d

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

@@ -5,9 +5,12 @@ import com.mojang.serialization.MapCodec;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.engine.data.cache.AtomicCache;
 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.object.IrisBiome;
 import art.arcane.iris.engine.object.IrisBiomeCustom;
 import art.arcane.iris.engine.object.IrisDimension;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.volmlib.util.math.RNG;
 import net.minecraft.core.Holder;
@@ -148,17 +151,26 @@ public class CustomBiomeSource extends BiomeSource {
     }
 
     Set<Holder<Biome>> possibleStructureBiomes() {
-        ensureCachesCurrent();
-        World world = BukkitWorldBinding.world(engine.getWorld());
-        if (world == null) {
-            throw new IllegalStateException("Iris biome source has no bound Bukkit world");
+        GenerationSessionLease lease = tryAcquireGenerationLease("bukkit_possible_biomes");
+        if (lease == null) {
+            throw new IllegalStateException("Iris possible biome lookup was rejected during an engine transition");
+        }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isRuntimeAvailable()) {
+                throw new IllegalStateException("Iris possible biome lookup has no active engine runtime");
+            }
+            ensureCachesCurrent();
+            World world = BukkitWorldBinding.world(engine.getWorld());
+            if (world == null) {
+                throw new IllegalStateException("Iris biome source has no bound Bukkit world");
+            }
+            Registry<Biome> customRegistry = ((RegistryAccess) getFor(
+                    RegistryAccess.Frozen.class, ((CraftServer) Bukkit.getServer()).getHandle().getServer()))
+                    .lookup(Registries.BIOME).orElse(null);
+            Registry<Biome> worldRegistry = ((CraftWorld) world).getHandle().registryAccess()
+                    .lookup(Registries.BIOME).orElse(null);
+            return Set.copyOf(getAllBiomes(customRegistry, worldRegistry, engine));
         }
-        Registry<Biome> customRegistry = ((RegistryAccess) getFor(
-                RegistryAccess.Frozen.class, ((CraftServer) Bukkit.getServer()).getHandle().getServer()))
-                .lookup(Registries.BIOME).orElse(null);
-        Registry<Biome> worldRegistry = ((CraftWorld) world).getHandle().registryAccess()
-                .lookup(Registries.BIOME).orElse(null);
-        return Set.copyOf(getAllBiomes(customRegistry, worldRegistry, engine));
     }
 
     private KMap<String, Holder<Biome>> fillCustomBiomes(Registry<Biome> customRegistry, Engine engine, Holder<Biome> fallback) {
@@ -212,11 +224,20 @@ public class CustomBiomeSource extends BiomeSource {
     }
 
     Holder<Biome> getVanillaSpawnBiome(Holder<Biome> biome) {
-        ensureCachesCurrent();
         if (biome == null) {
             return null;
         }
-        return vanillaSpawnBiomes.get(biome.value());
+        GenerationSessionLease lease = tryAcquireGenerationLease("bukkit_spawn_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris spawn biome lookup was rejected during an engine transition");
+        }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isRuntimeAvailable()) {
+                throw new IllegalStateException("Iris spawn biome lookup has no active engine runtime");
+            }
+            ensureCachesCurrent();
+            return vanillaSpawnBiomes.get(biome.value());
+        }
     }
 
     private RegistryAccess registry() {
@@ -230,51 +251,69 @@ public class CustomBiomeSource extends BiomeSource {
 
     @Override
     public Holder<Biome> getNoiseBiome(int x, int y, int z, Climate.Sampler sampler) {
-        ensureCachesCurrent();
-        if (isGuaranteedSurfaceBiome(y)) {
-            return getSurfaceStructureBiomeHolder(x, z);
+        GenerationSessionLease lease = tryAcquireGenerationLease("bukkit_structure_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris structure biome lookup was rejected during an engine transition");
         }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isRuntimeAvailable()) {
+                throw new IllegalStateException("Iris structure biome lookup has no active engine runtime");
+            }
+            ensureCachesCurrent();
+            if (isGuaranteedSurfaceBiome(y)) {
+                return getSurfaceStructureBiomeHolder(x, z);
+            }
 
-        long cacheKey = packNoiseKey(x, y, z);
-        Holder<Biome> cachedHolder = structureBiomeCache.get(cacheKey);
-        if (cachedHolder != null) {
-            return cachedHolder;
+            long cacheKey = packNoiseKey(x, y, z);
+            Holder<Biome> cachedHolder = structureBiomeCache.get(cacheKey);
+            if (cachedHolder != null) {
+                return cachedHolder;
+            }
+
+            Holder<Biome> resolvedHolder = resolveStructureBiomeHolder(x, y, z);
+            Holder<Biome> existingHolder = structureBiomeCache.putIfAbsent(cacheKey, resolvedHolder);
+            if (existingHolder != null) {
+                return existingHolder;
+            }
+
+            if (structureBiomeCache.size() > NOISE_BIOME_CACHE_MAX) {
+                structureBiomeCache.clear();
+            }
+
+            return resolvedHolder;
         }
-
-        Holder<Biome> resolvedHolder = resolveStructureBiomeHolder(x, y, z);
-        Holder<Biome> existingHolder = structureBiomeCache.putIfAbsent(cacheKey, resolvedHolder);
-        if (existingHolder != null) {
-            return existingHolder;
-        }
-
-        if (structureBiomeCache.size() > NOISE_BIOME_CACHE_MAX) {
-            structureBiomeCache.clear();
-        }
-
-        return resolvedHolder;
     }
 
     @Override
     public Set<Holder<Biome>> getBiomesWithin(int x, int y, int z, int radius, Climate.Sampler sampler) {
-        ensureCachesCurrent();
-        int minQuartY = QuartPos.fromBlock(y - radius);
-        boolean monumentQuery = radius == 29
-                && y == engine.getMinHeight() + engine.getDimension().getFluidHeight();
-        if (!monumentQuery && !isGuaranteedSurfaceBiome(minQuartY)) {
-            return super.getBiomesWithin(x, y, z, radius, sampler);
+        GenerationSessionLease lease = tryAcquireGenerationLease("bukkit_biomes_within");
+        if (lease == null) {
+            throw new IllegalStateException("Iris biome radius lookup was rejected during an engine transition");
         }
-        int minQuartX = QuartPos.fromBlock(x - radius);
-        int maxQuartX = QuartPos.fromBlock(x + radius);
-        int minQuartZ = QuartPos.fromBlock(z - radius);
-        int maxQuartZ = QuartPos.fromBlock(z + radius);
-        int columns = (maxQuartX - minQuartX + 1) * (maxQuartZ - minQuartZ + 1);
-        Set<Holder<Biome>> biomes = new HashSet<>(columns);
-        for (int quartZ = minQuartZ; quartZ <= maxQuartZ; quartZ++) {
-            for (int quartX = minQuartX; quartX <= maxQuartX; quartX++) {
-                biomes.add(getSurfaceStructureBiomeHolder(quartX, quartZ));
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isRuntimeAvailable()) {
+                throw new IllegalStateException("Iris biome radius lookup has no active engine runtime");
             }
+            ensureCachesCurrent();
+            int minQuartY = QuartPos.fromBlock(y - radius);
+            boolean monumentQuery = radius == 29
+                    && y == engine.getMinHeight() + engine.getDimension().getFluidHeight();
+            if (!monumentQuery && !isGuaranteedSurfaceBiome(minQuartY)) {
+                return super.getBiomesWithin(x, y, z, radius, sampler);
+            }
+            int minQuartX = QuartPos.fromBlock(x - radius);
+            int maxQuartX = QuartPos.fromBlock(x + radius);
+            int minQuartZ = QuartPos.fromBlock(z - radius);
+            int maxQuartZ = QuartPos.fromBlock(z + radius);
+            int columns = (maxQuartX - minQuartX + 1) * (maxQuartZ - minQuartZ + 1);
+            Set<Holder<Biome>> biomes = new HashSet<>(columns);
+            for (int quartZ = minQuartZ; quartZ <= maxQuartZ; quartZ++) {
+                for (int quartX = minQuartX; quartX <= maxQuartX; quartX++) {
+                    biomes.add(getSurfaceStructureBiomeHolder(quartX, quartZ));
+                }
+            }
+            return biomes;
         }
-        return biomes;
     }
 
     private Holder<Biome> getSurfaceStructureBiomeHolder(int x, int z) {
@@ -322,24 +361,52 @@ public class CustomBiomeSource extends BiomeSource {
     }
 
     public Holder<Biome> getVisibleNoiseBiome(int x, int y, int z, Climate.Sampler sampler) {
-        ensureCachesCurrent();
-        long cacheKey = packNoiseKey(x, y, z);
-        Holder<Biome> cachedHolder = noiseBiomeCache.get(cacheKey);
-        if (cachedHolder != null) {
-            return cachedHolder;
+        GenerationSessionLease lease = tryAcquireGenerationLease("bukkit_visible_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris visible biome lookup was rejected during an engine transition");
         }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isRuntimeAvailable()) {
+                throw new IllegalStateException("Iris visible biome lookup has no active engine runtime");
+            }
+            ensureCachesCurrent();
+            long cacheKey = packNoiseKey(x, y, z);
+            Holder<Biome> cachedHolder = noiseBiomeCache.get(cacheKey);
+            if (cachedHolder != null) {
+                return cachedHolder;
+            }
 
-        Holder<Biome> resolvedHolder = resolveVisibleBiomeHolder(x, y, z);
-        Holder<Biome> existingHolder = noiseBiomeCache.putIfAbsent(cacheKey, resolvedHolder);
-        if (existingHolder != null) {
-            return existingHolder;
+            Holder<Biome> resolvedHolder = resolveVisibleBiomeHolder(x, y, z);
+            Holder<Biome> existingHolder = noiseBiomeCache.putIfAbsent(cacheKey, resolvedHolder);
+            if (existingHolder != null) {
+                return existingHolder;
+            }
+
+            if (noiseBiomeCache.size() > NOISE_BIOME_CACHE_MAX) {
+                noiseBiomeCache.clear();
+            }
+
+            return resolvedHolder;
         }
+    }
 
-        if (noiseBiomeCache.size() > NOISE_BIOME_CACHE_MAX) {
-            noiseBiomeCache.clear();
+    private GenerationSessionLease tryAcquireGenerationLease(String operation) {
+        if (engine.isClosed()) {
+            return null;
         }
+        try {
+            return engine.acquireGenerationLease(operation);
+        } catch (GenerationSessionException e) {
+            if (engine.isClosing() || e.isExpectedTeardown()) {
+                return null;
+            }
+            throw new IllegalStateException("Iris biome source could not acquire generation session for "
+                    + operation + ".", e);
+        }
+    }
 
-        return resolvedHolder;
+    private boolean isRuntimeAvailable() {
+        return !engine.isClosed() && engine.getComplex() != null;
     }
 
     private void ensureCachesCurrent() {

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

@@ -1,6 +1,8 @@
 package art.arcane.iris.core.nms.v26_2_R1;
 
 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.NativeStructureGenerationPolicy;
 import art.arcane.iris.engine.object.IrisDimension;
@@ -14,6 +16,7 @@ import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.iris.util.common.data.IrisCustomData;
 import art.arcane.iris.util.common.reflect.WrappedField;
 import art.arcane.iris.util.common.reflect.WrappedReturningMethod;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.volmlib.util.math.RNG;
 import com.mojang.datafixers.util.Pair;
 import com.mojang.serialization.MapCodec;
@@ -90,6 +93,7 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
     private final CustomBiomeSource customBiomeSource;
     private final int runtimeMinY;
     private final int runtimeHeight;
+    private final int runtimeSeaLevel;
     private final ConcurrentHashMap<SpawnTableKey, WeightedList<MobSpawnSettings.SpawnerData>> mergedSpawnTables = new ConcurrentHashMap<>();
     private volatile ReachableStructureCache reachableStructureCache;
     private volatile StructureStepCache structureStepCache;
@@ -106,17 +110,21 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
         ServerLevel level = ((CraftWorld) world).getHandle();
         this.runtimeMinY = level.getMinY();
         this.runtimeHeight = level.getHeight();
+        this.runtimeSeaLevel = runtimeMinY + engine.getDimension().getFluidHeight();
     }
 
     @Override
     public @Nullable Pair<BlockPos, Holder<Structure>> findNearestMapStructure(ServerLevel level, HolderSet<Structure> holders, BlockPos pos, int radius, boolean findUnexplored) {
-        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);
+        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);
+        }
     }
 
     private Pair<BlockPos, Holder<Structure>> findNearestIrisStructure(ServerLevel level,
@@ -231,14 +239,17 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public int getSeaLevel() {
-        return runtimeMinY + engine.getDimension().getFluidHeight();
+        return runtimeSeaLevel;
     }
 
     @Override
     public void createStructures(RegistryAccess registryAccess, ChunkGeneratorStructureState structureState, StructureManager structureManager, ChunkAccess access, StructureTemplateManager templateManager, ResourceKey<Level> levelKey) {
-        Map<Structure, StructureStart> previousStarts = new HashMap<>(access.getAllStarts());
-        super.createStructures(registryAccess, structureState, structureManager, access, templateManager, levelKey);
-        adjustGeneratedStructures(registryAccess, access, previousStarts);
+        try (GenerationSessionLease lease = requireGenerationLease("bukkit_nms_create_structures");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            Map<Structure, StructureStart> previousStarts = new HashMap<>(access.getAllStarts());
+            super.createStructures(registryAccess, structureState, structureManager, access, templateManager, levelKey);
+            adjustGeneratedStructures(registryAccess, access, previousStarts);
+        }
     }
 
     private void adjustGeneratedStructures(RegistryAccess registryAccess, ChunkAccess access, Map<Structure, StructureStart> previousStarts) {
@@ -298,8 +309,11 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public CompletableFuture<ChunkAccess> createBiomes(RandomState randomstate, Blender blender, StructureManager structuremanager, ChunkAccess ichunkaccess) {
-        ichunkaccess.fillBiomesFromNoise(customBiomeSource::getVisibleNoiseBiome, randomstate.sampler());
-        return CompletableFuture.completedFuture(ichunkaccess);
+        try (GenerationSessionLease lease = requireGenerationLease("bukkit_nms_create_biomes");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            ichunkaccess.fillBiomesFromNoise(customBiomeSource::getVisibleNoiseBiome, randomstate.sampler());
+            return CompletableFuture.completedFuture(ichunkaccess);
+        }
     }
 
     @Override
@@ -355,9 +369,12 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public void applyBiomeDecoration(WorldGenLevel generatoraccessseed, ChunkAccess ichunkaccess, StructureManager structuremanager, boolean vanilla) {
-        addVanillaDecorations(generatoraccessseed, ichunkaccess, structuremanager);
-        placeVanillaStructures(generatoraccessseed, ichunkaccess, structuremanager);
-        delegate.applyBiomeDecoration(generatoraccessseed, ichunkaccess, structuremanager, false);
+        try (GenerationSessionLease lease = requireGenerationLease("bukkit_nms_biome_decoration");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            addVanillaDecorations(generatoraccessseed, ichunkaccess, structuremanager);
+            placeVanillaStructures(generatoraccessseed, ichunkaccess, structuremanager);
+            delegate.applyBiomeDecoration(generatoraccessseed, ichunkaccess, structuremanager, false);
+        }
     }
 
     private void placeVanillaStructures(WorldGenLevel world, ChunkAccess chunk, StructureManager structureManager) {
@@ -525,29 +542,35 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public void addVanillaDecorations(WorldGenLevel level, ChunkAccess chunkAccess, StructureManager structureManager) {
-        SectionPos sectionPos = SectionPos.of(chunkAccess.getPos(), level.getMinSectionY());
-        BlockPos blockPos = sectionPos.origin();
+        try (GenerationSessionLease lease = engine.acquireGenerationLease("bukkit_nms_heightmaps");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            SectionPos sectionPos = SectionPos.of(chunkAccess.getPos(), level.getMinSectionY());
+            BlockPos blockPos = sectionPos.origin();
 
-        Heightmap surface = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
-        Heightmap ocean = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
-        Heightmap motion = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.MOTION_BLOCKING);
-        Heightmap motionNoLeaves = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES);
+            Heightmap surface = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+            Heightmap ocean = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+            Heightmap motion = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.MOTION_BLOCKING);
+            Heightmap motionNoLeaves = chunkAccess.getOrCreateHeightmapUnprimed(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES);
+            int minHeight = engine.getMinHeight();
 
-        for (int x = 0; x < 16; x++) {
-            for (int z = 0; z < 16; z++) {
-                int wX = x + blockPos.getX();
-                int wZ = z + blockPos.getZ();
+            for (int x = 0; x < 16; x++) {
+                for (int z = 0; z < 16; z++) {
+                    int wX = x + blockPos.getX();
+                    int wZ = z + blockPos.getZ();
 
-                int terrainTop = engine.getHeight(wX, wZ, false) + engine.getMinHeight() + 1;
-                int terrainNoFluid = engine.getHeight(wX, wZ, true) + engine.getMinHeight() + 1;
-                SET_HEIGHT.invoke(ocean, x, z, terrainNoFluid);
-                SET_HEIGHT.invoke(surface, x, z, terrainTop);
-                SET_HEIGHT.invoke(motion, x, z, terrainTop);
-                SET_HEIGHT.invoke(motionNoLeaves, x, z, terrainTop);
+                    int terrainTop = engine.getHeight(wX, wZ, false) + minHeight + 1;
+                    int terrainNoFluid = engine.getHeight(wX, wZ, true) + minHeight + 1;
+                    SET_HEIGHT.invoke(ocean, x, z, terrainNoFluid);
+                    SET_HEIGHT.invoke(surface, x, z, terrainTop);
+                    SET_HEIGHT.invoke(motion, x, z, terrainTop);
+                    SET_HEIGHT.invoke(motionNoLeaves, x, z, terrainTop);
+                }
             }
-        }
 
-        Heightmap.primeHeightmaps(chunkAccess, ChunkStatus.FINAL_HEIGHTMAPS);
+            Heightmap.primeHeightmaps(chunkAccess, ChunkStatus.FINAL_HEIGHTMAPS);
+        } catch (GenerationSessionException e) {
+            throw new IllegalStateException("Iris heightmap generation could not acquire its engine runtime.", e);
+        }
     }
 
     @Override
@@ -585,20 +608,44 @@ public class IrisChunkGenerator extends CustomChunkGenerator {
 
     @Override
     public int getBaseHeight(int i, int j, Heightmap.Types heightmap_type, LevelHeightAccessor levelheightaccessor, RandomState randomstate) {
-        return levelheightaccessor.getMinY() + engine.getHeight(i, j, !heightmap_type.isOpaque().test(Blocks.WATER.defaultBlockState())) + 1;
+        try (GenerationSessionLease lease = engine.acquireGenerationLease("bukkit_nms_base_height");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            return levelheightaccessor.getMinY()
+                    + engine.getHeight(i, j, !heightmap_type.isOpaque().test(Blocks.WATER.defaultBlockState()))
+                    + 1;
+        } catch (GenerationSessionException e) {
+            throw new IllegalStateException("Iris base height query could not acquire its engine runtime.", e);
+        }
     }
 
     @Override
     public NoiseColumn getBaseColumn(int i, int j, LevelHeightAccessor levelheightaccessor, RandomState randomstate) {
-        int block = engine.getHeight(i, j, true);
-        int water = engine.getHeight(i, j, false);
-        BlockState[] column = new BlockState[levelheightaccessor.getHeight()];
-        for (int k = 0; k < column.length; k++) {
-            if (k <= block) column[k] = Blocks.STONE.defaultBlockState();
-            else if (k <= water) column[k] = Blocks.WATER.defaultBlockState();
-            else column[k] = Blocks.AIR.defaultBlockState();
+        try (GenerationSessionLease lease = engine.acquireGenerationLease("bukkit_nms_base_column");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            int block = engine.getHeight(i, j, true);
+            int water = engine.getHeight(i, j, false);
+            BlockState[] column = new BlockState[levelheightaccessor.getHeight()];
+            for (int k = 0; k < column.length; k++) {
+                if (k <= block) {
+                    column[k] = Blocks.STONE.defaultBlockState();
+                } else if (k <= water) {
+                    column[k] = Blocks.WATER.defaultBlockState();
+                } else {
+                    column[k] = Blocks.AIR.defaultBlockState();
+                }
+            }
+            return new NoiseColumn(levelheightaccessor.getMinY(), column);
+        } catch (GenerationSessionException e) {
+            throw new IllegalStateException("Iris base column query could not acquire its engine runtime.", e);
+        }
+    }
+
+    private GenerationSessionLease requireGenerationLease(String operation) {
+        try {
+            return engine.acquireGenerationLease(operation);
+        } catch (GenerationSessionException exception) {
+            throw new IllegalStateException("Iris " + operation + " could not acquire its engine runtime.", exception);
         }
-        return new NoiseColumn(levelheightaccessor.getMinY(), column);
     }
 
