukkitWorldSeed(worldName);
+        }
+
+        @Override
+        public Optional<World> loadedWorld(NamespacedKey worldKey) {
+            return WorldIdentity.resolve(worldKey);
+        }
+
+        @Override
+        public CompletableFuture<World> createWorld(NamespacedKey worldKey, String dimension, Long seed) {
+            try {
+                String worldName = IrisWorldStorage.logicalName(worldKey);
+                Iris.info("Loading World: %s | Generator: %s", worldName, dimension);
+                ChunkGenerator generator = plugin.getDefaultWorldGenerator(worldName, dimension);
+                IrisDimension irisDimension = IrisWorldGeneratorResolver.loadDimension(worldName, dimension);
+                if (generator == null || irisDimension == null) {
+                    throw new IllegalStateException("Could not resolve the Iris generator or dimension \"" + dimension + "\".");
+                }
+
+                Iris.info(C.LIGHT_PURPLE + "Preparing Spawn for " + worldName + " using Iris:" + dimension + "...");
+                WorldCreator creator = WorldCreatorCompat.ofKey(worldKey)
+                        .generator(generator)
+                        .environment(BukkitEnvironment.from(irisDimension.getEnvironment()));
+                if (seed != null) {
+                    creator.seed(seed);
+                }
+                return INMS.get().createWorldAsync(creator);
+            } catch (Throwable failure) {
+                return CompletableFuture.failedFuture(failure);
+            }
+        }
+
+        @Override
+        public boolean isIrisWorld(World world) {
+            return IrisToolbelt.isIrisWorld(world);
+        }
+
+        @Override
+        public DimensionResolution resolveDimension(NamespacedKey worldKey) {
+            File dimensionsDirectory = new File(IrisWorldStorage.packRoot(worldKey), "dimensions");
+            if (!dimensionsDirectory.isDirectory()) {
+                return DimensionResolution.failed(new IllegalStateException("The world has no Iris dimensions directory."));
+            }
+
+            List<String> dimensions = new ArrayList<>();
+            Path dimensionsRoot = dimensionsDirectory.toPath().toAbsolutePath().normalize();
+            try (Stream<Path> paths = Files.walk(dimensionsRoot)) {
+                paths.filter(path -> Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS))
+                        .filter(path -> path.getFileName().toString().endsWith(".json"))
+                        .forEach(path -> {
+                            String relative = dimensionsRoot.relativize(path).toString().replace(File.separatorChar, '/');
+                            dimensions.add(relative.substring(0, relative.length() - 5));
+                        });
+            } catch (IOException failure) {
+                return DimensionResolution.failed(new IllegalStateException(
+                        "The Iris dimensions directory could not be read.",
+                        failure));
+            }
+            Collections.sort(dimensions);
+
+            String registeredDimension = IrisWorlds.get().getWorlds().get(worldKey.toString());
+            if (registeredDimension != null && dimensions.contains(registeredDimension)) {
+                return DimensionResolution.resolved(registeredDimension);
+            }
+            if (dimensions.size() == 1) {
+                return DimensionResolution.resolved(dimensions.getFirst());
+            }
+            if (dimensions.isEmpty()) {
+                return DimensionResolution.failed(new IllegalStateException("No dimension definitions were found."));
+            }
+            return DimensionResolution.failed(new IllegalStateException(
+                    "Multiple dimension definitions were found without an exact registered dimension: "
+                            + String.join(", ", dimensions)));
+        }
+    }
 }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/IrisWorldGeneratorResolver.java

@@ -23,6 +23,7 @@ import art.arcane.iris.core.lifecycle.WorldLifecycleStaging;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.pack.BrokenPackException;
 import art.arcane.iris.core.pack.PackDownloader;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.pack.PackValidationRegistry;
 import art.arcane.iris.core.pack.PackValidationResult;
 import art.arcane.iris.core.pack.PackValidator;
@@ -33,7 +34,6 @@ import art.arcane.iris.engine.object.IrisWorld;
 import art.arcane.iris.engine.platform.BukkitChunkGenerator;
 import art.arcane.iris.util.common.plugin.VolmitPlugin;
 import art.arcane.iris.util.common.plugin.VolmitSender;
-import art.arcane.volmlib.util.io.IO;
 import lombok.NonNull;
 import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
@@ -42,6 +42,7 @@ import org.bukkit.generator.ChunkGenerator;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
+import java.util.List;
 import java.util.function.Supplier;
 
 /**
@@ -57,15 +58,12 @@ public final class IrisWorldGeneratorResolver {
 
     public void validateAllPacks() {
         File packsRoot = plugin.getDataFolder("packs");
-        File[] packDirs = packsRoot.listFiles(File::isDirectory);
-        if (packDirs == null || packDirs.length == 0) {
+        List<File> packDirs = PackDirectoryResolver.listVisiblePackDirectories(packsRoot);
+        PackValidationRegistry.clear();
+        if (packDirs.isEmpty()) {
             return;
         }
-        PackValidationRegistry.clear();
         for (File packDir : packDirs) {
-            if (packDir.getName().contains(".importing-")) {
-                continue;
-            }
             try {
                 PackValidationResult result = PackValidator.validate(packDir);
                 PackValidationRegistry.publish(result);
@@ -167,16 +165,16 @@ public final class IrisWorldGeneratorResolver {
         Iris.debug("Generator Config: " + w.toString());
 
         File ff = new File(w.worldFolder(), "iris/pack");
-        File[] files = ff.listFiles();
-        if (files == null || files.length == 0)
-            IO.delete(ff);
-
-        if (!ff.exists()) {
-            ff.mkdirs();
-            dim = Iris.service(StudioSVC.class).installIntoWorld(Iris.getSender(), dim, w.worldFolder());
+        IrisDimension installedDimension = ff.isDirectory()
+                ? IrisData.get(ff).getDimensionLoader().load(dim.getLoadKey(), false)
+                : null;
+        if (installedDimension == null) {
+            dim = Iris.service(StudioSVC.class).replaceIntoWorld(Iris.getSender(), dim, w.worldFolder());
             if (dim == null) {
                 throw new IllegalStateException("Failed to install dimension pack for " + id);
             }
+        } else {
+            dim = installedDimension;
         }
 
         return new BukkitChunkGenerator(w, false, ff, dim.getLoadKey());

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/PendingWorldDeleteQueue.java

@@ -19,14 +19,11 @@
 package art.arcane.iris.core;
 
 import art.arcane.iris.Iris;
+import art.arcane.iris.core.runtime.WorldDeletionQueue;
 import art.arcane.iris.core.runtime.TransientWorldCleanupSupport;
 import art.arcane.iris.core.tools.IrisCreator;
-import art.arcane.iris.core.tools.IrisToolbelt;
-import art.arcane.iris.engine.platform.PlatformChunkGenerator;
-import art.arcane.iris.util.common.misc.ServerProperties;
 import art.arcane.iris.util.common.plugin.VolmitPlugin;
 import art.arcane.volmlib.util.bukkit.WorldIdentity;
-import art.arcane.volmlib.util.io.IO;
 import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
 import org.bukkit.World;
@@ -34,21 +31,38 @@ import org.jetbrains.annotations.Nullable;
 
 import java.io.BufferedReader;
 import java.io.File;
-import java.io.FileReader;
-import java.io.FileWriter;
 import java.io.IOException;
-import java.io.PrintWriter;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.UUID;
+import java.util.regex.Pattern;
 
-/**
- * Persistent queue of world folders that must be deleted on the next startup, plus the startup
- * drain that actually removes them.
- */
-public final class PendingWorldDeleteQueue {
+public final class PendingWorldDeleteQueue implements WorldDeletionQueue {
     private static final String PENDING_WORLD_DELETE_FILE = "pending-world-deletes.txt";
+    private static final String EXACT_PREFIX = "exact:";
+    private static final Pattern SAFE_LOGICAL_NAME = Pattern.compile("^[a-z0-9_-]+$");
+    private static final Pattern QUARANTINE_NAME = Pattern.compile("^\\.iris-delete-[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$");
+    private static final Set<String> VANILLA_DIMENSION_ALIASES = Set.of("overworld", "the_nether", "the_end");
 
     private final VolmitPlugin plugin;
 
@@ -56,173 +70,413 @@ public final class PendingWorldDeleteQueue {
         this.plugin = plugin;
     }
 
-    public synchronized int queueWorldDeletionOnStartup(Collection<String> worldNames) throws IOException {
+    @Override
+    public synchronized int queueExactForStartupDeletion(Collection<String> worldNames) throws IOException {
+        return queueWorldDeletionOnStartup(worldNames, true);
+    }
+
+    @Override
+    public synchronized int queueFamilyForStartupDeletion(Collection<String> worldNames) throws IOException {
+        return queueWorldDeletionOnStartup(worldNames, false);
+    }
+
+    private int queueWorldDeletionOnStartup(Collection<String> worldNames, boolean exact) throws IOException {
         if (worldNames == null || worldNames.isEmpty()) {
             return 0;
         }
 
-        LinkedHashMap<String, String> queue = loadPendingWorldDeleteMap();
-        int before = queue.size();
-
+        File levelRoot = IrisWorldStorage.levelRoot();
+        ArrayList<String> normalizedNames = new ArrayList<>(worldNames.size());
         for (String worldName : worldNames) {
-            String normalized = normalizeWorldName(worldName);
+            String normalized = normalizeQueueEntry(worldName, levelRoot.getName());
             if (normalized == null) {
-                continue;
+                throw new IllegalArgumentException("Unsafe Iris world deletion target: " + worldName);
             }
-            queue.putIfAbsent(normalized.toLowerCase(Locale.ROOT), normalized);
+            normalizedNames.add(exact && !QUARANTINE_NAME.matcher(normalized).matches()
+                    ? EXACT_PREFIX + normalized
+                    : normalized);
+        }
+
+        File queueFile = plugin.getDataFile(PENDING_WORLD_DELETE_FILE);
+        LinkedHashMap<String, String> queue = loadPendingWorldDeleteMap(queueFile, levelRoot.getName());
+        int before = queue.size();
+        for (String normalized : normalizedNames) {
+            mergeQueueEntry(queue, normalized);
         }
 
         if (queue.size() != before) {
-            writePendingWorldDeleteMap(queue);
+            writePendingWorldDeleteMap(queueFile, queue);
         }
-
         return queue.size() - before;
     }
 
-    public void processPendingStartupWorldDeletes() {
+    public synchronized void processPendingStartupWorldDeletes() {
         try {
-            try {
-                int unregistered = IrisCreator.removeTransientStudioWorldsFromBukkitYml();
-                if (unregistered > 0) {
-                    Iris.info("Unregistered " + unregistered + " transient studio world(s) from bukkit.yml on startup.");
-                }
-            } catch (Throwable e) {
-                Iris.reportError("Failed to unregister transient studio worlds from bukkit.yml on startup.", e);
-            }
+            unregisterTransientStudioWorlds();
 
-            LinkedHashMap<String, String> queue = loadPendingWorldDeleteMap();
-            for (String transientStudioWorld : TransientWorldCleanupSupport.collectTransientStudioWorldNames(IrisWorldStorage.levelRoot())) {
-                queue.putIfAbsent(transientStudioWorld.toLowerCase(Locale.ROOT), transientStudioWorld);
+            File levelRoot = IrisWorldStorage.levelRoot();
+            File queueFile = plugin.getDataFile(PENDING_WORLD_DELETE_FILE);
+            LinkedHashMap<String, String> queue = loadPendingWorldDeleteMap(queueFile, levelRoot.getName());
+            for (String discoveredName : discoverStartupWorldNames(levelRoot)) {
+                mergeQueueEntry(queue, discoveredName);
             }
             if (queue.isEmpty()) {
+                if (queueFile.exists()) {
+                    writePendingWorldDeleteMap(queueFile, queue);
+                }
                 return;
             }
 
             LinkedHashMap<String, String> remaining = new LinkedHashMap<>();
             for (String worldName : queue.values()) {
-                if (worldName.equalsIgnoreCase(ServerProperties.LEVEL_NAME)) {
-                    Iris.warn("Skipping queued deletion for \"" + worldName + "\" because it is configured as level-name.");
-                    continue;
-                }
-
-                NamespacedKey worldKey = IrisWorldStorage.keyFromName(worldName);
-                World loaded = WorldIdentity.resolve(worldKey).orElse(null);
-                if (loaded != null) {
-                    if (TransientWorldCleanupSupport.isTransientStudioWorldName(worldName)) {
-                        try {
-                            PlatformChunkGenerator generator = IrisToolbelt.access(loaded);
-                            if (generator != null) {
-                                generator.close();
-                            }
-                            IrisToolbelt.evacuate(loaded);
-                            Bukkit.unloadWorld(loaded, false);
-                            Iris.info("Unloaded leftover studio world \"" + worldName + "\" for deletion.");
-                        } catch (Throwable e) {
-                            Iris.reportError("Failed to unload leftover studio world \"" + worldName + "\".", e);
-                        }
-
-                        if (WorldIdentity.resolve(worldKey).isPresent()) {
-                            Iris.warn("Studio world \"" + worldName + "\" is still loaded after unload; will retry next startup.");
-                            remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
-                            continue;
-                        }
-                    } else {
-                        Iris.warn("Skipping queued deletion for \"" + worldName + "\" because it is currently loaded.");
-                        remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
-                        continue;
-                    }
-                }
-
-                boolean foundAny = false;
-                boolean deletedAll = true;
-                for (String familyWorldName : TransientWorldCleanupSupport.worldFamilyNames(worldName)) {
-                    File worldFolder = IrisWorldStorage.dimensionRoot(familyWorldName);
-                    if (!worldFolder.exists()) {
-                        continue;
-                    }
-
-                    foundAny = true;
-                    IO.delete(worldFolder);
-                    if (worldFolder.exists()) {
-                        deletedAll = false;
-                        Iris.warn("Failed to delete queued world folder \"" + familyWorldName + "\". Retrying on next startup.");
-                    } else {
-                        Iris.info("Deleted queued world folder \"" + familyWorldName + "\".");
-                    }
-                }
-
-                if (!foundAny) {
-                    Iris.info("Queued world deletion skipped for \"" + worldName + "\" (folder missing).");
-                    continue;
-                }
-
-                if (!deletedAll) {
-                    remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
-                    continue;
-                }
-            }
-
-            writePendingWorldDeleteMap(remaining);
-        } catch (Throwable e) {
-            Iris.error("Failed to process queued startup world deletions.");
-            Iris.reportError(e);
-            e.printStackTrace();
-        }
-    }
-
-    private LinkedHashMap<String, String> loadPendingWorldDeleteMap() throws IOException {
-        LinkedHashMap<String, String> queue = new LinkedHashMap<>();
-        File queueFile = plugin.getDataFile(PENDING_WORLD_DELETE_FILE);
-        if (!queueFile.exists()) {
-            return queue;
-        }
-
-        try (BufferedReader reader = new BufferedReader(new FileReader(queueFile))) {
-            String line;
-            while ((line = reader.readLine()) != null) {
-                String normalized = normalizeWorldName(line);
-                if (normalized == null) {
-                    continue;
-                }
-                queue.putIfAbsent(normalized.toLowerCase(Locale.ROOT), normalized);
-            }
-        }
-
-        return queue;
-    }
-
-    private void writePendingWorldDeleteMap(Map<String, String> queue) throws IOException {
-        File queueFile = plugin.getDataFile(PENDING_WORLD_DELETE_FILE);
-        if (queue.isEmpty()) {
-            if (queueFile.exists()) {
-                IO.delete(queueFile);
-            }
-            return;
-        }
-
-        File parent = queueFile.getParentFile();
-        if (parent != null && !parent.exists() && !parent.mkdirs()) {
-            throw new IOException("Failed to create queue directory: " + parent.getAbsolutePath());
-        }
-
-        try (PrintWriter writer = new PrintWriter(new FileWriter(queueFile))) {
-            for (String worldName : queue.values()) {
-                writer.println(worldName);
+                processEntry(levelRoot, worldName, remaining);
             }
+            writePendingWorldDeleteMap(queueFile, remaining);
+        } catch (Throwable failure) {
+            Iris.reportError("Failed to process queued startup world deletions.", failure);
         }
     }
 
     @Nullable
-    private static String normalizeWorldName(String worldName) {
+    static String normalizeQueueEntry(String worldName, String levelName) {
         if (worldName == null) {
             return null;
         }
 
-        String trimmed = worldName.trim();
-        if (trimmed.isEmpty()) {
+        String candidate = worldName.trim();
+        if (candidate.isEmpty()) {
+            return null;
+        }
+        if (QUARANTINE_NAME.matcher(candidate).matches()) {
+            return candidate;
+        }
+
+        String logicalName = candidate.startsWith("iris:") ? candidate.substring("iris:".length()) : candidate;
+        if (!SAFE_LOGICAL_NAME.matcher(logicalName).matches()) {
+            return null;
+        }
+        String normalizedLevelName = Objects.requireNonNull(levelName, "levelName").trim().toLowerCase(Locale.ROOT);
+        if (VANILLA_DIMENSION_ALIASES.contains(logicalName)
+                || logicalName.equals(normalizedLevelName)
+                || logicalName.equals(normalizedLevelName + "_nether")
+                || logicalName.equals(normalizedLevelName + "_the_end")) {
             return null;
         }
 
-        return trimmed;
+        try {
+            NamespacedKey key = IrisWorldStorage.managedKeyFromName(candidate, normalizedLevelName);
+            return key.getKey().equals(logicalName) ? logicalName : null;
+        } catch (IllegalArgumentException failure) {
+            return null;
+        }
+    }
+
+    static LinkedHashMap<String, String> loadPendingWorldDeleteMap(File queueFile, String levelName) throws IOException {
+        LinkedHashMap<String, String> queue = new LinkedHashMap<>();
+        Path queuePath = Objects.requireNonNull(queueFile, "queueFile").toPath();
+        if (!Files.exists(queuePath, LinkOption.NOFOLLOW_LINKS)) {
+            return queue;
+        }
+
+        try (BufferedReader reader = Files.newBufferedReader(queuePath, StandardCharsets.UTF_8)) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                String normalized = normalizeStoredQueueEntry(line, levelName);
+                if (normalized != null) {
+                    mergeQueueEntry(queue, normalized);
+                }
+            }
+        }
+        return queue;
+    }
+
+    @Nullable
+    private static String normalizeStoredQueueEntry(String storedEntry, String levelName) {
+        if (storedEntry == null) {
+            return null;
+        }
+        String candidate = storedEntry.trim();
+        boolean exact = candidate.startsWith(EXACT_PREFIX);
+        String rawName = exact ? candidate.substring(EXACT_PREFIX.length()) : candidate;
+        String normalized = normalizeQueueEntry(rawName, levelName);
+        if (normalized == null || QUARANTINE_NAME.matcher(normalized).matches()) {
+            return normalized;
+        }
+        return exact ? EXACT_PREFIX + normalized : normalized;
+    }
+
+    private static void mergeQueueEntry(Map<String, String> queue, String storedEntry) {
+        String logicalKey = storedEntry.startsWith(EXACT_PREFIX)
+                ? storedEntry.substring(EXACT_PREFIX.length())
+                : storedEntry;
+        String key = logicalKey.toLowerCase(Locale.ROOT);
+        String existing = queue.get(key);
+        if (existing == null || (existing.startsWith(EXACT_PREFIX) && !storedEntry.startsWith(EXACT_PREFIX))) {
+            queue.put(key, storedEntry);
+        }
+    }
+
+    static void writePendingWorldDeleteMap(File queueFile, Map<String, String> queue) throws IOException {
+        Path queuePath = Objects.requireNonNull(queueFile, "queueFile").toPath().toAbsolutePath().normalize();
+        Path parent = queuePath.getParent();
+        if (parent == null) {
+            throw new IOException("Queue file has no parent directory: " + queuePath);
+        }
+        Files.createDirectories(parent);
+
+        StringBuilder content = new StringBuilder();
+        for (String worldName : Objects.requireNonNull(queue, "queue").values()) {
+            content.append(worldName).append('\n');
+        }
+
+        Path temporary = parent.resolve(queuePath.getFileName() + ".tmp-" + UUID.randomUUID());
+        IOException failure = null;
+        try {
+            byte[] bytes = content.toString().getBytes(StandardCharsets.UTF_8);
+            try (FileChannel channel = FileChannel.open(
+                    temporary,
+                    StandardOpenOption.CREATE_NEW,
+                    StandardOpenOption.WRITE
+            )) {
+                ByteBuffer buffer = ByteBuffer.wrap(bytes);
+                while (buffer.hasRemaining()) {
+                    channel.write(buffer);
+                }
+                channel.force(true);
+            }
+
+            replaceQueueFile(temporary, queuePath);
+            forceDirectory(parent);
+        } catch (IOException writeFailure) {
+            failure = writeFailure;
+            throw writeFailure;
+        } finally {
+            try {
+                Files.deleteIfExists(temporary);
+            } catch (IOException cleanupFailure) {
+                if (failure != null) {
+                    failure.addSuppressed(cleanupFailure);
+                } else {
+                    throw cleanupFailure;
+                }
+            }
+        }
+    }
+
+    static LinkedHashSet<String> discoverStartupWorldNames(File levelRoot) throws IOException {
+        LinkedHashSet<String> worldNames = new LinkedHashSet<>();
+        Path root = Objects.requireNonNull(levelRoot, "levelRoot").toPath().toAbsolutePath().normalize();
+        Path dimensions = root.resolve("dimensions");
+        Path irisNamespace = dimensions.resolve("iris");
+        if (!Files.exists(irisNamespace, LinkOption.NOFOLLOW_LINKS)) {
+            return worldNames;
+        }
+        if (Files.isSymbolicLink(dimensions) || Files.isSymbolicLink(irisNamespace)) {
+            throw new IOException("Iris dimension storage contains a symbolic link: " + irisNamespace);
+        }
+        if (!Files.isDirectory(irisNamespace, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Iris dimension storage is not a directory: " + irisNamespace);
+        }
+
+        try (DirectoryStream<Path> children = Files.newDirectoryStream(irisNamespace)) {
+            for (Path child : children) {
+                if (Files.isSymbolicLink(child) || !Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS)) {
+                    continue;
+                }
+
+                String name = child.getFileName().toString();
+                if (QUARANTINE_NAME.matcher(name).matches()) {
+                    worldNames.add(name);
+                    continue;
+                }
+
+                String transientBaseName = TransientWorldCleanupSupport.transientStudioBaseWorldName(name);
+                String normalized = normalizeQueueEntry(transientBaseName, root.getFileName().toString());
+                if (normalized != null) {
+                    worldNames.add(normalized);
+                }
+            }
+        }
+        return worldNames;
+    }
+
+    static List<Path> resolveQueueEntryPaths(File levelRoot, String worldName) throws IOException {
+        QueueEntry entry = QueueEntry.parse(worldName, levelRoot.getName());
+        List<DeleteTarget> targets = entry.targets(levelRoot);
+        ArrayList<Path> paths = new ArrayList<>(targets.size());
+        for (DeleteTarget target : targets) {
+            paths.add(target.path());
+        }
+        return List.copyOf(paths);
+    }
+
+    private static void replaceQueueFile(Path temporary, Path queuePath) throws IOException {
+        try {
+            Files.move(temporary, queuePath, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+        } catch (AtomicMoveNotSupportedException unsupported) {
+            Files.move(temporary, queuePath, StandardCopyOption.REPLACE_EXISTING);
+        }
+    }
+
+    private static void forceDirectory(Path directory) throws IOException {
+        try (FileChannel channel = FileChannel.open(directory, StandardOpenOption.READ)) {
+            channel.force(true);
+        }
+    }
+
+    private static void unregisterTransientStudioWorlds() {
+        try {
+            int unregistered = IrisCreator.removeTransientStudioWorldsFromBukkitYml();
+            if (unregistered > 0) {
+                Iris.info("Unregistered " + unregistered + " transient studio world(s) from bukkit.yml on startup.");
+            }
+        } catch (Throwable failure) {
+            Iris.reportError("Failed to unregister transient studio worlds from bukkit.yml on startup.", failure);
+        }
+    }
+
+    private static void processEntry(
+            File levelRoot,
+            String worldName,
+            LinkedHashMap<String, String> remaining
+    ) {
+        try {
+            QueueEntry entry = QueueEntry.parse(worldName, levelRoot.getName());
+            List<DeleteTarget> targets = entry.targets(levelRoot);
+            if (targets.stream().anyMatch(PendingWorldDeleteQueue::isLoaded)) {
+                Iris.warn("Skipping queued deletion for \"" + worldName + "\" because it is currently loaded.");
+                remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
+                return;
+            }
+
+            boolean foundAny = false;
+            boolean deletedAll = true;
+            for (DeleteTarget target : targets) {
+                Path worldFolder = target.path();
+                if (!Files.exists(worldFolder, LinkOption.NOFOLLOW_LINKS)) {
+                    continue;
+                }
+                if (Files.isSymbolicLink(worldFolder) || !Files.isDirectory(worldFolder, LinkOption.NOFOLLOW_LINKS)) {
+                    throw new IOException("Queued world target is not a safe directory: " + worldFolder);
+                }
+
+                foundAny = true;
+                try {
+                    deleteTree(worldFolder);
+                    Iris.info("Deleted queued world folder \"" + worldFolder.getFileName() + "\".");
+                } catch (IOException failure) {
+                    deletedAll = false;
+                    Iris.reportError("Failed to delete queued world folder \"" + worldFolder + "\".", failure);
+                }
+            }
+
+            if (!foundAny) {
+                Iris.info("Queued world deletion skipped for \"" + worldName + "\" (folder missing).");
+                return;
+            }
+            if (!deletedAll) {
+                remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
+            }
+        } catch (Throwable failure) {
+            remaining.put(worldName.toLowerCase(Locale.ROOT), worldName);
+            Iris.reportError("Failed to safely process queued world deletion for \"" + worldName + "\".", failure);
+        }
+    }
+
+    private static boolean isLoaded(DeleteTarget target) {
+        if (target.key() != null && WorldIdentity.resolve(target.key()).isPresent()) {
+            return true;
+        }
+
+        Path targetPath = target.path().toAbsolutePath().normalize();
+        for (World world : Bukkit.getWorlds()) {
+            if (world.getWorldFolder().toPath().toAbsolutePath().normalize().equals(targetPath)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static void deleteTree(Path target) throws IOException {
+        Files.walkFileTree(target, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attributes) throws IOException {
+                Files.delete(file);
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult postVisitDirectory(Path directory, IOException failure) throws IOException {
+                if (failure != null) {
+                    throw failure;
+                }
+                Files.delete(directory);
+                return FileVisitResult.CONTINUE;
+            }
+        });
+    }
+
+    private enum QueueEntryType {
+        EXACT,
+        LOGICAL,
+        QUARANTINE
+    }
+
+    private record QueueEntry(String storedName, QueueEntryType type) {
+        private static QueueEntry parse(String worldName, String levelName) {
+            String stored = normalizeStoredQueueEntry(worldName, levelName);
+            if (stored == null) {
+                throw new IllegalArgumentException("Unsafe queued Iris world deletion target: " + worldName);
+            }
+            boolean exact = stored.startsWith(EXACT_PREFIX);
+            String normalized = exact ? stored.substring(EXACT_PREFIX.length()) : stored;
+            QueueEntryType type = QUARANTINE_NAME.matcher(normalized).matches()
+                    ? QueueEntryType.QUARANTINE
+                    : exact ? QueueEntryType.EXACT : QueueEntryType.LOGICAL;
+            return new QueueEntry(normalized, type);
+        }
+
+        private List<DeleteTarget> targets(File levelRoot) throws IOException {
+            if (type == QueueEntryType.QUARANTINE) {
+                return List.of(new DeleteTarget(null, requireSafeQuarantinePath(levelRoot, storedName)));
+            }
+
+            if (type == QueueEntryType.EXACT) {
+                NamespacedKey key = IrisWorldStorage.managedKeyFromName(storedName, levelRoot.getName());
+                Path path = IrisWorldStorage.requireSafeManagedDimensionRoot(levelRoot, key).toPath();
+                return List.of(new DeleteTarget(key, path));
+            }
+
+            ArrayList<DeleteTarget> targets = new ArrayList<>(3);
+            for (String familyWorldName : TransientWorldCleanupSupport.worldFamilyNames(storedName)) {
+                NamespacedKey key = IrisWorldStorage.managedKeyFromName(familyWorldName, levelRoot.getName());
+                Path path = IrisWorldStorage.requireSafeManagedDimensionRoot(levelRoot, key).toPath();
+                targets.add(new DeleteTarget(key, path));
+            }
+            return targets;
+        }
+    }
+
+    private static Path requireSafeQuarantinePath(File levelRoot, String quarantineName) throws IOException {
+        if (!QUARANTINE_NAME.matcher(quarantineName).matches()) {
+            throw new IOException("Invalid Iris quarantine directory name: " + quarantineName);
+        }
+
+        Path root = levelRoot.toPath().toAbsolutePath().normalize();
+        Path dimensions = root.resolve("dimensions");
+        Path irisNamespace = dimensions.resolve("iris");
+        Path target = irisNamespace.resolve(quarantineName).normalize();
+        if (!Objects.equals(target.getParent(), irisNamespace)) {
+            throw new IOException("Iris quarantine target escapes its namespace: " + target);
+        }
+        for (Path path : List.of(dimensions, irisNamespace, target)) {
+            if (Files.isSymbolicLink(path)) {
+                throw new IOException("Iris quarantine storage contains a symbolic link: " + path);
+            }
+        }
+        return target;
+    }
+
+    private record DeleteTarget(@Nullable NamespacedKey key, Path path) {
     }
 }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandDeveloper.java

@@ -21,6 +21,7 @@ package art.arcane.iris.core.commands;
 import com.google.gson.JsonObject;
 import art.arcane.iris.Iris;
 import art.arcane.iris.core.ServerConfigurator;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
 import art.arcane.iris.core.nms.datapack.DataVersion;
 import art.arcane.iris.core.runtime.ChunkClearer;
 import art.arcane.iris.core.runtime.GoldenHashScanner;
@@ -216,7 +217,15 @@ public class CommandDeveloper implements DirectorExecutor {
             Iris.service(StudioSVC.class).downloadSearch(sender(), pack.getLoadKey(), true);
         }
 
-        Iris.service(StudioSVC.class).installIntoWorld(sender(), pack, folder);
+        try (LifecycleOperationCoordinator.Lease lease = LifecycleOperationCoordinator.get().acquire(
+                LifecycleOperationCoordinator.Domain.PACK_MUTATION,
+                LifecycleOperationCoordinator.OperationKind.PACK_PUBLISH,
+                pack.getLoadKey()
+        )) {
+            Iris.service(StudioSVC.class).replaceIntoWorld(sender(), pack, folder);
+        } catch (LifecycleOperationCoordinator.BusyException e) {
+            sender().sendMessage(C.YELLOW + e.getMessage());
+        }
     }
 
     @Director(description = "Test", descriptionKey = "iris.director.commanddeveloper.director.test")

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandFind.java

@@ -125,6 +125,7 @@ public class CommandFind implements DirectorExecutor {
 
         String structureKey = structure == null ? "" : structure.trim();
         Structure nativeStructure = resolveNativeStructure(structureKey);
+        boolean irisReplacement = false;
         if (nativeStructure != null) {
             IrisNativeStructureDecision decision = NativeStructureGenerationPolicy.resolve(
                     e, structureKey, false);
@@ -134,7 +135,8 @@ public class CommandFind implements DirectorExecutor {
                         structureKey, decision.status()));
                 return;
             }
-            if (decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS) {
+            irisReplacement = decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS;
+            if (irisReplacement && !IrisStructureLocator.hasNativePlacement(e, structureKey)) {
                 locateIrisStructure(e, structureKey, commandSender);
                 return;
             }
@@ -149,6 +151,9 @@ public class CommandFind implements DirectorExecutor {
             commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_FIND_UNKNOWN_STRUCTURE, MessageArgument.untrusted("structureKey", structureKey)));
             return;
         }
+        final boolean replacementLocate = irisReplacement;
+        final boolean explicitNativePlacement = IrisStructureLocator.hasNativePlacement(
+                e, structureKey);
 
         Player target = player();
         if (target == null) {
@@ -161,7 +166,8 @@ public class CommandFind implements DirectorExecutor {
         commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_FIND_LOCATING, MessageArgument.untrusted("structureKey", structureKey)));
         J.s(() -> {
             try {
-                if (!StructureReachability.isReachable(e, structureKey)) {
+                if (!replacementLocate && !explicitNativePlacement
+                        && !StructureReachability.isReachable(e, structureKey)) {
                     KList<String> miss = StructureReachability.missingBiomeKeys(e, structureKey);
                     sendStructureMessage(target, commandSender,
                             C.YELLOW + structureKey + " cannot generate in this world (its required biomes are not produced by this pack"

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandIris.java

@@ -19,16 +19,24 @@
 package art.arcane.iris.core.commands;
 
 import art.arcane.iris.Iris;
+import art.arcane.iris.core.BukkitWorldReconciler;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.core.IrisSettings;
+import art.arcane.iris.core.DatapackInstallResult;
 import art.arcane.iris.core.IrisWorldStorage;
 import art.arcane.iris.core.IrisWorlds;
 import art.arcane.iris.core.ServerConfigurator;
+import art.arcane.iris.core.lifecycle.BukkitWorldConfiguration;
+import art.arcane.iris.core.lifecycle.IrisWorldRemovalService;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
 import art.arcane.iris.core.lifecycle.WorldLifecycleService;
 import art.arcane.iris.core.loader.IrisData;
+import art.arcane.iris.core.pack.AtomicDirectoryPublisher;
 import art.arcane.iris.core.pack.PackDownloader;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.service.StudioSVC;
 import art.arcane.iris.core.tools.IrisToolbelt;
+import art.arcane.iris.engine.platform.PlatformChunkGenerator;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.volmlib.util.collection.KList;
@@ -41,7 +49,6 @@ import art.arcane.volmlib.util.director.annotations.Param;
 import art.arcane.volmlib.util.director.exceptions.DirectorParsingException;
 import art.arcane.iris.util.common.director.specialhandlers.NullablePlayerHandler;
 import art.arcane.iris.util.common.format.C;
-import art.arcane.volmlib.util.io.IO;
 import art.arcane.iris.util.common.misc.ServerProperties;
 import art.arcane.iris.util.common.plugin.VolmitSender;
 import art.arcane.iris.util.common.scheduling.J;
@@ -49,32 +56,44 @@ import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.NamespacedKey;
 import org.bukkit.World;
-import org.bukkit.configuration.ConfigurationSection;
-import org.bukkit.configuration.file.YamlConfiguration;
 import org.bukkit.entity.Player;
 
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.FileAlreadyExistsException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.Comparator;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
 import java.util.Properties;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Stream;
 
-import static art.arcane.iris.core.service.EditSVC.deletingWorld;
 import static art.arcane.iris.util.common.misc.ServerProperties.BUKKIT_YML;
 import static org.bukkit.Bukkit.getServer;
 
 import art.arcane.iris.core.localization.IrisLanguage;
 import art.arcane.iris.core.localization.IrisMessages;
 import art.arcane.volmlib.util.localization.MessageArgument;
-import art.arcane.iris.core.localization.BukkitCommandMessages;
 import art.arcane.iris.core.localization.BukkitCommandMessagesExtended;
 import art.arcane.iris.core.localization.RuntimeUiMessages;
 @Director(name = "iris", aliases = {"ir", "irs"}, description = "Basic Command", descriptionKey = "iris.director.commandiris.director.basic_command")
 public class CommandIris implements DirectorExecutor {
+    private static final long WORLD_UNLOAD_TIMEOUT_SECONDS = 150L;
+
     private CommandStudio studio;
     private CommandPregen pregen;
     private CommandObject object;
@@ -85,10 +104,7 @@ public class CommandIris implements DirectorExecutor {
     private CommandPack pack;
     private CommandFind find;
     private CommandDatapack datapack;
-    public static boolean worldCreation = false;
     private static final AtomicReference<Thread> mainWorld = new AtomicReference<>();
-    String WorldEngine;
-    String worldNameToCheck = "YourWorldName";
     VolmitSender sender = Iris.getSender();
 
     @Director(description = "Create a new world", descriptionKey = "iris.director.commandiris.director.create_new_world", aliases = {"c"})
@@ -107,7 +123,15 @@ public class CommandIris implements DirectorExecutor {
             @Param(aliases = "main-world", description = "Whether or not to automatically use this world as the main world", descriptionKey = "iris.director.commandiris.param.whether_not_automatically_use_this_world_as_main_world", defaultValue = "false")
             boolean main
     ) {
-        String worldName = IrisWorldStorage.logicalName(IrisWorldStorage.keyFromName(name));
+        NamespacedKey worldKey;
+        try {
+            worldKey = IrisWorldStorage.managedKeyFromName(name);
+            IrisWorldStorage.requireSafeManagedDimensionRoot(worldKey);
+        } catch (IllegalArgumentException e) {
+            sender().sendMessage(C.RED + e.getMessage());
+            return;
+        }
+        String worldName = IrisWorldStorage.logicalName(worldKey);
         if (worldName.equalsIgnoreCase("iris")) {
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_YOU_CANNOT_USE_WORLD_NAME_IRIS_CREATING_WORLDS_AS_IRIS));
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_MAY_WE_SUGGEST_NAME_IRISWORLD_INSTEAD));
@@ -145,7 +169,6 @@ public class CommandIris implements DirectorExecutor {
         }
 
         try {
-            worldCreation = true;
             IrisToolbelt.createWorld()
                     .dimension(resolvedType)
                     .name(worldName)
@@ -160,22 +183,46 @@ public class CommandIris implements DirectorExecutor {
                 }));
             }
         } catch (Throwable e) {
+            if (reportExpectedCreationInterruption(e)) {
+                return;
+            }
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_EXCEPTION_RAISED_DURING_CREATION_SEE_CONSOLE_MORE_DETAILS));
             Iris.reportError("Exception raised during world creation for \"" + worldName + "\".", e);
-            worldCreation = false;
             return;
         }
 
-        worldCreation = false;
         sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_SUCCESSFULLY_CREATED_YOUR_WORLD));
         if (main) sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_YOUR_WORLD_WILL_AUTOMATICALLY_BE_SET_AS_MAIN_WORLD_WHEN));
     }
 
     private boolean updateMainWorld(String newName) {
+        LifecycleOperationCoordinator.Lease lease;
+        try {
+            lease = LifecycleOperationCoordinator.get().acquire(
+                    LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                    LifecycleOperationCoordinator.OperationKind.WORLD_PROMOTE,
+                    newName
+            );
+        } catch (LifecycleOperationCoordinator.BusyException e) {
+            Iris.error("Could not promote Iris world \"" + newName + "\": " + e.getMessage());
+            return false;
+        }
+
+        try {
+            return updateMainWorldUnderLease(newName);
+        } finally {
+            lease.close();
+        }
+    }
+
+    private boolean updateMainWorldUnderLease(String newName) {
         try {
             File oldLevelRoot = IrisWorldStorage.levelRoot();
             File worldContainer = oldLevelRoot.getParentFile();
-            Properties data = ServerProperties.DATA;
+            if (worldContainer == null) {
+                throw new IllegalStateException("Current level folder has no world container.");
+            }
+            Properties data = new Properties();
             try (FileInputStream in = new FileInputStream(ServerProperties.SERVER_PROPERTIES)) {
                 data.load(in);
             }
@@ -186,22 +233,6 @@ public class CommandIris implements DirectorExecutor {
             }
 
             File newLevelRoot = new File(worldContainer, newName);
-            if (!newLevelRoot.exists() && !newLevelRoot.mkdirs()) {
-                throw new IllegalStateException("Could not create target level folder: " + newLevelRoot.getAbsolutePath());
-            }
-
-            for (String sub : List.of("data", "datapacks", "players")) {
-                File source = new File(oldLevelRoot, sub);
-                if (!source.exists()) {
-                    continue;
-                }
-
-                IO.copyDirectory(source.toPath(), new File(newLevelRoot, sub).toPath());
-            }
-
-            File targetDimensionRoot = IrisWorldStorage.dimensionRoot(newLevelRoot, NamespacedKey.minecraft("overworld"));
-            IO.copyDirectory(sourceDimensionRoot.toPath(), targetDimensionRoot.toPath());
-
             World sourceWorld = WorldIdentity.resolve(IrisWorldStorage.keyFromName(newName)).orElse(null);
             Long stagedSeed = IrisWorlds.readBukkitWorldSeed(newName);
             if (sourceWorld == null && stagedSeed == null) {
@@ -210,8 +241,18 @@ public class CommandIris implements DirectorExecutor {
             long promotedSeed = sourceWorld == null ? stagedSeed : sourceWorld.getSeed();
             data.setProperty("level-name", newName);
             data.setProperty("level-seed", Long.toString(promotedSeed));
-            try (FileOutputStream out = new FileOutputStream(ServerProperties.SERVER_PROPERTIES)) {
-                data.store(out, null);
+
+            try (MainWorldPublication publication = publishMainWorldFiles(
+                    oldLevelRoot.toPath(),
+                    sourceDimensionRoot.toPath(),
+                    newLevelRoot.toPath()
+            )) {
+                writeServerPropertiesAtomically(ServerProperties.SERVER_PROPERTIES.toPath(), data);
+                publication.commit();
+            }
+            synchronized (ServerProperties.DATA) {
+                ServerProperties.DATA.clear();
+                ServerProperties.DATA.putAll(data);
             }
             return true;
         } catch (Throwable e) {
@@ -221,57 +262,204 @@ public class CommandIris implements DirectorExecutor {
         }
     }
 
-    private boolean stageFoliaWorldCreation(String name, IrisDimension dimension, long seed, boolean main) {
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_RUNTIME_WORLD_CREATION_IS_DISABLED_ON_FOLIA));
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_PREPARING_WORLD_FILES_BUKKIT_YML_NEXT_STARTUP));
-
-        File worldFolder = IrisWorldStorage.dimensionRoot(name);
-        IrisDimension installed = Iris.service(StudioSVC.class).installIntoWorld(sender(), dimension, worldFolder);
-        if (installed == null) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_STAGE_WORLD_FILES_DIMENSION, MessageArgument.untrusted("value", dimension.getLoadKey())));
-            return false;
+    static MainWorldPublication publishMainWorldFiles(
+            Path currentLevelRoot,
+            Path sourceDimensionRoot,
+            Path targetLevelRoot
+    ) throws IOException {
+        Path current = Objects.requireNonNull(currentLevelRoot, "currentLevelRoot").toAbsolutePath().normalize();
+        Path sourceDimension = Objects.requireNonNull(sourceDimensionRoot, "sourceDimensionRoot").toAbsolutePath().normalize();
+        Path target = Objects.requireNonNull(targetLevelRoot, "targetLevelRoot").toAbsolutePath().normalize();
+        Path worldContainer = current.getParent();
+        Path sourceNamespace = current.resolve("dimensions/iris");
+        if (worldContainer == null || !Objects.equals(target.getParent(), worldContainer)) {
+            throw new IOException("Promoted main world must be a direct child of the world container.");
         }
-
-        if (!registerWorldInBukkitYml(name, dimension.getLoadKey(), seed)) {
-            return false;
+        if (!Objects.equals(sourceDimension.getParent(), sourceNamespace)) {
+            throw new IOException("Promoted source must be a direct Iris dimension.");
         }
+        if (Objects.equals(current, target)) {
+            throw new IOException("Promoted main world cannot replace the current main world.");
+        }
+        if (Files.isSymbolicLink(worldContainer)
+                || Files.isSymbolicLink(current)
+                || !Files.isDirectory(current, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Current world storage is missing or unsafe.");
+        }
+        if (Files.isSymbolicLink(sourceDimension)
+                || !Files.isDirectory(sourceDimension, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Promoted Iris dimension is missing or unsafe: " + sourceDimension);
+        }
+        requireAbsentMainWorldTarget(target);
 
-        if (main) {
-            if (updateMainWorld(name)) {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_UPDATED_SERVER_PROPERTIES_LEVEL_NAME, MessageArgument.untrusted("name", name)));
-            } else {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_WORLD_WAS_STAGED_BUT_FAILED_UPDATE_SERVER_PROPERTIES_MAIN_WORLD));
-                return false;
+        Path stage = Files.createTempDirectory(worldContainer, "." + target.getFileName() + ".promoting-");
+        boolean published = false;
+        try {
+            for (String subdirectory : List.of("data", "datapacks", "players")) {
+                Path source = current.resolve(subdirectory);
+                if (!Files.exists(source, LinkOption.NOFOLLOW_LINKS) && !Files.isSymbolicLink(source)) {
+                    continue;
+                }
+                copyWorldTree(source, stage.resolve(subdirectory));
+            }
+
+            Path targetDimension = IrisWorldStorage.dimensionRoot(
+                    stage.toFile(),
+                    NamespacedKey.minecraft("overworld")
+            ).toPath();
+            copyWorldTree(sourceDimension, targetDimension);
+            requireAbsentMainWorldTarget(target);
+            Files.move(stage, target);
+            published = true;
+            return new MainWorldPublication(target);
+        } finally {
+            if (!published) {
+                AtomicDirectoryPublisher.deleteTree(stage);
             }
         }
+    }
 
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_STAGED_IRIS_WORLD_WITH_GENERATOR_IRIS_SEED, MessageArgument.untrusted("name", name), MessageArgument.untrusted("value", dimension.getLoadKey()), MessageArgument.untrusted("seed", seed)));
-        if (main) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_THIS_WORLD_IS_NOW_CONFIGURED_AS_MAIN_NEXT_RESTART));
+    private static void requireAbsentMainWorldTarget(Path target) throws IOException {
+        if (Files.exists(target, LinkOption.NOFOLLOW_LINKS) || Files.isSymbolicLink(target)) {
+            throw new FileAlreadyExistsException("Main-world target already exists: " + target);
+        }
+    }
+
+    private static void copyWorldTree(Path source, Path target) throws IOException {
+        if (Files.isSymbolicLink(source)) {
+            throw new IOException("World data contains a symbolic link: " + source);
+        }
+        if (Files.isRegularFile(source, LinkOption.NOFOLLOW_LINKS)) {
+            Files.createDirectories(target.getParent());
+            Files.copy(source, target, StandardCopyOption.COPY_ATTRIBUTES);
+            return;
+        }
+        if (!Files.isDirectory(source, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("World data contains an unsupported entry: " + source);
+        }
+        try (Stream<Path> entries = Files.walk(source)) {
+            for (Path entry : entries.sorted(Comparator.naturalOrder()).toList()) {
+                if (Files.isSymbolicLink(entry)) {
+                    throw new IOException("World data contains a symbolic link: " + entry);
+                }
+                Path destination = target.resolve(source.relativize(entry)).normalize();
+                if (!destination.startsWith(target)) {
+                    throw new IOException("World data escapes its promotion stage: " + entry);
+                }
+                if (Files.isDirectory(entry, LinkOption.NOFOLLOW_LINKS)) {
+                    Files.createDirectories(destination);
+                } else if (Files.isRegularFile(entry, LinkOption.NOFOLLOW_LINKS)) {
+                    Files.createDirectories(destination.getParent());
+                    Files.copy(entry, destination, StandardCopyOption.COPY_ATTRIBUTES);
+                } else {
+                    throw new IOException("World data contains an unsupported entry: " + entry);
+                }
+            }
+        }
+    }
+
+    private static void writeServerPropertiesAtomically(Path propertiesFile, Properties data) throws IOException {
+        Path target = propertiesFile.toAbsolutePath().normalize();
+        Path parent = target.getParent();
+        if (parent == null) {
+            throw new IOException("server.properties has no parent directory.");
+        }
+        Path stage = Files.createTempFile(parent, ".server.properties.promoting-", ".tmp");
+        IOException operationFailure = null;
+        try {
+            try (FileOutputStream out = new FileOutputStream(stage.toFile())) {
+                data.store(out, null);
+                out.getFD().sync();
+            }
+            try {
+                Files.move(stage, target, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException e) {
+                Files.move(stage, target, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } catch (IOException e) {
+            operationFailure = e;
+            throw e;
+        } finally {
+            try {
+                Files.deleteIfExists(stage);
+            } catch (IOException cleanupFailure) {
+                if (operationFailure != null) {
+                    operationFailure.addSuppressed(cleanupFailure);
+                } else {
+                    throw cleanupFailure;
+                }
+            }
+        }
+    }
+
+    private boolean stageFoliaWorldCreation(String name, IrisDimension dimension, long seed, boolean main) {
+        NamespacedKey worldKey = IrisWorldStorage.managedKeyFromName(name);
+        LifecycleOperationCoordinator.Lease worldLease = null;
+        File worldFolder = IrisWorldStorage.requireSafeManagedDimensionRoot(worldKey);
+        try {
+            LifecycleOperationCoordinator coordinator = LifecycleOperationCoordinator.get();
+            worldLease = coordinator.acquire(
+                    LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                    LifecycleOperationCoordinator.OperationKind.WORLD_CREATE,
+                    worldKey.toString());
+            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_RUNTIME_WORLD_CREATION_IS_DISABLED_ON_FOLIA));
+            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_PREPARING_WORLD_FILES_BUKKIT_YML_NEXT_STARTUP));
+            if (worldFolder.exists()) {
+                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_THAT_FOLDER_ALREADY_EXISTS));
+                return false;
+            }
+
+            DatapackInstallResult datapackResult = ServerConfigurator.installDataPacksIfChanged(true);
+            if (!datapackResult.succeeded()) {
+                sender().sendMessage(C.RED + "Failed to compile the Iris datapack. No world files were staged.");
+                return false;
+            }
+            IrisDimension installed = Iris.service(StudioSVC.class).installIntoWorld(sender(), dimension, worldFolder);
+            if (installed == null) {
+                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_STAGE_WORLD_FILES_DIMENSION, MessageArgument.untrusted("value", dimension.getLoadKey())));
+                deleteDirectorySafely(worldFolder);
+                return false;
+            }
+
+            if (!registerWorldInBukkitYml(name, dimension.getLoadKey(), seed)) {
+                deleteDirectorySafely(worldFolder);
+                return false;
+            }
+
+            if (main) {
+                if (updateMainWorldUnderLease(name)) {
+                    sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_UPDATED_SERVER_PROPERTIES_LEVEL_NAME, MessageArgument.untrusted("name", name)));
+                } else {
+                    sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_WORLD_WAS_STAGED_BUT_FAILED_UPDATE_SERVER_PROPERTIES_MAIN_WORLD));
+                    try {
+                        BukkitWorldConfiguration.remove(BUKKIT_YML, name);
+                    } catch (IOException e) {
+                        Iris.reportError("Failed to roll back bukkit.yml after main-world staging failed.", e);
+                    }
+                    deleteDirectorySafely(worldFolder);
+                    return false;
+                }
+            }
+
+            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_STAGED_IRIS_WORLD_WITH_GENERATOR_IRIS_SEED, MessageArgument.untrusted("name", name), MessageArgument.untrusted("value", dimension.getLoadKey()), MessageArgument.untrusted("seed", seed)));
+            if (main) {
+                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_THIS_WORLD_IS_NOW_CONFIGURED_AS_MAIN_NEXT_RESTART));
+            }
+            return true;
+        } catch (LifecycleOperationCoordinator.BusyException e) {
+            sender().sendMessage(C.YELLOW + e.getMessage());
+            return false;
+        } finally {
+            if (worldLease != null) {
+                worldLease.close();
+            }
         }
-        return true;
     }
 
     private boolean registerWorldInBukkitYml(String worldName, String dimension, Long seed) {
         String logicalWorldName = IrisWorldStorage.logicalName(IrisWorldStorage.keyFromName(worldName));
-        YamlConfiguration yml = YamlConfiguration.loadConfiguration(BUKKIT_YML);
-        ConfigurationSection worlds = yml.getConfigurationSection("worlds");
-        if (worlds == null) {
-            worlds = yml.createSection("worlds");
-        }
-        ConfigurationSection worldSection = worlds.getConfigurationSection(logicalWorldName);
-        if (worldSection == null) {
-            worldSection = worlds.createSection(logicalWorldName);
-        }
-
-        String generator = "Iris:" + dimension;
-        worldSection.set("generator", generator);
-        if (seed != null) {
-            worldSection.set("seed", seed);
-        }
-
         try {
-            yml.save(BUKKIT_YML);
+            BukkitWorldConfiguration.register(BUKKIT_YML, logicalWorldName, dimension, seed);
             Iris.info("Registered \"" + logicalWorldName + "\" in bukkit.yml");
             return true;
         } catch (IOException e) {
@@ -282,6 +470,31 @@ public class CommandIris implements DirectorExecutor {
         }
     }
 
+    private void deleteDirectorySafely(File directory) {
+        try {
+            AtomicDirectoryPublisher.deleteTree(directory.toPath());
+        } catch (IOException e) {
+            Iris.reportError("Failed to roll back staged world folder \"" + directory.getAbsolutePath() + "\".", e);
+        }
+    }
+
+    private boolean reportExpectedCreationInterruption(Throwable failure) {
+        Throwable current = failure;
+        while (current != null) {
+            if (current instanceof LifecycleOperationCoordinator.BusyException) {
+                sender().sendMessage(C.YELLOW + current.getMessage());
+                return true;
+            }
+            current = current.getCause();
+        }
+        String message = failure.getMessage();
+        if (message != null && message.contains("queued a restart")) {
+            sender().sendMessage(C.YELLOW + message);
+            return true;
+        }
+        return false;
+    }
+
     @Director(description = "Teleport to another world", descriptionKey = "iris.director.commandiris.director.teleport_another_world", aliases = {"tp"}, sync = true)
     public void teleport(
             @Param(description = "World to teleport to", descriptionKey = "iris.director.commandiris.param.world_teleport")
@@ -368,78 +581,73 @@ public class CommandIris implements DirectorExecutor {
 
     @Director(description = "Remove an Iris world", descriptionKey = "iris.director.commandiris.director.remove_iris_world", aliases = {"rm"}, sync = true)
     public void remove(
-            @Param(description = "The world to remove", descriptionKey = "iris.director.commandiris.param.world_remove")
-            World world,
+            @Param(description = "The loaded or disk-only Iris world to remove", descriptionKey = "iris.director.commandiris.param.world_remove", customHandler = ManagedWorldNameHandler.class)
+            String world,
             @Param(description = "Whether to also remove the folder (if set to false, just does not load the world)", descriptionKey = "iris.director.commandiris.param.whether_also_remove_folder_if_set_false_just_does_not_load_world", defaultValue = "true")
             boolean delete
     ) {
-        if (!IrisToolbelt.isIrisWorld(world)) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_THIS_IS_NOT_IRIS_WORLD_IRIS_WORLDS, MessageArgument.untrusted("value", String.join(", ", getServer().getWorlds().stream().filter(IrisToolbelt::isIrisWorld).map(World::getName).toList()))));
-            return;
-        }
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_REMOVING_WORLD, MessageArgument.untrusted("value", world.getName())));
-
-        if (!IrisToolbelt.evacuate(world)) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_EVACUATE_WORLD, MessageArgument.untrusted("value", world.getName())));
-            return;
-        }
-
-        if (!WorldLifecycleService.get().unload(world, false)) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD, MessageArgument.untrusted("value", world.getName())));
-            return;
-        }
-
-        try {
-            if (IrisToolbelt.removeWorld(world)) {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_SUCCESSFULLY_REMOVED_FROM_BUKKIT_YML, MessageArgument.untrusted("value", world.getName())));
-            } else {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_LOOKS_LIKE_WORLD_WAS_ALREADY_REMOVED_FROM_BUKKIT_YML));
+        VolmitSender responseSender = sender();
+        responseSender.sendMessage(C.GRAY + "Removing Iris world '" + world + "'...");
+        IrisWorldRemovalService.get().remove(world, delete).whenComplete((result, throwable) -> {
+            Runnable response = () -> reportRemovalResult(responseSender, world, result, throwable);
+            if (responseSender.isPlayer() && J.runEntity(responseSender.player(), response)) {
+                return;
             }
-        } catch (IOException e) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_SAVE_BUKKIT_YML_BECAUSE, MessageArgument.untrusted("value", String.valueOf(e.getMessage()))));
-            Iris.reportError("Failed to remove world \"" + world.getName() + "\" from bukkit.yml.", e);
-        }
-        IrisToolbelt.evacuate(world, "Deleting world");
-        deletingWorld = true;
-        if (!delete) {
-            deletingWorld = false;
-            return;
-        }
-        VolmitSender sender = sender();
-        J.a(() -> {
-            int retries = 12;
-
-            if (deleteDirectory(world.getWorldFolder())) {
-                sender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_IRIS_SUCCESSFULLY_REMOVED_WORLD_FOLDER));
-            } else {
-                while(true){
-                    if (deleteDirectory(world.getWorldFolder())){
-                        sender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_IRIS_SUCCESSFULLY_REMOVED_WORLD_FOLDER_2));
-                        break;
-                    }
-                    retries--;
-                    if (retries == 0){
-                        sender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_IRIS_FAILED_REMOVE_WORLD_FOLDER));
-                        break;
-                    }
-                    J.sleep(3000);
-                }
-            }
-            deletingWorld = false;
+            J.s(response);
         });
     }
 
-    public static boolean deleteDirectory(File dir) {
-        if (dir.isDirectory()) {
-            File[] children = dir.listFiles();
-            for (int i = 0; i < children.length; i++) {
-                boolean success = deleteDirectory(children[i]);
-                if (!success) {
-                    return false;
+    private void reportRemovalResult(
+            VolmitSender responseSender,
+            String requestedWorld,
+            IrisWorldRemovalService.RemovalResult result,
+            Throwable throwable
+    ) {
+        if (throwable != null || result == null) {
+            Throwable failure = throwable == null
+                    ? new IllegalStateException("World removal returned no result.")
+                    : throwable;
+            responseSender.sendMessage(C.RED + "World removal failed unexpectedly; nothing further was deleted.");
+            Iris.reportError("Unexpected world removal failure for \"" + requestedWorld + "\".", failure);
+            return;
+        }
+
+        switch (result.status()) {
+            case UNREGISTERED -> responseSender.sendMessage(C.GREEN + "Unloaded and unregistered '"
+                    + result.target().logicalName() + "'; its files were preserved.");
+            case DELETED -> responseSender.sendMessage(C.GREEN + "Removed Iris world '"
+                    + result.target().logicalName() + "' and deleted its folder.");
+            case DELETE_QUEUED -> responseSender.sendMessage(C.YELLOW + "Removed Iris world '"
+                    + result.target().logicalName() + "'; its quarantined folder will be deleted at startup.");
+            case BUSY -> responseSender.sendMessage(C.YELLOW + "World changes are busy with "
+                    + result.blockingOperation().kind().name().toLowerCase(Locale.ROOT) + " for '"
+                    + result.blockingOperation().target() + "'. Try again when it completes.");
+            case INVALID_IDENTIFIER, PROTECTED_WORLD, NOT_IRIS_WORLD, UNSAFE_PATH, NOT_FOUND ->
+                    responseSender.sendMessage(C.RED + removalFailureDetail(result));
+            default -> {
+                responseSender.sendMessage(C.RED + "World removal stopped at "
+                        + result.status().name().toLowerCase(Locale.ROOT) + ": " + removalFailureDetail(result));
+                if (result.quarantineDirectory() != null) {
+                    responseSender.sendMessage(C.YELLOW + "The recoverable world folder is "
+                            + result.quarantineDirectory().toAbsolutePath() + ".");
+                } else if (result.configurationChanged() || result.registryChanged()) {
+                    responseSender.sendMessage(C.YELLOW + "Removal changed registration state before stopping; "
+                            + "the original world folder was not deleted.");
+                }
+                if (result.failure() != null) {
+                    Iris.reportError("World removal failed for \"" + requestedWorld + "\" at "
+                            + result.status().name() + ".", result.failure());
                 }
             }
         }
-        return dir.delete();
+    }
+
+    private String removalFailureDetail(IrisWorldRemovalService.RemovalResult result) {
+        Throwable failure = result.failure();
+        if (failure == null || failure.getMessage() == null || failure.getMessage().isBlank()) {
+            return result.status().name().toLowerCase(Locale.ROOT).replace('_', ' ');
+        }
+        return failure.getMessage();
     }
 
     @Director(description = "Toggle debug", descriptionKey = "iris.director.commandiris.director.toggle_debug")
@@ -466,7 +674,6 @@ public class CommandIris implements DirectorExecutor {
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_DOWNLOADING_PACK, MessageArgument.untrusted("pack", pack), MessageArgument.untrusted("branch", branch), MessageArgument.trusted("value", overwrite ? IrisLanguage.text(RuntimeUiMessages.DOWNLOAD_OVERWRITE_SUFFIX) : "")));
             Iris.service(StudioSVC.class).downloadSearch(sender(), "IrisDimensions/" + pack + "/" + branch, overwrite);
         }
-        ServerConfigurator.installDataPacksIfChanged(true);
     }
 
     @Director(description = "Get metrics for your world", descriptionKey = "iris.director.commandiris.director.get_metrics_your_world", aliases = "measure", origin = DirectorOrigin.PLAYER)
@@ -508,76 +715,187 @@ public class CommandIris implements DirectorExecutor {
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_THIS_IS_NOT_IRIS_WORLD_IRIS_WORLDS_2, MessageArgument.untrusted("value", String.join(", ", getServer().getWorlds().stream().filter(IrisToolbelt::isIrisWorld).map(World::getName).toList()))));
             return;
         }
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_UNLOADING_WORLD, MessageArgument.untrusted("value", world.getName())));
+        VolmitSender responseSender = sender();
+        responseSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_UNLOADING_WORLD, MessageArgument.untrusted("value", world.getName())));
+        LifecycleOperationCoordinator.Lease lease;
         try {
-            IrisToolbelt.evacuate(world);
-            boolean unloaded = WorldLifecycleService.get().unload(world, false);
-            if (unloaded) {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_WORLD_UNLOADED_SUCCESSFULLY));
-            } else {
-                sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD_2));
-            }
+            lease = LifecycleOperationCoordinator.get().acquire(
+                    LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                    LifecycleOperationCoordinator.OperationKind.WORLD_UNLOAD,
+                    WorldIdentity.serialize(world)
+            );
+        } catch (LifecycleOperationCoordinator.BusyException e) {
+            responseSender.sendMessage(C.YELLOW + e.getMessage());
+            return;
+        }
+        PlatformChunkGenerator generator = IrisToolbelt.access(world);
+        IrisToolbelt.beginWorldMaintenance(world, "world-unload", true);
+        try {
+            AtomicBoolean terminalTimeout = new AtomicBoolean(false);
+            CompletableFuture<Boolean> sequence = IrisToolbelt.evacuateAsync(world)
+                    .thenCompose(evacuated -> {
+                        if (terminalTimeout.get()) {
+                            return CompletableFuture.failedFuture(new TimeoutException(
+                                    "World unload stopped after its terminal timeout."));
+                        }
+                        if (!Boolean.TRUE.equals(evacuated)) {
+                            return CompletableFuture.completedFuture(false);
+                        }
+                        return WorldLifecycleService.get().unloadAsync(world, true);
+                    })
+                    .thenCompose(unloaded -> {
+                        if (terminalTimeout.get()) {
+                            return CompletableFuture.failedFuture(new TimeoutException(
+                                    "World unload stopped after its terminal timeout."));
+                        }
+                        if (!Boolean.TRUE.equals(unloaded) || generator == null) {
+                            return CompletableFuture.completedFuture(Boolean.TRUE.equals(unloaded));
+                        }
+                        return generator.closeAsync().thenApply(ignored -> true);
+                    });
+            guardUnloadCompletion(sequence, terminalTimeout, world.getName())
+                    .whenComplete((unloaded, throwable) -> {
+                        IrisToolbelt.endWorldMaintenance(world, "world-unload");
+                        lease.close();
+                        Runnable response = () -> reportUnloadResult(responseSender, world, unloaded, throwable);
+                        if (responseSender.isPlayer() && J.runEntity(responseSender.player(), response)) {
+                            return;
+                        }
+                        J.s(response);
+                    });
         } catch (Exception e) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD_3, MessageArgument.untrusted("value", String.valueOf(e.getMessage()))));
+            IrisToolbelt.endWorldMaintenance(world, "world-unload");
+            lease.close();
+            responseSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD_3, MessageArgument.untrusted("value", String.valueOf(e.getMessage()))));
             Iris.reportError("Failed to unload world \"" + world.getName() + "\".", e);
         }
     }
 
+    private CompletableFuture<Boolean> guardUnloadCompletion(
+            CompletableFuture<Boolean> source,
+            AtomicBoolean terminalTimeout,
+            String worldName
+    ) {
+        CompletableFuture<Boolean> guarded = new CompletableFuture<>();
+        AtomicBoolean settled = new AtomicBoolean(false);
+        source.whenComplete((unloaded, throwable) -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            if (throwable == null) {
+                guarded.complete(Boolean.TRUE.equals(unloaded));
+            } else {
+                guarded.completeExceptionally(throwable);
+            }
+        });
+        CompletableFuture.delayedExecutor(WORLD_UNLOAD_TIMEOUT_SECONDS, TimeUnit.SECONDS).execute(() -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            terminalTimeout.set(true);
+            TimeoutException timeout = new TimeoutException(
+                    "World unload did not settle within " + WORLD_UNLOAD_TIMEOUT_SECONDS
+                            + " seconds for \"" + worldName + "\".");
+            ServerConfigurator.restart("World unload timed out for \"" + worldName + "\".");
+            guarded.completeExceptionally(timeout);
+        });
+        return guarded;
+    }
+
+    private void reportUnloadResult(VolmitSender responseSender, World world, Boolean unloaded, Throwable throwable) {
+        if (throwable != null) {
+            responseSender.sendMessage(IrisLanguage.text(
+                    BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD_3,
+                    MessageArgument.untrusted("value", String.valueOf(throwable.getMessage()))
+            ));
+            Iris.reportError("Failed to unload world \"" + world.getName() + "\".", throwable);
+            return;
+        }
+        if (Boolean.TRUE.equals(unloaded)) {
+            responseSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_WORLD_UNLOADED_SUCCESSFULLY));
+        } else {
+            responseSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FAILED_UNLOAD_WORLD_2));
+        }
+    }
+
     @Director(description = "Load an Iris World", descriptionKey = "iris.director.commandiris.director.load_iris_world", origin = DirectorOrigin.PLAYER, sync = true, aliases = {"import"})
     public void loadWorld(
-            @Param(description = "The name of the world to load", descriptionKey = "iris.director.commandiris.param.name_world_load")
+            @Param(
+                    description = "The name of the world to load",
+                    descriptionKey = "iris.director.commandiris.param.name_world_load",
+                    customHandler = ManagedWorldNameHandler.class)
             String world
     ) {
-        String logicalWorldName = IrisWorldStorage.logicalName(IrisWorldStorage.keyFromName(world));
-        worldNameToCheck = logicalWorldName;
-        boolean worldExists = doesWorldExist(worldNameToCheck);
-        WorldEngine = logicalWorldName;
+        NamespacedKey worldKey;
+        try {
+            worldKey = IrisWorldStorage.managedKeyFromName(world);
+            IrisWorldStorage.requireSafeManagedDimensionRoot(worldKey);
+        } catch (IllegalArgumentException failure) {
+            sender().sendMessage(C.RED + failure.getMessage());
+            return;
+        }
+        String logicalWorldName = IrisWorldStorage.logicalName(worldKey);
+        boolean worldExists = doesWorldExist(logicalWorldName);
 
         if (!worldExists) {
             sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_DOESNT_EXIST_ON_SERVER, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
             return;
         }
 
-        File directory = new File(IrisWorldStorage.packRoot(IrisWorldStorage.keyFromName(logicalWorldName)), "dimensions");
-
-        String dimension = null;
-        if (directory.exists() && directory.isDirectory()) {
-            File[] files = directory.listFiles();
-            if (files != null) {
-                for (File file : files) {
-                    if (file.isFile()) {
-                        String fileName = file.getName();
-                        if (fileName.endsWith(".json")) {
-                            dimension = fileName.substring(0, fileName.length() - 5);
-                            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_GENERATOR, MessageArgument.untrusted("dimension", dimension)));
-                        }
+        VolmitSender responseSender = sender();
+        responseSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_LOADING_WORLD, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
+        Iris.instance.worldReconciler()
+                .loadWorld(BUKKIT_YML, worldKey.toString())
+                .whenComplete((result, failure) -> {
+                    Runnable response = () -> reportLoadWorldResult(
+                            responseSender,
+                            logicalWorldName,
+                            result,
+                            failure);
+                    if (responseSender.isPlayer() && J.runEntity(responseSender.player(), response)) {
+                        return;
                     }
-                }
-            }
-        } else {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_IS_NOT_IRIS_WORLD, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
-            return;
-        }
-
-        if (dimension == null) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_COULD_NOT_DETERMINE_IRIS_DIMENSION, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
-            return;
-        }
-
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_LOADING_WORLD, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
-
-        if (!registerWorldInBukkitYml(logicalWorldName, dimension, null)) {
-            return;
-        }
-
-        if (J.isFolia()) {
-            sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_FOLIA_CANNOT_LOAD_NEW_WORLDS_AT_RUNTIME_RESTART_SERVER_LOAD, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
-            return;
-        }
-
-        Iris.instance.worldReconciler().checkForBukkitWorlds(logicalWorldName::equals);
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_IRIS_LOADED_SUCCESSFULLY, MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
+                    J.s(response);
+                });
     }
+
+    private void reportLoadWorldResult(
+            VolmitSender responseSender,
+            String logicalWorldName,
+            BukkitWorldReconciler.LoadResult result,
+            Throwable failure
+    ) {
+        if (failure != null) {
+            responseSender.sendMessage(C.RED + "Failed to load Iris world \"" + logicalWorldName + "\": " + failure.getMessage());
+            Iris.reportError("Failed to load Iris world \"" + logicalWorldName + "\".", failure);
+            return;
+        }
+        if (result == null) {
+            IllegalStateException missingResult = new IllegalStateException("World load completed without a result.");
+            responseSender.sendMessage(C.RED + missingResult.getMessage());
+            Iris.reportError("Failed to load Iris world \"" + logicalWorldName + "\".", missingResult);
+            return;
+        }
+        if (result.succeeded()) {
+            responseSender.sendMessage(IrisLanguage.text(
+                    BukkitCommandMessagesExtended.COMMAND_IRIS_LOADED_SUCCESSFULLY,
+                    MessageArgument.untrusted("logicalWorldName", logicalWorldName)));
+            return;
+        }
+
+        C color = result.status() == BukkitWorldReconciler.ReconciliationStatus.BUSY
+                || result.status() == BukkitWorldReconciler.ReconciliationStatus.RESTART_REQUIRED
+                ? C.YELLOW
+                : C.RED;
+        responseSender.sendMessage(color + result.message());
+        Throwable resultFailure = result.failure();
+        if (resultFailure != null
+                && result.status() != BukkitWorldReconciler.ReconciliationStatus.BUSY
+                && result.status() != BukkitWorldReconciler.ReconciliationStatus.RESTART_REQUIRED) {
+            Iris.reportError("Failed to load Iris world \"" + logicalWorldName + "\".", resultFailure);
+        }
+    }
+
     @Director(description = "Evacuate an iris world", descriptionKey = "iris.director.commandiris.director.evacuate_iris_world", origin = DirectorOrigin.PLAYER, sync = true)
     public void evacuate(
             @Param(description = "Evacuate the world", descriptionKey = "iris.director.commandiris.param.evacuate_world")
@@ -596,6 +914,54 @@ public class CommandIris implements DirectorExecutor {
         return worldDirectory.exists() && worldDirectory.isDirectory();
     }
 
+    public static class ManagedWorldNameHandler implements DirectorParameterHandler<String> {
+        @Override
+        public KList<String> getPossibilities() {
+            Set<String> options = new LinkedHashSet<>();
+            for (World world : Bukkit.getWorlds()) {
+                if (IrisToolbelt.isIrisWorld(world)) {
+                    options.add(IrisWorldStorage.logicalName(world));
+                }
+            }
+            for (String identity : IrisWorlds.get().getWorlds().keySet()) {
+                try {
+                    options.add(IrisWorldStorage.logicalName(WorldIdentity.parse(identity)));
+                } catch (IllegalArgumentException ignored) {
+                }
+            }
+
+            File namespace = new File(IrisWorldStorage.levelRoot(), "dimensions/iris");
+            File[] diskWorlds = namespace.listFiles(File::isDirectory);
+            if (diskWorlds != null) {
+                for (File diskWorld : diskWorlds) {
+                    if (!Files.isSymbolicLink(diskWorld.toPath())
+                            && diskWorld.getName().matches("[a-z0-9_-]+")) {
+                        options.add(diskWorld.getName());
+                    }
+                }
+            }
+            return new KList<>(options);
+        }
+
+        @Override
+        public String toString(String value) {
+            return value == null ? "" : value;
+        }
+
+        @Override
+        public String parse(String in, boolean force) throws DirectorParsingException {
+            if (in == null || in.isBlank()) {
+                throw new DirectorParsingException("World identifier cannot be empty");
+            }
+            return in.trim();
+        }
+
+        @Override
+        public boolean supports(Class<?> type) {
+            return type == String.class;
+        }
+    }
+
     public static class PackDimensionTypeHandler implements DirectorParameterHandler<String> {
         @Override
         public KList<String> getPossibilities() {
@@ -603,28 +969,21 @@ public class CommandIris implements DirectorExecutor {
             options.add("default");
 
             File packsFolder = Iris.instance.getDataFolder("packs");
-            File[] packs = packsFolder.listFiles();
-            if (packs != null) {
-                for (File pack : packs) {
-                    if (pack == null || !pack.isDirectory()) {
-                        continue;
-                    }
+            for (File pack : PackDirectoryResolver.listVisiblePackDirectories(packsFolder)) {
+                options.add(pack.getName());
 
-                    options.add(pack.getName());
-
-                    try {
-                        IrisData data = IrisData.get(pack);
-                        for (String key : data.getDimensionLoader().getPossibleKeys()) {
-                            options.add(key);
-                            options.add(pack.getName() + ":" + key);
-                        }
-                    } catch (Throwable ex) {
-                        Iris.warn("Failed to read dimension keys from pack %s: %s%s",
-                                pack.getName(),
-                                ex.getClass().getSimpleName(),
-                                ex.getMessage() == null ? "" : " - " + ex.getMessage());
-                        Iris.reportError(ex);
+                try {
+                    IrisData data = IrisData.get(pack);
+                    for (String key : data.getDimensionLoader().getPossibleKeys()) {
+                        options.add(key);
+                        options.add(pack.getName() + ":" + key);
                     }
+                } catch (Throwable ex) {
+                    Iris.warn("Failed to read dimension keys from pack %s: %s%s",
+                            pack.getName(),
+                            ex.getClass().getSimpleName(),
+                            ex.getMessage() == null ? "" : " - " + ex.getMessage());
+                    Iris.reportError(ex);
                 }
             }
 
@@ -650,4 +1009,32 @@ public class CommandIris implements DirectorExecutor {
             return type == String.class;
         }
     }
+
+    static final class MainWorldPublication implements AutoCloseable {
+        private final Path target;
+        private boolean committed;
+        private boolean closed;
+
+        MainWorldPublication(Path target) {
+            this.target = target;
+        }
+
+        void commit() {
+            if (closed) {
+                throw new IllegalStateException("Main-world publication is already closed.");
+            }
+            committed = true;
+        }
+
+        @Override
+        public void close() throws IOException {
+            if (closed) {
+                return;
+            }
+            closed = true;
+            if (!committed) {
+                AtomicDirectoryPublisher.deleteTree(target);
+            }
+        }
+    }
 }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandObject.java

@@ -22,6 +22,7 @@ import art.arcane.iris.Iris;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.core.link.WorldEditLink;
 import art.arcane.iris.core.loader.IrisData;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.runtime.ObjectStudioActivation;
 import art.arcane.iris.core.runtime.WorldRuntimeControlService;
 import art.arcane.iris.core.service.ObjectSVC;
@@ -73,7 +74,6 @@ import java.io.File;
 import java.io.IOException;
 import java.text.NumberFormat;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -109,25 +109,20 @@ public class CommandObject implements DirectorExecutor {
             sources.put(data.getDataFolder().getName(), data);
         } else {
             File workspace = Iris.service(StudioSVC.class).getWorkspaceFolder();
-            File[] packs = workspace == null ? null : workspace.listFiles();
-            if (packs != null) {
-                Arrays.sort(packs, Comparator.comparing(File::getName, String.CASE_INSENSITIVE_ORDER));
-                for (File pack : packs) {
-                    if (!pack.isDirectory()) continue;
-                    File dimensionsDir = new File(pack, "dimensions");
-                    if (!dimensionsDir.isDirectory()) continue;
-                    IrisData data = IrisData.get(pack);
-                    String[] keys = data.getObjectLoader().getPossibleKeys();
-                    if (keys == null || keys.length == 0) continue;
-                    sources.put(pack.getName(), data);
-                    if (hostDimension == null) {
-                        File[] dimFiles = dimensionsDir.listFiles((f) -> f.isFile() && f.getName().endsWith(".json"));
-                        if (dimFiles != null && dimFiles.length > 0) {
-                            String loadKey = dimFiles[0].getName().replaceFirst("\\.json$", "");
-                            IrisDimension loaded = data.getDimensionLoader().load(loadKey);
-                            if (loaded != null) {
-                                hostDimension = loaded;
-                            }
+            for (File pack : PackDirectoryResolver.listVisiblePackDirectories(workspace)) {
+                File dimensionsDir = new File(pack, "dimensions");
+                if (!dimensionsDir.isDirectory()) continue;
+                IrisData data = IrisData.get(pack);
+                String[] keys = data.getObjectLoader().getPossibleKeys();
+                if (keys == null || keys.length == 0) continue;
+                sources.put(pack.getName(), data);
+                if (hostDimension == null) {
+                    File[] dimFiles = dimensionsDir.listFiles((f) -> f.isFile() && f.getName().endsWith(".json"));
+                    if (dimFiles != null && dimFiles.length > 0) {
+                        String loadKey = dimFiles[0].getName().replaceFirst("\\.json$", "");
+                        IrisDimension loaded = data.getDimensionLoader().load(loadKey);
+                        if (loaded != null) {
+                            hostDimension = loaded;
                         }
                     }
                 }
@@ -394,11 +389,7 @@ public class CommandObject implements DirectorExecutor {
     private static List<TreePlausibilizeBatch.Target> resolveFromPacks(String target) {
         List<TreePlausibilizeBatch.Target> out = new ArrayList<>();
         File packsFolder = Iris.instance.getDataFolder("packs");
-        File[] packs = packsFolder.listFiles(File::isDirectory);
-        if (packs == null) {
-            return out;
-        }
-        for (File pack : packs) {
+        for (File pack : PackDirectoryResolver.listVisiblePackDirectories(packsFolder)) {
             File objectsRoot = new File(pack, "objects");
             if (!objectsRoot.isDirectory()) {
                 continue;

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandPack.java

@@ -52,8 +52,8 @@ public class CommandPack implements DirectorExecutor {
         }
 
         if (pack == null || pack.isBlank()) {
-            File[] dirs = packsRoot.listFiles(File::isDirectory);
-            if (dirs == null || dirs.length == 0) {
+            List<File> dirs = PackDirectoryResolver.listVisiblePackDirectories(packsRoot);
+            if (dirs.isEmpty()) {
                 s.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.COMMAND_PACK_NO_PACKS_VALIDATE));
                 return;
             }
@@ -64,7 +64,7 @@ public class CommandPack implements DirectorExecutor {
                     broken++;
                 }
             }
-            s.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.COMMAND_PACK_VALIDATION_COMPLETE_BROKEN_PACKS, MessageArgument.untrusted("broken", String.valueOf(broken)), MessageArgument.untrusted("value", String.valueOf(dirs.length))));
+            s.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.COMMAND_PACK_VALIDATION_COMPLETE_BROKEN_PACKS, MessageArgument.untrusted("broken", String.valueOf(broken)), MessageArgument.untrusted("value", String.valueOf(dirs.size()))));
             return;
         }
 

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandStructure.java

@@ -153,6 +153,11 @@ public class CommandStructure implements DirectorExecutor {
                 }
             }
         }
+        for (String placedKey : IrisStructureLocator.placedKeys(engine)) {
+            if (!structureKeys.contains(placedKey)) {
+                structureKeys.add(placedKey);
+            }
+        }
         VolmitSender commandSender = sender();
         Player target = senderIsPlayer ? player() : null;
         commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STRUCTURE_VERIFYING_STRUCTURES_FROM_WITHIN_CHUNKS, MessageArgument.untrusted("value", world.getName()), MessageArgument.untrusted("value2", center.getBlockX()), MessageArgument.untrusted("value3", center.getBlockZ()), MessageArgument.untrusted("searchRadius", searchRadius)));
@@ -169,7 +174,8 @@ public class CommandStructure implements DirectorExecutor {
         for (String keyName : structureKeys) {
             IrisNativeStructureDecision decision = NativeStructureGenerationPolicy.resolve(engine, keyName, false);
             decisions.put(keyName, decision);
-            requiresNativeReachability |= decision.generate();
+            requiresNativeReachability |= !IrisStructureLocator.isPlaced(engine, keyName)
+                    && decision.generate();
         }
         Set<String> reachable = Set.of();
         if (requiresNativeReachability) {
@@ -190,7 +196,7 @@ public class CommandStructure implements DirectorExecutor {
         int errors = 0;
         for (String keyName : structureKeys) {
             IrisNativeStructureDecision decision = decisions.get(keyName);
-            if (decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS) {
+            if (IrisStructureLocator.isPlaced(engine, keyName)) {
                 try {
                     IrisStructureLocator.LocateResult result =
                             IrisStructureLocator.locate(engine, keyName, centerX, centerZ, searchRadius);
@@ -205,7 +211,7 @@ public class CommandStructure implements DirectorExecutor {
                         continue;
                     }
                     located++;
-                    messages.add(C.AQUA + "[iris] " + C.WHITE + keyName + C.GREEN + " @ "
+                    messages.add(C.AQUA + "[iris-planned] " + C.WHITE + keyName + C.GREEN + " @ "
                             + result.originX() + "," + result.baseY() + "," + result.originZ());
                 } catch (Throwable error) {
                     errors++;
@@ -230,7 +236,7 @@ public class CommandStructure implements DirectorExecutor {
             nativeEligible++;
             messages.add(C.GREEN + "[native-eligible] " + C.WHITE + keyName);
         }
-        messages.add(C.GREEN + "Structure verify: " + C.WHITE + located + C.GREEN + " Iris placements located, "
+        messages.add(C.GREEN + "Structure verify: " + C.WHITE + located + C.GREEN + " Iris placement plans found, "
                 + C.WHITE + nativeEligible + C.GREEN + " native structures eligible, "
                 + C.WHITE + disabled + C.GREEN + " disabled by policy, "
                 + C.WHITE + unreachable + C.GREEN + " biome-unreachable, "

adapters/bukkit/plugin/src/main/java/art/arcane/iris/core/commands/CommandStudio.java

@@ -229,29 +229,21 @@ public class CommandStudio implements DirectorExecutor {
         }
     }
 
-    @Director(description = "Create a new studio project", descriptionKey = "iris.director.commandstudio.director.create_new_studio_project", aliases = "+", sync = true)
+    @Director(description = "Create a new studio project", descriptionKey = "iris.director.commandstudio.director.create_new_studio_project", aliases = "+")
     public void create(
             @Param(description = "The name of this new Iris Project.", descriptionKey = "iris.director.commandstudio.param.name_this_new_iris_project", defaultValue = "studio")
             String name,
             @Param(
                     description = "Copy the contents of an existing project in your packs folder and use it as a template in this new project.", descriptionKey = "iris.director.commandstudio.param.copy_contents_existing_project_your_packs_folder_use_it_as_template_this",
+                    defaultValue = "null",
                     contextual = true,
                     customHandler = NullableDimensionHandler.class
             )
             IrisDimension template) {
-        String projectName = name;
-        if (name.equals("studio")) {
-            File workspace = Iris.service(StudioSVC.class).getWorkspaceFolder();
-            int suffix = 2;
-            while (new File(workspace, projectName).exists()) {
-                projectName = "studio" + suffix++;
-            }
-        }
-
         if (template != null) {
-            Iris.service(StudioSVC.class).create(sender(), projectName, template.getLoadKey());
+            Iris.service(StudioSVC.class).create(sender(), name, template);
         } else {
-            Iris.service(StudioSVC.class).create(sender(), projectName);
+            Iris.service(StudioSVC.class).create(sender(), name);
         }
     }
 

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/BukkitWorldReconcilerTest.java

@@ -0,0 +1,362 @@
+package art.arcane.iris.core;
+
+import art.arcane.iris.core.lifecycle.BukkitWorldConfiguration;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
+import org.bukkit.NamespacedKey;
+import org.bukkit.World;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Proxy;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class BukkitWorldReconcilerTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void loadLeaseCoversRegistrationThroughExactWorldCompletion() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        LifecycleOperationCoordinator coordinator = coordinator();
+        FakeBackend backend = new FakeBackend();
+        CompletableFuture<World> creation = new CompletableFuture<>();
+        backend.creation = creation;
+        World exactWorld = world(backend.worldKey);
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator);
+
+        CompletableFuture<BukkitWorldReconciler.LoadResult> load = reconciler.loadWorld(configuration, backend.worldKey.toString());
+
+        assertFalse(load.isDone());
+        assertEquals(LifecycleOperationCoordinator.OperationKind.WORLD_LOAD,
+                coordinator.active(LifecycleOperationCoordinator.Domain.WORLD_MUTATION)
+                        .orElseThrow()
+                        .kind());
+        assertEquals("Iris:overworld", YamlConfiguration.loadConfiguration(configuration)
+                .getString("worlds.probe.generator"));
+        assertThrows(LifecycleOperationCoordinator.BusyException.class,
+                () -> coordinator.acquire(
+                        LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                        LifecycleOperationCoordinator.OperationKind.WORLD_REMOVE,
+                        backend.worldKey.toString()));
+
+        backend.loaded = Optional.of(exactWorld);
+        creation.complete(exactWorld);
+        BukkitWorldReconciler.LoadResult result = load.join();
+
+        assertTrue(result.succeeded());
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.LOADED, result.status());
+        assertEquals(BukkitWorldConfiguration.Registration.CREATED, result.registration());
+        assertFalse(result.rollbackAttempted());
+        assertTrue(coordinator.isIdle());
+    }
+
+    @Test
+    public void failedCreationRollsBackOnlyNewRegistration() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        FakeBackend backend = new FakeBackend();
+        backend.creation = CompletableFuture.failedFuture(new IllegalStateException("create failed"));
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler.loadWorld(configuration, backend.worldKey.toString()).join();
+
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.CREATE_FAILED, result.status());
+        assertEquals(BukkitWorldConfiguration.Registration.CREATED, result.registration());
+        assertTrue(result.rollbackAttempted());
+        assertTrue(result.rollbackSucceeded());
+        assertNull(YamlConfiguration.loadConfiguration(configuration).get("worlds.probe"));
+    }
+
+    @Test
+    public void failedCreationPreservesPreexistingMatchingRegistration() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        BukkitWorldConfiguration.register(configuration, "probe", "overworld", 1337L);
+        FakeBackend backend = new FakeBackend();
+        backend.configuredSeed = 1337L;
+        backend.creation = CompletableFuture.failedFuture(new IllegalStateException("create failed"));
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler.loadWorld(configuration, backend.worldKey.toString()).join();
+
+        assertEquals(BukkitWorldConfiguration.Registration.UNCHANGED, result.registration());
+        assertFalse(result.rollbackAttempted());
+        assertEquals("Iris:overworld", YamlConfiguration.loadConfiguration(configuration)
+                .getString("worlds.probe.generator"));
+        assertEquals(1337L, YamlConfiguration.loadConfiguration(configuration)
+                .getLong("worlds.probe.seed"));
+    }
+
+    @Test
+    public void rollbackDoesNotRemoveARegistrationChangedDuringCreation() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        FakeBackend backend = new FakeBackend();
+        CompletableFuture<World> creation = new CompletableFuture<>();
+        backend.creation = creation;
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+        CompletableFuture<BukkitWorldReconciler.LoadResult> load = reconciler
+                .loadWorld(configuration, backend.worldKey.toString());
+        YamlConfiguration changed = YamlConfiguration.loadConfiguration(configuration);
+        changed.set("worlds.probe.generator", "Other:generator");
+        changed.save(configuration);
+
+        creation.completeExceptionally(new IllegalStateException("create failed"));
+        BukkitWorldReconciler.LoadResult result = load.join();
+
+        assertTrue(result.rollbackAttempted());
+        assertFalse(result.rollbackSucceeded());
+        assertEquals("Other:generator", YamlConfiguration.loadConfiguration(configuration)
+                .getString("worlds.probe.generator"));
+    }
+
+    @Test
+    public void mismatchedCreatedWorldIsNotReportedAsLoaded() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        FakeBackend backend = new FakeBackend();
+        backend.creation = CompletableFuture.completedFuture(world(new NamespacedKey("iris", "other")));
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler.loadWorld(configuration, backend.worldKey.toString()).join();
+
+        assertFalse(result.succeeded());
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.IDENTITY_MISMATCH, result.status());
+        assertTrue(result.rollbackSucceeded());
+        assertNull(YamlConfiguration.loadConfiguration(configuration).get("worlds.probe"));
+    }
+
+    @Test
+    public void mismatchedResolvedWorldIsNotReportedAsLoaded() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        FakeBackend backend = new FakeBackend();
+        World exactCreatedWorld = world(backend.worldKey);
+        backend.creation = CompletableFuture.completedFuture(exactCreatedWorld);
+        backend.loaded = Optional.of(world(new NamespacedKey("iris", "other")));
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler
+                .loadWorld(configuration, backend.worldKey.toString())
+                .join();
+
+        assertFalse(result.succeeded());
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.IDENTITY_MISMATCH, result.status());
+        assertTrue(result.rollbackSucceeded());
+    }
+
+    @Test
+    public void exactNonIrisWorldIsAnIdentityConflict() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        FakeBackend backend = new FakeBackend();
+        backend.loaded = Optional.of(world(backend.worldKey));
+        backend.irisWorld = false;
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler.loadWorld(configuration, backend.worldKey.toString()).join();
+
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.IDENTITY_CONFLICT, result.status());
+        assertEquals(0, backend.createCount.get());
+        assertTrue(result.rollbackSucceeded());
+    }
+
+    @Test
+    public void unresolvedDimensionAndBusyLifecycleDoNotTouchConfiguration() throws Exception {
+        File unresolvedConfiguration = temporaryFolder.newFile("unresolved.yml");
+        FakeBackend unresolvedBackend = new FakeBackend();
+        unresolvedBackend.dimensionResolution = BukkitWorldReconciler.DimensionResolution.failed(
+                new IllegalStateException("ambiguous"));
+        BukkitWorldReconciler unresolved = new BukkitWorldReconciler(unresolvedBackend, coordinator());
+
+        BukkitWorldReconciler.LoadResult unresolvedResult = unresolved
+                .loadWorld(unresolvedConfiguration, unresolvedBackend.worldKey.toString())
+                .join();
+
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.DIMENSION_UNRESOLVED, unresolvedResult.status());
+        assertEquals(0L, unresolvedConfiguration.length());
+
+        File busyConfiguration = temporaryFolder.newFile("busy.yml");
+        LifecycleOperationCoordinator coordinator = coordinator();
+        LifecycleOperationCoordinator.Lease removal = coordinator.acquire(
+                LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                LifecycleOperationCoordinator.OperationKind.WORLD_REMOVE,
+                "iris:other");
+        FakeBackend busyBackend = new FakeBackend();
+        BukkitWorldReconciler busy = new BukkitWorldReconciler(busyBackend, coordinator);
+        try {
+            BukkitWorldReconciler.LoadResult busyResult = busy.loadWorld(busyConfiguration, busyBackend.worldKey.toString()).join();
+            assertEquals(BukkitWorldReconciler.ReconciliationStatus.BUSY, busyResult.status());
+            assertEquals(0, busyBackend.createCount.get());
+            assertEquals(0L, busyConfiguration.length());
+        } finally {
+            removal.close();
+        }
+    }
+
+    @Test
+    public void pendingRestartRefusesWorldLoadBeforeRegistration() throws Exception {
+        File configuration = temporaryFolder.newFile("bukkit.yml");
+        LifecycleOperationCoordinator coordinator = coordinator();
+        assertTrue(coordinator.quiesceForRestart(() -> {
+        }));
+        FakeBackend backend = new FakeBackend();
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator);
+
+        BukkitWorldReconciler.LoadResult result = reconciler.loadWorld(configuration, backend.worldKey.toString()).join();
+
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.BUSY, result.status());
+        assertEquals(LifecycleOperationCoordinator.OperationKind.SERVER_RESTART,
+                ((LifecycleOperationCoordinator.BusyException) result.failure()).operationKind());
+        assertEquals(0, backend.createCount.get());
+        assertEquals(0L, configuration.length());
+    }
+
+    @Test
+    public void terminalCreateTimeoutWinsOverLateWorldCompletion() {
+        NamespacedKey worldKey = new NamespacedKey("iris", "probe");
+        CompletableFuture<World> source = new CompletableFuture<>();
+        AtomicInteger timeoutActions = new AtomicInteger();
+
+        CompletableFuture<World> guarded = BukkitWorldReconciler.guardCreateCompletion(
+                source,
+                worldKey,
+                1L,
+                timeoutActions::incrementAndGet);
+
+        CompletionException failure = assertThrows(CompletionException.class, guarded::join);
+        assertTrue(failure.getCause() instanceof TimeoutException);
+        assertEquals(1, timeoutActions.get());
+        source.complete(world(worldKey));
+        assertTrue(guarded.isCompletedExceptionally());
+    }
+
+    @Test
+    public void timedOutCreationPreservesNewRegistrationForRestartReconciliation() throws Exception {
+        File configuration = temporaryFolder.newFile("timeout.yml");
+        FakeBackend backend = new FakeBackend();
+        backend.creation = CompletableFuture.failedFuture(new TimeoutException("create timed out"));
+        BukkitWorldReconciler reconciler = new BukkitWorldReconciler(backend, coordinator());
+
+        BukkitWorldReconciler.LoadResult result = reconciler
+                .loadWorld(configuration, backend.worldKey.toString())
+                .join();
+
+        assertEquals(BukkitWorldReconciler.ReconciliationStatus.RESTART_REQUIRED, result.status());
+        assertFalse(result.rollbackAttempted());
+        assertEquals("Iris:overworld", YamlConfiguration.loadConfiguration(configuration)
+                .getString("worlds.probe.generator"));
+    }
+
+    private static LifecycleOperationCoordinator coordinator() throws Exception {
+        Constructor<LifecycleOperationCoordinator> constructor = LifecycleOperationCoordinator.class
+                .getDeclaredConstructor();
+        constructor.setAccessible(true);
+        return constructor.newInstance();
+    }
+
+    private static World world(NamespacedKey worldKey) {
+        return (World) Proxy.newProxyInstance(
+                BukkitWorldReconcilerTest.class.getClassLoader(),
+                new Class[]{World.class},
+                (proxy, method, arguments) -> switch (method.getName()) {
+                    case "getKey" -> worldKey;
+                    case "getName" -> worldKey.getKey();
+                    case "hashCode" -> System.identityHashCode(proxy);
+                    case "equals" -> proxy == arguments[0];
+                    case "toString" -> worldKey.toString();
+                    default -> defaultValue(method.getReturnType());
+                });
+    }
+
+    private static Object defaultValue(Class<?> type) {
+        if (!type.isPrimitive()) {
+            return null;
+        }
+        if (type == boolean.class) {
+            return false;
+        }
+        if (type == char.class) {
+            return '\0';
+        }
+        if (type == byte.class) {
+            return (byte) 0;
+        }
+        if (type == short.class) {
+            return (short) 0;
+        }
+        if (type == int.class) {
+            return 0;
+        }
+        if (type == long.class) {
+            return 0L;
+        }
+        if (type == float.class) {
+            return 0F;
+        }
+        if (type == double.class) {
+            return 0D;
+        }
+        throw new IllegalStateException("Unsupported primitive type: " + type);
+    }
+
+    private static final class FakeBackend implements BukkitWorldReconciler.Backend {
+        private final NamespacedKey worldKey;
+        private final AtomicInteger createCount;
+        private CompletableFuture<World> creation;
+        private Optional<World> loaded;
+        private boolean irisWorld;
+        private Long configuredSeed;
+        private BukkitWorldReconciler.DimensionResolution dimensionResolution;
+
+        private FakeBackend() {
+            worldKey = new NamespacedKey("iris", "probe");
+            createCount = new AtomicInteger();
+            creation = CompletableFuture.completedFuture(null);
+            loaded = Optional.empty();
+            irisWorld = true;
+            configuredSeed = null;
+            dimensionResolution = BukkitWorldReconciler.DimensionResolution.resolved("overworld");
+        }
+
+        @Override
+        public Map<String, String> configuredWorlds() {
+            return Map.of("probe", "overworld");
+        }
+
+        @Override
+        public Long configuredSeed(String worldName) {
+            return configuredSeed;
+        }
+
+        @Override
+        public Optional<World> loadedWorld(NamespacedKey requestedWorldKey) {
+            return worldKey.equals(requestedWorldKey) ? loaded : Optional.empty();
+        }
+
+        @Override
+        public CompletableFuture<World> createWorld(NamespacedKey requestedWorldKey, String dimension, Long seed) {
+            createCount.incrementAndGet();
+            return creation;
+        }
+
+        @Override
+        public boolean isIrisWorld(World world) {
+            return irisWorld;
+        }
+
+        @Override
+        public BukkitWorldReconciler.DimensionResolution resolveDimension(NamespacedKey requestedWorldKey) {
+            return dimensionResolution;
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/PendingWorldDeleteQueueTest.java

@@ -0,0 +1,176 @@
+package art.arcane.iris.core;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class PendingWorldDeleteQueueTest {
+    private static final String QUARANTINE_NAME = ".iris-delete-6a4fd7fd-8e75-4f2f-b9fa-523b90c41f45";
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void acceptsOnlyCanonicalManagedNamesAndStrictQuarantines() {
+        assertEquals("alpha", PendingWorldDeleteQueue.normalizeQueueEntry("alpha", "world"));
+        assertEquals("alpha", PendingWorldDeleteQueue.normalizeQueueEntry("iris:alpha", "world"));
+        assertEquals(QUARANTINE_NAME, PendingWorldDeleteQueue.normalizeQueueEntry(QUARANTINE_NAME, "world"));
+
+        for (String rejected : List.of(
+                "world",
+                "world_nether",
+                "world_the_end",
+                "overworld",
+                "the_nether",
+                "the_end",
+                "minecraft:overworld",
+                "minecraft:the_nether",
+                "minecraft:the_end",
+                "Alpha",
+                "alpha beta",
+                "../alpha",
+                "alpha/beta",
+                ".iris-delete-6a4fd7fd-8e75-4f2f-b9fa-523b90c41f4",
+                ".iris-delete-6A4FD7FD-8E75-4F2F-B9FA-523B90C41F45"
+        )) {
+            assertNull(rejected, PendingWorldDeleteQueue.normalizeQueueEntry(rejected, "world"));
+        }
+    }
+
+    @Test
+    public void loadFiltersUnsafeEntriesAndCanonicalizesDuplicates() throws IOException {
+        File queueFile = temporaryFolder.newFile("pending-world-deletes.txt");
+        Files.writeString(
+                queueFile.toPath(),
+                String.join("\n", "alpha", "iris:alpha", "world", "../escape", QUARANTINE_NAME),
+                StandardCharsets.UTF_8
+        );
+
+        LinkedHashMap<String, String> queue = PendingWorldDeleteQueue.loadPendingWorldDeleteMap(queueFile, "world");
+
+        assertEquals(List.of("alpha", QUARANTINE_NAME), List.copyOf(queue.values()));
+    }
+
+    @Test
+    public void queueFileReplacementIsCompleteAndLeavesNoTemporaryFile() throws IOException {
+        File queueFile = new File(temporaryFolder.getRoot(), "state/pending-world-deletes.txt");
+        LinkedHashMap<String, String> first = new LinkedHashMap<>();
+        first.put("alpha", "alpha");
+        first.put(QUARANTINE_NAME, QUARANTINE_NAME);
+        PendingWorldDeleteQueue.writePendingWorldDeleteMap(queueFile, first);
+
+        assertEquals("alpha\n" + QUARANTINE_NAME + "\n", Files.readString(queueFile.toPath()));
+
+        LinkedHashMap<String, String> replacement = new LinkedHashMap<>();
+        replacement.put("beta", "beta");
+        PendingWorldDeleteQueue.writePendingWorldDeleteMap(queueFile, replacement);
+
+        assertEquals("beta\n", Files.readString(queueFile.toPath()));
+        try (Stream<Path> files = Files.list(queueFile.toPath().getParent())) {
+            assertFalse(files.anyMatch(path -> path.getFileName().toString().contains(".tmp-")));
+        }
+    }
+
+    @Test
+    public void emptyQueueIsDurablyRepresentedByAnEmptyFile() throws IOException {
+        File queueFile = new File(temporaryFolder.getRoot(), "pending-world-deletes.txt");
+
+        PendingWorldDeleteQueue.writePendingWorldDeleteMap(queueFile, new LinkedHashMap<>());
+
+        assertTrue(queueFile.isFile());
+        assertEquals(0L, queueFile.length());
+    }
+
+    @Test
+    public void writeFailuresPropagateToTheCaller() throws IOException {
+        File parentFile = temporaryFolder.newFile("not-a-directory");
+        File queueFile = new File(parentFile, "pending-world-deletes.txt");
+
+        assertThrows(
+                IOException.class,
+                () -> PendingWorldDeleteQueue.writePendingWorldDeleteMap(queueFile, new LinkedHashMap<>())
+        );
+    }
+
+    @Test
+    public void discoversOnlyDirectNonSymlinkStartupDirectories() throws IOException {
+        File levelRoot = temporaryFolder.newFolder("world");
+        Path irisNamespace = levelRoot.toPath().resolve("dimensions/iris");
+        Files.createDirectories(irisNamespace);
+        Files.createDirectory(irisNamespace.resolve(QUARANTINE_NAME));
+        Files.createDirectory(irisNamespace.resolve(".iris-delete-not-a-uuid"));
+        String transientName = "iris-45ba411e-bf7c-493a-bf41-aa020754990b";
+        Files.createDirectory(irisNamespace.resolve(transientName + "_nether"));
+        Path nested = irisNamespace.resolve("ordinary/nested");
+        Files.createDirectories(nested);
+        Files.createDirectory(nested.resolve(".iris-delete-f70b8c21-9174-43a2-b7b7-a84fc0b2fe4a"));
+        Path symlinkTarget = temporaryFolder.newFolder("quarantine-target").toPath();
+        Files.createSymbolicLink(
+                irisNamespace.resolve(".iris-delete-b8c7ff2d-2efd-410d-b228-6da5d5a46c36"),
+                symlinkTarget
+        );
+
+        LinkedHashSet<String> discovered = PendingWorldDeleteQueue.discoverStartupWorldNames(levelRoot);
+
+        assertEquals(Set.of(QUARANTINE_NAME, transientName), discovered);
+    }
+
+    @Test
+    public void refusesSymlinkedIrisNamespace() throws IOException {
+        File levelRoot = temporaryFolder.newFolder("world");
+        Path dimensions = levelRoot.toPath().resolve("dimensions");
+        Files.createDirectories(dimensions);
+        Path external = temporaryFolder.newFolder("external-iris").toPath();
+        Files.createSymbolicLink(dimensions.resolve("iris"), external);
+
+        assertThrows(
+                IOException.class,
+                () -> PendingWorldDeleteQueue.discoverStartupWorldNames(levelRoot)
+        );
+    }
+
+    @Test
+    public void quarantineEntriesResolveToOnlyTheirExactDirectory() throws IOException {
+        File levelRoot = temporaryFolder.newFolder("world");
+
+        List<Path> paths = PendingWorldDeleteQueue.resolveQueueEntryPaths(levelRoot, QUARANTINE_NAME);
+
+        assertEquals(List.of(
+                levelRoot.toPath().resolve("dimensions/iris").resolve(QUARANTINE_NAME).toAbsolutePath()
+        ), paths);
+    }
+
+    @Test
+    public void exactLogicalEntriesDoNotExpandIntoDimensionFamilies() throws IOException {
+        File levelRoot = temporaryFolder.newFolder("world");
+
+        List<Path> exact = PendingWorldDeleteQueue.resolveQueueEntryPaths(levelRoot, "exact:alpha");
+        List<Path> family = PendingWorldDeleteQueue.resolveQueueEntryPaths(levelRoot, "alpha");
+
+        assertEquals(List.of(
+                levelRoot.toPath().resolve("dimensions/iris/alpha").toAbsolutePath()
+        ), exact);
+        assertEquals(List.of(
+                levelRoot.toPath().resolve("dimensions/iris/alpha").toAbsolutePath(),
+                levelRoot.toPath().resolve("dimensions/iris/alpha_nether").toAbsolutePath(),
+                levelRoot.toPath().resolve("dimensions/iris/alpha_the_end").toAbsolutePath()
+        ), family);
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/CommandIrisLoadWorldContractTest.java

@@ -0,0 +1,47 @@
+package art.arcane.iris.core.commands;
+
+import art.arcane.iris.core.BukkitWorldReconciler;
+import art.arcane.volmlib.util.director.annotations.Param;
+import org.junit.Test;
+
+import java.io.File;
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.concurrent.CompletableFuture;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class CommandIrisLoadWorldContractTest {
+    @Test
+    public void commandUsesTypedAsyncReconciliationBeforeReportingSuccess() throws Exception {
+        Method reconciliation = BukkitWorldReconciler.class.getDeclaredMethod(
+                "loadWorld",
+                File.class,
+                String.class);
+        assertEquals(CompletableFuture.class, reconciliation.getReturnType());
+        Method commandMethod = CommandIris.class.getDeclaredMethod("loadWorld", String.class);
+        Parameter worldParameter = commandMethod.getParameters()[0];
+        assertEquals(CommandIris.ManagedWorldNameHandler.class,
+                worldParameter.getAnnotation(Param.class).customHandler());
+
+        String source = Files.readString(Path.of(System.getProperty("iris.commandIrisSource")));
+        String command = source.substring(
+                source.indexOf("public void loadWorld("),
+                source.indexOf("private void reportLoadWorldResult("));
+        String reporter = source.substring(
+                source.indexOf("private void reportLoadWorldResult("),
+                source.indexOf("@Director(description = \"Evacuate an iris world\""));
+
+        assertTrue(command.contains("IrisWorldStorage.managedKeyFromName(world)"));
+        assertTrue(command.contains(".loadWorld(BUKKIT_YML, worldKey.toString())"));
+        assertTrue(command.contains(".whenComplete((result, failure) ->"));
+        assertFalse(command.contains("checkForBukkitWorlds"));
+        assertFalse(command.contains("COMMAND_IRIS_LOADED_SUCCESSFULLY"));
+        assertTrue(reporter.contains("if (result.succeeded())"));
+        assertTrue(reporter.contains("COMMAND_IRIS_LOADED_SUCCESSFULLY"));
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/CommandIrisMainWorldPromotionTest.java

@@ -0,0 +1,93 @@
+package art.arcane.iris.core.commands;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.IOException;
+import java.nio.file.FileAlreadyExistsException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class CommandIrisMainWorldPromotionTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void existingTopLevelWorldIsRefusedWithoutMerging() throws IOException {
+        PromotionPaths paths = createPromotionPaths("existing-target");
+        Files.createDirectories(paths.target());
+        Files.writeString(paths.target().resolve("sentinel.txt"), "keep");
+
+        assertThrows(FileAlreadyExistsException.class, () -> CommandIris.publishMainWorldFiles(
+                paths.current(),
+                paths.sourceDimension(),
+                paths.target()
+        ));
+
+        assertEquals("keep", Files.readString(paths.target().resolve("sentinel.txt")));
+        assertFalse(Files.exists(paths.target().resolve("dimensions/minecraft/overworld/region/r.0.0.mca")));
+        assertFalse(hasPromotionStage(paths.root(), paths.target().getFileName().toString()));
+    }
+
+    @Test
+    public void uncommittedPromotionRollsBackThePublishedWorld() throws IOException {
+        PromotionPaths paths = createPromotionPaths("rollback-target");
+
+        try (CommandIris.MainWorldPublication publication = CommandIris.publishMainWorldFiles(
+                paths.current(),
+                paths.sourceDimension(),
+                paths.target()
+        )) {
+            assertTrue(Files.isRegularFile(paths.target().resolve("data/map.dat")));
+            assertTrue(Files.isRegularFile(paths.target().resolve("dimensions/minecraft/overworld/region/r.0.0.mca")));
+        }
+
+        assertFalse(Files.exists(paths.target()));
+        assertFalse(hasPromotionStage(paths.root(), paths.target().getFileName().toString()));
+    }
+
+    @Test
+    public void committedPromotionKeepsTheCompleteStagedWorld() throws IOException {
+        PromotionPaths paths = createPromotionPaths("committed-target");
+
+        try (CommandIris.MainWorldPublication publication = CommandIris.publishMainWorldFiles(
+                paths.current(),
+                paths.sourceDimension(),
+                paths.target()
+        )) {
+            publication.commit();
+        }
+
+        assertEquals("map", Files.readString(paths.target().resolve("data/map.dat")));
+        assertEquals("region", Files.readString(paths.target().resolve("dimensions/minecraft/overworld/region/r.0.0.mca")));
+        assertFalse(hasPromotionStage(paths.root(), paths.target().getFileName().toString()));
+    }
+
+    private PromotionPaths createPromotionPaths(String targetName) throws IOException {
+        Path root = temporaryFolder.newFolder(targetName + "-root").toPath();
+        Path current = root.resolve("world");
+        Path sourceDimension = current.resolve("dimensions/iris/" + targetName);
+        Path target = root.resolve(targetName);
+        Files.createDirectories(current.resolve("data"));
+        Files.writeString(current.resolve("data/map.dat"), "map");
+        Files.createDirectories(sourceDimension.resolve("region"));
+        Files.writeString(sourceDimension.resolve("region/r.0.0.mca"), "region");
+        return new PromotionPaths(root, current, sourceDimension, target);
+    }
+
+    private boolean hasPromotionStage(Path root, String targetName) throws IOException {
+        try (Stream<Path> entries = Files.list(root)) {
+            return entries.anyMatch(path -> path.getFileName().toString().startsWith("." + targetName + ".promoting-"));
+        }
+    }
+
+    private record PromotionPaths(Path root, Path current, Path sourceDimension, Path target) {
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/CommandIrisRemovalCommandContractTest.java

@@ -0,0 +1,27 @@
+package art.arcane.iris.core.commands;
+
+import art.arcane.volmlib.util.director.annotations.Param;
+import org.bukkit.World;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class CommandIrisRemovalCommandContractTest {
+    @Test
+    public void removalAcceptsDiskOnlyNamesAndUsesManagedSuggestions() throws NoSuchMethodException {
+        Method command = CommandIris.class.getDeclaredMethod("remove", String.class, boolean.class);
+        Parameter worldParameter = command.getParameters()[0];
+        Param world = worldParameter.getAnnotation(Param.class);
+
+        assertEquals(CommandIris.ManagedWorldNameHandler.class, world.customHandler());
+        assertFalse(Arrays.stream(CommandIris.class.getDeclaredMethods())
+                .anyMatch(method -> method.getName().equals("remove")
+                        && method.getParameterCount() == 2
+                        && method.getParameterTypes()[0] == World.class));
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/CommandIrisUnloadContractTest.java

@@ -0,0 +1,26 @@
+package art.arcane.iris.core.commands;
+
+import org.junit.Test;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertTrue;
+
+public class CommandIrisUnloadContractTest {
+    @Test
+    public void unloadAwaitsEvacuationAndHasATerminalLifecycleTimeout() throws Exception {
+        String source = Files.readString(Path.of(System.getProperty("iris.commandIrisSource")));
+        String command = source.substring(
+                source.indexOf("public void unloadWorld("),
+                source.indexOf("private void reportUnloadResult("));
+
+        assertTrue(command.contains("IrisToolbelt.evacuateAsync(world)"));
+        assertTrue(command.indexOf("IrisToolbelt.evacuateAsync(world)")
+                < command.indexOf("WorldLifecycleService.get().unloadAsync(world, true)"));
+        assertTrue(command.contains("guardUnloadCompletion(sequence, terminalTimeout, world.getName())"));
+        assertTrue(command.contains("ServerConfigurator.restart(\"World unload timed out"));
+        assertTrue(command.indexOf("ServerConfigurator.restart(\"World unload timed out")
+                < command.indexOf("guarded.completeExceptionally(timeout)"));
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/CommandStudioCreationContractTest.java

@@ -0,0 +1,27 @@
+package art.arcane.iris.core.commands;
+
+import art.arcane.iris.engine.object.IrisDimension;
+import art.arcane.iris.util.common.director.specialhandlers.NullableDimensionHandler;
+import art.arcane.volmlib.util.director.annotations.Director;
+import art.arcane.volmlib.util.director.annotations.Param;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class CommandStudioCreationContractTest {
+    @Test
+    public void createRunsAsynchronouslyAndTemplateIsOptional() throws NoSuchMethodException {
+        Method command = CommandStudio.class.getDeclaredMethod("create", String.class, IrisDimension.class);
+        Director director = command.getAnnotation(Director.class);
+        Parameter templateParameter = command.getParameters()[1];
+        Param template = templateParameter.getAnnotation(Param.class);
+
+        assertFalse(director.sync());
+        assertEquals("null", template.defaultValue());
+        assertEquals(NullableDimensionHandler.class, template.customHandler());
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/core/commands/IrisStructureLocateCommandContractTest.java

@@ -25,7 +25,7 @@ public class IrisStructureLocateCommandContractTest {
     }
 
     @Test
-    public void findRoutesOnlyExplicitNativeReplacementThroughIrisLocate() throws IOException {
+    public void findRoutesRegisteredReplacementThroughPersistedNativeLocate() throws IOException {
         String source = Files.readString(Path.of(System.getProperty("iris.commandFindSource")));
         int methodStart = source.indexOf("public void structure(");
         int methodEnd = source.indexOf("private static Structure resolveNativeStructure", methodStart);
@@ -34,16 +34,19 @@ public class IrisStructureLocateCommandContractTest {
         int policyResolution = method.indexOf("NativeStructureGenerationPolicy.resolve(", nativeResolution);
         int replacementCheck = method.indexOf(
                 "decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS", policyResolution);
-        int replacementLocate = method.indexOf("locateIrisStructure(e, structureKey, commandSender)", replacementCheck);
         int genericIrisLookup = method.indexOf(
-                "nativeStructure == null && IrisStructureLocator.isPlaced(e, structureKey)", replacementLocate);
+                "nativeStructure == null && IrisStructureLocator.isPlaced(e, structureKey)", replacementCheck);
+        int replacementLocate = method.indexOf("final boolean replacementLocate = irisReplacement", genericIrisLookup);
         int nativeLocate = method.indexOf("targetWorld.locateNearestStructure(", genericIrisLookup);
         assertTrue(nativeResolution >= 0);
         assertTrue(policyResolution > nativeResolution);
         assertTrue(replacementCheck > policyResolution);
-        assertTrue(replacementLocate > replacementCheck);
-        assertTrue(genericIrisLookup > replacementLocate);
+        assertTrue(genericIrisLookup > replacementCheck);
+        assertTrue(replacementLocate > genericIrisLookup);
         assertTrue(nativeLocate > policyResolution);
+        assertTrue(method.contains("irisReplacement && !IrisStructureLocator.hasNativePlacement"));
+        assertTrue(method.contains("!replacementLocate && !explicitNativePlacement"));
+        assertTrue(method.contains("&& !StructureReachability.isReachable"));
         assertTrue(method.contains("decision.status() != NativeStructureGenerationStatus.REPLACED_BY_IRIS"));
         assertFalse(method.contains("NativeStructureLocateCapability"));
     }
@@ -82,7 +85,8 @@ public class IrisStructureLocateCommandContractTest {
         int methodEnd = source.indexOf("private void sendVerificationMessages(", methodStart);
         String method = source.substring(methodStart, methodEnd);
         int policyResolution = method.indexOf("NativeStructureGenerationPolicy.resolve(engine, keyName, false)");
-        int nativeRequirement = method.indexOf("requiresNativeReachability |= decision.generate()", policyResolution);
+        int nativeRequirement = method.indexOf(
+                "requiresNativeReachability |= !IrisStructureLocator.isPlaced", policyResolution);
         int reachabilityGuard = method.indexOf("if (requiresNativeReachability)", nativeRequirement);
         int reachabilityLookup = method.indexOf("StructureReachability.reachableKeys(engine)", reachabilityGuard);
 

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/ForcedStructureChunkGenerator.java

@@ -10,8 +10,6 @@ import net.minecraft.world.level.StructureManager;
 import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.biome.BiomeManager;
 import net.minecraft.world.level.biome.FixedBiomeSource;
-import net.minecraft.world.level.block.Blocks;
-import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.minecraft.world.level.levelgen.Heightmap;
@@ -22,16 +20,11 @@ import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
 final class ForcedStructureChunkGenerator extends ChunkGenerator {
-    private static final int MIN_SAFE_STRUCTURE_Y = 80;
-    private static final int VERTICAL_MARGIN = 32;
-
     private final ChunkGenerator delegate;
-    private final int targetY;
 
-    ForcedStructureChunkGenerator(ChunkGenerator delegate, Holder<Biome> sourceBiome, int targetY) {
+    ForcedStructureChunkGenerator(ChunkGenerator delegate, Holder<Biome> sourceBiome) {
         super(new FixedBiomeSource(sourceBiome));
         this.delegate = delegate;
-        this.targetY = targetY;
     }
 
     @Override
@@ -72,7 +65,7 @@ final class ForcedStructureChunkGenerator extends ChunkGenerator {
 
     @Override
     public int getSeaLevel() {
-        return delegate.getMinY() + 1;
+        return delegate.getSeaLevel();
     }
 
     @Override
@@ -83,21 +76,13 @@ final class ForcedStructureChunkGenerator extends ChunkGenerator {
     @Override
     public int getBaseHeight(int x, int z, Heightmap.Types type,
                              LevelHeightAccessor heightAccessor, RandomState randomState) {
-        return safeOccupiedY(heightAccessor) + 1;
+        return delegate.getBaseHeight(x, z, type, heightAccessor, randomState);
     }
 
     @Override
     public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor heightAccessor,
                                      RandomState randomState) {
-        int minY = heightAccessor.getMinY();
-        BlockState[] states = new BlockState[heightAccessor.getHeight()];
-        for (int index = 0; index < states.length; index++) {
-            int y = minY + index;
-            states[index] = (y & 1) == 0
-                    ? Blocks.STONE.defaultBlockState()
-                    : Blocks.AIR.defaultBlockState();
-        }
-        return new NoiseColumn(minY, states);
+        return delegate.getBaseColumn(x, z, heightAccessor, randomState);
     }
 
     @Override
@@ -106,13 +91,4 @@ final class ForcedStructureChunkGenerator extends ChunkGenerator {
         delegate.addDebugScreenInfo(result, randomState, feetPos);
     }
 
-    private int safeOccupiedY(LevelHeightAccessor heightAccessor) {
-        int minY = heightAccessor.getMinY() + VERTICAL_MARGIN;
-        int maxY = heightAccessor.getMaxY() - VERTICAL_MARGIN;
-        if (minY > maxY) {
-            return heightAccessor.getMinY()
-                    + Math.max(0, heightAccessor.getHeight() / 2);
-        }
-        return Math.max(minY, Math.min(maxY, Math.max(MIN_SAFE_STRUCTURE_Y, targetY)));
-    }
 }

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureFactory.java

@@ -4,6 +4,7 @@ import art.arcane.iris.engine.framework.NativeStructureStartPlan;
 import art.arcane.iris.engine.object.IrisJigsawConfiguration;
 import art.arcane.iris.engine.object.IrisJigsawHeightmap;
 import art.arcane.iris.engine.object.IrisJigsawLiquidSettings;
+import art.arcane.iris.spi.PlatformStructureHooks.JigsawSourceMetadata;
 import net.minecraft.core.Holder;
 import net.minecraft.core.RegistryAccess;
 import net.minecraft.nbt.CompoundTag;
@@ -18,6 +19,7 @@ import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.biome.BiomeSource;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.structures.JigsawStructure;
@@ -43,7 +45,7 @@ public final class NativeStructureFactory {
                 .orElseThrow(() -> new IllegalStateException("Configured native structure '"
                         + plan.source().getStructure() + "' has no usable generation biome"));
         ChunkGenerator forcedGenerator = new ForcedStructureChunkGenerator(
-                context.generator(), sourceBiome, plan.baseY());
+                context.generator(), sourceBiome);
         StructureStart generated = configured.generate(
                 sourceHolder,
                 context.levelKey(),
@@ -82,15 +84,41 @@ public final class NativeStructureFactory {
         if (!positioned.isValid()) {
             return StructureStart.INVALID_START;
         }
-        return NativeStructureReferenceEnvelope.wrap(
+        return NativeStructureReferenceEnvelope.wrapForPublication(
                 positioned,
                 source,
                 references,
-                context.templateManager(),
-                plan.placement().resolvedTerrain()
+                plan.placement().resolvedTerrain(),
+                plan.source().getStructure()
         );
     }
 
+    public static JigsawSourceMetadata sourceMetadata(RegistryAccess registryAccess,
+                                                       StructureTemplateManager templateManager,
+                                                       JigsawStructure source) {
+        CompoundTag sourceTag = encodeJigsaw(registryAccess, source);
+        return new JigsawSourceMetadata(
+                sourceDistance(sourceTag, "horizontal"),
+                horizontalReferenceExpansion(source),
+                NativeStructureTemplatePoolBounds.sourceHorizontalSpan(
+                        registryAccess, templateManager, source));
+    }
+
+    public static int templatePoolHorizontalSpan(RegistryAccess registryAccess,
+                                                 StructureTemplateManager templateManager,
+                                                 String templatePoolKey) {
+        return NativeStructureTemplatePoolBounds.horizontalSpan(
+                registryAccess, templateManager, templatePoolKey);
+    }
+
+    public static int jigsawStartPoolHorizontalSpan(RegistryAccess registryAccess,
+                                                    StructureTemplateManager templateManager,
+                                                    JigsawStructure source,
+                                                    String templatePoolKey) {
+        return NativeStructureTemplatePoolBounds.horizontalSpan(
+                registryAccess, templateManager, source, templatePoolKey);
+    }
+
     static Structure configure(RegistryAccess registryAccess, Structure source,
                                IrisJigsawConfiguration configuration,
                                boolean underground, int baseY) {
@@ -103,10 +131,7 @@ public final class NativeStructureFactory {
             return source;
         }
         RegistryOps<Tag> registryOps = RegistryOps.create(NbtOps.INSTANCE, registryAccess);
-        Tag encoded = Structure.DIRECT_CODEC.encodeStart(registryOps, sourceJigsaw).getOrThrow();
-        if (!(encoded instanceof CompoundTag structureTag)) {
-            throw new IllegalStateException("Native jigsaw codec did not produce a compound");
-        }
+        CompoundTag structureTag = encodeJigsaw(registryOps, sourceJigsaw);
         CompoundTag configuredTag = structureTag.copy();
         if (underground) {
             CompoundTag height = new CompoundTag();
@@ -123,6 +148,20 @@ public final class NativeStructureFactory {
         return configured;
     }
 
+    private static CompoundTag encodeJigsaw(RegistryAccess registryAccess,
+                                             JigsawStructure source) {
+        return encodeJigsaw(RegistryOps.create(NbtOps.INSTANCE, registryAccess), source);
+    }
+
+    private static CompoundTag encodeJigsaw(RegistryOps<Tag> registryOps,
+                                             JigsawStructure source) {
+        Tag encoded = Structure.DIRECT_CODEC.encodeStart(registryOps, source).getOrThrow();
+        if (!(encoded instanceof CompoundTag structureTag)) {
+            throw new IllegalStateException("Native jigsaw codec did not produce a compound");
+        }
+        return structureTag;
+    }
+
     private static void applyConfiguration(CompoundTag tag, IrisJigsawConfiguration configuration) {
         if (configuration == null) {
             return;
@@ -168,7 +207,7 @@ public final class NativeStructureFactory {
         tag.put("max_distance_from_center", distance);
     }
 
-    private static int sourceDistance(CompoundTag tag, String axis) {
+    static int sourceDistance(CompoundTag tag, String axis) {
         Tag raw = tag.get("max_distance_from_center");
         if (raw instanceof CompoundTag compound) {
             return compound.getIntOr(axis, 128);
@@ -176,6 +215,14 @@ public final class NativeStructureFactory {
         return tag.getIntOr("max_distance_from_center", 128);
     }
 
+    static int horizontalReferenceExpansion(Structure structure) {
+        BoundingBox content = new BoundingBox(0, 0, 0, 0, 0, 0);
+        BoundingBox adjusted = structure.adjustBoundingBox(content);
+        int expansion = Math.max(content.minX() - adjusted.minX(), adjusted.maxX() - content.maxX());
+        expansion = Math.max(expansion, content.minZ() - adjusted.minZ());
+        return Math.max(0, Math.max(expansion, adjusted.maxZ() - content.maxZ()));
+    }
+
     private static void applyHeightmap(CompoundTag tag, IrisJigsawHeightmap heightmap) {
         if (heightmap == null || heightmap == IrisJigsawHeightmap.SOURCE) {
             return;

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureFoundationBuilder.java

@@ -60,9 +60,6 @@ public final class NativeStructureFoundationBuilder {
     private static void markFoundationEnvelope(BitSet envelope, List<StructurePiece> pieces, BoundingBox area,
                                                int x, int z) {
         for (StructurePiece piece : pieces) {
-            if (NativeStructureReferenceEnvelope.isMarker(piece)) {
-                continue;
-            }
             BoundingBox bounds = piece.getBoundingBox();
             if (x < bounds.minX() || x > bounds.maxX() || z < bounds.minZ() || z > bounds.maxZ()) {
                 continue;