     @Override

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

@@ -19,4 +19,21 @@ public class CustomBiomeSourceStructureContractTest {
         assertTrue(source.contains("resolution.irisBiome.getStructureDerivativeKey()"));
         assertFalse(source.contains("resolution.irisBiome.getVanillaDerivative()"));
     }
+
+    @Test
+    public void biomeRuntimeReadsAreGenerationLeased() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.customBiomeSource")));
+
+        assertTrue(source.contains("tryAcquireGenerationLease(\"bukkit_possible_biomes\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(\"bukkit_spawn_biome\")"));
+        assertTrue(source.contains("Iris spawn biome lookup was rejected during an engine transition"));
+        assertTrue(source.contains("Iris spawn biome lookup has no active engine runtime"));
+        assertTrue(source.contains("tryAcquireGenerationLease(\"bukkit_structure_biome\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(\"bukkit_biomes_within\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(\"bukkit_visible_biome\")"));
+        assertTrue(source.contains("if (engine.isClosed())"));
+        assertTrue(source.contains("engine.isClosing() || e.isExpectedTeardown()"));
+        assertTrue(source.contains("catch (GenerationSessionException e)"));
+        assertTrue(source.contains("e.isExpectedTeardown()"));
+    }
 }

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

@@ -54,4 +54,14 @@ public class IrisChunkGeneratorFailureContractTest {
                 < placement.indexOf("for (NativePlacementGroup group"));
         assertFalse(placement.contains("IrisLogging.reportError"));
     }
+
+    @Test
+    public void heightmapRuntimeReadsAreGenerationLeased() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.nmsChunkGeneratorSource")));
+
+        assertTrue(source.contains("engine.acquireGenerationLease(\"bukkit_nms_heightmaps\")"));
+        assertTrue(source.contains("engine.acquireGenerationLease(\"bukkit_nms_base_height\")"));
+        assertTrue(source.contains("engine.acquireGenerationLease(\"bukkit_nms_base_column\")"));
+        assertTrue(source.contains("catch (GenerationSessionException e)"));
+    }
 }

adapters/bukkit/plugin/build.gradle

@@ -46,4 +46,8 @@ 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.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)
+    systemProperty('iris.engineSvcSource', file('src/main/java/art/arcane/iris/core/service/IrisEngineSVC.java').absolutePath)
 }

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

@@ -55,6 +55,7 @@ import art.arcane.iris.engine.EnginePanic;
 import art.arcane.iris.engine.framework.BlockEditAccess;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.PreservationRegistry;
+import art.arcane.iris.engine.framework.TreeBlockMaterial;
 import art.arcane.iris.engine.object.IrisCompat;
 import art.arcane.iris.engine.object.IrisDimension;
 import art.arcane.iris.engine.object.IrisWorld;
@@ -634,11 +635,8 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         IrisServices.register(EngineComponentCleanup.class, (EngineComponentCleanup) BukkitPlatform::unregisterListener);
         IrisServices.register(EngineEffectsProvider.class, (EngineEffectsProvider) IrisEngineEffects::new);
         IrisServices.register(EnginePlatformHooks.class, new BukkitEnginePlatformHooks());
-        IrisServices.register(EngineWorldManagerProvider.class, (EngineWorldManagerProvider) (Engine engine) -> {
-            IrisWorldManager manager = new IrisWorldManager(engine);
-            manager.startManager();
-            return manager;
-        });
+        IrisServices.register(EngineWorldManagerProvider.class,
+                (EngineWorldManagerProvider) IrisWorldManager::new);
         IrisServices.register(art.arcane.iris.core.runtime.WorldDeletionQueue.class, (art.arcane.iris.core.runtime.WorldDeletionQueue) Iris::queueWorldDeletionOnStartup);
         settingsFile = getDataFile("settings.json");
         configHotloadEngine = new ConfigHotloadEngine(
@@ -673,6 +671,7 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
             }
             IrisToolbelt.retainMantleDataForSlice(String.class.getCanonicalName());
             IrisToolbelt.retainMantleDataForSlice(BlockData.class.getCanonicalName());
+            IrisToolbelt.retainMantleDataForSlice(TreeBlockMaterial.class.getCanonicalName());
         });
     }
 

adapters/bukkit/plugin/src/main/java/art/arcane/iris/api/tree/IrisTreeFellerService.java

@@ -0,0 +1,12 @@
+package art.arcane.iris.api.tree;
+
+import org.bukkit.block.Block;
+import org.bukkit.event.block.BlockBreakEvent;
+
+public interface IrisTreeFellerService {
+    boolean tryFell(BlockBreakEvent event, TreeFellerOptions options);
+
+    boolean isManagedBreak(BlockBreakEvent event);
+
+    boolean isTreeBlock(Block block);
+}

adapters/bukkit/plugin/src/main/java/art/arcane/iris/api/tree/TreeFellerAccess.java

@@ -0,0 +1,6 @@
+package art.arcane.iris.api.tree;
+
+public enum TreeFellerAccess {
+    STANDALONE,
+    INTEGRATION_OVERRIDE
+}

adapters/bukkit/plugin/src/main/java/art/arcane/iris/api/tree/TreeFellerOptions.java

@@ -0,0 +1,32 @@
+package art.arcane.iris.api.tree;
+
+import java.util.Objects;
+
+public record TreeFellerOptions(
+        TreeFellerAccess access,
+        int durabilityPreservationChance,
+        TreeFellerRunHooks runHooks
+) {
+    public TreeFellerOptions {
+        Objects.requireNonNull(access, "access");
+        Objects.requireNonNull(runHooks, "runHooks");
+        if (durabilityPreservationChance < 0 || durabilityPreservationChance > 100) {
+            throw new IllegalArgumentException("durabilityPreservationChance must be between 0 and 100");
+        }
+    }
+
+    public static TreeFellerOptions standalone() {
+        return new TreeFellerOptions(TreeFellerAccess.STANDALONE, 0, TreeFellerRunHooks.NONE);
+    }
+
+    public static TreeFellerOptions integrationOverride(
+            int durabilityPreservationChance,
+            TreeFellerRunHooks runHooks
+    ) {
+        return new TreeFellerOptions(
+                TreeFellerAccess.INTEGRATION_OVERRIDE,
+                durabilityPreservationChance,
+                runHooks
+        );
+    }
+}

adapters/bukkit/plugin/src/main/java/art/arcane/iris/api/tree/TreeFellerRunHooks.java

@@ -0,0 +1,30 @@
+package art.arcane.iris.api.tree;
+
+public interface TreeFellerRunHooks {
+    TreeFellerRunHooks NONE = new TreeFellerRunHooks() {
+        @Override
+        public void onActivationAccepted() {
+        }
+
+        @Override
+        public boolean reserveLogCost() {
+            return true;
+        }
+
+        @Override
+        public void commitLogCost() {
+        }
+
+        @Override
+        public void refundLogCost() {
+        }
+    };
+
+    void onActivationAccepted();
+
+    boolean reserveLogCost();
+
+    void commitLogCost();
+
+    void refundLogCost();
+}

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

@@ -80,7 +80,10 @@ public final class BukkitEnginePlatformHooks implements EnginePlatformHooks {
 
     @Override
     public void shutdownPregenerator(Engine engine) {
-        PregeneratorJob.shutdownInstance();
+        IrisWorld world = engine.getWorld();
+        if (world != null) {
+            PregeneratorJob.shutdownInstanceForWorld(world.identity());
+        }
     }
 
     @Override

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

@@ -0,0 +1,91 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.core.loader.ResourceLoader;
+import art.arcane.iris.engine.framework.MeteredCache;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.util.common.format.C;
+import art.arcane.iris.util.common.plugin.VolmitSender;
+import art.arcane.iris.util.project.stream.utility.CachedDoubleStream2D;
+import art.arcane.iris.util.project.stream.utility.CachedStream2D;
+import art.arcane.iris.util.project.stream.utility.CachedStream3D;
+import art.arcane.volmlib.util.format.Form;
+
+import java.util.List;
+
+final class IrisEngineStatus {
+    private IrisEngineStatus() {
+    }
+
+    static void send(VolmitSender sender, Snapshot snapshot) {
+        CacheSummary caches = summarizeCaches();
+        MaintenanceMetrics metrics = snapshot.metrics();
+
+        sender.sendMessage(C.DARK_PURPLE + "-------------------------");
+        sender.sendMessage(C.DARK_PURPLE + "Status:");
+        sender.sendMessage(C.DARK_PURPLE + "- Service: " + C.LIGHT_PURPLE + (snapshot.serviceRunning() ? "Running" : "Stopped"));
+        sender.sendMessage(C.DARK_PURPLE + "- Metrics: " + C.LIGHT_PURPLE + (snapshot.metricsRunning() ? "Running" : "Stopped"));
+        sender.sendMessage(C.DARK_PURPLE + "- Maintenance Period: " + C.LIGHT_PURPLE + Form.duration(snapshot.maintenancePeriodMillis()));
+        sender.sendMessage(C.DARK_PURPLE + "- Worker Parallelism: " + C.LIGHT_PURPLE + snapshot.workerParallelism());
+        sender.sendMessage(C.DARK_PURPLE + "- Active World Tasks: " + C.LIGHT_PURPLE + metrics.activeTasks());
+        sender.sendMessage(C.DARK_PURPLE + "Tectonic Plates:");
+        sender.sendMessage(C.DARK_PURPLE + "- Configured Retention: " + C.LIGHT_PURPLE + Form.duration(snapshot.retentionMillis()));
+        sender.sendMessage(C.DARK_PURPLE + "- Heap Usage: " + C.LIGHT_PURPLE + Form.pc(snapshot.heapUsage()));
+        sender.sendMessage(C.DARK_PURPLE + "- Resident: " + C.LIGHT_PURPLE + metrics.residentTectonicPlates());
+        sender.sendMessage(C.DARK_PURPLE + "- Queued: " + C.LIGHT_PURPLE + metrics.queuedTectonicPlates());
+        sender.sendMessage(C.DARK_PURPLE + "- Average Idle Duration: " + C.LIGHT_PURPLE + Form.duration(metrics.averageIdleDuration(), 2));
+        sender.sendMessage(C.DARK_PURPLE + "- Max Idle Duration: " + C.LIGHT_PURPLE + Form.duration(metrics.maxIdleDuration(), 2));
+        sender.sendMessage(C.DARK_PURPLE + "- Min Idle Duration: " + C.LIGHT_PURPLE + Form.duration(metrics.minIdleDuration(), 2));
+        sender.sendMessage(C.DARK_PURPLE + "Caches:");
+        sender.sendMessage(C.DARK_PURPLE + "- Resource: " + C.LIGHT_PURPLE + caches.sizes()[0] + " (" + caches.counts()[0] + ")");
+        sender.sendMessage(C.DARK_PURPLE + "- 2D Stream: " + C.LIGHT_PURPLE + caches.sizes()[1] + " (" + caches.counts()[1] + ")");
+        sender.sendMessage(C.DARK_PURPLE + "- 3D Stream: " + C.LIGHT_PURPLE + caches.sizes()[2] + " (" + caches.counts()[2] + ")");
+        sender.sendMessage(C.DARK_PURPLE + "- Other: " + C.LIGHT_PURPLE + caches.sizes()[3] + " (" + caches.counts()[3] + ")");
+        sender.sendMessage(C.DARK_PURPLE + "Other:");
+        sender.sendMessage(C.DARK_PURPLE + "- Iris Worlds: " + C.LIGHT_PURPLE + metrics.worlds());
+        sender.sendMessage(C.DARK_PURPLE + "- Loaded Chunks: " + C.LIGHT_PURPLE + metrics.loadedChunks());
+        sender.sendMessage(C.DARK_PURPLE + "-------------------------");
+    }
+
+    private static CacheSummary summarizeCaches() {
+        long[] sizes = new long[4];
+        long[] counts = new long[4];
+        PreservationSVC preservation = IrisServices.get(PreservationSVC.class);
+        List<MeteredCache> caches = preservation == null ? List.of() : preservation.getCaches();
+
+        for (MeteredCache cache : caches) {
+            int type = switch (cache) {
+                case ResourceLoader<?> ignored -> 0;
+                case CachedStream2D<?> ignored -> 1;
+                case CachedDoubleStream2D ignored -> 1;
+                case CachedStream3D<?> ignored -> 2;
+                default -> 3;
+            };
+            sizes[type] += cache.getSize();
+            counts[type]++;
+        }
+        return new CacheSummary(sizes, counts);
+    }
+
+    record Snapshot(boolean serviceRunning,
+                    boolean metricsRunning,
+                    long maintenancePeriodMillis,
+                    int workerParallelism,
+                    long retentionMillis,
+                    double heapUsage,
+                    MaintenanceMetrics metrics) {
+    }
+
+    record MaintenanceMetrics(long residentTectonicPlates,
+                              long queuedTectonicPlates,
+                              long loadedChunks,
+                              int worlds,
+                              int activeTasks,
+                              double averageIdleDuration,
+                              double maxIdleDuration,
+                              double minIdleDuration) {
+        static final MaintenanceMetrics EMPTY = new MaintenanceMetrics(0L, 0L, 0L, 0, 0, 0D, 0D, 0D);
+    }
+
+    private record CacheSummary(long[] sizes, long[] counts) {
+    }
+}

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

@@ -1,12 +1,14 @@
 package art.arcane.iris.core.service;
 
 import art.arcane.iris.Iris;
-import art.arcane.iris.core.gui.PregeneratorJob;
+import art.arcane.iris.engine.framework.EngineTelemetrySnapshot;
+import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.util.common.plugin.IrisService;
 import art.arcane.volmlib.integration.IntegrationHandshakeRequest;
 import art.arcane.volmlib.integration.IntegrationHandshakeResponse;
 import art.arcane.volmlib.integration.IntegrationHeartbeat;
 import art.arcane.volmlib.integration.IntegrationMetricDescriptor;
+import art.arcane.volmlib.integration.IntegrationMetricGroup;
 import art.arcane.volmlib.integration.IntegrationMetricSample;
 import art.arcane.volmlib.integration.IntegrationMetricSchema;
 import art.arcane.volmlib.integration.IntegrationProtocolNegotiator;
@@ -15,25 +17,59 @@ import art.arcane.volmlib.integration.IntegrationServiceContract;
 import org.bukkit.Bukkit;
 import org.bukkit.plugin.ServicePriority;
 
-import java.util.HashMap;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.Supplier;
 
 public class IrisIntegrationService implements IrisService, IntegrationServiceContract {
+    private static final IntegrationProtocolVersion CURRENT_PROTOCOL = new IntegrationProtocolVersion(1, 2);
     private static final Set<IntegrationProtocolVersion> SUPPORTED_PROTOCOLS = Set.of(
             new IntegrationProtocolVersion(1, 0),
-            new IntegrationProtocolVersion(1, 1)
+            new IntegrationProtocolVersion(1, 1),
+            CURRENT_PROTOCOL
     );
-
     private static final Set<String> CAPABILITIES = Set.of(
             "handshake",
             "heartbeat",
             "metrics",
-            "iris-engine-metrics"
+            "metric-groups",
+            "iris-engine-metrics",
+            "iris-world-metrics"
+    );
+    private static final Map<String, String> TIMING_KEYS = Map.ofEntries(
+            Map.entry("total", IntegrationMetricSchema.IRIS_GENERATION_TOTAL_MS),
+            Map.entry("updates", IntegrationMetricSchema.IRIS_GENERATION_UPDATES_MS),
+            Map.entry("terrain", IntegrationMetricSchema.IRIS_GENERATION_TERRAIN_MS),
+            Map.entry("biome", IntegrationMetricSchema.IRIS_GENERATION_BIOME_MS),
+            Map.entry("post", IntegrationMetricSchema.IRIS_GENERATION_POST_MS),
+            Map.entry("perfection", IntegrationMetricSchema.IRIS_GENERATION_PERFECTION_MS),
+            Map.entry("decoration", IntegrationMetricSchema.IRIS_GENERATION_DECORATION_MS),
+            Map.entry("cave", IntegrationMetricSchema.IRIS_GENERATION_CAVE_MS),
+            Map.entry("deposit", IntegrationMetricSchema.IRIS_GENERATION_DEPOSIT_MS),
+            Map.entry("carve.resolve", IntegrationMetricSchema.IRIS_GENERATION_CARVE_RESOLVE_MS),
+            Map.entry("carve.apply", IntegrationMetricSchema.IRIS_GENERATION_CARVE_APPLY_MS),
+            Map.entry("context.prefill", IntegrationMetricSchema.IRIS_GENERATION_CONTEXT_PREFILL_MS),
+            Map.entry("pregen.wait.permit", IntegrationMetricSchema.IRIS_PREGEN_WAIT_PERMIT_MS),
+            Map.entry("pregen.wait.adaptive", IntegrationMetricSchema.IRIS_PREGEN_WAIT_ADAPTIVE_MS)
     );
 
-    private volatile IntegrationProtocolVersion negotiatedProtocol = new IntegrationProtocolVersion(1, 1);
+    private final Supplier<IrisTelemetrySnapshot> telemetrySupplier;
+
+    public IrisIntegrationService() {
+        this(IrisIntegrationService::currentTelemetry);
+    }
+
+    IrisIntegrationService(Supplier<IrisTelemetrySnapshot> telemetrySupplier) {
+        this.telemetrySupplier = telemetrySupplier == null
+                ? () -> IrisTelemetrySnapshot.EMPTY
+                : telemetrySupplier;
+    }
 
     @Override
     public void onEnable() {
@@ -68,9 +104,11 @@ public class IrisIntegrationService implements IrisService, IntegrationServiceCo
 
     @Override
     public Set<IntegrationMetricDescriptor> metricDescriptors() {
-        return IntegrationMetricSchema.descriptors().stream()
-                .filter(descriptor -> descriptor.key().startsWith("iris."))
-                .collect(java.util.stream.Collectors.toSet());
+        Set<IntegrationMetricDescriptor> descriptors = new LinkedHashSet<>();
+        for (String key : IntegrationMetricSchema.irisKeys()) {
+            descriptors.add(IntegrationMetricSchema.descriptor(key));
+        }
+        return Set.copyOf(descriptors);
     }
 
     @Override
@@ -106,12 +144,11 @@ public class IrisIntegrationService implements IrisService, IntegrationServiceCo
             );
         }
 
-        negotiatedProtocol = negotiated.get();
         return new IntegrationHandshakeResponse(
                 pluginId(),
                 pluginVersion(),
                 true,
-                negotiatedProtocol,
+                negotiated.get(),
                 SUPPORTED_PROTOCOLS,
                 CAPABILITIES,
                 "ok",
@@ -121,90 +158,228 @@ public class IrisIntegrationService implements IrisService, IntegrationServiceCo
 
     @Override
     public IntegrationHeartbeat heartbeat() {
-        long now = System.currentTimeMillis();
-        return new IntegrationHeartbeat(negotiatedProtocol, true, now, "ok");
+        return new IntegrationHeartbeat(CURRENT_PROTOCOL, true, System.currentTimeMillis(), "ok");
     }
 
     @Override
     public Map<String, IntegrationMetricSample> sampleMetrics(Set<String> metricKeys) {
         Set<String> requested = metricKeys == null || metricKeys.isEmpty()
                 ? IntegrationMetricSchema.irisKeys()
-                : metricKeys;
-        long now = System.currentTimeMillis();
-        Map<String, IntegrationMetricSample> out = new HashMap<>();
+                : Set.copyOf(metricKeys);
+        IrisTelemetrySnapshot snapshot = safeSnapshot();
+        long sampledAtMs = snapshot.sampledAtMs() > 0L
+                ? snapshot.sampledAtMs()
+                : System.currentTimeMillis();
+        if (snapshot.sampledAtMs() <= 0L) {
+            return unavailableMetrics(requested, "telemetry-not-ready", sampledAtMs);
+        }
 