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureLocatePersistence.java

@@ -0,0 +1,351 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.IrisStructureLocator;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.spi.IrisLogging;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.NbtUtils;
+import net.minecraft.nbt.StreamTagVisitor;
+import net.minecraft.nbt.Tag;
+import net.minecraft.nbt.visitors.CollectFields;
+import net.minecraft.nbt.visitors.FieldSelector;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.datafix.DataFixTypes;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.storage.SimpleRegionStorage;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+
+public final class NativeStructureLocatePersistence {
+    public static final int MAX_SELECTED_CANDIDATE_RETRIES = 64;
+    private static final int MAX_STORAGE_PROBES = 512;
+    private static final Method PAPER_LEVEL_TYPE_KEY = paperLevelTypeKey();
+
+    private NativeStructureLocatePersistence() {
+    }
+
+    public static Probe probe(ServerLevel level, Structure structure, boolean requireUnreferenced) {
+        return probe(level, structure, requireUnreferenced, new ProbeBudget(MAX_STORAGE_PROBES));
+    }
+
+    public static ProbeBudget probeBudget() {
+        return new ProbeBudget(MAX_STORAGE_PROBES);
+    }
+
+    public static Probe probe(ServerLevel level, Structure structure, boolean requireUnreferenced,
+                              ProbeBudget budget) {
+        return new Probe(level, structure, requireUnreferenced, budget);
+    }
+
+    public static Search search(Engine engine, String structureKey,
+                                int blockX, int blockZ, int radius, Probe probe) {
+        return new Search(engine, structureKey, blockX, blockZ, radius, probe);
+    }
+
+    public static final class Probe {
+        private final ServerLevel level;
+        private final Structure structure;
+        private final String structureKey;
+        private final boolean requireUnreferenced;
+        private final ProbeBudget budget;
+        private final Map<Long, Boolean> storedDecisions = new HashMap<>();
+
+        Probe(ServerLevel level, Structure structure, boolean requireUnreferenced,
+              ProbeBudget budget) {
+            this.level = level;
+            this.structure = structure;
+            Registry<Structure> registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+            Identifier identifier = registry.getKey(structure);
+            if (identifier == null) {
+                throw new IllegalStateException("Cannot probe an unregistered native structure");
+            }
+            this.structureKey = identifier.toString();
+            this.requireUnreferenced = requireUnreferenced;
+            this.budget = budget;
+        }
+
+        public boolean accepts(int chunkX, int chunkZ) {
+            ChunkAccess loaded = level.getChunkSource().getChunk(
+                    chunkX, chunkZ, ChunkStatus.STRUCTURE_STARTS, false);
+            if (loaded != null) {
+                StructureStart start = loaded.getStartForStructure(structure);
+                return start != null && start.isValid()
+                        && (!requireUnreferenced || start.canBeReferenced());
+            }
+
+            ChunkPos chunkPos = new ChunkPos(chunkX, chunkZ);
+            Boolean storedDecision = storedDecisions.get(chunkPos.pack());
+            if (storedDecision != null) {
+                return storedDecision;
+            }
+            boolean accepted = budget.acceptsStored(
+                    level, chunkPos, structureKey, requireUnreferenced);
+            storedDecisions.put(chunkPos.pack(), accepted);
+            return accepted;
+        }
+
+        public StructureStart verifySelected(int chunkX, int chunkZ) {
+            ChunkAccess chunk = level.getChunk(chunkX, chunkZ, ChunkStatus.STRUCTURE_STARTS);
+            StructureStart start = chunk.getStartForStructure(structure);
+            if (start == null || !start.isValid()) {
+                return null;
+            }
+            if (requireUnreferenced) {
+                if (!start.canBeReferenced()) {
+                    return null;
+                }
+            }
+            return start;
+        }
+
+        private void reference(StructureStart start) {
+            if (requireUnreferenced) {
+                level.structureManager().addReference(start);
+            }
+        }
+    }
+
+    public static final class ProbeBudget {
+        private final int maximum;
+        private final Map<Long, StoredChunkState> storedChunks = new HashMap<>();
+        private final ChunkStorageScanner scanner;
+        private final StoredChunkDatafixer datafixer;
+        private int used;
+        private boolean scanFailureReported;
+
+        private ProbeBudget(int maximum) {
+            this(maximum, null, ProbeBudget::datafix);
+        }
+
+        ProbeBudget(int maximum, ChunkStorageScanner scanner) {
+            this(maximum, scanner, ProbeBudget::datafix);
+        }
+
+        ProbeBudget(int maximum, ChunkStorageScanner scanner,
+                    StoredChunkDatafixer datafixer) {
+            this.maximum = maximum;
+            this.scanner = scanner;
+            this.datafixer = Objects.requireNonNull(
+                    datafixer, "Stored chunk datafixer must not be null");
+        }
+
+        private void claim() {
+            if (used >= maximum) {
+                throw new IrisStructureLocator.CandidateSearchLimitException();
+            }
+            used++;
+        }
+
+        private StoredChunkState storedState(ServerLevel level, ChunkPos chunkPos) {
+            StoredChunkState cached = storedChunks.get(chunkPos.pack());
+            if (cached != null) {
+                return cached;
+            }
+            claim();
+            CollectFields fields = new CollectFields(
+                    new FieldSelector(IntTag.TYPE, "DataVersion"),
+                    new FieldSelector("Level", "Structures", CompoundTag.TYPE, "Starts"),
+                    new FieldSelector("structures", CompoundTag.TYPE, "starts"));
+            ChunkStorageScanner activeScanner = scanner == null
+                    ? level.getChunkSource().chunkMap.chunkScanner()::scanChunk : scanner;
+            try {
+                activeScanner.scan(chunkPos, fields).join();
+            } catch (RuntimeException error) {
+                if (!scanFailureReported) {
+                    scanFailureReported = true;
+                    IrisLogging.reportError(
+                            "Native structure locate could not scan stored chunk state; candidates will be verified by loading their structure starts.",
+                            error);
+                }
+                StoredChunkState unresolved = StoredChunkState.missing();
+                storedChunks.put(chunkPos.pack(), unresolved);
+                return unresolved;
+            }
+            Tag result = fields.getResult();
+            StoredChunkState resolved;
+            try {
+                resolved = result instanceof CompoundTag storedChunk
+                        ? StoredChunkState.parse(datafixer.datafix(level, storedChunk))
+                        : StoredChunkState.missing();
+            } catch (RuntimeException error) {
+                if (!scanFailureReported) {
+                    scanFailureReported = true;
+                    IrisLogging.reportError(
+                            "Native structure locate could not datafix stored chunk state; candidates will be verified by loading their structure starts.",
+                            error);
+                }
+                resolved = StoredChunkState.missing();
+            }
+            storedChunks.put(chunkPos.pack(), resolved);
+            return resolved;
+        }
+
+        private static CompoundTag datafix(ServerLevel level, CompoundTag storedChunk) {
+            int dataVersion = NbtUtils.getDataVersion(storedChunk);
+            int currentDataVersion = SharedConstants.getCurrentVersion().dataVersion().version();
+            if (dataVersion >= currentDataVersion) {
+                return storedChunk;
+            }
+            if (level == null) {
+                throw new IllegalStateException("Stored chunk datafix requires an active level");
+            }
+            CompoundTag context = chunkDataFixContext(level);
+            SimpleRegionStorage.injectDatafixingContext(storedChunk, context);
+            return DataFixTypes.CHUNK.updateToCurrentVersion(
+                    level.getServer().getFixerUpper(), storedChunk, dataVersion);
+        }
+
+        private static CompoundTag chunkDataFixContext(ServerLevel level) {
+            CompoundTag context = new CompoundTag();
+            String levelIdentifier = level.dimension().identifier().toString();
+            if (PAPER_LEVEL_TYPE_KEY == null) {
+                context.putString("dimension", levelIdentifier);
+            } else {
+                context.putString("dimension", paperLevelTypeKey(level).identifier().toString());
+                context.putString("level_identifier", levelIdentifier);
+            }
+            level.getChunkSource().getGenerator().getTypeNameForDataFixer()
+                    .ifPresent(identifier -> context.putString("generator", identifier.toString()));
+            return context;
+        }
+
+        boolean acceptsStored(ServerLevel level, ChunkPos chunkPos,
+                              String structureKey, boolean requireUnreferenced) {
+            return storedState(level, chunkPos).accepts(structureKey, requireUnreferenced);
+        }
+
+        int used() {
+            return used;
+        }
+    }
+
+    public static final class Search {
+        private final Engine engine;
+        private final String structureKey;
+        private final int blockX;
+        private final int blockZ;
+        private final int radius;
+        private final Probe probe;
+        private final Set<Long> rejectedChunks = new HashSet<>();
+
+        private Search(Engine engine, String structureKey, int blockX, int blockZ,
+                       int radius, Probe probe) {
+            this.engine = engine;
+            this.structureKey = structureKey;
+            this.blockX = blockX;
+            this.blockZ = blockZ;
+            this.radius = radius;
+            this.probe = probe;
+        }
+
+        public IrisStructureLocator.LocateResult predict() {
+            if (rejectedChunks.size() >= MAX_SELECTED_CANDIDATE_RETRIES) {
+                return new IrisStructureLocator.LocateResult(
+                        IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED, 0, 0, 0);
+            }
+            return IrisStructureLocator.locateInPlacementRings(
+                    engine, structureKey, blockX, blockZ, radius,
+                    (chunkX, chunkZ) -> !rejectedChunks.contains(ChunkPos.pack(chunkX, chunkZ))
+                            && probe.accepts(chunkX, chunkZ));
+        }
+
+        public VerifiedStart verify(IrisStructureLocator.LocateResult result) {
+            int chunkX = result.originX() >> 4;
+            int chunkZ = result.originZ() >> 4;
+            StructureStart start = probe.verifySelected(chunkX, chunkZ);
+            if (start == null) {
+                return null;
+            }
+            NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecovery.resolve(
+                    engine, probe.level, structureKey, probe.structure, start);
+            if (ownership == null) {
+                return null;
+            }
+            return new VerifiedStart(start, ownership);
+        }
+
+        public void reject(IrisStructureLocator.LocateResult result) {
+            rejectedChunks.add(ChunkPos.pack(result.originX() >> 4, result.originZ() >> 4));
+        }
+
+        public void reference(VerifiedStart verified) {
+            probe.reference(verified.start());
+        }
+    }
+
+    private static Method paperLevelTypeKey() {
+        try {
+            return ServerLevel.class.getMethod("getTypeKey");
+        } catch (NoSuchMethodException ignored) {
+            return null;
+        }
+    }
+
+    private static ResourceKey<?> paperLevelTypeKey(ServerLevel level) {
+        try {
+            Object value = PAPER_LEVEL_TYPE_KEY.invoke(level);
+            if (value instanceof ResourceKey<?> key) {
+                return key;
+            }
+            throw new IllegalStateException("Paper level type key has an unexpected value");
+        } catch (IllegalAccessException | InvocationTargetException error) {
+            throw new IllegalStateException("Cannot read Paper level type key", error);
+        }
+    }
+
+    public record VerifiedStart(StructureStart start,
+                                NativeStructureOwnershipRecord ownership) {
+    }
+
+    @FunctionalInterface
+    interface ChunkStorageScanner {
+        CompletableFuture<Void> scan(ChunkPos chunkPos, StreamTagVisitor visitor);
+    }
+
+    @FunctionalInterface
+    interface StoredChunkDatafixer {
+        CompoundTag datafix(ServerLevel level, CompoundTag storedChunk);
+    }
+
+    private record StoredChunkState(boolean stored, boolean startsPresent, CompoundTag starts) {
+        private static StoredChunkState missing() {
+            return new StoredChunkState(false, false, new CompoundTag());
+        }
+
+        private static StoredChunkState parse(CompoundTag chunk) {
+            CompoundTag structures = chunk.getCompoundOrEmpty("structures");
+            return structures.getCompound("starts")
+                    .map(starts -> new StoredChunkState(true, true, starts))
+                    .orElseGet(() -> new StoredChunkState(true, false, new CompoundTag()));
+        }
+
+        private boolean accepts(String structureKey, boolean requireUnreferenced) {
+            if (!stored || !startsPresent) {
+                return true;
+            }
+            return starts.getCompound(structureKey).map(start -> {
+                String id = start.getStringOr("id", "");
+                return !StructureStart.INVALID_START_ID.equals(id)
+                        && (!requireUnreferenced || start.getIntOr("references", 0) == 0);
+            }).orElse(false);
+        }
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureLocateResults.java

@@ -37,6 +37,19 @@ public final class NativeStructureLocateResults {
                 <= horizontalDistanceSquared(origin, replacement.getFirst()) ? nativeResult : replacement;
     }
 
+    public static <T> Pair<BlockPos, T> selectAndReference(
+            BlockPos origin,
+            Pair<BlockPos, T> replacement, Runnable replacementReference,
+            Pair<BlockPos, T> nativeResult, Runnable nativeReference) {
+        Pair<BlockPos, T> selected = nearest(origin, replacement, nativeResult);
+        if (selected == replacement && replacement != null) {
+            replacementReference.run();
+        } else if (selected == nativeResult && nativeResult != null) {
+            nativeReference.run();
+        }
+        return selected;
+    }
+
     private static long horizontalDistanceSquared(BlockPos origin, BlockPos target) {
         long dx = (long) target.getX() - origin.getX();
         long dz = (long) target.getZ() - origin.getZ();

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureOwnershipFingerprint.java

@@ -0,0 +1,239 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructurePlacementPlanner;
+import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.framework.StructurePlacementGrid;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import net.minecraft.world.level.levelgen.structure.pools.EmptyPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HexFormat;
+import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
+
+public final class NativeStructureOwnershipFingerprint {
+    private static final Comparator<PieceIdentity> PIECE_ORDER = Comparator
+            .comparing(PieceIdentity::type)
+            .thenComparingInt(PieceIdentity::minX)
+            .thenComparingInt(PieceIdentity::minY)
+            .thenComparingInt(PieceIdentity::minZ)
+            .thenComparingInt(PieceIdentity::maxX)
+            .thenComparingInt(PieceIdentity::maxY)
+            .thenComparingInt(PieceIdentity::maxZ)
+            .thenComparingInt(PieceIdentity::orientation)
+            .thenComparingInt(PieceIdentity::generationDepth)
+            .thenComparing(PieceIdentity::detail);
+
+    private NativeStructureOwnershipFingerprint() {
+    }
+
+    public static NativeStructureOwnershipRecord capture(String structureKey,
+                                                         StructureStart start,
+                                                         NativeStructureStartPlan plan,
+                                                         BoundingBox referenceEnvelope) {
+        StructureStart resolvedStart = requireValid(start);
+        NativeStructureStartPlan resolvedPlan = Objects.requireNonNull(
+                plan, "Native structure start plan must not be null");
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(resolvedStart);
+        BoundingBox references = Objects.requireNonNull(
+                referenceEnvelope, "Native structure reference envelope must not be null");
+        ChunkPos origin = resolvedStart.getChunkPos();
+        return NativeStructureOwnershipRecord.create(
+                structureKey,
+                origin.x(),
+                origin.z(),
+                StructurePlacementGrid.placementIdentity(resolvedPlan.placement()),
+                resolvedPlan.baseY(),
+                content.minX(),
+                content.minY(),
+                content.minZ(),
+                content.maxX(),
+                content.maxY(),
+                content.maxZ(),
+                locatorY(resolvedStart),
+                references.minX() >> 4,
+                references.maxX() >> 4,
+                references.minZ() >> 4,
+                references.maxZ() >> 4,
+                fingerprint(structureKey, resolvedStart),
+                NativeStructurePlacementPlanner.decisionFor(resolvedPlan)
+        );
+    }
+
+    public static boolean matches(NativeStructureOwnershipRecord record, StructureStart start) {
+        if (record == null || start == null || !start.isValid()) {
+            return false;
+        }
+        ChunkPos origin = start.getChunkPos();
+        if (origin.x() != record.originChunkX()
+                || origin.z() != record.originChunkZ()
+                || !fingerprint(record.structureKey(), start).equals(record.contentFingerprint())) {
+            return false;
+        }
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(start);
+        if (content.getXSpan() != (record.contentMaxX() - record.contentMinX()) + 1
+                || content.getYSpan() != (record.contentMaxY() - record.contentMinY()) + 1
+                || content.getZSpan() != (record.contentMaxZ() - record.contentMinZ()) + 1) {
+            return false;
+        }
+        return start.getStructure() instanceof OceanMonumentStructure
+                || content.minX() == record.contentMinX()
+                && content.minY() == record.contentMinY()
+                && content.minZ() == record.contentMinZ()
+                && content.maxX() == record.contentMaxX()
+                && content.maxY() == record.contentMaxY()
+                && content.maxZ() == record.contentMaxZ();
+    }
+
+    public static String fingerprint(String structureKey, StructureStart start) {
+        StructureStart resolvedStart = requireValid(start);
+        MessageDigest digest = sha256();
+        updateString(digest, Objects.requireNonNull(structureKey,
+                "Native structure key must not be null").trim().toLowerCase(Locale.ROOT));
+        updateInt(digest, resolvedStart.getChunkPos().x());
+        updateInt(digest, resolvedStart.getChunkPos().z());
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(resolvedStart);
+        List<PieceIdentity> pieces = contentPieces(resolvedStart, content.minY());
+        updateInt(digest, pieces.size());
+        for (PieceIdentity piece : pieces) {
+            updateString(digest, piece.type());
+            updateInt(digest, piece.minX());
+            updateInt(digest, piece.minY());
+            updateInt(digest, piece.minZ());
+            updateInt(digest, piece.maxX());
+            updateInt(digest, piece.maxY());
+            updateInt(digest, piece.maxZ());
+            updateInt(digest, piece.orientation());
+            updateInt(digest, piece.generationDepth());
+            updateString(digest, piece.detail());
+        }
+        return HexFormat.of().formatHex(digest.digest());
+    }
+
+    public static int locatorY(StructureStart start) {
+        StructureStart resolvedStart = requireValid(start);
+        if (!resolvedStart.getPieces().isEmpty()) {
+            return resolvedStart.getPieces().getFirst().getLocatorPosition().getY();
+        }
+        throw new IllegalStateException("Native structure contains no locatable content pieces");
+    }
+
+    private static List<PieceIdentity> contentPieces(StructureStart start, int contentMinY) {
+        List<PieceIdentity> pieces = new ArrayList<>();
+        for (StructurePiece piece : start.getPieces()) {
+            BoundingBox bounds = piece.getBoundingBox();
+            Identifier type = BuiltInRegistries.STRUCTURE_PIECE.getKey(piece.getType());
+            Direction orientation = piece.getOrientation();
+            String detail = pieceDetail(piece, contentMinY);
+            pieces.add(new PieceIdentity(
+                    type == null ? "" : type.toString(),
+                    bounds.minX(), bounds.minY() - contentMinY, bounds.minZ(),
+                    bounds.maxX(), bounds.maxY() - contentMinY, bounds.maxZ(),
+                    orientation == null ? -1 : orientation.get2DDataValue(),
+                    piece.getGenDepth(),
+                    detail
+            ));
+        }
+        if (pieces.isEmpty()) {
+            throw new IllegalStateException("Native structure contains no content pieces");
+        }
+        pieces.sort(PIECE_ORDER);
+        return List.copyOf(pieces);
+    }
+
+    private static String pieceDetail(StructurePiece piece, int contentMinY) {
+        if (!(piece instanceof PoolElementStructurePiece poolPiece)) {
+            return "";
+        }
+        return poolElementIdentity(poolPiece.getElement()) + "|"
+                + poolPiece.getPosition().getX() + ","
+                + (poolPiece.getPosition().getY() - contentMinY) + ","
+                + poolPiece.getPosition().getZ() + "|"
+                + poolPiece.getGroundLevelDelta() + "|"
+                + poolPiece.getRotation().getSerializedName();
+    }
+
+    private static String poolElementIdentity(StructurePoolElement element) {
+        Identifier type = BuiltInRegistries.STRUCTURE_POOL_ELEMENT.getKey(element.getType());
+        StringBuilder identity = new StringBuilder(element.getClass().getName())
+                .append('|')
+                .append(type == null ? "" : type)
+                .append('|')
+                .append(element.getProjection().getSerializedName())
+                .append('|')
+                .append(element.getGroundLevelDelta());
+        if (element == EmptyPoolElement.INSTANCE) {
+            return identity.append("|empty").toString();
+        }
+        if (element instanceof SinglePoolElement single) {
+            try {
+                return identity.append("|template=")
+                        .append(single.getTemplateLocation()).toString();
+            } catch (RuntimeException inlineTemplate) {
+                return identity.append("|runtime-template").toString();
+            }
+        }
+        if (element instanceof ListPoolElement list) {
+            identity.append("|list[");
+            for (StructurePoolElement child : list.getElements()) {
+                String childIdentity = poolElementIdentity(child);
+                identity.append(childIdentity.length()).append(':').append(childIdentity);
+            }
+            return identity.append(']').toString();
+        }
+        return identity.append("|bounded-custom").toString();
+    }
+
+    private static StructureStart requireValid(StructureStart start) {
+        StructureStart resolved = Objects.requireNonNull(
+                start, "Native structure start must not be null");
+        if (!resolved.isValid()) {
+            throw new IllegalArgumentException("Native structure start must be valid");
+        }
+        return resolved;
+    }
+
+    private static MessageDigest sha256() {
+        try {
+            return MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException error) {
+            throw new IllegalStateException("SHA-256 is unavailable", error);
+        }
+    }
+
+    private static void updateString(MessageDigest digest, String value) {
+        byte[] encoded = value.getBytes(StandardCharsets.UTF_8);
+        updateInt(digest, encoded.length);
+        digest.update(encoded);
+    }
+
+    private static void updateInt(MessageDigest digest, int value) {
+        digest.update((byte) (value >>> 24));
+        digest.update((byte) (value >>> 16));
+        digest.update((byte) (value >>> 8));
+        digest.update((byte) value);
+    }
+
+    private record PieceIdentity(String type,
+                                 int minX, int minY, int minZ,
+                                 int maxX, int maxY, int maxZ,
+                                 int orientation, int generationDepth, String detail) {
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureOwnershipRecovery.java

@@ -0,0 +1,157 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipStore;
+import art.arcane.iris.engine.framework.NativeStructurePlacementPlanner;
+import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.framework.StructurePlacementGrid;
+import art.arcane.iris.engine.object.NativeStructureGenerationStatus;
+import art.arcane.iris.engine.object.NativeStructureSuppression;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
+
+import java.util.Locale;
+import java.util.Objects;
+
+public final class NativeStructureOwnershipRecovery {
+    private NativeStructureOwnershipRecovery() {
+    }
+
+    public static NativeStructureOwnershipRecord resolve(
+            Engine engine, ServerLevel level, String structureKey,
+            Structure structure, StructureStart start) {
+        Objects.requireNonNull(engine, "Native structure ownership recovery requires an engine");
+        ServerLevel activeLevel = Objects.requireNonNull(
+                level, "Native structure ownership recovery requires a level");
+        Structure activeStructure = Objects.requireNonNull(
+                structure, "Native structure ownership recovery requires a structure");
+        if (start == null || !start.isValid() || start.getStructure() != activeStructure) {
+            return null;
+        }
+        ChunkPos origin = start.getChunkPos();
+        NativeStructureOwnershipRecord persisted = NativeStructureOwnershipStore.findPersisted(
+                engine, structureKey, origin.x(), origin.z());
+        if (persisted != null) {
+            if (NativeStructureOwnershipFingerprint.matches(persisted, start)) {
+                return persisted;
+            }
+            NativeStructureOwnershipStore.discard(
+                    engine, structureKey, origin.x(), origin.z());
+        }
+        NativeStructureStartPlan plan = NativeStructurePlacementPlanner.matchingPlan(
+                engine, structureKey, origin.x(), origin.z());
+        if (!matchesPlan(structureKey, origin, plan)) {
+            return null;
+        }
+        Registry<Structure> registry = activeLevel.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+        Holder<Structure> holder = registry.wrapAsHolder(activeStructure);
+        ChunkGeneratorStructureState state = activeLevel.getChunkSource().getGeneratorState();
+        if (naturalStartIsAmbiguous(engine, structureKey, activeStructure, holder, state, plan)) {
+            return null;
+        }
+        StructureStart expected = generateExpected(
+                engine, activeLevel, holder, plan, start.getReferences());
+        NativeStructureOwnershipRecord recovered = proveCandidate(
+                structureKey, activeStructure, start, plan, expected, false);
+        if (recovered == null) {
+            return null;
+        }
+        NativeStructureOwnershipStore.record(engine, recovered);
+        return recovered;
+    }
+
+    static NativeStructureOwnershipRecord proveCandidate(
+            String structureKey, Structure structure, StructureStart persisted,
+            NativeStructureStartPlan plan, StructureStart expected,
+            boolean naturalStartAmbiguous) {
+        if (naturalStartAmbiguous || structure == null
+                || persisted == null || !persisted.isValid()
+                || expected == null || !expected.isValid()
+                || persisted.getStructure() != structure
+                || expected.getStructure() != structure
+                || !matchesPlan(structureKey, persisted.getChunkPos(), plan)
+                || !persisted.getChunkPos().equals(expected.getChunkPos())) {
+            return null;
+        }
+        BoundingBox referenceEnvelope = NativeStructureReferenceEnvelope.referenceBounds(
+                expected, structure, plan.placement().resolvedTerrain(), structureKey);
+        NativeStructureOwnershipRecord candidate = NativeStructureOwnershipFingerprint.capture(
+                structureKey, expected, plan, referenceEnvelope);
+        if (candidate.placementIdentity()
+                != StructurePlacementGrid.placementIdentity(plan.placement())) {
+            return null;
+        }
+        return NativeStructureOwnershipFingerprint.matches(candidate, persisted)
+                ? candidate : null;
+    }
+
+    private static boolean matchesPlan(String structureKey, ChunkPos origin,
+                                       NativeStructureStartPlan plan) {
+        if (structureKey == null || structureKey.isBlank() || plan == null) {
+            return false;
+        }
+        return plan.chunkX() == origin.x()
+                && plan.chunkZ() == origin.z()
+                && normalize(structureKey).equals(normalize(plan.source().getStructure()));
+    }
+
+    private static StructureStart generateExpected(
+            Engine engine, ServerLevel level, Holder<Structure> holder,
+            NativeStructureStartPlan plan, int references) {
+        ChunkGeneratorStructureState state = level.getChunkSource().getGeneratorState();
+        ChunkGenerator generator = level.getChunkSource().getGenerator();
+        BiomeSource biomeSource = generator.getBiomeSource();
+        NativeStructureFactory.GenerationContext generationContext =
+                new NativeStructureFactory.GenerationContext(
+                        level.registryAccess(),
+                        generator,
+                        biomeSource,
+                        state.randomState(),
+                        level.getStructureManager(),
+                        state.getLevelSeed(),
+                        level.dimension(),
+                        level,
+                        biome -> true,
+                        generator.getSeaLevel(),
+                        (x, z) -> engine.getHeight(x, z, true) + engine.getMinHeight()
+                );
+        return NativeStructureFactory.generate(generationContext, holder, plan, references);
+    }
+
+    private static boolean naturalStartIsAmbiguous(
+            Engine engine, String structureKey, Structure structure,
+            Holder<Structure> holder, ChunkGeneratorStructureState state,
+            NativeStructureStartPlan plan) {
+        if (plan.placement().getNativeSuppression() == NativeStructureSuppression.REPLACE_SOURCE) {
+            return false;
+        }
+        NativeStructureGenerationStatus sourceStatus = NativeStructureGenerationPolicy.resolve(
+                engine, structureKey,
+                NativeStructureVegetationClearer.isUndergroundStep(structure.step())).status();
+        if (sourceStatus == NativeStructureGenerationStatus.REPLACED_BY_IRIS) {
+            return false;
+        }
+        for (StructurePlacement placement : state.getPlacementsForStructure(holder)) {
+            if (placement.isStructureChunk(state, plan.chunkX(), plan.chunkZ())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static String normalize(String structureKey) {
+        return structureKey == null ? "" : structureKey.trim().toLowerCase(Locale.ROOT);
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructurePostProcessor.java

@@ -42,9 +42,18 @@ public final class NativeStructurePostProcessor {
         if (targets == null || targets.isEmpty()) {
             return;
         }
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                NativeStructureTerrainIntegrator.captureSourceTerrain(world, area, targets);
         for (NativeStructureTerrainIntegrator.TerrainTarget target : targets) {
             NativeStructureTerrainIntegrator.integrateTerrain(world, area, target.structureId(), target.start(),
-                    target.terrain(), paletteBlockResolver);
+                    target.terrain(), paletteBlockResolver, sourceTerrain);
+        }
+        for (NativeStructureTerrainIntegrator.TerrainTarget target : targets) {
+            if (NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                    target.start(), target.terrain())) {
+                NativeStructureTerrainIntegrator.clearLegacyTemplateAir(
+                        world, area, target.start(), () -> world.getLevel().getStructureManager());
+            }
         }
     }
 

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureReferenceEnvelope.java

@@ -3,43 +3,61 @@ package art.arcane.iris.nativegen;
 import art.arcane.iris.engine.object.IrisStructureTerrain;
 import art.arcane.iris.engine.object.IrisStructureTerrainMode;
 import art.arcane.iris.spi.IrisLogging;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
 import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.block.Rotation;
 import net.minecraft.world.level.levelgen.structure.BoundingBox;
-import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.StructurePiece;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
-import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
-import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
-import net.minecraft.world.level.levelgen.structure.templatesystem.BlockIgnoreProcessor;
-import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
-import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
-import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
 
-import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 public final class NativeStructureReferenceEnvelope {
-    private static final int MARKER_GROUND_LEVEL_DELTA = Integer.MIN_VALUE;
     private static final int MAX_REFERENCE_DISTANCE_CHUNKS = 8;
-    private static final StructurePoolElement MARKER_ELEMENT = StructurePoolElement.single(
-            "minecraft:empty",
-            Holder.direct(new StructureProcessorList(List.of(
-                    BlockIgnoreProcessor.STRUCTURE_AND_AIR))),
-            LiquidSettings.APPLY_WATERLOGGING
-    ).apply(StructureTemplatePool.Projection.RIGID);
+    private static final Set<String> WARNED_CLIPPED_TERRAIN = ConcurrentHashMap.newKeySet();
+    private static final Set<String> WARNED_SKIPPED_CONTENT = ConcurrentHashMap.newKeySet();
 
     private NativeStructureReferenceEnvelope() {
     }
 
     public static StructureStart wrap(StructureStart generated, Structure source, int references,
-                                      StructureTemplateManager templateManager,
                                       IrisStructureTerrain terrain) {
-        List<StructurePiece> pieces = new ArrayList<>(generated.getPieces());
+        return wrap(generated, source, references, terrain, null);
+    }
+
+    public static StructureStart wrap(StructureStart generated, Structure source, int references,
+                                      IrisStructureTerrain terrain, String structureKey) {
+        referenceBounds(generated, source, terrain, structureKey);
+        return new StructureStart(
+                source,
+                generated.getChunkPos(),
+                references,
+                new PiecesContainer(List.copyOf(generated.getPieces()))
+        );
+    }
+
+    public static StructureStart wrapForPublication(
+            StructureStart generated, Structure source, int references,
+            IrisStructureTerrain terrain, String structureKey) {
+        try {
+            return wrap(generated, source, references, terrain, structureKey);
+        } catch (UnrepresentableContentException exception) {
+            warnSkippedContent(generated, source, structureKey);
+            return StructureStart.INVALID_START;
+        }
+    }
+
+    public static BoundingBox referenceBounds(StructureStart start, Structure source,
+                                              IrisStructureTerrain terrain) {
+        return referenceBounds(start, source, terrain, null);
+    }
+
+    public static BoundingBox referenceBounds(StructureStart start, Structure source,
+                                              IrisStructureTerrain terrain,
+                                              String structureKey) {
         IrisStructureTerrainMode mode = terrain == null
                 ? IrisStructureTerrainMode.PRESERVE : terrain.resolvedMode();
         boolean usesEnvelope = mode == IrisStructureTerrainMode.BORE
@@ -47,9 +65,19 @@ public final class NativeStructureReferenceEnvelope {
                 || mode == IrisStructureTerrainMode.VACUUM
                 || mode == IrisStructureTerrainMode.ENCASE;
         int horizontalPadding = usesEnvelope ? Math.max(0, terrain.getHorizontalPadding()) : 0;
-        if (horizontalPadding > 0) {
-            BoundingBox content = contentBounds(pieces);
-            BoundingBox envelope = new BoundingBox(
+        BoundingBox content = contentBounds(start);
+        if (!fitsReferenceRange(start.getChunkPos(), content)) {
+            throw new UnrepresentableContentException("Native structure content at "
+                    + start.getChunkPos().x() + "," + start.getChunkPos().z()
+                    + " exceeds Minecraft's " + MAX_REFERENCE_DISTANCE_CHUNKS
+                    + "-chunk structure reference range");
+        }
+        BoundingBox adjustedEnvelope;
+        boolean arithmeticClipped = false;
+        try {
+            BoundingBox envelope = horizontalPadding == 0
+                    ? content
+                    : new BoundingBox(
                     Math.subtractExact(content.minX(), horizontalPadding),
                     content.minY(),
                     Math.subtractExact(content.minZ(), horizontalPadding),
@@ -57,41 +85,36 @@ public final class NativeStructureReferenceEnvelope {
                     content.maxY(),
                     Math.addExact(content.maxZ(), horizontalPadding)
             );
-            BoundingBox referencedEnvelope = clampReferenceRange(generated.getChunkPos(), envelope);
-            if (!sameHorizontalBounds(envelope, referencedEnvelope)) {
-                IrisLogging.warn("Native structure terrain envelope at "
-                        + generated.getChunkPos().x() + "," + generated.getChunkPos().z()
-                        + " was clipped to Minecraft's " + MAX_REFERENCE_DISTANCE_CHUNKS
-                        + "-chunk structure reference range");
-            }
-            pieces.add(marker(templateManager, referencedEnvelope.minX(),
-                    referencedEnvelope.minY(), referencedEnvelope.minZ()));
-            pieces.add(marker(templateManager, referencedEnvelope.maxX(),
-                    referencedEnvelope.maxY(), referencedEnvelope.maxZ()));
+            adjustedEnvelope = mode == IrisStructureTerrainMode.SOURCE
+                    ? source.adjustBoundingBox(content) : envelope;
+            adjustedEnvelope = encapsulating(adjustedEnvelope, content);
+        } catch (ArithmeticException exception) {
+            adjustedEnvelope = maximumReferenceBounds(start.getChunkPos(), content);
+            arithmeticClipped = true;
+        }
+        BoundingBox referencedEnvelope = clampReferenceRange(start.getChunkPos(), adjustedEnvelope);
+        if (arithmeticClipped || !sameHorizontalBounds(adjustedEnvelope, referencedEnvelope)) {
+            warnClippedTerrain(start, source, structureKey);
+            return referencedEnvelope;
+        }
+        return adjustedEnvelope;
+    }
+
+    public static boolean contentFitsReferenceRange(StructureStart start) {
+        try {
+            return fitsReferenceRange(start.getChunkPos(), contentBounds(start));
+        } catch (UnrepresentableContentException exception) {
+            return false;
         }
-        return new StructureStart(
-                source,
-                generated.getChunkPos(),
-                references,
-                new PiecesContainer(List.copyOf(pieces))
-        );
     }
 
     public static BoundingBox contentBounds(StructureStart start) {
         return contentBounds(start.getPieces());
     }
 
-    public static boolean isMarker(StructurePiece piece) {
-        return piece instanceof PoolElementStructurePiece poolPiece
-                && poolPiece.getGroundLevelDelta() == MARKER_GROUND_LEVEL_DELTA;
-    }
-
     private static BoundingBox contentBounds(List<StructurePiece> pieces) {
         BoundingBox bounds = null;
         for (StructurePiece piece : pieces) {
-            if (isMarker(piece)) {
-                continue;
-            }
             bounds = bounds == null
                     ? copy(piece.getBoundingBox())
                     : bounds.encapsulate(piece.getBoundingBox());
@@ -102,25 +125,11 @@ public final class NativeStructureReferenceEnvelope {
         return bounds;
     }
 
-    private static PoolElementStructurePiece marker(StructureTemplateManager templateManager,
-                                                     int x, int y, int z) {
-        BlockPos position = new BlockPos(x, y, z);
-        return new PoolElementStructurePiece(
-                templateManager,
-                MARKER_ELEMENT,
-                position,
-                MARKER_GROUND_LEVEL_DELTA,
-                Rotation.NONE,
-                new BoundingBox(position),
-                LiquidSettings.APPLY_WATERLOGGING
-        );
-    }
-
     private static BoundingBox clampReferenceRange(ChunkPos startChunk, BoundingBox envelope) {
-        int minX = (startChunk.x() - MAX_REFERENCE_DISTANCE_CHUNKS) << 4;
-        int maxX = ((startChunk.x() + MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15;
-        int minZ = (startChunk.z() - MAX_REFERENCE_DISTANCE_CHUNKS) << 4;
-        int maxZ = ((startChunk.z() + MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15;
+        int minX = minimumReferenceBlock(startChunk.x());
+        int maxX = maximumReferenceBlock(startChunk.x());
+        int minZ = minimumReferenceBlock(startChunk.z());
+        int maxZ = maximumReferenceBlock(startChunk.z());
         return new BoundingBox(
                 Math.max(envelope.minX(), minX),
                 envelope.minY(),
@@ -131,6 +140,40 @@ public final class NativeStructureReferenceEnvelope {
         );
     }
 
+    private static BoundingBox maximumReferenceBounds(ChunkPos startChunk, BoundingBox content) {
+        return new BoundingBox(
+                minimumReferenceBlock(startChunk.x()), content.minY(),
+                minimumReferenceBlock(startChunk.z()),
+                maximumReferenceBlock(startChunk.x()), content.maxY(),
+                maximumReferenceBlock(startChunk.z())
+        );
+    }
+
+    private static boolean fitsReferenceRange(ChunkPos startChunk, BoundingBox content) {
+        return content.minX() >= minimumReferenceBlock(startChunk.x())
+                && content.maxX() <= maximumReferenceBlock(startChunk.x())
+                && content.minZ() >= minimumReferenceBlock(startChunk.z())
+                && content.maxZ() <= maximumReferenceBlock(startChunk.z());
+    }
+
+    private static int minimumReferenceBlock(int originChunk) {
+        return checkedReferenceBlock(
+                ((long) originChunk - MAX_REFERENCE_DISTANCE_CHUNKS) << 4, originChunk);
+    }
+
+    private static int maximumReferenceBlock(int originChunk) {
+        return checkedReferenceBlock(
+                (((long) originChunk + MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15L, originChunk);
+    }
+
+    private static int checkedReferenceBlock(long block, int originChunk) {
+        if (block < Integer.MIN_VALUE || block > Integer.MAX_VALUE) {
+            throw new UnrepresentableContentException("Native structure origin chunk " + originChunk
+                    + " exceeds Minecraft's block coordinate range");
+        }
+        return (int) block;
+    }
+
     private static boolean sameHorizontalBounds(BoundingBox left, BoundingBox right) {
         return left.minX() == right.minX()
                 && left.minZ() == right.minZ()
@@ -143,4 +186,51 @@ public final class NativeStructureReferenceEnvelope {
                 bounds.minX(), bounds.minY(), bounds.minZ(),
                 bounds.maxX(), bounds.maxY(), bounds.maxZ());
     }
+
+    private static BoundingBox encapsulating(BoundingBox left, BoundingBox right) {
+        return new BoundingBox(
+                Math.min(left.minX(), right.minX()),
+                Math.min(left.minY(), right.minY()),
+                Math.min(left.minZ(), right.minZ()),
+                Math.max(left.maxX(), right.maxX()),
+                Math.max(left.maxY(), right.maxY()),
+                Math.max(left.maxZ(), right.maxZ())
+        );
+    }
+
+    private static void warnClippedTerrain(
+            StructureStart start, Structure source, String structureKey) {
+        String key = warningKey(source, structureKey);
+        if (WARNED_CLIPPED_TERRAIN.add(key)) {
+            IrisLogging.warn("Clipping optional terrain envelope for native structure '"
+                    + key + "' at " + start.getChunkPos().x() + "," + start.getChunkPos().z()
+                    + " to Minecraft's " + MAX_REFERENCE_DISTANCE_CHUNKS
+                    + "-chunk reference range; all generated content remains exactly referenced");
+        }
+    }
+
+    private static void warnSkippedContent(
+            StructureStart start, Structure source, String structureKey) {
+        String key = warningKey(source, structureKey);
+        if (WARNED_SKIPPED_CONTENT.add(key)) {
+            IrisLogging.warn("Skipping native structure '" + key + "' at "
+                    + start.getChunkPos().x() + "," + start.getChunkPos().z()
+                    + " because its generated content exceeds Minecraft's "
+                    + MAX_REFERENCE_DISTANCE_CHUNKS
+                    + "-chunk reference range; no structure start, ownership, references, or blocks were published");
+        }
+    }
+
+    private static String warningKey(Structure source, String structureKey) {
+        if (structureKey != null && !structureKey.isBlank()) {
+            return structureKey.trim().toLowerCase(Locale.ROOT);
+        }
+        return source.getClass().getName();
+    }
+
+    public static final class UnrepresentableContentException extends IllegalStateException {
+        private UnrepresentableContentException(String message) {
+            super(message);
+        }
+    }
 }

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureReferenceRepair.java

@@ -0,0 +1,224 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipStore;
+import art.arcane.iris.engine.object.IrisNativeStructureDecision;
+import art.arcane.iris.spi.IrisLogging;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import net.minecraft.core.Registry;
+import net.minecraft.core.SectionPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+public final class NativeStructureReferenceRepair {
+    private static final int REFERENCE_DISTANCE_CHUNKS =
+            NativeStructureOwnershipRecord.MAX_REFERENCE_DISTANCE_CHUNKS;
+    private static final Set<String> WARNED_POLICY_INVALIDATIONS = ConcurrentHashMap.newKeySet();
+
+    private NativeStructureReferenceRepair() {
+    }
+
+    public static void createReferences(Engine engine, WorldGenLevel level,
+                                        StructureManager structureManager, ChunkAccess targetChunk) {
+        ChunkPos target = targetChunk.getPos();
+        Registry<Structure> registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+        ServerLevel serverLevel = level.getLevel();
+        List<ScannedStart> starts = new ArrayList<>();
+        for (int originChunkX = target.x() - REFERENCE_DISTANCE_CHUNKS;
+             originChunkX <= target.x() + REFERENCE_DISTANCE_CHUNKS; originChunkX++) {
+            for (int originChunkZ = target.z() - REFERENCE_DISTANCE_CHUNKS;
+                 originChunkZ <= target.z() + REFERENCE_DISTANCE_CHUNKS; originChunkZ++) {
+                ChunkAccess originChunk = level.getChunk(
+                        originChunkX, originChunkZ, ChunkStatus.STRUCTURE_STARTS);
+                for (Map.Entry<Structure, StructureStart> entry : originChunk.getAllStarts().entrySet()) {
+                    ScannedStart start = scanStart(
+                            engine, serverLevel, structureManager, targetChunk, registry,
+                            originChunk, entry.getKey(), entry.getValue());
+                    if (start != null && isTargetRelevant(engine, targetChunk, start)) {
+                        starts.add(start);
+                    }
+                }
+            }
+        }
+        for (ScannedStart start : starts) {
+            boolean valid;
+            synchronized (start.originChunk()) {
+                StructureStart current = start.originChunk().getStartForStructure(start.structure());
+                valid = current == start.start() && current.isValid();
+            }
+            if (!valid) {
+                continue;
+            }
+            structureManager.addReferenceForStructure(
+                    SectionPos.bottomOf(targetChunk), start.structure(),
+                    start.origin().pack(), targetChunk);
+        }
+    }
+
+    private static boolean isTargetRelevant(
+            Engine engine, ChunkAccess targetChunk, ScannedStart scanned) {
+        StructureStart start = scanned.start();
+        Structure structure = scanned.structure();
+        ChunkPos target = targetChunk.getPos();
+        if (scanned.ownership() != null) {
+            return requiresReference(target, scanned.structureKey(), start, scanned.ownership());
+        }
+        if (scanned.registered()) {
+            return requiresNaturalReference(
+                    engine, target, scanned.structureKey(), structure, start);
+        }
+        return NativeStructureReferenceEnvelope.contentBounds(start).intersects(
+                target.getMinBlockX(), target.getMinBlockZ(),
+                target.getMaxBlockX(), target.getMaxBlockZ());
+    }
+
+    private static ScannedStart scanStart(
+            Engine engine, ServerLevel level, StructureManager structureManager,
+            ChunkAccess targetChunk, Registry<Structure> registry,
+            ChunkAccess originChunk, Structure structure, StructureStart start) {
+        Identifier identifier = registry.getKey(structure);
+        String structureKey = identifier == null
+                ? structure.getClass().getName() : identifier.toString();
+        if (start == null || !start.isValid()) {
+            return null;
+        }
+        if (!NativeStructureReferenceEnvelope.contentFitsReferenceRange(start)) {
+            if (identifier != null) {
+                NativeStructureOwnershipStore.discard(
+                        engine, structureKey, start.getChunkPos().x(), start.getChunkPos().z());
+            }
+            invalidateStart(structureManager, originChunk, structure, start, targetChunk);
+            return null;
+        }
+        ChunkPos startOrigin = start.getChunkPos();
+        NativeStructureOwnershipRecord ownership = identifier == null ? null
+                : NativeStructureOwnershipRecovery.resolve(
+                engine, level, structureKey, structure, start);
+        if (ownership != null) {
+            return new ScannedStart(
+                    originChunk, structure, start, structureKey, ownership, true);
+        }
+        if (identifier != null && !naturalPolicyAllows(engine, structureKey, structure)) {
+            invalidateStart(structureManager, originChunk, structure, start, targetChunk);
+            if (WARNED_POLICY_INVALIDATIONS.add(structureKey)) {
+                IrisLogging.warn("Invalidating persisted natural structure start '"
+                        + structureKey + "' because the current Iris dimension policy disables it");
+            }
+            return null;
+        }
+        return new ScannedStart(
+                originChunk, structure, start, structureKey, null, identifier != null);
+    }
+
+    private static boolean naturalPolicyAllows(
+            Engine engine, String structureKey, Structure structure) {
+        IrisNativeStructureDecision decision = NativeStructureGenerationPolicy.resolve(
+                engine, structureKey,
+                NativeStructureVegetationClearer.isUndergroundStep(structure.step()));
+        return naturalDecisionAllows(decision);
+    }
+
+    static boolean naturalDecisionAllows(IrisNativeStructureDecision decision) {
+        return Objects.requireNonNull(
+                decision, "Native structure decision must not be null").generate();
+    }
+
+    private static void invalidateStart(
+            StructureManager structureManager, ChunkAccess originChunk,
+            Structure structure, StructureStart start, ChunkAccess targetChunk) {
+        synchronized (originChunk) {
+            StructureStart current = originChunk.getStartForStructure(structure);
+            if (current == start && current.isValid()) {
+                structureManager.setStartForStructure(
+                        SectionPos.bottomOf(originChunk), structure,
+                        StructureStart.INVALID_START, originChunk);
+            }
+        }
+        if (targetChunk != null) {
+            removeTargetReference(targetChunk, structure, start.getChunkPos().pack());
+        }
+    }
+
+    private static void removeTargetReference(
+            ChunkAccess targetChunk, Structure structure, long origin) {
+        LongSet current = targetChunk.getAllReferences().get(structure);
+        if (current == null || !current.contains(origin)) {
+            return;
+        }
+        Map<Structure, LongSet> updated = new HashMap<>(targetChunk.getAllReferences());
+        LongSet retained = new LongOpenHashSet(current);
+        retained.remove(origin);
+        if (retained.isEmpty()) {
+            updated.remove(structure);
+        } else {
+            updated.put(structure, retained);
+        }
+        targetChunk.setAllReferences(updated);
+    }
+
+    static boolean requiresNaturalReference(Engine engine, ChunkPos target, String structureKey,
+                                            Structure structure, StructureStart start) {
+        if (target == null || start == null || !start.isValid()) {
+            return false;
+        }
+        IrisNativeStructureDecision decision = NativeStructureGenerationPolicy.resolve(
+                engine, structureKey,
+                NativeStructureVegetationClearer.isUndergroundStep(structure.step()));
+        if (!decision.generate()) {
+            return false;
+        }
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                start, structure,
+                NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain()),
+                structureKey);
+        return referenceBounds.intersects(
+                target.getMinBlockX(), target.getMinBlockZ(),
+                target.getMaxBlockX(), target.getMaxBlockZ());
+    }
+
+    static boolean requiresReference(ChunkPos target, String structureKey,
+                                     StructureStart start,
+                                     NativeStructureOwnershipRecord ownership) {
+        if (target == null || start == null || !start.isValid()
+                || ownership == null || !ownership.structureKey().equals(structureKey)
+                || !ownership.covers(target.x(), target.z())) {
+            return false;
+        }
+        return NativeStructureOwnershipFingerprint.matches(ownership, start);
+    }
+
+    private record ScannedStart(
+            ChunkAccess originChunk,
+            Structure structure,
+            StructureStart start,
+            String structureKey,
+            NativeStructureOwnershipRecord ownership,
+            boolean registered
+    ) {
+        private ChunkPos origin() {
+            return ownership == null
+                    ? start.getChunkPos()
+                    : new ChunkPos(ownership.originChunkX(), ownership.originChunkZ());
+        }
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureStartInjector.java

@@ -1,9 +1,14 @@
 package art.arcane.iris.nativegen;
 
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipStore;
 import art.arcane.iris.engine.framework.NativeStructurePlacementPlanner;
 import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.object.NativeStructureGenerationStatus;
 import art.arcane.iris.engine.object.NativeStructureSuppression;
+import art.arcane.iris.spi.IrisLogging;
 import net.minecraft.core.Holder;
 import net.minecraft.core.Registry;
 import net.minecraft.core.RegistryAccess;
@@ -17,6 +22,7 @@ import net.minecraft.world.level.biome.BiomeSource;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
@@ -24,8 +30,12 @@ import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemp
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 public final class NativeStructureStartInjector {
+    private static final Set<String> WARNED_DUPLICATE_STRUCTURES = ConcurrentHashMap.newKeySet();
+
     private NativeStructureStartInjector() {
     }
 
@@ -48,14 +58,22 @@ public final class NativeStructureStartInjector {
             }
             Holder<Structure> holder = registry.wrapAsHolder(structure);
             if (configuredStarts.containsKey(structure)) {
-                throw new IllegalStateException("Multiple configured native structure placements selected '"
-                        + identifier + "' in chunk " + chunk.getPos().x() + "," + chunk.getPos().z()
-                        + "; Minecraft can persist only one start per registered structure per chunk");
+                if (WARNED_DUPLICATE_STRUCTURES.add(identifier.toString())) {
+                    IrisLogging.warn("Ignoring duplicate native structure placements for '"
+                            + identifier + "'; the first deterministic candidate owns each chunk start");
+                }
+                continue;
             }
             StructureStart existing = context.structureManager().getStartForStructure(
                     section, structure, chunk);
             boolean replacement = plan.placement().getNativeSuppression()
                     == NativeStructureSuppression.REPLACE_SOURCE;
+            if (!replacement && existing != null && existing.isValid()) {
+                NativeStructureGenerationStatus sourceStatus = NativeStructureGenerationPolicy.resolve(
+                        context.engine(), identifier.toString(),
+                        NativeStructureVegetationClearer.isUndergroundStep(structure.step())).status();
+                replacement = sourceStatus == NativeStructureGenerationStatus.REPLACED_BY_IRIS;
+            }
             if (!replacement && existing != null && existing.isValid()) {
                 continue;
             }
@@ -77,18 +95,43 @@ public final class NativeStructureStartInjector {
                     );
             StructureStart generated = NativeStructureFactory.generate(
                     generationContext, holder, plan, references);
-            if (!generated.isValid()) {
-                throw new IllegalStateException("Configured native structure '" + identifier
-                        + "' produced no valid start in chunk " + chunk.getPos().x()
-                        + "," + chunk.getPos().z());
+            if (!isUsableGeneratedStart(generated)) {
+                if (replacement) {
+                    context.structureManager().setStartForStructure(
+                            section, structure, StructureStart.INVALID_START, chunk);
+                }
+                NativeStructureOwnershipStore.discard(
+                        context.engine(), identifier.toString(),
+                        chunk.getPos().x(), chunk.getPos().z());
+                continue;
+            }
+            BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                    generated, structure, plan.placement().resolvedTerrain(), identifier.toString());
+            NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                    identifier.toString(), generated, plan, referenceBounds);
+            NativeStructureOwnershipStore.record(context.engine(), ownership);
+            try {
+                context.structureManager().setStartForStructure(
+                        section, structure, generated, chunk);
+            } catch (RuntimeException | Error publicationError) {
+                try {
+                    NativeStructureOwnershipStore.discard(
+                            context.engine(), identifier.toString(),
+                            chunk.getPos().x(), chunk.getPos().z());
+                } catch (RuntimeException | Error cleanupError) {
+                    publicationError.addSuppressed(cleanupError);
+                }
+                throw publicationError;
             }
-            context.structureManager().setStartForStructure(
-                    section, structure, generated, chunk);
             configuredStarts.put(structure, plan);
         }
         return Map.copyOf(configuredStarts);
     }
 
+    static boolean isUsableGeneratedStart(StructureStart start) {
+        return start != null && start.isValid();
+    }
+
     public record InjectionContext(
             Engine engine,
             RegistryAccess registryAccess,

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureSurfaceFitter.java

@@ -1,6 +1,8 @@
 package art.arcane.iris.nativegen;
 
 import art.arcane.iris.engine.object.IrisObjectVacuum;
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import art.arcane.iris.engine.object.IrisStructureTerrainMode;
 import net.minecraft.core.BlockPos;
 import net.minecraft.world.level.WorldGenLevel;
 import net.minecraft.world.level.block.Blocks;
@@ -13,13 +15,11 @@ import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
 import net.minecraft.world.level.levelgen.structure.pools.JigsawJunction;
 import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
-import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.IntBinaryOperator;
-import java.util.function.Supplier;
 
 public final class NativeStructureSurfaceFitter {
     private static final double SURFACE_TERRAIN_FALLOFF = 2.0;
@@ -30,32 +30,31 @@ public final class NativeStructureSurfaceFitter {
     }
 
     public static void prepareSurfaceStructures(WorldGenLevel world, BoundingBox area,
-                                                List<StructureStart> starts,
+                                                List<NativeStructureTerrainIntegrator.TerrainTarget> targets,
                                                 IntBinaryOperator surfaceHeight) {
-        if (starts == null || starts.isEmpty()) {
+        if (targets == null || targets.isEmpty()) {
             return;
         }
         Objects.requireNonNull(surfaceHeight, "Surface structure terrain fitting requires an Iris height resolver");
-        List<SurfaceAnchor> anchors = collectSurfaceAnchors(starts);
+        List<SurfaceAnchor> anchors = collectSurfaceAnchors(targets);
         if (!anchors.isEmpty()) {
             fitSurfaceTerrain(world, area, anchors, surfaceHeight);
         }
-        Supplier<StructureTemplateManager> templates = () -> world.getLevel().getStructureManager();
-        for (StructureStart start : starts) {
-            if (requiresSurfaceTerrain(start)) {
-                NativeStructureTerrainIntegrator.clearLegacyTemplateAir(world, area, start, templates);
-            }
-        }
     }
 
     static boolean shouldPrepareSurfaceTerrain(TerrainAdjustment adjustment,
                                                GenerationStep.Decoration step) {
         return adjustment == TerrainAdjustment.BEARD_THIN
-                && step == GenerationStep.Decoration.SURFACE_STRUCTURES;
+                || adjustment == TerrainAdjustment.BEARD_BOX;
     }
 
     static int resolveSurfaceTarget(List<SurfaceAnchor> anchors, int worldX, int worldZ,
                                     int originalY) {
+        return resolveSurface(anchors, worldX, worldZ, originalY).targetY();
+    }
+
+    private static SurfaceResolution resolveSurface(List<SurfaceAnchor> anchors,
+                                                    int worldX, int worldZ, int originalY) {
         int localTargetY = originalY;
         SurfaceAnchor selectedLocal = null;
         long totalInfluence = 0L;
@@ -64,11 +63,42 @@ public final class NativeStructureSurfaceFitter {
         for (SurfaceAnchor anchor : anchors) {
             int outX = IrisObjectVacuum.outset(worldX, anchor.minX(), anchor.maxX());
             int outZ = IrisObjectVacuum.outset(worldZ, anchor.minZ(), anchor.maxZ());
-            long distanceSquared = (long) outX * outX + (long) outZ * outZ;
-            if (distanceSquared > (long) SURFACE_TERRAIN_RADIUS * SURFACE_TERRAIN_RADIUS) {
+            boolean containsColumn = outX == 0 && outZ == 0;
+            if (containsColumn && anchor.strength() > 1 && originalY < anchor.meetY()) {
+                if (precedes(anchor, selectedLocal)) {
+                    localTargetY = anchor.meetY();
+                    selectedLocal = anchor;
+                }
+                continue;
+            }
+            int verticalDistance = anchor.verticalDistance(originalY);
+            long horizontalDistanceSquared = (long) outX * outX + (long) outZ * outZ;
+            long distanceSquared = (long) outX * outX + (long) outZ * outZ
+                    + (long) verticalDistance * verticalDistance;
+            double factor = 0D;
+            long radiusSquared = (long) SURFACE_TERRAIN_RADIUS * SURFACE_TERRAIN_RADIUS;
+            if (distanceSquared <= radiusSquared) {
+                double distance = Math.sqrt(distanceSquared);
+                factor = Math.pow(
+                        1D - distance / SURFACE_TERRAIN_RADIUS, SURFACE_TERRAIN_FALLOFF);
+            }
+            if (anchor.strength() > 1 && originalY < anchor.meetY()
+                    && verticalDistance > SURFACE_TERRAIN_RADIUS
+                    && horizontalDistanceSquared <= radiusSquared) {
+                double horizontalDistance = Math.sqrt(horizontalDistanceSquared);
+                double horizontalFactor = Math.pow(
+                        1D - horizontalDistance / SURFACE_TERRAIN_RADIUS,
+                        SURFACE_TERRAIN_FALLOFF);
+                double rescueProgress = Math.min(1D,
+                        (verticalDistance - SURFACE_TERRAIN_RADIUS)
+                                / (double) SURFACE_TERRAIN_RADIUS);
+                double rescueWeight = rescueProgress * rescueProgress
+                        * (3D - 2D * rescueProgress);
+                factor = Math.max(factor, horizontalFactor * rescueWeight);
+            }
+            if (factor <= 0D) {
                 continue;
             }
-            boolean containsColumn = outX == 0 && outZ == 0;
             if (containsColumn) {
                 if (precedes(anchor, selectedLocal)) {
                     localTargetY = anchor.meetY();
@@ -76,10 +106,6 @@ public final class NativeStructureSurfaceFitter {
                 }
                 continue;
             }
-            double factor = IrisObjectVacuum.columnInfluence(
-                    worldX, worldZ,
-                    anchor.minX(), anchor.maxX(), anchor.minZ(), anchor.maxZ(),
-                    SURFACE_TERRAIN_RADIUS, SURFACE_TERRAIN_FALLOFF);
             long influence = Math.round(factor * SURFACE_TERRAIN_INFLUENCE_SCALE);
             if (influence <= 0L) {
                 continue;
@@ -90,14 +116,15 @@ public final class NativeStructureSurfaceFitter {
             maximumInfluence = Math.max(maximumInfluence, influence);
         }
         if (selectedLocal != null) {
-            return localTargetY;
+            return new SurfaceResolution(localTargetY, selectedLocal.strength() > 1);
         }
         if (totalInfluence == 0L) {
-            return originalY;
+            return new SurfaceResolution(originalY, false);
         }
         double blendedMeetY = weightedMeetY / (double) totalInfluence;
         double factor = maximumInfluence / (double) SURFACE_TERRAIN_INFLUENCE_SCALE;
-        return (int) Math.round(originalY + ((blendedMeetY - originalY) * factor));
+        return new SurfaceResolution(
+                (int) Math.round(originalY + ((blendedMeetY - originalY) * factor)), false);
     }
 
     private static boolean precedes(SurfaceAnchor candidate, SurfaceAnchor selected) {
@@ -125,41 +152,62 @@ public final class NativeStructureSurfaceFitter {
         return false;
     }
 
-    private static List<SurfaceAnchor> collectSurfaceAnchors(List<StructureStart> starts) {
+    private static List<SurfaceAnchor> collectSurfaceAnchors(
+            List<NativeStructureTerrainIntegrator.TerrainTarget> targets) {
         List<SurfaceAnchor> anchors = new ArrayList<>();
-        for (StructureStart start : starts) {
-            if (!requiresSurfaceTerrain(start)) {
+        for (NativeStructureTerrainIntegrator.TerrainTarget target : targets) {
+            if (!requiresSurfaceTerrain(target)) {
                 continue;
             }
+            StructureStart start = target.start();
+            TerrainAdjustment adjustment = start.getStructure().terrainAdaptation();
             for (StructurePiece piece : start.getPieces()) {
-                if (NativeStructureReferenceEnvelope.isMarker(piece)) {
-                    continue;
-                }
                 if (piece instanceof PoolElementStructurePiece poolPiece) {
                     if (poolPiece.getElement().getProjection() == StructureTemplatePool.Projection.RIGID) {
                         BoundingBox bounds = poolPiece.getBoundingBox();
-                        anchors.add(new SurfaceAnchor(
-                                bounds.minX(), bounds.maxX(), bounds.minZ(), bounds.maxZ(),
-                                bounds.minY() + poolPiece.getGroundLevelDelta() - 1, 2));
+                        anchors.add(surfaceAnchor(
+                                bounds, bounds.minY() + poolPiece.getGroundLevelDelta(),
+                                2, adjustment));
                     }
                     for (JigsawJunction junction : poolPiece.getJunctions()) {
                         anchors.add(new SurfaceAnchor(
                                 junction.getSourceX(), junction.getSourceX(),
                                 junction.getSourceZ(), junction.getSourceZ(),
-                                junction.getSourceGroundY() - 1, 1));
+                                junction.getSourceGroundY() - 1, 1,
+                                junction.getSourceGroundY(), junction.getSourceGroundY()));
                     }
                     continue;
                 }
                 BoundingBox bounds = piece.getBoundingBox();
-                anchors.add(new SurfaceAnchor(
-                        bounds.minX(), bounds.maxX(), bounds.minZ(), bounds.maxZ(),
-                        bounds.minY() - 1, 2));
+                anchors.add(surfaceAnchor(bounds, bounds.minY(), 2, adjustment));
             }
         }
         return List.copyOf(anchors);
     }
 
+    static SurfaceAnchor surfaceAnchor(BoundingBox bounds, int groundY, int strength,
+                                       TerrainAdjustment adjustment) {
+        int meetY = groundY - 1;
+        if (adjustment == TerrainAdjustment.BEARD_BOX) {
+            return new SurfaceAnchor(
+                    bounds.minX(), bounds.maxX(), bounds.minZ(), bounds.maxZ(),
+                    meetY, strength, groundY, bounds.maxY());
+        }
+        return new SurfaceAnchor(bounds.minX(), bounds.maxX(), bounds.minZ(), bounds.maxZ(),
+                meetY, strength, groundY, groundY);
+    }
+
     static boolean requiresSurfaceTerrain(StructureStart start) {
+        return requiresSurfaceTerrain(new NativeStructureTerrainIntegrator.TerrainTarget(
+                null, start, new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE)));
+    }
+
+    static boolean requiresSurfaceTerrain(NativeStructureTerrainIntegrator.TerrainTarget target) {
+        if (target == null || target.terrain() == null
+                || target.terrain().resolvedMode() != IrisStructureTerrainMode.SOURCE) {
+            return false;
+        }
+        StructureStart start = target.start();
         return start != null
                 && start.isValid()
                 && shouldPrepareSurfaceTerrain(
@@ -173,14 +221,17 @@ public final class NativeStructureSurfaceFitter {
         int depth = area.getZSpan();
         int[] originalHeights = new int[width * depth];
         int[] targetHeights = new int[width * depth];
+        boolean[] rigidBaseSupport = new boolean[width * depth];
         for (int z = area.minZ(); z <= area.maxZ(); z++) {
             for (int x = area.minX(); x <= area.maxX(); x++) {
                 int column = (z - area.minZ()) * width + x - area.minX();
                 int originalY = Math.max(area.minY(), Math.min(
                         area.maxY(), surfaceHeight.applyAsInt(x, z)));
+                SurfaceResolution resolution = resolveSurface(anchors, x, z, originalY);
                 originalHeights[column] = originalY;
                 targetHeights[column] = Math.max(area.minY(), Math.min(
-                        area.maxY(), resolveSurfaceTarget(anchors, x, z, originalY)));
+                        area.maxY(), resolution.targetY()));
+                rigidBaseSupport[column] = resolution.rigidBaseSupport();
             }
         }
         BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
@@ -188,7 +239,8 @@ public final class NativeStructureSurfaceFitter {
             for (int x = area.minX(); x <= area.maxX(); x++) {
                 int column = (z - area.minZ()) * width + x - area.minX();
                 applySurfaceColumn(world, position, x, z,
-                        originalHeights[column], targetHeights[column], area.minY(), area.maxY());
+                        originalHeights[column], targetHeights[column], area.minY(), area.maxY(),
+                        rigidBaseSupport[column]);
             }
         }
     }
@@ -196,7 +248,18 @@ public final class NativeStructureSurfaceFitter {
     static void applySurfaceColumn(WorldGenLevel world, BlockPos.MutableBlockPos position,
                                    int x, int z, int originalY, int targetY,
                                    int worldMinY, int worldMaxY) {
+        applySurfaceColumn(world, position, x, z, originalY, targetY,
+                worldMinY, worldMaxY, false);
+    }
+
+    static void applySurfaceColumn(WorldGenLevel world, BlockPos.MutableBlockPos position,
+                                   int x, int z, int originalY, int targetY,
+                                   int worldMinY, int worldMaxY,
+                                   boolean requireRigidBaseSupport) {
         if (targetY == originalY) {
+            if (requireRigidBaseSupport) {
+                ensureRigidBaseTerrain(world, position, x, z, targetY, worldMinY);
+            }
             return;
         }
         SurfaceMaterials materials = resolveSurfaceMaterials(world, position, x, z, originalY, worldMinY);
@@ -207,6 +270,9 @@ public final class NativeStructureSurfaceFitter {
                 world.setBlock(position.set(x, y, z), clearedState, 2);
             }
             world.setBlock(position.set(x, targetY, z), materials.surface(), 2);
+            if (requireRigidBaseSupport) {
+                ensureRigidBaseTerrain(world, position, x, z, targetY, worldMinY, materials);
+            }
             return;
         }
         for (int y = originalY + 1; y < targetY; y++) {
@@ -219,6 +285,42 @@ public final class NativeStructureSurfaceFitter {
         if (!NativeStructureVegetationClearer.isTreeBlock(world.getBlockState(position))) {
             world.setBlock(position, materials.surface(), 2);
         }
+        if (requireRigidBaseSupport) {
+            ensureRigidBaseTerrain(world, position, x, z, targetY, worldMinY, materials);
+        }
+    }
+
+    private static void ensureRigidBaseTerrain(WorldGenLevel world,
+                                               BlockPos.MutableBlockPos position,
+                                               int x, int z, int targetY, int worldMinY) {
+        int supportY = targetY - 1;
+        boolean targetIsTerrain = isTerrainBlock(world.getBlockState(position.set(x, targetY, z)));
+        boolean supportIsTerrain = supportY < worldMinY
+                || isTerrainBlock(world.getBlockState(position.set(x, supportY, z)));
+        if (targetIsTerrain && supportIsTerrain) {
+            return;
+        }
+        SurfaceMaterials materials = resolveSurfaceMaterials(
+                world, position, x, z, targetY, worldMinY);
+        ensureRigidBaseTerrain(world, position, x, z, targetY, worldMinY, materials);
+    }
+
+    private static void ensureRigidBaseTerrain(WorldGenLevel world,
+                                               BlockPos.MutableBlockPos position,
+                                               int x, int z, int targetY, int worldMinY,
+                                               SurfaceMaterials materials) {
+        int supportY = targetY - 1;
+        position.set(x, targetY, z);
+        if (!isTerrainBlock(world.getBlockState(position))) {
+            world.setBlock(position, materials.surface(), 2);
+        }
+        if (supportY < worldMinY) {
+            return;
+        }
+        position.set(x, supportY, z);
+        if (!isTerrainBlock(world.getBlockState(position))) {
+            world.setBlock(position, materials.subsurface(), 2);
+        }
     }
 
     private static BlockState clearSurfaceDecorationAndResolveFill(
@@ -271,9 +373,20 @@ public final class NativeStructureSurfaceFitter {
         return state.isSolid() && !NativeStructureVegetationClearer.isTreeBlock(state);
     }
 
-    record SurfaceAnchor(int minX, int maxX, int minZ, int maxZ, int meetY, int strength) {
+    record SurfaceAnchor(int minX, int maxX, int minZ, int maxZ, int meetY, int strength,
+                         int minInfluenceY, int maxInfluenceY) {
+        SurfaceAnchor(int minX, int maxX, int minZ, int maxZ, int meetY, int strength) {
+            this(minX, maxX, minZ, maxZ, meetY, strength, meetY + 1, meetY + 1);
+        }
+
+        int verticalDistance(int y) {
+            return IrisObjectVacuum.outset(y, minInfluenceY, maxInfluenceY);
+        }
     }
 
     private record SurfaceMaterials(BlockState surface, BlockState subsurface) {
     }
+
+    private record SurfaceResolution(int targetY, boolean rigidBaseSupport) {
+    }
 }

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureTemplatePoolBounds.java

@@ -0,0 +1,228 @@
+package art.arcane.iris.nativegen;
+
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.pools.EmptyPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.FeaturePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.pools.alias.DirectPoolAlias;
+import net.minecraft.world.level.levelgen.structure.pools.alias.PoolAliasBinding;
+import net.minecraft.world.level.levelgen.structure.pools.alias.RandomGroupPoolAlias;
+import net.minecraft.world.level.levelgen.structure.pools.alias.RandomPoolAlias;
+import net.minecraft.world.level.levelgen.structure.structures.JigsawStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Function;
+
+public final class NativeStructureTemplatePoolBounds {
+    private NativeStructureTemplatePoolBounds() {
+    }
+
+    public static int sourceHorizontalSpan(RegistryAccess registryAccess,
+                                           StructureTemplateManager templateManager,
+                                           JigsawStructure source) {
+        Registry<StructureTemplatePool> pools = registryAccess.lookupOrThrow(Registries.TEMPLATE_POOL);
+        return sourceHorizontalSpan(
+                templateManager,
+                source.getStartPool(),
+                source.getPoolAliases(),
+                key -> pools.getValue(key.identifier()));
+    }
+
+    public static int horizontalSpan(RegistryAccess registryAccess,
+                                     StructureTemplateManager templateManager,
+                                     String templatePoolKey) {
+        Identifier identifier = Identifier.tryParse(templatePoolKey);
+        if (identifier == null) {
+            throw new IllegalArgumentException("Invalid registered template pool key: " + templatePoolKey);
+        }
+        Registry<StructureTemplatePool> pools = registryAccess.lookupOrThrow(Registries.TEMPLATE_POOL);
+        StructureTemplatePool pool = pools.getValue(identifier);
+        if (pool == null) {
+            throw new IllegalArgumentException("Registered template pool does not exist: " + templatePoolKey);
+        }
+        return horizontalSpan(pool, templateManager);
+    }
+
+    public static int horizontalSpan(RegistryAccess registryAccess,
+                                     StructureTemplateManager templateManager,
+                                     JigsawStructure source,
+                                     String templatePoolKey) {
+        Identifier identifier = Identifier.tryParse(templatePoolKey);
+        if (identifier == null) {
+            throw new IllegalArgumentException("Invalid registered template pool key: " + templatePoolKey);
+        }
+        Registry<StructureTemplatePool> pools = registryAccess.lookupOrThrow(Registries.TEMPLATE_POOL);
+        ResourceKey<StructureTemplatePool> startPoolKey = ResourceKey.create(
+                Registries.TEMPLATE_POOL, identifier);
+        StructureTemplatePool startPool = pools.getValue(identifier);
+        if (startPool == null) {
+            throw new IllegalArgumentException("Registered template pool does not exist: " + templatePoolKey);
+        }
+        return sourceHorizontalSpan(
+                templateManager,
+                startPool,
+                startPoolKey,
+                source.getPoolAliases(),
+                key -> pools.getValue(key.identifier()));
+    }
+
+    static int sourceHorizontalSpan(StructureTemplateManager templateManager,
+                                    Holder<StructureTemplatePool> startPool,
+                                    List<PoolAliasBinding> aliases,
+                                    Function<ResourceKey<StructureTemplatePool>, StructureTemplatePool> poolLookup) {
+        return sourceHorizontalSpan(templateManager, startPool.value(),
+                startPool.unwrapKey().orElse(null), aliases, poolLookup);
+    }
+
+    static int sourceHorizontalSpan(StructureTemplateManager templateManager,
+                                    StructureTemplatePool startPool,
+                                    ResourceKey<StructureTemplatePool> startPoolKey,
+                                    List<PoolAliasBinding> aliases,
+                                    Function<ResourceKey<StructureTemplatePool>, StructureTemplatePool> poolLookup) {
+        int maximumSpan = directHorizontalSpan(startPool, templateManager);
+        if (startPoolKey == null) {
+            return maximumSpan;
+        }
+        Set<ResourceKey<StructureTemplatePool>> targets = new HashSet<>();
+        for (PoolAliasBinding binding : aliases) {
+            collectTargets(binding, startPoolKey, targets);
+        }
+        for (ResourceKey<StructureTemplatePool> target : targets) {
+            StructureTemplatePool targetPool = poolLookup.apply(target);
+            if (targetPool == null) {
+                throw new IllegalStateException("Jigsaw start-pool alias target does not exist: "
+                        + target.identifier());
+            }
+            maximumSpan = Math.max(maximumSpan, directHorizontalSpan(targetPool, templateManager));
+        }
+        return maximumSpan;
+    }
+
+    private static void collectTargets(PoolAliasBinding binding,
+                                       ResourceKey<StructureTemplatePool> startPoolKey,
+                                       Set<ResourceKey<StructureTemplatePool>> targets) {
+        if (binding instanceof DirectPoolAlias direct) {
+            if (direct.alias().equals(startPoolKey)) {
+                targets.add(direct.target());
+            }
+            return;
+        }
+        if (binding instanceof RandomPoolAlias random) {
+            if (random.alias().equals(startPoolKey)) {
+                random.targets().unwrap().forEach(entry -> targets.add(entry.value()));
+            }
+            return;
+        }
+        if (binding instanceof RandomGroupPoolAlias group) {
+            group.groups().unwrap().forEach(entry -> entry.value().forEach(
+                    nested -> collectTargets(nested, startPoolKey, targets)));
+            return;
+        }
+        throw new IllegalStateException("Unsupported jigsaw pool alias type: "
+                + binding.getClass().getName());
+    }
+
+    static int horizontalSpan(StructureTemplatePool pool,
+                              StructureTemplateManager templateManager) {
+        Set<StructureTemplatePool> visited = Collections.newSetFromMap(new IdentityHashMap<>());
+        return horizontalSpan(pool, templateManager, visited);
+    }
+
+    private static int horizontalSpan(StructureTemplatePool pool,
+                                      StructureTemplateManager templateManager,
+                                      Set<StructureTemplatePool> visited) {
+        if (!visited.add(pool)) {
+            return 0;
+        }
+        int maximumSpan = directHorizontalSpan(pool, templateManager);
+        Holder<StructureTemplatePool> fallback = pool.getFallback();
+        if (fallback == null || !fallback.isBound()) {
+            throw new IllegalStateException("Template pool has an unresolved fallback");
+        }
+        return Math.max(maximumSpan, horizontalSpan(fallback.value(), templateManager, visited));
+    }
+
+    private static int directHorizontalSpan(StructureTemplatePool pool,
+                                            StructureTemplateManager templateManager) {
+        int maximumSpan = 0;
+        for (Pair<StructurePoolElement, Integer> entry : pool.getTemplates()) {
+            StructurePoolElement element = entry.getFirst();
+            validateElement(element, templateManager);
+            maximumSpan = Math.max(maximumSpan, horizontalSpan(element, templateManager));
+        }
+        return maximumSpan;
+    }
+
+    private static void validateElement(StructurePoolElement element,
+                                        StructureTemplateManager templateManager) {
+        if (element == EmptyPoolElement.INSTANCE || element instanceof FeaturePoolElement) {
+            return;
+        }
+        if (element instanceof SinglePoolElement single) {
+            Identifier template;
+            try {
+                template = single.getTemplateLocation();
+            } catch (RuntimeException inlineTemplate) {
+                return;
+            }
+            if (templateManager.get(template).isEmpty()) {
+                throw new IllegalStateException("Template pool element does not resolve a structure template: "
+                        + template);
+            }
+            return;
+        }
+        if (element instanceof ListPoolElement list) {
+            for (StructurePoolElement child : list.getElements()) {
+                validateElement(child, templateManager);
+            }
+            return;
+        }
+    }
+
+    private static int horizontalSpan(StructurePoolElement element,
+                                      StructureTemplateManager templateManager) {
+        if (element == EmptyPoolElement.INSTANCE) {
+            return 0;
+        }
+        long maximumSpan = 0L;
+        for (Rotation rotation : Rotation.values()) {
+            BoundingBox box;
+            try {
+                box = element.getBoundingBox(templateManager, BlockPos.ZERO, rotation);
+            } catch (RuntimeException | LinkageError error) {
+                throw new IllegalStateException("Template pool element "
+                        + element.getClass().getName()
+                        + " could not provide bounded geometry for rotation " + rotation, error);
+            }
+            if (box == null) {
+                throw new IllegalStateException("Template pool element "
+                        + element.getClass().getName()
+                        + " returned no bounded geometry for rotation " + rotation);
+            }
+            long xSpan = (long) box.maxX() - box.minX() + 1L;
+            long zSpan = (long) box.maxZ() - box.minZ() + 1L;
+            maximumSpan = Math.max(maximumSpan, Math.max(xSpan, zSpan));
+        }
+        if (maximumSpan < 0L || maximumSpan > Integer.MAX_VALUE) {
+            throw new IllegalStateException("Template pool element has an unbounded horizontal span");
+        }
+        return (int) maximumSpan;
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureTerrainIntegrator.java

@@ -9,16 +9,24 @@ import art.arcane.iris.engine.object.IrisStructureTerrainMode;
 import art.arcane.iris.util.project.noise.CNG;
 import art.arcane.volmlib.util.math.RNG;
 import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.world.level.Level;
 import net.minecraft.world.level.WorldGenLevel;
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.Rotation;
 import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.dimension.BuiltinDimensionTypes;
+import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.levelgen.structure.BoundingBox;
 import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
 import net.minecraft.world.level.levelgen.structure.StructurePiece;
 import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.pools.JigsawJunction;
 import net.minecraft.world.level.levelgen.structure.pools.LegacySinglePoolElement;
 import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
 import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
@@ -29,62 +37,80 @@ import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemp
 import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
 
 import java.util.ArrayList;
-import java.util.Collections;
+import java.util.BitSet;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
 
 public final class NativeStructureTerrainIntegrator {
-    private static final int AUTO_ENCASE_PADDING = 3;
     private static final long CARVE_CEILING_ROLL_SIGNATURE = 0x2A17L;
     private static final long CARVE_FLOOR_ROLL_SIGNATURE = 0x5B3DL;
     private static final long CARVE_LOBE_SIGNATURE = 0x7C41L;
-    private static final int MAX_CACHED_CARVE_FOOTPRINTS = 4;
+    private static final int MAX_CACHED_CARVE_CELLS = 2_000_000;
     private static final int MAX_CARVE_COLUMNS = 2_000_000;
     private static final int MAX_TEMPLATE_OCCUPANCY_CELLS = 4_194_304;
+    private static final int SOURCE_BURY_HORIZONTAL_RADIUS = 6;
+    private static final int SOURCE_BURY_VERTICAL_RADIUS = 12;
+    private static final int SOURCE_ENCAPSULATE_RADIUS = 12;
+    private static final int SOURCE_JUNCTION_RADIUS = 12;
+    private static final int SOURCE_MATERIAL_SAMPLE_RADIUS = 8;
     private static final List<Block> TEMPLATE_VOID_BLOCKS = List.of(Blocks.AIR, Blocks.STRUCTURE_VOID);
-    private static final Map<CarveFootprintKey, StructureCarvingFootprint> CARVE_FOOTPRINTS =
-            Collections.synchronizedMap(new LinkedHashMap<>(16, 0.75F, true) {
-                @Override
-                protected boolean removeEldestEntry(
-                        Map.Entry<CarveFootprintKey, StructureCarvingFootprint> eldest) {
-                    return size() > MAX_CACHED_CARVE_FOOTPRINTS;
-                }
-            });
+    private static final Set<Block> VANILLA_SOURCE_TERRAIN_BLOCKS = Set.of(
+            Blocks.STONE, Blocks.GRANITE, Blocks.DIORITE, Blocks.ANDESITE,
+            Blocks.TUFF, Blocks.DEEPSLATE, Blocks.NETHERRACK, Blocks.BASALT,
+            Blocks.BLACKSTONE, Blocks.DIRT, Blocks.COARSE_DIRT, Blocks.ROOTED_DIRT,
+            Blocks.GRASS_BLOCK, Blocks.PODZOL, Blocks.MYCELIUM, Blocks.MUD,
+            Blocks.MOSS_BLOCK, Blocks.SAND, Blocks.RED_SAND, Blocks.TERRACOTTA,
+            Blocks.CRIMSON_NYLIUM, Blocks.WARPED_NYLIUM, Blocks.SNOW_BLOCK,
+            Blocks.ICE, Blocks.PACKED_ICE, Blocks.BLUE_ICE, Blocks.SOUL_SAND,
+            Blocks.SOUL_SOIL, Blocks.END_STONE, Blocks.GRAVEL, Blocks.CLAY,
+            Blocks.CALCITE, Blocks.DRIPSTONE_BLOCK, Blocks.SANDSTONE,
+            Blocks.RED_SANDSTONE, Blocks.SCULK);
+    private static final Map<CarveFootprintKey, CachedCarveFootprint> CARVE_FOOTPRINTS =
+            new LinkedHashMap<>(16, 0.75F, true);
+    private static final ConcurrentHashMap<CarveFootprintKey, CompletableFuture<StructureCarvingFootprint>>
+            CARVE_FOOTPRINT_BUILDS = new ConcurrentHashMap<>();
+    private static int cachedCarveCells;
 
     private NativeStructureTerrainIntegrator() {
     }
 
     public static IrisStructureTerrain resolveNativeTerrain(StructureStart start,
                                                             IrisStructureTerrain configuredTerrain) {
-        if (configuredTerrain != null) {
-            return configuredTerrain;
-        }
-        if (start == null || !start.isValid()
-                || !encasesTerrain(start.getStructure().terrainAdaptation())) {
-            return null;
-        }
-        return new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.ENCASE)
-                .setHorizontalPadding(AUTO_ENCASE_PADDING)
-                .setCeilingPadding(AUTO_ENCASE_PADDING)
-                .setFloorPadding(AUTO_ENCASE_PADDING);
-    }
-
-    static boolean encasesTerrain(TerrainAdjustment adjustment) {
-        return adjustment == TerrainAdjustment.BURY || adjustment == TerrainAdjustment.ENCAPSULATE;
+        return configuredTerrain == null
+                ? new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE)
+                : configuredTerrain;
     }
 
     static void integrateTerrain(WorldGenLevel world, BoundingBox area, String structureId,
                                  StructureStart start, IrisStructureTerrain configuredTerrain,
                                  NativeStructurePostProcessor.PaletteBlockResolver paletteBlockResolver) {
+        SourceTerrainSnapshot sourceTerrain = requiresSourceTerrainFill(start, configuredTerrain)
+                ? captureSourceTerrain(world, area, start, configuredTerrain) : null;
+        integrateTerrain(world, area, structureId, start, configuredTerrain,
+                paletteBlockResolver, sourceTerrain);
+    }
+
+    static void integrateTerrain(WorldGenLevel world, BoundingBox area, String structureId,
+                                 StructureStart start, IrisStructureTerrain configuredTerrain,
+                                 NativeStructurePostProcessor.PaletteBlockResolver paletteBlockResolver,
+                                 SourceTerrainSnapshot sourceTerrain) {
         IrisStructureTerrain terrain = configuredTerrain == null
                 ? new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE)
                 : configuredTerrain;
         IrisStructureTerrainMode mode = terrain.resolvedMode();
-        if (mode == IrisStructureTerrainMode.SOURCE || mode == IrisStructureTerrainMode.PRESERVE) {
+        if (mode == IrisStructureTerrainMode.SOURCE) {
+            integrateSourceTerrain(world, area, start, sourceTerrain);
+            return;
+        }
+        if (mode == IrisStructureTerrainMode.PRESERVE) {
             return;
         }
         if (mode == IrisStructureTerrainMode.VACUUM) {
@@ -111,12 +137,381 @@ public final class NativeStructureTerrainIntegrator {
                 terrain, shape, carveNoiseIdentity(world, structureId, start)));
     }
 
+    static SourceTerrainSnapshot captureSourceTerrain(
+            WorldGenLevel world, BoundingBox area, List<TerrainTarget> targets) {
+        BitSet requiredLayers = new BitSet(area.getYSpan());
+        boolean requiresSnapshot = false;
+        for (TerrainTarget target : targets) {
+            if (target != null && requiresSourceTerrainFill(target.start(), target.terrain())) {
+                requiresSnapshot = true;
+                markSourceTerrainLayers(area, target.start(), target.terrain(), requiredLayers);
+            }
+        }
+        return requiresSnapshot ? SourceTerrainSnapshot.capture(world, area, requiredLayers) : null;
+    }
+
+    private static SourceTerrainSnapshot captureSourceTerrain(
+            WorldGenLevel world, BoundingBox area, StructureStart start,
+            IrisStructureTerrain configuredTerrain) {
+        BitSet requiredLayers = new BitSet(area.getYSpan());
+        markSourceTerrainLayers(area, start, configuredTerrain, requiredLayers);
+        return SourceTerrainSnapshot.capture(world, area, requiredLayers);
+    }
+
+    private static void markSourceTerrainLayers(
+            BoundingBox area, StructureStart start, IrisStructureTerrain configuredTerrain,
+            BitSet requiredLayers) {
+        if (!requiresSourceTerrainFill(start, configuredTerrain)) {
+            return;
+        }
+        TerrainAdjustment adjustment = start.getStructure().terrainAdaptation();
+        for (StructurePiece piece : start.getPieces()) {
+            if (!isSourceRigidPiece(piece)) {
+                continue;
+            }
+            BoundingBox bounds = piece.getBoundingBox();
+            long horizontalDistanceSquared = minimumHorizontalDistanceSquared(area, bounds);
+            if (adjustment == TerrainAdjustment.BURY) {
+                long remainingDistanceSquared = (long) SOURCE_BURY_VERTICAL_RADIUS
+                        * SOURCE_BURY_VERTICAL_RADIUS - 1L - horizontalDistanceSquared * 4L;
+                if (remainingDistanceSquared < 0L) {
+                    continue;
+                }
+                int verticalRadius = (int) Math.floor(Math.sqrt(remainingDistanceSquared));
+                long groundY = bounds.minY();
+                if (piece instanceof PoolElementStructurePiece poolPiece) {
+                    groundY += poolPiece.getGroundLevelDelta();
+                }
+                markLayers(area, requiredLayers,
+                        groundY - verticalRadius, groundY + verticalRadius);
+            } else {
+                long remainingDistanceSquared = (long) SOURCE_ENCAPSULATE_RADIUS
+                        * SOURCE_ENCAPSULATE_RADIUS - 1L - horizontalDistanceSquared;
+                if (remainingDistanceSquared < 0L) {
+                    continue;
+                }
+                int verticalRadius = (int) Math.floor(Math.sqrt(remainingDistanceSquared));
+                markLayers(area, requiredLayers,
+                        (long) bounds.minY() - verticalRadius,
+                        (long) bounds.maxY() + verticalRadius);
+            }
+        }
+        markSourceJunctionLayers(area, start, requiredLayers);
+    }
+
+    private static void markSourceJunctionLayers(
+            BoundingBox area, StructureStart start, BitSet requiredLayers) {
+        Set<JunctionAnchor> anchors = sourceJunctionAnchors(start);
+        for (JunctionAnchor anchor : anchors) {
+            long deltaX = intervalDistance(area.minX(), area.maxX(), anchor.x(), anchor.x());
+            long deltaZ = intervalDistance(area.minZ(), area.maxZ(), anchor.z(), anchor.z());
+            long horizontalDistanceSquared = deltaX * deltaX + deltaZ * deltaZ;
+            long remainingDistanceSquared = (long) SOURCE_JUNCTION_RADIUS
+                    * SOURCE_JUNCTION_RADIUS - 1L - horizontalDistanceSquared;
+            if (remainingDistanceSquared < 1L) {
+                continue;
+            }
+            int verticalRadius = (int) Math.floor(Math.sqrt(remainingDistanceSquared));
+            markLayers(area, requiredLayers,
+                    (long) anchor.y() - verticalRadius, (long) anchor.y() - 1L);
+        }
+    }
+
+    private static long minimumHorizontalDistanceSquared(BoundingBox area, BoundingBox bounds) {
+        long deltaX = intervalDistance(area.minX(), area.maxX(), bounds.minX(), bounds.maxX());
+        long deltaZ = intervalDistance(area.minZ(), area.maxZ(), bounds.minZ(), bounds.maxZ());
+        return deltaX * deltaX + deltaZ * deltaZ;
+    }
+
+    private static long intervalDistance(int firstMin, int firstMax, int secondMin, int secondMax) {
+        if (firstMax < secondMin) {
+            return (long) secondMin - firstMax;
+        }
+        if (firstMin > secondMax) {
+            return (long) firstMin - secondMax;
+        }
+        return 0L;
+    }
+
+    private static void markLayers(
+            BoundingBox area, BitSet requiredLayers, long minimumY, long maximumY) {
+        long clippedMinimumY = Math.max(area.minY(), minimumY);
+        long clippedMaximumY = Math.min(area.maxY(), maximumY);
+        if (clippedMinimumY > clippedMaximumY) {
+            return;
+        }
+        int fromIndex = Math.toIntExact(clippedMinimumY - area.minY());
+        int toIndex = Math.toIntExact(clippedMaximumY - area.minY() + 1L);
+        requiredLayers.set(fromIndex, toIndex);
+    }
+
+    private static boolean requiresSourceTerrainFill(
+            StructureStart start, IrisStructureTerrain configuredTerrain) {
+        if (start == null || !start.isValid()) {
+            return false;
+        }
+        IrisStructureTerrain terrain = configuredTerrain == null
+                ? new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE)
+                : configuredTerrain;
+        if (terrain.resolvedMode() != IrisStructureTerrainMode.SOURCE) {
+            return false;
+        }
+        TerrainAdjustment adjustment = start.getStructure().terrainAdaptation();
+        return adjustment == TerrainAdjustment.BURY
+                || adjustment == TerrainAdjustment.ENCAPSULATE;
+    }
+
+    static boolean clearsLegacyTemplateAir(StructureStart start, IrisStructureTerrain terrain) {
+        if (start == null || !start.isValid() || terrain == null) {
+            return false;
+        }
+        IrisStructureTerrainMode mode = terrain.resolvedMode();
+        return mode == IrisStructureTerrainMode.ENCASE
+                || mode == IrisStructureTerrainMode.SOURCE
+                && start.getStructure().terrainAdaptation() != TerrainAdjustment.NONE;
+    }
+
+    private static void integrateSourceTerrain(WorldGenLevel world, BoundingBox area,
+                                               StructureStart start,
+                                               SourceTerrainSnapshot sourceTerrain) {
+        if (start == null || !start.isValid()) {
+            return;
+        }
+        TerrainAdjustment adjustment = start.getStructure().terrainAdaptation();
+        if (adjustment == TerrainAdjustment.BURY) {
+            fillBuriedTerrain(world, area, start, requireSourceTerrain(
+                    world, area, start, sourceTerrain));
+        } else if (adjustment == TerrainAdjustment.ENCAPSULATE) {
+            fillEncapsulatedTerrain(world, area, start, requireSourceTerrain(
+                    world, area, start, sourceTerrain));
+        }
+    }
+
+    private static SourceTerrainSnapshot requireSourceTerrain(
+            WorldGenLevel world, BoundingBox area, StructureStart start,
+            SourceTerrainSnapshot sourceTerrain) {
+        return sourceTerrain == null
+                ? captureSourceTerrain(world, area, start, null) : sourceTerrain;
+    }
+
+    private static void fillBuriedTerrain(WorldGenLevel world, BoundingBox area,
+                                          StructureStart start,
+                                          SourceTerrainSnapshot sourceTerrain) {
+        BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
+        for (StructurePiece piece : start.getPieces()) {
+            if (!isSourceRigidPiece(piece)) {
+                continue;
+            }
+            BoundingBox bounds = piece.getBoundingBox();
+            int groundY = bounds.minY();
+            if (piece instanceof PoolElementStructurePiece poolPiece) {
+                groundY += poolPiece.getGroundLevelDelta();
+            }
+            int minX = Math.max(area.minX(), bounds.minX() - SOURCE_BURY_HORIZONTAL_RADIUS);
+            int maxX = Math.min(area.maxX(), bounds.maxX() + SOURCE_BURY_HORIZONTAL_RADIUS);
+            int minY = Math.max(area.minY(), groundY - SOURCE_BURY_VERTICAL_RADIUS);
+            int maxY = Math.min(area.maxY(), groundY + SOURCE_BURY_VERTICAL_RADIUS);
+            int minZ = Math.max(area.minZ(), bounds.minZ() - SOURCE_BURY_HORIZONTAL_RADIUS);
+            int maxZ = Math.min(area.maxZ(), bounds.maxZ() + SOURCE_BURY_HORIZONTAL_RADIUS);
+            for (int x = minX; x <= maxX; x++) {
+                int outX = outset(x, bounds.minX(), bounds.maxX());
+                for (int z = minZ; z <= maxZ; z++) {
+                    int outZ = outset(z, bounds.minZ(), bounds.maxZ());
+                    for (int y = minY; y <= maxY; y++) {
+                        int vertical = Math.abs(y - groundY);
+                        if (!insideBurialEnvelope(outX, vertical, outZ)) {
+                            continue;
+                        }
+                        fillEncaseable(world, position.set(x, y, z), sourceTerrain);
+                    }
+                }
+            }
+        }
+        fillSourceJunctionTerrain(world, area, start, position, sourceTerrain);
+    }
+
+    private static void fillEncapsulatedTerrain(WorldGenLevel world, BoundingBox area,
+                                                StructureStart start,
+                                                SourceTerrainSnapshot sourceTerrain) {
+        BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
+        for (StructurePiece piece : start.getPieces()) {
+            if (!isSourceRigidPiece(piece)) {
+                continue;
+            }
+            BoundingBox bounds = piece.getBoundingBox();
+            int minX = Math.max(area.minX(), bounds.minX() - SOURCE_ENCAPSULATE_RADIUS);
+            int maxX = Math.min(area.maxX(), bounds.maxX() + SOURCE_ENCAPSULATE_RADIUS);
+            int minY = Math.max(area.minY(), bounds.minY() - SOURCE_ENCAPSULATE_RADIUS);
+            int maxY = Math.min(area.maxY(), bounds.maxY() + SOURCE_ENCAPSULATE_RADIUS);
+            int minZ = Math.max(area.minZ(), bounds.minZ() - SOURCE_ENCAPSULATE_RADIUS);
+            int maxZ = Math.min(area.maxZ(), bounds.maxZ() + SOURCE_ENCAPSULATE_RADIUS);
+            for (int x = minX; x <= maxX; x++) {
+                int outX = outset(x, bounds.minX(), bounds.maxX());
+                for (int z = minZ; z <= maxZ; z++) {
+                    int outZ = outset(z, bounds.minZ(), bounds.maxZ());
+                    for (int y = minY; y <= maxY; y++) {
+                        int outY = outset(y, bounds.minY(), bounds.maxY());
+                        if (!insideEncapsulationEnvelope(outX, outY, outZ)) {
+                            continue;
+                        }
+                        fillEncaseable(world, position.set(x, y, z), sourceTerrain);
+                    }
+                }
+            }
+        }
+        fillSourceJunctionTerrain(world, area, start, position, sourceTerrain);
+    }
+
+    static boolean insideBurialEnvelope(int outX, int verticalDistance, int outZ) {
+        long horizontalSquared = (long) outX * outX + (long) outZ * outZ;
+        long verticalSquared = (long) verticalDistance * verticalDistance;
+        return horizontalSquared * 4L + verticalSquared
+                < (long) SOURCE_BURY_VERTICAL_RADIUS * SOURCE_BURY_VERTICAL_RADIUS;
+    }
+
+    static boolean insideEncapsulationEnvelope(int outX, int outY, int outZ) {
+        return (long) outX * outX + (long) outY * outY + (long) outZ * outZ
+                < (long) SOURCE_ENCAPSULATE_RADIUS * SOURCE_ENCAPSULATE_RADIUS;
+    }
+
+    static boolean isSourceRigidPiece(StructurePiece piece) {
+        if (piece == null) {
+            return false;
+        }
+        return !(piece instanceof PoolElementStructurePiece poolPiece)
+                || poolPiece.getElement().getProjection() == StructureTemplatePool.Projection.RIGID;
+    }
+
+    static boolean insideSourceJunctionEnvelope(int deltaX, int deltaY, int deltaZ) {
+        if (deltaY >= 0) {
+            return false;
+        }
+        return (long) deltaX * deltaX + (long) deltaY * deltaY + (long) deltaZ * deltaZ
+                < (long) SOURCE_JUNCTION_RADIUS * SOURCE_JUNCTION_RADIUS;
+    }
+
+    private static void fillSourceJunctionTerrain(WorldGenLevel world, BoundingBox area,
+                                                  StructureStart start,
+                                                  BlockPos.MutableBlockPos position,
+                                                  SourceTerrainSnapshot sourceTerrain) {
+        Set<JunctionAnchor> anchors = sourceJunctionAnchors(start);
+        for (JunctionAnchor anchor : anchors) {
+            int minX = Math.max(area.minX(), anchor.x() - SOURCE_JUNCTION_RADIUS + 1);
+            int maxX = Math.min(area.maxX(), anchor.x() + SOURCE_JUNCTION_RADIUS - 1);
+            int minY = Math.max(area.minY(), anchor.y() - SOURCE_JUNCTION_RADIUS + 1);
+            int maxY = Math.min(area.maxY(), anchor.y() - 1);
+            int minZ = Math.max(area.minZ(), anchor.z() - SOURCE_JUNCTION_RADIUS + 1);
+            int maxZ = Math.min(area.maxZ(), anchor.z() + SOURCE_JUNCTION_RADIUS - 1);
+            for (int x = minX; x <= maxX; x++) {
+                int deltaX = x - anchor.x();
+                for (int z = minZ; z <= maxZ; z++) {
+                    int deltaZ = z - anchor.z();
+                    for (int y = minY; y <= maxY; y++) {
+                        if (insideSourceJunctionEnvelope(deltaX, y - anchor.y(), deltaZ)) {
+                            fillEncaseable(world, position.set(x, y, z), sourceTerrain);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private static Set<JunctionAnchor> sourceJunctionAnchors(StructureStart start) {
+        Set<JunctionAnchor> anchors = new HashSet<>();
+        for (StructurePiece piece : start.getPieces()) {
+            if (!(piece instanceof PoolElementStructurePiece poolPiece)) {
+                continue;
+            }
+            for (JigsawJunction junction : poolPiece.getJunctions()) {
+                anchors.add(new JunctionAnchor(
+                        junction.getSourceX(), junction.getSourceGroundY(), junction.getSourceZ()));
+            }
+        }
+        return anchors;
+    }
+
+    private static int outset(int value, int minimum, int maximum) {
+        if (value < minimum) {
+            return minimum - value;
+        }
+        return Math.max(0, value - maximum);
+    }
+
+    private static void fillEncaseable(WorldGenLevel world, BlockPos position,
+                                       SourceTerrainSnapshot sourceTerrain) {
+        if (isEncaseable(world.getBlockState(position))) {
+            world.setBlock(position, sourceEncaseBlock(world, position, sourceTerrain), 2);
+        }
+    }
+
+    static BlockState sourceEncaseBlock(WorldGenLevel world, BlockPos position) {
+        int minX = Math.subtractExact(position.getX(), SOURCE_MATERIAL_SAMPLE_RADIUS);
+        int minZ = Math.subtractExact(position.getZ(), SOURCE_MATERIAL_SAMPLE_RADIUS);
+        int maxX = Math.addExact(position.getX(), SOURCE_MATERIAL_SAMPLE_RADIUS);
+        int maxZ = Math.addExact(position.getZ(), SOURCE_MATERIAL_SAMPLE_RADIUS);
+        BoundingBox sampleArea = new BoundingBox(minX, position.getY(), minZ,
+                maxX, position.getY(), maxZ);
+        BitSet requiredLayers = new BitSet(1);
+        requiredLayers.set(0);
+        SourceTerrainSnapshot sourceTerrain = SourceTerrainSnapshot.capture(
+                world, sampleArea, requiredLayers);
+        return sourceEncaseBlock(world, position, sourceTerrain);
+    }
+
+    static BlockState sourceEncaseBlock(WorldGenLevel world, BlockPos position,
+                                        SourceTerrainSnapshot sourceTerrain) {
+        BlockPos.MutableBlockPos probe = new BlockPos.MutableBlockPos();
+        for (int distance = 1; distance <= SOURCE_MATERIAL_SAMPLE_RADIUS; distance++) {
+            BlockState sampled = sourceTerrain.stateAt(probe.set(
+                    position.getX() - distance, position.getY(), position.getZ()));
+            if (sampled != null) {
+                return sampled;
+            }
+            sampled = sourceTerrain.stateAt(probe.set(
+                    position.getX() + distance, position.getY(), position.getZ()));
+            if (sampled != null) {
+                return sampled;
+            }
+            sampled = sourceTerrain.stateAt(probe.set(
+                    position.getX(), position.getY(), position.getZ() - distance));
+            if (sampled != null) {
+                return sampled;
+            }
+            sampled = sourceTerrain.stateAt(probe.set(
+                    position.getX(), position.getY(), position.getZ() + distance));
+            if (sampled != null) {
+                return sampled;
+            }
+        }
+        return defaultEncaseBlock(world, position.getY());
+    }
+
+    private static BlockState sourceTerrainBlock(BlockState state) {
+        if (!state.isSolid() || NativeStructureVegetationClearer.isTreeBlock(state)) {
+            return null;
+        }
+        return VANILLA_SOURCE_TERRAIN_BLOCKS.contains(state.getBlock())
+                || state.is(BlockTags.BASE_STONE_OVERWORLD)
+                || state.is(BlockTags.BASE_STONE_NETHER)
+                || state.is(BlockTags.SUBSTRATE_OVERWORLD)
+                || state.is(BlockTags.DIRT)
+                || state.is(BlockTags.SAND)
+                || state.is(BlockTags.TERRACOTTA)
+                || state.is(BlockTags.MUD)
+                || state.is(BlockTags.MOSS_BLOCKS)
+                || state.is(BlockTags.GRASS_BLOCKS)
+                || state.is(BlockTags.NYLIUM)
+                || state.is(BlockTags.SNOW)
+                || state.is(BlockTags.ICE)
+                || state.is(BlockTags.CORAL_BLOCKS)
+                || state.is(BlockTags.SOUL_FIRE_BASE_BLOCKS)
+                ? state : null;
+    }
+
     static List<BoundingBox> contentPieceBounds(StructureStart start) {
         List<BoundingBox> bounds = new ArrayList<>(start.getPieces().size());
         for (StructurePiece piece : start.getPieces()) {
-            if (!NativeStructureReferenceEnvelope.isMarker(piece)) {
-                bounds.add(piece.getBoundingBox());
-            }
+            bounds.add(piece.getBoundingBox());
         }
         return List.copyOf(bounds);
     }
@@ -128,18 +523,84 @@ public final class NativeStructureTerrainIntegrator {
     static StructureCarvingFootprint carveFootprint(StructureStart start, int horizontalPadding,
                                                     Supplier<StructureTemplateManager> templates) {
         CarveFootprintKey key = new CarveFootprintKey(start, horizontalPadding);
-        StructureCarvingFootprint cached = CARVE_FOOTPRINTS.get(key);
+        StructureCarvingFootprint cached = cachedCarveFootprint(key);
         if (cached != null) {
             return cached;
         }
-        StructureCarvingFootprint footprint = StructureCarvingFootprint.fromColumns(
-                sink -> emitCarveColumns(start, templates, sink), horizontalPadding, MAX_CARVE_COLUMNS);
-        if (footprint == null) {
-            throw new IllegalStateException("Native structure carve footprint is empty or exceeds "
-                    + MAX_CARVE_COLUMNS + " columns");
+        CompletableFuture<StructureCarvingFootprint> build = new CompletableFuture<>();
+        CompletableFuture<StructureCarvingFootprint> active = CARVE_FOOTPRINT_BUILDS.putIfAbsent(key, build);
+        if (active != null) {
+            return awaitCarveFootprint(active);
+        }
+        try {
+            StructureCarvingFootprint footprint = StructureCarvingFootprint.fromColumns(
+                    sink -> emitCarveColumns(start, templates, sink), horizontalPadding, MAX_CARVE_COLUMNS);
+            if (footprint == null) {
+                throw new IllegalStateException("Native structure carve footprint is empty or exceeds "
+                        + MAX_CARVE_COLUMNS + " columns");
+            }
+            cacheCarveFootprint(key, footprint);
+            build.complete(footprint);
+            return footprint;
+        } catch (RuntimeException | Error error) {
+            build.completeExceptionally(error);
+            throw error;
+        } finally {
+            CARVE_FOOTPRINT_BUILDS.remove(key, build);
+        }
+    }
+
+    static int cachedCarveFootprintCells() {
+        synchronized (CARVE_FOOTPRINTS) {
+            return cachedCarveCells;
+        }
+    }
+
+    static int maximumCachedCarveFootprintCells() {
+        return MAX_CACHED_CARVE_CELLS;
+    }
+
+    private static StructureCarvingFootprint cachedCarveFootprint(CarveFootprintKey key) {
+        synchronized (CARVE_FOOTPRINTS) {
+            CachedCarveFootprint cached = CARVE_FOOTPRINTS.get(key);
+            return cached == null ? null : cached.footprint();
+        }
+    }
+
+    private static StructureCarvingFootprint awaitCarveFootprint(
+            CompletableFuture<StructureCarvingFootprint> future) {
+        try {
+            return future.join();
+        } catch (CompletionException error) {
+            Throwable cause = error.getCause();
+            if (cause instanceof RuntimeException runtime) {
+                throw runtime;
+            }
+            if (cause instanceof Error fatal) {
+                throw fatal;
+            }
+            throw new IllegalStateException("Native structure carve footprint build failed", cause);
+        }
+    }
+
+    private static void cacheCarveFootprint(CarveFootprintKey key,
+                                            StructureCarvingFootprint footprint) {
+        int cells = Math.multiplyExact(footprint.width(), footprint.depth());
+        synchronized (CARVE_FOOTPRINTS) {
+            CachedCarveFootprint previous = CARVE_FOOTPRINTS.remove(key);
+            if (previous != null) {
+                cachedCarveCells -= previous.cells();
+            }
+            while (!CARVE_FOOTPRINTS.isEmpty()
+                    && cachedCarveCells + cells > MAX_CACHED_CARVE_CELLS) {
+                Map.Entry<CarveFootprintKey, CachedCarveFootprint> eldest =
+                        CARVE_FOOTPRINTS.entrySet().iterator().next();
+                cachedCarveCells -= eldest.getValue().cells();
+                CARVE_FOOTPRINTS.remove(eldest.getKey());
+            }
+            CARVE_FOOTPRINTS.put(key, new CachedCarveFootprint(footprint, cells));
+            cachedCarveCells += cells;
         }
-        CARVE_FOOTPRINTS.put(key, footprint);
-        return footprint;
     }
 
     static OrganicCarve organicCarve(StructureCarvingFootprint footprint, IrisStructureTerrain terrain,
@@ -235,9 +696,6 @@ public final class NativeStructureTerrainIntegrator {
                                             Supplier<StructureTemplateManager> templates,
                                             StructureCarvingFootprint.ColumnSink sink) {
         for (StructurePiece piece : start.getPieces()) {
-            if (NativeStructureReferenceEnvelope.isMarker(piece)) {
-                continue;
-            }
             BoundingBox bounds = piece.getBoundingBox();
             if (!(piece instanceof PoolElementStructurePiece poolPiece)
                     || !emitTemplateColumns(pieceTemplates(poolPiece, templates),
@@ -373,7 +831,7 @@ public final class NativeStructureTerrainIntegrator {
                             continue;
                         }
                         BlockState fill = palette == null
-                                ? defaultEncaseBlock(y)
+                                ? defaultEncaseBlock(world, y)
                                 : Objects.requireNonNull(
                                         paletteBlockResolver.resolve(palette, rng, x, y, z),
                                         "Encase palette returned no block for " + structureId + " at "
@@ -393,6 +851,41 @@ public final class NativeStructureTerrainIntegrator {
         return y < 0 ? Blocks.DEEPSLATE.defaultBlockState() : Blocks.STONE.defaultBlockState();
     }
 
+    static BlockState defaultEncaseBlock(WorldGenLevel world, int y) {
+        ServerLevel level = world == null ? null : world.getLevel();
+        if (level == null) {
+            return defaultEncaseBlock(y);
+        }
+        Holder<DimensionType> dimensionType = level.dimensionTypeRegistration();
+        ResourceKey<DimensionType> dimensionTypeKey = dimensionType.unwrapKey().orElse(null);
+        return defaultEncaseBlock(level.dimension(), dimensionTypeKey, dimensionType.value(), y);
+    }
+
+    static BlockState defaultEncaseBlock(ResourceKey<Level> dimension, int y) {
+        return defaultEncaseBlock(dimension, null, null, y);
+    }
+
+    static BlockState defaultEncaseBlock(ResourceKey<Level> dimension,
+                                         ResourceKey<DimensionType> dimensionTypeKey,
+                                         DimensionType dimensionType, int y) {
+        if (Level.NETHER.equals(dimension)) {
+            return Blocks.NETHERRACK.defaultBlockState();
+        }
+        if (Level.END.equals(dimension)) {
+            return Blocks.END_STONE.defaultBlockState();
+        }
+        if (BuiltinDimensionTypes.NETHER.equals(dimensionTypeKey)
+                || dimensionType != null && dimensionType.hasCeiling() && !dimensionType.hasSkyLight()) {
+            return Blocks.NETHERRACK.defaultBlockState();
+        }
+        if (BuiltinDimensionTypes.END.equals(dimensionTypeKey)
+                || dimensionType != null && (dimensionType.hasEnderDragonFight()
+                || dimensionType.hasEndFlashes())) {
+            return Blocks.END_STONE.defaultBlockState();
+        }
+        return defaultEncaseBlock(y);
+    }
+
     private static void carvePieceBoxes(WorldGenLevel world, BoundingBox area, StructureStart start,
                                         IrisStructureTerrain terrain) {
         BlockState air = Blocks.AIR.defaultBlockState();
@@ -431,9 +924,6 @@ public final class NativeStructureTerrainIntegrator {
                                        StructureStart start,
                                        Supplier<StructureTemplateManager> templates) {
         for (StructurePiece piece : start.getPieces()) {
-            if (NativeStructureReferenceEnvelope.isMarker(piece)) {
-                continue;
-            }
             if (!(piece instanceof PoolElementStructurePiece poolPiece)
                     || poolPiece.getElement().getProjection() != StructureTemplatePool.Projection.RIGID
                     || !intersects(poolPiece.getBoundingBox(), area)) {
@@ -496,6 +986,80 @@ public final class NativeStructureTerrainIntegrator {
     private record CarveFootprintKey(StructureStart start, int padding) {
     }
 
+    private record CachedCarveFootprint(StructureCarvingFootprint footprint, int cells) {
+    }
+
+    private record JunctionAnchor(int x, int y, int z) {
+    }
+
+    static final class SourceTerrainSnapshot {
+        private final BoundingBox area;
+        private final int width;
+        private final BlockState[][] statesByLayer;
+        private final int sampledCells;
+
+        private SourceTerrainSnapshot(BoundingBox area, int width,
+                                      BlockState[][] statesByLayer, int sampledCells) {
+            this.area = area;
+            this.width = width;
+            this.statesByLayer = statesByLayer;
+            this.sampledCells = sampledCells;
+        }
+
+        static SourceTerrainSnapshot capture(
+                WorldGenLevel world, BoundingBox area, BitSet requiredLayers) {
+            Objects.requireNonNull(world, "Source terrain snapshot requires a generation level");
+            Objects.requireNonNull(area, "Source terrain snapshot requires writable bounds");
+            Objects.requireNonNull(requiredLayers, "Source terrain snapshot requires sampled layers");
+            int width = area.getXSpan();
+            int depth = area.getZSpan();
+            int height = area.getYSpan();
+            int horizontalCells = Math.multiplyExact(width, depth);
+            BlockState[][] statesByLayer = new BlockState[height][];
+            int sampledCells = 0;
+            BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
+            for (int layer = requiredLayers.nextSetBit(0);
+                 layer >= 0; layer = requiredLayers.nextSetBit(layer + 1)) {
+                if (layer >= height) {
+                    throw new IllegalArgumentException(
+                            "Source terrain snapshot layer exceeds writable bounds: " + layer);
+                }
+                BlockState[] states = new BlockState[horizontalCells];
+                statesByLayer[layer] = states;
+                sampledCells = Math.addExact(sampledCells, horizontalCells);
+                int y = Math.addExact(area.minY(), layer);
+                for (int z = area.minZ(); z <= area.maxZ(); z++) {
+                    for (int x = area.minX(); x <= area.maxX(); x++) {
+                        int index = (z - area.minZ()) * width + x - area.minX();
+                        states[index] = sourceTerrainBlock(
+                                world.getBlockState(position.set(x, y, z)));
+                    }
+                }
+            }
+            return new SourceTerrainSnapshot(new BoundingBox(
+                    area.minX(), area.minY(), area.minZ(),
+                    area.maxX(), area.maxY(), area.maxZ()), width,
+                    statesByLayer, sampledCells);
+        }
+
+        BlockState stateAt(BlockPos position) {
+            if (!area.isInside(position)) {
+                return null;
+            }
+            BlockState[] states = statesByLayer[position.getY() - area.minY()];
+            if (states == null) {
+                return null;
+            }
+            int index = (position.getZ() - area.minZ()) * width
+                    + position.getX() - area.minX();
+            return states[index];
+        }
+
+        int sampledCells() {
+            return sampledCells;
+        }
+    }
+
     record OrganicCarve(StructureCarvingFootprint footprint, IrisStructureCarveShape shape,
                         int horizontalPadding, int ceilingPadding, int floorPadding,
                         double strength, double frequency, CNG blob, CNG ceilingRoll, CNG floorRoll,

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureVanillaLocator.java

@@ -0,0 +1,224 @@
+package art.arcane.iris.nativegen;
+
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.SectionPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureCheckResult;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.placement.ConcentricRingsStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public final class NativeStructureVanillaLocator {
+    private NativeStructureVanillaLocator() {
+    }
+
+    public static Candidate predict(ServerLevel level, HolderSet<Structure> holders,
+                                    BlockPos origin, int radius, boolean findUnexplored) {
+        if (SharedConstants.DEBUG_DISABLE_FEATURES
+                || !level.getServer().getWorldGenSettings().options().generateStructures()) {
+            return null;
+        }
+        ChunkGeneratorStructureState state = level.getChunkSource().getGeneratorState();
+        Map<StructurePlacement, Set<Holder<Structure>>> byPlacement = new LinkedHashMap<>();
+        for (Holder<Structure> holder : holders) {
+            for (StructurePlacement placement : state.getPlacementsForStructure(holder)) {
+                byPlacement.computeIfAbsent(placement, ignored -> new LinkedHashSet<>()).add(holder);
+            }
+        }
+        if (byPlacement.isEmpty()) {
+            return null;
+        }
+
+        StructureManager structureManager = level.structureManager();
+        Candidate best = null;
+        double bestDistance = Double.MAX_VALUE;
+        List<Map.Entry<RandomSpreadStructurePlacement, Set<Holder<Structure>>>> randomPlacements =
+                new ArrayList<>(byPlacement.size());
+        for (Map.Entry<StructurePlacement, Set<Holder<Structure>>> entry : byPlacement.entrySet()) {
+            StructurePlacement placement = entry.getKey();
+            if (placement instanceof ConcentricRingsStructurePlacement concentric) {
+                Candidate candidate = predictConcentric(
+                        entry.getValue(), level, structureManager, origin, findUnexplored,
+                        state, concentric);
+                if (candidate != null) {
+                    double distance = origin.distSqr(candidate.result().getFirst());
+                    if (distance < bestDistance) {
+                        best = candidate;
+                        bestDistance = distance;
+                    }
+                }
+            } else if (placement instanceof RandomSpreadStructurePlacement randomSpread) {
+                randomPlacements.add(Map.entry(randomSpread, entry.getValue()));
+            }
+        }
+
+        int centerChunkX = SectionPos.blockToSectionCoord(origin.getX());
+        int centerChunkZ = SectionPos.blockToSectionCoord(origin.getZ());
+        int searchRadius = Math.max(0, radius);
+        for (int ring = 0; ring <= searchRadius; ring++) {
+            boolean foundInRing = false;
+            for (Map.Entry<RandomSpreadStructurePlacement, Set<Holder<Structure>>> entry
+                    : randomPlacements) {
+                Candidate candidate = predictRandomSpread(
+                        entry.getValue(), level, structureManager,
+                        centerChunkX, centerChunkZ, ring, findUnexplored,
+                        state.getLevelSeed(), entry.getKey());
+                if (candidate == null) {
+                    continue;
+                }
+                foundInRing = true;
+                double distance = origin.distSqr(candidate.result().getFirst());
+                if (distance < bestDistance) {
+                    best = candidate;
+                    bestDistance = distance;
+                }
+            }
+            if (foundInRing) {
+                return best;
+            }
+        }
+        return best;
+    }
+
+    private static Candidate predictConcentric(Set<Holder<Structure>> holders,
+                                                ServerLevel level,
+                                                StructureManager structureManager,
+                                                BlockPos origin,
+                                                boolean findUnexplored,
+                                                ChunkGeneratorStructureState state,
+                                                ConcentricRingsStructurePlacement placement) {
+        List<ChunkPos> positions = state.getRingPositionsFor(placement);
+        if (positions == null) {
+            throw new IllegalStateException(
+                    "Tried to locate structures for an unavailable concentric placement");
+        }
+        Candidate best = null;
+        double bestDistance = Double.MAX_VALUE;
+        for (ChunkPos position : positions) {
+            BlockPos locatePosition = new BlockPos(
+                    SectionPos.sectionToBlockCoord(position.x(), 8),
+                    32,
+                    SectionPos.sectionToBlockCoord(position.z(), 8));
+            double distance = locatePosition.distSqr(origin);
+            if (best != null && distance >= bestDistance) {
+                continue;
+            }
+            Candidate candidate = predictAt(
+                    holders, level, structureManager, findUnexplored, placement, position);
+            if (candidate != null) {
+                best = candidate;
+                bestDistance = distance;
+            }
+        }
+        return best;
+    }
+
+    private static Candidate predictRandomSpread(Set<Holder<Structure>> holders,
+                                                  ServerLevel level,
+                                                  StructureManager structureManager,
+                                                  int centerChunkX, int centerChunkZ,
+                                                  int ring, boolean findUnexplored,
+                                                  long seed,
+                                                  RandomSpreadStructurePlacement placement) {
+        int spacing = placement.spacing();
+        for (int offsetX = -ring; offsetX <= ring; offsetX++) {
+            boolean edgeX = offsetX == -ring || offsetX == ring;
+            for (int offsetZ = -ring; offsetZ <= ring; offsetZ++) {
+                boolean edgeZ = offsetZ == -ring || offsetZ == ring;
+                if (!edgeX && !edgeZ) {
+                    continue;
+                }
+                int gridChunkX = centerChunkX + spacing * offsetX;
+                int gridChunkZ = centerChunkZ + spacing * offsetZ;
+                ChunkPos candidatePosition = placement.getPotentialStructureChunk(
+                        seed, gridChunkX, gridChunkZ);
+                Candidate candidate = predictAt(
+                        holders, level, structureManager,
+                        findUnexplored, placement, candidatePosition);
+                if (candidate != null) {
+                    return candidate;
+                }
+            }
+        }
+        return null;
+    }
+
+    private static Candidate predictAt(Set<Holder<Structure>> holders,
+                                       ServerLevel level,
+                                       StructureManager structureManager,
+                                       boolean findUnexplored,
+                                       StructurePlacement placement,
+                                       ChunkPos candidatePosition) {
+        for (Holder<Structure> holder : holders) {
+            Structure structure = holder.value();
+            StructureCheckResult result = structureManager.checkStructurePresence(
+                    candidatePosition, structure, placement, findUnexplored);
+            if (result == StructureCheckResult.START_NOT_PRESENT) {
+                continue;
+            }
+            if (!findUnexplored && result == StructureCheckResult.START_PRESENT) {
+                return new Candidate(
+                        Pair.of(placement.getLocatePos(candidatePosition), holder), null);
+            }
+            ChunkAccess chunk = level.getChunk(
+                    candidatePosition.x(), candidatePosition.z(), ChunkStatus.STRUCTURE_STARTS);
+            StructureStart start = structureManager.getStartForStructure(
+                    SectionPos.bottomOf(chunk), structure, chunk);
+            if (start == null || !start.isValid()
+                    || findUnexplored && !start.canBeReferenced()) {
+                continue;
+            }
+            return new Candidate(
+                    Pair.of(placement.getLocatePos(start.getChunkPos()), holder),
+                    findUnexplored ? start : null);
+        }
+        return null;
+    }
+
+    public static final class Candidate {
+        private final Pair<BlockPos, Holder<Structure>> result;
+        private final StructureStart referenceStart;
+        private final AtomicBoolean committed;
+
+        private Candidate(Pair<BlockPos, Holder<Structure>> result,
+                          StructureStart referenceStart) {
+            this.result = result;
+            this.referenceStart = referenceStart;
+            this.committed = new AtomicBoolean();
+        }
+
+        public Pair<BlockPos, Holder<Structure>> result() {
+            return result;
+        }
+
+        public boolean reference(StructureManager structureManager) {
+            if (referenceStart == null || !committed.compareAndSet(false, true)) {
+                return false;
+            }
+            if (!referenceStart.canBeReferenced()) {
+                return false;
+            }
+            structureManager.addReference(referenceStart);
+            return true;
+        }
+    }
+}

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureVegetationClearer.java

@@ -43,13 +43,17 @@ public final class NativeStructureVegetationClearer {
         }
         boolean[] clearColumns = new boolean[area.getXSpan() * area.getZSpan()];
         for (VegetationTarget target : targets) {
-            if (target != null && target.force() && target.start() != null && target.start().isValid()) {
+            if (shouldProcessTarget(target)) {
                 markVegetationColumns(area, snapshot, target, clearColumns);
             }
         }
         clearVegetationColumns(world, area, snapshot, clearColumns);
     }
 
+    static boolean shouldProcessTarget(VegetationTarget target) {
+        return target != null && target.start() != null && target.start().isValid();
+    }
+
     private static VegetationSnapshot captureVegetation(ChunkAccess chunk, BoundingBox area) {
         int width = area.getXSpan();
         int depth = area.getZSpan();
@@ -100,9 +104,6 @@ public final class NativeStructureVegetationClearer {
         int[] pieceTops = new int[clearColumns.length];
         Arrays.fill(pieceTops, Integer.MIN_VALUE);
         for (StructurePiece piece : target.start().getPieces()) {
-            if (NativeStructureReferenceEnvelope.isMarker(piece)) {
-                continue;
-            }
             BoundingBox bounds = piece.getBoundingBox();
             int minX = Math.max(area.minX(), bounds.minX());
             int maxX = Math.min(area.maxX(), bounds.maxX());

adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureVerticalPlacer.java

@@ -15,8 +15,11 @@ import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
 import net.minecraft.world.level.levelgen.structure.pools.JigsawJunction;
 import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
 import net.minecraft.world.level.levelgen.structure.structures.JungleTemplePiece;
+import net.minecraft.world.level.levelgen.structure.structures.JungleTempleStructure;
 import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -39,11 +42,11 @@ public final class NativeStructureVerticalPlacer {
                                              boolean underground, boolean preserveSourceY,
                                              IrisStructureYBand yBand,
                                              IntBinaryOperator surfaceHeight) {
-        if (isOceanMonument(structureId)) {
+        if (isOceanMonument(start, structureId)) {
             return alignOceanMonumentToSeaLevel(
                     start, requestedOffset, seaLevel, worldMinY, worldMaxYExclusive);
         }
-        if (isAdjustedScatteredStructure(structureId)) {
+        if (isAdjustedScatteredStructure(start, structureId)) {
             return alignScatteredStructureToSurface(
                     start, structureId, requestedOffset, worldMinY, worldMaxYExclusive, surfaceHeight);
         }
@@ -169,18 +172,28 @@ public final class NativeStructureVerticalPlacer {
     static void ensureMonumentSeaLevelAlignment(StructureStart start, String structureId,
                                                  int configuredOffset, int seaLevel,
                                                  int worldMinY, int worldMaxYExclusive) {
-        if (isOceanMonument(structureId)) {
+        if (!isOceanMonument(start, structureId)) {
+            return;
+        }
+        synchronized (start) {
             alignOceanMonumentToSeaLevel(
                     start, configuredOffset, seaLevel, worldMinY, worldMaxYExclusive);
         }
     }
 
-    private static boolean isOceanMonument(String structureId) {
-        return OCEAN_MONUMENT_ID.equals(structureId);
+    private static boolean isOceanMonument(StructureStart start, String structureId) {
+        return OCEAN_MONUMENT_ID.equals(structureId)
+                && start != null
+                && start.getStructure() instanceof OceanMonumentStructure;
     }
 
-    private static boolean isAdjustedScatteredStructure(String structureId) {
-        return DESERT_PYRAMID_ID.equals(structureId) || JUNGLE_PYRAMID_ID.equals(structureId);
+    private static boolean isAdjustedScatteredStructure(StructureStart start, String structureId) {
+        if (start == null) {
+            return false;
+        }
+        Structure source = start.getStructure();
+        return (DESERT_PYRAMID_ID.equals(structureId) && source instanceof DesertPyramidStructure)
+                || (JUNGLE_PYRAMID_ID.equals(structureId) && source instanceof JungleTempleStructure);
     }
 
     private static ScatteredFeaturePiece requireAdjustedScatteredPiece(StructureStart start,
@@ -252,9 +265,15 @@ public final class NativeStructureVerticalPlacer {
     private static OceanMonumentPieces.MonumentBuilding requireOceanMonumentBuilding(StructureStart start) {
         Objects.requireNonNull(start, "Ocean monument start must not be null");
         List<StructurePiece> pieces = start.getPieces();
-        if (pieces.size() != 1 || !(pieces.get(0) instanceof OceanMonumentPieces.MonumentBuilding building)) {
+        OceanMonumentPieces.MonumentBuilding building = null;
+        for (StructurePiece piece : pieces) {
+            if (piece instanceof OceanMonumentPieces.MonumentBuilding monumentBuilding) {
+                building = monumentBuilding;
+            }
+        }
+        if (pieces.size() != 1 || building == null) {
             throw new IllegalStateException("minecraft:monument must contain exactly one MonumentBuilding, found "
-                    + pieces.size() + " top-level pieces");
+                    + pieces.size() + " pieces");
         }
         return building;
     }

adapters/modded-common/src/main/java/art/arcane/iris/modded/IrisModdedChunkGenerator.java

@@ -27,7 +27,8 @@ import art.arcane.iris.engine.framework.GenerationSessionLease;
 import art.arcane.iris.engine.framework.NativeStructureStartPlan;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.nativegen.NativeStructureStartInjector;
-import art.arcane.iris.nativegen.NativeStructureLocateResults;
+import art.arcane.iris.nativegen.NativeStructureReferenceRepair;
+import art.arcane.iris.nativegen.NativeStructureVanillaLocator;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.spi.PlatformBiome;
 import art.arcane.iris.spi.PlatformBlockState;
@@ -294,14 +295,14 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         Engine current = engine();
         try (GenerationSessionLease lease = requireGenerationLease(current, "modded_structure_locate");
              IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
-            Pair<BlockPos, Holder<Structure>> irisPlaced = nativeStructures.findNearestIrisStructure(
-                    level, holders, pos, Math.max(1, radius), findUnexplored, current);
             HolderSet<Structure> reachable = nativeStructures.filterReachableNativeStructures(
                     level, holders, current);
-            Pair<BlockPos, Holder<Structure>> nativeLocated = reachable.size() == 0
-                    ? null
-                    : super.findNearestMapStructure(level, reachable, pos, radius, findUnexplored);
-            return NativeStructureLocateResults.nearest(pos, irisPlaced, nativeLocated);
+            NativeStructureVanillaLocator.Candidate nativeCandidate =
+                    reachable.size() == 0 ? null
+                            : NativeStructureVanillaLocator.predict(
+                                    level, reachable, pos, radius, findUnexplored);
+            return nativeStructures.findNearestIrisStructure(
+                    level, holders, pos, Math.max(0, radius), findUnexplored, current, nativeCandidate);
         }
     }
 
@@ -879,7 +880,8 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         Engine current = engine();
         try (GenerationSessionLease lease = requireGenerationLease(current, "modded_create_references");
              IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
-            super.createReferences(level, structureManager, chunk);
+            NativeStructureReferenceRepair.createReferences(
+                    current, level, structureManager, chunk);
         }
     }
 

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedForcedDatapack.java

@@ -23,7 +23,7 @@ import art.arcane.iris.core.localization.IrisLanguage;
 import art.arcane.iris.core.localization.RuntimeUiMessages;
 import art.arcane.iris.core.nms.datapack.DataVersion;
 import art.arcane.iris.core.nms.datapack.IDataFixer;
-import art.arcane.iris.core.pack.PackValidationRegistry;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.pack.PackValidationResult;
 import art.arcane.iris.core.pack.PackValidator;
 import art.arcane.iris.engine.object.IrisDimension;
@@ -74,7 +74,6 @@ public final class ModdedForcedDatapack {
     // v2: custom biomes now inherit their vanilla derivative's biome tags, so every already-published pack has
     // to regenerate once.
     private static final String HASH_SALT = "iris-forced-datapack-v2";
-    private static final String GIT_DIRECTORY = ".git";
     private static final long PACKS_HASH_TTL_NANOS = 2_000_000_000L;
     private static final Object LOCK = new Object();
     private static final AtomicBoolean LOADED = new AtomicBoolean(false);
@@ -147,13 +146,13 @@ public final class ModdedForcedDatapack {
             return;
         }
         Path packsRoot = packsRoot();
-        File[] packs = packsRoot.toFile().listFiles(File::isDirectory);
-        if (packs == null || packs.length == 0) {
+        List<File> packs = PackDirectoryResolver.listVisiblePackDirectories(packsRoot.toFile());
+        if (packs.isEmpty()) {
             return;
         }
         LOGGER.error("===============================================================");
         LOGGER.error("Iris forced datapack '{}' was never loaded by this server.", PACK_ID);
-        LOGGER.error("{} installed pack(s) at {} contributed no dimension types or custom biomes.", packs.length, packsRoot);
+        LOGGER.error("{} installed pack(s) at {} contributed no dimension types or custom biomes.", packs.size(), packsRoot);
         LOGGER.error("Datapack source injection failed for this loader (mixin/event not applied), so world creation will fail and restarting will not fix it.");
         LOGGER.error("===============================================================");
     }
@@ -360,8 +359,8 @@ public final class ModdedForcedDatapack {
             Files.walkFileTree(root, new SimpleFileVisitor<Path>() {
                 @Override
                 public FileVisitResult preVisitDirectory(Path directory, BasicFileAttributes attributes) {
-                    // Studio packs can be git checkouts; .git churns constantly and never reaches the datapack.
-                    return GIT_DIRECTORY.equals(directory.getFileName().toString())
+                    return !directory.equals(root)
+                            && PackDirectoryResolver.isHiddenName(directory.getFileName().toString())
                             ? FileVisitResult.SKIP_SUBTREE
                             : FileVisitResult.CONTINUE;
                 }
@@ -397,16 +396,10 @@ public final class ModdedForcedDatapack {
         int packCount = 0;
         KList<String> presetIds = new KList<>();
         File root = packsRoot().toFile();
-        File[] packs = root.listFiles(File::isDirectory);
-        if (packs == null && root.exists()) {
-            throw new IOException("Iris could not read installed pack directory " + root.getAbsolutePath());
-        }
-        if (packs != null) {
-            Arrays.sort(packs, Comparator.comparing(File::getName));
-            for (File pack : packs) {
-                if (stagePack(pack, fixer, stagingDirectory, seenBiomes, presetIds)) {
-                    packCount++;
-                }
+        List<File> packs = PackDirectoryResolver.listVisiblePackDirectoriesOrThrow(root);
+        for (File pack : packs) {
+            if (stagePack(pack, fixer, stagingDirectory, seenBiomes, presetIds)) {
+                packCount++;
             }
         }
 
@@ -431,8 +424,7 @@ public final class ModdedForcedDatapack {
                                      KList<String> presetIds) throws IOException {
         PackValidationResult validation;
         try {
-            validation = PackValidator.validate(sourcePack);
-            PackValidationRegistry.publish(validation);
+            validation = PackValidator.validateForDatapackBootstrap(sourcePack);
         } catch (Throwable validationFailure) {
             LOGGER.error("Iris excluded pack '{}' from Create World because validation failed",
                     sourcePack.getName(), validationFailure);