+        Map<String, IntegrationMetricSample> available = globalSamples(snapshot);
+        Map<String, IntegrationMetricSample> selected = new LinkedHashMap<>(requested.size());
         for (String key : requested) {
-            switch (key) {
-                case IntegrationMetricSchema.IRIS_CHUNK_STREAM_MS -> out.put(key, sampleChunkStreamMetric(now));
-                case IntegrationMetricSchema.IRIS_PREGEN_QUEUE -> out.put(key, samplePregenQueueMetric(now));
-                case IntegrationMetricSchema.IRIS_BIOME_CACHE_HIT_RATE -> out.put(key, sampleBiomeCacheHitRateMetric(now));
-                default -> out.put(key, IntegrationMetricSample.unavailable(
-                        IntegrationMetricSchema.descriptor(key),
-                        "unsupported-key",
-                        now
-                ));
+            IntegrationMetricSample sample = available.get(key);
+            selected.put(key, sample == null
+                    ? unavailable(key, "unsupported-key", sampledAtMs)
+                    : sample);
+        }
+        return Map.copyOf(selected);
+    }
+
+    @Override
+    public List<IntegrationMetricGroup> metricGroups() {
+        IrisTelemetrySnapshot snapshot = safeSnapshot();
+        if (snapshot.sampledAtMs() <= 0L || snapshot.worlds().isEmpty()) {
+            return List.of();
+        }
+
+        List<EngineTelemetrySnapshot> worlds = new ArrayList<>(snapshot.worlds());
+        worlds.sort(Comparator.comparing(EngineTelemetrySnapshot::worldIdentity));
+        List<IntegrationMetricGroup> groups = new ArrayList<>(worlds.size());
+        for (EngineTelemetrySnapshot world : worlds) {
+            groups.add(new IntegrationMetricGroup(
+                    "world",
+                    world.worldIdentity(),
+                    world.worldName(),
+                    Map.of(
+                            "plugin", "iris",
+                            "dimension", world.dimensionKey()
+                    ),
+                    worldSamples(world, snapshot.pregenerator())
+            ));
+        }
+        return List.copyOf(groups);
+    }
+
+    private Map<String, IntegrationMetricSample> globalSamples(IrisTelemetrySnapshot snapshot) {
+        long sampledAtMs = snapshot.sampledAtMs();
+        EngineTelemetrySnapshot.Aggregate aggregate = snapshot.aggregate();
+        Map<String, IntegrationMetricSample> samples = new LinkedHashMap<>();
+        put(samples, IntegrationMetricSchema.IRIS_WORLD_COUNT, aggregate.worldCount(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_ACTIVE, aggregate.active(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_CLOSING, aggregate.closing() + snapshot.closingEngines(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_FAILED, aggregate.failed(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_STUDIO, aggregate.studio(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_PENDING_REGISTRATIONS, snapshot.pendingRegistrations(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_LOADED_CHUNKS, aggregate.loadedChunks(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_LOADED_ENTITIES, aggregate.loadedEntities(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENTITY_SATURATION, aggregate.entitySaturationMax(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_SESSION, aggregate.generatedSession(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_TOTAL, aggregate.generatedTotal(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_PER_SECOND, aggregate.chunksPerSecond(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_BLOCK_UPDATES_PER_SECOND, aggregate.blockUpdatesPerSecond(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_PARALLELISM, aggregate.parallelism(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_GENERATION_ACTIVE_LEASES, aggregate.activeGenerationLeases(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_HOTLOADS_TOTAL, aggregate.hotloadsTotal(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MAINTENANCE_ACTIVE_TASKS, snapshot.maintenanceActiveTasks(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MAINTENANCE_WORKERS, snapshot.maintenanceWorkers(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_RESIDENT_PLATES, aggregate.mantleResidentPlates(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_QUEUED_PLATES, aggregate.mantleQueuedPlates(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_IDLE_AVERAGE_MS, aggregate.mantleIdleAverageMs(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_IDLE_MAX_MS, aggregate.mantleIdleMaxMs(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_IDLE_MIN_MS, aggregate.mantleIdleMinMs(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_HEAP_USAGE, snapshot.heapUsage(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_RECLAIM_URGENCY, snapshot.reclaimUrgency(), sampledAtMs);
+        putCacheSamples(samples, snapshot.caches(), sampledAtMs);
+        putPregenSamples(samples, snapshot.pregenerator(), sampledAtMs);
+        putTimingSamples(samples, aggregate.generationTimingMaximaMs(), sampledAtMs);
+        return Map.copyOf(samples);
+    }
+
+    private Map<String, IntegrationMetricSample> worldSamples(
+            EngineTelemetrySnapshot world,
+            IrisTelemetrySnapshot.PregenSnapshot pregenerator
+    ) {
+        long sampledAtMs = world.sampledAtMs();
+        Map<String, IntegrationMetricSample> samples = new LinkedHashMap<>();
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_ACTIVE, world.active() ? 1 : 0, sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_CLOSING, world.closing() ? 1 : 0, sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_FAILED, world.failed() ? 1 : 0, sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_STUDIO, world.studio() ? 1 : 0, sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_LOADED_CHUNKS, world.loadedChunks(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_LOADED_ENTITIES, world.loadedEntities(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENTITY_SATURATION, world.entitySaturation(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_SESSION, world.generatedSession(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_TOTAL, world.generatedTotal(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_CHUNKS_PER_SECOND, world.chunksPerSecond(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_BLOCK_UPDATES_PER_SECOND, world.blockUpdatesPerSecond(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_ENGINE_PARALLELISM, world.parallelism(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_GENERATION_ACTIVE_LEASES, world.activeGenerationLeases(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_HOTLOADS_TOTAL, world.hotloadsTotal(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_RESIDENT_PLATES, world.mantleResidentPlates(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_QUEUED_PLATES, world.mantleQueuedPlates(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_MANTLE_IDLE_AVERAGE_MS, world.mantleIdleMs(), sampledAtMs);
+        boolean targetsWorld = pregenerator.active()
+                && world.worldIdentity().equals(pregenerator.worldIdentity());
+        putPregenSamples(samples, targetsWorld ? pregenerator : IrisTelemetrySnapshot.PregenSnapshot.INACTIVE, sampledAtMs);
+        putTimingSamples(samples, world.generationTimingsMs(), sampledAtMs);
+        samples.keySet().retainAll(IntegrationMetricSchema.irisWorldKeys());
+        return Map.copyOf(samples);
+    }
+
+    private void putCacheSamples(
+            Map<String, IntegrationMetricSample> samples,
+            IrisTelemetrySnapshot.CacheSnapshot caches,
+            long sampledAtMs
+    ) {
+        putCacheBucket(samples, caches.total(), IntegrationMetricSchema.IRIS_CACHE_COUNT, IntegrationMetricSchema.IRIS_CACHE_ENTRIES, IntegrationMetricSchema.IRIS_CACHE_CAPACITY, IntegrationMetricSchema.IRIS_CACHE_USAGE, sampledAtMs);
+        putCacheBucket(samples, caches.resource(), IntegrationMetricSchema.IRIS_CACHE_RESOURCE_COUNT, IntegrationMetricSchema.IRIS_CACHE_RESOURCE_ENTRIES, IntegrationMetricSchema.IRIS_CACHE_RESOURCE_CAPACITY, IntegrationMetricSchema.IRIS_CACHE_RESOURCE_USAGE, sampledAtMs);
+        putCacheBucket(samples, caches.stream2d(), IntegrationMetricSchema.IRIS_CACHE_STREAM_2D_COUNT, IntegrationMetricSchema.IRIS_CACHE_STREAM_2D_ENTRIES, IntegrationMetricSchema.IRIS_CACHE_STREAM_2D_CAPACITY, IntegrationMetricSchema.IRIS_CACHE_STREAM_2D_USAGE, sampledAtMs);
+        putCacheBucket(samples, caches.stream3d(), IntegrationMetricSchema.IRIS_CACHE_STREAM_3D_COUNT, IntegrationMetricSchema.IRIS_CACHE_STREAM_3D_ENTRIES, IntegrationMetricSchema.IRIS_CACHE_STREAM_3D_CAPACITY, IntegrationMetricSchema.IRIS_CACHE_STREAM_3D_USAGE, sampledAtMs);
+        putCacheBucket(samples, caches.other(), IntegrationMetricSchema.IRIS_CACHE_OTHER_COUNT, IntegrationMetricSchema.IRIS_CACHE_OTHER_ENTRIES, IntegrationMetricSchema.IRIS_CACHE_OTHER_CAPACITY, IntegrationMetricSchema.IRIS_CACHE_OTHER_USAGE, sampledAtMs);
+    }
+
+    private void putCacheBucket(
+            Map<String, IntegrationMetricSample> samples,
+            IrisTelemetrySnapshot.CacheBucket bucket,
+            String countKey,
+            String entriesKey,
+            String capacityKey,
+            String usageKey,
+            long sampledAtMs
+    ) {
+        put(samples, countKey, bucket.count(), sampledAtMs);
+        put(samples, entriesKey, bucket.entries(), sampledAtMs);
+        put(samples, capacityKey, bucket.capacity(), sampledAtMs);
+        put(samples, usageKey, bucket.usage(), sampledAtMs);
+    }
+
+    private void putPregenSamples(
+            Map<String, IntegrationMetricSample> samples,
+            IrisTelemetrySnapshot.PregenSnapshot pregenerator,
+            long sampledAtMs
+    ) {
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_ACTIVE, pregenerator.active() ? 1 : 0, sampledAtMs);
+        if (!pregenerator.active()) {
+            for (String key : Set.of(
+                    IntegrationMetricSchema.IRIS_PREGEN_PAUSED,
+                    IntegrationMetricSchema.IRIS_PREGEN_PROGRESS,
+                    IntegrationMetricSchema.IRIS_PREGEN_GENERATED,
+                    IntegrationMetricSchema.IRIS_PREGEN_TOTAL,
+                    IntegrationMetricSchema.IRIS_PREGEN_QUEUE,
+                    IntegrationMetricSchema.IRIS_PREGEN_THROUGHPUT,
+                    IntegrationMetricSchema.IRIS_PREGEN_ETA_MS,
+                    IntegrationMetricSchema.IRIS_PREGEN_ELAPSED_MS,
+                    IntegrationMetricSchema.IRIS_PREGEN_FAILED)) {
+                samples.put(key, unavailable(key, "pregen-inactive", sampledAtMs));
             }
+            return;
         }
 
-        return out;
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_PAUSED, pregenerator.paused() ? 1 : 0, sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_PROGRESS, pregenerator.progressPercent(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_GENERATED, pregenerator.generated(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_TOTAL, pregenerator.total(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_QUEUE, pregenerator.remaining(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_THROUGHPUT, pregenerator.chunksPerSecond(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_ETA_MS, pregenerator.etaMs(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_ELAPSED_MS, pregenerator.elapsedMs(), sampledAtMs);
+        put(samples, IntegrationMetricSchema.IRIS_PREGEN_FAILED, pregenerator.failed(), sampledAtMs);
     }
 
-    private IntegrationMetricSample sampleChunkStreamMetric(long now) {
-        IntegrationMetricDescriptor descriptor = IntegrationMetricSchema.descriptor(IntegrationMetricSchema.IRIS_CHUNK_STREAM_MS);
-
-        double chunksPerSecond = PregeneratorJob.chunksPerSecond();
-
-        if (chunksPerSecond > 0D) {
-            return IntegrationMetricSample.available(descriptor, 1000D / chunksPerSecond, now);
+    private void putTimingSamples(
+            Map<String, IntegrationMetricSample> samples,
+            Map<String, Double> timings,
+            long sampledAtMs
+    ) {
+        for (Map.Entry<String, String> entry : TIMING_KEYS.entrySet()) {
+            Double value = timings.get(entry.getKey());
+            samples.put(entry.getValue(), value == null
+                    ? unavailable(entry.getValue(), "timing-not-available", sampledAtMs)
+                    : available(entry.getValue(), value, sampledAtMs));
         }
-
-        IrisEngineSVC engineService = Iris.service(IrisEngineSVC.class);
-        if (engineService != null) {
-            double idle = engineService.getAverageIdleDuration();
-            if (idle > 0D && Double.isFinite(idle)) {
-                return IntegrationMetricSample.available(descriptor, idle, now);
-            }
-        }
-
-        return IntegrationMetricSample.available(descriptor, 0D, now);
     }
 
-    private IntegrationMetricSample samplePregenQueueMetric(long now) {
-        IntegrationMetricDescriptor descriptor = IntegrationMetricSchema.descriptor(IntegrationMetricSchema.IRIS_PREGEN_QUEUE);
-        long totalQueue = 0L;
-        boolean hasAnySource = false;
-
-        long pregenRemaining = PregeneratorJob.chunksRemaining();
-        if (pregenRemaining >= 0L) {
-            totalQueue += pregenRemaining;
-            hasAnySource = true;
-        }
-
-        IrisEngineSVC engineService = Iris.service(IrisEngineSVC.class);
-        if (engineService != null) {
-            totalQueue += Math.max(0, engineService.getQueuedTectonicPlateCount());
-            hasAnySource = true;
-        }
-
-        if (!hasAnySource) {
-            return IntegrationMetricSample.unavailable(descriptor, "queue-not-available", now);
-        }
-
-        return IntegrationMetricSample.available(descriptor, totalQueue, now);
+    private void put(Map<String, IntegrationMetricSample> samples, String key, double value, long sampledAtMs) {
+        samples.put(key, available(key, value, sampledAtMs));
     }
 
-    private IntegrationMetricSample sampleBiomeCacheHitRateMetric(long now) {
-        IntegrationMetricDescriptor descriptor = IntegrationMetricSchema.descriptor(IntegrationMetricSchema.IRIS_BIOME_CACHE_HIT_RATE);
-        IrisEngineSVC engineService = Iris.service(IrisEngineSVC.class);
-        if (engineService == null) {
-            return IntegrationMetricSample.unavailable(descriptor, "engine-service-unavailable", now);
-        }
+    private IntegrationMetricSample available(String key, double value, long sampledAtMs) {
+        return IntegrationMetricSample.available(IntegrationMetricSchema.descriptor(key), value, sampledAtMs);
+    }
 
-        double ratio = engineService.getBiomeCacheUsageRatio();
-        if (!Double.isFinite(ratio)) {
-            return IntegrationMetricSample.unavailable(descriptor, "biome-cache-ratio-invalid", now);
-        }
+    private IntegrationMetricSample unavailable(String key, String reason, long sampledAtMs) {
+        return IntegrationMetricSample.unavailable(IntegrationMetricSchema.descriptor(key), reason, sampledAtMs);
+    }
 
-        return IntegrationMetricSample.available(descriptor, Math.max(0D, Math.min(1D, ratio)), now);
+    private Map<String, IntegrationMetricSample> unavailableMetrics(
+            Set<String> keys,
+            String reason,
+            long sampledAtMs
+    ) {
+        Map<String, IntegrationMetricSample> samples = new LinkedHashMap<>(keys.size());
+        for (String key : keys) {
+            samples.put(key, unavailable(key, reason, sampledAtMs));
+        }
+        return Map.copyOf(samples);
+    }
+
+    private IrisTelemetrySnapshot safeSnapshot() {
+        IrisTelemetrySnapshot snapshot = telemetrySupplier.get();
+        return snapshot == null ? IrisTelemetrySnapshot.EMPTY : snapshot;
+    }
+
+    private static IrisTelemetrySnapshot currentTelemetry() {
+        IrisEngineSVC service = IrisServices.get(IrisEngineSVC.class);
+        return service == null ? IrisTelemetrySnapshot.EMPTY : service.telemetrySnapshot();
     }
 }

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

@@ -0,0 +1,140 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.engine.framework.EngineTelemetrySnapshot;
+
+import java.util.List;
+
+record IrisTelemetrySnapshot(
+        long sampledAtMs,
+        List<EngineTelemetrySnapshot> worlds,
+        EngineTelemetrySnapshot.Aggregate aggregate,
+        int maintenanceActiveTasks,
+        int maintenanceWorkers,
+        int closingEngines,
+        int pendingRegistrations,
+        double heapUsage,
+        double reclaimUrgency,
+        CacheSnapshot caches,
+        PregenSnapshot pregenerator
+) {
+    static final IrisTelemetrySnapshot EMPTY = new IrisTelemetrySnapshot(
+            0L,
+            List.of(),
+            EngineTelemetrySnapshot.aggregate(List.of()),
+            0,
+            0,
+            0,
+            0,
+            0D,
+            0D,
+            CacheSnapshot.EMPTY,
+            PregenSnapshot.INACTIVE
+    );
+
+    IrisTelemetrySnapshot {
+        worlds = worlds == null ? List.of() : List.copyOf(worlds);
+        aggregate = aggregate == null ? EngineTelemetrySnapshot.aggregate(worlds) : aggregate;
+        maintenanceActiveTasks = Math.max(0, maintenanceActiveTasks);
+        maintenanceWorkers = Math.max(0, maintenanceWorkers);
+        closingEngines = Math.max(0, closingEngines);
+        pendingRegistrations = Math.max(0, pendingRegistrations);
+        heapUsage = finiteRatio(heapUsage);
+        reclaimUrgency = finiteRatio(reclaimUrgency);
+        caches = caches == null ? CacheSnapshot.EMPTY : caches;
+        pregenerator = pregenerator == null ? PregenSnapshot.INACTIVE : pregenerator;
+    }
+
+    private static double finiteRatio(double value) {
+        return Double.isFinite(value) ? Math.max(0D, Math.min(1D, value)) : 0D;
+    }
+
+    record CacheSnapshot(
+            CacheBucket total,
+            CacheBucket resource,
+            CacheBucket stream2d,
+            CacheBucket stream3d,
+            CacheBucket other
+    ) {
+        static final CacheSnapshot EMPTY = new CacheSnapshot(
+                CacheBucket.EMPTY,
+                CacheBucket.EMPTY,
+                CacheBucket.EMPTY,
+                CacheBucket.EMPTY,
+                CacheBucket.EMPTY
+        );
+
+        CacheSnapshot {
+            total = total == null ? CacheBucket.EMPTY : total;
+            resource = resource == null ? CacheBucket.EMPTY : resource;
+            stream2d = stream2d == null ? CacheBucket.EMPTY : stream2d;
+            stream3d = stream3d == null ? CacheBucket.EMPTY : stream3d;
+            other = other == null ? CacheBucket.EMPTY : other;
+        }
+    }
+
+    record CacheBucket(int count, long entries, long capacity) {
+        static final CacheBucket EMPTY = new CacheBucket(0, 0L, 0L);
+
+        CacheBucket {
+            count = Math.max(0, count);
+            entries = Math.max(0L, entries);
+            capacity = Math.max(0L, capacity);
+        }
+
+        double usage() {
+            return capacity <= 0L ? 0D : Math.min(1D, entries / (double) capacity);
+        }
+
+        CacheBucket plus(CacheBucket other) {
+            if (other == null) {
+                return this;
+            }
+            return new CacheBucket(count + other.count, entries + other.entries, capacity + other.capacity);
+        }
+    }
+
+    record PregenSnapshot(
+            boolean active,
+            String worldIdentity,
+            String worldName,
+            boolean paused,
+            double progressPercent,
+            long generated,
+            long total,
+            long remaining,
+            double chunksPerSecond,
+            long etaMs,
+            long elapsedMs,
+            long failed
+    ) {
+        static final PregenSnapshot INACTIVE = new PregenSnapshot(
+                false,
+                "",
+                "",
+                false,
+                0D,
+                0L,
+                0L,
+                0L,
+                0D,
+                0L,
+                0L,
+                0L
+        );
+
+        PregenSnapshot {
+            worldIdentity = worldIdentity == null ? "" : worldIdentity.trim();
+            worldName = worldName == null ? "" : worldName.trim();
+            progressPercent = Double.isFinite(progressPercent)
+                    ? Math.max(0D, Math.min(100D, progressPercent))
+                    : 0D;
+            generated = Math.max(0L, generated);
+            total = Math.max(0L, total);
+            remaining = Math.max(0L, remaining);
+            chunksPerSecond = Double.isFinite(chunksPerSecond) ? Math.max(0D, chunksPerSecond) : 0D;
+            etaMs = Math.max(0L, etaMs);
+            elapsedMs = Math.max(0L, elapsedMs);
+            failed = Math.max(0L, failed);
+        }
+    }
+}