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedNativeStructureStage.java

@@ -21,17 +21,21 @@ package art.arcane.iris.modded;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.IrisStructureLocator;
 import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
-import art.arcane.iris.engine.framework.NativeStructurePlacementPlanner;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
 import art.arcane.iris.engine.framework.NativeStructureStartPlan;
 import art.arcane.iris.engine.object.IrisMaterialPalette;
 import art.arcane.iris.engine.object.IrisNativeStructureDecision;
 import art.arcane.iris.nativegen.NativeStructureGenerationException;
+import art.arcane.iris.nativegen.NativeStructureLocatePersistence;
+import art.arcane.iris.nativegen.NativeStructureLocateResults;
+import art.arcane.iris.nativegen.NativeStructureOwnershipRecovery;
 import art.arcane.iris.nativegen.NativeStructurePostProcessor;
 import art.arcane.iris.nativegen.NativeStructureReferenceEnvelope;
 import art.arcane.iris.nativegen.NativeStructureSurfaceFitter;
 import art.arcane.iris.nativegen.NativeStructureTerrainIntegrator;
 import art.arcane.iris.nativegen.NativeStructureVegetationClearer;
 import art.arcane.iris.nativegen.NativeStructureVerticalPlacer;
+import art.arcane.iris.nativegen.NativeStructureVanillaLocator;
 import art.arcane.iris.nativegen.WorldgenTerrainHeightmaps;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.volmlib.util.math.RNG;
@@ -60,6 +64,7 @@ import net.minecraft.world.level.levelgen.structure.StructureStart;
 import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
 
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -85,42 +90,85 @@ final class ModdedNativeStructureStage {
     Pair<BlockPos, Holder<Structure>> findNearestIrisStructure(ServerLevel level,
                                                               HolderSet<Structure> holders,
                                                               BlockPos pos, int radius, boolean findUnexplored,
-                                                              Engine current) {
-        if (findUnexplored) {
-            return null;
-        }
+                                                              Engine current,
+                                                              NativeStructureVanillaLocator.Candidate nativeCandidate) {
+        Pair<BlockPos, Holder<Structure>> nativeLocated =
+                nativeCandidate == null ? null : nativeCandidate.result();
+        Runnable nativeReference = () -> {
+            if (nativeCandidate != null) {
+                nativeCandidate.reference(level.structureManager());
+            }
+        };
         Registry<Structure> registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE);
-        BlockPos best = null;
-        Holder<Structure> bestHolder = null;
-        long bestDistance = Long.MAX_VALUE;
+        List<IrisNativeLocateSearch> searches = new ArrayList<>(holders.size());
+        NativeStructureLocatePersistence.ProbeBudget budget = NativeStructureLocatePersistence.probeBudget();
         for (Holder<Structure> holder : holders) {
             Identifier id = registry.getKey(holder.value());
             if (id == null) {
                 throw new IllegalStateException("Native structure locate received an unregistered structure holder");
             }
             String structureId = id.toString();
-            if (!IrisStructureLocator.isPlaced(current, structureId)) {
+            if (!IrisStructureLocator.hasNativePlacement(current, structureId)) {
                 continue;
             }
-            IrisStructureLocator.LocateResult result = IrisStructureLocator.locate(
-                    current, structureId, pos.getX(), pos.getZ(), radius);
-            if (result.status() == IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED) {
-                throw new IllegalStateException("Iris structure locate reached its safety limit for "
-                        + structureId + " within " + radius + " chunks");
-            }
-            if (!result.found()) {
-                continue;
-            }
-            long dx = (long) result.originX() - pos.getX();
-            long dz = (long) result.originZ() - pos.getZ();
-            long distance = dx * dx + dz * dz;
-            if (distance < bestDistance) {
-                bestDistance = distance;
-                best = new BlockPos(result.originX(), result.baseY(), result.originZ());
-                bestHolder = holder;
-            }
+            NativeStructureLocatePersistence.Probe probe = NativeStructureLocatePersistence.probe(
+                    level, holder.value(), findUnexplored, budget);
+            searches.add(new IrisNativeLocateSearch(
+                    holder, structureId, NativeStructureLocatePersistence.search(
+                    current, structureId, pos.getX(), pos.getZ(), radius, probe)));
         }
-        return best == null ? null : Pair.of(best, bestHolder);
+        searches.sort(Comparator.comparing(IrisNativeLocateSearch::structureId));
+        for (int attempt = 0; attempt < NativeStructureLocatePersistence.MAX_SELECTED_CANDIDATE_RETRIES; attempt++) {
+            IrisNativeLocateSearch bestSearch = null;
+            IrisStructureLocator.LocateResult bestResult = null;
+            long bestDistance = Long.MAX_VALUE;
+            for (IrisNativeLocateSearch search : searches) {
+                IrisStructureLocator.LocateResult result = search.search().predict();
+                if (result.status() == IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED) {
+                    throw new IllegalStateException("Iris structure locate reached its safety limit for "
+                            + search.structureId() + " within " + radius + " placement rings");
+                }
+                if (!result.found()) {
+                    continue;
+                }
+                long dx = (long) result.originX() - pos.getX();
+                long dz = (long) result.originZ() - pos.getZ();
+                long distance = dx * dx + dz * dz;
+                if (distance < bestDistance) {
+                    bestDistance = distance;
+                    bestSearch = search;
+                    bestResult = result;
+                }
+            }
+            if (bestSearch == null) {
+                return NativeStructureLocateResults.selectAndReference(
+                        pos, null, () -> { }, nativeLocated, nativeReference);
+            }
+            Pair<BlockPos, Holder<Structure>> predicted = Pair.of(
+                    new BlockPos(bestResult.originX(), bestResult.baseY(), bestResult.originZ()),
+                    bestSearch.holder());
+            if (NativeStructureLocateResults.nearest(pos, predicted, nativeLocated) != predicted) {
+                return NativeStructureLocateResults.selectAndReference(
+                        pos, predicted, () -> { }, nativeLocated, nativeReference);
+            }
+            NativeStructureLocatePersistence.VerifiedStart verified =
+                    bestSearch.search().verify(bestResult);
+            if (verified == null) {
+                bestSearch.search().reject(bestResult);
+                continue;
+            }
+            BlockPos located = new BlockPos(
+                    bestResult.originX(), verified.ownership().locatorY(),
+                    bestResult.originZ());
+            Pair<BlockPos, Holder<Structure>> irisLocated = Pair.of(located, bestSearch.holder());
+            IrisNativeLocateSearch selectedSearch = bestSearch;
+            NativeStructureLocatePersistence.VerifiedStart selectedStart = verified;
+            return NativeStructureLocateResults.selectAndReference(
+                    pos, irisLocated, () -> selectedSearch.search().reference(selectedStart),
+                    nativeLocated, nativeReference);
+        }
+        throw new IllegalStateException("Iris structure locate rejected too many selected candidates within "
+                + radius + " placement rings");
     }
 
     HolderSet<Structure> filterReachableNativeStructures(ServerLevel level, HolderSet<Structure> holders,
@@ -193,10 +241,14 @@ final class ModdedNativeStructureStage {
                         decision.preserveSourceY(),
                         decision.yBand(),
                         (x, z) -> current.getHeight(x, z, true) + current.getMinHeight());
-                StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
-                        start, structure, start.getReferences(), templateManager,
-                        NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain()));
+                StructureStart wrapped = NativeStructureReferenceEnvelope.wrapForPublication(
+                        start, structure, start.getReferences(),
+                        NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain()),
+                        structureId);
                 chunk.setStartForStructure(structure, wrapped);
+                if (!wrapped.isValid()) {
+                    continue;
+                }
             } catch (Throwable error) {
                 throw NativeStructureGenerationException.failure(
                         "vertical adjustment", structureId, chunkPos.x(), chunkPos.z(), error);
@@ -227,7 +279,6 @@ final class ModdedNativeStructureStage {
         Engine current = generator.engine();
         List<NativePlacementGroup> placementGroups = new ArrayList<>();
         List<StructureStart> heightmapStarts = new ArrayList<>();
-        List<StructureStart> nativeStarts = new ArrayList<>();
         List<NativeStructureVegetationClearer.VegetationTarget> vegetationTargets = new ArrayList<>();
         List<NativeStructureTerrainIntegrator.TerrainTarget> terrainTargets = new ArrayList<>();
         for (int step = 0; step < steps; step++) {
@@ -245,10 +296,11 @@ final class ModdedNativeStructureStage {
                     List<StructureStart> starts = structureManager.startsForStructure(sectionPos, structure);
                     List<NativePlacement> resolvedPlacements = new ArrayList<>(starts.size());
                     for (StructureStart start : starts) {
-                        NativeStructureStartPlan plan = NativeStructurePlacementPlanner.matchingPlan(
-                                current, structureId, start.getChunkPos().x(), start.getChunkPos().z());
-                        IrisNativeStructureDecision decision = plan == null
-                                ? sourceDecision : NativeStructurePlacementPlanner.decisionFor(plan);
+                        NativeStructureOwnershipRecord ownership =
+                                NativeStructureOwnershipRecovery.resolve(
+                                        current, world.getLevel(), structureId, structure, start);
+                        IrisNativeStructureDecision decision =
+                                ownership == null ? sourceDecision : ownership.restoredDecision();
                         if (!decision.generate()) {
                             continue;
                         }
@@ -258,9 +310,6 @@ final class ModdedNativeStructureStage {
                                 structureId, start,
                                 NativeStructureTerrainIntegrator.resolveNativeTerrain(
                                         start, decision.terrain())));
-                        if (plan == null || !plan.placement().isUnderground()) {
-                            nativeStarts.add(start);
-                        }
                         boolean clearEntireFootprint = NativeStructureVegetationClearer
                                 .shouldClearEntireVegetationFootprint(
                                         structure.step(), decision.clearVegetation());
@@ -289,15 +338,6 @@ final class ModdedNativeStructureStage {
                     "heightmap priming", nativeStructureBatchContext(placementGroups),
                     chunkPos.x(), chunkPos.z(), error);
         }
-        try {
-            NativeStructureSurfaceFitter.prepareSurfaceStructures(
-                    world, area, nativeStarts,
-                    (x, z) -> current.getHeight(x, z, true) + current.getMinHeight());
-        } catch (Throwable error) {
-            throw NativeStructureGenerationException.failure(
-                    "terrain integration", nativeStructureBatchContext(placementGroups),
-                    chunkPos.x(), chunkPos.z(), error);
-        }
         try {
             NativeStructureVegetationClearer.clearIntersectingVegetation(
                     world, chunk, area, vegetationTargets);
@@ -306,6 +346,15 @@ final class ModdedNativeStructureStage {
                     "vegetation cleanup", nativeStructureBatchContext(placementGroups),
                     chunkPos.x(), chunkPos.z(), error);
         }
+        try {
+            NativeStructureSurfaceFitter.prepareSurfaceStructures(
+                    world, area, terrainTargets,
+                    (x, z) -> current.getHeight(x, z, true) + current.getMinHeight());
+        } catch (Throwable error) {
+            throw NativeStructureGenerationException.failure(
+                    "terrain integration", nativeStructureBatchContext(placementGroups),
+                    chunkPos.x(), chunkPos.z(), error);
+        }
         try {
             NativeStructurePostProcessor.prepareTerrain(
                     world, area, terrainTargets, this::resolvePaletteBlock);
@@ -413,8 +462,8 @@ final class ModdedNativeStructureStage {
         ChunkPos chunkPos = chunk.getPos();
         int minX = chunkPos.getMinBlockX();
         int minZ = chunkPos.getMinBlockZ();
-        int minY = chunk.getMinY();
-        int maxY = minY + chunk.getHeight() - 1;
+        int minY = chunk.getMinY() + 1;
+        int maxY = chunk.getMinY() + chunk.getHeight() - 1;
         return new BoundingBox(minX, minY, minZ, minX + 15, maxY, minZ + 15);
     }
 
@@ -436,6 +485,10 @@ final class ModdedNativeStructureStage {
                                         List<NativePlacement> placements) {
     }
 
+    private record IrisNativeLocateSearch(Holder<Structure> holder, String structureId,
+                                          NativeStructureLocatePersistence.Search search) {
+    }
+
     private record StructureStepCache(Registry<Structure> registry, List<List<Structure>> structures) {
     }
 }

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedPackInstaller.java

@@ -56,8 +56,8 @@ public final class ModdedPackInstaller {
         synchronized (installLock) {
             File packs = configDir.resolve("irisworldgen").resolve("packs").toFile();
             try {
-                boolean installed = PackDownloader.isDefaultOverworld(pack)
-                        ? PackDownloader.downloadDefaultOverworld(packs, forceOverwrite, feedback) != null
+                PackDownloader.PackInstallResult result = PackDownloader.isDefaultOverworld(pack)
+                        ? PackDownloader.downloadDefaultOverworld(packs, forceOverwrite, feedback)
                         : PackDownloader.download(
                                 packs,
                                 "IrisDimensions/" + pack,
@@ -65,8 +65,9 @@ public final class ModdedPackInstaller {
                                 forceOverwrite,
                                 false,
                                 pack,
-                                feedback) != null;
-                if (installed) {
+                                feedback);
+                boolean installed = result != null;
+                if (result != null && result.changed()) {
                     // Pack-install completion is one of the four forced-datapack regeneration triggers; every
                     // install call site already runs off the server thread, so regenerate inline here. A
                     // regeneration failure must never turn a successful install into a failed one.
@@ -76,6 +77,9 @@ public final class ModdedPackInstaller {
                         LOGGER.error("Iris installed pack '{}' but could not regenerate the forced datapack", pack, regenerationFailure);
                     }
                 }
+                if (result != null && result.restartRequired()) {
+                    feedback.accept("Pack '" + pack + "' is installed on disk and requires a server restart before its active data changes.");
+                }
                 return installed;
             } catch (IOException error) {
                 LOGGER.error("Iris pack download failed for IrisDimensions/{} ({})", pack, branch, error);

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedRegistries.java

@@ -28,6 +28,7 @@ import art.arcane.iris.spi.PlatformEntityType;
 import art.arcane.iris.spi.PlatformItem;
 import art.arcane.iris.spi.PlatformRegistries;
 import art.arcane.volmlib.util.data.UnresolvedKeyLog;
+import net.minecraft.core.HolderLookup;
 import net.minecraft.core.Registry;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.core.registries.Registries;
@@ -40,6 +41,7 @@ import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.block.state.properties.Property;
+import net.minecraft.world.level.storage.loot.LootTable;
 
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
@@ -212,6 +214,20 @@ public final class ModdedRegistries implements PlatformRegistries {
         return keys;
     }
 
+    @Override
+    public List<String> lootTableKeys() {
+        List<String> keys = new ArrayList<>();
+        MinecraftServer instance = server.get();
+        if (instance == null) {
+            warnNotReady("loot table");
+            return keys;
+        }
+        HolderLookup.RegistryLookup<LootTable> registry = instance.reloadableRegistries().lookup()
+                .lookupOrThrow(Registries.LOOT_TABLE);
+        registry.listElementIds().forEach(key -> keys.add(key.identifier().toString()));
+        return keys;
+    }
+
     @Override
     public Map<String, List<PlatformBlockProperty>> blockStateProperties() {
         Map<String, List<PlatformBlockProperty>> properties = new LinkedHashMap<>();

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedStartup.java

@@ -19,6 +19,7 @@
 package art.arcane.iris.modded;
 
 import art.arcane.iris.core.pack.BrokenPackException;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.pack.PackDownloader;
 import art.arcane.iris.core.pack.PackValidationRegistry;
 import art.arcane.iris.core.pack.PackValidationResult;
@@ -104,9 +105,9 @@ public final class ModdedStartup {
 
     public static void validateAllPacks() {
         File packsRoot = ModdedPackCommands.packsRoot();
-        File[] packDirs = packsRoot.listFiles(File::isDirectory);
+        List<File> packDirs = PackDirectoryResolver.listVisiblePackDirectories(packsRoot);
         PackValidationRegistry.clear();
-        if (packDirs == null || packDirs.length == 0) {
+        if (packDirs.isEmpty()) {
             LOGGER.info("Iris found no packs to validate under {}; install one with /iris download <pack>",
                     packsRoot.getAbsolutePath());
             return;
@@ -146,8 +147,8 @@ public final class ModdedStartup {
         if (pack == null || pack.isBlank()) {
             throw new IllegalArgumentException("Pack name is required for world creation");
         }
-        File packDir = new File(ModdedPackCommands.packsRoot(), pack);
-        if (!packDir.isDirectory()) {
+        File packDir = PackDirectoryResolver.resolveExisting(ModdedPackCommands.packsRoot(), pack);
+        if (packDir == null) {
             throw new BrokenPackException(pack, List.of(
                     "Pack folder does not exist under " + ModdedPackCommands.packsRoot().getAbsolutePath() + "."));
         }

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedStructureHooks.java

@@ -19,8 +19,10 @@
 package art.arcane.iris.modded;
 
 import art.arcane.iris.nativegen.NativeStructureGenerationException;
+import art.arcane.iris.nativegen.NativeStructureFactory;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.PlatformStructureHooks;
+import art.arcane.iris.spi.PlatformStructureHooks.JigsawSourceMetadata;
 import art.arcane.iris.spi.PlatformWorld;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Holder;
@@ -95,6 +97,67 @@ public final class ModdedStructureHooks implements PlatformStructureHooks {
         return registryKeys(Registries.TEMPLATE_POOL);
     }
 
+    @Override
+    public JigsawSourceMetadata jigsawSourceMetadata(String structureKey) {
+        MinecraftServer instance = requireServer("resolve live jigsaw metadata for registered structure '"
+                + structureKey + "'");
+        try {
+            Identifier identifier = Identifier.tryParse(structureKey);
+            if (identifier == null) {
+                throw new IllegalArgumentException("Invalid registered structure key: " + structureKey);
+            }
+            Registry<Structure> registry = instance.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+            Structure structure = registry.getValue(identifier);
+            if (structure == null) {
+                throw new IllegalArgumentException("Registered structure does not exist: " + structureKey);
+            }
+            if (!(structure instanceof JigsawStructure jigsaw)) {
+                throw new IllegalArgumentException("Registered structure is not a jigsaw: " + structureKey);
+            }
+            return NativeStructureFactory.sourceMetadata(
+                    instance.registryAccess(), instance.getStructureManager(), jigsaw);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve live jigsaw metadata for registered structure '"
+                    + structureKey + "' from the modded structure registry", error);
+        }
+    }
+
+    @Override
+    public int templatePoolHorizontalSpan(String templatePoolKey) {
+        MinecraftServer instance = requireServer("resolve the live horizontal span for registered template pool '"
+                + templatePoolKey + "'");
+        try {
+            return NativeStructureFactory.templatePoolHorizontalSpan(
+                    instance.registryAccess(), instance.getStructureManager(), templatePoolKey);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve the live horizontal span for registered "
+                    + "template pool '" + templatePoolKey + "' from the modded template-pool registry", error);
+        }
+    }
+
+    @Override
+    public int jigsawStartPoolHorizontalSpan(String structureKey, String templatePoolKey) {
+        MinecraftServer instance = requireServer("resolve the effective start-pool span for registered jigsaw '"
+                + structureKey + "'");
+        try {
+            Identifier identifier = Identifier.tryParse(structureKey);
+            if (identifier == null) {
+                throw new IllegalArgumentException("Invalid registered structure key: " + structureKey);
+            }
+            Structure structure = instance.registryAccess().lookupOrThrow(Registries.STRUCTURE)
+                    .getValue(identifier);
+            if (!(structure instanceof JigsawStructure jigsaw)) {
+                throw new IllegalArgumentException("Registered structure is not a jigsaw: " + structureKey);
+            }
+            return NativeStructureFactory.jigsawStartPoolHorizontalSpan(
+                    instance.registryAccess(), instance.getStructureManager(), jigsaw, templatePoolKey);
+        } catch (RuntimeException error) {
+            throw new IllegalStateException("Iris failed to resolve the effective start-pool span for registered "
+                    + "jigsaw structure '" + structureKey + "' and pool '" + templatePoolKey
+                    + "' from the modded registries", error);
+        }
+    }
+
     @Override
     public List<String> structureSetKeys() {
         return registryKeys(Registries.STRUCTURE_SET);

adapters/modded-common/src/main/java/art/arcane/iris/modded/command/ModdedCommandSuggestions.java

@@ -18,6 +18,7 @@
 
 package art.arcane.iris.modded.command;
 
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.IrisStructureLocator;
 import art.arcane.iris.modded.IrisModdedChunkGenerator;
@@ -153,24 +154,18 @@ final class ModdedCommandSuggestions {
         names.add("overworld");
         try {
             File packs = ModdedEngineBootstrap.loader().configDir().resolve("irisworldgen").resolve("packs").toFile();
-            File[] children = packs.listFiles();
-            if (children != null) {
-                for (File child : children) {
-                    if (!child.isDirectory()) {
-                        continue;
-                    }
-                    String packName = child.getName();
-                    names.add(packName);
-                    File dimensions = new File(child, "dimensions");
-                    File[] dimensionFiles = dimensions.listFiles(
-                            (File directory, String name) -> name.endsWith(".json"));
-                    if (dimensionFiles == null) {
-                        continue;
-                    }
-                    for (File dimensionFile : dimensionFiles) {
-                        String fileName = dimensionFile.getName();
-                        names.add(packName + ":" + fileName.substring(0, fileName.length() - 5));
-                    }
+            for (File child : PackDirectoryResolver.listVisiblePackDirectories(packs)) {
+                String packName = child.getName();
+                names.add(packName);
+                File dimensions = new File(child, "dimensions");
+                File[] dimensionFiles = dimensions.listFiles(
+                        (File directory, String name) -> name.endsWith(".json"));
+                if (dimensionFiles == null) {
+                    continue;
+                }
+                for (File dimensionFile : dimensionFiles) {
+                    String fileName = dimensionFile.getName();
+                    names.add(packName + ":" + fileName.substring(0, fileName.length() - 5));
                 }
             }
         } catch (Throwable e) {

adapters/modded-common/src/main/java/art/arcane/iris/modded/command/ModdedDatapackCommands.java

@@ -20,6 +20,7 @@ package art.arcane.iris.modded.command;
 
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.nms.datapack.DataVersion;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.modded.IrisModdedChunkGenerator;
@@ -42,8 +43,12 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Locale;
+import java.util.Set;
 import java.util.function.Predicate;
 
 import art.arcane.iris.core.localization.IrisLanguage;
@@ -74,11 +79,11 @@ public final class ModdedDatapackCommands {
         root.then(Commands.literal("ls")
                 .executes((CommandContext<CommandSourceStack> context) -> list(context.getSource())));
 
-        root.then(message("ingest", "Modrinth datapack ingest requires the Bukkit plugin because its editable-resource import and manifest workflow use Bukkit tooling. Iris modded dimensions do run native vanilla and datapack structure placement; install the datapack in world/datapacks and restart to generate its registered structures."));
-        root.then(message("pull", "Modrinth datapack ingest requires the Bukkit plugin because its editable-resource import and manifest workflow use Bukkit tooling. Iris modded dimensions do run native vanilla and datapack structure placement; install the datapack in world/datapacks and restart to generate its registered structures."));
+        root.then(message("ingest", "Managed Modrinth datapack ingest is Bukkit-only. On modded servers install the datapack folder or zip in world/datapacks, enable it, restart, then use /iris datapack list to confirm it is enabled. Registered structures generate natively in Iris dimensions."));
+        root.then(message("pull", "Managed Modrinth datapack ingest is Bukkit-only. On modded servers install the datapack folder or zip in world/datapacks, enable it, restart, then use /iris datapack list to confirm it is enabled. Registered structures generate natively in Iris dimensions."));
 
-        root.then(message("remove", "Datapack removal manages the Bukkit ingest manifest. On modded servers delete the datapack folder from world/datapacks and restart."));
-        root.then(message("rm", "Datapack removal manages the Bukkit ingest manifest. On modded servers delete the datapack folder from world/datapacks and restart."));
+        root.then(message("remove", "Managed datapack removal is Bukkit-only. On modded servers disable the pack, delete its folder or zip from world/datapacks, and restart."));
+        root.then(message("rm", "Managed datapack removal is Bukkit-only. On modded servers disable the pack, delete its folder or zip from world/datapacks, and restart."));
 
         return root;
     }
@@ -215,27 +220,24 @@ public final class ModdedDatapackCommands {
         MinecraftServer server = source.getServer();
         LinkedHashSet<String> configured = new LinkedHashSet<>();
         File packsRoot = ModdedPackCommands.packsRoot();
-        File[] packs = packsRoot.isDirectory() ? packsRoot.listFiles(File::isDirectory) : null;
-        if (packs != null) {
-            for (File pack : packs) {
-                if (!new File(pack, "dimensions").isDirectory()) {
-                    continue;
-                }
-                try {
-                    IrisData data = IrisData.get(pack);
-                    for (IrisDimension dimension : data.getDimensionLoader().loadAll(data.getDimensionLoader().getPossibleKeys())) {
-                        if (dimension == null || dimension.getDatapackImports() == null) {
-                            continue;
-                        }
-                        for (String url : dimension.getDatapackImports()) {
-                            if (url != null && !url.isBlank()) {
-                                configured.add(url.trim());
-                            }
+        for (File pack : PackDirectoryResolver.listVisiblePackDirectories(packsRoot)) {
+            if (!new File(pack, "dimensions").isDirectory()) {
+                continue;
+            }
+            try {
+                IrisData data = IrisData.get(pack);
+                for (IrisDimension dimension : data.getDimensionLoader().loadAll(data.getDimensionLoader().getPossibleKeys())) {
+                    if (dimension == null || dimension.getDatapackImports() == null) {
+                        continue;
+                    }
+                    for (String url : dimension.getDatapackImports()) {
+                        if (url != null && !url.isBlank()) {
+                            configured.add(url.trim());
                         }
                     }
-                } catch (Throwable e) {
-                    LOGGER.error("Iris datapack import scan failed for pack {}", pack.getName(), e);
                 }
+            } catch (Throwable e) {
+                LOGGER.error("Iris datapack import scan failed for pack {}", pack.getName(), e);
             }
         }
 
@@ -248,19 +250,45 @@ public final class ModdedDatapackCommands {
         }
 
         File datapacks = worldDatapacksFolder(server);
-        File[] installed = datapacks.isDirectory() ? datapacks.listFiles(File::isDirectory) : null;
+        File[] installed = datapacks.isDirectory()
+                ? datapacks.listFiles(file -> file.isDirectory() || file.isFile() && file.getName().toLowerCase(Locale.ROOT).endsWith(".zip"))
+                : null;
+        Set<String> availableIds = new HashSet<>(server.getPackRepository().getAvailableIds());
+        Set<String> selectedIds = new HashSet<>(server.getPackRepository().getSelectedIds());
         KList<String> names = new KList<>();
         if (installed != null) {
-            for (File folder : installed) {
-                if (new File(folder, "pack.mcmeta").isFile()) {
-                    names.add(folder.getName());
+            for (File installedPack : installed) {
+                String name = installedPack.getName();
+                String repositoryId = resolveRepositoryId(name, availableIds);
+                String state;
+                if (repositoryId == null) {
+                    state = "unavailable";
+                } else if (selectedIds.contains(repositoryId)) {
+                    state = "enabled";
+                } else {
+                    state = "disabled";
                 }
+                names.add(name + " [" + state + "]");
             }
         }
+        Collections.sort(names);
         IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_DATAPACK_COMMANDS_INSTALLED_WORLD_DATAPACKS, MessageArgument.untrusted("value", names.size())));
         for (String name : names) {
             IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_DATAPACK_COMMANDS_MESSAGE_2, MessageArgument.untrusted("name", name)));
         }
         return 1;
     }
+
+    private static String resolveRepositoryId(String filename, Set<String> availableIds) {
+        String direct = "file/" + filename;
+        if (availableIds.contains(direct)) {
+            return direct;
+        }
+        for (String availableId : availableIds) {
+            if (availableId.equals(filename) || availableId.endsWith("/" + filename)) {
+                return availableId;
+            }
+        }
+        return null;
+    }
 }

adapters/modded-common/src/main/java/art/arcane/iris/modded/command/ModdedLocateCommands.java

@@ -173,10 +173,16 @@ final class ModdedLocateCommands {
             return 0;
         }
         if (decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS) {
-            locateIrisStructure(source, level, engine, player, target.key());
+            if (!IrisStructureLocator.hasNativePlacement(engine, target.key())) {
+                locateIrisStructure(source, level, engine, player, target.key());
+                return 1;
+            }
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.IRIS_MODDED_COMMANDS_SEARCHING_NATIVE_STRUCTURE_WITHIN_CHUNKS, MessageArgument.untrusted("value", target.key()), MessageArgument.untrusted("NATIVESTRUCTURELOCATERADIUS", NATIVE_STRUCTURE_LOCATE_RADIUS)));
+            runNativeStructureLocate(source, level, player, target);
             return 1;
         }
-        if (target.availability() != NativeStructureAvailability.AVAILABLE) {
+        if (!IrisStructureLocator.hasNativePlacement(engine, target.key())
+                && target.availability() != NativeStructureAvailability.AVAILABLE) {
             IrisModdedCommands.fail(source, nativeUnavailableMessage(target.key(), target.availability()));
             return 0;
         }

adapters/modded-common/src/main/java/art/arcane/iris/modded/command/ModdedPackCommands.java

@@ -110,14 +110,12 @@ public final class ModdedPackCommands {
 
         List<File> targets = new ArrayList<>();
         if (pack == null || pack.isBlank()) {
-            File[] dirs = packsRoot.listFiles(File::isDirectory);
-            if (dirs == null || dirs.length == 0) {
+            List<File> dirs = PackDirectoryResolver.listVisiblePackDirectories(packsRoot);
+            if (dirs.isEmpty()) {
                 IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_PACK_COMMANDS_NO_PACKS_VALIDATE_UNDER, MessageArgument.untrusted("value", packsRoot.getAbsolutePath())));
                 return 0;
             }
-            for (File dir : dirs) {
-                targets.add(dir);
-            }
+            targets.addAll(dirs);
         } else {
             File target = PackDirectoryResolver.resolveExisting(packsRoot, pack);
             if (target == null) {

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedGenerationLeaseContractTest.java

@@ -48,7 +48,8 @@ public class ModdedGenerationLeaseContractTest {
         String references = method(source, "public void createReferences(");
         assertTrue(references.contains("requireGenerationLease(current, \"modded_create_references\")"));
         assertTrue(references.contains("IrisContext.open(current, lease.sessionId(), null)"));
-        assertTrue(references.contains("super.createReferences(level, structureManager, chunk);"));
+        assertTrue(references.contains("NativeStructureReferenceRepair.createReferences("));
+        assertFalse(references.contains("super.createReferences(level, structureManager, chunk);"));
     }
 
     @Test

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedStructureHooksTest.java

@@ -80,6 +80,11 @@ public class ModdedStructureHooksTest {
                 IllegalStateException.class, hooks::jigsawStructureKeys);
         IllegalStateException templatePoolKeys = assertThrows(
                 IllegalStateException.class, hooks::templatePoolKeys);
+        IllegalStateException jigsawMetadata = assertThrows(
+                IllegalStateException.class, () -> hooks.jigsawSourceMetadata("minecraft:village"));
+        IllegalStateException templatePoolSpan = assertThrows(
+                IllegalStateException.class,
+                () -> hooks.templatePoolHorizontalSpan("minecraft:village/plains/town_centers"));
         IllegalStateException structureSetKeys = assertThrows(
                 IllegalStateException.class, hooks::structureSetKeys);
         IllegalStateException structureBiomeKeys = assertThrows(
@@ -88,6 +93,8 @@ public class ModdedStructureHooksTest {
         assertTrue(structureKeys.getMessage().contains("before the Minecraft server is available"));
         assertTrue(jigsawStructureKeys.getMessage().contains("before the Minecraft server is available"));
         assertTrue(templatePoolKeys.getMessage().contains("before the Minecraft server is available"));
+        assertTrue(jigsawMetadata.getMessage().contains("before the Minecraft server is available"));
+        assertTrue(templatePoolSpan.getMessage().contains("before the Minecraft server is available"));
         assertTrue(structureSetKeys.getMessage().contains("before the Minecraft server is available"));
         assertTrue(structureBiomeKeys.getMessage().contains("before the Minecraft server is available"));
     }

adapters/modded-common/src/test/java/art/arcane/iris/modded/NativeStructureFailureContractTest.java

@@ -56,7 +56,7 @@ public class NativeStructureFailureContractTest {
     }
 
     @Test
-    public void structureTerrainPreparationPrecedesVegetationAndPlacement() throws IOException {
+    public void structureVegetationCleanupPrecedesTerrainPreparationAndPlacement() throws IOException {
         String source = moddedSource("ModdedNativeStructureStage.java");
         int placementStart = source.indexOf("void placeVanillaStructures");
         int placementEnd = source.indexOf("private static String nativeStructureBatchContext", placementStart);
@@ -65,9 +65,9 @@ public class NativeStructureFailureContractTest {
         assertTrue(placement.contains("\"terrain integration\""));
         assertTrue(placement.contains("prepareSurfaceStructures"));
         assertTrue(placement.contains("clearIntersectingVegetation"));
-        assertTrue(placement.indexOf("prepareSurfaceStructures")
-                < placement.indexOf("clearIntersectingVegetation"));
         assertTrue(placement.indexOf("clearIntersectingVegetation")
+                < placement.indexOf("prepareSurfaceStructures"));
+        assertTrue(placement.indexOf("prepareSurfaceStructures")
                 < placement.indexOf("for (NativePlacementGroup group"));
     }
 
@@ -86,6 +86,7 @@ public class NativeStructureFailureContractTest {
                 < placement.indexOf("prepareSurfaceStructures"));
         assertTrue(source.contains("generationEngine.getHeight(x, z, false) + runtimeMinY + 1"));
         assertTrue(source.contains("generationEngine.getHeight(x, z, true) + runtimeMinY + 1"));
+        assertTrue(source.contains("int minY = chunk.getMinY() + 1;"));
     }
 
     @Test

adapters/modded-common/src/test/java/art/arcane/iris/modded/SchemaBuilderPlatformIsolationTest.java

@@ -0,0 +1,53 @@
+package art.arcane.iris.modded;
+
+import art.arcane.iris.core.project.SchemaBuilder;
+import art.arcane.iris.engine.object.IrisDirection;
+import art.arcane.iris.engine.object.annotations.ArrayType;
+import art.arcane.iris.engine.object.annotations.Desc;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.volmlib.util.json.JSONArray;
+import art.arcane.volmlib.util.json.JSONObject;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+public class SchemaBuilderPlatformIsolationTest {
+    @Test
+    public void enumSchemaDoesNotResolveBukkitOnlyMethodSignatures() {
+        assertThrows(ClassNotFoundException.class, () -> Class.forName("org.bukkit.block.BlockFace"));
+
+        JSONObject schema = new SchemaBuilder(DirectionModel.class, null).construct();
+        JSONObject direction = schema.getJSONObject("properties").getJSONObject("direction");
+        String definitionKey = direction.getString("$ref").substring("#/definitions/".length());
+        JSONArray values = schema.getJSONObject("definitions").getJSONObject(definitionKey).getJSONArray("oneOf");
+        List<String> names = new ArrayList<>(values.length());
+        for (int index = 0; index < values.length(); index++) {
+            names.add(values.getJSONObject(index).getString("const"));
+        }
+
+        assertEquals(List.of(
+                "UP_POSITIVE_Y",
+                "DOWN_NEGATIVE_Y",
+                "NORTH_NEGATIVE_Z",
+                "SOUTH_POSITIVE_Z",
+                "EAST_POSITIVE_X",
+                "WEST_NEGATIVE_X"), names);
+        assertEquals("#/definitions/" + definitionKey,
+                schema.getJSONObject("properties").getJSONObject("directions")
+                        .getJSONObject("items").getString("$ref"));
+    }
+
+    @Desc("Direction model.")
+    public static class DirectionModel {
+        @Desc("Direction.")
+        private IrisDirection direction = IrisDirection.NORTH_NEGATIVE_Z;
+
+        @Desc("Directions.")
+        @ArrayType(type = IrisDirection.class)
+        private KList<IrisDirection> directions = new KList<>();
+    }
+}

adapters/modded-common/src/test/java/art/arcane/iris/modded/command/IrisModdedStructureCommandTest.java

@@ -1,15 +1,49 @@
 package art.arcane.iris.modded.command;
 
+import art.arcane.iris.nativegen.NativeStructureLocateResults;
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.core.BlockPos;
 import org.junit.Test;
 
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.concurrent.atomic.AtomicInteger;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 
 public class IrisModdedStructureCommandTest {
+    @Test
+    public void mixedUnexploredLocateReferencesOnlyTheSelectedProvider() {
+        BlockPos origin = BlockPos.ZERO;
+        Pair<BlockPos, String> irisNear = Pair.of(new BlockPos(4, 70, 0), "iris");
+        Pair<BlockPos, String> nativeFar = Pair.of(new BlockPos(8, 70, 0), "native");
+        AtomicInteger irisReferences = new AtomicInteger();
+        AtomicInteger nativeReferences = new AtomicInteger();
+
+        Pair<BlockPos, String> irisSelected = NativeStructureLocateResults.selectAndReference(
+                origin,
+                irisNear, () -> irisReferences.incrementAndGet(),
+                nativeFar, () -> nativeReferences.incrementAndGet());
+
+        assertSame(irisNear, irisSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(0, nativeReferences.get());
+
+        Pair<BlockPos, String> nativeNear = Pair.of(new BlockPos(2, 70, 0), "native");
+        Pair<BlockPos, String> nativeSelected = NativeStructureLocateResults.selectAndReference(
+                origin,
+                irisNear, () -> irisReferences.incrementAndGet(),
+                nativeNear, () -> nativeReferences.incrementAndGet());
+
+        assertSame(nativeNear, nativeSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(1, nativeReferences.get());
+    }
+
     @Test
     public void gotoStructureSupportsIrisAndNativeRegistryTargets() throws IOException {
         String source = source("ModdedLocateCommands.java");
@@ -40,21 +74,34 @@ public class IrisModdedStructureCommandTest {
         int methodStart = source.indexOf("Pair<BlockPos, Holder<Structure>> findNearestIrisStructure(");
         int methodEnd = source.indexOf("HolderSet<Structure> filterReachableNativeStructures(", methodStart);
         String method = source.substring(methodStart, methodEnd);
-        int unexploredGuard = method.indexOf("if (findUnexplored)");
         int registryLookup = method.indexOf("level.registryAccess().lookupOrThrow(Registries.STRUCTURE)");
         int placedCheck = method.indexOf(
-                "if (!IrisStructureLocator.isPlaced(current, structureId))");
-        int irisLocate = method.indexOf("IrisStructureLocator.locate(", placedCheck);
+                "if (!IrisStructureLocator.hasNativePlacement(current, structureId))");
+        int irisLocate = method.indexOf("NativeStructureLocatePersistence.search(", placedCheck);
+        int nearestSelection = method.indexOf(
+                "NativeStructureLocateResults.nearest(pos, predicted, nativeLocated)", irisLocate);
+        int selectedVerification = method.indexOf("bestSearch.search().verify(bestResult)", nearestSelection);
+        int selectedReference = method.indexOf(
+                "selectedSearch.search().reference(selectedStart)", selectedVerification);
 
-        assertTrue(unexploredGuard >= 0);
-        assertTrue(registryLookup > unexploredGuard);
+        assertTrue(registryLookup >= 0);
         assertTrue(placedCheck > registryLookup);
         assertTrue(irisLocate > placedCheck);
+        assertTrue(nearestSelection > irisLocate);
+        assertTrue(selectedVerification > nearestSelection);
+        assertTrue(selectedReference > selectedVerification);
+        assertTrue(method.contains("NativeStructureLocatePersistence.probe("));
+        assertTrue(method.contains("findUnexplored"));
         assertTrue(method.contains("LocateStatus.SEARCH_LIMIT_REACHED"));
-        assertTrue(method.contains("new BlockPos(result.originX(), result.baseY(), result.originZ())"));
+        assertTrue(method.contains("verified.ownership().locatorY()"));
+        assertTrue(method.contains("selectedSearch.search().reference(selectedStart)"));
+        assertTrue(method.contains("NativeStructureLocateResults.selectAndReference("));
         assertFalse(method.contains("NativeStructureLocateCapability"));
         assertTrue(source.contains("structureBiomeSource.isStructureReachable(holder)"));
         assertFalse(source.contains("isPaperUnavailable"));
+        String generator = moddedSource("IrisModdedChunkGenerator.java");
+        assertTrue(generator.contains("NativeStructureVanillaLocator.predict("));
+        assertFalse(generator.contains("super.findNearestMapStructure(level, reachable"));
     }
 
     @Test
@@ -68,7 +115,7 @@ public class IrisModdedStructureCommandTest {
         int policyResolution = method.indexOf("NativeStructureGenerationPolicy.resolve(engine, target.key(), false)", genericIrisLookup);
         int replacementCheck = method.indexOf(
                 "decision.status() == NativeStructureGenerationStatus.REPLACED_BY_IRIS", policyResolution);
-        int replacementLocate = method.indexOf("locateIrisStructure(source, level, engine, player, target.key())",
+        int replacementLocate = method.indexOf("runNativeStructureLocate(source, level, player, target)",
                 replacementCheck);
 
         assertTrue(nativeResolution >= 0);
@@ -76,6 +123,8 @@ public class IrisModdedStructureCommandTest {
         assertTrue(policyResolution > genericIrisLookup);
         assertTrue(replacementCheck > policyResolution);
         assertTrue(replacementLocate > replacementCheck);
+        assertTrue(method.contains("!IrisStructureLocator.hasNativePlacement(engine, target.key())"));
+        assertTrue(method.contains("&& target.availability() != NativeStructureAvailability.AVAILABLE"));
     }
 
     @Test

adapters/modded-common/src/test/java/art/arcane/iris/nativegen/NativeStructureReferenceRepairTest.java

@@ -0,0 +1,442 @@
+package art.arcane.iris.nativegen;
+
+import art.arcane.iris.core.loader.IrisData;
+import art.arcane.iris.engine.IrisEngine;
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipBundle;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipRecord;
+import art.arcane.iris.engine.framework.NativeStructureOwnershipStore;
+import art.arcane.iris.engine.framework.NativeStructureStartPlan;
+import art.arcane.iris.engine.object.IrisDimension;
+import art.arcane.iris.engine.object.IrisNativeStructure;
+import art.arcane.iris.engine.object.IrisNativeStructureDecision;
+import art.arcane.iris.engine.object.IrisStructurePlacement;
+import art.arcane.iris.engine.object.IrisStructureTerrain;
+import art.arcane.iris.engine.object.IrisStructureTerrainMode;
+import art.arcane.iris.engine.object.NativeStructureGenerationStatus;
+import art.arcane.volmlib.util.collection.KList;
+import com.github.benmanes.caffeine.cache.Cache;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureReferenceRepairTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void persistedEnvelopeRepairsReloadedMonumentReferenceOutsideLiveBounds() {
+        long seed = 119723L;
+        ChunkPos origin = new ChunkPos(-3, 6);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                structure,
+                0,
+                terrain);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                "minecraft:monument",
+                wrapped,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()),
+                NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain));
+        PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                origin, seed, new PiecesContainer(wrapped.getPieces()));
+        StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
+        ChunkPos target = outsideLiveBounds(ownership, reloaded);
+
+        assertNotNull(target);
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, ownership));
+        assertFalse(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, null));
+    }
+
+    @Test
+    public void deniedNaturalStartsCannotEnterCollisionArbitration() {
+        IrisNativeStructureDecision enabled = new IrisNativeStructureDecision(
+                NativeStructureGenerationStatus.GENERATE_NATIVE,
+                0, null, false, false, null, new IrisStructureTerrain());
+        IrisNativeStructureDecision disabled = new IrisNativeStructureDecision(
+                NativeStructureGenerationStatus.DISABLED_BY_PACK,
+                0, null, false, false, null, new IrisStructureTerrain());
+        IrisNativeStructureDecision replaced = new IrisNativeStructureDecision(
+                NativeStructureGenerationStatus.REPLACED_BY_IRIS,
+                0, null, false, false, null, new IrisStructureTerrain());
+
+        assertTrue(NativeStructureReferenceRepair.naturalDecisionAllows(enabled));
+        assertFalse(NativeStructureReferenceRepair.naturalDecisionAllows(disabled));
+        assertFalse(NativeStructureReferenceRepair.naturalDecisionAllows(replaced));
+    }
+
+    @Test
+    public void persistedManualOwnershipSurvivesDisabledNaturalPolicyDuringReferenceScans()
+            throws Exception {
+        String structureKey = "minecraft:monument";
+        long seed = 582119L;
+        ChunkPos origin = new ChunkPos(2, -4);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart start = NativeStructureReferenceEnvelope.wrap(
+                generated, structure, 0, terrain);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
+                structureKey,
+                start,
+                plan(origin, NativeStructureReferenceEnvelope.contentBounds(start).minY()),
+                NativeStructureReferenceEnvelope.referenceBounds(start, structure, terrain));
+        IrisDimension dimension = new IrisDimension();
+        dimension.getImportedStructures().getDisabled().add(structureKey);
+        IrisData data = allocateWithoutConstructor(IrisData.class);
+        Engine engine = engine(dimension, data);
+        IrisNativeStructureDecision currentDecision = NativeStructureGenerationPolicy.resolve(
+                engine, structureKey, false);
+
+        assertFalse(currentDecision.generate());
+        assertFalse(NativeStructureReferenceRepair.naturalDecisionAllows(currentDecision));
+
+        ProtoChunk originChunk = emptyChunk(origin);
+        originChunk.setStartForStructure(structure, start);
+        ProtoChunk emptyScannedChunk = emptyChunk(new ChunkPos(Integer.MIN_VALUE, Integer.MIN_VALUE));
+        Registry<Structure> registry = structureRegistry(structure, structureKey);
+        ServerLevel serverLevel = allocateWithoutConstructor(ServerLevel.class);
+        StructureManager structureManager = new StructureManager(null, null, null);
+        ChunkPos coveredTarget = new ChunkPos(
+                ownership.referenceMinChunkX(), ownership.referenceMinChunkZ());
+        ChunkPos uncoveredTarget = outsideReferenceEnvelopeWithinScan(ownership);
+
+        assertNotNull(uncoveredTarget);
+
+        installOwnership(engine, ownership);
+        try {
+            WorldGenLevel level = worldGenLevel(
+                    registry, serverLevel, originChunk, emptyScannedChunk);
+            ProtoChunk coveredChunk = emptyChunk(coveredTarget);
+            NativeStructureReferenceRepair.createReferences(
+                    engine, level, structureManager, coveredChunk);
+
+            assertSame(start, originChunk.getStartForStructure(structure));
+            assertTrue(originChunk.getStartForStructure(structure).isValid());
+            assertTrue(coveredChunk.getReferencesForStructure(structure).contains(origin.pack()));
+
+            ProtoChunk uncoveredChunk = emptyChunk(uncoveredTarget);
+            NativeStructureReferenceRepair.createReferences(
+                    engine, level, structureManager, uncoveredChunk);
+
+            assertSame(start, originChunk.getStartForStructure(structure));
+            assertTrue(originChunk.getStartForStructure(structure).isValid());
+            assertFalse(uncoveredChunk.getReferencesForStructure(structure).contains(origin.pack()));
+        } finally {
+            NativeStructureOwnershipStore.close(engine);
+        }
+    }
+
+    private static StructureStart monumentStart(OceanMonumentStructure structure,
+                                                  ChunkPos origin, long seed) {
+        WorldgenRandom random = new WorldgenRandom(
+                new LegacyRandomSource(RandomSupport.generateUniqueSeed()));
+        random.setLargeFeatureSeed(seed, origin.x(), origin.z());
+        Direction orientation = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+        OceanMonumentPieces.MonumentBuilding building = new OceanMonumentPieces.MonumentBuilding(
+                random,
+                origin.getMinBlockX() - 29,
+                origin.getMinBlockZ() - 29,
+                orientation
+        );
+        return new StructureStart(
+                structure,
+                origin,
+                0,
+                new PiecesContainer(List.of(building))
+        );
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin, int baseY) {
+        IrisNativeStructure source = new IrisNativeStructure()
+                .setStructure("minecraft:monument")
+                .setWeight(1);
+        IrisStructurePlacement placement = new IrisStructurePlacement()
+                .setPlacementId("monument-reference-test")
+                .setNativeStructures(new KList<IrisNativeStructure>().qadd(source));
+        return new NativeStructureStartPlan(
+                placement,
+                source,
+                origin.x(),
+                origin.z(),
+                baseY
+        );
+    }
+
+    private static ChunkPos outsideLiveBounds(NativeStructureOwnershipRecord ownership,
+                                              StructureStart start) {
+        for (int chunkX = ownership.referenceMinChunkX();
+             chunkX <= ownership.referenceMaxChunkX(); chunkX++) {
+            for (int chunkZ = ownership.referenceMinChunkZ();
+                 chunkZ <= ownership.referenceMaxChunkZ(); chunkZ++) {
+                ChunkPos candidate = new ChunkPos(chunkX, chunkZ);
+                if (!start.getBoundingBox().intersects(
+                        candidate.getMinBlockX(), candidate.getMinBlockZ(),
+                        candidate.getMaxBlockX(), candidate.getMaxBlockZ())) {
+                    return candidate;
+                }
+            }
+        }
+        return null;
+    }
+
+    private static ChunkPos outsideReferenceEnvelopeWithinScan(
+            NativeStructureOwnershipRecord ownership) {
+        int originX = ownership.originChunkX();
+        int originZ = ownership.originChunkZ();
+        List<ChunkPos> candidates = List.of(
+                new ChunkPos(ownership.referenceMinChunkX() - 1, originZ),
+                new ChunkPos(ownership.referenceMaxChunkX() + 1, originZ),
+                new ChunkPos(originX, ownership.referenceMinChunkZ() - 1),
+                new ChunkPos(originX, ownership.referenceMaxChunkZ() + 1));
+        for (ChunkPos candidate : candidates) {
+            if (!ownership.covers(candidate.x(), candidate.z())
+                    && Math.abs(candidate.x() - originX)
+                    <= NativeStructureOwnershipRecord.MAX_REFERENCE_DISTANCE_CHUNKS
+                    && Math.abs(candidate.z() - originZ)
+                    <= NativeStructureOwnershipRecord.MAX_REFERENCE_DISTANCE_CHUNKS) {
+                return candidate;
+            }
+        }
+        return null;
+    }
+
+    private static ProtoChunk emptyChunk(ChunkPos position) {
+        return new ProtoChunk(
+                position,
+                UpgradeData.EMPTY,
+                LevelHeightAccessor.create(0, 0),
+                null,
+                null);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Registry<Structure> structureRegistry(
+            Structure structure, String structureKey) {
+        Identifier identifier = Identifier.parse(structureKey);
+        InvocationHandler handler = (Object proxy, Method method, Object[] arguments) -> {
+            if (method.getName().equals("getKey")) {
+                return arguments != null && arguments.length == 1
+                        && arguments[0] == structure ? identifier : null;
+            }
+            return defaultProxyValue(proxy, method, arguments);
+        };
+        return (Registry<Structure>) Proxy.newProxyInstance(
+                Registry.class.getClassLoader(),
+                new Class<?>[]{Registry.class},
+                handler);
+    }
+
+    private static WorldGenLevel worldGenLevel(
+            Registry<Structure> registry,
+            ServerLevel serverLevel,
+            ChunkAccess originChunk,
+            ChunkAccess emptyChunk) {
+        RegistryAccess registryAccess = registryAccess(registry);
+        ChunkPos origin = originChunk.getPos();
+        InvocationHandler handler = (Object proxy, Method method, Object[] arguments) -> {
+            return switch (method.getName()) {
+                case "registryAccess" -> registryAccess;
+                case "getLevel" -> serverLevel;
+                case "getChunk" -> arguments != null
+                        && arguments.length >= 2
+                        && ((Integer) arguments[0]) == origin.x()
+                        && ((Integer) arguments[1]) == origin.z()
+                        ? originChunk : emptyChunk;
+                default -> defaultProxyValue(proxy, method, arguments);
+            };
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(),
+                new Class<?>[]{WorldGenLevel.class},
+                handler);
+    }
+
+    private static RegistryAccess registryAccess(Registry<Structure> registry) {
+        InvocationHandler handler = (Object proxy, Method method, Object[] arguments) -> {
+            return switch (method.getName()) {
+                case "lookupOrThrow" -> registry;
+                case "lookup" -> Optional.of(registry);
+                case "registries" -> Stream.empty();
+                default -> defaultProxyValue(proxy, method, arguments);
+            };
+        };
+        return (RegistryAccess) Proxy.newProxyInstance(
+                RegistryAccess.class.getClassLoader(),
+                new Class<?>[]{RegistryAccess.class},
+                handler);
+    }
+
+    private static Engine engine(IrisDimension dimension, IrisData data) throws Exception {
+        TestEngine engine = allocateWithoutConstructor(TestEngine.class);
+        engine.dimension = dimension;
+        engine.data = data;
+        return engine;
+    }
+
+    @SuppressWarnings("unchecked")
+    private static void installOwnership(
+            Engine engine, NativeStructureOwnershipRecord ownership) throws Exception {
+        NativeStructureOwnershipBundle bundle =
+                NativeStructureOwnershipBundle.empty().with(ownership);
+        Class<?> storageType = Class.forName(
+                "art.arcane.iris.engine.framework.NativeStructureOwnershipStore$Storage");
+        InvocationHandler storageHandler =
+                (Object proxy, Method method, Object[] arguments) -> {
+                    return switch (method.getName()) {
+                        case "read" -> arguments != null
+                                && arguments.length == 2
+                                && ((Integer) arguments[0]) == ownership.originChunkX()
+                                && ((Integer) arguments[1]) == ownership.originChunkZ()
+                                ? bundle : null;
+                        case "write", "remove" -> null;
+                        default -> defaultProxyValue(proxy, method, arguments);
+                    };
+                };
+        Object storage = Proxy.newProxyInstance(
+                storageType.getClassLoader(),
+                new Class<?>[]{storageType},
+                storageHandler);
+        Class<?> stateType = Class.forName(
+                "art.arcane.iris.engine.framework.NativeStructureOwnershipStore$State");
+        Constructor<?> constructor = stateType.getDeclaredConstructor(Engine.class, storageType);
+        constructor.setAccessible(true);
+        Object state = constructor.newInstance(engine, storage);
+        Field statesField = NativeStructureOwnershipStore.class.getDeclaredField("STATES");
+        statesField.setAccessible(true);
+        Cache<Engine, Object> states = (Cache<Engine, Object>) statesField.get(null);
+        states.put(engine, state);
+    }
+
+    private static <T> T allocateWithoutConstructor(Class<T> type) throws Exception {
+        Class<?> unsafeType = Class.forName("sun.misc.Unsafe");
+        Field unsafeField = unsafeType.getDeclaredField("theUnsafe");
+        unsafeField.setAccessible(true);
+        Object unsafe = unsafeField.get(null);
+        Method allocateInstance = unsafeType.getMethod("allocateInstance", Class.class);
+        return type.cast(allocateInstance.invoke(unsafe, type));
+    }
+
+    private static Object defaultProxyValue(
+            Object proxy, Method method, Object[] arguments) {
+        return switch (method.getName()) {
+            case "equals" -> arguments != null && arguments.length == 1
+                    && proxy == arguments[0];
+            case "hashCode" -> System.identityHashCode(proxy);
+            case "toString" -> proxy.getClass().getInterfaces()[0].getSimpleName() + "Proxy";
+            default -> primitiveDefault(method.getReturnType());
+        };
+    }
+
+    private static Object primitiveDefault(Class<?> returnType) {
+        if (!returnType.isPrimitive() || returnType == void.class) {
+            return null;
+        }
+        if (returnType == boolean.class) {
+            return false;
+        }
+        if (returnType == char.class) {
+            return '\0';
+        }
+        if (returnType == byte.class) {
+            return (byte) 0;
+        }
+        if (returnType == short.class) {
+            return (short) 0;
+        }
+        if (returnType == int.class) {
+            return 0;
+        }
+        if (returnType == long.class) {
+            return 0L;
+        }
+        if (returnType == float.class) {
+            return 0.0F;
+        }
+        return 0.0D;
+    }
+
+    private static final class TestEngine extends IrisEngine {
+        private IrisDimension dimension;
+        private IrisData data;
+
+        private TestEngine() {
+            super(null, false);
+        }
+
+        @Override
+        public IrisDimension getDimension() {
+            return dimension;
+        }
+
+        @Override
+        public IrisData getData() {
+            return data;
+        }
+
+        @Override
+        public boolean isClosing() {
+            return false;
+        }
+
+        @Override
+        public boolean isClosed() {
+            return false;
+        }
+    }
+}

build.gradle

@@ -120,6 +120,8 @@ nmsBindings.each { key, value ->
                 rootProject.file("adapters/bukkit/nms/${key}/src/main/java/art/arcane/iris/core/nms/${key}/IrisChunkGenerator.java").absolutePath)
             systemProperty('iris.nativeStructurePostProcessorSource',
                 rootProject.file('adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructurePostProcessor.java').absolutePath)
+            systemProperty('iris.nativeStructureStartInjectorSource',
+                rootProject.file('adapters/minecraft-common/src/main/java/art/arcane/iris/nativegen/NativeStructureStartInjector.java').absolutePath)
             systemProperty('iris.customBiomeSource',
                 rootProject.file("adapters/bukkit/nms/${key}/src/main/java/art/arcane/iris/core/nms/${key}/CustomBiomeSource.java").absolutePath)
             systemProperty('iris.vanillaStructureBiomesSource',

core/build.gradle

@@ -119,6 +119,10 @@ dependencies {
     testRuntimeOnly(libs.paper.api)
 }
 
+tasks.named('test').configure {
+    maxHeapSize = '1g'
+}
+
 java {
     toolchain {
         languageVersion = JavaLanguageVersion.of(25)

core/purity-allowlist.txt

@@ -2,14 +2,18 @@ art/arcane/iris/core/IrisRuntimeSchedulerMode.java
 art/arcane/iris/core/IrisWorldStorage.java
 art/arcane/iris/core/IrisWorlds.java
 art/arcane/iris/core/ServerConfigurator.java
+art/arcane/iris/core/WorldCreatorCompat.java
+art/arcane/iris/core/WorldRemovalPathPolicy.java
 art/arcane/iris/core/datapack/DatapackIngestService.java
 art/arcane/iris/core/edit/BlockSignal.java
 art/arcane/iris/core/edit/DustRevealer.java
 art/arcane/iris/core/events/IrisEngineEvent.java
 art/arcane/iris/core/events/IrisEngineHotloadEvent.java
 art/arcane/iris/core/events/IrisLootEvent.java
+art/arcane/iris/core/lifecycle/BukkitWorldConfiguration.java
 art/arcane/iris/core/lifecycle/BukkitPublicBackend.java
 art/arcane/iris/core/lifecycle/CapabilitySnapshot.java
+art/arcane/iris/core/lifecycle/IrisWorldRemovalService.java
 art/arcane/iris/core/lifecycle/PaperLibBootstrap.java
 art/arcane/iris/core/lifecycle/PaperLikeRuntimeBackend.java
 art/arcane/iris/core/lifecycle/WorldLifecycleBackend.java
@@ -115,7 +119,6 @@ art/arcane/iris/engine/object/IrisVanillaLootTable.java
 art/arcane/iris/engine/object/LegacyTileData.java
 art/arcane/iris/engine/object/PotionEffectTypes.java
 art/arcane/iris/engine/object/TileData.java
-art/arcane/iris/engine/object/annotations/functions/LootTableKeyFunction.java
 art/arcane/iris/engine/platform/BukkitChunkGenerator.java
 art/arcane/iris/engine/platform/DummyBiomeProvider.java
 art/arcane/iris/engine/platform/DummyChunkGenerator.java

core/src/main/java/art/arcane/iris/core/DatapackInstallResult.java

@@ -0,0 +1,44 @@
+package art.arcane.iris.core;
+
+import java.util.Objects;
+
+public record DatapackInstallResult(Status status) {
+    public DatapackInstallResult {
+        Objects.requireNonNull(status, "status");
+    }
+
+    public static DatapackInstallResult failedResult() {
+        return new DatapackInstallResult(Status.FAILED);
+    }
+
+    public static DatapackInstallResult unchangedResult() {
+        return new DatapackInstallResult(Status.UNCHANGED);
+    }
+
+    public static DatapackInstallResult readyResult() {
+        return new DatapackInstallResult(Status.READY);
+    }
+
+    public static DatapackInstallResult restartRequiredResult() {
+        return new DatapackInstallResult(Status.RESTART_REQUIRED);
+    }
+
+    public boolean succeeded() {
+        return status != Status.FAILED;
+    }
+
+    public boolean changed() {
+        return status == Status.READY || status == Status.RESTART_REQUIRED;
+    }
+
+    public boolean restartRequired() {
+        return status == Status.RESTART_REQUIRED;
+    }
+
+    public enum Status {
+        FAILED,
+        UNCHANGED,
+        READY,
+        RESTART_REQUIRED
+    }
+}

core/src/main/java/art/arcane/iris/core/IrisDatapackCompiler.java

@@ -3,6 +3,8 @@ package art.arcane.iris.core;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.loader.ResourceLoader;
 import art.arcane.iris.core.nms.datapack.IDataFixer;
+import art.arcane.iris.core.pack.AtomicDirectoryPublisher;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.volmlib.util.collection.KList;
@@ -10,8 +12,12 @@ import art.arcane.volmlib.util.collection.KSet;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
+import java.nio.file.LinkOption;
 import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Comparator;
@@ -19,6 +25,7 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicIntegerArray;
 import java.util.stream.Stream;
 
@@ -49,9 +56,7 @@ public final class IrisDatapackCompiler {
             throw new IOException("No Iris datapack output roots were provided");
         }
 
-        for (File datapackRoot : datapackRoots) {
-            Files.createDirectories(datapackRoot.toPath());
-        }
+        resetOutputRoots(datapackRoots);
         IrisDimension.clearGeneratedBiomeTags(datapackRoots);
 
         DimensionHeight height = new DimensionHeight(fixer);
@@ -59,6 +64,7 @@ public final class IrisDatapackCompiler {
         int packCount = 0;
         int dimensionCount = 0;
         for (File packRoot : packRoots) {
+            PackDirectoryResolver.requireSafePackTree(packRoot);
             if (!hasDimensions(packRoot.toPath())) {
                 continue;
             }
@@ -93,42 +99,42 @@ public final class IrisDatapackCompiler {
         }
 
         IrisDimension.writeShared(datapackRoots, height, packFormat, adjustVanillaHeight);
-        validateOutputs(datapackRoots);
+        validateOutputs(datapackRoots, dimensionCount);
         return new CompilationResult(packCount, dimensionCount, countBiomes(biomes));
     }
 
     private static void collectInstalledPackRoots(Path packsRoot, Map<Path, File> roots) throws IOException {
-        if (!Files.isDirectory(packsRoot)) {
-            return;
-        }
-        try (Stream<Path> stream = Files.list(packsRoot)) {
-            List<Path> candidates = stream
-                    .filter(Files::isDirectory)
-                    .sorted(Comparator.comparing(Path::toString))
-                    .toList();
-            for (Path candidate : candidates) {
-                addPackRoot(candidate, roots);
-            }
+        List<File> candidates = PackDirectoryResolver.listVisiblePackDirectoriesOrThrow(packsRoot.toFile());
+        for (File candidate : candidates) {
+            addPackRoot(candidate.toPath(), roots);
         }
     }
 
     private static void collectWorldPackRoots(Path dimensionsRoot, Map<Path, File> roots) throws IOException {
-        if (!Files.isDirectory(dimensionsRoot)) {
+        if (Files.isSymbolicLink(dimensionsRoot)
+                || !Files.isDirectory(dimensionsRoot, LinkOption.NOFOLLOW_LINKS)) {
             return;
         }
-        try (Stream<Path> stream = Files.find(
-                dimensionsRoot,
-                WORLD_PACK_SCAN_DEPTH,
-                (path, attributes) -> attributes.isDirectory()
-                        && "pack".equals(path.getFileName().toString())
-                        && path.getParent() != null
-                        && "iris".equals(path.getParent().getFileName().toString())
-                        && hasDimensions(path)
-        )) {
-            List<Path> candidates = stream.sorted(Comparator.comparing(Path::toString)).toList();
-            for (Path candidate : candidates) {
-                addPackRoot(candidate, roots);
+        List<Path> candidates = new ArrayList<>();
+        Files.walkFileTree(dimensionsRoot, Set.of(), WORLD_PACK_SCAN_DEPTH, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult preVisitDirectory(Path directory, BasicFileAttributes attributes) {
+                if (!directory.equals(dimensionsRoot)
+                        && PackDirectoryResolver.containsHiddenPathSegment(dimensionsRoot, directory)) {
+                    return FileVisitResult.SKIP_SUBTREE;
+                }
+                if ("pack".equals(directory.getFileName().toString())
+                        && directory.getParent() != null
+                        && "iris".equals(directory.getParent().getFileName().toString())
+                        && hasDimensions(directory)) {
+                    candidates.add(directory);
+                }
+                return FileVisitResult.CONTINUE;
             }
+        });
+        candidates.sort(Comparator.comparing(Path::toString));
+        for (Path candidate : candidates) {
+            addPackRoot(candidate, roots);
         }
     }
 