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

@@ -0,0 +1,308 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.util.common.scheduling.J;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.Particle;
+import org.bukkit.Sound;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.entity.ExperienceOrb;
+import org.bukkit.entity.Item;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.util.Vector;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+final class TreeFellerPresentation {
+    private static final int MIN_BLOCKS_PER_PULSE = 4;
+    private static final int MAX_BLOCKS_PER_PULSE = 64;
+    private static final int TARGET_EROSION_PULSES = 60;
+    private static final int MAX_EFFECT_ORIGINS_PER_PULSE = 16;
+
+    private final Player player;
+    private final World sourceWorld;
+    private final Queue<PendingDrop> pendingDrops = new ConcurrentLinkedQueue<>();
+    private final AtomicBoolean flushScheduled = new AtomicBoolean();
+    private final AtomicBoolean fallbackScheduled = new AtomicBoolean();
+    private final AtomicBoolean completed = new AtomicBoolean();
+    private final AtomicBoolean effectFailureReported = new AtomicBoolean();
+    private final AtomicBoolean deliveryFailureReported = new AtomicBoolean();
+    private final AtomicInteger deliveryPulses = new AtomicInteger();
+    private volatile Location fallbackLocation;
+
+    TreeFellerPresentation(Player player, World sourceWorld, Location fallbackLocation) {
+        this.player = player;
+        this.sourceWorld = sourceWorld;
+        this.fallbackLocation = fallbackLocation.clone();
+    }
+
+    static int blocksPerPulse(int blockCount) {
+        int requested = Math.max(1, (blockCount + TARGET_EROSION_PULSES - 1) / TARGET_EROSION_PULSES);
+        return Math.max(MIN_BLOCKS_PER_PULSE, Math.min(requested, MAX_BLOCKS_PER_PULSE));
+    }
+
+    static int effectStride(int blocksPerPulse) {
+        return Math.max(
+                1,
+                (blocksPerPulse + MAX_EFFECT_ORIGINS_PER_PULSE - 1) / MAX_EFFECT_ORIGINS_PER_PULSE
+        );
+    }
+
+    static List<ItemStack> consolidateDrops(Collection<ItemStack> drops) {
+        List<ItemStack> consolidated = new ArrayList<>();
+        for (ItemStack drop : drops) {
+            mergeDrop(consolidated, drop);
+        }
+        return List.copyOf(consolidated);
+    }
+
+    void activate(Block block) {
+        try {
+            Location center = block.getLocation().clone().add(0.5D, 0.5D, 0.5D);
+            World world = block.getWorld();
+            world.spawnParticle(Particle.ENCHANT, center, 24, 0.45D, 0.45D, 0.45D, 0.18D);
+            world.spawnParticle(Particle.END_ROD, center, 8, 0.25D, 0.25D, 0.25D, 0.035D);
+            world.playSound(center, Sound.BLOCK_ENCHANTMENT_TABLE_USE, 0.55F, 1.35F);
+            world.playSound(center, Sound.BLOCK_AMETHYST_BLOCK_CHIME, 0.4F, 0.8F);
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+    }
+
+    void erode(
+            Location source,
+            BlockData visualData,
+            int erosionOrder,
+            int processed,
+            int blocksPerPulse,
+            int effectStride,
+            int totalBlocks
+    ) {
+        if (processed % effectStride != 0 || source.getWorld() == null) {
+            return;
+        }
+        try {
+            World world = source.getWorld();
+            world.spawnParticle(Particle.BLOCK, source, 5, 0.3D, 0.3D, 0.3D, 0.04D, visualData);
+            world.spawnParticle(Particle.ENCHANT, source, 3, 0.28D, 0.28D, 0.28D, 0.12D);
+            if (processed % blocksPerPulse == 0) {
+                double progress = totalBlocks <= 1 ? 1D : (double) erosionOrder / (double) (totalBlocks - 1);
+                float pitch = (float) Math.min(1.95D, 0.65D + (progress * 1.25D));
+                world.playSound(source, Sound.BLOCK_AMETHYST_BLOCK_CHIME, 0.22F, pitch);
+            }
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+    }
+
+    boolean routeDrop(Object drop) {
+        if (!(drop instanceof ItemStack item)) {
+            return false;
+        }
+        if (item.getType() == Material.AIR || item.getAmount() <= 0) {
+            return true;
+        }
+        return enqueue(new PendingDrop(item.clone(), 0));
+    }
+
+    boolean routeExperience(int experience) {
+        return experience <= 0 || enqueue(new PendingDrop(null, experience));
+    }
+
+    void finish() {
+        completed.set(true);
+        if (!pendingDrops.isEmpty()) {
+            scheduleFlush();
+        }
+    }
+
+    private boolean enqueue(PendingDrop drop) {
+        pendingDrops.add(drop);
+        if (scheduleFlush()) {
+            return true;
+        }
+        return !pendingDrops.remove(drop);
+    }
+
+    private boolean scheduleFlush() {
+        if (pendingDrops.isEmpty() || !flushScheduled.compareAndSet(false, true)) {
+            return true;
+        }
+        fallbackScheduled.set(false);
+        Runnable retired = () -> {
+            if (!scheduleFallbackFlush()) {
+                flushScheduled.set(false);
+                IrisLogging.error("Unable to deliver queued Iris tree-feller drops after the player retired.");
+            }
+        };
+        if (J.runEntity(player, this::flushAtPlayer, 1, retired)) {
+            return true;
+        }
+        return scheduleFallbackFlush();
+    }
+
+    private boolean scheduleFallbackFlush() {
+        if (!fallbackScheduled.compareAndSet(false, true)) {
+            return true;
+        }
+        Location fallback = fallbackLocation.clone();
+        if (J.runAt(fallback, () -> flushAtFallback(fallback), 1)) {
+            return true;
+        }
+        fallbackScheduled.set(false);
+        flushScheduled.set(false);
+        return false;
+    }
+
+    private void flushAtPlayer() {
+        if (!player.isOnline() || !player.getWorld().equals(sourceWorld)) {
+            if (!scheduleFallbackFlush()) {
+                IrisLogging.error("Unable to deliver queued Iris tree-feller drops at their fallback location.");
+            }
+            return;
+        }
+        Location target = player.getLocation().clone().add(0D, 0.15D, 0D);
+        fallbackLocation = target.clone();
+        deliverBatch(target, drainPendingDrops(), true);
+        completeFlush();
+    }
+
+    private void flushAtFallback(Location fallback) {
+        deliverBatch(fallback, drainPendingDrops(), false);
+        completeFlush();
+    }
+
+    private DropBatch drainPendingDrops() {
+        List<ItemStack> items = new ArrayList<>();
+        long experience = 0L;
+        PendingDrop pending;
+        while ((pending = pendingDrops.poll()) != null) {
+            if (pending.item() != null) {
+                items.add(pending.item());
+            }
+            experience = Math.min(Integer.MAX_VALUE, experience + pending.experience());
+        }
+        return new DropBatch(consolidateDrops(items), (int) experience);
+    }
+
+    private void deliverBatch(Location target, DropBatch batch, boolean atPlayer) {
+        World world = target.getWorld();
+        if (world == null) {
+            requeueBatch(batch);
+            return;
+        }
+        int deliveredItems = 0;
+        for (int index = 0; index < batch.items().size(); index++) {
+            ItemStack item = batch.items().get(index);
+            Item dropped;
+            try {
+                dropped = world.dropItem(target, item);
+            } catch (Throwable error) {
+                requeueUndelivered(batch, index);
+                reportDeliveryFailure(error);
+                return;
+            }
+            deliveredItems++;
+            try {
+                dropped.setVelocity(new Vector(0D, 0.08D, 0D));
+            } catch (Throwable error) {
+                reportEffectFailure(error);
+            }
+        }
+        if (batch.experience() > 0) {
+            try {
+                ExperienceOrb orb = world.spawn(target.clone().add(0D, 0.35D, 0D), ExperienceOrb.class);
+                orb.setExperience(batch.experience());
+            } catch (Throwable error) {
+                pendingDrops.add(new PendingDrop(null, batch.experience()));
+                reportDeliveryFailure(error);
+            }
+        }
+        try {
+            int enchantParticles = Math.min(32, 6 + (deliveredItems * 2));
+            Location effectLocation = target.clone().add(0D, 0.35D, 0D);
+            world.spawnParticle(Particle.ENCHANT, effectLocation, enchantParticles, 0.35D, 0.25D, 0.35D, 0.15D);
+            world.spawnParticle(Particle.END_ROD, effectLocation, Math.min(8, 2 + deliveredItems), 0.2D, 0.2D, 0.2D, 0.025D);
+            int deliveryPulse = deliveryPulses.incrementAndGet();
+            if (atPlayer && (deliveryPulse == 1 || deliveryPulse % 4 == 0 || completed.get())) {
+                world.playSound(target, Sound.BLOCK_AMETHYST_BLOCK_CHIME, 0.2F, 1.65F);
+            }
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+    }
+
+    private void completeFlush() {
+        fallbackScheduled.set(false);
+        flushScheduled.set(false);
+        if (!pendingDrops.isEmpty() && !scheduleFlush()) {
+            IrisLogging.error("Unable to schedule the remaining Iris tree-feller drops.");
+        }
+    }
+
+    private void requeueBatch(DropBatch batch) {
+        requeueUndelivered(batch, 0);
+    }
+
+    private void requeueUndelivered(DropBatch batch, int firstUndeliveredItem) {
+        for (int index = firstUndeliveredItem; index < batch.items().size(); index++) {
+            pendingDrops.add(new PendingDrop(batch.items().get(index), 0));
+        }
+        if (batch.experience() > 0) {
+            pendingDrops.add(new PendingDrop(null, batch.experience()));
+        }
+    }
+
+    private void reportEffectFailure(Throwable error) {
+        if (effectFailureReported.compareAndSet(false, true)) {
+            IrisLogging.reportError("Failed to render an Iris tree-feller effect.", error);
+        }
+    }
+
+    private void reportDeliveryFailure(Throwable error) {
+        if (deliveryFailureReported.compareAndSet(false, true)) {
+            IrisLogging.reportError("Failed to deliver an Iris tree-feller drop; it remains queued for retry.", error);
+        }
+    }
+
+    private static void mergeDrop(List<ItemStack> consolidated, ItemStack source) {
+        if (source == null || source.getType() == Material.AIR || source.getAmount() <= 0) {
+            return;
+        }
+        int remaining = source.getAmount();
+        for (ItemStack existing : consolidated) {
+            if (!existing.isSimilar(source) || existing.getAmount() >= existing.getMaxStackSize()) {
+                continue;
+            }
+            int transferable = Math.min(remaining, existing.getMaxStackSize() - existing.getAmount());
+            existing.setAmount(existing.getAmount() + transferable);
+            remaining -= transferable;
+            if (remaining == 0) {
+                return;
+            }
+        }
+        int maximumStackSize = Math.max(1, source.getMaxStackSize());
+        while (remaining > 0) {
+            ItemStack stack = source.clone();
+            stack.setAmount(Math.min(remaining, maximumStackSize));
+            consolidated.add(stack);
+            remaining -= stack.getAmount();
+        }
+    }
+
+    private record PendingDrop(ItemStack item, int experience) {
+    }
+
+    private record DropBatch(List<ItemStack> items, int experience) {
+    }
+}

adapters/bukkit/plugin/src/main/resources/paper-plugin.yml

@@ -8,6 +8,10 @@ load: STARTUP
 authors: [ cyberpwn, NextdoorPsycho, Vatuu ]
 website: volmit.com
 description: More than a Dimension!
+permissions:
+  iris.treefeller:
+    description: Allows survival players to fell Iris-managed trees with an axe.
+    default: op
 dependencies:
   server:
     PlaceholderAPI:

adapters/bukkit/plugin/src/main/resources/plugin.yml

@@ -22,7 +22,11 @@ loadbefore: [ Multiverse-Core ]
 authors: [ cyberpwn, NextdoorPsycho, Vatuu ]
 website: volmit.com
 description: More than a Dimension!
-commands:
-  iris:
-    aliases: [ ir, irs ]
+commands:
+  iris:
+    aliases: [ ir, irs ]
+permissions:
+  iris.treefeller:
+    description: Allows survival players to fell Iris-managed trees with an axe.
+    default: op
 api-version: '${apiVersion}'

adapters/bukkit/plugin/src/test/java/art/arcane/iris/PaperPluginMetadataTest.java

@@ -2,6 +2,8 @@ package art.arcane.iris;
 
 import org.bukkit.plugin.PluginDescriptionFile;
 import org.bukkit.plugin.PluginLoadOrder;
+import org.bukkit.permissions.Permission;
+import org.bukkit.permissions.PermissionDefault;
 import org.junit.Test;
 
 import java.io.InputStream;
@@ -54,6 +56,9 @@ public class PaperPluginMetadataTest {
         assertTrue(metadata.contains("folia-supported: true"));
         assertTrue(metadata.contains("load: STARTUP"));
         assertFalse(metadata.contains("commands:"));
+        assertTrue(metadata.contains("permissions:\n  iris.treefeller:\n"
+                + "    description: Allows survival players to fell Iris-managed trees with an axe.\n"
+                + "    default: op"));
         for (String pluginId : JOINED_PLUGIN_IDS) {
             assertTrue(metadata.contains(optionalDependencyBlock(pluginId, "BEFORE", true)));
         }
@@ -76,6 +81,13 @@ public class PaperPluginMetadataTest {
         assertEquals(List.of("ir", "irs"), commands.get("iris").get("aliases"));
         assertEquals(BUKKIT_SOFT_DEPEND_IDS, metadata.getSoftDepend());
         assertEquals(List.of("Multiverse-Core"), metadata.getLoadBeforePlugins());
+        Permission treeFeller = metadata.getPermissions().stream()
+                .filter(permission -> "iris.treefeller".equals(permission.getName()))
+                .findFirst()
+                .orElse(null);
+        assertNotNull(treeFeller);
+        assertEquals("Allows survival players to fell Iris-managed trees with an axe.", treeFeller.getDescription());
+        assertEquals(PermissionDefault.OP, treeFeller.getDefault());
     }
 
     @Test

adapters/bukkit/plugin/src/test/java/art/arcane/iris/api/tree/TreeFellerOptionsTest.java

@@ -0,0 +1,28 @@
+package art.arcane.iris.api.tree;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class TreeFellerOptionsTest {
+    @Test
+    public void factoriesExposeStableAccessModes() {
+        TreeFellerOptions standalone = TreeFellerOptions.standalone();
+        TreeFellerOptions override = TreeFellerOptions.integrationOverride(75, TreeFellerRunHooks.NONE);
+
+        assertEquals(TreeFellerAccess.STANDALONE, standalone.access());
+        assertEquals(0, standalone.durabilityPreservationChance());
+        assertEquals(TreeFellerAccess.INTEGRATION_OVERRIDE, override.access());
+        assertEquals(75, override.durabilityPreservationChance());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void chanceBelowRangeIsRejected() {
+        TreeFellerOptions.integrationOverride(-1, TreeFellerRunHooks.NONE);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void chanceAboveRangeIsRejected() {
+        TreeFellerOptions.integrationOverride(101, TreeFellerRunHooks.NONE);
+    }
+}

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

@@ -0,0 +1,83 @@
+package art.arcane.iris.core.runtime;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class BukkitEngineLifecycleContractTest {
+    @Test
+    public void closeFutureIsPublishedBeforeCloseWorkIsScheduled() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.bukkitChunkGeneratorSource")));
+        String closeAsync = method(source, "public CompletableFuture<Void> closeAsync()");
+
+        assertBefore(closeAsync, "closeFuture.compareAndSet(null, future)", "withExclusiveControlFuture(");
+        assertTrue(closeAsync.contains("while (!closeFuture.compareAndSet(null, future))"));
+        assertTrue(closeAsync.contains("operation.whenComplete("));
+        assertFalse(closeAsync.contains("!existing.isDone()"));
+
+        String baseHeight = method(source, "public int getBaseHeight(");
+        assertTrue(baseHeight.contains("currentEngine.acquireGenerationLease(\"bukkit_base_height\")"));
+        assertTrue(baseHeight.contains("IrisContext.open(currentEngine, lease.sessionId(), null)"));
+        assertTrue(baseHeight.contains("catch (GenerationSessionException e)"));
+
+        String generation = method(source, "public void generateNoise(");
+        assertTrue(generation.contains("throw new IllegalStateException"));
+        assertTrue(generation.contains("engine.acquireGenerationLease(\"bukkit_terrain_stage\")"));
+        assertTrue(generation.contains("IrisContext.open(engine, lease.sessionId(), null)"));
+        assertBefore(generation, "engine.acquireGenerationLease(\"bukkit_terrain_stage\")", "blocks.apply()");
+        assertFalse(generation.contains("RED_GLAZED_TERRACOTTA"));
+    }
+
+    @Test
+    public void targetedPregeneratorShutdownChecksWorldIdentity() throws IOException {
+        String jobSource = Files.readString(Path.of(System.getProperty("iris.pregeneratorJobSource")));
+        String targetedShutdown = method(jobSource,
+                "public static boolean shutdownInstanceForWorld(String worldIdentity)");
+
+        assertBefore(targetedShutdown, "inst.targetsWorldIdentity(worldIdentity)",
+                "shutdownAndWait(inst, WORLD_SHUTDOWN_TIMEOUT_MILLIS)");
+
+        String waitedShutdown = method(jobSource,
+                "private static boolean shutdownAndWait(PregeneratorJob inst, long timeoutMs)");
+        assertBefore(waitedShutdown, "inst.worker.interrupt()", "inst.worker.join(");
+        assertTrue(waitedShutdown.contains("inst.worker.isAlive()"));
+
+        String hooksSource = Files.readString(Path.of(System.getProperty("iris.bukkitEnginePlatformHooksSource")));
+        String hookShutdown = method(hooksSource, "public void shutdownPregenerator(Engine engine)");
+        assertTrue(hookShutdown.contains("PregeneratorJob.shutdownInstanceForWorld(world.identity());"));
+        assertFalse(hookShutdown.contains("PregeneratorJob.shutdownInstance();"));
+    }
+
+    private static void assertBefore(String source, String first, String second) {
+        int firstIndex = source.indexOf(first);
+        int secondIndex = source.indexOf(second);
+        assertTrue("Missing source contract token: " + first, firstIndex >= 0);
+        assertTrue("Missing source contract token: " + second, secondIndex >= 0);
+        assertTrue(first + " must occur before " + second, firstIndex < secondIndex);
+    }
+
+    private static String method(String source, String signature) {
+        int start = source.indexOf(signature);
+        assertTrue("Missing source contract signature: " + signature, start >= 0);
+        int openBrace = source.indexOf('{', start);
+        assertTrue("Missing source contract method body: " + signature, openBrace >= 0);
+        int depth = 0;
+        for (int index = openBrace; index < source.length(); index++) {
+            char current = source.charAt(index);
+            if (current == '{') {
+                depth++;
+            } else if (current == '}') {
+                depth--;
+                if (depth == 0) {
+                    return source.substring(start, index + 1);
+                }
+            }
+        }
+        throw new IllegalArgumentException("Unclosed source contract method: " + signature);
+    }
+}

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

@@ -0,0 +1,105 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.engine.framework.EngineAssignedWorldManager;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.world.WorldUnloadEvent;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class IrisEngineLifecycleContractTest {
+    @Test
+    public void engineServiceExclusivelyOwnsWorldUnload() throws NoSuchMethodException {
+        assertMonitorUnloadHandler(IrisEngineSVC.class.getMethod("onWorldUnload", WorldUnloadEvent.class));
+        for (Method method : EngineAssignedWorldManager.class.getDeclaredMethods()) {
+            boolean handlesWorldUnload = method.getParameterCount() == 1
+                    && method.getParameterTypes()[0] == WorldUnloadEvent.class
+                    && method.isAnnotationPresent(EventHandler.class);
+            assertFalse("EngineAssignedWorldManager must defer world unload ownership to IrisEngineSVC.", handlesWorldUnload);
+        }
+    }
+
+    @Test
+    public void registrationIdentityConflictsByWorldIdentityOrFolder() {
+        Path sharedFolder = Path.of("build", "worlds", "shared");
+        IrisEngineSVC.RegistrationIdentity first =
+                new IrisEngineSVC.RegistrationIdentity("minecraft:first", sharedFolder);
+        IrisEngineSVC.RegistrationIdentity sameIdentity =
+                new IrisEngineSVC.RegistrationIdentity("minecraft:first", Path.of("build", "worlds", "other"));
+        IrisEngineSVC.RegistrationIdentity sameFolder =
+                new IrisEngineSVC.RegistrationIdentity("minecraft:other", sharedFolder);
+        IrisEngineSVC.RegistrationIdentity distinct =
+                new IrisEngineSVC.RegistrationIdentity("minecraft:distinct", Path.of("build", "worlds", "distinct"));
+
+        assertTrue(first.conflictsWith(sameIdentity));
+        assertTrue(first.conflictsWith(sameFolder));
+        assertFalse(first.conflictsWith(distinct));
+    }
+
+    @Test
+    public void registrationRetryWaitsAsynchronouslyForClose() throws IOException {
+        String source = Files.readString(Path.of(System.getProperty("iris.engineSvcSource")));
+        String add = method(source, "private void add(World world)");
+        String remove = method(source, "private void remove(World world)");
+        String completeClose = method(source, "private void completeClose(");
+        String retry = method(source, "private void retryRegistrationAfterClose(");
+        String invokeClose = method(source, "private CompletableFuture<Void> invokeGeneratorClose()");
+
+        assertBefore(add, "findClosingGenerator(registrationIdentity)", "new Registered(");
+        assertBefore(remove, "reserveClose(registered)", "startClose(registered, closing)");
+        assertBefore(completeClose, "if (failure == null)", "closingGenerators.remove(closing)");
+        assertBefore(completeClose, "closingGenerators.remove(closing)", "closing.completion().complete(null)");
+        assertBefore(completeClose, "} else {", "closing.completion().completeExceptionally(failure)");
+        assertTrue(retry.contains("completion.whenComplete("));
+        assertTrue(retry.contains("J.s(() -> add(world), 1);"));
+        assertBefore(retry, "if (failure != null)", "J.s(() -> add(world), 1);");
+        assertFalse(retry.contains("completion.get("));
+        assertFalse(retry.contains("completion.join("));
+        assertTrue(invokeClose.contains("CompletableFuture.failedFuture("));
+        assertTrue(invokeClose.contains("future.whenComplete("));
+    }
+
+    private static void assertMonitorUnloadHandler(Method method) {
+        EventHandler eventHandler = method.getAnnotation(EventHandler.class);
+        assertNotNull(eventHandler);
+        assertEquals(EventPriority.MONITOR, eventHandler.priority());
+        assertTrue(eventHandler.ignoreCancelled());
+    }
+
+    private static void assertBefore(String source, String first, String second) {
+        int firstIndex = source.indexOf(first);
+        int secondIndex = source.indexOf(second);
+        assertTrue("Missing source contract token: " + first, firstIndex >= 0);
+        assertTrue("Missing source contract token: " + second, secondIndex >= 0);
+        assertTrue(first + " must occur before " + second, firstIndex < secondIndex);
+    }
+
+    private static String method(String source, String signature) {
+        int start = source.indexOf(signature);
+        assertTrue("Missing source contract signature: " + signature, start >= 0);
+        int openBrace = source.indexOf('{', start);
+        assertTrue("Missing source contract method body: " + signature, openBrace >= 0);
+        int depth = 0;
+        for (int index = openBrace; index < source.length(); index++) {
+            char current = source.charAt(index);
+            if (current == '{') {
+                depth++;
+            } else if (current == '}') {
+                depth--;
+                if (depth == 0) {
+                    return source.substring(start, index + 1);
+                }
+            }
+        }
+        throw new IllegalArgumentException("Unclosed source contract method: " + signature);
+    }
+}

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

@@ -1,24 +0,0 @@
-package art.arcane.iris.core.service;
-
-import org.junit.Test;
-
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-
-public class IrisEngineSVCTest {
-    @Test
-    public void maintenanceSkipsReductionWhenPregenDoesNotTargetWorld() {
-        assertTrue(IrisEngineSVC.shouldSkipMantleReductionForMaintenance(true, false));
-    }
-
-    @Test
-    public void maintenanceDoesNotSkipReductionForActivePregenWorld() {
-        assertFalse(IrisEngineSVC.shouldSkipMantleReductionForMaintenance(true, true));
-    }
-
-    @Test
-    public void noMaintenanceNeverSkipsReduction() {
-        assertFalse(IrisEngineSVC.shouldSkipMantleReductionForMaintenance(false, false));
-        assertFalse(IrisEngineSVC.shouldSkipMantleReductionForMaintenance(false, true));
-    }
-}

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

@@ -0,0 +1,174 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.engine.framework.EngineTelemetrySnapshot;
+import art.arcane.volmlib.integration.IntegrationMetricGroup;
+import art.arcane.volmlib.integration.IntegrationMetricSample;
+import art.arcane.volmlib.integration.IntegrationMetricSchema;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class IrisIntegrationServiceTest {
+    @Test
+    public void unavailableTelemetryDoesNotPublishFalseZeroes() {
+        IrisIntegrationService service = new IrisIntegrationService(() -> IrisTelemetrySnapshot.EMPTY);
+        Map<String, IntegrationMetricSample> samples = service.sampleMetrics(Set.of(
+                IntegrationMetricSchema.IRIS_WORLD_COUNT,
+                IntegrationMetricSchema.IRIS_PREGEN_QUEUE,
+                IntegrationMetricSchema.IRIS_GENERATION_TOTAL_MS));
+
+        for (IntegrationMetricSample sample : samples.values()) {
+            assertFalse(sample.available());
+            assertEquals("telemetry-not-ready", sample.message());
+        }
+        assertTrue(service.metricGroups().isEmpty());
+    }
+
+    @Test
+    public void publishesAggregateAndPerWorldMetricsFromOneImmutableSnapshot() {
+        long now = System.currentTimeMillis();
+        EngineTelemetrySnapshot first = world("minecraft:overworld", "world", 12L, 20L, 4D, now);
+        EngineTelemetrySnapshot second = world("minecraft:the_nether", "world_nether", 8L, 30L, 2D, now);
+        IrisTelemetrySnapshot snapshot = telemetry(
+                List.of(first, second),
+                new IrisTelemetrySnapshot.PregenSnapshot(
+                        true,
+                        first.worldIdentity(),
+                        first.worldName(),
+                        false,
+                        50D,
+                        100L,
+                        200L,
+                        100L,
+                        8D,
+                        2_000L,
+                        5_000L,
+                        1L
+                ),
+                now
+        );
+        IrisIntegrationService service = new IrisIntegrationService(() -> snapshot);
+
+        Map<String, IntegrationMetricSample> samples = service.sampleMetrics(Set.of(
+                IntegrationMetricSchema.IRIS_WORLD_COUNT,
+                IntegrationMetricSchema.IRIS_ENGINE_PENDING_REGISTRATIONS,
+                IntegrationMetricSchema.IRIS_LOADED_CHUNKS,
+                IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_TOTAL,
+                IntegrationMetricSchema.IRIS_PREGEN_THROUGHPUT,
+                IntegrationMetricSchema.IRIS_GENERATION_TOTAL_MS,
+                "iris.unsupported"
+        ));
+
+        assertEquals(2D, value(samples, IntegrationMetricSchema.IRIS_WORLD_COUNT), 0D);
+        assertEquals(3D, value(samples, IntegrationMetricSchema.IRIS_ENGINE_PENDING_REGISTRATIONS), 0D);
+        assertEquals(20D, value(samples, IntegrationMetricSchema.IRIS_LOADED_CHUNKS), 0D);
+        assertEquals(50D, value(samples, IntegrationMetricSchema.IRIS_CHUNKS_GENERATED_TOTAL), 0D);
+        assertEquals(8D, value(samples, IntegrationMetricSchema.IRIS_PREGEN_THROUGHPUT), 0D);
+        assertEquals(4D, value(samples, IntegrationMetricSchema.IRIS_GENERATION_TOTAL_MS), 0D);
+        assertFalse(samples.get("iris.unsupported").available());
+        assertEquals("unsupported-key", samples.get("iris.unsupported").message());
+
+        List<IntegrationMetricGroup> groups = service.metricGroups();
+        assertEquals(2, groups.size());
+        IntegrationMetricGroup overworld = groups.get(0);
+        IntegrationMetricGroup nether = groups.get(1);
+        assertEquals("minecraft:overworld", overworld.scopeId());
+        assertEquals(1D, value(overworld.samples(), IntegrationMetricSchema.IRIS_PREGEN_ACTIVE), 0D);
+        assertEquals(8D, value(overworld.samples(), IntegrationMetricSchema.IRIS_PREGEN_THROUGHPUT), 0D);
+        assertEquals("minecraft:the_nether", nether.scopeId());
+        assertEquals(0D, value(nether.samples(), IntegrationMetricSchema.IRIS_PREGEN_ACTIVE), 0D);
+        assertFalse(nether.samples().get(IntegrationMetricSchema.IRIS_PREGEN_QUEUE).available());
+    }
+
+    @Test
+    public void publishesEveryManagedWorldWithoutAWorldCountCap() {
+        long now = System.currentTimeMillis();
+        List<EngineTelemetrySnapshot> worlds = new ArrayList<>();
+        for (int index = 0; index < 48; index++) {
+            worlds.add(world("iris:world_" + index, "world_" + index, index, index, index, now));
+        }
+        IrisIntegrationService service = new IrisIntegrationService(
+                () -> telemetry(worlds, IrisTelemetrySnapshot.PregenSnapshot.INACTIVE, now)
+        );
+
+        List<IntegrationMetricGroup> groups = service.metricGroups();
+
+        assertEquals(48, groups.size());
+        assertEquals(48, groups.stream().map(IntegrationMetricGroup::scopeId).distinct().count());
+    }
+
+    private static IrisTelemetrySnapshot telemetry(
+            List<EngineTelemetrySnapshot> worlds,
+            IrisTelemetrySnapshot.PregenSnapshot pregenerator,
+            long now
+    ) {
+        IrisTelemetrySnapshot.CacheBucket resource = new IrisTelemetrySnapshot.CacheBucket(2, 10L, 100L);
+        IrisTelemetrySnapshot.CacheSnapshot caches = new IrisTelemetrySnapshot.CacheSnapshot(
+                resource,
+                resource,
+                IrisTelemetrySnapshot.CacheBucket.EMPTY,
+                IrisTelemetrySnapshot.CacheBucket.EMPTY,
+                IrisTelemetrySnapshot.CacheBucket.EMPTY
+        );
+        return new IrisTelemetrySnapshot(
+                now,
+                worlds,
+                EngineTelemetrySnapshot.aggregate(worlds),
+                1,
+                4,
+                0,
+                3,
+                0.5D,
+                0.1D,
+                caches,
+                pregenerator
+        );
+    }
+
+    private static EngineTelemetrySnapshot world(
+            String identity,
+            String name,
+            long loadedChunks,
+            long generatedTotal,
+            double generationMs,
+            long now
+    ) {
+        return new EngineTelemetrySnapshot(
+                now,
+                identity,
+                name,
+                "dimension",
+                true,
+                false,
+                false,
+                false,
+                loadedChunks,
+                3L,
+                0.25D,
+                generatedTotal,
+                generatedTotal,
+                2D,
+                4L,
+                2,
+                1,
+                1L,
+                4L,
+                1L,
+                10D,
+                Map.of("total", generationMs)
+        );
+    }
+
+    private static double value(Map<String, IntegrationMetricSample> samples, String key) {
+        IntegrationMetricSample sample = samples.get(key);
+        assertTrue(sample.available());
+        return sample.valueOr(-1D);
+    }
+}

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

@@ -0,0 +1,60 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.core.service.tree.TreeMarkerTraversal;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.player.PlayerItemHeldEvent;
+import org.bukkit.event.player.PlayerSwapHandItemsEvent;
+import org.bukkit.event.player.PlayerToggleSneakEvent;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class TreeFellerEventOrderTest {
+    @Test
+    public void standaloneIntentPrecedesMonitorFinalization() throws Exception {
+        Method request = TreeFellerSVC.class.getMethod("requestStandalone", org.bukkit.event.block.BlockBreakEvent.class);
+        Method finalize = TreeFellerSVC.class.getMethod("finalizeBreak", org.bukkit.event.block.BlockBreakEvent.class);
+        EventHandler requestHandler = request.getAnnotation(EventHandler.class);
+        EventHandler finalizeHandler = finalize.getAnnotation(EventHandler.class);
+
+        assertEquals(EventPriority.HIGHEST, requestHandler.priority());
+        assertTrue(requestHandler.ignoreCancelled());
+        assertEquals(EventPriority.MONITOR, finalizeHandler.priority());
+        assertFalse(finalizeHandler.ignoreCancelled());
+    }
+
+    @Test
+    public void incompleteDiscoveryFallsOnlyTheTrigger() {
+        TreeMarkerTraversal.Position trigger = new TreeMarkerTraversal.Position(4, 80, -2);
+        TreeMarkerTraversal.Discovery incomplete = new TreeMarkerTraversal.Discovery(
+                List.of(trigger, new TreeMarkerTraversal.Position(4, 81, -2)),
+                false
+        );
+
+        assertEquals(List.of(trigger), TreeFellerSVC.positionsForFelling(incomplete, trigger));
+    }
+
+    @Test
+    public void playerControlChangesHaltRunsAtMonitor() throws Exception {
+        Method sneak = TreeFellerSVC.class.getMethod("haltWhenSneakingStops", PlayerToggleSneakEvent.class);
+        Method held = TreeFellerSVC.class.getMethod("haltWhenHeldSlotChanges", PlayerItemHeldEvent.class);
+        Method hands = TreeFellerSVC.class.getMethod("haltWhenHandsSwap", PlayerSwapHandItemsEvent.class);
+
+        assertMonitorCancellationHandler(sneak);
+        assertMonitorCancellationHandler(held);
+        assertMonitorCancellationHandler(hands);
+    }
+
+    private void assertMonitorCancellationHandler(Method method) {
+        EventHandler handler = method.getAnnotation(EventHandler.class);
+
+        assertEquals(EventPriority.MONITOR, handler.priority());
+        assertTrue(handler.ignoreCancelled());
+    }
+}

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

@@ -0,0 +1,27 @@
+package art.arcane.iris.core.service;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class TreeFellerPresentationTest {
+    @Test
+    public void pulseSizeKeepsSmallTreesReadableAndLargeTreesBounded() {
+        assertEquals(4, TreeFellerPresentation.blocksPerPulse(1));
+        assertEquals(4, TreeFellerPresentation.blocksPerPulse(240));
+        assertEquals(10, TreeFellerPresentation.blocksPerPulse(600));
+        assertEquals(64, TreeFellerPresentation.blocksPerPulse(100_000));
+    }
+
+    @Test
+    public void effectSamplingStaysBoundedPerPulse() {
+        assertEquals(1, TreeFellerPresentation.effectStride(4));
+        assertEquals(1, TreeFellerPresentation.effectStride(16));
+        assertEquals(2, TreeFellerPresentation.effectStride(17));
+        assertEquals(2, TreeFellerPresentation.effectStride(31));
+        assertEquals(2, TreeFellerPresentation.effectStride(32));
+        assertEquals(3, TreeFellerPresentation.effectStride(33));
+        assertEquals(4, TreeFellerPresentation.effectStride(64));
+    }
+
+}

adapters/fabric/build.gradle

@@ -120,7 +120,8 @@ dependencies {
         libs.fabricApi.eventsInteraction,
         libs.fabricApi.networking,
         libs.fabricApi.rendering,
-        libs.fabricApi.keyMapping
+        libs.fabricApi.keyMapping,
+        libs.fabricApi.permission
     ]
     fabricApi.each { Object notation ->
         add('jij', notation)

adapters/fabric/logs/latest.log

@@ -1,5 +1,95 @@
-[17:42:11] [Test worker/INFO]: Iris registered custom content provider 'iris_deferred_test'
-[17:42:11] [Test worker/ERROR]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[19:42:28] [Test worker/INFO]: Iris registered custom content provider 'iris_deferred_test'
+[19:42:28] [Test worker/ERROR]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+java.lang.RuntimeException: second disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:55)
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47)
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65)
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53)
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77)
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28)
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19)
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88)
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63)
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122)
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
+[19:42:28] [Test worker/ERROR]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$FirstService
+java.lang.RuntimeException: first disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:54)
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84)
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47)
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65)
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53)
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77)
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28)
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19)
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88)
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103)
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63)
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122)
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
+[19:42:28] [Test worker/ERROR]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: cleanup failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32)
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
@@ -44,7 +134,7 @@ java.lang.RuntimeException: cleanup failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
-[17:42:11] [Test worker/ERROR]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[19:42:28] [Test worker/ERROR]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: enable failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:31)
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
@@ -92,7 +182,7 @@ java.lang.RuntimeException: enable failed
 	Suppressed: java.lang.RuntimeException: cleanup failed
 		at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32)
 		... 42 more
-[17:42:11] [Test worker/ERROR]: [worldcheck] server stop request failed
+[19:42:28] [Test worker/ERROR]: [worldcheck] server stop request failed
 java.lang.IllegalStateException: stop request failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$stopRequestFailureForcesNonzeroResult$1(ModdedWorldCheckTest.java:235)
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:179)
@@ -139,7 +229,7 @@ java.lang.IllegalStateException: stop request failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
-[17:42:11] [Test worker/ERROR]: [worldcheck] waiting for server shutdown failed
+[19:42:28] [Test worker/ERROR]: [worldcheck] waiting for server shutdown failed
 java.lang.IllegalStateException: shutdown wait failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$shutdownWaitFailureForcesNonzeroExit$0(ModdedWorldCheckTest.java:261)
 	at art.arcane.iris.modded.ModdedWorldCheck.awaitStopAndExit(ModdedWorldCheck.java:194)
@@ -186,7 +276,7 @@ java.lang.IllegalStateException: shutdown wait failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
-[17:42:11] [Test worker/ERROR]: [worldcheck] check failed
+[19:42:28] [Test worker/ERROR]: [worldcheck] check failed
 java.lang.IllegalStateException: check failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$thrownCheckStillRequestsStop$0(ModdedWorldCheckTest.java:221)
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:174)
@@ -233,8 +323,8 @@ java.lang.IllegalStateException: check failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
-[17:42:11] [Test worker/INFO]: Iris registered custom content provider 'iris_discovery_success'
-[17:42:11] [Test worker/ERROR]: Iris custom content provider discovery failed
+[19:42:28] [Test worker/INFO]: Iris registered custom content provider 'iris_discovery_success'
+[19:42:28] [Test worker/ERROR]: Iris custom content provider discovery failed
 java.lang.RuntimeException: provider init failed
 	at art.arcane.iris.modded.api.ModdedCustomContentRegistryTest.failedDiscoveryPublishesNothingAndPreservesTheCause(ModdedCustomContentRegistryTest.java:39)
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)

adapters/fabric/src/main/java/art/arcane/iris/fabric/FabricModdedLoader.java

@@ -19,15 +19,27 @@
 package art.arcane.iris.fabric;
 
 import art.arcane.iris.modded.ModdedLoader;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
 import net.fabricmc.api.EnvType;
+import net.fabricmc.fabric.api.event.player.PlayerBlockBreakEvents;
+import net.fabricmc.fabric.api.permission.v1.PermissionContextOwner;
 import net.fabricmc.loader.api.FabricLoader;
 import net.fabricmc.loader.api.ModContainer;
+import net.minecraft.core.BlockPos;
+import net.minecraft.resources.Identifier;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.permissions.PermissionLevel;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
 
 import java.io.File;
 import java.nio.file.Path;
 
 public final class FabricModdedLoader implements ModdedLoader {
+    private static final Identifier TREE_FELLER_PERMISSION = Identifier.fromNamespaceAndPath("iris", "treefeller");
+
     @Override
     public String platformName() {
         return "fabric";
@@ -74,4 +86,24 @@ public final class FabricModdedLoader implements ModdedLoader {
                 .map((Path p) -> p.toFile())
                 .orElse(null);
     }
+
+    @Override
+    public boolean hasTreeFellerPermission(ServerPlayer player) {
+        return ((PermissionContextOwner) player).checkPermission(
+                TREE_FELLER_PERMISSION,
+                PermissionLevel.GAMEMASTERS
+        );
+    }
+
+    @Override
+    public boolean canTreeFellerBreak(
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState state
+    ) {
+        BlockEntity blockEntity = state.hasBlockEntity() ? level.getBlockEntity(position) : null;
+        return ModdedTreeFellerService.runBreakProbe(() -> PlayerBlockBreakEvents.BEFORE.invoker()
+                .beforeBlockBreak(level, player, position, state, blockEntity));
+    }
 }

adapters/fabric/src/main/java/art/arcane/iris/fabric/IrisFabricBootstrap.java

@@ -42,6 +42,7 @@ import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.resources.Identifier;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.entity.player.Player;
@@ -60,13 +61,19 @@ public final class IrisFabricBootstrap implements ModInitializer {
         ServerLifecycleEvents.SERVER_STARTED.register((MinecraftServer server) -> ModdedEngineBootstrap.serverStarted(server));
         ServerLifecycleEvents.SERVER_STOPPING.register((MinecraftServer server) -> ModdedEngineBootstrap.stop());
         ServerLevelEvents.LOAD.register((MinecraftServer server, ServerLevel level) -> ModdedEngineBootstrap.levelLoaded(level));
+        ServerLevelEvents.UNLOAD.register((MinecraftServer server, ServerLevel level) -> ModdedEngineBootstrap.levelUnloaded(level));
         CommandRegistrationCallback.EVENT.register((CommandDispatcher<CommandSourceStack> dispatcher, CommandBuildContext buildContext, Commands.CommandSelection selection) -> IrisModdedCommands.register(dispatcher));
         PlayerBlockBreakEvents.BEFORE.register((Level level, Player player, BlockPos pos, BlockState state, BlockEntity blockEntity) -> {
-            if (level instanceof ServerLevel serverLevel) {
-                ModdedBlockBreakHandler.prepare(serverLevel, pos, state);
+            if (level instanceof ServerLevel serverLevel && player instanceof ServerPlayer serverPlayer) {
+                ModdedBlockBreakHandler.prepare(serverLevel, serverPlayer, pos, state);
             }
             return true;
         });
+        PlayerBlockBreakEvents.CANCELED.register((Level level, Player player, BlockPos pos, BlockState state, BlockEntity blockEntity) -> {
+            if (level instanceof ServerLevel serverLevel) {
+                ModdedBlockBreakHandler.cancel(serverLevel, pos);
+            }
+        });
         AttackBlockCallback.EVENT.register((Player player, Level level, InteractionHand hand, BlockPos pos, Direction direction) ->
                 ModdedWandService.attackBlock(player, level, hand, pos) ? InteractionResult.SUCCESS : InteractionResult.PASS);
         UseBlockCallback.EVENT.register((Player player, Level level, InteractionHand hand, BlockHitResult hit) ->

adapters/fabric/src/main/java/art/arcane/iris/fabric/mixin/BlockItemMixin.java

@@ -0,0 +1,25 @@
+package art.arcane.iris.fabric.mixin;
+
+import art.arcane.iris.modded.ModdedBlockBreakHandler;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.item.BlockItem;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.block.state.BlockState;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(BlockItem.class)
+public final class BlockItemMixin {
+    @Inject(method = "placeBlock", at = @At("RETURN"))
+    private void iris$clearTreeProvenance(
+            BlockPlaceContext context,
+            BlockState state,
+            CallbackInfoReturnable<Boolean> info
+    ) {
+        if (info.getReturnValue() && context.getLevel() instanceof ServerLevel level) {
+            ModdedBlockBreakHandler.clearPlacedProvenance(level, context.getClickedPos());
+        }
+    }
+}

adapters/fabric/src/main/java/art/arcane/iris/fabric/mixin/BlockMixin.java

@@ -48,6 +48,10 @@ public class BlockMixin {
         if (result == null) {
             return;
         }
+        if (result.routeCombinedDrops(info.getReturnValue())) {
+            info.setReturnValue(List.of());
+            return;
+        }
         List<ItemStack> drops = result.replaceVanillaDrops()
                 ? new ArrayList<>()
                 : new ArrayList<>(info.getReturnValue());

adapters/fabric/src/main/resources/irisworldgen.mixins.json

@@ -4,6 +4,7 @@
   "package": "art.arcane.iris.fabric.mixin",
   "compatibilityLevel": "JAVA_25",
   "mixins": [
+    "BlockItemMixin",
     "BlockMixin",
     "ServerPacksSourceMixin"
   ],