@@ -137,29 +143,52 @@ public final class IrisDatapackCompiler {
             return;
         }
         Path normalized = root.toAbsolutePath().normalize();
+        if (!Files.isDirectory(normalized)) {
+            return;
+        }
+        PackDirectoryResolver.requireSafePackTree(normalized.toFile());
         Path identity = normalized.toRealPath();
         roots.putIfAbsent(identity, normalized.toFile());
     }
 
     private static boolean hasDimensions(Path root) {
         Path dimensions = root.resolve("dimensions");
-        if (!Files.isDirectory(dimensions)) {
+        if (Files.isSymbolicLink(dimensions)
+                || !Files.isDirectory(dimensions, LinkOption.NOFOLLOW_LINKS)) {
             return false;
         }
         try (Stream<Path> stream = Files.list(dimensions)) {
-            return stream.anyMatch(path -> Files.isRegularFile(path) && path.getFileName().toString().endsWith(".json"));
+            return stream.anyMatch(path -> !Files.isSymbolicLink(path)
+                    && Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS)
+                    && path.getFileName().toString().endsWith(".json"));
         } catch (IOException e) {
             return false;
         }
     }
 
-    private static void validateOutputs(Collection<File> datapackRoots) throws IOException {
+    private static void resetOutputRoots(Collection<File> datapackRoots) throws IOException {
+        for (File datapackRoot : datapackRoots) {
+            Path root = datapackRoot.toPath().toAbsolutePath().normalize();
+            if (Files.isSymbolicLink(root)) {
+                throw new IOException("Iris datapack output root is a symbolic link: " + root);
+            }
+            if (Files.exists(root, LinkOption.NOFOLLOW_LINKS)) {
+                if (!Files.isDirectory(root, LinkOption.NOFOLLOW_LINKS)) {
+                    throw new IOException("Iris datapack output root is not a directory: " + root);
+                }
+                AtomicDirectoryPublisher.deleteTree(root);
+            }
+            Files.createDirectories(root);
+        }
+    }
+
+    private static void validateOutputs(Collection<File> datapackRoots, int dimensionCount) throws IOException {
         for (File datapackRoot : datapackRoots) {
             Path root = datapackRoot.toPath();
             if (!Files.isRegularFile(root.resolve("pack.mcmeta"))) {
                 throw new IOException("Iris datapack metadata was not generated at " + root);
             }
-            if (!Files.isDirectory(root.resolve("data/iris/dimension_type"))) {
+            if (dimensionCount > 0 && !Files.isDirectory(root.resolve("data/iris/dimension_type"))) {
                 throw new IOException("Iris dimension types were not generated at " + root);
             }
         }

core/src/main/java/art/arcane/iris/core/IrisWorldStorage.java

@@ -11,6 +11,7 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Path;
+import java.nio.file.Files;
 import java.util.Locale;
 import java.util.Objects;
 import java.util.Optional;
@@ -50,6 +51,10 @@ public final class IrisWorldStorage {
         return cached;
     }
 
+    public static String configuredLevelName() {
+        return levelNameFromProperties(new File("server.properties"));
+    }
+
     static String levelNameFromProperties(File serverProperties) {
         Properties properties = new Properties();
         if (Objects.requireNonNull(serverProperties, "serverProperties").isFile()) {
@@ -87,6 +92,39 @@ public final class IrisWorldStorage {
         return keyFromName(worldName, levelRoot().getName());
     }
 
+    public static NamespacedKey managedKeyFromName(String worldName) {
+        String requestedName = Objects.requireNonNull(worldName, "worldName").trim();
+        if (requestedName.contains(":")) {
+            return managedKeyFromName(requestedName, DEFAULT_LEVEL_NAME);
+        }
+        return managedKeyFromName(requestedName, levelRoot().getName());
+    }
+
+    public static NamespacedKey managedKeyFromName(String worldName, String levelName) {
+        String requestedName = Objects.requireNonNull(worldName, "worldName").trim();
+        if (requestedName.isEmpty()) {
+            throw new IllegalArgumentException("World name cannot be empty.");
+        }
+        if (requestedName.contains("/") || requestedName.contains("\\") || requestedName.contains("..")) {
+            throw new IllegalArgumentException("World name must be a safe single path segment.");
+        }
+
+        NamespacedKey key;
+        if (requestedName.contains(":")) {
+            key = NamespacedKey.fromString(requestedName.toLowerCase(Locale.ENGLISH));
+            if (key == null) {
+                throw new IllegalArgumentException("World identifier is invalid: " + requestedName);
+            }
+        } else {
+            key = keyFromName(requestedName, levelName);
+        }
+
+        if (!IRIS_NAMESPACE.equals(key.getNamespace()) || !key.getKey().matches("[a-z0-9_-]+")) {
+            throw new IllegalArgumentException("Only Iris-managed dimension worlds can be changed.");
+        }
+        return key;
+    }
+
     static NamespacedKey keyFromName(String worldName, String levelName) {
         String name = Objects.requireNonNull(worldName, "worldName").trim();
         String mainLevelName = Objects.requireNonNull(levelName, "levelName").trim();
@@ -112,7 +150,11 @@ public final class IrisWorldStorage {
     }
 
     public static String logicalName(NamespacedKey key) {
-        return logicalName(key, levelRoot().getName());
+        NamespacedKey worldKey = Objects.requireNonNull(key, "key");
+        if (IRIS_NAMESPACE.equals(worldKey.getNamespace())) {
+            return worldKey.getKey();
+        }
+        return logicalName(worldKey, levelRoot().getName());
     }
 
     static String logicalName(NamespacedKey key, String levelName) {
@@ -147,6 +189,31 @@ public final class IrisWorldStorage {
         return dimensionRoot(levelRoot(), key);
     }
 
+    public static File requireSafeManagedDimensionRoot(NamespacedKey key) {
+        return requireSafeManagedDimensionRoot(levelRoot(), key);
+    }
+
+    public static File requireSafeManagedDimensionRoot(File levelRoot, NamespacedKey key) {
+        NamespacedKey worldKey = Objects.requireNonNull(key, "key");
+        if (!IRIS_NAMESPACE.equals(worldKey.getNamespace()) || !worldKey.getKey().matches("[a-z0-9_-]+")) {
+            throw new IllegalArgumentException("Only safe Iris-managed dimension worlds can be changed.");
+        }
+
+        Path root = Objects.requireNonNull(levelRoot, "levelRoot").toPath().toAbsolutePath().normalize();
+        Path dimensions = root.resolve("dimensions");
+        Path namespace = dimensions.resolve(IRIS_NAMESPACE);
+        Path target = namespace.resolve(worldKey.getKey()).normalize();
+        if (!Objects.equals(target.getParent(), namespace)) {
+            throw new IllegalArgumentException("World target escapes the Iris namespace root.");
+        }
+        for (Path path : new Path[]{dimensions, namespace, target}) {
+            if (Files.isSymbolicLink(path)) {
+                throw new IllegalArgumentException("World storage path contains a symbolic link: " + path);
+            }
+        }
+        return target.toFile();
+    }
+
     public static File dimensionRoot(File levelRoot, NamespacedKey key) {
         Path dimensionsRoot = Objects.requireNonNull(levelRoot, "levelRoot")
                 .toPath()

core/src/main/java/art/arcane/iris/core/IrisWorlds.java

@@ -22,8 +22,15 @@ import org.bukkit.configuration.file.YamlConfiguration;
 
 import java.io.File;
 import java.io.IOException;
-import java.io.OutputStreamWriter;
+import java.io.UncheckedIOException;
 import java.lang.reflect.Type;
+import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
 import java.util.Objects;
 import java.util.stream.Stream;
 
@@ -62,9 +69,42 @@ public class IrisWorlds {
         });
     }
 
-    public void put(String identity, String type) {
-        put0(identity, type);
-        save();
+    public synchronized void put(String identity, String type) {
+        String canonicalIdentity = WorldIdentity.parse(identity).toString();
+        String requiredType = Objects.requireNonNull(type, "type");
+        String previous = worlds.put(canonicalIdentity, requiredType);
+        if (requiredType.equals(previous)) {
+            return;
+        }
+        dirty = true;
+        try {
+            saveOrThrow();
+        } catch (IOException e) {
+            if (previous == null) {
+                worlds.remove(canonicalIdentity);
+            } else {
+                worlds.put(canonicalIdentity, previous);
+            }
+            dirty = true;
+            throw new UncheckedIOException("Failed to persist Iris world registry entry for " + canonicalIdentity, e);
+        }
+    }
+
+    public synchronized boolean remove(String identity) {
+        String canonicalIdentity = WorldIdentity.parse(identity).toString();
+        String previous = worlds.remove(canonicalIdentity);
+        if (previous == null) {
+            return false;
+        }
+        dirty = true;
+        try {
+            saveOrThrow();
+            return true;
+        } catch (IOException e) {
+            worlds.put(canonicalIdentity, previous);
+            dirty = true;
+            throw new UncheckedIOException("Failed to remove Iris world registry entry for " + canonicalIdentity, e);
+        }
     }
 
     private void put0(String identity, String type) {
@@ -74,7 +114,7 @@ public class IrisWorlds {
             dirty = true;
     }
 
-    public KMap<String, String> getWorlds() {
+    public synchronized KMap<String, String> getWorlds() {
         clean();
         KMap<String, String> result = new KMap<>();
         readBukkitWorlds().forEach((name, type) -> result.put(IrisWorldStorage.keyFromName(name).toString(), type));
@@ -95,7 +135,7 @@ public class IrisWorlds {
                 .filter(Objects::nonNull);
     }
 
-    public void clean() {
+    public synchronized void clean() {
         boolean removed = worlds.entrySet().removeIf(entry -> {
             try {
                 File packRoot = IrisWorldStorage.packRoot(WorldIdentity.parse(entry.getKey()));
@@ -108,18 +148,43 @@ public class IrisWorlds {
     }
 
     public synchronized void save() {
-        clean();
-        if (!dirty) return;
         try {
-            IO.write(IrisPlatforms.get().dataFile("worlds.json"), OutputStreamWriter::new, writer -> GSON.toJson(worlds, TYPE, writer));
-            dirty = false;
+            saveOrThrow();
         } catch (IOException e) {
             IrisLogging.error("Failed to save worlds.json!");
-            e.printStackTrace();
             IrisLogging.reportError(e);
         }
     }
 
+    private void saveOrThrow() throws IOException {
+        clean();
+        if (!dirty) {
+            return;
+        }
+
+        Path target = IrisPlatforms.get().dataFile("worlds.json").toPath().toAbsolutePath().normalize();
+        Path parent = target.getParent();
+        if (parent == null) {
+            throw new IOException("worlds.json target has no parent: " + target);
+        }
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".iris-worlds-", ".json");
+        try {
+            Files.writeString(staged, GSON.toJson(worlds, TYPE), StandardCharsets.UTF_8);
+            try (FileChannel channel = FileChannel.open(staged, StandardOpenOption.WRITE)) {
+                channel.force(true);
+            }
+            try {
+                Files.move(staged, target, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(staged, target, StandardCopyOption.REPLACE_EXISTING);
+            }
+            dirty = false;
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
     public static Long readBukkitWorldSeed(String world) {
         YamlConfiguration bukkit = YamlConfiguration.loadConfiguration(ServerProperties.BUKKIT_YML);
         ConfigurationSection worlds = bukkit.getConfigurationSection("worlds");

core/src/main/java/art/arcane/iris/core/ServerConfigurator.java

@@ -22,10 +22,14 @@ import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.core.datapack.DatapackIngestService;
 import art.arcane.iris.core.loader.IrisData;
+import art.arcane.iris.core.loader.ResourceLoader;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
 import art.arcane.iris.core.nms.INMS;
 import art.arcane.iris.core.nms.datapack.DataVersion;
 import art.arcane.iris.core.nms.datapack.IDataFixer;
+import art.arcane.iris.core.pack.AtomicDirectoryPublisher;
 import art.arcane.iris.core.pack.DefaultPackBootstrapProvisioner;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.engine.object.IrisBiome;
 import art.arcane.iris.engine.object.IrisBiomeCustom;
@@ -47,16 +51,27 @@ import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
+import java.nio.channels.FileChannel;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
+import java.nio.file.LinkOption;
 import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
+import java.util.Comparator;
+import java.util.HexFormat;
 import java.util.List;
 import java.util.Objects;
+import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
@@ -64,6 +79,8 @@ import art.arcane.iris.core.localization.BukkitRuntimeMessages;
 import art.arcane.iris.core.localization.IrisLanguage;
 import art.arcane.volmlib.util.localization.MessageArgument;
 public class ServerConfigurator {
+    private static final Object DATAPACK_INSTALL_LOCK = new Object();
+
     public static void configure() {
         IrisSettings.IrisSettingsAutoconfiguration s = IrisSettings.get().getAutoConfiguration();
         if (s.isConfigureSpigotTimeoutTime()) {
@@ -77,7 +94,10 @@ public class ServerConfigurator {
         if (DefaultPackBootstrapProvisioner.wasProvisionedThisStartup()) {
             IrisLogging.info("Paper loaded the Iris datapack during bootstrap; skipping the legacy startup install.");
         } else {
-            installDataPacks(true);
+            DatapackInstallResult result = installDataPacks(true);
+            if (result.restartRequired() && IrisSettings.get().getAutoConfiguration().isAutoRestartOnCustomBiomeInstall()) {
+                restart();
+            }
         }
     }
 
@@ -124,20 +144,20 @@ public class ServerConfigurator {
         return roots;
     }
 
-    public static boolean installDataPacks(boolean fullInstall) {
-        IDataFixer fixer = DataVersion.getDefault();
-        if (fixer == null) {
-            DataVersion fallback = DataVersion.getLatest();
-            IrisLogging.warn("Primary datapack fixer was null, forcing latest fixer: " + fallback.getVersion());
-            fixer = fallback.get();
-        }
-        return installDataPacks(fixer, fullInstall);
+    public static DatapackInstallResult installDataPacks(boolean fullInstall) {
+        return installDataPacks(resolveDataFixer(), fullInstall);
     }
 
-    public static boolean installDataPacks(IDataFixer fixer, boolean fullInstall) {
+    public static DatapackInstallResult installDataPacks(IDataFixer fixer, boolean fullInstall) {
+        synchronized (DATAPACK_INSTALL_LOCK) {
+            return installDataPacksLocked(fixer, fullInstall);
+        }
+    }
+
+    private static DatapackInstallResult installDataPacksLocked(IDataFixer fixer, boolean fullInstall) {
         if (fixer == null) {
             IrisLogging.error("Unable to install datapacks, fixer is null!");
-            return false;
+            return DatapackInstallResult.failedResult();
         }
         if (fullInstall) {
             IrisLogging.info("Checking Data Packs...");
@@ -145,7 +165,10 @@ public class ServerConfigurator {
             IrisLogging.debug("Checking Data Packs...");
         }
         KList<File> datapacksFolders = getDatapacksFolder();
-        DatapackIngestService.reapplyFromStaging(datapacksFolders);
+        if (!DatapackIngestService.reapplyFromStaging(datapacksFolders)) {
+            IrisLogging.error("Unable to compile Iris datapacks while external datapack recovery is incomplete.");
+            return DatapackInstallResult.failedResult();
+        }
         List<File> packRoots;
         try (Stream<IrisData> stream = allPacks()) {
             packRoots = stream
@@ -155,17 +178,58 @@ public class ServerConfigurator {
                     .toList();
         }
 
+        KList<File> liveRoots = getIrisDatapackRoots();
+        KList<File> stagedRoots = new KList<>();
+        List<Path> stagedPaths = new ArrayList<>(liveRoots.size());
+        List<AtomicDirectoryPublisher.Publication> publications = new ArrayList<>(liveRoots.size());
         try {
+            for (File liveRoot : liveRoots) {
+                Path target = liveRoot.toPath().toAbsolutePath().normalize();
+                Path parent = target.getParent();
+                if (parent == null) {
+                    throw new IOException("Iris datapack root has no parent: " + target);
+                }
+                Files.createDirectories(parent);
+                Path staged = parent.resolve(".iris-compile-" + UUID.randomUUID());
+                Files.createDirectories(staged);
+                stagedPaths.add(staged);
+                stagedRoots.add(staged.toFile());
+            }
             IrisDatapackCompiler.compile(
                     packRoots,
-                    getIrisDatapackRoots(),
+                    stagedRoots,
                     fixer,
                     BukkitPlatform.dataPackFormat(),
                     IrisSettings.get().getGeneral().adjustVanillaHeight
             );
-        } catch (IOException e) {
+            for (int i = 0; i < liveRoots.size(); i++) {
+                publications.add(AtomicDirectoryPublisher.publish(
+                        stagedRoots.get(i).toPath(),
+                        liveRoots.get(i).toPath()
+                ));
+            }
+            for (AtomicDirectoryPublisher.Publication publication : publications) {
+                publication.commit();
+                try {
+                    publication.cleanupBackup();
+                } catch (IOException cleanupFailure) {
+                    IrisLogging.warn("Iris datapack was committed but its backup could not be removed: "
+                            + cleanupFailure.getMessage());
+                }
+            }
+        } catch (IOException | RuntimeException e) {
+            closePublications(publications, e);
             IrisLogging.reportError("Unable to compile Iris datapacks", e);
-            return false;
+            return DatapackInstallResult.failedResult();
+        } finally {
+            for (Path stagedPath : stagedPaths) {
+                try {
+                    AtomicDirectoryPublisher.deleteTree(stagedPath);
+                } catch (IOException cleanupFailure) {
+                    IrisLogging.warn("Failed to clean Iris datapack compilation stage " + stagedPath + ": "
+                            + cleanupFailure.getMessage());
+                }
+            }
         }
         if (fullInstall) {
             IrisLogging.info("Data Packs Setup!");
@@ -173,74 +237,205 @@ public class ServerConfigurator {
             IrisLogging.debug("Data Packs Setup!");
         }
 
-        return fullInstall && verifyDataPacksPost(IrisSettings.get().getAutoConfiguration().isAutoRestartOnCustomBiomeInstall());
+        boolean restartRequired = fullInstall && verifyDataPacksPost();
+        return restartRequired
+                ? DatapackInstallResult.restartRequiredResult()
+                : DatapackInstallResult.readyResult();
     }
 
-    public static boolean installDataPacksIfChanged(boolean fullInstall) {
-        File packsDir = IrisPlatforms.get().dataFolder("packs");
-        String current = computePackFingerprint(packsDir);
-        File cacheFile = new File(IrisPlatforms.get().dataFolder("cache"), "datapack-fingerprint");
-        String cached = "";
-        if (cacheFile.exists()) {
+    private static IDataFixer resolveDataFixer() {
+        IDataFixer fixer = DataVersion.getDefault();
+        if (fixer != null) {
+            return fixer;
+        }
+        DataVersion fallback = DataVersion.getLatest();
+        IrisLogging.warn("Primary datapack fixer was null, forcing latest fixer: " + fallback.getVersion());
+        return fallback.get();
+    }
+
+    private static void closePublications(List<AtomicDirectoryPublisher.Publication> publications, Throwable failure) {
+        for (int i = publications.size() - 1; i >= 0; i--) {
             try {
-                cached = Files.readString(cacheFile.toPath(), StandardCharsets.UTF_8).trim();
-            } catch (IOException e) {
-                cached = "";
+                publications.get(i).close();
+            } catch (IOException rollbackFailure) {
+                failure.addSuppressed(rollbackFailure);
             }
         }
-        if (!current.isEmpty() && current.equals(cached)) {
-            IrisLogging.debug("Data packs unchanged, skipping install.");
-            return false;
+    }
+
+    public static DatapackInstallResult installDataPacksIfChanged(boolean fullInstall) {
+        synchronized (DATAPACK_INSTALL_LOCK) {
+            File packsDir = IrisPlatforms.get().dataFolder("packs");
+            String current;
+            try {
+                current = computePackFingerprint(packsDir);
+            } catch (RuntimeException exception) {
+                IrisLogging.reportError("Unable to fingerprint Iris packs safely", exception);
+                return DatapackInstallResult.failedResult();
+            }
+            File cacheFile = new File(IrisPlatforms.get().dataFolder("cache"), "datapack-fingerprint");
+            String cached = "";
+            if (cacheFile.exists()) {
+                try {
+                    cached = Files.readString(cacheFile.toPath(), StandardCharsets.UTF_8).trim();
+                } catch (IOException e) {
+                    cached = "";
+                }
+            }
+            if (!current.isEmpty() && current.equals(cached)) {
+                IrisLogging.debug("Data packs unchanged, skipping install.");
+                return DatapackInstallResult.unchangedResult();
+            }
+            DatapackInstallResult result = installDataPacksLocked(resolveDataFixer(), fullInstall);
+            if (result.succeeded()) {
+                try {
+                    writeFingerprintAtomic(cacheFile.toPath(), current);
+                } catch (IOException e) {
+                    IrisLogging.warn("Failed to write datapack fingerprint cache: " + e.getMessage());
+                }
+            }
+            return result;
         }
-        boolean result = installDataPacks(fullInstall);
-        try {
-            cacheFile.getParentFile().mkdirs();
-            Files.writeString(cacheFile.toPath(), current, StandardCharsets.UTF_8);
-        } catch (IOException e) {
-            IrisLogging.warn("Failed to write datapack fingerprint cache: " + e.getMessage());
-        }
-        return result;
     }
 
     public static String computePackFingerprint(File packsDir) {
-        if (packsDir == null || !packsDir.isDirectory()) {
+        if (packsDir == null) {
+            return "";
+        }
+        Path root = packsDir.toPath().toAbsolutePath().normalize();
+        if (Files.isSymbolicLink(root)) {
+            throw new IllegalArgumentException("Iris packs root is a symbolic link: " + root);
+        }
+        if (!Files.isDirectory(root, LinkOption.NOFOLLOW_LINKS)) {
             return "";
         }
         try {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
-            List<String> entries = new ArrayList<>();
-            collectFingerprintEntries(packsDir, packsDir.getAbsolutePath(), entries);
-            Collections.sort(entries);
-            for (String entry : entries) {
-                digest.update(entry.getBytes(StandardCharsets.UTF_8));
+            List<FingerprintEntry> entries = collectFingerprintEntries(root);
+            entries.sort(Comparator.comparing(FingerprintEntry::relativePath));
+            byte[] buffer = new byte[8192];
+            for (FingerprintEntry entry : entries) {
+                byte[] relativePath = entry.relativePath().getBytes(StandardCharsets.UTF_8);
+                updateDigestInt(digest, relativePath.length);
+                digest.update(relativePath);
+                updateDigestLong(digest, Files.size(entry.source()));
+                try (InputStream input = Files.newInputStream(entry.source())) {
+                    int read;
+                    while ((read = input.read(buffer)) >= 0) {
+                        if (read > 0) {
+                            digest.update(buffer, 0, read);
+                        }
+                    }
+                }
             }
-            byte[] hash = digest.digest();
-            StringBuilder sb = new StringBuilder(hash.length * 2);
-            for (byte b : hash) {
-                sb.append(String.format("%02x", b));
-            }
-            return sb.toString();
+            return HexFormat.of().formatHex(digest.digest());
+        } catch (IOException exception) {
+            throw new UncheckedIOException("Unable to fingerprint Iris packs at " + root, exception);
         } catch (NoSuchAlgorithmException e) {
             throw new IllegalStateException("SHA-256 not available", e);
         }
     }
 
-    private static void collectFingerprintEntries(File dir, String rootPath, List<String> entries) {
-        File[] files = dir.listFiles();
-        if (files == null) {
-            return;
+    private static void writeFingerprintAtomic(Path target, String fingerprint) throws IOException {
+        Path absoluteTarget = target.toAbsolutePath().normalize();
+        Path parent = absoluteTarget.getParent();
+        if (parent == null) {
+            throw new IOException("Datapack fingerprint target has no parent: " + absoluteTarget);
         }
-        for (File file : files) {
-            if (file.isDirectory()) {
-                if (file.getName().startsWith(".")) {
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".datapack-fingerprint-", ".tmp");
+        try {
+            Files.writeString(staged, fingerprint, StandardCharsets.UTF_8);
+            try (FileChannel channel = FileChannel.open(staged, StandardOpenOption.WRITE)) {
+                channel.force(true);
+            }
+            try {
+                Files.move(staged, absoluteTarget, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(staged, absoluteTarget, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    private static List<FingerprintEntry> collectFingerprintEntries(Path root) throws IOException {
+        List<FingerprintEntry> entries = new ArrayList<>();
+        try (Stream<Path> children = Files.list(root)) {
+            for (Path child : children.toList()) {
+                String childName = child.getFileName().toString();
+                if (PackDirectoryResolver.isHiddenName(childName)) {
                     continue;
                 }
-                collectFingerprintEntries(file, rootPath, entries);
-            } else {
-                String relative = file.getAbsolutePath().substring(rootPath.length());
-                entries.add(relative + "|" + file.length() + "|" + file.lastModified());
+                if (Files.isSymbolicLink(child)) {
+                    if (!Files.isDirectory(child)) {
+                        throw new IOException("Iris pack fingerprint rejected symbolic link: " + child);
+                    }
+                    PackDirectoryResolver.requireSafePackTree(child.toFile());
+                    collectFingerprintTree(child.toRealPath(), childName, entries);
+                } else if (Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS)) {
+                    collectFingerprintTree(child, childName, entries);
+                } else if (Files.isRegularFile(child, LinkOption.NOFOLLOW_LINKS)) {
+                    entries.add(new FingerprintEntry(child, childName));
+                } else {
+                    throw new IOException("Iris pack fingerprint rejected unsupported entry: " + child);
+                }
             }
         }
+        return entries;
+    }
+
+    private static void collectFingerprintTree(
+            Path treeRoot,
+            String logicalRoot,
+            List<FingerprintEntry> entries
+    ) throws IOException {
+        Files.walkFileTree(treeRoot, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult preVisitDirectory(Path directory, BasicFileAttributes attributes) {
+                if (!directory.equals(treeRoot)
+                        && PackDirectoryResolver.isHiddenName(directory.getFileName().toString())) {
+                    return FileVisitResult.SKIP_SUBTREE;
+                }
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attributes) throws IOException {
+                if (PackDirectoryResolver.isHiddenName(file.getFileName().toString())) {
+                    return FileVisitResult.CONTINUE;
+                }
+                if (attributes.isSymbolicLink() || Files.isSymbolicLink(file)) {
+                    throw new IOException("Iris pack fingerprint rejected symbolic link: " + file);
+                }
+                if (!attributes.isRegularFile()) {
+                    throw new IOException("Iris pack fingerprint rejected unsupported entry: " + file);
+                }
+                String relative = treeRoot.relativize(file).toString().replace(File.separatorChar, '/');
+                entries.add(new FingerprintEntry(file, logicalRoot + "/" + relative));
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult visitFileFailed(Path file, IOException failure) throws IOException {
+                throw new IOException("Unable to inspect Iris pack entry: " + file, failure);
+            }
+        });
+    }
+
+    private record FingerprintEntry(Path source, String relativePath) {
+    }
+
+    private static void updateDigestInt(MessageDigest digest, int value) {
+        for (int shift = Integer.SIZE - Byte.SIZE; shift >= 0; shift -= Byte.SIZE) {
+            digest.update((byte) (value >>> shift));
+        }
+    }
+
+    private static void updateDigestLong(MessageDigest digest, long value) {
+        for (int shift = Long.SIZE - Byte.SIZE; shift >= 0; shift -= Byte.SIZE) {
+            digest.update((byte) (value >>> shift));
+        }
     }
 
     public static File resolveDatapacksFolder(File worldFolder) {
@@ -255,12 +450,12 @@ public class ServerConfigurator {
         return IrisWorldStorage.levelRoot(worldFolder);
     }
 
-    private static boolean verifyDataPacksPost(boolean allowRestarting) {
+    private static boolean verifyDataPacksPost() {
         try (Stream<IrisData> stream = allPacks()) {
             boolean bad = stream
                     .map(data -> {
                         IrisLogging.debug("Checking Pack: " + data.getDataFolder().getPath());
-                        var loader = data.getDimensionLoader();
+                        ResourceLoader<IrisDimension> loader = data.getDimensionLoader();
                         return loader.loadAll(loader.getPossibleKeys())
                                 .stream()
                                 .filter(Objects::nonNull)
@@ -270,13 +465,13 @@ public class ServerConfigurator {
                     })
                     .toList()
                     .contains(true);
-            if (!bad) return false;
+            if (!bad) {
+                return false;
+            }
         }
 
 
-        if (allowRestarting) {
-            restart();
-        } else if (INMS.get().supportsDataPacks()) {
+        if (INMS.get().supportsDataPacks()) {
             IrisLogging.error("============================================================================");
             IrisLogging.error(C.ITALIC + "You need to restart your server to properly generate custom biomes.");
             IrisLogging.error(C.ITALIC + "By continuing, Iris will use backup biomes in place of the custom biomes.");
@@ -292,22 +487,23 @@ public class ServerConfigurator {
                 }
             }
 
-            J.sleep(3000);
         }
         return true;
     }
 
     public static void restart() {
-        J.s(() -> {
-            IrisLogging.warn("New data pack entries have been installed in Iris! Restarting server!");
-            IrisLogging.warn("This will only happen when your pack changes (updates/first time setup)");
-            IrisLogging.warn("(You can disable this auto restart in iris settings)");
+        restart("New data pack entries have been installed in Iris.");
+    }
+
+    public static void restart(String reason) {
+        LifecycleOperationCoordinator.get().quiesceForRestart(() -> J.s(() -> {
+            IrisLogging.warn(reason + " Restarting server to restore a safe lifecycle boundary.");
             J.s(() -> {
                 IrisLogging.warn("Looks like the restart command didn't work. Stopping the server instead!");
                 Bukkit.shutdown();
             }, 100);
             Bukkit.dispatchCommand(Bukkit.getConsoleSender(), "restart");
-        });
+        }));
     }
 
     public static boolean verifyDataPackInstalled(IrisDimension dimension) {
@@ -360,12 +556,12 @@ public class ServerConfigurator {
     }
 
     public static Stream<IrisData> allPacks() {
-        File[] packs = IrisPlatforms.get().dataFolder("packs").listFiles(File::isDirectory);
-        Stream<File> locals = packs == null ? Stream.empty() : Arrays.stream(packs);
+        Stream<File> locals = PackDirectoryResolver.listVisiblePackDirectories(
+                IrisPlatforms.get().dataFolder("packs")
+        ).stream();
         return Stream.concat(locals
-                .filter(base -> !base.getName().contains(".importing-"))
-                .filter( base -> {
-                    var content = new File(base, "dimensions").listFiles();
+                .filter(base -> {
+                    File[] content = new File(base, "dimensions").listFiles();
                     return content != null && content.length > 0;
                 })
                 .map(IrisData::get), IrisWorlds.get().getPacks());

core/src/main/java/art/arcane/iris/core/WorldRemovalPathPolicy.java

@@ -0,0 +1,169 @@
+package art.arcane.iris.core;
+
+import org.bukkit.NamespacedKey;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collection;
+import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
+
+public final class WorldRemovalPathPolicy {
+    private WorldRemovalPathPolicy() {
+    }
+
+    public static Target resolve(String identifier, String configuredMainWorld, Path levelRoot) {
+        return resolve(identifier, configuredMainWorld, List.of(configuredMainWorld), levelRoot);
+    }
+
+    public static Target resolve(
+            String identifier,
+            String currentMainWorld,
+            Collection<String> protectedWorldNames,
+            Path levelRoot
+    ) {
+        String requestedIdentifier = requireIdentifier(identifier);
+        String mainWorld = requireIdentifier(currentMainWorld);
+        for (String protectedWorldName : Objects.requireNonNull(protectedWorldNames, "protectedWorldNames")) {
+            if (protectedWorldName != null
+                    && !protectedWorldName.isBlank()
+                    && requestedIdentifier.equalsIgnoreCase(protectedWorldName.trim())) {
+                throw new Rejection(RejectionReason.CONFIGURED_MAIN_WORLD,
+                        "A current or configured main world cannot be removed.");
+            }
+        }
+        if (requestedIdentifier.toLowerCase(Locale.ENGLISH).startsWith(NamespacedKey.MINECRAFT + ":")) {
+            throw new Rejection(RejectionReason.MINECRAFT_NAMESPACE,
+                    "Minecraft namespace worlds cannot be removed.");
+        }
+
+        NamespacedKey worldKey;
+        try {
+            worldKey = IrisWorldStorage.managedKeyFromName(requestedIdentifier, mainWorld);
+        } catch (IllegalArgumentException failure) {
+            throw classifyIdentifierFailure(requestedIdentifier, failure);
+        }
+
+        Path normalizedLevelRoot = Objects.requireNonNull(levelRoot, "levelRoot").toAbsolutePath().normalize();
+        if (Files.isSymbolicLink(normalizedLevelRoot)) {
+            throw new Rejection(RejectionReason.SYMBOLIC_LINK,
+                    "World storage path contains a symbolic link: " + normalizedLevelRoot);
+        }
+        Path target;
+        try {
+            target = IrisWorldStorage.requireSafeManagedDimensionRoot(
+                    normalizedLevelRoot.toFile(),
+                    worldKey
+            ).toPath().toAbsolutePath().normalize();
+        } catch (IllegalArgumentException failure) {
+            throw classifyStorageFailure(normalizedLevelRoot, worldKey, failure);
+        }
+        validateStoragePath(normalizedLevelRoot, worldKey, target);
+        return new Target(
+                requestedIdentifier,
+                worldKey,
+                IrisWorldStorage.logicalName(worldKey, mainWorld),
+                normalizedLevelRoot,
+                target
+        );
+    }
+
+    public static void validateStoragePath(Path levelRoot, NamespacedKey worldKey, Path candidate) {
+        Path normalizedLevelRoot = Objects.requireNonNull(levelRoot, "levelRoot").toAbsolutePath().normalize();
+        if (Files.isSymbolicLink(normalizedLevelRoot)) {
+            throw new Rejection(RejectionReason.SYMBOLIC_LINK,
+                    "World storage path contains a symbolic link: " + normalizedLevelRoot);
+        }
+        Path expected;
+        try {
+            expected = IrisWorldStorage.requireSafeManagedDimensionRoot(
+                    normalizedLevelRoot.toFile(),
+                    Objects.requireNonNull(worldKey, "worldKey")
+            ).toPath().toAbsolutePath().normalize();
+        } catch (IllegalArgumentException failure) {
+            throw classifyStorageFailure(normalizedLevelRoot, worldKey, failure);
+        }
+        Path normalizedCandidate = Objects.requireNonNull(candidate, "candidate").toAbsolutePath().normalize();
+        if (!normalizedCandidate.equals(expected)) {
+            throw new Rejection(RejectionReason.OUTSIDE_STORAGE_ROOT,
+                    "The world directory is outside its exact Iris dimension storage root.");
+        }
+    }
+
+    private static Rejection classifyIdentifierFailure(String identifier, IllegalArgumentException failure) {
+        NamespacedKey parsed = identifier.contains(":")
+                ? NamespacedKey.fromString(identifier.toLowerCase(Locale.ENGLISH))
+                : null;
+        RejectionReason reason = parsed != null && !"iris".equals(parsed.getNamespace())
+                ? RejectionReason.NOT_IRIS_NAMESPACE
+                : RejectionReason.INVALID_IDENTIFIER;
+        return new Rejection(reason, failure.getMessage(), failure);
+    }
+
+    private static Rejection classifyStorageFailure(
+            Path levelRoot,
+            NamespacedKey worldKey,
+            IllegalArgumentException failure
+    ) {
+        Path dimensions = levelRoot.resolve("dimensions");
+        Path namespace = dimensions.resolve(worldKey.getNamespace());
+        Path target = namespace.resolve(worldKey.getKey());
+        RejectionReason reason = Files.isSymbolicLink(dimensions)
+                || Files.isSymbolicLink(namespace)
+                || Files.isSymbolicLink(target)
+                ? RejectionReason.SYMBOLIC_LINK
+                : RejectionReason.OUTSIDE_STORAGE_ROOT;
+        return new Rejection(reason, failure.getMessage(), failure);
+    }
+
+    private static String requireIdentifier(String identifier) {
+        if (identifier == null || identifier.isBlank()) {
+            throw new Rejection(RejectionReason.INVALID_IDENTIFIER, "The world identifier cannot be empty.");
+        }
+        return identifier.trim();
+    }
+
+    public record Target(
+            String requestedIdentifier,
+            NamespacedKey worldKey,
+            String logicalName,
+            Path levelRoot,
+            Path worldDirectory
+    ) {
+        public Target {
+            Objects.requireNonNull(requestedIdentifier, "requestedIdentifier");
+            Objects.requireNonNull(worldKey, "worldKey");
+            Objects.requireNonNull(logicalName, "logicalName");
+            Objects.requireNonNull(levelRoot, "levelRoot");
+            Objects.requireNonNull(worldDirectory, "worldDirectory");
+        }
+    }
+
+    public enum RejectionReason {
+        INVALID_IDENTIFIER,
+        CONFIGURED_MAIN_WORLD,
+        MINECRAFT_NAMESPACE,
+        NOT_IRIS_NAMESPACE,
+        OUTSIDE_STORAGE_ROOT,
+        SYMBOLIC_LINK
+    }
+
+    public static final class Rejection extends IllegalArgumentException {
+        private final RejectionReason reason;
+
+        private Rejection(RejectionReason reason, String message) {
+            super(message);
+            this.reason = Objects.requireNonNull(reason, "reason");
+        }
+
+        private Rejection(RejectionReason reason, String message, Throwable cause) {
+            super(message, cause);
+            this.reason = Objects.requireNonNull(reason, "reason");
+        }
+
+        public RejectionReason reason() {
+            return reason;
+        }
+    }
+}

core/src/main/java/art/arcane/iris/core/datapack/ModrinthResolver.java

@@ -23,14 +23,17 @@ import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
 
-import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.Reader;
 import java.net.HttpURLConnection;
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
@@ -39,6 +42,7 @@ public final class ModrinthResolver {
     private static final String API = "https://api.modrinth.com/v2";
     private static final String USER_AGENT = "VolmitSoftware/Iris (datapack-ingest)";
     private static final String DATAPACK_LOADER = "datapack";
+    private static final int MAX_API_RESPONSE_CHARS = 8 * 1024 * 1024;
 
     private ModrinthResolver() {
     }
@@ -63,9 +67,19 @@ public final class ModrinthResolver {
                 ? selectLatestDatapackVersion(versions, serverMcVersion)
                 : selectVersionByToken(versions, ref.versionToken);
         if (version == null) {
-            String detail = ref.versionToken == null ? "no datapack-loader version" : "no version matching '" + ref.versionToken + "'";
+            String detail = ref.versionToken == null
+                    ? (serverMcVersion == null || serverMcVersion.isBlank()
+                    ? "no datapack-loader version"
+                    : "no datapack-loader version compatible with Minecraft " + serverMcVersion)
+                    : "no version matching '" + ref.versionToken + "'";
             throw new IOException("Modrinth project '" + ref.slug + "' has " + detail);
         }
+        if (!isDatapack(version)) {
+            throw new IOException("Modrinth version for '" + ref.slug + "' is not published for the datapack loader");
+        }
+        if (serverMcVersion != null && !serverMcVersion.isBlank() && !gameVersionsContains(version, serverMcVersion)) {
+            throw new IOException("Modrinth version for '" + ref.slug + "' is not compatible with Minecraft " + serverMcVersion);
+        }
 
         JsonObject file = selectFile(version);
         if (file == null) {
@@ -76,41 +90,30 @@ public final class ModrinthResolver {
     }
 
     private static ModrinthRef parse(String url) {
-        if (!url.toLowerCase(Locale.ROOT).contains("modrinth.com/")) {
+        URI uri;
+        try {
+            uri = new URI(url);
+        } catch (URISyntaxException e) {
+            return null;
+        }
+        String host = uri.getHost();
+        if (host == null || !(host.equalsIgnoreCase("modrinth.com") || host.equalsIgnoreCase("www.modrinth.com"))) {
             return null;
         }
 
-        String path = url.replaceFirst("^[a-zA-Z][a-zA-Z0-9+.-]*://", "");
-        int query = path.indexOf('?');
-        if (query >= 0) {
-            path = path.substring(0, query);
-        }
-        int fragment = path.indexOf('#');
-        if (fragment >= 0) {
-            path = path.substring(0, fragment);
-        }
-
         List<String> parts = new ArrayList<>();
-        for (String segment : path.split("/")) {
+        for (String segment : uri.getPath().split("/")) {
             if (!segment.isBlank()) {
                 parts.add(segment);
             }
         }
-
-        int base = -1;
-        for (int i = 0; i < parts.size(); i++) {
-            if (parts.get(i).equalsIgnoreCase("modrinth.com")) {
-                base = i;
-                break;
-            }
-        }
-        if (base < 0 || parts.size() < base + 3) {
+        if (parts.size() < 2) {
             return null;
         }
 
-        String slug = parts.get(base + 2);
+        String slug = parts.get(1);
         String token = null;
-        for (int i = base + 3; i + 1 < parts.size(); i++) {
+        for (int i = 2; i + 1 < parts.size(); i++) {
             if (parts.get(i).equalsIgnoreCase("version")) {
                 token = parts.get(i + 1);
                 break;
@@ -125,6 +128,9 @@ public final class ModrinthResolver {
         String normalizedToken = normalizeVersion(token);
 
         for (JsonElement element : versions) {
+            if (!element.isJsonObject()) {
+                continue;
+            }
             JsonObject version = element.getAsJsonObject();
             String id = optString(version, "id");
             String number = optString(version, "version_number");
@@ -146,25 +152,24 @@ public final class ModrinthResolver {
         return datapackMatch != null ? datapackMatch : anyMatch;
     }
 
-    private static JsonObject selectLatestDatapackVersion(JsonArray versions, String serverMcVersion) {
-        JsonObject firstDatapack = null;
+    static JsonObject selectLatestDatapackVersion(JsonArray versions, String serverMcVersion) {
         for (JsonElement element : versions) {
+            if (!element.isJsonObject()) {
+                continue;
+            }
             JsonObject version = element.getAsJsonObject();
             if (!isDatapack(version)) {
                 continue;
             }
-            if (firstDatapack == null) {
-                firstDatapack = version;
-            }
-            if (serverMcVersion != null && !serverMcVersion.isBlank() && gameVersionsContains(version, serverMcVersion)) {
+            if (serverMcVersion == null || serverMcVersion.isBlank() || gameVersionsContains(version, serverMcVersion)) {
                 return version;
             }
         }
-        return firstDatapack;
+        return null;
     }
 
-    private static JsonObject selectFile(JsonObject version) {
-        JsonArray files = version.getAsJsonArray("files");
+    static JsonObject selectFile(JsonObject version) {
+        JsonArray files = optArray(version, "files");
         if (files == null || files.isEmpty()) {
             return null;
         }
@@ -174,11 +179,14 @@ public final class ModrinthResolver {
         JsonObject primary = null;
         JsonObject first = null;
         for (JsonElement element : files) {
+            if (!element.isJsonObject()) {
+                continue;
+            }
             JsonObject file = element.getAsJsonObject();
             if (first == null) {
                 first = file;
             }
-            boolean isPrimary = file.has("primary") && file.get("primary").getAsBoolean();
+            boolean isPrimary = optBoolean(file, "primary");
             boolean isZip = optString(file, "filename").toLowerCase(Locale.ROOT).endsWith(".zip");
             if (isPrimary && primary == null) {
                 primary = file;
@@ -203,14 +211,20 @@ public final class ModrinthResolver {
         return first;
     }
 
-    private static ResolvedDatapack toResolved(JsonObject version, JsonObject file, String slug) {
+    private static ResolvedDatapack toResolved(JsonObject version, JsonObject file, String slug) throws IOException {
         String downloadUrl = optString(file, "url");
         String filename = optString(file, "filename");
+        if (downloadUrl.isBlank() || filename.isBlank()) {
+            throw new IOException("Modrinth version for '" + slug + "' has an invalid downloadable file");
+        }
         String sha1 = null;
         if (file.has("hashes") && file.get("hashes").isJsonObject()) {
             sha1 = optString(file.getAsJsonObject("hashes"), "sha1");
+            if (!sha1.isBlank() && !sha1.matches("(?i)[0-9a-f]{40}")) {
+                throw new IOException("Modrinth version for '" + slug + "' has an invalid SHA-1 checksum");
+            }
         }
-        return new ResolvedDatapack(downloadUrl, filename, sha1, optString(version, "id"), optString(version, "version_number"), slug);
+        return new ResolvedDatapack(downloadUrl, filename, sha1, optString(version, "id"), optString(version, "version_number"), slug, false);
     }
 
     private static ResolvedDatapack directResolve(String url) {
@@ -226,16 +240,45 @@ public final class ModrinthResolver {
         if (filename.isBlank()) {
             filename = "datapack.zip";
         }
-        return new ResolvedDatapack(url, filename, null, "direct", "direct", null);
+        String identity = directIdentity(url);
+        return new ResolvedDatapack(url, filename, null, "direct-" + identity, "direct", null, true);
+    }
+
+    static String directIdentity(String url) {
+        String normalized = url;
+        try {
+            URI parsed = new URI(url).normalize();
+            normalized = new URI(
+                    parsed.getScheme() == null ? null : parsed.getScheme().toLowerCase(Locale.ROOT),
+                    parsed.getUserInfo(),
+                    parsed.getHost() == null ? null : parsed.getHost().toLowerCase(Locale.ROOT),
+                    parsed.getPort(),
+                    parsed.getPath(),
+                    parsed.getQuery(),
+                    null
+            ).toASCIIString();
+        } catch (URISyntaxException ignored) {
+        }
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            byte[] hash = digest.digest(normalized.getBytes(StandardCharsets.UTF_8));
+            StringBuilder builder = new StringBuilder(16);
+            for (int i = 0; i < 8; i++) {
+                builder.append(String.format("%02x", hash[i]));
+            }
+            return builder.toString();
+        } catch (NoSuchAlgorithmException e) {
+            throw new IllegalStateException("SHA-256 algorithm unavailable", e);
+        }
     }
 
     private static boolean isDatapack(JsonObject version) {
-        JsonArray loaders = version.getAsJsonArray("loaders");
+        JsonArray loaders = optArray(version, "loaders");
         if (loaders == null) {
             return false;
         }
         for (JsonElement loader : loaders) {
-            if (DATAPACK_LOADER.equalsIgnoreCase(loader.getAsString())) {
+            if (isString(loader) && DATAPACK_LOADER.equalsIgnoreCase(loader.getAsString())) {
                 return true;
             }
         }
@@ -243,12 +286,12 @@ public final class ModrinthResolver {
     }
 
     private static boolean gameVersionsContains(JsonObject version, String mc) {
-        JsonArray gameVersions = version.getAsJsonArray("game_versions");
+        JsonArray gameVersions = optArray(version, "game_versions");
         if (gameVersions == null) {
             return false;
         }
         for (JsonElement gv : gameVersions) {
-            if (mc.equalsIgnoreCase(gv.getAsString())) {
+            if (isString(gv) && mc.equalsIgnoreCase(gv.getAsString())) {
                 return true;
             }
         }
@@ -267,19 +310,42 @@ public final class ModrinthResolver {
     }
 
     private static String optString(JsonObject object, String key) {
-        if (object == null || !object.has(key) || object.get(key).isJsonNull()) {
+        if (object == null || !object.has(key) || !isString(object.get(key))) {
             return "";
         }
         return object.get(key).getAsString();
     }
 
+    private static JsonArray optArray(JsonObject object, String key) {
+        if (object == null || !object.has(key) || !object.get(key).isJsonArray()) {
+            return null;
+        }
+        return object.getAsJsonArray(key);
+    }
+
+    private static boolean optBoolean(JsonObject object, String key) {
+        if (object == null || !object.has(key) || !object.get(key).isJsonPrimitive()
+                || !object.get(key).getAsJsonPrimitive().isBoolean()) {
+            return false;
+        }
+        return object.get(key).getAsBoolean();
+    }
+
+    private static boolean isString(JsonElement element) {
+        return element != null && element.isJsonPrimitive() && element.getAsJsonPrimitive().isString();
+    }
+
     private static JsonArray getJsonArray(String url) throws IOException {
         String body = httpGet(url);
-        JsonElement parsed = JsonParser.parseString(body);
-        if (!parsed.isJsonArray()) {
-            throw new IOException("Unexpected response from " + url);
+        try {
+            JsonElement parsed = JsonParser.parseString(body);
+            if (!parsed.isJsonArray()) {
+                throw new IOException("Unexpected response from " + url);
+            }
+            return parsed.getAsJsonArray();
+        } catch (RuntimeException e) {
+            throw new IOException("Invalid JSON response from " + url, e);
         }
-        return parsed.getAsJsonArray();
     }
 
     private static String httpGet(String url) throws IOException {
@@ -298,17 +364,36 @@ public final class ModrinthResolver {
             throw new IOException("HTTP " + code + " from " + url);
         }
 
-        StringBuilder builder = new StringBuilder();
         try (InputStream input = connection.getInputStream();
-             BufferedReader reader = new BufferedReader(new InputStreamReader(input, StandardCharsets.UTF_8))) {
-            String line;
-            while ((line = reader.readLine()) != null) {
-                builder.append(line);
-            }
+             InputStreamReader reader = new InputStreamReader(input, StandardCharsets.UTF_8)) {
+            return readBoundedApiResponse(reader, url, MAX_API_RESPONSE_CHARS);
         } finally {
             connection.disconnect();
         }
-        return builder.toString();
+    }
+
+    static String readBoundedApiResponse(Reader reader, String source, int maxChars) throws IOException {
+        if (maxChars < 1) {
+            throw new IllegalArgumentException("Response character limit must be positive");
+        }
+        int bufferSize = maxChars < 8192 ? maxChars + 1 : 8192;
+        char[] buffer = new char[bufferSize];
+        StringBuilder builder = new StringBuilder(Math.min(maxChars, 8192));
+        while (true) {
+            int remaining = maxChars - builder.length();
+            int requested = remaining >= buffer.length ? buffer.length : remaining + 1;
+            int length = reader.read(buffer, 0, requested);
+            if (length == -1) {
+                return builder.toString();
+            }
+            if (length == 0) {
+                continue;
+            }
+            if (length > remaining) {
+                throw new IOException("Oversized response from " + source);
+            }
+            builder.append(buffer, 0, length);
+        }
     }
 
     private static final class ModrinthRef {
@@ -328,14 +413,16 @@ public final class ModrinthResolver {
         private final String versionId;
         private final String versionNumber;
         private final String projectSlug;
+        private final boolean direct;
 
-        public ResolvedDatapack(String downloadUrl, String fileName, String sha1, String versionId, String versionNumber, String projectSlug) {
+        public ResolvedDatapack(String downloadUrl, String fileName, String sha1, String versionId, String versionNumber, String projectSlug, boolean direct) {
             this.downloadUrl = downloadUrl;
             this.fileName = fileName;
             this.sha1 = sha1;
             this.versionId = versionId;
             this.versionNumber = versionNumber;
             this.projectSlug = projectSlug;
+            this.direct = direct;
         }
 
         public String getDownloadUrl() {
@@ -361,5 +448,9 @@ public final class ModrinthResolver {
         public String getProjectSlug() {
             return projectSlug;
         }
+
+        public boolean isDirect() {
+            return direct;
+        }
     }
 }

core/src/main/java/art/arcane/iris/core/lifecycle/BukkitPublicBackend.java

@@ -45,8 +45,8 @@ final class BukkitPublicBackend implements WorldLifecycleBackend {
     }
 
     @Override
-    public boolean unload(World world, boolean save) {
-        return WorldLifecycleSupport.unloadWorld(capabilities, world, save);
+    public CompletableFuture<Boolean> unloadAsync(World world, boolean save) {
+        return WorldLifecycleSupport.unloadWorldAsync(capabilities, world, save);
     }
 
     @Override

core/src/main/java/art/arcane/iris/core/lifecycle/BukkitWorldConfiguration.java

@@ -0,0 +1,194 @@
+package art.arcane.iris.core.lifecycle;
+
+import org.bukkit.configuration.ConfigurationSection;
+import org.bukkit.configuration.InvalidConfigurationException;
+import org.bukkit.configuration.file.YamlConfiguration;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.util.Objects;
+import java.util.ArrayList;
+import java.util.function.Predicate;
+
+public final class BukkitWorldConfiguration {
+    private static final Object MUTATION_LOCK = new Object();
+
+    private BukkitWorldConfiguration() {
+    }
+
+    public static Registration register(File configurationFile, String worldName, String dimension, Long seed) throws IOException {
+        Objects.requireNonNull(configurationFile, "configurationFile");
+        String requiredWorldName = requireWorldName(worldName);
+        String requiredDimension = requireName(dimension, "Dimension");
+        synchronized (MUTATION_LOCK) {
+            YamlConfiguration configuration = load(configurationFile);
+            ConfigurationSection worlds = configuration.getConfigurationSection("worlds");
+            if (worlds == null) {
+                worlds = configuration.createSection("worlds");
+            }
+
+            ConfigurationSection existing = worlds.getConfigurationSection(requiredWorldName);
+            String generator = "Iris:" + requiredDimension;
+            if (existing != null) {
+                String existingGenerator = existing.getString("generator");
+                Long existingSeed = existing.contains("seed") ? existing.getLong("seed") : null;
+                if (!generator.equals(existingGenerator) || !Objects.equals(seed, existingSeed)) {
+                    throw new IOException("bukkit.yml already contains a different definition for world \""
+                            + requiredWorldName + "\".");
+                }
+                return Registration.UNCHANGED;
+            }
+
+            ConfigurationSection created = worlds.createSection(requiredWorldName);
+            created.set("generator", generator);
+            if (seed != null) {
+                created.set("seed", seed);
+            }
+            saveAtomic(configurationFile.toPath(), configuration);
+            return Registration.CREATED;
+        }
+    }
+
+    public static boolean remove(File configurationFile, String worldName) throws IOException {
+        Objects.requireNonNull(configurationFile, "configurationFile");
+        String requiredWorldName = requireWorldName(worldName);
+        synchronized (MUTATION_LOCK) {
+            YamlConfiguration configuration = load(configurationFile);
+            ConfigurationSection worlds = configuration.getConfigurationSection("worlds");
+            if (worlds == null || worlds.get(requiredWorldName) == null) {
+                return false;
+            }
+
+            worlds.set(requiredWorldName, null);
+            if (worlds.getKeys(false).isEmpty()) {
+                configuration.set("worlds", null);
+            }
+            saveAtomic(configurationFile.toPath(), configuration);
+            return true;
+        }
+    }
+
+    public static boolean removeIfMatching(
+            File configurationFile,
+            String worldName,
+            String dimension,
+            Long seed
+    ) throws IOException {
+        Objects.requireNonNull(configurationFile, "configurationFile");
+        String requiredWorldName = requireWorldName(worldName);
+        String requiredDimension = requireName(dimension, "Dimension");
+        synchronized (MUTATION_LOCK) {
+            YamlConfiguration configuration = load(configurationFile);
+            ConfigurationSection worlds = configuration.getConfigurationSection("worlds");
+            if (worlds == null) {
+                return false;
+            }
+
+            ConfigurationSection existing = worlds.getConfigurationSection(requiredWorldName);
+            if (existing == null) {
+                return false;
+            }
+            String expectedGenerator = "Iris:" + requiredDimension;
+            String actualGenerator = existing.getString("generator");
+            Long actualSeed = existing.contains("seed") ? existing.getLong("seed") : null;
+            if (!expectedGenerator.equals(actualGenerator) || !Objects.equals(seed, actualSeed)) {
+                return false;
+            }
+
+            worlds.set(requiredWorldName, null);
+            if (worlds.getKeys(false).isEmpty()) {
+                configuration.set("worlds", null);
+            }
+            saveAtomic(configurationFile.toPath(), configuration);
+            return true;
+        }
+    }
+
+    public static int removeMatching(File configurationFile, Predicate<String> matcher) throws IOException {
+        Objects.requireNonNull(configurationFile, "configurationFile");
+        Predicate<String> requiredMatcher = Objects.requireNonNull(matcher, "matcher");
+        synchronized (MUTATION_LOCK) {
+            YamlConfiguration configuration = load(configurationFile);
+            ConfigurationSection worlds = configuration.getConfigurationSection("worlds");
+            if (worlds == null) {
+                return 0;
+            }
+
+            int removed = 0;
+            for (String worldName : new ArrayList<>(worlds.getKeys(false))) {
+                if (!requiredMatcher.test(worldName)) {
+                    continue;
+                }
+                worlds.set(worldName, null);
+                removed++;
+            }
+            if (removed == 0) {
+                return 0;
+            }
+            if (worlds.getKeys(false).isEmpty()) {
+                configuration.set("worlds", null);
+            }
+            saveAtomic(configurationFile.toPath(), configuration);
+            return removed;
+        }
+    }
+
+    static void saveAtomic(Path target, YamlConfiguration configuration) throws IOException {
+        Path absoluteTarget = target.toAbsolutePath().normalize();
+        Path parent = absoluteTarget.getParent();
+        if (parent == null) {
+            throw new IOException("bukkit.yml target has no parent: " + absoluteTarget);
+        }
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".bukkit-worlds-", ".yml");
+        try {
+            configuration.save(staged.toFile());
+            try (FileChannel channel = FileChannel.open(staged, StandardOpenOption.WRITE)) {
+                channel.force(true);
+            }
+            try {
+                Files.move(staged, absoluteTarget, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(staged, absoluteTarget, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    private static YamlConfiguration load(File configurationFile) throws IOException {
+        YamlConfiguration configuration = new YamlConfiguration();
+        try {
+            configuration.load(configurationFile);
+            return configuration;
+        } catch (InvalidConfigurationException exception) {
+            throw new IOException("bukkit.yml is invalid and was not changed.", exception);
+        }
+    }
+
+    private static String requireWorldName(String value) {
+        String worldName = requireName(value, "World name");
+        if (!worldName.matches("[a-z0-9_-]+")) {
+            throw new IllegalArgumentException("World name must contain only lowercase letters, numbers, underscores, or hyphens.");
+        }
+        return worldName;
+    }
+
+    private static String requireName(String value, String label) {
+        if (value == null || value.isBlank()) {
+            throw new IllegalArgumentException(label + " cannot be empty.");
+        }
+        return value.trim();
+    }
+
+    public enum Registration {
+        CREATED,
+        UNCHANGED
+    }
+}

core/src/main/java/art/arcane/iris/core/lifecycle/LifecycleOperationCoordinator.java

@@ -0,0 +1,275 @@
+package art.arcane.iris.core.lifecycle;
+
+import art.arcane.iris.spi.IrisLogging;
+
+import java.util.ArrayDeque;
+import java.util.Collections;
+import java.util.EnumMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public final class LifecycleOperationCoordinator {
+    private static final LifecycleOperationCoordinator INSTANCE = new LifecycleOperationCoordinator();
+
+    private final Object monitor;
+    private final ArrayDeque<Runnable> idleCallbacks;
+    private ActiveOperation mutationOperation;
+    private ActiveOperation restartOperation;
+    private Runnable pendingRestartCallback;
+    private long nextOperationId;
+
+    LifecycleOperationCoordinator() {
+        monitor = new Object();
+        idleCallbacks = new ArrayDeque<>();
+        nextOperationId = 1L;
+    }
+
+    public static LifecycleOperationCoordinator get() {
+        return INSTANCE;
+    }
+
+    public Lease acquire(Domain domain, OperationKind kind, String target) {
+        Objects.requireNonNull(domain, "domain");
+        Objects.requireNonNull(kind, "kind");
+        String normalizedTarget = Objects.requireNonNull(target, "target").trim();
+        if (normalizedTarget.isEmpty()) {
+            throw new IllegalArgumentException("target must not be blank");
+        }
+
+        synchronized (monitor) {
+            if (domain == Domain.SERVER_LIFECYCLE) {
+                throw new IllegalArgumentException("SERVER_LIFECYCLE is reserved for terminal operations");
+            }
+
+            ActiveOperation currentOperation = restartOperation == null ? mutationOperation : restartOperation;
+            if (currentOperation != null) {
+                throw new BusyException(currentOperation);
+            }
+
+            ActiveOperation operation = new ActiveOperation(nextOperationId++, domain, kind, normalizedTarget);
+            mutationOperation = operation;
+            return new LeaseImpl(this, operation);
+        }
+    }
+
+    public boolean quiesceForRestart(Runnable callback) {
+        Runnable restartCallback = Objects.requireNonNull(callback, "callback");
+        ActiveOperation operation;
+        boolean dispatch;
+        synchronized (monitor) {
+            if (restartOperation != null) {
+                return false;
+            }
+
+            operation = new ActiveOperation(
+                    nextOperationId++,
+                    Domain.SERVER_LIFECYCLE,
+                    OperationKind.SERVER_RESTART,
+                    "server");
+            restartOperation = operation;
+            dispatch = mutationOperation == null;
+            if (!dispatch) {
+                pendingRestartCallback = restartCallback;
+                return true;
+            }
+        }
+
+        runRestartCallback(restartCallback, operation);
+        return true;
+    }
+
+    public Optional<ActiveOperation> active(Domain domain) {
+        Objects.requireNonNull(domain, "domain");
+        synchronized (monitor) {
+            if (domain == Domain.SERVER_LIFECYCLE) {
+                return Optional.ofNullable(restartOperation);
+            }
+            if (mutationOperation != null && mutationOperation.domain() == domain) {
+                return Optional.of(mutationOperation);
+            }
+            return Optional.empty();
+        }
+    }
+
+    public Map<Domain, ActiveOperation> snapshot() {
+        synchronized (monitor) {
+            EnumMap<Domain, ActiveOperation> operations = new EnumMap<>(Domain.class);
+            if (mutationOperation != null) {
+                operations.put(mutationOperation.domain(), mutationOperation);
+            }
+            if (restartOperation != null) {
+                operations.put(Domain.SERVER_LIFECYCLE, restartOperation);
+            }
+            return Collections.unmodifiableMap(operations);
+        }
+    }
+
+    public boolean isIdle() {
+        synchronized (monitor) {
+            return mutationOperation == null && restartOperation == null;
+        }
+    }
+
+    public void whenIdle(Runnable callback) {
+        Runnable idleCallback = Objects.requireNonNull(callback, "callback");
+        synchronized (monitor) {
+            if (mutationOperation != null || restartOperation != null) {
+                idleCallbacks.addLast(idleCallback);
+                return;
+            }
+            runIdleCallback(idleCallback);
+        }
+    }
+
+    private void release(ActiveOperation operation) {
+        Runnable restartCallback = null;
+        ActiveOperation terminalOperation = null;
+        synchronized (monitor) {
+            if (!operation.equals(mutationOperation)) {
+                throw new IllegalStateException("Lifecycle operation lease is not active: " + operation.id());
+            }
+
+            mutationOperation = null;
+            if (restartOperation != null && pendingRestartCallback != null) {
+                terminalOperation = restartOperation;
+                restartCallback = pendingRestartCallback;
+                pendingRestartCallback = null;
+            } else {
+                runIdleCallbacks();
+            }
+        }
+
+        if (restartCallback != null) {
+            runRestartCallback(restartCallback, terminalOperation);
+        }
+    }
+
+    private void runIdleCallbacks() {
+        while (mutationOperation == null && restartOperation == null && !idleCallbacks.isEmpty()) {
+            runIdleCallback(idleCallbacks.removeFirst());
+        }
+    }
+
+    private void runIdleCallback(Runnable callback) {
+        try {
+            callback.run();
+        } catch (Throwable failure) {
+            IrisLogging.reportError("Lifecycle idle callback failed.", failure);
+        }
+    }
+
+    private void runRestartCallback(Runnable callback, ActiveOperation operation) {
+        try {
+            callback.run();
+        } catch (Throwable failure) {
+            IrisLogging.reportError("Lifecycle restart dispatch failed for operation " + operation.id() + ".", failure);
+        }
+    }
+
+    public enum Domain {
+        WORLD_MUTATION,
+        PACK_MUTATION,
+        SERVER_LIFECYCLE
+    }
+
+    public enum OperationKind {
+        WORLD_CREATE,
+        WORLD_LOAD,
+        WORLD_UNLOAD,
+        WORLD_REMOVE,
+        WORLD_PROMOTE,
+        STUDIO_OPEN,
+        STUDIO_CLOSE,
+        PACK_CREATE,
+        PACK_DOWNLOAD,
+        PACK_PUBLISH,
+        DATAPACK_COMPILE,
+        SERVER_RESTART
+    }
+
+    public record ActiveOperation(long id, Domain domain, OperationKind kind, String target) {
+        public ActiveOperation {
+            if (id < 1L) {
+                throw new IllegalArgumentException("id must be positive");
+            }
+            Objects.requireNonNull(domain, "domain");
+            Objects.requireNonNull(kind, "kind");
+            target = Objects.requireNonNull(target, "target").trim();
+            if (target.isEmpty()) {
+                throw new IllegalArgumentException("target must not be blank");
+            }
+        }
+    }
+
+    public static final class BusyException extends IllegalStateException {
+        private final ActiveOperation currentOperation;
+
+        private BusyException(ActiveOperation currentOperation) {
+            super("Lifecycle domain " + currentOperation.domain()
+                    + " is busy with " + currentOperation.kind()
+                    + " target=" + currentOperation.target()
+                    + " id=" + currentOperation.id());
+            this.currentOperation = currentOperation;
+        }
+
+        public ActiveOperation currentOperation() {
+            return currentOperation;
+        }
+
+        public long operationId() {
+            return currentOperation.id();
+        }
+
+        public Domain domain() {
+            return currentOperation.domain();
+        }
+
+        public OperationKind operationKind() {
+            return currentOperation.kind();
+        }
+
+        public String target() {
+            return currentOperation.target();
+        }
+    }
+
+    public interface Lease extends AutoCloseable {
+        ActiveOperation operation();
+
+        boolean isClosed();
+
+        @Override
+        void close();
+    }
+
+    private static final class LeaseImpl implements Lease {
+        private final LifecycleOperationCoordinator coordinator;
+        private final ActiveOperation operation;
+        private final AtomicBoolean closed;
+
+        private LeaseImpl(LifecycleOperationCoordinator coordinator, ActiveOperation operation) {
+            this.coordinator = coordinator;
+            this.operation = operation;
+            closed = new AtomicBoolean();
+        }
+
+        @Override
+        public ActiveOperation operation() {
+            return operation;
+        }
+
+        @Override
+        public boolean isClosed() {
+            return closed.get();
+        }
+
+        @Override
+        public void close() {
+            if (closed.compareAndSet(false, true)) {
+                coordinator.release(operation);
+            }
+        }
+    }
+}

core/src/main/java/art/arcane/iris/core/lifecycle/PaperLikeRuntimeBackend.java

@@ -81,8 +81,8 @@ final class PaperLikeRuntimeBackend implements WorldLifecycleBackend {
     }
 
     @Override
-    public boolean unload(World world, boolean save) {
-        return WorldLifecycleSupport.unloadWorld(capabilities, world, save);
+    public CompletableFuture<Boolean> unloadAsync(World world, boolean save) {
+        return WorldLifecycleSupport.unloadWorldAsync(capabilities, world, save);
     }
 
     @Override

core/src/main/java/art/arcane/iris/core/lifecycle/WorldLifecycleBackend.java

@@ -9,7 +9,7 @@ public interface WorldLifecycleBackend {
 
     CompletableFuture<World> create(WorldLifecycleRequest request);
 
-    boolean unload(World world, boolean save);
+    CompletableFuture<Boolean> unloadAsync(World world, boolean save);
 
     String backendName();
 }

core/src/main/java/art/arcane/iris/core/lifecycle/WorldLifecycleService.java

@@ -1,6 +1,8 @@
 package art.arcane.iris.core.lifecycle;
 
+import art.arcane.iris.core.ServerConfigurator;
 import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.util.common.scheduling.J;
 import art.arcane.volmlib.util.bukkit.WorldIdentity;
 import org.bukkit.NamespacedKey;
@@ -8,25 +10,43 @@ import org.bukkit.World;
 
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 
 public final class WorldLifecycleService {
+    private static final long UNLOAD_TIMEOUT_SECONDS = 120L;
     private static volatile WorldLifecycleService instance;
 
     private final CapabilitySnapshot capabilities;
-    private final WorldsProviderBackend worldsProviderBackend;
-    private final PaperLikeRuntimeBackend paperLikeRuntimeBackend;
-    private final BukkitPublicBackend bukkitPublicBackend;
+    private final WorldLifecycleBackend worldsProviderBackend;
+    private final WorldLifecycleBackend paperLikeRuntimeBackend;
+    private final WorldLifecycleBackend bukkitPublicBackend;
     private final List<WorldLifecycleBackend> backends;
     private final Map<String, String> worldBackendByKey;
 
     public WorldLifecycleService(CapabilitySnapshot capabilities) {
-        this.capabilities = capabilities;
-        this.worldsProviderBackend = new WorldsProviderBackend(capabilities);
-        this.paperLikeRuntimeBackend = new PaperLikeRuntimeBackend(capabilities);
-        this.bukkitPublicBackend = new BukkitPublicBackend(capabilities);
+        this(
+                capabilities,
+                new WorldsProviderBackend(capabilities),
+                new PaperLikeRuntimeBackend(capabilities),
+                new BukkitPublicBackend(capabilities)
+        );
+    }
+
+    WorldLifecycleService(
+            CapabilitySnapshot capabilities,
+            WorldLifecycleBackend worldsProviderBackend,
+            WorldLifecycleBackend paperLikeRuntimeBackend,
+            WorldLifecycleBackend bukkitPublicBackend
+    ) {
+        this.capabilities = Objects.requireNonNull(capabilities, "capabilities");
+        this.worldsProviderBackend = Objects.requireNonNull(worldsProviderBackend, "worldsProviderBackend");
+        this.paperLikeRuntimeBackend = Objects.requireNonNull(paperLikeRuntimeBackend, "paperLikeRuntimeBackend");
+        this.bukkitPublicBackend = Objects.requireNonNull(bukkitPublicBackend, "bukkitPublicBackend");
         this.backends = List.of(worldsProviderBackend, paperLikeRuntimeBackend, bukkitPublicBackend);
         this.worldBackendByKey = new ConcurrentHashMap<>();
     }
@@ -89,47 +109,83 @@ public final class WorldLifecycleService {
         }
     }
 
-    public boolean unload(World world, boolean save) {
-        if (!J.isPrimaryThread()) {
-            CompletableFuture<Boolean> future = new CompletableFuture<>();
-            J.s(() -> {
-                try {
-                    future.complete(unloadDirect(world, save));
-                } catch (Throwable e) {
-                    future.completeExceptionally(e);
-                }
-            });
-            return future.join();
-        }
-
-        return unloadDirect(world, save);
-    }
-
-    private boolean unloadDirect(World world, boolean save) {
-        String worldIdentity = WorldIdentity.serialize(world);
+    public CompletableFuture<Boolean> unloadAsync(World world, boolean save) {
+        World requiredWorld = Objects.requireNonNull(world, "world");
+        String worldIdentity = WorldIdentity.serialize(requiredWorld);
+        String worldName = requiredWorld.getName();
         WorldLifecycleBackend backend = selectUnloadBackend(worldIdentity);
         IrisLogging.info("WorldLifecycle unload: world=%s, backend=%s",
-                world.getName(),
+                worldName,
                 backend.backendName());
-        boolean unloaded;
+
+        CompletableFuture<Boolean> unloadFuture;
         try {
-            unloaded = backend.unload(world, save);
+            unloadFuture = backend.unloadAsync(requiredWorld, save);
+            if (unloadFuture == null) {
+                throw new IllegalStateException("World lifecycle backend returned no unload completion future.");
+            }
         } catch (Throwable e) {
-            IrisLogging.reportError("WorldLifecycle unload failed: world=\"" + world.getName()
-                    + "\", backend=" + backend.backendName()
-                    + ", family=" + capabilities.serverFamily().id() + ".", e);
-            if (e instanceof RuntimeException runtimeException) {
+            unloadFuture = CompletableFuture.failedFuture(e);
+        }
+
+        CompletableFuture<Boolean> guardedFuture = guardUnloadCompletion(worldName, unloadFuture);
+        return guardedFuture.whenComplete((unloaded, throwable) -> {
+            if (throwable != null) {
+                Throwable cause = WorldLifecycleSupport.unwrap(throwable);
+                IrisLogging.reportError("WorldLifecycle unload failed: world=\"" + worldName
+                        + "\", backend=" + backend.backendName()
+                        + ", family=" + capabilities.serverFamily().id() + ".", cause);
+                return;
+            }
+            if (Boolean.TRUE.equals(unloaded)) {
+                worldBackendByKey.remove(worldIdentity, backend.backendName());
+            }
+        });
+    }
+
+    private CompletableFuture<Boolean> guardUnloadCompletion(
+            String worldName,
+            CompletableFuture<Boolean> unloadFuture
+    ) {
+        CompletableFuture<Boolean> guarded = new CompletableFuture<>();
+        unloadFuture.whenComplete((unloaded, throwable) -> {
+            if (throwable == null) {
+                guarded.complete(Boolean.TRUE.equals(unloaded));
+            } else {
+                guarded.completeExceptionally(WorldLifecycleSupport.unwrap(throwable));
+            }
+        });
+        if (!guarded.isDone()) {
+            CompletableFuture.delayedExecutor(UNLOAD_TIMEOUT_SECONDS, TimeUnit.SECONDS).execute(() -> {
+                TimeoutException timeout = new TimeoutException(
+                        "World unload did not settle within " + UNLOAD_TIMEOUT_SECONDS + " seconds for \""
+                                + worldName + "\".");
+                if (!guarded.completeExceptionally(timeout) || IrisToolbelt.isServerStopping()) {
+                    return;
+                }
+                ServerConfigurator.restart("World unload timed out for \"" + worldName + "\".");
+            });
+        }
+        return guarded;
+    }
+
+    public boolean unload(World world, boolean save) {
+        if (J.isPrimaryThread() || (J.isFolia() && WorldLifecycleSupport.isGlobalTickThread())) {
+            throw new IllegalStateException("WorldLifecycle unload cannot block the primary/global tick thread; use unloadAsync instead.");
+        }
+
+        try {
+            return Boolean.TRUE.equals(unloadAsync(world, save).join());
+        } catch (CompletionException e) {
+            Throwable cause = WorldLifecycleSupport.unwrap(e);
+            if (cause instanceof RuntimeException runtimeException) {
                 throw runtimeException;
             }
-            if (e instanceof Error error) {
+            if (cause instanceof Error error) {
                 throw error;
             }
-            throw new IllegalStateException(e);
+            throw new IllegalStateException(cause);
         }
-        if (unloaded) {
-            worldBackendByKey.remove(worldIdentity);
-        }
-        return unloaded;
     }
 
     public String backendNameForWorld(NamespacedKey worldKey) {

core/src/main/java/art/arcane/iris/core/lifecycle/WorldLifecycleSupport.java

@@ -5,8 +5,10 @@ import art.arcane.iris.core.link.Identifier;
 import art.arcane.iris.core.nms.INMS;
 import art.arcane.iris.core.nms.INMSBinding;
 import art.arcane.iris.engine.platform.PlatformChunkGenerator;
+import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.util.common.scheduling.J;
 import art.arcane.volmlib.util.bukkit.WorldIdentity;
+import art.arcane.volmlib.util.scheduling.FoliaScheduler;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.NamespacedKey;
@@ -414,36 +416,83 @@ final class WorldLifecycleSupport {
         }
     }
 
-    static boolean unloadWorld(CapabilitySnapshot capabilities, World world, boolean save) {
+    static CompletableFuture<Boolean> unloadWorldAsync(CapabilitySnapshot capabilities, World world, boolean save) {
         if (world == null) {
-            return false;
+            return CompletableFuture.completedFuture(false);
         }
 
-        CompletableFuture<Boolean> asyncUnload = unloadWorldViaAsyncApi(capabilities, world, save);
-        if (asyncUnload != null) {
-            return resolveAsyncUnload(asyncUnload);
+        CompletableFuture<Boolean> result = new CompletableFuture<>();
+        Runnable invokeTask = () -> beginUnload(capabilities, world, save, result);
+        boolean folia = J.isFolia();
+        if ((!folia && J.isPrimaryThread()) || (folia && isGlobalTickThread())) {
+            invokeTask.run();
+            return result;
         }
 
-        try {
-            return Bukkit.unloadWorld(world, save);
-        } catch (UnsupportedOperationException unsupported) {
-            if (capabilities.minecraftServer() == null || capabilities.removeLevelMethod() == null) {
-                throw unsupported;
+        CompletableFuture<Void> scheduled = runGlobalAsync(invokeTask);
+        scheduled.whenComplete((unused, throwable) -> {
+            if (throwable != null) {
+                result.completeExceptionally(unwrap(throwable));
             }
+        });
+        return result;
+    }
+
+    private static void beginUnload(
+            CapabilitySnapshot capabilities,
+            World world,
+            boolean save,
+            CompletableFuture<Boolean> result
+    ) {
+        CompletableFuture<Boolean> operation;
+        try {
+            operation = unloadWorldViaAsyncApi(capabilities, world, save);
+            if (operation == null) {
+                operation = unloadWorldWithoutAsyncApi(capabilities, world, save);
+            }
+        } catch (Throwable e) {
+            result.completeExceptionally(unwrap(e));
+            return;
         }
 
+        operation.whenComplete((unloaded, throwable) -> {
+            if (throwable == null) {
+                result.complete(Boolean.TRUE.equals(unloaded));
+            } else {
+                result.completeExceptionally(unwrap(throwable));
+            }
+        });
+    }
+
+    private static CompletableFuture<Boolean> unloadWorldWithoutAsyncApi(
+            CapabilitySnapshot capabilities,
+            World world,
+            boolean save
+    ) {
+        String worldName = world.getName();
         try {
+            try {
+                return CompletableFuture.completedFuture(Bukkit.unloadWorld(world, save));
+            } catch (UnsupportedOperationException unsupported) {
+                if (capabilities.minecraftServer() == null || capabilities.removeLevelMethod() == null) {
+                    return CompletableFuture.failedFuture(unsupported);
+                }
+            }
+
             if (save) {
                 world.save();
             }
-
             Method getHandleMethod = world.getClass().getMethod("getHandle");
             Object serverLevel = getHandleMethod.invoke(world);
-            closeServerLevel(world, serverLevel);
-            detachServerLevel(capabilities, serverLevel, world);
-            return WorldIdentity.resolve(WorldIdentity.key(world)).isEmpty();
+            CompletableFuture<Boolean> operation = closeServerLevelAsync(world, serverLevel)
+                    .thenCompose(unused -> detachServerLevelAsync(capabilities, serverLevel, world))
+                    .thenApply(unused -> WorldIdentity.resolve(WorldIdentity.key(world)).isEmpty());
+            return contextualizeUnloadFailure(worldName, operation);
         } catch (Throwable e) {
-            throw new IllegalStateException("Failed to unload world \"" + world.getName() + "\" through the selected world lifecycle backend.", unwrap(e));
+            return CompletableFuture.failedFuture(new IllegalStateException(
+                    "Failed to unload world \"" + worldName + "\" through the selected world lifecycle backend.",
+                    unwrap(e)
+            ));
         }
     }
 
@@ -452,63 +501,70 @@ final class WorldLifecycleSupport {
             return null;
         }
 
+        return invokeAsyncUnload(
+                capabilities.bukkitServer(),
+                capabilities.unloadWorldAsyncMethod(),
+                world,
+                save
+        );
+    }
+
+    static CompletableFuture<Boolean> invokeAsyncUnload(
+            Object bukkitServer,
+            Method unloadWorldAsyncMethod,
+            World world,
+            boolean save
+    ) {
         CompletableFuture<Boolean> callbackFuture = new CompletableFuture<>();
-        Runnable invokeTask = () -> {
-            Consumer<Boolean> callback = result -> callbackFuture.complete(Boolean.TRUE.equals(result));
-            try {
-                capabilities.unloadWorldAsyncMethod().invoke(capabilities.bukkitServer(), world, save, callback);
-            } catch (Throwable e) {
-                callbackFuture.completeExceptionally(unwrap(e));
-            }
-        };
-
-        if (J.isFolia() && !isGlobalTickThread()) {
-            CompletableFuture<Void> scheduled = J.sfut(invokeTask);
-            if (scheduled == null) {
-                callbackFuture.completeExceptionally(new IllegalStateException("Failed to schedule global unload task."));
-                return callbackFuture;
-            }
-            scheduled.whenComplete((unused, throwable) -> {
-                if (throwable != null) {
-                    callbackFuture.completeExceptionally(unwrap(throwable));
-                }
-            });
-            return callbackFuture;
+        Consumer<Boolean> callback = unloaded -> callbackFuture.complete(Boolean.TRUE.equals(unloaded));
+        try {
+            unloadWorldAsyncMethod.invoke(bukkitServer, world, save, callback);
+        } catch (Throwable e) {
+            callbackFuture.completeExceptionally(unwrap(e));
         }
-
-        invokeTask.run();
         return callbackFuture;
     }
 
-    private static boolean resolveAsyncUnload(CompletableFuture<Boolean> asyncUnload) {
-        if (J.isPrimaryThread()) {
-            if (!asyncUnload.isDone()) {
-                return true;
+    private static CompletableFuture<Boolean> contextualizeUnloadFailure(
+            String worldName,
+            CompletableFuture<Boolean> operation
+    ) {
+        CompletableFuture<Boolean> result = new CompletableFuture<>();
+        operation.whenComplete((unloaded, throwable) -> {
+            if (throwable == null) {
+                result.complete(Boolean.TRUE.equals(unloaded));
+            } else {
+                result.completeExceptionally(new IllegalStateException(
+                        "Failed to unload world \"" + worldName + "\" through the selected world lifecycle backend.",
+                        unwrap(throwable)
+                ));
             }
-
-            try {
-                return Boolean.TRUE.equals(asyncUnload.join());
-            } catch (Throwable e) {
-                throw new IllegalStateException("Failed to consume async world unload result.", unwrap(e));
-            }
-        }
-
-        try {
-            return Boolean.TRUE.equals(asyncUnload.get(120, TimeUnit.SECONDS));
-        } catch (Throwable e) {
-            throw new IllegalStateException("Failed while waiting for async world unload result.", unwrap(e));
-        }
+        });
+        return result;
     }
 
-    private static void closeServerLevel(World world, Object serverLevel) throws Throwable {
-        Method closeMethod = CapabilityResolution.resolveMethod(serverLevel.getClass(), "close", method -> method.getParameterCount() == 0);
+    private static CompletableFuture<Void> closeServerLevelAsync(World world, Object serverLevel) {
+        Method closeMethod;
+        try {
+            closeMethod = CapabilityResolution.resolveMethod(
+                    serverLevel.getClass(),
+                    "close",
+                    method -> method.getParameterCount() == 0
+            );
+        } catch (Throwable e) {
+            return CompletableFuture.failedFuture(unwrap(e));
+        }
         if (closeMethod == null) {
-            return;
+            return CompletableFuture.completedFuture(null);
         }
 
         if (!J.isFolia()) {
-            closeMethod.invoke(serverLevel);
-            return;
+            try {
+                closeMethod.invoke(serverLevel);
+                return CompletableFuture.completedFuture(null);
+            } catch (Throwable e) {
+                return CompletableFuture.failedFuture(unwrap(e));
+            }
         }
 
         Location spawn = world.getSpawnLocation();
@@ -524,9 +580,11 @@ final class WorldLifecycleSupport {
             }
         });
         if (!scheduled) {
-            throw new IllegalStateException("Failed to schedule region close task for world \"" + world.getName() + "\".");
+            return CompletableFuture.failedFuture(new IllegalStateException(
+                    "Failed to schedule region close task for world \"" + world.getName() + "\"."
+            ));
         }
-        closeFuture.get(90, TimeUnit.SECONDS);
+        return closeFuture.orTimeout(90L, TimeUnit.SECONDS);
     }
 
     @SuppressWarnings({"rawtypes", "unchecked"})
@@ -545,7 +603,11 @@ final class WorldLifecycleSupport {
         }
     }
 
-    private static void detachServerLevel(CapabilitySnapshot capabilities, Object serverLevel, World world) throws Throwable {
+    private static CompletableFuture<Void> detachServerLevelAsync(
+            CapabilitySnapshot capabilities,
+            Object serverLevel,
+            World world
+    ) {
         Runnable detachTask = () -> {
             try {
                 capabilities.removeLevelMethod().invoke(capabilities.minecraftServer(), serverLevel);
@@ -556,15 +618,41 @@ final class WorldLifecycleSupport {
         };
 
         if (!J.isFolia() || isGlobalTickThread()) {
-            detachTask.run();
-            return;
+            try {
+                detachTask.run();
+                return CompletableFuture.completedFuture(null);
+            } catch (Throwable e) {
+                return CompletableFuture.failedFuture(unwrap(e));
+            }
         }
 
-        CompletableFuture<Void> detachFuture = J.sfut(detachTask);
-        if (detachFuture == null) {
-            throw new IllegalStateException("Failed to schedule global detach task for world \"" + world.getName() + "\".");
+        CompletableFuture<Void> detachFuture = runGlobalAsync(detachTask);
+        return detachFuture.orTimeout(15L, TimeUnit.SECONDS);
+    }
+
+    private static CompletableFuture<Void> runGlobalAsync(Runnable task) {
+        if (!J.isFolia()) {
+            return J.sfut(task);
         }
-        detachFuture.get(15, TimeUnit.SECONDS);
+
+        CompletableFuture<Void> result = new CompletableFuture<>();
+        Runnable settlement = () -> {
+            try {
+                task.run();
+                result.complete(null);
+            } catch (Throwable e) {
+                result.completeExceptionally(unwrap(e));
+            }
+        };
+
+        try {
+            if (!FoliaScheduler.runGlobal(BukkitPlatform.plugin(), settlement)) {
+                result.completeExceptionally(new IllegalStateException("Failed to schedule global world lifecycle task."));
+            }
+        } catch (Throwable e) {
+            result.completeExceptionally(unwrap(e));
+        }
+        return result;
     }
 
     static boolean isGlobalTickThread() {

core/src/main/java/art/arcane/iris/core/lifecycle/WorldsProviderBackend.java

@@ -46,8 +46,8 @@ final class WorldsProviderBackend implements WorldLifecycleBackend {
     }
 
     @Override
-    public boolean unload(World world, boolean save) {
-        return WorldLifecycleSupport.unloadWorld(capabilities, world, save);
+    public CompletableFuture<Boolean> unloadAsync(World world, boolean save) {
+        return WorldLifecycleSupport.unloadWorldAsync(capabilities, world, save);
     }
 
     @Override

core/src/main/java/art/arcane/iris/core/link/MultiverseCoreLink.java

@@ -22,28 +22,36 @@ import lombok.SneakyThrows;
 import org.bukkit.Bukkit;
 import org.bukkit.World;
 import org.mvplugins.multiverse.core.MultiverseCoreApi;
+import org.mvplugins.multiverse.core.utils.result.Attempt;
 import org.mvplugins.multiverse.core.world.MultiverseWorld;
 import org.mvplugins.multiverse.core.world.WorldManager;
 import org.mvplugins.multiverse.core.world.options.ImportWorldOptions;
 import org.mvplugins.multiverse.core.world.options.RemoveWorldOptions;
+import org.mvplugins.multiverse.core.world.reasons.RemoveFailureReason;
 
 import java.lang.reflect.Field;
 
 public class MultiverseCoreLink {
-    public void removeFromConfig(World world) {
-        removeFromConfig(world.getName());
+    public boolean removeFromConfig(World world) {
+        return removeFromConfig(world.getName());
     }
 
-    public void removeFromConfig(String world) {
+    public boolean removeFromConfig(String world) {
         if (!isActive()) {
-            return;
+            return false;
         }
         WorldManager manager = worldManager();
         MultiverseWorld multiverseWorld = manager.getWorld(world).getOrElse((MultiverseWorld) null);
         if (multiverseWorld == null) {
-            return;
+            return false;
         }
-        manager.removeWorld(RemoveWorldOptions.world(multiverseWorld)).onSuccess(ignored -> manager.saveWorldsConfig());
+        Attempt<String, RemoveFailureReason> removal = manager.removeWorld(RemoveWorldOptions.world(multiverseWorld));
+        if (removal.isFailure()) {
+            throw new IllegalStateException("Multiverse refused to remove world \"" + world + "\": "
+                    + removal.getFailureMessage());
+        }
+        manager.saveWorldsConfig().get();
+        return true;
     }
 
     @SneakyThrows
@@ -72,7 +80,7 @@ public class MultiverseCoreLink {
                     .invoke(config, generator);
         }
 
-        manager.saveWorldsConfig();
+        manager.saveWorldsConfig().get();
     }
 
     private WorldManager worldManager() {

core/src/main/java/art/arcane/iris/core/loader/IrisData.java

@@ -31,6 +31,7 @@ import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.JsonWriter;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.engine.data.cache.AtomicCache;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.IrisStructureLocator;
@@ -244,15 +245,14 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
                 }
             }
 
-            for (File i : Objects.requireNonNull(IrisPlatforms.get().dataFolder("packs").listFiles())) {
-                if (i.isDirectory()) {
-                    IrisData dm = get(i);
-                    if (dm == nearest) continue;
-                    T t = dm.load(type, key, false);
+            for (File i : PackDirectoryResolver.listVisiblePackDirectories(
+                    IrisPlatforms.get().dataFolder("packs"))) {
+                IrisData dm = get(i);
+                if (dm == nearest) continue;
+                T t = dm.load(type, key, false);
 
-                    if (t != null) {
-                        return t;
-                    }
+                if (t != null) {
+                    return t;
                 }
             }
         } catch (Throwable e) {

core/src/main/java/art/arcane/iris/core/nms/INMSBinding.java

@@ -28,6 +28,7 @@ import art.arcane.iris.engine.data.chunk.TerrainChunk;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.platform.PlatformChunkGenerator;
 import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.spi.PlatformStructureHooks.JigsawSourceMetadata;
 import art.arcane.iris.util.project.hunk.Hunk;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
@@ -106,6 +107,18 @@ public interface INMSBinding {
         return new KList<>();
     }
 
+    default JigsawSourceMetadata getJigsawSourceMetadata(String structureKey) {
+        throw new UnsupportedOperationException("The active NMS binding does not expose registered jigsaw metadata");
+    }
+
+    default int getTemplatePoolHorizontalSpan(String templatePoolKey) {
+        throw new UnsupportedOperationException("The active NMS binding does not expose registered template pool spans");
+    }
+
+    default int getJigsawStartPoolHorizontalSpan(String structureKey, String templatePoolKey) {
+        return getTemplatePoolHorizontalSpan(templatePoolKey);
+    }
+
     KList<String> getStructureSetKeys();
 
     KList<String> getReachableStructureKeys(World world);

core/src/main/java/art/arcane/iris/core/nms/MinecraftVersion.java

@@ -6,7 +6,7 @@ import java.lang.reflect.Method;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-final class MinecraftVersion {
+public final class MinecraftVersion {
     private static final Pattern DECORATED_VERSION_PATTERN = Pattern.compile("\\(MC: ([0-9]+(?:\\.[0-9]+){0,2})\\)");
 
     private final String value;

core/src/main/java/art/arcane/iris/core/pack/AtomicDirectoryPublisher.java

@@ -0,0 +1,113 @@
+package art.arcane.iris.core.pack;
+
+import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.Comparator;
+import java.util.Objects;
+import java.util.UUID;
+import java.util.stream.Stream;
+
+public final class AtomicDirectoryPublisher {
+    private AtomicDirectoryPublisher() {
+    }
+
+    public static Publication publish(Path stagedDirectory, Path targetDirectory) throws IOException {
+        Path staged = Objects.requireNonNull(stagedDirectory, "stagedDirectory").toAbsolutePath().normalize();
+        Path target = Objects.requireNonNull(targetDirectory, "targetDirectory").toAbsolutePath().normalize();
+        if (!Files.isDirectory(staged) || Files.isSymbolicLink(staged)) {
+            throw new IOException("Staged directory is missing or unsafe: " + staged);
+        }
+        if (!Objects.equals(staged.getParent(), target.getParent())) {
+            throw new IOException("Staged and target directories must have the same parent.");
+        }
+
+        Path backup = null;
+        if (Files.exists(target) || Files.isSymbolicLink(target)) {
+            backup = target.resolveSibling("." + target.getFileName() + ".backup-" + UUID.randomUUID());
+            move(target, backup);
+        }
+        try {
+            move(staged, target);
+            return new Publication(target, backup);
+        } catch (IOException failure) {
+            if (backup != null && (Files.exists(backup) || Files.isSymbolicLink(backup))) {
+                try {
+                    move(backup, target);
+                } catch (IOException rollbackFailure) {
+                    failure.addSuppressed(rollbackFailure);
+                }
+            }
+            throw failure;
+        }
+    }
+
+    private static void move(Path source, Path target) throws IOException {
+        try {
+            Files.move(source, target, StandardCopyOption.ATOMIC_MOVE);
+        } catch (AtomicMoveNotSupportedException exception) {
+            Files.move(source, target);
+        }
+    }
+
+    public static final class Publication implements AutoCloseable {
+        private final Path target;
+        private final Path backup;
+        private boolean committed;
+        private boolean closed;
+
+        private Publication(Path target, Path backup) {
+            this.target = target;
+            this.backup = backup;
+        }
+
+        public synchronized void commit() {
+            if (closed) {
+                throw new IllegalStateException("Directory publication is already closed.");
+            }
+            committed = true;
+        }
+
+        public synchronized void cleanupBackup() throws IOException {
+            if (!committed) {
+                throw new IllegalStateException("Directory publication is not committed.");
+            }
+            if (backup != null) {
+                deleteTree(backup);
+            }
+        }
+
+        @Override
+        public synchronized void close() throws IOException {
+            if (closed) {
+                return;
+            }
+            closed = true;
+            if (committed) {
+                return;
+            }
+
+            deleteTree(target);
+            if (backup != null && (Files.exists(backup) || Files.isSymbolicLink(backup))) {
+                move(backup, target);
+            }
+        }
+    }
+
+    public static void deleteTree(Path path) throws IOException {
+        if (!Files.exists(path) && !Files.isSymbolicLink(path)) {
+            return;
+        }
+        if (Files.isSymbolicLink(path) || !Files.isDirectory(path)) {
+            Files.delete(path);
+            return;
+        }
+        try (Stream<Path> stream = Files.walk(path)) {
+            for (Path entry : stream.sorted(Comparator.reverseOrder()).toList()) {
+                Files.deleteIfExists(entry);
+            }
+        }
+    }
+}

core/src/main/java/art/arcane/iris/core/pack/PackDirectoryResolver.java

@@ -1,9 +1,16 @@
 package art.arcane.iris.core.pack;
 
 import java.io.File;
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
 import java.nio.file.LinkOption;
 import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Stream;
 
 public final class PackDirectoryResolver {
     private PackDirectoryResolver() {
@@ -18,9 +25,103 @@ public final class PackDirectoryResolver {
         if (!root.equals(candidate.getParent())) {
             return null;
         }
-        if (Files.isSymbolicLink(candidate) || !Files.isDirectory(candidate, LinkOption.NOFOLLOW_LINKS)) {
+        if (!isVisiblePackDirectory(candidate.toFile())) {
             return null;
         }
         return candidate.toFile();
     }
+
+    public static List<File> listVisiblePackDirectories(File packsRoot) {
+        try {
+            return listVisiblePackDirectoriesOrThrow(packsRoot);
+        } catch (IOException exception) {
+            return List.of();
+        }
+    }
+
+    public static List<File> listVisiblePackDirectoriesOrThrow(File packsRoot) throws IOException {
+        if (packsRoot == null) {
+            return List.of();
+        }
+        Path root = packsRoot.toPath().toAbsolutePath().normalize();
+        if (!Files.exists(root, LinkOption.NOFOLLOW_LINKS)) {
+            return List.of();
+        }
+        if (Files.isSymbolicLink(root) || !Files.isDirectory(root, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Pack workspace is missing or unsafe: " + root);
+        }
+        try (Stream<Path> stream = Files.list(root)) {
+            return stream
+                    .map(Path::toFile)
+                    .filter(PackDirectoryResolver::isVisiblePackDirectory)
+                    .sorted(Comparator.comparing(File::getName, String.CASE_INSENSITIVE_ORDER)
+                            .thenComparing(File::getName))
+                    .toList();
+        }
+    }
+
+    public static boolean isVisiblePackDirectory(File candidate) {
+        if (candidate == null || isHiddenName(candidate.getName())) {
+            return false;
+        }
+        Path path = candidate.toPath();
+        return Files.isDirectory(path);
+    }
+
+    public static void requireSafePackTree(File candidate) throws IOException {
+        if (!isVisiblePackDirectory(candidate)) {
+            throw new IOException("Pack directory is missing or unsafe: " + candidate);
+        }
+        Path root = candidate.toPath().toAbsolutePath().normalize().toRealPath();
+        if (Files.isSymbolicLink(root) || !Files.isDirectory(root, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Pack directory target is missing or unsafe: " + candidate);
+        }
+        Files.walkFileTree(root, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult preVisitDirectory(Path directory, BasicFileAttributes attributes) {
+                if (!directory.equals(root) && isHiddenName(directory.getFileName().toString())) {
+                    return FileVisitResult.SKIP_SUBTREE;
+                }
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attributes) throws IOException {
+                if (attributes.isSymbolicLink() || Files.isSymbolicLink(file)) {
+                    throw new IOException("Pack directory contains a symbolic link: " + file);
+                }
+                if (!attributes.isRegularFile()) {
+                    throw new IOException("Pack directory contains an unsupported entry: " + file);
+                }
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult visitFileFailed(Path file, IOException failure) throws IOException {
+                throw new IOException("Unable to inspect pack entry: " + file, failure);
+            }
+        });
+    }
+
+    public static boolean containsHiddenPathSegment(Path root, Path candidate) {
+        if (root == null || candidate == null) {
+            return true;
+        }
+        Path normalizedRoot = root.toAbsolutePath().normalize();
+        Path normalizedCandidate = candidate.toAbsolutePath().normalize();
+        if (!normalizedCandidate.startsWith(normalizedRoot)) {
+            return true;
+        }
+        Path relative = normalizedRoot.relativize(normalizedCandidate);
+        for (Path segment : relative) {
+            if (isHiddenName(segment.toString())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public static boolean isHiddenName(String name) {
+        return name != null && name.startsWith(".");
+    }
 }

core/src/main/java/art/arcane/iris/core/pack/PackDownloader.java

@@ -23,18 +23,33 @@ import art.arcane.iris.core.localization.PackDownloadMessages;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.util.common.misc.WebCache;
-import art.arcane.volmlib.util.io.IO;
 import art.arcane.volmlib.util.localization.MessageArgument;
-import org.zeroturnaround.zip.ZipUtil;
 import org.zeroturnaround.zip.commons.FileUtils;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Consumer;
 import java.util.regex.Pattern;
+import java.util.stream.Stream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
 
 public final class PackDownloader {
     private static final String DEFAULT_OVERWORLD_PACK = "overworld";
@@ -43,7 +58,14 @@ public final class PackDownloader {
     private static final Pattern GITHUB_REPOSITORY = Pattern.compile("[A-Za-z0-9_.-]+/[A-Za-z0-9_.-]+");
     private static final Pattern GITHUB_REF = Pattern.compile("[A-Za-z0-9][A-Za-z0-9._/-]*");
     private static final Pattern COMMIT_SHA = Pattern.compile("[0-9a-fA-F]{40}");
-    private static final ConcurrentHashMap<String, Object> DOWNLOAD_LOCKS = new ConcurrentHashMap<>();
+    private static final Pattern PACK_KEY = Pattern.compile("[a-z0-9_-]+");
+    private static final ArchiveLimits ARCHIVE_LIMITS = new ArchiveLimits(
+            512L * 1024L * 1024L,
+            100_000,
+            2L * 1024L * 1024L * 1024L,
+            256L * 1024L * 1024L
+    );
+    private static final ConcurrentHashMap<String, DownloadLock> DOWNLOAD_LOCKS = new ConcurrentHashMap<>();
 
     private PackDownloader() {
     }
@@ -63,15 +85,37 @@ public final class PackDownloader {
      * partial import (an interrupted copy) and counts as absent so it can be replaced.
      */
     public static boolean isPackPresent(File packsFolder, String key) {
-        if (packsFolder == null || key == null || key.isBlank()) {
+        if (packsFolder == null || !isSafePackKey(key)) {
+            return false;
+        }
+        Path packsRoot = packsFolder.toPath().toAbsolutePath().normalize();
+        File resolvedPack = PackDirectoryResolver.resolveExisting(packsFolder, key);
+        if (resolvedPack == null) {
+            return false;
+        }
+        try {
+            PackDirectoryResolver.requireSafePackTree(resolvedPack);
+        } catch (IOException exception) {
+            return false;
+        }
+        Path pack = resolvedPack.toPath().toAbsolutePath().normalize();
+        Path dimensions = pack.resolve("dimensions");
+        if (!Objects.equals(pack.getParent(), packsRoot)
+                || Files.isSymbolicLink(dimensions)
+                || !Files.isDirectory(pack)
+                || !Files.isDirectory(dimensions, LinkOption.NOFOLLOW_LINKS)) {
+            return false;
+        }
+        try (Stream<Path> entries = Files.list(dimensions)) {
+            return entries.anyMatch(path -> path.getFileName().toString().endsWith(".json")
+                    && !Files.isSymbolicLink(path)
+                    && Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS));
+        } catch (IOException exception) {
             return false;
         }
-        File[] dimensions = new File(new File(packsFolder, key), "dimensions")
-                .listFiles((File dir, String name) -> name.endsWith(".json"));
-        return dimensions != null && dimensions.length > 0;
     }
 
-    public static String downloadDefaultOverworld(File packsFolder, boolean forceOverwrite, Consumer<String> feedback) throws IOException {
+    public static PackInstallResult downloadDefaultOverworld(File packsFolder, boolean forceOverwrite, Consumer<String> feedback) throws IOException {
         return download(packsFolder, DEFAULT_OVERWORLD_REPOSITORY, defaultOverworldReleaseUrl(), forceOverwrite, true, DEFAULT_OVERWORLD_PACK, feedback);
     }
 
@@ -82,136 +126,414 @@ public final class PackDownloader {
      * per-repo lock keeps concurrent startup triggers (async default-pack install racing world
      * resolution) from downloading the same archive twice.
      */
-    public static String download(File packsFolder, String repo, String ref, boolean forceOverwrite, boolean directUrl, String expectedKey, Consumer<String> feedback) throws IOException {
-        // Lock on the destination pack key when known: concurrent triggers for the same pack can
-        // arrive with different refs (release URL vs listing branch) and must still serialize.
-        String lockKey = expectedKey != null && !expectedKey.isBlank() ? "key:" + expectedKey : "ref:" + repo + "|" + ref;
-        Object lock = DOWNLOAD_LOCKS.computeIfAbsent(lockKey, key -> new Object());
-        synchronized (lock) {
-            if (!forceOverwrite && isPackPresent(packsFolder, expectedKey)) {
-                feedback.accept(IrisLanguage.plain(PackDownloadMessages.ALREADY_INSTALLED, MessageArgument.untrusted("key", expectedKey)));
-                return expectedKey;
-            }
-            return downloadLocked(packsFolder, repo, ref, forceOverwrite, directUrl, feedback);
+    public static PackInstallResult download(File packsFolder, String repo, String ref, boolean forceOverwrite, boolean directUrl, String expectedKey, Consumer<String> feedback) throws IOException {
+        Objects.requireNonNull(packsFolder, "packsFolder");
+        Consumer<String> output = feedback == null ? ignored -> {
+        } : feedback;
+        if (expectedKey != null && !expectedKey.isBlank() && !isSafePackKey(expectedKey)) {
+            throw new IllegalArgumentException("Invalid expected pack key '" + expectedKey + "'");
         }
+        String lockKey = expectedKey != null && !expectedKey.isBlank() ? "key:" + expectedKey : "ref:" + repo + "|" + ref;
+        return withDownloadLock(lockKey, () -> {
+            if (!forceOverwrite && isPackPresent(packsFolder, expectedKey)) {
+                sendFeedback(output, IrisLanguage.plain(PackDownloadMessages.ALREADY_INSTALLED, MessageArgument.untrusted("key", expectedKey)));
+                return new PackInstallResult(expectedKey, false, false);
+            }
+            return downloadLocked(packsFolder, repo, ref, forceOverwrite, directUrl, expectedKey, lockKey, output);
+        });
     }
 
-    private static String downloadLocked(File packsFolder, String repo, String ref, boolean forceOverwrite, boolean directUrl, Consumer<String> feedback) throws IOException {
+    private static PackInstallResult downloadLocked(File packsFolder, String repo, String ref, boolean forceOverwrite, boolean directUrl,
+                                                    String expectedKey, String heldLockKey, Consumer<String> feedback) throws IOException {
         String url = directUrl ? ref : resolveGithubArchiveUrl(repo, ref);
-        feedback.accept(IrisLanguage.plain(PackDownloadMessages.DOWNLOADING, MessageArgument.untrusted("url", url)) + " "); //The extra space stops a bug in adventure API from repeating the last letter of the URL
-        File zip = WebCache.getNonCachedFile("pack-" + repo, url);
+        sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.DOWNLOADING, MessageArgument.untrusted("url", url)) + " ");
+        File zip = WebCache.getNonCachedFile("pack-" + repo, url, ARCHIVE_LIMITS.maxArchiveBytes());
         File temp = WebCache.getTemp();
         File work = new File(temp, "dl-" + UUID.randomUUID());
 
-        if (zip == null || !zip.exists()) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.FAILED_TO_FIND, MessageArgument.untrusted("url", url)));
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.CHECK_REPOSITORY_AND_BRANCH));
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.EXAMPLE_COMMAND));
-            return null;
-        }
-        feedback.accept(IrisLanguage.plain(PackDownloadMessages.UNPACKING, MessageArgument.untrusted("repository", repo)));
         try {
-            ZipUtil.unpack(zip, work);
-        } catch (Throwable e) {
-            IrisLogging.reportError(e);
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.UNPACK_FAILED));
-            IO.delete(work);
-            return null;
-        }
-        File dir = null;
-        File[] zipFiles = work.listFiles();
-
-        if (zipFiles == null) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.NO_EXTRACTED_FILES));
-            return null;
-        }
-
-        try {
-            dir = zipFiles.length > 1 ? work : zipFiles[0].isDirectory() ? zipFiles[0] : null;
-        } catch (NullPointerException e) {
-            IrisLogging.reportError(e);
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.HOME_DIRECTORY_ERROR));
-            return null;
-        }
-
-        if (dir == null) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.INVALID_ARCHIVE_FORMAT));
-            return null;
-        }
-
-        IrisData data = IrisData.get(dir);
-        String[] dimensions = data.getDimensionLoader().getPossibleKeys();
-
-        if (dimensions == null || dimensions.length == 0) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.NO_DIMENSION_FILE));
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.CHECK_GITHUB));
-            return null;
-        }
-
-        if (dimensions.length != 1) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.ONE_DIMENSION_REQUIRED));
-            return null;
-        }
-
-        IrisDimension d = data.getDimensionLoader().load(dimensions[0]);
-        data.close();
-
-        if (d == null) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.INVALID_DIMENSION));
-            return null;
-        }
-
-        String key = d.getLoadKey();
-        feedback.accept(IrisLanguage.plain(PackDownloadMessages.IMPORTING, MessageArgument.untrusted("name", d.getName()), MessageArgument.untrusted("key", key)));
-        File packEntry = new File(packsFolder, key);
-        File[] staleStaging = packsFolder.listFiles((File parent, String name) -> name.startsWith(key + ".importing-"));
-        if (staleStaging != null) {
-            for (File stale : staleStaging) {
-                IO.delete(stale);
-            }
-        }
-
-        if (forceOverwrite) {
-            IO.delete(packEntry);
-        }
-
-        if (IrisData.loadAnyDimension(key, null) != null) {
-            feedback.accept(IrisLanguage.plain(PackDownloadMessages.DIMENSION_KEY_CONFLICT, MessageArgument.untrusted("key", key)));
-            return null;
-        }
-
-        File[] existingEntries = packEntry.listFiles();
-        if (packEntry.exists() && existingEntries != null && existingEntries.length > 0) {
-            if (isPackPresent(packsFolder, key)) {
-                feedback.accept(IrisLanguage.plain(PackDownloadMessages.PACK_KEY_CONFLICT, MessageArgument.untrusted("key", key)));
+            if (zip == null || !zip.exists()) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.FAILED_TO_FIND, MessageArgument.untrusted("url", url)));
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.CHECK_REPOSITORY_AND_BRANCH));
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.EXAMPLE_COMMAND));
                 return null;
             }
-            // Non-empty but no dimension file: a partial import from an interrupted copy.
-            // Replace it instead of refusing forever.
-            IrisLogging.warn("Replacing partial pack folder " + packEntry.getPath() + " (no dimension files found).");
-            IO.delete(packEntry);
-        }
-
-        // Stage inside the packs folder and move into place so packs/<key> is never partial:
-        // an interrupted copy previously left a folder without dimensions/, which then blocked
-        // every future import as a key conflict.
-        File staging = new File(packsFolder, key + ".importing-" + UUID.randomUUID());
-        try {
-            FileUtils.copyDirectory(dir, staging);
-            if (!staging.renameTo(packEntry)) {
-                throw new IOException("Unable to move imported pack into place: " + packEntry.getPath());
+            sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.UNPACKING, MessageArgument.untrusted("repository", repo)));
+            try {
+                unpackArchive(zip.toPath(), work.toPath(), ARCHIVE_LIMITS);
+            } catch (IOException exception) {
+                IrisLogging.reportError(exception);
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.UNPACK_FAILED));
+                return null;
             }
-        } catch (IOException | RuntimeException e) {
-            IO.delete(staging);
-            throw e;
+            File[] zipFiles = work.listFiles();
+            if (zipFiles == null) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.NO_EXTRACTED_FILES));
+                return null;
+            }
+            File directory;
+            try {
+                directory = zipFiles.length > 1 ? work : zipFiles[0].isDirectory() ? zipFiles[0] : null;
+            } catch (NullPointerException exception) {
+                IrisLogging.reportError(exception);
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.HOME_DIRECTORY_ERROR));
+                return null;
+            }
+            if (directory == null) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.INVALID_ARCHIVE_FORMAT));
+                return null;
+            }
+            return installExtractedPack(packsFolder, directory, forceOverwrite, expectedKey, heldLockKey, feedback);
+        } finally {
+            deleteDirectory(work);
+        }
+    }
+
+    static PackInstallResult installExtractedPack(File packsFolder, File extractedPack, boolean forceOverwrite,
+                                                  String expectedKey, Consumer<String> feedback) throws IOException {
+        Objects.requireNonNull(packsFolder, "packsFolder");
+        Objects.requireNonNull(extractedPack, "extractedPack");
+        Consumer<String> output = feedback == null ? ignored -> {
+        } : feedback;
+        return installExtractedPack(packsFolder, extractedPack, forceOverwrite, expectedKey, null, output);
+    }
+
+    private static PackInstallResult installExtractedPack(File packsFolder, File extractedPack, boolean forceOverwrite,
+                                                          String expectedKey, String heldLockKey, Consumer<String> feedback) throws IOException {
+        if (expectedKey != null && !expectedKey.isBlank() && !isSafePackKey(expectedKey)) {
+            throw new IllegalArgumentException("Invalid expected pack key '" + expectedKey + "'");
+        }
+        Path packsRoot = packsFolder.toPath().toAbsolutePath().normalize();
+        Files.createDirectories(packsRoot);
+        Path staging = packsRoot.resolve(".iris-import-" + UUID.randomUUID());
+        try {
+            FileUtils.copyDirectory(extractedPack, staging.toFile());
+            PreparedPack prepared = prepareStagedPack(staging.toFile(), expectedKey, feedback);
+            if (prepared == null) {
+                return null;
+            }
+            String destinationLockKey = "key:" + prepared.key();
+            if (destinationLockKey.equals(heldLockKey)) {
+                return publishPreparedPack(packsFolder, packsRoot, staging, prepared, forceOverwrite, feedback);
+            }
+            return withDownloadLock(destinationLockKey,
+                    () -> publishPreparedPack(packsFolder, packsRoot, staging, prepared, forceOverwrite, feedback));
+        } finally {
+            deleteDirectory(staging.toFile());
+        }
+    }
+
+    private static PreparedPack prepareStagedPack(File staging, String expectedKey,
+                                                  Consumer<String> feedback) throws IOException {
+        IrisData data = IrisData.openDatapackCompiler(staging);
+        String key;
+        String name;
+        try {
+            String[] dimensions = data.getDimensionLoader().getPossibleKeys();
+            if (dimensions == null || dimensions.length == 0) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.NO_DIMENSION_FILE));
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.CHECK_GITHUB));
+                return null;
+            }
+            if (dimensions.length != 1) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.ONE_DIMENSION_REQUIRED));
+                return null;
+            }
+            IrisDimension dimension = data.getDimensionLoader().load(dimensions[0]);
+            if (dimension == null) {
+                sendFeedback(feedback, IrisLanguage.plain(PackDownloadMessages.INVALID_DIMENSION));
+                return null;
+            }
+            key = dimension.getLoadKey();
+            name = dimension.getName();
+        } finally {
+            data.close();
+        }
+        if (!isSafePackKey(key)) {
+            throw new IOException("Downloaded pack has unsafe dimension key '" + key + "'");
+        }
+        if (expectedKey != null && !expectedKey.isBlank() && !expectedKey.equals(key)) {
+            throw new IOException("Downloaded pack key '" + key + "' does not match requested key '" + expectedKey + "'");
         }
 
-        IrisData.getLoaded(packEntry)
-                .ifPresent(IrisData::hotloaded);
+        PackValidationResult stagedValidation;
+        try {
+            stagedValidation = PackValidator.validate(staging);
+        } catch (RuntimeException exception) {
+            throw new IOException("Pack validation failed before publication for '" + key + "'", exception);
+        }
+        PackValidationResult validation = new PackValidationResult(
+                key,
+                stagedValidation.getBlockingErrors(),
+                stagedValidation.getWarnings(),
+                stagedValidation.getValidatedAtMillis()
+        );
+        if (!validation.isLoadable()) {
+            sendValidationFeedback(validation, feedback);
+            return null;
+        }
+        sendFeedback(feedback, IrisLanguage.plain(
+                PackDownloadMessages.IMPORTING,
+                MessageArgument.untrusted("name", name),
+                MessageArgument.untrusted("key", key)
+        ));
+        return new PreparedPack(key, name, validation);
+    }
 
-        feedback.accept(IrisLanguage.plain(PackDownloadMessages.ACQUIRED, MessageArgument.untrusted("name", d.getName())));
-        validateDownloaded(packEntry, feedback);
-        return key;
+    private static PackInstallResult publishPreparedPack(File packsFolder, Path packsRoot, Path staging, PreparedPack prepared,
+                                                         boolean forceOverwrite, Consumer<String> feedback) throws IOException {
+        Path target = packsRoot.resolve(prepared.key()).normalize();
+        if (!Objects.equals(target.getParent(), packsRoot)) {
+            throw new IOException("Pack target escapes the packs folder: " + target);
+        }
+        if (Files.isSymbolicLink(target)) {
+            sendFeedback(feedback, "Pack '" + prepared.key() + "' is a symbolic-link source and cannot be replaced by Iris.");
+            return null;
+        }
+
+        Path conflictingPack = findConflictingPack(packsRoot, staging, target, prepared.key());
+        if (conflictingPack != null) {
+            sendFeedback(feedback, IrisLanguage.plain(
+                    PackDownloadMessages.DIMENSION_KEY_CONFLICT,
+                    MessageArgument.untrusted("key", prepared.key())
+            ));
+            return null;
+        }
+        if (!forceOverwrite && isPackPresent(packsRoot.toFile(), prepared.key())) {
+            sendFeedback(feedback, IrisLanguage.plain(
+                    PackDownloadMessages.PACK_KEY_CONFLICT,
+                    MessageArgument.untrusted("key", prepared.key())
+            ));
+            return null;
+        }
+        if (!forceOverwrite && Files.exists(target) && !isPackPresent(packsRoot.toFile(), prepared.key())) {
+            IrisLogging.warn("Replacing partial pack folder " + target + " (no dimension files found).");
+        }
+
+        Optional<IrisData> loadedData = IrisData.getLoaded(new File(packsFolder, prepared.key()));
+        if (loadedData.isEmpty()) {
+            loadedData = IrisData.getLoaded(target.toFile());
+        }
+        if (loadedData.isPresent()) {
+            sendFeedback(
+                    feedback,
+                    "Pack '" + prepared.key() + "' is active and cannot be replaced safely. Unload its worlds before retrying."
+            );
+            return null;
+        }
+        try (AtomicDirectoryPublisher.Publication publication = AtomicDirectoryPublisher.publish(staging, target)) {
+            publication.commit();
+            try {
+                publication.cleanupBackup();
+            } catch (IOException exception) {
+                IrisLogging.reportError(
+                        "Pack '" + prepared.key() + "' was published, but its transaction backup could not be cleaned.",
+                        exception
+                );
+            }
+        }
+        PackValidationRegistry.publish(prepared.validation());
+        sendValidationFeedback(prepared.validation(), feedback);
+        sendFeedback(feedback, IrisLanguage.plain(
+                PackDownloadMessages.ACQUIRED,
+                MessageArgument.untrusted("name", prepared.name())
+        ));
+        return new PackInstallResult(prepared.key(), true, false);
+    }
+
+    private static Path findConflictingPack(Path packsRoot, Path staging, Path target, String key) throws IOException {
+        Set<Path> roots = new LinkedHashSet<>();
+        roots.add(packsRoot);
+        if (IrisPlatforms.isBound()) {
+            roots.add(IrisPlatforms.get().dataFolder("packs").toPath().toAbsolutePath().normalize());
+        }
+        for (Path root : roots) {
+            if (!Files.isDirectory(root)) {
+                continue;
+            }
+            try (Stream<Path> entries = Files.list(root)) {
+                List<Path> candidates = entries.toList();
+                for (Path candidate : candidates) {
+                    Path normalized = candidate.toAbsolutePath().normalize();
+                    String candidateName = candidate.getFileName().toString();
+                    if (normalized.equals(staging)
+                            || normalized.equals(target)
+                            || PackDirectoryResolver.isHiddenName(candidateName)
+                            || !PackDirectoryResolver.isVisiblePackDirectory(candidate.toFile())) {
+                        continue;
+                    }
+                    Path dimension = candidate.resolve("dimensions").resolve(key + ".json");
+                    if (Files.isRegularFile(dimension)) {
+                        return normalized;
+                    }
+                }
+            }
+        }
+        return null;
+    }
+
+    private static boolean isSafePackKey(String key) {
+        return key != null && PACK_KEY.matcher(key).matches();
+    }
+
+    private static PackInstallResult withDownloadLock(String key, DownloadOperation operation) throws IOException {
+        DownloadLock lock = DOWNLOAD_LOCKS.compute(key, (ignored, existing) -> {
+            DownloadLock selected = existing == null ? new DownloadLock() : existing;
+            selected.references++;
+            return selected;
+        });
+        try {
+            synchronized (lock) {
+                return operation.run();
+            }
+        } finally {
+            DOWNLOAD_LOCKS.computeIfPresent(key, (ignored, existing) -> {
+                if (existing != lock) {
+                    return existing;
+                }
+                existing.references--;
+                return existing.references == 0 ? null : existing;
+            });
+        }
+    }
+
+    static int downloadLockCount() {
+        return DOWNLOAD_LOCKS.size();
+    }
+
+    static void unpackArchive(Path archive, Path destination, ArchiveLimits limits) throws IOException {
+        Path source = Objects.requireNonNull(archive, "archive").toAbsolutePath().normalize();
+        Path root = Objects.requireNonNull(destination, "destination").toAbsolutePath().normalize();
+        ArchiveLimits safety = Objects.requireNonNull(limits, "limits");
+        if (Files.isSymbolicLink(source) || !Files.isRegularFile(source, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Pack archive is missing or unsafe: " + source);
+        }
+        if (Files.size(source) > safety.maxArchiveBytes()) {
+            throw new IOException("Pack archive exceeds the compressed size limit.");
+        }
+        if (Files.exists(root, LinkOption.NOFOLLOW_LINKS) && !Files.isDirectory(root, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Pack extraction target is not a directory: " + root);
+        }
+        Files.createDirectories(root);
+        if (Files.isSymbolicLink(root)) {
+            throw new IOException("Pack extraction target is unsafe: " + root);
+        }
+
+        int entryCount = 0;
+        long expandedBytes = 0L;
+        Set<String> paths = new HashSet<>();
+        try (InputStream input = Files.newInputStream(source); ZipInputStream zip = new ZipInputStream(input)) {
+            ZipEntry entry;
+            while ((entry = zip.getNextEntry()) != null) {
+                entryCount++;
+                if (entryCount > safety.maxEntries()) {
+                    throw new IOException("Pack archive contains too many entries.");
+                }
+                String normalizedName = normalizeArchiveEntry(entry.getName());
+                String collisionKey = normalizedName.toLowerCase(Locale.ROOT);
+                if (!paths.add(collisionKey)) {
+                    throw new IOException("Pack archive contains a duplicate path: " + normalizedName);
+                }
+                Path output = root.resolve(normalizedName).normalize();
+                if (!output.startsWith(root)) {
+                    throw new IOException("Pack archive entry escapes extraction: " + entry.getName());
+                }
+                if (entry.isDirectory()) {
+                    Files.createDirectories(output);
+                    zip.closeEntry();
+                    continue;
+                }
+                long declaredSize = entry.getSize();
+                if (declaredSize > safety.maxEntryBytes()) {
+                    throw new IOException("Pack archive entry exceeds the file size limit: " + normalizedName);
+                }
+                Files.createDirectories(output.getParent());
+                long entryBytes = 0L;
+                try (OutputStream file = Files.newOutputStream(output, StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE)) {
+                    byte[] buffer = new byte[8192];
+                    int read;
+                    while ((read = zip.read(buffer)) != -1) {
+                        if (read == 0) {
+                            continue;
+                        }
+                        entryBytes += read;
+                        expandedBytes += read;
+                        if (entryBytes > safety.maxEntryBytes()) {
+                            throw new IOException("Pack archive entry exceeds the file size limit: " + normalizedName);
+                        }
+                        if (expandedBytes > safety.maxExpandedBytes()) {
+                            throw new IOException("Pack archive expands beyond the safety limit.");
+                        }
+                        file.write(buffer, 0, read);
+                    }
+                }
+                zip.closeEntry();
+            }
+        }
+        if (entryCount == 0) {
+            throw new IOException("Pack archive is empty.");
+        }
+    }
+
+    private static String normalizeArchiveEntry(String rawName) throws IOException {
+        if (rawName == null || rawName.isBlank() || rawName.indexOf('\0') >= 0
+                || rawName.startsWith("/") || rawName.startsWith("\\")) {
+            throw new IOException("Pack archive contains an invalid path.");
+        }
+        String slashNormalized = rawName.replace('\\', '/');
+        if (slashNormalized.matches("^[A-Za-z]:.*")) {
+            throw new IOException("Pack archive contains an unsafe path: " + rawName);
+        }
+        Path normalized = Path.of(slashNormalized).normalize();
+        String result = normalized.toString().replace('\\', '/');
+        if (normalized.isAbsolute() || normalized.startsWith("..") || result.isBlank() || ".".equals(result)) {
+            throw new IOException("Pack archive contains an unsafe path: " + rawName);
+        }
+        return result;
+    }
+
+    private static void deleteDirectory(File directory) {
+        try {
+            AtomicDirectoryPublisher.deleteTree(directory.toPath());
+        } catch (IOException exception) {
+            IrisLogging.reportError("Failed to clean temporary pack directory '" + directory.getPath() + "'", exception);
+        }
+    }
+
+    private static void sendFeedback(Consumer<String> feedback, String message) {
+        try {
+            feedback.accept(message);
+        } catch (RuntimeException exception) {
+            IrisLogging.reportError("Pack download feedback delivery failed", exception);
+        }
+    }
+
+    private static void sendValidationFeedback(PackValidationResult result, Consumer<String> feedback) {
+        if (!result.isLoadable()) {
+            sendFeedback(feedback, IrisLanguage.plain(
+                    PackDownloadMessages.VALIDATION_FAILED,
+                    MessageArgument.untrusted("pack", result.getPackName())
+            ));
+            for (String reason : result.getBlockingErrors()) {
+                sendFeedback(feedback, IrisLanguage.plain(
+                        PackDownloadMessages.VALIDATION_REASON,
+                        MessageArgument.untrusted("reason", reason)
+                ));
+            }
+            return;
+        }
+        if (!result.getWarnings().isEmpty()) {
+            sendFeedback(feedback, IrisLanguage.plain(
+                    PackDownloadMessages.VALIDATED_WITH_WARNINGS,
+                    MessageArgument.untrusted("pack", result.getPackName()),
+                    MessageArgument.trusted("count", result.getWarnings().size())
+            ));
+            return;
+        }
+        sendFeedback(feedback, IrisLanguage.plain(
+                PackDownloadMessages.VALIDATED,
+                MessageArgument.untrusted("pack", result.getPackName())
+        ));
     }
 
     static String resolveGithubArchiveUrl(String repo, String ref) {
@@ -229,6 +551,9 @@ public final class PackDownloader {
         if (COMMIT_SHA.matcher(ref).matches()) {
             return "https://github.com/" + repo + "/archive/" + ref + ".zip";
         }
+        if ("HEAD".equals(ref)) {
+            return "https://github.com/" + repo + "/archive/HEAD.zip";
+        }
         if (ref.startsWith("refs/") && !ref.startsWith("refs/heads/") && !ref.startsWith("refs/tags/")) {
             throw new IllegalArgumentException("Unsupported GitHub reference '" + ref + "'");
         }
@@ -269,27 +594,26 @@ public final class PackDownloader {
         }
     }
 
-    private static void validateDownloaded(File packEntry, Consumer<String> feedback) {
-        try {
-            PackValidationResult result = PackValidator.validate(packEntry);
-            PackValidationRegistry.publish(result);
+    private record PreparedPack(String key, String name, PackValidationResult validation) {
+    }
 
-            if (!result.isLoadable()) {
-                feedback.accept(IrisLanguage.plain(PackDownloadMessages.VALIDATION_FAILED, MessageArgument.untrusted("pack", result.getPackName())));
-                for (String reason : result.getBlockingErrors()) {
-                    feedback.accept(IrisLanguage.plain(PackDownloadMessages.VALIDATION_REASON, MessageArgument.untrusted("reason", reason)));
-                }
-            } else if (!result.getWarnings().isEmpty()) {
-                feedback.accept(IrisLanguage.plain(
-                        PackDownloadMessages.VALIDATED_WITH_WARNINGS,
-                        MessageArgument.untrusted("pack", result.getPackName()),
-                        MessageArgument.trusted("count", result.getWarnings().size())
-                ));
-            } else {
-                feedback.accept(IrisLanguage.plain(PackDownloadMessages.VALIDATED, MessageArgument.untrusted("pack", result.getPackName())));
+    public record PackInstallResult(String key, boolean changed, boolean restartRequired) {
+    }
+
+    record ArchiveLimits(long maxArchiveBytes, int maxEntries, long maxExpandedBytes, long maxEntryBytes) {
+        ArchiveLimits {
+            if (maxArchiveBytes < 1L || maxEntries < 1 || maxExpandedBytes < 1L || maxEntryBytes < 1L) {
+                throw new IllegalArgumentException("Archive limits must be positive.");
             }
-        } catch (Throwable e) {
-            IrisLogging.reportError("Pack validation failed for '" + packEntry.getName() + "'", e);
         }
     }
+
+    @FunctionalInterface
+    private interface DownloadOperation {
+        PackInstallResult run() throws IOException;
+    }
+
+    private static final class DownloadLock {
+        private int references;
+    }
 }

core/src/main/java/art/arcane/iris/core/pack/PackObjectSurfaceValidator.java

@@ -117,6 +117,10 @@ final class PackObjectSurfaceValidator {
     }
 
     static List<String> validateStructureGraph(File packFolder) {
+        return validateStructureGraph(packFolder, true);
+    }
+
+    static List<String> validateStructureGraph(File packFolder, boolean validateLiveRegistries) {
         List<String> blockingErrors = new ArrayList<>();
         if (packFolder == null || !packFolder.isDirectory()) {
             return blockingErrors;
@@ -131,7 +135,8 @@ final class PackObjectSurfaceValidator {
         Set<String> pieceKeys = ContentKeyValidator.deriveRegistrantKeysExact(piecesFolder);
         Set<String> objectKeys = ContentKeyValidator.deriveObjectKeysExact(objectsFolder);
 
-        PackStructurePlacementValidator.validateStructurePlacements(packFolder, structureKeys, blockingErrors);
+        PackStructurePlacementValidator.validateStructurePlacements(
+                packFolder, structureKeys, validateLiveRegistries, blockingErrors);
         PackStructurePlacementValidator.validateStructureStartPools(structuresFolder, poolKeys, blockingErrors);
         PackStructurePlacementValidator.validateJigsawPools(poolsFolder, poolKeys, pieceKeys, blockingErrors);
         PackStructurePlacementValidator.validateJigsawPieces(piecesFolder, poolKeys, objectKeys, blockingErrors);

core/src/main/java/art/arcane/iris/core/pack/PackStructurePlacementValidator.java

@@ -18,7 +18,10 @@
 
 package art.arcane.iris.core.pack;
 
+import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.iris.spi.PlatformStructureHooks;
+import art.arcane.iris.spi.PlatformStructureHooks.JigsawSourceMetadata;
 import art.arcane.volmlib.util.json.JSONArray;
 import art.arcane.volmlib.util.json.JSONObject;
 