adapters/forge/logs/debug.log

@@ -1,8 +1,98 @@
-[18Jul2026 17:42:16.031] [Test worker/DEBUG] [io.netty.util.internal.logging.InternalLoggerFactory/]: Using SLF4J as the default logging framework
-[18Jul2026 17:42:16.033] [Test worker/DEBUG] [io.netty.util.ResourceLeakDetector/]: -Dio.netty.leakDetection.level: simple
-[18Jul2026 17:42:16.033] [Test worker/DEBUG] [io.netty.util.ResourceLeakDetector/]: -Dio.netty.leakDetection.targetRecords: 4
-[18Jul2026 17:42:18.043] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_deferred_test'
-[18Jul2026 17:42:18.104] [Test worker/ERROR] [Iris/]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[20Jul2026 19:42:36.918] [Test worker/DEBUG] [io.netty.util.internal.logging.InternalLoggerFactory/]: Using SLF4J as the default logging framework
+[20Jul2026 19:42:36.919] [Test worker/DEBUG] [io.netty.util.ResourceLeakDetector/]: -Dio.netty.leakDetection.level: simple
+[20Jul2026 19:42:36.919] [Test worker/DEBUG] [io.netty.util.ResourceLeakDetector/]: -Dio.netty.leakDetection.targetRecords: 4
+[20Jul2026 19:42:38.772] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_deferred_test'
+[20Jul2026 19:42:38.831] [Test worker/ERROR] [Iris/]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+java.lang.RuntimeException: second disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:55) ~[test/:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115) ~[junit-4.13.2.jar:4.13.2]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53) ~[?:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19) ~[?:?]
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33) ~[?:?]
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88) ~[?:?]
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63) ~[?:?]
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
+[20Jul2026 19:42:38.837] [Test worker/ERROR] [Iris/]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$FirstService
+java.lang.RuntimeException: first disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:54) ~[test/:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115) ~[junit-4.13.2.jar:4.13.2]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53) ~[?:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19) ~[?:?]
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33) ~[?:?]
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88) ~[?:?]
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63) ~[?:?]
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
+[20Jul2026 19:42:38.840] [Test worker/ERROR] [Iris/]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: cleanup failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
@@ -47,7 +137,7 @@ java.lang.RuntimeException: cleanup failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.110] [Test worker/ERROR] [Iris/]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[20Jul2026 19:42:38.843] [Test worker/ERROR] [Iris/]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: enable failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:31) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
@@ -95,7 +185,7 @@ java.lang.RuntimeException: enable failed
 	Suppressed: java.lang.RuntimeException: cleanup failed
 		at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32) ~[test/:?]
 		... 42 more
-[18Jul2026 17:42:18.144] [Test worker/ERROR] [Iris/]: [worldcheck] server stop request failed
+[20Jul2026 19:42:38.875] [Test worker/ERROR] [Iris/]: [worldcheck] server stop request failed
 java.lang.IllegalStateException: stop request failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$stopRequestFailureForcesNonzeroResult$1(ModdedWorldCheckTest.java:235) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:179) ~[main/:?]
@@ -142,7 +232,7 @@ java.lang.IllegalStateException: stop request failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.147] [Test worker/ERROR] [Iris/]: [worldcheck] waiting for server shutdown failed
+[20Jul2026 19:42:38.878] [Test worker/ERROR] [Iris/]: [worldcheck] waiting for server shutdown failed
 java.lang.IllegalStateException: shutdown wait failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$shutdownWaitFailureForcesNonzeroExit$0(ModdedWorldCheckTest.java:261) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.awaitStopAndExit(ModdedWorldCheck.java:194) ~[main/:?]
@@ -189,7 +279,7 @@ java.lang.IllegalStateException: shutdown wait failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.154] [Test worker/ERROR] [Iris/]: [worldcheck] check failed
+[20Jul2026 19:42:38.883] [Test worker/ERROR] [Iris/]: [worldcheck] check failed
 java.lang.IllegalStateException: check failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$thrownCheckStillRequestsStop$0(ModdedWorldCheckTest.java:221) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:174) ~[main/:?]
@@ -236,8 +326,8 @@ java.lang.IllegalStateException: check failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.160] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_discovery_success'
-[18Jul2026 17:42:18.161] [Test worker/ERROR] [Iris/]: Iris custom content provider discovery failed
+[20Jul2026 19:42:38.889] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_discovery_success'
+[20Jul2026 19:42:38.889] [Test worker/ERROR] [Iris/]: Iris custom content provider discovery failed
 java.lang.RuntimeException: provider init failed
 	at art.arcane.iris.modded.api.ModdedCustomContentRegistryTest.failedDiscoveryPublishesNothingAndPreservesTheCause(ModdedCustomContentRegistryTest.java:39) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]

adapters/forge/logs/latest.log

@@ -1,5 +1,95 @@
-[18Jul2026 17:42:18.043] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_deferred_test'
-[18Jul2026 17:42:18.104] [Test worker/ERROR] [Iris/]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[20Jul2026 19:42:38.772] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_deferred_test'
+[20Jul2026 19:42:38.831] [Test worker/ERROR] [Iris/]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+java.lang.RuntimeException: second disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:55) ~[test/:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115) ~[junit-4.13.2.jar:4.13.2]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53) ~[?:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19) ~[?:?]
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33) ~[?:?]
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88) ~[?:?]
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63) ~[?:?]
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
+[20Jul2026 19:42:38.837] [Test worker/ERROR] [Iris/]: Iris service onDisable failed for art.arcane.iris.modded.ModdedServiceManagerTest$FirstService
+java.lang.RuntimeException: first disable failed
+	at art.arcane.iris.modded.ModdedServiceManagerTest.disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures(ModdedServiceManagerTest.java:54) ~[test/:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runners.ParentRunner.run(ParentRunner.java:413) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.13.2.jar:4.13.2]
+	at org.junit.runner.JUnitCore.run(JUnitCore.java:115) ~[junit-4.13.2.jar:4.13.2]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.runRequest(JUnitTestExecutor.java:175) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:84) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.JUnitTestExecutor.accept(JUnitTestExecutor.java:47) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestDefinitionProcessor.processTestDefinition(AbstractJUnitTestDefinitionProcessor.java:65) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.SuiteTestDefinitionProcessor.processTestDefinition(SuiteTestDefinitionProcessor.java:53) ~[?:?]
+	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
+	at java.base/java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
+	at org.gradle.internal.dispatch.MethodInvocation.invokeOn(MethodInvocation.java:77) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:28) ~[?:?]
+	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:19) ~[?:?]
+	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33) ~[?:?]
+	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:88) ~[?:?]
+	at jdk.proxy1/jdk.proxy1.$Proxy4.processTestDefinition(Unknown Source) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:178) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:126) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:103) ~[?:?]
+	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:63) ~[?:?]
+	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:122) ~[?:?]
+	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
+	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
+[20Jul2026 19:42:38.840] [Test worker/ERROR] [Iris/]: Iris service rollback failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: cleanup failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
@@ -44,7 +134,7 @@ java.lang.RuntimeException: cleanup failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.110] [Test worker/ERROR] [Iris/]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
+[20Jul2026 19:42:38.843] [Test worker/ERROR] [Iris/]: Iris service onEnable failed for art.arcane.iris.modded.ModdedServiceManagerTest$SecondService
 java.lang.RuntimeException: enable failed
 	at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:31) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
@@ -92,7 +182,7 @@ java.lang.RuntimeException: enable failed
 	Suppressed: java.lang.RuntimeException: cleanup failed
 		at art.arcane.iris.modded.ModdedServiceManagerTest.rollsBackEnabledServicesAndPreservesCleanupFailures(ModdedServiceManagerTest.java:32) ~[test/:?]
 		... 42 more
-[18Jul2026 17:42:18.144] [Test worker/ERROR] [Iris/]: [worldcheck] server stop request failed
+[20Jul2026 19:42:38.875] [Test worker/ERROR] [Iris/]: [worldcheck] server stop request failed
 java.lang.IllegalStateException: stop request failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$stopRequestFailureForcesNonzeroResult$1(ModdedWorldCheckTest.java:235) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:179) ~[main/:?]
@@ -139,7 +229,7 @@ java.lang.IllegalStateException: stop request failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.147] [Test worker/ERROR] [Iris/]: [worldcheck] waiting for server shutdown failed
+[20Jul2026 19:42:38.878] [Test worker/ERROR] [Iris/]: [worldcheck] waiting for server shutdown failed
 java.lang.IllegalStateException: shutdown wait failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$shutdownWaitFailureForcesNonzeroExit$0(ModdedWorldCheckTest.java:261) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.awaitStopAndExit(ModdedWorldCheck.java:194) ~[main/:?]
@@ -186,7 +276,7 @@ java.lang.IllegalStateException: shutdown wait failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.154] [Test worker/ERROR] [Iris/]: [worldcheck] check failed
+[20Jul2026 19:42:38.883] [Test worker/ERROR] [Iris/]: [worldcheck] check failed
 java.lang.IllegalStateException: check failed
 	at art.arcane.iris.modded.ModdedWorldCheckTest.lambda$thrownCheckStillRequestsStop$0(ModdedWorldCheckTest.java:221) ~[test/:?]
 	at art.arcane.iris.modded.ModdedWorldCheck.runAndRequestStop(ModdedWorldCheck.java:174) ~[main/:?]
@@ -233,8 +323,8 @@ java.lang.IllegalStateException: check failed
 	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:72) ~[?:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69) [gradle-worker.jar:?]
 	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74) [gradle-worker.jar:?]
-[18Jul2026 17:42:18.160] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_discovery_success'
-[18Jul2026 17:42:18.161] [Test worker/ERROR] [Iris/]: Iris custom content provider discovery failed
+[20Jul2026 19:42:38.889] [Test worker/INFO] [Iris/]: Iris registered custom content provider 'iris_discovery_success'
+[20Jul2026 19:42:38.889] [Test worker/ERROR] [Iris/]: Iris custom content provider discovery failed
 java.lang.RuntimeException: provider init failed
 	at art.arcane.iris.modded.api.ModdedCustomContentRegistryTest.failedDiscoveryPublishesNothingAndPreservesTheCause(ModdedCustomContentRegistryTest.java:39) ~[test/:?]
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]

adapters/forge/src/main/java/art/arcane/iris/forge/ForgeModdedLoader.java

@@ -19,18 +19,37 @@
 package art.arcane.iris.forge;
 
 import art.arcane.iris.modded.ModdedLoader;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
+import net.minecraft.commands.Commands;
+import net.minecraft.core.BlockPos;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraftforge.common.util.Result;
+import net.minecraftforge.event.level.BlockEvent;
 import net.minecraftforge.fml.ModList;
 import net.minecraftforge.fml.loading.FMLEnvironment;
 import net.minecraftforge.fml.loading.FMLLoader;
 import net.minecraftforge.fml.loading.FMLPaths;
 import net.minecraftforge.forgespi.language.IModFileInfo;
 import net.minecraftforge.server.ServerLifecycleHooks;
+import net.minecraftforge.server.permission.PermissionAPI;
+import net.minecraftforge.server.permission.nodes.PermissionNode;
+import net.minecraftforge.server.permission.nodes.PermissionTypes;
 
 import java.io.File;
 import java.nio.file.Path;
 
 public final class ForgeModdedLoader implements ModdedLoader {
+    public static final PermissionNode<Boolean> TREE_FELLER_PERMISSION = new PermissionNode<>(
+            "iris",
+            "treefeller",
+            PermissionTypes.BOOLEAN,
+            (player, playerId, contexts) ->
+                    player != null && Commands.LEVEL_GAMEMASTERS.check(player.permissions())
+    );
+
     @Override
     public String platformName() {
         return "forge";
@@ -73,4 +92,29 @@ public final class ForgeModdedLoader implements ModdedLoader {
         IModFileInfo info = ModList.getModFileById("irisworldgen");
         return info == null ? null : info.getFile().getFilePath().toFile();
     }
+
+    @Override
+    public boolean hasTreeFellerPermission(ServerPlayer player) {
+        return PermissionAPI.getPermission(player, TREE_FELLER_PERMISSION);
+    }
+
+    @Override
+    public boolean canTreeFellerBreak(
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState state
+    ) {
+        return ModdedTreeFellerService.runBreakProbe(() -> {
+            BlockEvent.BreakEvent event = new BlockEvent.BreakEvent(
+                    level,
+                    position,
+                    state,
+                    player,
+                    Result.DEFAULT
+            );
+            BlockEvent.BreakEvent.BUS.post(event);
+            return !event.getResult().isDenied();
+        });
+    }
 }

adapters/forge/src/main/java/art/arcane/iris/forge/IrisForgeBlockLootModifier.java

@@ -65,6 +65,10 @@ public final class IrisForgeBlockLootModifier extends LootModifier {
         if (result == null) {
             return generatedLoot;
         }
+        if (result.routeCombinedDrops(generatedLoot)) {
+            generatedLoot.clear();
+            return generatedLoot;
+        }
         if (result.replaceVanillaDrops()) {
             generatedLoot.clear();
         }

adapters/forge/src/main/java/art/arcane/iris/forge/IrisForgeBootstrap.java

@@ -44,12 +44,15 @@ import net.minecraftforge.event.server.ServerStartingEvent;
 import net.minecraftforge.event.server.ServerStoppingEvent;
 import net.minecraftforge.api.distmarker.Dist;
 import net.minecraftforge.common.loot.IGlobalLootModifier;
+import net.minecraftforge.common.util.BlockSnapshot;
+import net.minecraftforge.eventbus.api.listener.Priority;
 import net.minecraftforge.fml.common.Mod;
 import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
 import net.minecraftforge.fml.loading.FMLEnvironment;
 import net.minecraftforge.fml.loading.FMLLoader;
 import net.minecraftforge.registries.DeferredRegister;
 import net.minecraftforge.registries.ForgeRegistries;
+import net.minecraftforge.server.permission.events.PermissionGatherEvent;
 
 import java.util.function.Predicate;
 
@@ -80,6 +83,11 @@ public final class IrisForgeBootstrap {
                 ModdedEngineBootstrap.levelLoaded(level);
             }
         });
+        LevelEvent.Unload.BUS.addListener((LevelEvent.Unload event) -> {
+            if (event.getLevel() instanceof ServerLevel level) {
+                ModdedEngineBootstrap.levelUnloaded(level);
+            }
+        });
         PlayerEvent.PlayerLoggedInEvent.BUS.addListener((PlayerEvent.PlayerLoggedInEvent event) -> {
             if (event.getEntity() instanceof ServerPlayer player) {
                 ModdedProtocolHandler.onPlayerJoin(player);
@@ -96,11 +104,32 @@ public final class IrisForgeBootstrap {
             }
         });
         RegisterCommandsEvent.BUS.addListener((RegisterCommandsEvent event) -> IrisModdedCommands.register(event.getDispatcher()));
+        PermissionGatherEvent.Nodes.BUS.addListener((PermissionGatherEvent.Nodes event) ->
+                event.addNodes(ForgeModdedLoader.TREE_FELLER_PERMISSION));
         BlockEvent.BreakEvent.BUS.addListener((BlockEvent.BreakEvent event) -> {
-            if (event.getLevel() instanceof ServerLevel level && !event.getResult().isDenied()) {
-                ModdedBlockBreakHandler.prepare(level, event.getPos(), event.getState());
+            if (event.getLevel() instanceof ServerLevel level
+                    && event.getPlayer() instanceof ServerPlayer player
+                    && !event.getResult().isDenied()) {
+                ModdedBlockBreakHandler.prepare(level, player, event.getPos(), event.getState());
             }
         });
+        BlockEvent.EntityPlaceEvent.BUS.addListener(Priority.MONITOR, false, (BlockEvent.EntityPlaceEvent event) -> {
+            if (!(event instanceof BlockEvent.EntityMultiPlaceEvent)
+                    && event.getLevel() instanceof ServerLevel level) {
+                ModdedBlockBreakHandler.clearPlacedProvenance(level, event.getPos());
+            }
+        });
+        BlockEvent.EntityMultiPlaceEvent.BUS.addListener(
+                Priority.MONITOR,
+                false,
+                (BlockEvent.EntityMultiPlaceEvent event) -> {
+                    for (BlockSnapshot snapshot : event.getReplacedBlockSnapshots()) {
+                        if (snapshot.getLevel() instanceof ServerLevel level) {
+                            ModdedBlockBreakHandler.clearPlacedProvenance(level, snapshot.getPos());
+                        }
+                    }
+                }
+        );
         PlayerInteractEvent.LeftClickBlock.BUS.addListener((Predicate<PlayerInteractEvent.LeftClickBlock>) (PlayerInteractEvent.LeftClickBlock event) ->
                 ModdedWandService.attackBlock(event.getEntity(), event.getLevel(), event.getHand(), event.getPos()));
         PlayerInteractEvent.RightClickBlock.BUS.addListener((Predicate<PlayerInteractEvent.RightClickBlock>) (PlayerInteractEvent.RightClickBlock event) ->

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

@@ -19,8 +19,11 @@
 package art.arcane.iris.modded;
 
 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.object.IrisBiome;
 import art.arcane.iris.engine.object.IrisBiomeCustom;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.volmlib.util.math.RNG;
 import com.mojang.serialization.MapCodec;
 import net.minecraft.core.Holder;
@@ -51,6 +54,7 @@ final class IrisModdedBiomeSource extends BiomeSource {
     private final ConcurrentHashMap<Long, Holder<Biome>> visibleBiomeCache = new ConcurrentHashMap<>();
     private final ConcurrentHashMap<Long, Holder<Biome>> structureBiomeCache = new ConcurrentHashMap<>();
     private final ConcurrentHashMap<Long, Holder<Biome>> surfaceStructureBiomeCache = new ConcurrentHashMap<>();
+    private final Set<StructureStateBiomeSource> structureStateSources = ConcurrentHashMap.newKeySet();
     private volatile IrisModdedChunkGenerator generator;
     private volatile Set<String> possibleStructureBiomeKeys;
 
@@ -67,6 +71,9 @@ final class IrisModdedBiomeSource extends BiomeSource {
         structureBiomeCache.clear();
         surfaceStructureBiomeCache.clear();
         possibleStructureBiomeKeys = null;
+        for (StructureStateBiomeSource source : structureStateSources) {
+            source.clearCache();
+        }
     }
 
     BiomeSource forStructureState(HolderLookup<StructureSet> structureSets) {
@@ -91,7 +98,9 @@ final class IrisModdedBiomeSource extends BiomeSource {
                 }
             }
         });
-        return new StructureStateBiomeSource(this, Set.copyOf(possible));
+        StructureStateBiomeSource source = new StructureStateBiomeSource(this, Set.copyOf(possible));
+        structureStateSources.add(source);
+        return source;
     }
 
     @Override
@@ -134,10 +143,19 @@ final class IrisModdedBiomeSource extends BiomeSource {
     @Override
     public Holder<Biome> getNoiseBiome(int quartX, int quartY, int quartZ, Climate.Sampler sampler) {
         Engine engine = engineOrNull();
-        if (!isReady(engine)) {
+        if (engine == null) {
             return serializedSource.getNoiseBiome(quartX, quartY, quartZ, sampler);
         }
-        return getNoiseBiome(engine, quartX, quartY, quartZ, sampler);
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_structure_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris structure biome lookup was rejected during an engine transition");
+        }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isReady(engine)) {
+                throw new IllegalStateException("Iris structure biome lookup has no active engine runtime");
+            }
+            return getNoiseBiome(engine, quartX, quartY, quartZ, sampler);
+        }
     }
 
     private Holder<Biome> getNoiseBiome(Engine engine, int quartX, int quartY, int quartZ,
@@ -160,24 +178,46 @@ final class IrisModdedBiomeSource extends BiomeSource {
 
     Holder<Biome> getVisibleNoiseBiome(int quartX, int quartY, int quartZ, Climate.Sampler sampler) {
         Engine engine = engineOrNull();
-        if (!isReady(engine)) {
+        if (engine == null) {
             return serializedSource.getNoiseBiome(quartX, quartY, quartZ, sampler);
         }
-        long key = packNoiseKey(quartX, quartY, quartZ);
-        Holder<Biome> cached = visibleBiomeCache.get(key);
-        if (cached != null) {
-            return cached;
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_visible_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris visible biome lookup was rejected during an engine transition");
         }
-        Holder<Biome> resolved = resolveVisibleBiome(engine, quartX, quartY, quartZ, sampler);
-        Holder<Biome> existing = visibleBiomeCache.putIfAbsent(key, resolved);
-        if (visibleBiomeCache.size() > BIOME_CACHE_MAX) {
-            visibleBiomeCache.clear();
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isReady(engine)) {
+                throw new IllegalStateException("Iris visible biome lookup has no active engine runtime");
+            }
+            long key = packNoiseKey(quartX, quartY, quartZ);
+            Holder<Biome> cached = visibleBiomeCache.get(key);
+            if (cached != null) {
+                return cached;
+            }
+            Holder<Biome> resolved = resolveVisibleBiome(engine, quartX, quartY, quartZ, sampler);
+            Holder<Biome> existing = visibleBiomeCache.putIfAbsent(key, resolved);
+            if (visibleBiomeCache.size() > BIOME_CACHE_MAX) {
+                visibleBiomeCache.clear();
+            }
+            return existing == null ? resolved : existing;
         }
-        return existing == null ? resolved : existing;
     }
 
     boolean isStructureReachable(Holder<Structure> structure) {
-        Set<String> possible = possibleStructureBiomeKeys();
+        Engine engine = engineOrNull();
+        if (engine == null) {
+            return isStructureReachable(structure, possibleStructureBiomeKeys());
+        }
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_structure_reachability");
+        if (lease == null) {
+            throw new IllegalStateException("Iris structure reachability was rejected during an engine transition");
+        }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            return isStructureReachable(structure, possibleStructureBiomeKeys());
+        }
+    }
+
+    private boolean isStructureReachable(Holder<Structure> structure, Set<String> possible) {
         for (Holder<Biome> biome : structure.value().biomes()) {
             String key = holderKey(biome);
             if (isGeneratedBiomeKey(key, possible)) {
@@ -191,26 +231,35 @@ final class IrisModdedBiomeSource extends BiomeSource {
     public Set<Holder<Biome>> getBiomesWithin(int x, int y, int z, int radius, Climate.Sampler sampler) {
         int minQuartY = QuartPos.fromBlock(y - radius);
         Engine engine = engineOrNull();
-        if (!isReady(engine)) {
+        if (engine == null) {
             return super.getBiomesWithin(x, y, z, radius, sampler);
         }
-        boolean monumentQuery = isMonumentSurfaceBiomeQuery(
-                y, radius, engine.getMinHeight(), engine.getDimension().getFluidHeight());
-        if (!monumentQuery && !isGuaranteedSurfaceBiome(minQuartY, engine.getMinHeight())) {
-            return super.getBiomesWithin(x, y, z, radius, sampler);
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_biomes_within");
+        if (lease == null) {
+            throw new IllegalStateException("Iris biome radius lookup was rejected during an engine transition");
         }
-        int minQuartX = QuartPos.fromBlock(x - radius);
-        int maxQuartX = QuartPos.fromBlock(x + radius);
-        int minQuartZ = QuartPos.fromBlock(z - radius);
-        int maxQuartZ = QuartPos.fromBlock(z + radius);
-        int columns = (maxQuartX - minQuartX + 1) * (maxQuartZ - minQuartZ + 1);
-        Set<Holder<Biome>> biomes = new HashSet<>(columns);
-        for (int quartZ = minQuartZ; quartZ <= maxQuartZ; quartZ++) {
-            for (int quartX = minQuartX; quartX <= maxQuartX; quartX++) {
-                biomes.add(getSurfaceStructureBiome(engine, quartX, quartZ, sampler));
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isReady(engine)) {
+                throw new IllegalStateException("Iris biome radius lookup has no active engine runtime");
             }
+            boolean monumentQuery = isMonumentSurfaceBiomeQuery(
+                    y, radius, engine.getMinHeight(), engine.getDimension().getFluidHeight());
+            if (!monumentQuery && !isGuaranteedSurfaceBiome(minQuartY, engine.getMinHeight())) {
+                return super.getBiomesWithin(x, y, z, radius, sampler);
+            }
+            int minQuartX = QuartPos.fromBlock(x - radius);
+            int maxQuartX = QuartPos.fromBlock(x + radius);
+            int minQuartZ = QuartPos.fromBlock(z - radius);
+            int maxQuartZ = QuartPos.fromBlock(z + radius);
+            int columns = (maxQuartX - minQuartX + 1) * (maxQuartZ - minQuartZ + 1);
+            Set<Holder<Biome>> biomes = new HashSet<>(columns);
+            for (int quartZ = minQuartZ; quartZ <= maxQuartZ; quartZ++) {
+                for (int quartX = minQuartX; quartX <= maxQuartX; quartX++) {
+                    biomes.add(getSurfaceStructureBiome(engine, quartX, quartZ, sampler));
+                }
+            }
+            return biomes;
         }
-        return biomes;
     }
 
     private Holder<Biome> getSurfaceStructureBiome(Engine engine, int quartX, int quartZ,
@@ -338,28 +387,37 @@ final class IrisModdedBiomeSource extends BiomeSource {
             throw new IllegalStateException("Iris structure biome source is not bound to its generator");
         }
         Engine engine = current.awaitStructureEngine();
-        Registry<Biome> registry = biomeRegistry();
-        if (registry == null) {
-            throw new IllegalStateException("Iris structure biome lookup has no biome registry");
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_structure_state_biome");
+        if (lease == null) {
+            throw new IllegalStateException("Iris structure biome lookup was rejected during an engine transition");
         }
-        IrisBiome irisBiome;
-        if (isGuaranteedSurfaceBiome(quartY, engine.getMinHeight())) {
-            irisBiome = engine.getComplex().getTrueBiomeStream().get(quartX << 2, quartZ << 2);
-        } else {
-            BiomeResolution resolution = resolveBiomeResolution(engine, quartX, quartY, quartZ);
-            irisBiome = resolution == null ? null : resolution.irisBiome();
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isReady(engine)) {
+                throw new IllegalStateException("Iris structure biome lookup has no active engine runtime");
+            }
+            Registry<Biome> registry = biomeRegistry();
+            if (registry == null) {
+                throw new IllegalStateException("Iris structure biome lookup has no biome registry");
+            }
+            IrisBiome irisBiome;
+            if (isGuaranteedSurfaceBiome(quartY, engine.getMinHeight())) {
+                irisBiome = engine.getComplex().getTrueBiomeStream().get(quartX << 2, quartZ << 2);
+            } else {
+                BiomeResolution resolution = resolveBiomeResolution(engine, quartX, quartY, quartZ);
+                irisBiome = resolution == null ? null : resolution.irisBiome();
+            }
+            if (irisBiome == null) {
+                throw new IllegalStateException("Iris returned no structure biome at quart "
+                        + quartX + "," + quartY + "," + quartZ);
+            }
+            String derivativeKey = irisBiome.getStructureDerivativeKey();
+            Holder<Biome> resolved = resolveHolder(registry, derivativeKey);
+            if (resolved == null) {
+                throw new IllegalStateException("Iris structure biome derivative '" + derivativeKey
+                        + "' is not registered at quart " + quartX + "," + quartY + "," + quartZ);
+            }
+            return resolved;
         }
-        if (irisBiome == null) {
-            throw new IllegalStateException("Iris returned no structure biome at quart "
-                    + quartX + "," + quartY + "," + quartZ);
-        }
-        String derivativeKey = irisBiome.getStructureDerivativeKey();
-        Holder<Biome> resolved = resolveHolder(registry, derivativeKey);
-        if (resolved == null) {
-            throw new IllegalStateException("Iris structure biome derivative '" + derivativeKey
-                    + "' is not registered at quart " + quartX + "," + quartY + "," + quartZ);
-        }
-        return resolved;
     }
 
     static long biomeResolutionSeed(long worldSeed, int blockX, int blockY, int blockZ) {
@@ -403,6 +461,21 @@ final class IrisModdedBiomeSource extends BiomeSource {
         return current == null ? null : current.structureEngineOrNull();
     }
 
+    private GenerationSessionLease tryAcquireGenerationLease(Engine engine, String operation) {
+        if (engine == null || engine.isClosed()) {
+            return null;
+        }
+        try {
+            return engine.acquireGenerationLease(operation);
+        } catch (GenerationSessionException e) {
+            if (engine.isClosing() || e.isExpectedTeardown()) {
+                return null;
+            }
+            throw new IllegalStateException("Iris biome source could not acquire generation session for "
+                    + operation + ".", e);
+        }
+    }
+
     private Set<String> possibleStructureBiomeKeys() {
         Set<String> cached = possibleStructureBiomeKeys;
         if (cached != null) {
@@ -429,24 +502,33 @@ final class IrisModdedBiomeSource extends BiomeSource {
             return Set.of();
         }
         Engine engine = current.structureEngineOrNull();
-        if (!isReady(engine)) {
+        if (engine == null) {
             return current.configuredStructureBiomeKeys();
         }
-        LinkedHashSet<String> possible = new LinkedHashSet<>();
-        String namespace = engine.getDimension().getLoadKey().toLowerCase(Locale.ROOT);
-        for (IrisBiome irisBiome : engine.getAllBiomes()) {
-            String derivative = normalizeKey(irisBiome.getStructureDerivativeKey());
-            if (derivative != null) {
-                possible.add(derivative);
-            }
-            if (!irisBiome.isCustom()) {
-                continue;
-            }
-            for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
-                possible.add(namespace + ":" + customBiome.getId().toLowerCase(Locale.ROOT));
-            }
+        GenerationSessionLease lease = tryAcquireGenerationLease(engine, "modded_structure_biome_keys");
+        if (lease == null) {
+            throw new IllegalStateException("Iris structure biome key lookup was rejected during an engine transition");
+        }
+        try (lease; IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!isReady(engine)) {
+                throw new IllegalStateException("Iris structure biome key lookup has no active engine runtime");
+            }
+            LinkedHashSet<String> possible = new LinkedHashSet<>();
+            String namespace = engine.getDimension().getLoadKey().toLowerCase(Locale.ROOT);
+            for (IrisBiome irisBiome : engine.getAllBiomes()) {
+                String derivative = normalizeKey(irisBiome.getStructureDerivativeKey());
+                if (derivative != null) {
+                    possible.add(derivative);
+                }
+                if (!irisBiome.isCustom()) {
+                    continue;
+                }
+                for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
+                    possible.add(namespace + ":" + customBiome.getId().toLowerCase(Locale.ROOT));
+                }
+            }
+            return Set.copyOf(possible);
         }
-        return Set.copyOf(possible);
     }
 
     private static Set<String> registeredBiomeKeys(Registry<Biome> registry) {
@@ -517,6 +599,10 @@ final class IrisModdedBiomeSource extends BiomeSource {
             this.possibleBiomes = possibleBiomes;
         }
 
+        private void clearCache() {
+            resolvedBiomes.clear();
+        }
+
         @Override
         protected MapCodec<? extends BiomeSource> codec() {
             throw new UnsupportedOperationException("Structure state biome sources are not serializable");

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

@@ -22,6 +22,7 @@ import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.pack.PackValidationRegistry;
 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.NativeStructureGenerationPolicy;
 import art.arcane.iris.engine.object.IrisBiome;
@@ -37,6 +38,7 @@ import art.arcane.iris.nativegen.NativeStructurePostProcessor;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.spi.PlatformBiome;
 import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.iris.util.project.hunk.Hunk;
 import art.arcane.volmlib.util.math.RNG;
 import com.mojang.datafixers.util.Pair;
@@ -185,6 +187,7 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     private final ConcurrentHashMap<NativeStructureStartKey, Integer> worldCheckStructureShifts = new ConcurrentHashMap<>();
     private final AtomicBoolean announced = new AtomicBoolean(false);
     private volatile boolean vanillaSpawnBiomesInitialized;
+    private volatile boolean unloading;
     private volatile Engine engine;
     private volatile String activePack;
     private volatile String activeDimensionKey;
@@ -221,6 +224,7 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     synchronized void repointAndBind(ServerLevel level, String pack, String packDimensionKey, long seed) {
+        requireBindingAllowed();
         if (level.getChunkSource().getGenerator() != this) {
             throw new IllegalArgumentException("ServerLevel does not use Iris generator '" + dimensionKey + "'");
         }
@@ -258,11 +262,13 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     public synchronized void unbindEngine() {
+        unloading = true;
         ServerLevel level = boundLevel();
         unbindEngine(level);
     }
 
     synchronized void unbindEngine(ServerLevel level) {
+        unloading = true;
         if (level != null) {
             ModdedWorldEngines.evictOrThrow(level);
         }
@@ -322,13 +328,16 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
                                                                      BlockPos pos, int radius,
                                                                      boolean findUnexplored) {
         Engine current = engine();
-        Pair<BlockPos, Holder<Structure>> irisPlaced = findNearestIrisStructure(
-                level, holders, pos, Math.max(1, radius), findUnexplored, current);
-        HolderSet<Structure> reachable = 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);
+        try (GenerationSessionLease lease = requireGenerationLease(current, "modded_structure_locate");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            Pair<BlockPos, Holder<Structure>> irisPlaced = findNearestIrisStructure(
+                    level, holders, pos, Math.max(1, radius), findUnexplored, current);
+            HolderSet<Structure> reachable = 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);
+        }
     }
 
     public boolean isNativeStructureReachable(Holder<Structure> structure) {
@@ -412,8 +421,10 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     private Engine engine() {
+        requireBindingAllowed();
         Engine cached = engine;
-        if (cached != null) {
+        requireCompletedShutdown(cached);
+        if (cached != null && !cached.isClosed()) {
             return cached;
         }
         ServerLevel level = boundLevel();
@@ -423,14 +434,17 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         return bindEngine(level);
     }
 
-    void bindLevel(ServerLevel level) {
+    synchronized void bindLevel(ServerLevel level) {
         if (level.getChunkSource().getGenerator() != this) {
             throw new IllegalArgumentException("ServerLevel does not use Iris generator '" + dimensionKey + "'");
         }
+        requireCompletedShutdown(engine);
+        unloading = false;
         bindEngine(level);
     }
 
     private Engine bindEngine(ServerLevel level) {
+        requireBindingAllowed();
         try {
             requireGlobalStructureGeneration(
                     level.getServer().getWorldGenSettings().options().generateStructures(), dimensionKey);
@@ -439,18 +453,22 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
             throw error;
         }
         Engine cached = engine;
+        requireCompletedShutdown(cached);
         if (cached != null && !cached.isClosed() && cached.getComplex() != null) {
             engineBinding.complete(cached);
             return cached;
         }
         synchronized (this) {
+            requireBindingAllowed();
             Engine existing = engine;
+            requireCompletedShutdown(existing);
             if (existing != null && !existing.isClosed() && existing.getComplex() != null) {
                 engineBinding.complete(existing);
                 return existing;
             }
             try {
                 Engine created = ModdedWorldEngines.get(level, activePack, activeDimensionKey, seedOverride);
+                requireCompletedShutdown(created);
                 if (created.isClosed() || created.getComplex() == null) {
                     throw new IllegalStateException("Iris generator '" + dimensionKey
                             + "' created an engine without a ready biome complex");
@@ -473,6 +491,19 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         }
     }
 
+    private void requireCompletedShutdown(Engine current) {
+        if (current != null && current.isClosing() && !current.isClosed()) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey
+                    + "' cannot bind while its previous engine shutdown remains incomplete");
+        }
+    }
+
+    private void requireBindingAllowed() {
+        if (unloading) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey + "' is unloading and cannot bind an engine");
+        }
+    }
+
     static void requireGlobalStructureGeneration(boolean enabled, String dimensionKey) {
         if (enabled) {
             return;
@@ -483,8 +514,10 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     private Engine engineOrNull() {
+        requireBindingAllowed();
         Engine cached = engine;
-        if (cached != null) {
+        requireCompletedShutdown(cached);
+        if (cached != null && !cached.isClosed()) {
             return cached;
         }
         try {
@@ -495,8 +528,10 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     Engine structureEngineOrNull() {
+        requireBindingAllowed();
         engineBinding.throwIfFailed(dimensionKey);
         Engine cached = engine;
+        requireCompletedShutdown(cached);
         if (cached != null && !cached.isClosed() && cached.getComplex() != null) {
             return cached;
         }
@@ -505,11 +540,14 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     Engine awaitStructureEngine() {
+        requireBindingAllowed();
         Engine current = engine;
+        requireCompletedShutdown(current);
         if (current != null && !current.isClosed() && current.getComplex() != null) {
             return current;
         }
         Engine bound = engineBinding.await(dimensionKey);
+        requireCompletedShutdown(bound);
         if (bound.isClosed() || bound.getComplex() == null) {
             throw new IllegalStateException("Iris generator '" + dimensionKey
                     + "' completed bootstrap without a ready biome complex");
@@ -518,7 +556,9 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     private Engine requireDataQueryEngine(String operation) {
+        requireBindingAllowed();
         Engine current = engine;
+        requireCompletedShutdown(current);
         if (current != null && !current.isClosed() && current.getComplex() != null) {
             return current;
         }
@@ -561,18 +601,21 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
                 return configuredStructureBiomeKeys;
             }
             Engine current = engine;
-            Iterable<IrisBiome> biomes;
-            String namespace;
-            if (current != null && !current.isClosed()) {
-                biomes = current.getAllBiomes();
-                namespace = current.getDimension().getLoadKey();
-            } else {
-                ConfiguredPack configured = configuredPack();
-                Set<String> resolved = collectConfiguredBiomeKeys(configured.dimension(), configured.data());
-                configuredStructureBiomeKeys = resolved;
-                return resolved;
+            if (current != null && !current.isClosed() && !current.isClosing()) {
+                try (GenerationSessionLease lease = current.acquireGenerationLease("modded_configured_biome_keys");
+                     IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+                    Set<String> resolved = collectConfiguredBiomeKeys(
+                            current.getAllBiomes(), current.getDimension().getLoadKey());
+                    configuredStructureBiomeKeys = resolved;
+                    return resolved;
+                } catch (GenerationSessionException e) {
+                    if (!current.isClosing() && !e.isExpectedTeardown()) {
+                        throw new IllegalStateException("Iris configured biome lookup could not acquire its engine runtime.", e);
+                    }
+                }
             }
-            Set<String> resolved = collectConfiguredBiomeKeys(biomes, namespace);
+            ConfiguredPack configured = configuredPack();
+            Set<String> resolved = collectConfiguredBiomeKeys(configured.dimension(), configured.data());
             configuredStructureBiomeKeys = resolved;
             return resolved;
         }
@@ -654,7 +697,8 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     }
 
     public Engine engineIfBound() {
-        return engine;
+        Engine current = engine;
+        return unloading || current == null || current.isClosing() || current.isClosed() ? null : current;
     }
 
     public Engine commandEngine() {
@@ -710,23 +754,26 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
             return;
         }
 
-        String namespace = current.getDimension().getLoadKey().toLowerCase(Locale.ROOT);
-        for (IrisBiome irisBiome : current.getDimension().getReachableBiomes(current)) {
-            if (irisBiome == null || !irisBiome.isCustom()) {
-                continue;
-            }
-            Holder<Biome> vanillaHolder = resolveBiomeHolder(registry, irisBiome.getVanillaDerivativeKey());
-            if (vanillaHolder == null) {
-                continue;
-            }
-            for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
-                Holder<Biome> customHolder = resolveBiomeHolder(registry, namespace + ":" + customBiome.getId());
-                if (customHolder != null) {
-                    vanillaSpawnBiomes.putIfAbsent(customHolder.value(), vanillaHolder);
+        try (GenerationSessionLease lease = requireGenerationLease(current, "modded_spawn_biomes");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            String namespace = current.getDimension().getLoadKey().toLowerCase(Locale.ROOT);
+            for (IrisBiome irisBiome : current.getDimension().getReachableBiomes(current)) {
+                if (irisBiome == null || !irisBiome.isCustom()) {
+                    continue;
+                }
+                Holder<Biome> vanillaHolder = resolveBiomeHolder(registry, irisBiome.getVanillaDerivativeKey());
+                if (vanillaHolder == null) {
+                    continue;
+                }
+                for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
+                    Holder<Biome> customHolder = resolveBiomeHolder(registry, namespace + ":" + customBiome.getId());
+                    if (customHolder != null) {
+                        vanillaSpawnBiomes.putIfAbsent(customHolder.value(), vanillaHolder);
+                    }
                 }
             }
+            vanillaSpawnBiomesInitialized = true;
         }
-        vanillaSpawnBiomesInitialized = true;
     }
 
     private Holder<Biome> resolveBiomeHolder(Registry<Biome> registry, String key) {
@@ -750,8 +797,12 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     @Override
     public CompletableFuture<ChunkAccess> createBiomes(RandomState randomState, Blender blender,
                                                        StructureManager structureManager, ChunkAccess chunk) {
-        chunk.fillBiomesFromNoise(structureBiomeSource::getVisibleNoiseBiome, randomState.sampler());
-        return CompletableFuture.completedFuture(chunk);
+        Engine current = engine();
+        try (GenerationSessionLease lease = requireGenerationLease(current, "modded_create_biomes");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            chunk.fillBiomesFromNoise(structureBiomeSource::getVisibleNoiseBiome, randomState.sampler());
+            return CompletableFuture.completedFuture(chunk);
+        }
     }
 
     @Override
@@ -759,36 +810,46 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         Engine generationEngine = engine();
         ChunkPos pos = chunk.getPos();
         lastChunkGenAt = System.currentTimeMillis();
-        if (announced.compareAndSet(false, true)) {
-            LOGGER.info("Iris generating {} through IrisModdedChunkGenerator (dim={} first chunk {},{})",
-                    dimensionKey, generationEngine.getDimension().getLoadKey(), pos.x(), pos.z());
-        }
         LOGGER.debug("Iris generating chunk {},{}", pos.x(), pos.z());
 