@@ -26,22 +29,32 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Set;
 
 final class PackStructurePlacementValidator {
+    private static final Set<String> TERRAIN_ENVELOPE_MODES = Set.of(
+            "BORE", "FORCE_CARVE", "VACUUM", "ENCASE");
+
     private PackStructurePlacementValidator() {
     }
 
     static void validateStructurePlacements(File packFolder,
                                             Set<String> structureKeys,
+                                            boolean validateLiveRegistries,
                                             List<String> blockingErrors) {
-        Set<String> registeredStructures = registeredStructureKeys();
-        Set<String> registeredJigsaws = registeredJigsawKeys();
-        Set<String> registeredPools = registeredTemplatePoolKeys();
+        RegistrySnapshot registries = registrySnapshot(validateLiveRegistries, blockingErrors);
+        if (registries == null) {
+            return;
+        }
+        Map<String, String> placementIds = new HashMap<>();
+        Map<String, String> anonymousGridIdentities = new HashMap<>();
         for (String folderName : PackValidator.STRUCTURE_HOST_FOLDERS) {
             File resourceFolder = new File(packFolder, folderName);
             if (!resourceFolder.isDirectory()) {
@@ -55,22 +68,42 @@ final class PackStructurePlacementValidator {
                 if (resource == null) {
                     continue;
                 }
+                String resourceKey = PackValidationIo.deriveKey(resourceFolder, resourceFile);
+                if (PackValidator.DIMENSIONS_FOLDER.equals(folderName)) {
+                    validateImportedStructureAdjustmentEnvelopes(
+                            resourceKey, resource, registries, blockingErrors);
+                }
+                Object rawPlacements = resource.opt("structures");
                 JSONArray placements = resource.optJSONArray("structures");
                 if (placements == null) {
+                    if (resource.has("structures") && rawPlacements != JSONObject.NULL) {
+                        blockingErrors.add(resourceType + " '" + resourceKey + "'.structures must be an array.");
+                    }
                     continue;
                 }
-                String resourceKey = PackValidationIo.deriveKey(resourceFolder, resourceFile);
                 for (int placementIndex = 0; placementIndex < placements.length(); placementIndex++) {
                     JSONObject placement = placements.optJSONObject(placementIndex);
-                    if (placement == null) {
-                        continue;
-                    }
-                    JSONArray references = placement.optJSONArray("structures");
-                    JSONArray nativeStructures = placement.optJSONArray("nativeStructures");
-                    boolean hasIrisStructures = references != null && references.length() > 0;
-                    boolean hasNativeStructures = nativeStructures != null && nativeStructures.length() > 0;
                     String placementPath = resourceType + " '" + resourceKey + "' structures["
                             + placementIndex + "]";
+                    if (placement == null) {
+                        blockingErrors.add(placementPath + " must be an object.");
+                        continue;
+                    }
+                    validatePlacementConfiguration(placementPath, placement, blockingErrors);
+                    validatePlacementIdentity(
+                            placementPath, placement, placementIds, anonymousGridIdentities, blockingErrors);
+                    JSONArray references = placement.optJSONArray("structures");
+                    JSONArray nativeStructures = placement.optJSONArray("nativeStructures");
+                    if (placement.has("structures") && placement.opt("structures") != JSONObject.NULL
+                            && references == null) {
+                        blockingErrors.add(placementPath + ".structures must be an array.");
+                    }
+                    if (placement.has("nativeStructures") && placement.opt("nativeStructures") != JSONObject.NULL
+                            && nativeStructures == null) {
+                        blockingErrors.add(placementPath + ".nativeStructures must be an array.");
+                    }
+                    boolean hasIrisStructures = references != null && references.length() > 0;
+                    boolean hasNativeStructures = nativeStructures != null && nativeStructures.length() > 0;
                     if (hasIrisStructures == hasNativeStructures) {
                         blockingErrors.add(placementPath
                                 + " must declare exactly one non-empty backend: structures or nativeStructures.");
@@ -78,14 +111,24 @@ final class PackStructurePlacementValidator {
                     }
                     if (hasNativeStructures) {
                         validateNativeStructures(
-                                placementPath, placement, nativeStructures,
-                                registeredStructures, registeredJigsaws,
-                                registeredPools, blockingErrors);
+                                placementPath, nativeStructures,
+                                registries.structures(), registries.jigsaws(),
+                                registries.pools(), registries.jigsawMetadataResolver(),
+                                registries.hooks(), blockingErrors);
                         continue;
                     }
+                    Set<String> editableStructureKeys = new HashSet<>();
                     for (int referenceIndex = 0; referenceIndex < references.length(); referenceIndex++) {
                         Object rawReference = references.opt(referenceIndex);
                         if (!(rawReference instanceof String structureKey) || structureKey.isBlank()) {
+                            blockingErrors.add(placementPath + ".structures[" + referenceIndex
+                                    + "] must name a non-blank Iris structure.");
+                            continue;
+                        }
+                        String normalizedStructureKey = structureKey.trim().toLowerCase(Locale.ROOT);
+                        if (!editableStructureKeys.add(normalizedStructureKey)) {
+                            blockingErrors.add(placementPath + ".structures[" + referenceIndex
+                                    + "] duplicates Iris structure '" + structureKey + "'.");
                             continue;
                         }
                         if (!structureKeys.contains(structureKey)) {
@@ -99,66 +142,240 @@ final class PackStructurePlacementValidator {
         }
     }
 
-    private static Set<String> registeredJigsawKeys() {
+    private static RegistrySnapshot registrySnapshot(boolean validateLiveRegistries,
+                                                     List<String> blockingErrors) {
+        if (!validateLiveRegistries || !IrisPlatforms.isBound()) {
+            return new RegistrySnapshot(Set.of(), Set.of(), Set.of(), null, null);
+        }
         try {
-            List<String> registered = IrisPlatforms.get().structureHooks().jigsawStructureKeys();
-            if (registered == null || registered.isEmpty()) {
-                return Set.of();
+            PlatformStructureHooks hooks = IrisPlatforms.get().structureHooks();
+            if (hooks == null) {
+                throw new IllegalStateException("The active platform did not provide structure registry hooks");
             }
-            Set<String> keys = new HashSet<>();
-            for (String key : registered) {
-                if (key != null && !key.isBlank()) {
-                    keys.add(key.toLowerCase(Locale.ROOT));
-                }
+            Set<String> structures = normalizeRegistryKeys(
+                    hooks.structureKeys(), "structure");
+            Set<String> jigsaws = normalizeRegistryKeys(
+                    hooks.jigsawStructureKeys(), "jigsaw structure");
+            Set<String> pools = normalizeRegistryKeys(
+                    hooks.templatePoolKeys(), "template pool");
+            if (structures.isEmpty()) {
+                throw new IllegalStateException("The active structure registry is empty");
             }
-            return Set.copyOf(keys);
-        } catch (Throwable ignored) {
-            return Set.of();
+            if (jigsaws.isEmpty()) {
+                throw new IllegalStateException("The active jigsaw structure registry is empty");
+            }
+            if (pools.isEmpty()) {
+                throw new IllegalStateException("The active template pool registry is empty");
+            }
+            return new RegistrySnapshot(
+                    structures, jigsaws, pools, new JigsawMetadataResolver(hooks), hooks);
+        } catch (RuntimeException | LinkageError e) {
+            IrisLogging.reportError("Could not read the live structure registries during pack validation", e);
+            blockingErrors.add("Could not validate native structure references against the live registries: "
+                    + failureMessage(e) + ".");
+            return null;
         }
     }
 
-    private static Set<String> registeredStructureKeys() {
-        try {
-            List<String> registered = IrisPlatforms.get().structureHooks().structureKeys();
-            if (registered == null || registered.isEmpty()) {
-                return Set.of();
+    private static Set<String> normalizeRegistryKeys(List<String> registered, String registryName) {
+        if (registered == null) {
+            throw new IllegalStateException("The active " + registryName + " registry returned null");
+        }
+        Set<String> keys = new HashSet<>();
+        for (String key : registered) {
+            if (key != null && !key.isBlank()) {
+                keys.add(key.toLowerCase(Locale.ROOT));
             }
-            Set<String> keys = new HashSet<>();
-            for (String key : registered) {
-                if (key != null && !key.isBlank()) {
-                    keys.add(key.toLowerCase(Locale.ROOT));
-                }
+        }
+        return Set.copyOf(keys);
+    }
+
+    private static String failureMessage(Throwable throwable) {
+        String message = throwable.getMessage();
+        return message == null || message.isBlank() ? throwable.getClass().getSimpleName() : message;
+    }
+
+    private static void validatePlacementConfiguration(String path, JSONObject placement,
+                                                       List<String> blockingErrors) {
+        PackJsonFieldChecks.validateOptionalEnum(path, placement, "distribution",
+                Set.of("RANDOM_SPREAD", "DENSITY", "CONCENTRIC_RINGS"), blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(path, placement, "spacing", 1, 4096, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "separation", 0, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "salt", Integer.MIN_VALUE, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalDoubleRange(path, placement, "density", 0D, 1D, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "ringCount", 1, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "ringDistance", 1, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "ringSpread", 1, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "minHeight", Integer.MIN_VALUE, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path, placement, "maxHeight", Integer.MIN_VALUE, Integer.MAX_VALUE, blockingErrors);
+        PackJsonFieldChecks.validateOptionalBoolean(path, placement, "underground", blockingErrors);
+        PackJsonFieldChecks.validateOptionalBoolean(path, placement, "underwater", blockingErrors);
+        PackJsonFieldChecks.validateOptionalEnum(path, placement, "nativeSuppression",
+                Set.of("NONE", "REPLACE_SOURCE"), blockingErrors);
+
+        Integer spacing = integerValue(placement, "spacing", 32);
+        Integer separation = integerValue(placement, "separation", 8);
+        if (spacing != null && separation != null && separation >= spacing) {
+            blockingErrors.add(path + ".separation must be smaller than spacing.");
+        }
+        Integer minimumHeight = integerValue(placement, "minHeight", -2032);
+        Integer maximumHeight = integerValue(placement, "maxHeight", 2032);
+        if (minimumHeight != null && maximumHeight != null && minimumHeight > maximumHeight) {
+            blockingErrors.add(path + " has an inverted height band: minHeight must not exceed maxHeight.");
+        }
+        Integer ringCount = integerValue(placement, "ringCount", 128);
+        Integer ringDistance = integerValue(placement, "ringDistance", 32);
+        Integer ringSpread = integerValue(placement, "ringSpread", 3);
+        if (ringCount != null && ringDistance != null && ringSpread != null
+                && ringCount > 0 && ringDistance > 0 && ringSpread > 0) {
+            long ringRadius = (long) Math.ceilDiv(ringCount, ringSpread) * ringDistance;
+            if (ringRadius > Integer.MAX_VALUE) {
+                blockingErrors.add(path + " concentric ring radius exceeds the supported chunk coordinate range.");
             }
-            return Set.copyOf(keys);
-        } catch (Throwable ignored) {
-            return Set.of();
+        }
+
+        if (placement.has("placementId")) {
+            Object rawPlacementId = placement.opt("placementId");
+            if (!(rawPlacementId instanceof String placementId)) {
+                blockingErrors.add(path + ".placementId must be a string.");
+            } else if (!placementId.isEmpty() && placementId.isBlank()) {
+                blockingErrors.add(path + ".placementId must be omitted or non-blank.");
+            } else if (!placementId.equals(placementId.trim())) {
+                blockingErrors.add(path + ".placementId must not contain leading or trailing whitespace.");
+            }
+        }
+        validateStilt(path, placement, blockingErrors);
+        validateNativeTerrain(path, placement, blockingErrors);
+    }
+
+    private static void validatePlacementIdentity(String path, JSONObject placement,
+                                                  Map<String, String> placementIds,
+                                                  Map<String, String> anonymousGridIdentities,
+                                                  List<String> blockingErrors) {
+        Object rawPlacementId = placement.opt("placementId");
+        if (rawPlacementId instanceof String placementId && !placementId.isBlank()) {
+            String normalizedId = placementId.trim();
+            String existing = placementIds.putIfAbsent(normalizedId, path);
+            if (existing != null) {
+                blockingErrors.add(path + ".placementId duplicates '" + normalizedId
+                        + "' already declared by " + existing + ".");
+            }
+            return;
+        }
+        String gridIdentity = anonymousGridIdentity(placement);
+        String existing = anonymousGridIdentities.putIfAbsent(gridIdentity, path);
+        if (existing != null) {
+            blockingErrors.add(path + " duplicates an anonymous placement grid already declared by "
+                    + existing + "; give distinct placements unique placementId values.");
         }
     }
 
-    private static Set<String> registeredTemplatePoolKeys() {
-        try {
-            List<String> registered = IrisPlatforms.get().structureHooks().templatePoolKeys();
-            if (registered == null || registered.isEmpty()) {
-                return Set.of();
+    private static String anonymousGridIdentity(JSONObject placement) {
+        StringBuilder identity = new StringBuilder();
+        appendIdentity(identity, placement.optString("distribution", "RANDOM_SPREAD"));
+        appendIdentity(identity, integerValue(placement, "salt", 165745296));
+        appendIdentity(identity, integerValue(placement, "spacing", 32));
+        appendIdentity(identity, integerValue(placement, "separation", 8));
+        Object rawDensity = placement.has("density") ? placement.opt("density") : 0.02D;
+        appendIdentity(identity, rawDensity instanceof Number number
+                ? Double.doubleToLongBits(number.doubleValue()) : rawDensity);
+        appendIdentity(identity, integerValue(placement, "ringCount", 128));
+        appendIdentity(identity, integerValue(placement, "ringDistance", 32));
+        appendIdentity(identity, integerValue(placement, "ringSpread", 3));
+        appendIdentity(identity, integerValue(placement, "minHeight", -2032));
+        appendIdentity(identity, integerValue(placement, "maxHeight", 2032));
+        appendIdentity(identity, placement.opt("underground") instanceof Boolean underground && underground);
+        appendIdentity(identity, placement.opt("underwater") instanceof Boolean underwater && underwater);
+        JSONArray structures = placement.optJSONArray("structures");
+        JSONArray nativeStructures = placement.optJSONArray("nativeStructures");
+        if (structures != null && structures.length() > 0) {
+            appendIdentity(identity, "iris");
+            List<String> orderedStructures = new ArrayList<>(structures.length());
+            for (int index = 0; index < structures.length(); index++) {
+                orderedStructures.add(String.valueOf(structures.opt(index)));
             }
-            Set<String> keys = new HashSet<>();
-            for (String key : registered) {
-                if (key != null && !key.isBlank()) {
-                    keys.add(key.toLowerCase(Locale.ROOT));
+            orderedStructures.sort(String::compareTo);
+            for (String structure : orderedStructures) {
+                appendIdentity(identity, structure);
+            }
+        } else {
+            appendIdentity(identity, "native");
+            if (nativeStructures != null) {
+                List<String> orderedSources = new ArrayList<>(nativeStructures.length());
+                for (int index = 0; index < nativeStructures.length(); index++) {
+                    JSONObject source = nativeStructures.optJSONObject(index);
+                    String sourceKey = source == null ? "null" : source.optString("structure", "");
+                    Integer weight = source == null ? null : integerValue(source, "weight", 1);
+                    orderedSources.add(sourceKey.length() + ":" + sourceKey + ":" + weight);
+                }
+                orderedSources.sort(String::compareTo);
+                for (String source : orderedSources) {
+                    appendIdentity(identity, source);
                 }
             }
-            return Set.copyOf(keys);
-        } catch (Throwable ignored) {
-            return Set.of();
+        }
+        return identity.toString();
+    }
+
+    private static void appendIdentity(StringBuilder identity, Object value) {
+        String text = String.valueOf(value);
+        identity.append(text.length()).append(':').append(text).append('|');
+    }
+
+    private static void validateStilt(String path, JSONObject placement, List<String> blockingErrors) {
+        if (!placement.has("stilt") || placement.opt("stilt") == JSONObject.NULL) {
+            return;
+        }
+        JSONObject stilt = placement.optJSONObject("stilt");
+        if (stilt == null) {
+            blockingErrors.add(path + ".stilt must be an object.");
+            return;
+        }
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path + ".stilt", stilt, "maxDepth", 1, 4064, blockingErrors);
+        PackJsonFieldChecks.validateOptionalIntegerRange(
+                path + ".stilt", stilt, "spacing", 1, 64, blockingErrors);
+        PackJsonFieldChecks.validateOptionalBoolean(
+                path + ".stilt", stilt, "supportNonOccluding", blockingErrors);
+        if (stilt.has("palette") && stilt.opt("palette") != JSONObject.NULL
+                && stilt.optJSONObject("palette") == null) {
+            blockingErrors.add(path + ".stilt.palette must be an object.");
         }
     }
 
-    private static void validateNativeStructures(String placementPath, JSONObject placement,
+    private static Integer integerValue(JSONObject object, String field, int defaultValue) {
+        if (!object.has(field)) {
+            return defaultValue;
+        }
+        Object rawValue = object.opt(field);
+        if (!(rawValue instanceof Number number)) {
+            return null;
+        }
+        double doubleValue = number.doubleValue();
+        if (!Double.isFinite(doubleValue) || Math.rint(doubleValue) != doubleValue
+                || doubleValue < Integer.MIN_VALUE || doubleValue > Integer.MAX_VALUE) {
+            return null;
+        }
+        return number.intValue();
+    }
+
+    private static void validateNativeStructures(String placementPath,
                                                  JSONArray nativeStructures,
                                                  Set<String> registeredStructures,
                                                  Set<String> registeredJigsaws,
                                                  Set<String> registeredPools,
+                                                 JigsawMetadataResolver jigsawMetadataResolver,
+                                                 PlatformStructureHooks hooks,
                                                  List<String> blockingErrors) {
+        Set<String> sourceKeys = new HashSet<>();
+        long totalWeight = 0L;
         for (int sourceIndex = 0; sourceIndex < nativeStructures.length(); sourceIndex++) {
             String sourcePath = placementPath + ".nativeStructures[" + sourceIndex + "]";
             JSONObject source = nativeStructures.optJSONObject(sourceIndex);
@@ -174,22 +391,199 @@ final class PackStructurePlacementValidator {
                 blockingErrors.add(sourcePath + ".structure '" + structureKey
                         + "' is not a registered structure.");
             }
+            if (!structureKey.isEmpty() && !sourceKeys.add(structureKey.toLowerCase(Locale.ROOT))) {
+                blockingErrors.add(sourcePath + ".structure duplicates native source '" + structureKey + "'.");
+            }
             Integer weight = PackLootValidator.lootInteger(source, "weight", 1, sourcePath, blockingErrors);
             PackLootValidator.requireMinimum(sourcePath + ".weight", weight, 1, blockingErrors);
+            if (weight != null && weight > 0) {
+                totalWeight += weight;
+            }
+            String normalizedStructureKey = structureKey.toLowerCase(Locale.ROOT);
+            boolean registeredJigsaw = registeredJigsaws.contains(normalizedStructureKey);
             JSONObject jigsaw = source.optJSONObject("jigsaw");
             if (source.has("jigsaw") && source.opt("jigsaw") != JSONObject.NULL && jigsaw == null) {
                 blockingErrors.add(sourcePath + ".jigsaw must be an object.");
             } else if (jigsaw != null) {
-                if (!registeredJigsaws.isEmpty()
-                        && !registeredJigsaws.contains(structureKey.toLowerCase(Locale.ROOT))) {
+                if (!registeredJigsaws.isEmpty() && !registeredJigsaw) {
                     blockingErrors.add(sourcePath
                             + ".jigsaw requires a registered jigsaw structure.");
                 }
                 validateJigsawAssembly(
                         sourcePath + ".jigsaw", jigsaw, registeredPools, blockingErrors);
             }
+            JigsawSourceMetadata sourceMetadata = registeredJigsaw
+                    ? resolveJigsawMetadata(sourcePath, normalizedStructureKey,
+                    jigsawMetadataResolver, blockingErrors)
+                    : null;
+            if (registeredJigsaw && sourceMetadata == null) {
+                continue;
+            }
+            if (registeredJigsaw || jigsaw != null) {
+                validateReferenceEnvelope(
+                        sourcePath, normalizedStructureKey, jigsaw,
+                        sourceMetadata, hooks, blockingErrors);
+            }
         }
-        validateNativeTerrain(placementPath, placement, blockingErrors);
+        if (totalWeight > Integer.MAX_VALUE) {
+            blockingErrors.add(placementPath + ".nativeStructures total weight exceeds "
+                    + Integer.MAX_VALUE + ".");
+        }
+    }
+
+    private static void validateReferenceEnvelope(String sourcePath, String structureKey,
+                                                  JSONObject jigsaw, JigsawSourceMetadata sourceMetadata,
+                                                  PlatformStructureHooks hooks,
+                                                  List<String> blockingErrors) {
+        boolean overriddenDistance = jigsaw != null && jigsaw.has("maxDistanceHorizontal");
+        Integer maximumDistance = overriddenDistance
+                ? integerValue(jigsaw, "maxDistanceHorizontal", -1)
+                : sourceMetadata == null ? null : sourceMetadata.maxDistanceHorizontal();
+        if (maximumDistance == null || maximumDistance < 0) {
+            return;
+        }
+        Integer startElementSpan = effectiveStartElementSpan(
+                sourcePath, structureKey, jigsaw, sourceMetadata, hooks, blockingErrors);
+        if (startElementSpan == null) {
+            return;
+        }
+        long assemblySpan = Math.max(maximumDistance, startElementSpan);
+        if (assemblySpan > 128L) {
+            String distancePath = overriddenDistance
+                    ? ".jigsaw.maxDistanceHorizontal" : " registered jigsaw source max-distance";
+            blockingErrors.add(sourcePath + distancePath + " and its actual structure content"
+                    + " (" + startElementSpan + "-block maximum start element and "
+                    + maximumDistance + "-block maximum assembly distance) must not exceed Minecraft's"
+                    + " 128-block (8-chunk) structure reference range.");
+        }
+    }
+
+    private static Integer effectiveStartElementSpan(String sourcePath, String structureKey,
+                                                     JSONObject jigsaw,
+                                                     JigsawSourceMetadata sourceMetadata,
+                                                     PlatformStructureHooks hooks,
+                                                     List<String> blockingErrors) {
+        int sourceSpan = sourceMetadata == null ? 0 : sourceMetadata.maxStartElementHorizontalSpan();
+        if (jigsaw == null || !jigsaw.has("startPool")) {
+            return sourceSpan;
+        }
+        String startPool = jigsaw.optString("startPool", "").trim();
+        if (startPool.isEmpty() || hooks == null) {
+            return sourceSpan;
+        }
+        try {
+            int resolvedSpan = hooks.jigsawStartPoolHorizontalSpan(structureKey, startPool);
+            if (resolvedSpan < 0) {
+                throw new IllegalStateException("negative horizontal span " + resolvedSpan);
+            }
+            return resolvedSpan;
+        } catch (RuntimeException | LinkageError error) {
+            IrisLogging.reportError("Could not resolve the effective native jigsaw start-pool span", error);
+            blockingErrors.add(sourcePath + ".jigsaw.startPool '" + startPool
+                    + "' could not resolve a bounded live horizontal span: "
+                    + failureMessage(error) + ".");
+            return null;
+        }
+    }
+
+    private static void validateImportedStructureAdjustmentEnvelopes(
+            String dimensionKey, JSONObject dimension, RegistrySnapshot registries,
+            List<String> blockingErrors) {
+        JSONObject policy = dimension.optJSONObject("importedStructures");
+        if (policy == null) {
+            return;
+        }
+        JSONArray adjustments = policy.optJSONArray("adjustments");
+        if (adjustments == null) {
+            return;
+        }
+        List<String> orderedStructureKeys = new ArrayList<>(registries.structures());
+        orderedStructureKeys.sort(String::compareTo);
+        Map<String, EffectiveTerrainAdjustment> effective = new HashMap<>();
+        for (int adjustmentIndex = 0; adjustmentIndex < adjustments.length(); adjustmentIndex++) {
+            JSONObject adjustment = adjustments.optJSONObject(adjustmentIndex);
+            if (adjustment == null || adjustment.optJSONObject("terrain") == null) {
+                continue;
+            }
+            JSONArray matches = adjustment.optJSONArray("match");
+            if (matches == null || matches.length() == 0) {
+                continue;
+            }
+            String path = "Dimension '" + dimensionKey
+                    + "' importedStructures.adjustments[" + adjustmentIndex + "]";
+            for (String structureKey : orderedStructureKeys) {
+                if (matchesStructure(matches, structureKey)) {
+                    effective.put(structureKey, new EffectiveTerrainAdjustment(path, adjustment));
+                }
+            }
+        }
+        for (String structureKey : orderedStructureKeys) {
+            EffectiveTerrainAdjustment adjustment = effective.get(structureKey);
+            if (adjustment == null) {
+                continue;
+            }
+            JSONObject terrain = adjustment.adjustment().optJSONObject("terrain");
+            if (terrain == null || !TERRAIN_ENVELOPE_MODES.contains(
+                    terrain.optString("mode", "SOURCE").toUpperCase(Locale.ROOT))) {
+                continue;
+            }
+            String sourcePath = adjustment.path() + " matched registered structure '"
+                    + structureKey + "'";
+            if (registries.jigsaws().contains(structureKey)) {
+                JigsawSourceMetadata metadata = resolveJigsawMetadata(
+                        sourcePath, structureKey,
+                        registries.jigsawMetadataResolver(), blockingErrors);
+                if (metadata == null) {
+                    continue;
+                }
+                validateReferenceEnvelope(
+                        sourcePath, structureKey, null, metadata,
+                        registries.hooks(), blockingErrors);
+            }
+        }
+    }
+
+    private static boolean matchesStructure(JSONArray matches, String structureKey) {
+        for (int matchIndex = 0; matchIndex < matches.length(); matchIndex++) {
+            Object rawPattern = matches.opt(matchIndex);
+            if (rawPattern instanceof String pattern
+                    && matchesStructurePattern(pattern, structureKey)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static JigsawSourceMetadata resolveJigsawMetadata(
+            String sourcePath, String structureKey,
+            JigsawMetadataResolver resolver, List<String> blockingErrors) {
+        if (resolver == null) {
+            return null;
+        }
+        MetadataResolution resolution = resolver.resolve(structureKey);
+        if (resolution.metadata() != null) {
+            return resolution.metadata();
+        }
+        blockingErrors.add(sourcePath + " could not resolve live metadata for registered jigsaw source '"
+                + structureKey + "': " + resolution.failure() + ".");
+        return null;
+    }
+
+    private static boolean matchesStructurePattern(String pattern, String structureKey) {
+        String normalizedPattern = pattern == null ? "" : pattern.trim().toLowerCase(Locale.ROOT);
+        String normalizedKey = structureKey == null ? "" : structureKey.trim().toLowerCase(Locale.ROOT);
+        if (normalizedPattern.isEmpty() || !normalizedKey.startsWith(normalizedPattern)) {
+            return false;
+        }
+        if (normalizedKey.length() == normalizedPattern.length()) {
+            return true;
+        }
+        char patternEnd = normalizedPattern.charAt(normalizedPattern.length() - 1);
+        if (patternEnd == ':' || patternEnd == '/' || patternEnd == '_') {
+            return true;
+        }
+        char boundary = normalizedKey.charAt(normalizedPattern.length());
+        return boundary == '/' || boundary == '_';
     }
 
     private static void validateJigsawAssembly(String path, JSONObject assembly,
@@ -234,6 +628,8 @@ final class PackStructurePlacementValidator {
         }
         PackJsonFieldChecks.validateOptionalEnum(path + ".terrain", terrain, "mode",
                 Set.of("SOURCE", "PRESERVE", "BORE", "FORCE_CARVE", "VACUUM", "ENCASE"), blockingErrors);
+        PackJsonFieldChecks.validateOptionalEnum(path + ".terrain", terrain, "shape",
+                Set.of("BOX", "ROUNDED", "ERODED"), blockingErrors);
         PackJsonFieldChecks.validateOptionalIntegerRange(path + ".terrain", terrain,
                 "horizontalPadding", 0, 128, blockingErrors);
         PackJsonFieldChecks.validateOptionalIntegerRange(path + ".terrain", terrain,
@@ -386,4 +782,48 @@ final class PackStructurePlacementValidator {
             default -> "Resource";
         };
     }
+
+    private record RegistrySnapshot(Set<String> structures, Set<String> jigsaws, Set<String> pools,
+                                    JigsawMetadataResolver jigsawMetadataResolver,
+                                    PlatformStructureHooks hooks) {
+    }
+
+    private static final class JigsawMetadataResolver {
+        private final PlatformStructureHooks hooks;
+        private final Map<String, MetadataResolution> resolutions = new HashMap<>();
+
+        private JigsawMetadataResolver(PlatformStructureHooks hooks) {
+            this.hooks = hooks;
+        }
+
+        private MetadataResolution resolve(String structureKey) {
+            MetadataResolution cached = resolutions.get(structureKey);
+            if (cached != null) {
+                return cached;
+            }
+            MetadataResolution resolved;
+            try {
+                JigsawSourceMetadata metadata = hooks.jigsawSourceMetadata(structureKey);
+                if (metadata == null) {
+                    throw new IllegalStateException(
+                            "The active structure registry returned null jigsaw metadata for '"
+                                    + structureKey + "'");
+                }
+                resolved = new MetadataResolution(metadata, null);
+            } catch (RuntimeException | LinkageError error) {
+                IrisLogging.reportError(
+                        "Could not resolve live jigsaw metadata for registered structure '"
+                                + structureKey + "' during pack validation", error);
+                resolved = new MetadataResolution(null, failureMessage(error));
+            }
+            resolutions.put(structureKey, resolved);
+            return resolved;
+        }
+    }
+
+    private record MetadataResolution(JigsawSourceMetadata metadata, String failure) {
+    }
+
+    private record EffectiveTerrainAdjustment(String path, JSONObject adjustment) {
+    }
 }

core/src/main/java/art/arcane/iris/core/pack/PackValidator.java

@@ -45,6 +45,14 @@ public final class PackValidator {
     }
 
     public static PackValidationResult validate(File packFolder) {
+        return validate(packFolder, true);
+    }
+
+    public static PackValidationResult validateForDatapackBootstrap(File packFolder) {
+        return validate(packFolder, false);
+    }
+
+    private static PackValidationResult validate(File packFolder, boolean validateLiveRegistries) {
         String packName = packFolder == null ? "<unknown>" : packFolder.getName();
         List<String> blockingErrors = new ArrayList<>();
         List<String> warnings = new ArrayList<>();
@@ -72,7 +80,8 @@ public final class PackValidator {
         blockingErrors.addAll(PackObjectSurfaceValidator.validateRemovedWorldgenFields(packFolder));
         blockingErrors.addAll(PackObjectSurfaceValidator.validateObjectSurfaceSupport(packFolder));
         blockingErrors.addAll(PackObjectSurfaceValidator.validateUnsupportedStructureTransforms(packFolder));
-        blockingErrors.addAll(PackObjectSurfaceValidator.validateStructureGraph(packFolder));
+        blockingErrors.addAll(PackObjectSurfaceValidator.validateStructureGraph(
+                packFolder, validateLiveRegistries));
         StructureGraphPackValidator.Validation compiledStructures =
                 StructureGraphPackValidator.validate(
                         packFolder.toPath(), PackObjectSurfaceValidator.collectPlacedStructureKeys(packFolder));

core/src/main/java/art/arcane/iris/core/project/IrisProjectCopier.java

@@ -18,52 +18,213 @@
 
 package art.arcane.iris.core.project;
 
+import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.volmlib.util.format.Form;
 import art.arcane.volmlib.util.io.IO;
 import art.arcane.volmlib.util.json.JSONObject;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.FileAlreadyExistsException;
 import java.nio.file.Files;
+import java.nio.file.LinkOption;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.Comparator;
+import java.util.Objects;
 import java.util.stream.Stream;
 
 public final class IrisProjectCopier {
     private IrisProjectCopier() {
     }
 
-    public static void copyProject(File sourcePack, File targetPack, String sourceKey, String targetKey) throws IOException {
-        Path source = sourcePack.toPath();
-        try (Stream<Path> walk = Files.walk(source)) {
-            for (Path path : walk.sorted(Comparator.naturalOrder()).toList()) {
-                String relative = source.relativize(path).toString();
-                if (relative.isEmpty() || relative.equals(".git") || relative.startsWith(".git" + File.separator) || relative.endsWith(".code-workspace")) {
-                    continue;
-                }
-                Path destination = targetPack.toPath().resolve(relative);
-                if (Files.isDirectory(path)) {
-                    Files.createDirectories(destination);
-                } else {
-                    Files.createDirectories(destination.getParent());
-                    Files.copy(path, destination, StandardCopyOption.REPLACE_EXISTING);
-                }
-            }
-        }
+    public static void copyProject(File sourcePack, File targetWorkspace, String sourceKey, String targetKey) throws IOException {
+        copyProject(sourcePack, targetWorkspace, sourceKey, targetKey, (source, target) -> {
+        });
+    }
 
-        File oldDimension = new File(targetPack, "dimensions/" + sourceKey + ".json");
-        File newDimension = new File(targetPack, "dimensions/" + targetKey + ".json");
-        if (oldDimension.isFile() && !oldDimension.equals(newDimension)) {
-            Files.copy(oldDimension.toPath(), newDimension.toPath(), StandardCopyOption.REPLACE_EXISTING);
-            Files.delete(oldDimension.toPath());
-        }
-        if (newDimension.isFile()) {
-            JSONObject json = new JSONObject(IO.readAll(newDimension));
-            if (json.has("name")) {
-                json.put("name", Form.capitalizeWords(targetKey.replaceAll("\\Q-\\E", " ")));
-                IO.writeAll(newDimension, json.toString(4));
+    static void copyProject(
+            File sourcePack,
+            File targetWorkspace,
+            String sourceKey,
+            String targetKey,
+            CopyHook copyHook
+    ) throws IOException {
+        String validatedSourceKey = requireSafeKey(sourceKey, "source");
+        String validatedTargetKey = requireSafeKey(targetKey, "target");
+        Path source = requireSafeSource(
+                Objects.requireNonNull(sourcePack, "sourcePack").toPath().toAbsolutePath().normalize(),
+                validatedSourceKey
+        );
+        Path workspace = requireTargetWorkspace(targetWorkspace);
+        Path target = workspace.resolve(validatedTargetKey).normalize();
+        requireAvailableTarget(target, workspace, validatedTargetKey);
+
+        Path stage = Files.createTempDirectory(workspace, "." + validatedTargetKey + ".importing-");
+        boolean published = false;
+        Throwable operationFailure = null;
+        try {
+            copyTree(source, stage, Objects.requireNonNull(copyHook, "copyHook"));
+            transformDimension(stage, validatedSourceKey, validatedTargetKey);
+            requireAvailableTarget(target, workspace, validatedTargetKey);
+            publish(stage, target);
+            published = true;
+        } catch (IOException | RuntimeException | Error e) {
+            operationFailure = e;
+            throw e;
+        } finally {
+            if (!published) {
+                try {
+                    deleteTree(stage);
+                } catch (IOException cleanupFailure) {
+                    if (operationFailure != null) {
+                        operationFailure.addSuppressed(cleanupFailure);
+                    } else {
+                        throw cleanupFailure;
+                    }
+                }
             }
         }
     }
+
+    private static String requireSafeKey(String value, String purpose) throws IOException {
+        if (value == null || value.isBlank()) {
+            throw new IOException("Project " + purpose + " key cannot be empty.");
+        }
+
+        Path key;
+        try {
+            key = Path.of(value);
+        } catch (RuntimeException e) {
+            throw new IOException("Invalid project " + purpose + " key: " + value, e);
+        }
+        if (key.isAbsolute()
+                || key.getNameCount() != 1
+                || !key.normalize().equals(key)
+                || ".".equals(value)
+                || "..".equals(value)
+                || value.indexOf('/') >= 0
+                || value.indexOf('\\') >= 0) {
+            throw new IOException("Invalid project " + purpose + " key: " + value);
+        }
+        return value;
+    }
+
+    private static Path requireTargetWorkspace(File targetWorkspace) throws IOException {
+        Path workspace = Objects.requireNonNull(targetWorkspace, "targetWorkspace").toPath().toAbsolutePath().normalize();
+        if (Files.isSymbolicLink(workspace)
+                || !Files.isDirectory(workspace, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Project workspace is missing or unsafe: " + workspace);
+        }
+        return workspace;
+    }
+
+    private static Path requireSafeSource(Path source, String sourceKey) throws IOException {
+        if (!Files.isDirectory(source)) {
+            throw new IOException("Source project is missing or unsafe: " + source);
+        }
+        PackDirectoryResolver.requireSafePackTree(source.toFile());
+        Path resolvedSource = source.toRealPath();
+
+        Path dimension = resolvedSource.resolve("dimensions").resolve(sourceKey + ".json").normalize();
+        if (!dimension.startsWith(resolvedSource)
+                || Files.isSymbolicLink(dimension)
+                || !Files.isRegularFile(dimension, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Source project dimension is missing or unsafe: " + dimension);
+        }
+        return resolvedSource;
+    }
+
+    private static void requireAvailableTarget(Path target, Path workspace, String targetKey) throws IOException {
+        if (!workspace.equals(target.getParent()) || !targetKey.equals(target.getFileName().toString())) {
+            throw new IOException("Target project must be a direct child of the workspace: " + target);
+        }
+        if (Files.exists(target, LinkOption.NOFOLLOW_LINKS) || Files.isSymbolicLink(target)) {
+            throw new FileAlreadyExistsException(target.toString());
+        }
+    }
+
+    private static void copyTree(Path source, Path stage, CopyHook copyHook) throws IOException {
+        try (Stream<Path> walk = Files.walk(source)) {
+            for (Path path : walk.sorted(Comparator.naturalOrder()).toList()) {
+                Path relative = source.relativize(path);
+                if (relative.toString().isEmpty() || shouldSkip(relative)) {
+                    continue;
+                }
+                if (Files.isSymbolicLink(path)) {
+                    throw new IOException("Source project contains a symbolic link: " + path);
+                }
+
+                Path destination = stage.resolve(relative).normalize();
+                if (!destination.startsWith(stage)) {
+                    throw new IOException("Source project entry escapes staging: " + relative);
+                }
+                copyHook.beforeCopy(path, destination);
+                if (Files.isDirectory(path, LinkOption.NOFOLLOW_LINKS)) {
+                    Files.createDirectories(destination);
+                } else if (Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS)) {
+                    Files.createDirectories(destination.getParent());
+                    Files.copy(path, destination);
+                } else {
+                    throw new IOException("Source project contains an unsupported entry: " + path);
+                }
+            }
+        }
+    }
+
+    private static boolean shouldSkip(Path relative) {
+        return ".git".equals(relative.getName(0).toString())
+                || relative.getFileName().toString().endsWith(".code-workspace");
+    }
+
+    private static void transformDimension(Path stage, String sourceKey, String targetKey) throws IOException {
+        Path oldDimension = stage.resolve("dimensions").resolve(sourceKey + ".json");
+        Path newDimension = stage.resolve("dimensions").resolve(targetKey + ".json");
+        if (!oldDimension.equals(newDimension)) {
+            Files.move(oldDimension, newDimension);
+        }
+
+        JSONObject json = new JSONObject(IO.readAll(newDimension.toFile()));
+        if (json.has("name")) {
+            json.put("name", Form.capitalizeWords(targetKey.replace('-', ' ')));
+            IO.writeAll(newDimension.toFile(), json.toString(4));
+        }
+    }
+
+    private static void publish(Path stage, Path target) throws IOException {
+        try {
+            Files.move(stage, target, StandardCopyOption.ATOMIC_MOVE);
+        } catch (AtomicMoveNotSupportedException e) {
+            Files.move(stage, target);
+        }
+    }
+
+    private static void deleteTree(Path root) throws IOException {
+        if (!Files.exists(root, LinkOption.NOFOLLOW_LINKS)) {
+            return;
+        }
+        try (Stream<Path> walk = Files.walk(root)) {
+            IOException failure = null;
+            for (Path path : walk.sorted(Comparator.reverseOrder()).toList()) {
+                try {
+                    Files.deleteIfExists(path);
+                } catch (IOException e) {
+                    if (failure == null) {
+                        failure = e;
+                    } else {
+                        failure.addSuppressed(e);
+                    }
+                }
+            }
+            if (failure != null) {
+                throw failure;
+            }
+        }
+    }
+
+    @FunctionalInterface
+    interface CopyHook {
+        void beforeCopy(Path source, Path target) throws IOException;
+    }
 }

core/src/main/java/art/arcane/iris/core/project/SchemaBuilder.java

@@ -536,7 +536,7 @@ public class SchemaBuilder {
                 } else if (SchemaKeyedTypes.isKeyed(k.getType())) {
                     fancyType = addEnum(k.getType(), prop, description, SchemaKeyedTypes.values(k.getType()), Function.identity());
                 } else if (k.getType().isEnum()) {
-                    fancyType = addEnum(k.getType(), prop, description, k.getType().getEnumConstants(), o -> ((Enum<?>) o).name());
+                    fancyType = addEnum(k.getType(), prop, description, enumNames(k.getType()), Function.identity());
                 }
             }
             case "object" -> {
@@ -738,7 +738,7 @@ public class SchemaBuilder {
                             } else if (SchemaKeyedTypes.isKeyed(t.type())) {
                                 fancyType = addEnumList(prop, description, t, SchemaKeyedTypes.values(t.type()), Function.identity());
                             } else if (t.type().isEnum()) {
-                                fancyType = addEnumList(prop, description, t, t.type().getEnumConstants(), o -> ((Enum<?>) o).name());
+                                fancyType = addEnumList(prop, description, t, enumNames(t.type()), Function.identity());
                             }
                         }
                     }
@@ -851,6 +851,22 @@ public class SchemaBuilder {
         return "List of " + s + "s";
     }
 
+    private static String[] enumNames(Class<?> enumType) {
+        try {
+            Object[] constants = enumType.getEnumConstants();
+            String[] names = new String[constants.length];
+            for (int index = 0; index < constants.length; index++) {
+                names[index] = ((Enum<?>) constants[index]).name();
+            }
+            return names;
+        } catch (LinkageError error) {
+            return Arrays.stream(enumType.getDeclaredFields())
+                    .filter(Field::isEnumConstant)
+                    .map(Field::getName)
+                    .toArray(String[]::new);
+        }
+    }
+
     @NotNull
     private <T> String addEnum(Class<?> type, JSONObject prop, KList<String> description, T[] values, Function<T, String> function) {
         JSONArray a = new JSONArray();

core/src/main/java/art/arcane/iris/core/runtime/StudioOpenCoordinator.java

@@ -2,9 +2,13 @@ package art.arcane.iris.core.runtime;
 
 import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
 import art.arcane.iris.core.IrisWorldStorage;
+import art.arcane.iris.core.ServerConfigurator;
+import art.arcane.iris.core.lifecycle.LifecycleOperationCoordinator;
+import art.arcane.iris.core.link.MultiverseCoreLink;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.core.lifecycle.WorldLifecycleService;
+import art.arcane.iris.core.pack.AtomicDirectoryPublisher;
 import art.arcane.iris.core.project.IrisProject;
 import art.arcane.iris.core.project.IrisCodeWorkspace;
 import art.arcane.iris.core.tools.IrisCreator;
@@ -14,7 +18,6 @@ import art.arcane.iris.util.common.plugin.VolmitSender;
 import art.arcane.iris.util.common.scheduling.J;
 import art.arcane.volmlib.util.exceptions.IrisException;
 import art.arcane.volmlib.util.bukkit.WorldIdentity;
-import art.arcane.volmlib.util.io.IO;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.World;
@@ -22,17 +25,27 @@ import org.bukkit.entity.Player;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
+import java.util.function.Supplier;
 
 public final class StudioOpenCoordinator {
+    private static final long STUDIO_CLOSE_TIMEOUT_SECONDS = 120L;
     private static volatile StudioOpenCoordinator instance;
 
     private StudioOpenCoordinator() {
@@ -61,31 +74,20 @@ public final class StudioOpenCoordinator {
     }
 
     public CompletableFuture<StudioCloseResult> closeProject(IrisProject project) {
-        CompletableFuture<StudioCloseResult> future = new CompletableFuture<>();
-        J.aBukkit(() -> future.complete(executeClose(project)));
-        return future;
-    }
-
-    private StudioCloseResult executeClose(IrisProject project) {
         if (project == null) {
-            return new StudioCloseResult(null, true, true, false, null);
+            return CompletableFuture.completedFuture(new StudioCloseResult(null, true, true, false, null));
         }
 
         PlatformChunkGenerator provider = project.getActiveProvider();
         if (provider == null) {
-            return new StudioCloseResult(null, true, true, false, null);
+            return CompletableFuture.completedFuture(new StudioCloseResult(null, true, true, false, null));
         }
 
         World world = BukkitWorldBinding.world(provider.getTarget().getWorld());
         String worldName = world == null
                 ? IrisWorldStorage.logicalName(WorldIdentity.parse(provider.getTarget().getWorld().identity()))
                 : IrisWorldStorage.logicalName(world);
-        try {
-            return closeWorld(provider, worldName, world, true, project);
-        } catch (Throwable e) {
-            project.setActiveProvider(null);
-            return new StudioCloseResult(worldName, false, false, false, e);
-        }
+        return closeWorldCoordinated(provider, worldName, world, true, project);
     }
 
     private void executeOpen(StudioOpenRequest request, CompletableFuture<StudioOpenResult> future) {
@@ -200,7 +202,16 @@ public final class StudioOpenCoordinator {
             if (!request.retainOnFailure()) {
                 try {
                     updateStage(request, "cleanup", 1.00D);
-                    closeWorld(provider, request.worldName(), world, true, request.project());
+                    StudioCloseResult cleanupResult = closeWorldCoordinated(
+                            provider,
+                            request.worldName(),
+                            world,
+                            true,
+                            request.project()
+                    ).get(45L, TimeUnit.SECONDS);
+                    if (cleanupResult.failureCause() != null) {
+                        throw cleanupResult.failureCause();
+                    }
                 } catch (Throwable cleanupError) {
                     IrisLogging.reportError("Studio cleanup failed for world \"" + request.worldName() + "\".", cleanupError);
                 }
@@ -240,164 +251,344 @@ public final class StudioOpenCoordinator {
         return loaded;
     }
 
-    private StudioCloseResult closeWorld(
+    private CompletableFuture<StudioCloseResult> closeWorldCoordinated(
             PlatformChunkGenerator provider,
             String worldName,
             World world,
             boolean deleteFolder,
             IrisProject project
     ) {
-        Throwable failure = null;
-        boolean unloadCompletedLive = world == null || !isWorldFamilyLoaded(worldName);
-        boolean folderDeletionCompletedLive = !deleteFolder;
-        boolean startupCleanupQueued = false;
-        CompletableFuture<Void> closeFuture = CompletableFuture.completedFuture(null);
-
-        if (world != null) {
-            try {
-                evacuatePlayers(world);
-            } catch (Throwable e) {
-                failure = e;
-            }
+        String operationTarget = worldName == null || worldName.isBlank() ? "unknown-studio-world" : worldName;
+        LifecycleOperationCoordinator.Lease lease;
+        try {
+            lease = LifecycleOperationCoordinator.get().acquire(
+                    LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
+                    LifecycleOperationCoordinator.OperationKind.STUDIO_CLOSE,
+                    operationTarget
+            );
+        } catch (Throwable failure) {
+            boolean queued = deleteFolder && queueStartupCleanup(worldName, failure);
+            return CompletableFuture.completedFuture(new StudioCloseResult(
+                    worldName,
+                    false,
+                    false,
+                    queued,
+                    failure
+            ));
         }
 
+        CompletableFuture<StudioCloseResult> closeFuture;
+        try {
+            closeFuture = closeWorldReserved(provider, worldName, world, deleteFolder, project);
+        } catch (Throwable failure) {
+            boolean queued = deleteFolder && queueStartupCleanup(worldName, failure);
+            closeFuture = CompletableFuture.completedFuture(new StudioCloseResult(
+                    worldName,
+                    false,
+                    false,
+                    queued,
+                    failure
+            ));
+        }
+        return closeFuture.whenComplete((result, throwable) -> lease.close());
+    }
+
+    private CompletableFuture<StudioCloseResult> closeWorldReserved(
+            PlatformChunkGenerator provider,
+            String worldName,
+            World world,
+            boolean deleteFolder,
+            IrisProject project
+    ) {
+        AtomicBoolean unloadConfirmed = new AtomicBoolean(false);
+        AtomicBoolean folderDeleted = new AtomicBoolean(!deleteFolder);
+        AtomicBoolean terminalTimeout = new AtomicBoolean(false);
         if (world != null) {
             IrisToolbelt.beginWorldMaintenance(world, "studio-close", true);
         }
 
-        try {
-            if (project != null) {
-                project.setActiveProvider(null);
-            }
-            if (provider != null) {
-                closeFuture = provider.closeAsync();
-            }
-
-            if (worldName != null && !worldName.isBlank()) {
-                requestWorldFamilyUnload(worldName);
-            }
-
-            if (worldName != null && !worldName.isBlank()) {
-                long unloadDeadline = System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(20L);
-                CompletableFuture<Void> unloadFuture = waitForWorldFamilyUnload(worldName, unloadDeadline);
-                try {
-                    unloadFuture.get(Math.max(1000L, unloadDeadline - System.currentTimeMillis()), TimeUnit.MILLISECONDS);
-                    unloadCompletedLive = true;
-                } catch (TimeoutException e) {
-                    unloadCompletedLive = !isWorldFamilyLoaded(worldName);
-                } catch (Throwable e) {
-                    failure = failure == null ? unwrapFailure(e) : failure;
-                }
-            }
-
-            try {
-                closeFuture.get(20L, TimeUnit.SECONDS);
-            } catch (Throwable e) {
-                Throwable cause = unwrapFailure(e);
-                if (failure == null) {
-                    failure = cause;
-                }
-            }
-
-            if (deleteFolder && worldName != null && !worldName.isBlank()) {
-                WorldFamilyDeleteResult deleteResult = deleteWorldFamily(worldName, unloadCompletedLive);
-                folderDeletionCompletedLive = deleteResult.liveDeleted();
-                startupCleanupQueued = deleteResult.startupCleanupQueued();
-            }
-        } finally {
+        CompletableFuture<Void> sequence = sequenceStudioClose(
+                () -> evacuateWorldFamily(worldName, world),
+                () -> unloadWorldFamily(worldName, world).thenRun(() -> {
+                    if (terminalTimeout.get()) {
+                        throw new CompletionException(new TimeoutException(
+                                "Studio close stopped after its terminal timeout."));
+                    }
+                    unloadConfirmed.set(true);
+                    if (project != null) {
+                        project.setActiveProvider(null);
+                    }
+                }),
+                () -> provider == null ? CompletableFuture.completedFuture(null) : provider.closeAsync(),
+                () -> deleteFolder
+                        ? deleteWorldFamily(worldName).thenRun(() -> folderDeleted.set(true))
+                        : CompletableFuture.completedFuture(null),
+                terminalTimeout::get
+        );
+        CompletableFuture<StudioCloseResult> operation = guardCloseCompletion(
+                sequence,
+                terminalTimeout,
+                worldName)
+                .thenApply(ignored -> new StudioCloseResult(
+                        worldName,
+                        true,
+                        folderDeleted.get(),
+                        false,
+                        null
+                ))
+                .exceptionally(throwable -> {
+                    Throwable failure = unwrapFailure(throwable);
+                    boolean queued = deleteFolder && queueStartupCleanup(worldName, failure);
+                    return new StudioCloseResult(
+                            worldName,
+                            unloadConfirmed.get(),
+                            folderDeleted.get(),
+                            queued,
+                            failure
+                    );
+                });
+        return operation.whenComplete((result, throwable) -> {
             if (world != null) {
                 IrisToolbelt.endWorldMaintenance(world, "studio-close");
             }
-        }
-
-        return new StudioCloseResult(worldName, unloadCompletedLive, folderDeletionCompletedLive, startupCleanupQueued, failure);
+        });
     }
 
-    private void evacuatePlayers(World world) throws Exception {
-        if (world == null) {
-            return;
+    static CompletableFuture<Void> sequenceStudioClose(
+            Supplier<CompletableFuture<Void>> evacuate,
+            Supplier<CompletableFuture<Void>> unload,
+            Supplier<CompletableFuture<Void>> closeGenerator,
+            Supplier<CompletableFuture<Void>> deleteFolders
+    ) {
+        return sequenceStudioClose(evacuate, unload, closeGenerator, deleteFolders, () -> false);
+    }
+
+    static CompletableFuture<Void> sequenceStudioClose(
+            Supplier<CompletableFuture<Void>> evacuate,
+            Supplier<CompletableFuture<Void>> unload,
+            Supplier<CompletableFuture<Void>> closeGenerator,
+            Supplier<CompletableFuture<Void>> deleteFolders,
+            BooleanSupplier terminalTimeout
+    ) {
+        return invokePhase(evacuate)
+                .thenCompose(ignored -> invokePhaseUnlessTimedOut(unload, terminalTimeout))
+                .thenCompose(ignored -> invokePhaseUnlessTimedOut(closeGenerator, terminalTimeout))
+                .thenCompose(ignored -> invokePhaseUnlessTimedOut(deleteFolders, terminalTimeout));
+    }
+
+    private static CompletableFuture<Void> invokePhase(Supplier<CompletableFuture<Void>> phase) {
+        try {
+            CompletableFuture<Void> future = phase.get();
+            if (future == null) {
+                return CompletableFuture.failedFuture(new IllegalStateException("Studio close phase returned no completion future."));
+            }
+            return future;
+        } catch (Throwable failure) {
+            return CompletableFuture.failedFuture(failure);
+        }
+    }
+
+    private static CompletableFuture<Void> invokePhaseUnlessTimedOut(
+            Supplier<CompletableFuture<Void>> phase,
+            BooleanSupplier terminalTimeout
+    ) {
+        if (terminalTimeout.getAsBoolean()) {
+            return CompletableFuture.failedFuture(new TimeoutException(
+                    "Studio close stopped after its terminal timeout."));
+        }
+        return invokePhase(phase);
+    }
+
+    private CompletableFuture<Void> guardCloseCompletion(
+            CompletableFuture<Void> source,
+            AtomicBoolean terminalTimeout,
+            String worldName
+    ) {
+        CompletableFuture<Void> guarded = new CompletableFuture<>();
+        AtomicBoolean settled = new AtomicBoolean(false);
+        source.whenComplete((ignored, throwable) -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            if (throwable == null) {
+                guarded.complete(null);
+            } else {
+                guarded.completeExceptionally(throwable);
+            }
+        });
+        CompletableFuture.delayedExecutor(STUDIO_CLOSE_TIMEOUT_SECONDS, TimeUnit.SECONDS).execute(() -> {
+            if (!settled.compareAndSet(false, true)) {
+                return;
+            }
+            terminalTimeout.set(true);
+            TimeoutException timeout = new TimeoutException(
+                    "Studio close did not settle within " + STUDIO_CLOSE_TIMEOUT_SECONDS
+                            + " seconds for \"" + worldName + "\".");
+            ServerConfigurator.restart("Studio close timed out for \"" + worldName + "\".");
+            guarded.completeExceptionally(timeout);
+        });
+        return guarded;
+    }
+
+    private CompletableFuture<Void> evacuateWorldFamily(String worldName, World primaryWorld) {
+        List<World> loadedWorlds = loadedWorldFamily(worldName, primaryWorld);
+        if (loadedWorlds.isEmpty()) {
+            return CompletableFuture.completedFuture(null);
         }
 
-        CompletableFuture<Void> future = J.sfut(() -> {
-            IrisToolbelt.evacuate(world);
+        ArrayList<CompletableFuture<Void>> evacuations = new ArrayList<>(loadedWorlds.size());
+        for (World loadedWorld : loadedWorlds) {
+            CompletableFuture<Void> evacuation = J.sfut(() -> IrisToolbelt.evacuateAsync(loadedWorld))
+                    .thenCompose(evacuationFuture -> evacuationFuture)
+                    .thenCompose(evacuated -> Boolean.TRUE.equals(evacuated)
+                            ? CompletableFuture.completedFuture(null)
+                            : CompletableFuture.failedFuture(new IllegalStateException(
+                                    "Studio player evacuation failed for \"" + loadedWorld.getName() + "\".")));
+            evacuations.add(evacuation);
+        }
+        return CompletableFuture.allOf(evacuations.toArray(CompletableFuture[]::new));
+    }
+
+    private CompletableFuture<Void> unloadWorldFamily(String worldName, World primaryWorld) {
+        List<World> loadedWorlds = loadedWorldFamily(worldName, primaryWorld);
+        ArrayList<CompletableFuture<Boolean>> unloads = new ArrayList<>(loadedWorlds.size());
+        for (World loadedWorld : loadedWorlds) {
+            CompletableFuture<Boolean> unload = J.sfut(() ->
+                            IrisServices.get(MultiverseCoreLink.class)
+                                    .removeFromConfig(loadedWorld))
+                    .thenCompose(ignored -> WorldLifecycleService.get().unloadAsync(loadedWorld, false));
+            unloads.add(unload);
+        }
+
+        return CompletableFuture.allOf(unloads.toArray(CompletableFuture[]::new)).thenApply(ignored -> {
+            for (CompletableFuture<Boolean> unload : unloads) {
+                if (!Boolean.TRUE.equals(unload.join())) {
+                    throw new CompletionException(new IllegalStateException(
+                            "Studio world family unload returned false for \"" + worldName + "\"."));
+                }
+            }
+            if (isWorldFamilyLoaded(worldName)) {
+                throw new CompletionException(new IllegalStateException(
+                        "Studio world family remained loaded after confirmed unload for \"" + worldName + "\"."));
+            }
             return null;
         });
-        if (future != null) {
-            future.get(10L, TimeUnit.SECONDS);
-        }
     }
 
-    private void requestWorldFamilyUnload(String worldName) {
+    private List<World> loadedWorldFamily(String worldName, World primaryWorld) {
+        LinkedHashSet<World> worlds = new LinkedHashSet<>();
+        if (primaryWorld != null) {
+            worlds.add(primaryWorld);
+        }
         if (worldName == null || worldName.isBlank()) {
-            return;
+            return List.copyOf(worlds);
         }
-
         for (String familyWorldName : TransientWorldCleanupSupport.worldFamilyNames(worldName)) {
-            World familyWorld = WorldIdentity.resolve(IrisWorldStorage.keyFromName(familyWorldName)).orElse(null);
-            if (familyWorld == null) {
-                continue;
-            }
-
-            IrisServices.get(art.arcane.iris.core.link.MultiverseCoreLink.class).removeFromConfig(familyWorld);
-            WorldLifecycleService.get().unload(familyWorld, false);
+            WorldIdentity.resolve(IrisWorldStorage.keyFromName(familyWorldName)).ifPresent(worlds::add);
         }
+        return List.copyOf(worlds);
     }
 
-    private WorldFamilyDeleteResult deleteWorldFamily(String worldName, boolean unloadCompletedLive) {
+    private CompletableFuture<Void> deleteWorldFamily(String worldName) {
         if (worldName == null || worldName.isBlank()) {
-            return new WorldFamilyDeleteResult(true, false);
+            return CompletableFuture.completedFuture(null);
+        }
+        if (isWorldFamilyLoaded(worldName)) {
+            return CompletableFuture.failedFuture(new IllegalStateException(
+                    "Refusing to delete a loaded studio world family for \"" + worldName + "\"."));
         }
 
-        boolean liveDeleted = true;
-        for (String familyWorldName : TransientWorldCleanupSupport.worldFamilyNames(worldName)) {
-            File folder = IrisWorldStorage.dimensionRoot(familyWorldName);
-            if (!folder.exists()) {
-                continue;
+        return CompletableFuture.runAsync(() -> {
+            for (String familyWorldName : TransientWorldCleanupSupport.worldFamilyNames(worldName)) {
+                try {
+                    if (isWorldFamilyLoaded(worldName)) {
+                        throw new IOException("Studio world family became loaded before deletion for \""
+                                + worldName + "\".");
+                    }
+                    File folder = IrisWorldStorage.requireSafeManagedDimensionRoot(
+                            IrisWorldStorage.managedKeyFromName(familyWorldName));
+                    AtomicDirectoryPublisher.deleteTree(folder.toPath());
+                } catch (IOException | IllegalArgumentException failure) {
+                    throw new CompletionException(failure);
+                }
             }
+        });
+    }
 
-            try {
-                deleteWorldFolderAsync(folder, 40).get(15L, TimeUnit.SECONDS);
-            } catch (Throwable e) {
-                liveDeleted = false;
-                IrisLogging.reportError("Studio folder deletion retries failed for \"" + folder.getAbsolutePath() + "\".", unwrapFailure(e));
-            }
-
-            if (folder.exists()) {
-                liveDeleted = false;
-            }
+    private boolean queueStartupCleanup(String worldName, Throwable failure) {
+        if (worldName == null || worldName.isBlank()) {
+            return false;
         }
-
-        if (liveDeleted) {
-            return new WorldFamilyDeleteResult(true, false);
-        }
-
         try {
-            IrisServices.get(WorldDeletionQueue.class).queueForStartupDeletion(Collections.singleton(worldName));
-            return new WorldFamilyDeleteResult(false, true);
-        } catch (IOException e) {
-            if (unloadCompletedLive) {
-                IrisLogging.reportError("Failed to queue deferred deletion for world \"" + worldName + "\".", e);
+            IrisServices.get(WorldDeletionQueue.class).queueFamilyForStartupDeletion(Collections.singleton(worldName));
+            return true;
+        } catch (Throwable queueFailure) {
+            if (failure != null) {
+                failure.addSuppressed(queueFailure);
             }
-            return new WorldFamilyDeleteResult(false, false);
+            IrisLogging.reportError("Failed to queue deferred deletion for world \"" + worldName + "\".", queueFailure);
+            return false;
         }
     }
 
     private void cleanupStaleTransientWorlds(String worldName) {
-        LinkedHashSet<String> staleWorldNames = TransientWorldCleanupSupport.collectTransientStudioWorldNames(IrisWorldStorage.levelRoot());
+        LinkedHashSet<String> staleWorldNames = collectSafeTransientWorldNames();
         String requestedBaseName = TransientWorldCleanupSupport.transientStudioBaseWorldName(worldName);
         if (requestedBaseName != null) {
             staleWorldNames.add(requestedBaseName);
         }
 
         for (String staleWorldName : staleWorldNames) {
-            if (WorldIdentity.resolve(IrisWorldStorage.keyFromName(staleWorldName)).isPresent()) {
-                continue;
+            try {
+                StudioCloseResult cleanupResult = closeWorldCoordinated(
+                        null,
+                        staleWorldName,
+                        null,
+                        true,
+                        null
+                ).get(30L, TimeUnit.SECONDS);
+                if (cleanupResult.failureCause() != null) {
+                    IrisLogging.reportError("Stale studio world cleanup failed for \"" + staleWorldName + "\".", cleanupResult.failureCause());
+                }
+            } catch (Throwable failure) {
+                IrisLogging.reportError("Stale studio world cleanup failed for \"" + staleWorldName + "\".", unwrapFailure(failure));
             }
-
-            deleteWorldFamily(staleWorldName, true);
         }
     }
 
+    private LinkedHashSet<String> collectSafeTransientWorldNames() {
+        LinkedHashSet<String> worldNames = new LinkedHashSet<>();
+        Path irisNamespace = IrisWorldStorage.levelRoot()
+                .toPath()
+                .toAbsolutePath()
+                .normalize()
+                .resolve("dimensions")
+                .resolve("iris");
+        if (!Files.exists(irisNamespace, LinkOption.NOFOLLOW_LINKS)) {
+            return worldNames;
+        }
+        if (Files.isSymbolicLink(irisNamespace) || !Files.isDirectory(irisNamespace, LinkOption.NOFOLLOW_LINKS)) {
+            IrisLogging.warn("Skipping stale studio cleanup because Iris dimension storage is unsafe: " + irisNamespace);
+            return worldNames;
+        }
+
+        try (DirectoryStream<Path> children = Files.newDirectoryStream(irisNamespace)) {
+            for (Path child : children) {
+                if (Files.isSymbolicLink(child) || !Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS)) {
+                    continue;
+                }
+                String transientName = TransientWorldCleanupSupport.transientStudioBaseWorldName(
+                        child.getFileName().toString());
+                if (transientName != null) {
+                    worldNames.add(transientName);
+                }
+            }
+        } catch (IOException failure) {
+            IrisLogging.reportError("Failed to inspect stale studio worlds in \"" + irisNamespace + "\".", failure);
+        }
+        return worldNames;
+    }
+
     private void updateStage(StudioOpenRequest request, String stage, double progress) {
         if (request.progressConsumer() != null) {
             request.progressConsumer().accept(new StudioOpenProgress(progress, stage));
@@ -419,37 +610,6 @@ public final class StudioOpenCoordinator {
         };
     }
 
-    private CompletableFuture<Void> waitForWorldFamilyUnload(String worldName, long deadline) {
-        if (worldName == null || !isWorldFamilyLoaded(worldName) || System.currentTimeMillis() >= deadline) {
-            return CompletableFuture.completedFuture(null);
-        }
-
-        return delayFuture(100L).thenCompose(ignored -> waitForWorldFamilyUnload(worldName, deadline));
-    }
-
-    private CompletableFuture<Void> deleteWorldFolderAsync(File folder, int attemptsRemaining) {
-        if (folder == null || !folder.exists()) {
-            return CompletableFuture.completedFuture(null);
-        }
-
-        IO.delete(folder);
-        if (!folder.exists()) {
-            return CompletableFuture.completedFuture(null);
-        }
-
-        if (attemptsRemaining <= 1) {
-            return CompletableFuture.failedFuture(new IllegalStateException("World folder still exists after deletion retries: " + folder.getAbsolutePath()));
-        }
-
-        return delayFuture(250L).thenCompose(ignored -> deleteWorldFolderAsync(folder, attemptsRemaining - 1));
-    }
-
-    private CompletableFuture<Void> delayFuture(long delayMillis) {
-        long safeDelay = Math.max(0L, delayMillis);
-        return CompletableFuture.runAsync(() -> {
-        }, CompletableFuture.delayedExecutor(safeDelay, TimeUnit.MILLISECONDS));
-    }
-
     private Throwable unwrapFailure(Throwable throwable) {
         Throwable cursor = throwable;
         while (cursor instanceof CompletionException || cursor instanceof ExecutionException) {
@@ -538,7 +698,4 @@ public final class StudioOpenCoordinator {
             return failureCause == null;
         }
     }
-
-    private record WorldFamilyDeleteResult(boolean liveDeleted, boolean startupCleanupQueued) {
-    }
 }