-        int dimMinY = generationEngine.getMinHeight();
-        int dimMaxY = generationEngine.getMaxHeight();
-        int height = dimMaxY - dimMinY;
         PlatformBlockState air = IrisPlatforms.get().registries().air();
 
         if (PARALLEL_CHUNK_SYSTEM) {
             return CompletableFuture.completedFuture(
-                    generateTerrain(chunk, generationEngine, pos, dimMinY, height, air));
+                    generateTerrain(chunk, generationEngine, pos, air));
         }
         return CompletableFuture.supplyAsync(
-                () -> generateTerrain(chunk, generationEngine, pos, dimMinY, height, air),
+                () -> generateTerrain(chunk, generationEngine, pos, air),
                 genPool);
     }
 
     private ChunkAccess generateTerrain(ChunkAccess chunk, Engine generationEngine, ChunkPos pos,
-                                        int dimMinY, int height, PlatformBlockState air) {
-        ModdedBlockBuffer blocks = new ModdedBlockBuffer(height, air);
-        Hunk<PlatformBiome> biomes = Hunk.newArrayHunk(16, height, 16);
-        try {
+                                        PlatformBlockState air) {
+        try (GenerationSessionLease lease = generationEngine.acquireGenerationLease("modded_chunk_pipeline");
+             IrisContext.Scope ignored = IrisContext.open(generationEngine, lease.sessionId(), null)) {
+            if (announced.compareAndSet(false, true)) {
+                LOGGER.info("Iris generating {} through IrisModdedChunkGenerator (dim={} first chunk {},{})",
+                        dimensionKey, generationEngine.getDimension().getLoadKey(), pos.x(), pos.z());
+            }
+            int dimMinY = generationEngine.getMinHeight();
+            int dimMaxY = generationEngine.getMaxHeight();
+            int height = dimMaxY - dimMinY;
+            ModdedBlockBuffer blocks = new ModdedBlockBuffer(height, air);
+            Hunk<PlatformBiome> biomes = Hunk.newArrayHunk(16, height, 16);
             generationEngine.generate(pos.getMinBlockX(), pos.getMinBlockZ(), blocks, biomes, false);
+
+            writeBlocks(chunk, blocks, dimMinY, height);
+            writeTerrainHeightmaps(chunk, generationEngine, pos, height);
+            Heightmap.primeHeightmaps(chunk, EnumSet.of(
+                    Heightmap.Types.MOTION_BLOCKING,
+                    Heightmap.Types.MOTION_BLOCKING_NO_LEAVES));
+            ModdedWorldManager.enqueueGenerated(generationEngine, pos.x(), pos.z());
+            return chunk;
         } catch (GenerationSessionException e) {
-            if (e.isExpectedTeardown()) {
+            if (generationEngine.isClosing() || e.isExpectedTeardown()) {
                 LOGGER.debug("Iris chunk {},{} skipped: engine sealed for hotload/teardown", pos.x(), pos.z());
-                return chunk;
+                throw new IllegalStateException(
+                        "Iris chunk generation was rejected during an engine transition.", e);
             }
             LOGGER.error("Iris failed to generate chunk {},{}", pos.x(), pos.z(), e);
             throw new IllegalStateException("Iris generation failed for chunk " + pos.x() + "," + pos.z(), e);
@@ -796,14 +857,6 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
             LOGGER.error("Iris failed to generate chunk {},{}", pos.x(), pos.z(), e);
             throw new IllegalStateException("Iris generation failed for chunk " + pos.x() + "," + pos.z(), e);
         }
-
-        writeBlocks(chunk, blocks, dimMinY, height);
-        writeTerrainHeightmaps(chunk, generationEngine, pos, height);
-        Heightmap.primeHeightmaps(chunk, EnumSet.of(
-                Heightmap.Types.MOTION_BLOCKING,
-                Heightmap.Types.MOTION_BLOCKING_NO_LEAVES));
-        ModdedWorldManager.enqueueGenerated(generationEngine, pos.x(), pos.z());
-        return chunk;
     }
 
     private void writeTerrainHeightmaps(ChunkAccess chunk, Engine generationEngine, ChunkPos pos, int height) {
@@ -885,20 +938,31 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
 
     @Override
     public void applyBiomeDecoration(WorldGenLevel level, ChunkAccess chunk, StructureManager structureManager) {
-        placeVanillaStructures(level, chunk, structureManager);
+        Engine current = engine();
+        try (GenerationSessionLease lease = requireGenerationLease(current, "modded_biome_decoration");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            placeVanillaStructures(level, chunk, structureManager);
+        }
     }
 
     @Override
     public void createStructures(RegistryAccess registryAccess, ChunkGeneratorStructureState structureState, StructureManager structureManager, ChunkAccess chunk, StructureTemplateManager templateManager, ResourceKey<Level> levelKey) {
         Engine current = engine();
-        Map<Structure, StructureStart> previousStarts = new HashMap<>(chunk.getAllStarts());
-        super.createStructures(registryAccess, structureState, structureManager, chunk, templateManager, levelKey);
-        adjustGeneratedStructures(registryAccess, chunk, previousStarts, current);
+        try (GenerationSessionLease lease = requireGenerationLease(current, "modded_create_structures");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            Map<Structure, StructureStart> previousStarts = new HashMap<>(chunk.getAllStarts());
+            super.createStructures(registryAccess, structureState, structureManager, chunk, templateManager, levelKey);
+            adjustGeneratedStructures(registryAccess, chunk, previousStarts, current);
+        }
     }
 
     @Override
     public void createReferences(WorldGenLevel level, StructureManager structureManager, ChunkAccess chunk) {
-        super.createReferences(level, structureManager, chunk);
+        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);
+        }
     }
 
     private void adjustGeneratedStructures(RegistryAccess registryAccess, ChunkAccess chunk,
@@ -1168,7 +1232,12 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     public int getBaseHeight(int x, int z, Heightmap.Types type, LevelHeightAccessor heightAccessor, RandomState randomState) {
         Engine current = requireDataQueryEngine("base height");
         boolean ignoreFluid = !type.isOpaque().test(Blocks.WATER.defaultBlockState());
-        return heightAccessor.getMinY() + current.getHeight(x, z, ignoreFluid) + 1;
+        try (GenerationSessionLease lease = current.acquireGenerationLease("modded_base_height");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            return heightAccessor.getMinY() + current.getHeight(x, z, ignoreFluid) + 1;
+        } catch (GenerationSessionException e) {
+            throw new IllegalStateException("Iris base height query could not acquire its engine runtime.", e);
+        }
     }
 
     @Override
@@ -1176,17 +1245,30 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         int minY = heightAccessor.getMinY();
         BlockState[] states = new BlockState[heightAccessor.getHeight()];
         Engine current = requireDataQueryEngine("base column");
-        BlockState airState = Blocks.AIR.defaultBlockState();
-        int surface = current.getHeight(x, z, true);
-        int fluid = current.getHeight(x, z, false);
-        BlockState stone = Blocks.STONE.defaultBlockState();
-        BlockState water = Blocks.WATER.defaultBlockState();
-        int solidEnd = Math.max(0, Math.min(states.length, surface + 1));
-        int fluidEnd = Math.max(solidEnd, Math.max(0, Math.min(states.length, fluid + 1)));
-        Arrays.fill(states, 0, solidEnd, stone);
-        Arrays.fill(states, solidEnd, fluidEnd, water);
-        Arrays.fill(states, fluidEnd, states.length, airState);
-        return new NoiseColumn(minY, states);
+        try (GenerationSessionLease lease = current.acquireGenerationLease("modded_base_column");
+             IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
+            BlockState airState = Blocks.AIR.defaultBlockState();
+            int surface = current.getHeight(x, z, true);
+            int fluid = current.getHeight(x, z, false);
+            BlockState stone = Blocks.STONE.defaultBlockState();
+            BlockState water = Blocks.WATER.defaultBlockState();
+            int solidEnd = Math.max(0, Math.min(states.length, surface + 1));
+            int fluidEnd = Math.max(solidEnd, Math.max(0, Math.min(states.length, fluid + 1)));
+            Arrays.fill(states, 0, solidEnd, stone);
+            Arrays.fill(states, solidEnd, fluidEnd, water);
+            Arrays.fill(states, fluidEnd, states.length, airState);
+            return new NoiseColumn(minY, states);
+        } catch (GenerationSessionException e) {
+            throw new IllegalStateException("Iris base column query could not acquire its engine runtime.", e);
+        }
+    }
+
+    private GenerationSessionLease requireGenerationLease(Engine current, String operation) {
+        try {
+            return current.acquireGenerationLease(operation);
+        } catch (GenerationSessionException exception) {
+            throw new IllegalStateException("Iris " + operation + " could not acquire its engine runtime.", exception);
+        }
     }
 
     @Override

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

@@ -21,6 +21,7 @@ package art.arcane.iris.modded;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.engine.framework.Engine;
 import art.arcane.iris.engine.framework.LootResolver;
+import art.arcane.iris.engine.framework.TreeBlockMaterial;
 import art.arcane.iris.engine.object.IrisBiome;
 import art.arcane.iris.engine.object.IrisBlockData;
 import art.arcane.iris.engine.object.IrisBlockDrops;
@@ -28,11 +29,13 @@ import art.arcane.iris.engine.object.IrisLoot;
 import art.arcane.iris.engine.object.IrisMarker;
 import art.arcane.iris.engine.object.IrisRegion;
 import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.math.RNG;
 import art.arcane.volmlib.util.matter.MatterMarker;
 import net.minecraft.core.BlockPos;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.util.Mth;
 import net.minecraft.util.RandomSource;
 import net.minecraft.world.entity.EntityTypes;
@@ -43,6 +46,7 @@ import net.minecraft.world.level.chunk.ChunkGenerator;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.List;
 import java.util.concurrent.ConcurrentHashMap;
 
 public final class ModdedBlockBreakHandler {
@@ -52,12 +56,24 @@ public final class ModdedBlockBreakHandler {
     private ModdedBlockBreakHandler() {
     }
 
-    public static void prepare(ServerLevel level, BlockPos position, BlockState brokenState) {
+    public static void prepare(
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState brokenState
+    ) {
+        if (ModdedTreeFellerService.isBreakProbe()) {
+            return;
+        }
         if (engineFor(level) == null) {
             return;
         }
         BreakKey key = new BreakKey(level, position.asLong());
-        PendingBreak pending = new PendingBreak(brokenState);
+        ModdedTreeFellerService treeFeller = treeFellerService();
+        ModdedTreeFellerService.PreparedOrigin preparedOrigin = treeFeller == null
+                ? null
+                : treeFeller.prepare(level, player, position, brokenState);
+        PendingBreak pending = new PendingBreak(brokenState, preparedOrigin);
         PENDING.put(key, pending);
         ModdedScheduler scheduler = ModdedEngineBootstrap.schedulerOrNull();
         if (scheduler != null) {
@@ -69,11 +85,15 @@ public final class ModdedBlockBreakHandler {
         PENDING.clear();
     }
 
+    public static void cancel(ServerLevel level, BlockPos position) {
+        PENDING.remove(new BreakKey(level, position.asLong()));
+    }
+
     public static Result complete(ServerLevel level, BlockPos position, BlockState fallbackState) {
         BreakKey key = new BreakKey(level, position.asLong());
         PendingBreak pending = PENDING.remove(key);
-        BlockState brokenState = pending == null ? fallbackState : pending.brokenState();
-        return evaluateSafely(level, position, brokenState);
+        PendingBreak resolved = pending == null ? new PendingBreak(fallbackState, null) : pending;
+        return evaluateSafely(level, position, resolved);
     }
 
     public static Result completePrepared(ServerLevel level, BlockPos position) {
@@ -82,7 +102,7 @@ public final class ModdedBlockBreakHandler {
         if (pending == null || level.getBlockState(position).equals(pending.brokenState())) {
             return null;
         }
-        return PENDING.remove(key, pending) ? evaluateSafely(level, position, pending.brokenState()) : null;
+        return PENDING.remove(key, pending) ? evaluateSafely(level, position, pending) : null;
     }
 
     public static void spawn(ServerLevel level, BlockPos position, KList<ItemStack> drops) {
@@ -115,13 +135,15 @@ public final class ModdedBlockBreakHandler {
         if (level.getBlockState(position).equals(pending.brokenState())) {
             return;
         }
-        Result result = evaluateSafely(level, position, pending.brokenState());
-        spawn(level, position, result.drops());
+        Result result = evaluateSafely(level, position, pending);
+        if (!result.routeCombinedDrops(List.of())) {
+            spawn(level, position, result.drops());
+        }
     }
 
-    private static Result evaluateSafely(ServerLevel level, BlockPos position, BlockState brokenState) {
+    private static Result evaluateSafely(ServerLevel level, BlockPos position, PendingBreak pending) {
         try {
-            return evaluate(level, position, brokenState);
+            return evaluate(level, position, pending);
         } catch (Throwable error) {
             LOGGER.error("Iris block-break processing failed at {},{},{} in {}", position.getX(), position.getY(), position.getZ(),
                     level.dimension().identifier(), error);
@@ -129,13 +151,56 @@ public final class ModdedBlockBreakHandler {
         }
     }
 
-    private static Result evaluate(ServerLevel level, BlockPos position, BlockState brokenState) {
+    private static Result evaluate(ServerLevel level, BlockPos position, PendingBreak pending) {
         Engine engine = engineFor(level);
         if (engine == null || engine.isClosed()) {
             return Result.empty();
         }
 
         removeMarker(engine, position);
+        Result drops = evaluateDrops(level, position, pending.brokenState(), engine);
+        ModdedTreeFellerService treeFeller = treeFellerService();
+        ModdedTreeFellerService.OriginDropRoute route = treeFeller == null || pending.preparedOrigin() == null
+                ? null
+                : treeFeller.completeOrigin(pending.preparedOrigin());
+        if (route == null) {
+            clearTreeProvenance(engine, position);
+        }
+        return drops.withRoute(route);
+    }
+
+    public static Result evaluateManagedDrops(ServerLevel level, BlockPos position, BlockState brokenState) {
+        Engine engine = engineFor(level);
+        if (engine == null || engine.isClosed()) {
+            return Result.empty();
+        }
+        try {
+            return evaluateDrops(level, position, brokenState, engine);
+        } catch (Throwable error) {
+            LOGGER.error("Iris managed block-drop processing failed at {},{},{} in {}", position.getX(), position.getY(), position.getZ(),
+                    level.dimension().identifier(), error);
+            return Result.empty();
+        }
+    }
+
+    public static void completeManagedBreak(ServerLevel level, BlockPos position) {
+        Engine engine = engineFor(level);
+        if (engine != null && !engine.isClosed()) {
+            removeMarker(engine, position);
+            clearTreeProvenance(engine, position);
+        }
+    }
+
+    public static void clearPlacedProvenance(ServerLevel level, BlockPos position) {
+        completeManagedBreak(level, position);
+    }
+
+    private static Result evaluateDrops(
+            ServerLevel level,
+            BlockPos position,
+            BlockState brokenState,
+            Engine engine
+    ) {
         KList<IrisBlockDrops> providers = providers(engine, position, brokenState);
         if (providers.isEmpty()) {
             return Result.empty();
@@ -155,7 +220,7 @@ public final class ModdedBlockBreakHandler {
                 }
             }
         }
-        return new Result(drops, replaceVanillaDrops);
+        return new Result(drops, replaceVanillaDrops, null);
     }
 
     private static void removeMarker(Engine engine, BlockPos position) {
@@ -174,6 +239,12 @@ public final class ModdedBlockBreakHandler {
         }
     }
 
+    private static void clearTreeProvenance(Engine engine, BlockPos position) {
+        int mantleY = position.getY() - engine.getMinHeight();
+        engine.getMantle().getMantle().remove(position.getX(), mantleY, position.getZ(), String.class);
+        engine.getMantle().getMantle().remove(position.getX(), mantleY, position.getZ(), TreeBlockMaterial.class);
+    }
+
     private static KList<IrisBlockDrops> providers(Engine engine, BlockPos position, BlockState brokenState) {
         KList<IrisBlockDrops> providers = new KList<>();
         IrisData data = engine.getData();
@@ -227,7 +298,7 @@ public final class ModdedBlockBreakHandler {
         return exact ? configuredState.equals(brokenState) : configuredState.getBlock() == brokenState.getBlock();
     }
 
-    private static Engine engineFor(ServerLevel level) {
+    public static Engine engineFor(ServerLevel level) {
         ChunkGenerator generator = level.getChunkSource().getGenerator();
         if (!(generator instanceof IrisModdedChunkGenerator irisGenerator)) {
             return null;
@@ -244,15 +315,72 @@ public final class ModdedBlockBreakHandler {
         }
     }
 
-    public record Result(KList<ItemStack> drops, boolean replaceVanillaDrops) {
+    private static ModdedTreeFellerService treeFellerService() {
+        return ModdedEngineBootstrap.services().service(ModdedTreeFellerService.class);
+    }
+
+    public static final class Result {
+        private final KList<ItemStack> drops;
+        private final boolean replaceVanillaDrops;
+        private final ModdedTreeFellerService.OriginDropRoute route;
+
+        private Result(
+                KList<ItemStack> drops,
+                boolean replaceVanillaDrops,
+                ModdedTreeFellerService.OriginDropRoute route
+        ) {
+            this.drops = drops;
+            this.replaceVanillaDrops = replaceVanillaDrops;
+            this.route = route;
+        }
+
+        public KList<ItemStack> drops() {
+            return drops;
+        }
+
+        public boolean replaceVanillaDrops() {
+            return replaceVanillaDrops;
+        }
+
+        public boolean routeCombinedDrops(Iterable<ItemStack> vanillaDrops) {
+            if (route == null) {
+                return false;
+            }
+            return route.route(combinedDrops(vanillaDrops));
+        }
+
+        public KList<ItemStack> combinedDrops(Iterable<ItemStack> vanillaDrops) {
+            KList<ItemStack> combined = new KList<>();
+            if (!replaceVanillaDrops) {
+                for (ItemStack stack : vanillaDrops) {
+                    if (stack != null && !stack.isEmpty()) {
+                        combined.add(stack.copy());
+                    }
+                }
+            }
+            for (ItemStack stack : drops) {
+                if (stack != null && !stack.isEmpty()) {
+                    combined.add(stack.copy());
+                }
+            }
+            return combined;
+        }
+
+        private Result withRoute(ModdedTreeFellerService.OriginDropRoute route) {
+            return new Result(drops, replaceVanillaDrops, route);
+        }
+
         private static Result empty() {
-            return new Result(new KList<>(), false);
+            return new Result(new KList<>(), false, null);
         }
     }
 
     private record BreakKey(ServerLevel level, long position) {
     }
 
-    private record PendingBreak(BlockState brokenState) {
+    private record PendingBreak(
+            BlockState brokenState,
+            ModdedTreeFellerService.PreparedOrigin preparedOrigin
+    ) {
     }
 }

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

@@ -175,12 +175,18 @@ public final class ModdedDimensionManager {
                 }
                 return false;
             }
+            IrisModdedChunkGenerator generator = level.getChunkSource().getGenerator()
+                    instanceof IrisModdedChunkGenerator irisGenerator
+                    ? irisGenerator
+                    : null;
+            boolean generatorUnbound = false;
             try {
                 evacuate(server, level);
-                if (level.getChunkSource().getGenerator() instanceof IrisModdedChunkGenerator generator) {
-                    generator.unbindEngine();
+                if (generator != null) {
+                    generator.unbindEngine(level);
+                    generatorUnbound = true;
                 }
-                ModdedWorldEngines.evict(level);
+                ModdedWorldEngines.evictOrThrow(level);
                 level.save(null, true, false);
                 serverAccess.removeLevel(server, key);
                 level.close();
@@ -191,12 +197,31 @@ public final class ModdedDimensionManager {
                 LOGGER.info("Iris removed runtime dimension '{}'", dimensionId);
                 return true;
             } catch (Throwable e) {
+                rollbackRemoval(server, serverAccess, key, level, generator, generatorUnbound, e);
                 LOGGER.error("Iris failed to remove runtime dimension '{}'", dimensionId, e);
                 throw new IllegalStateException("Iris runtime dimension removal failed for " + dimensionId, e);
             }
         }
     }
 
+    private static void rollbackRemoval(MinecraftServer server, ModdedServerAccess serverAccess,
+                                        ResourceKey<Level> key, ServerLevel level,
+                                        IrisModdedChunkGenerator generator, boolean generatorUnbound,
+                                        Throwable failure) {
+        try {
+            if (!generatorUnbound || generator == null || !serverAccess.hasLevel(server, key)) {
+                return;
+            }
+            generator.bindLevel(level);
+        } catch (Throwable rollbackFailure) {
+            if (rollbackFailure != failure) {
+                failure.addSuppressed(rollbackFailure);
+            }
+            LOGGER.error("Iris failed to restore the engine for retained runtime dimension '{}'",
+                    key.identifier(), rollbackFailure);
+        }
+    }
+
     public static boolean teleport(ServerPlayer player, MinecraftServer server, String dimensionId, double x, double y, double z) {
         ServerLevel level = level(server, dimensionId);
         if (level == null) {

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

@@ -42,6 +42,7 @@ import art.arcane.iris.modded.service.ModdedLogFilterService;
 import art.arcane.iris.modded.service.ModdedPreservationService;
 import art.arcane.iris.modded.service.ModdedSettingsHotloadService;
 import art.arcane.iris.modded.service.ModdedStudioHotloadService;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
 import art.arcane.iris.spi.IrisPlatform;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.spi.IrisServices;
@@ -135,29 +136,82 @@ public final class ModdedEngineBootstrap {
         }
     }
 
+    public static void levelUnloaded(ServerLevel level) {
+        if (!(level.getChunkSource().getGenerator() instanceof IrisModdedChunkGenerator generator)) {
+            return;
+        }
+
+        try {
+            generator.unbindEngine(level);
+        } catch (Throwable exception) {
+            LOGGER.error("Iris engine unload failed for {}", level.dimension().identifier(), exception);
+            if (exception instanceof RuntimeException runtimeException) {
+                throw runtimeException;
+            }
+            if (exception instanceof Error fatalError) {
+                throw fatalError;
+            }
+            throw new IllegalStateException("Iris engine unload failed for "
+                    + level.dimension().identifier(), exception);
+        }
+    }
+
     public static void stop() {
         MinecraftServer stoppingServer = currentServer;
-        ModdedWorldCheck.serverStopped(stoppingServer);
-        ModdedProtocolHandler.stop();
-        ModdedPregenJob.shutdown();
-        ModdedObjectUndo.clearAll();
-        ModdedWandService.clearAll();
-        ModdedBlockBreakHandler.clear();
-        ModdedStudioCommands.clear();
-        ModdedWorldEngines.shutdown();
-        ModdedPrimaryWorldRouter.clear();
-        services().disableAll();
-        ModdedDimensionManager.clear();
+        Throwable failure = null;
+        failure = runStopStage(failure, "world check", () -> ModdedWorldCheck.serverStopped(stoppingServer));
+        failure = runStopStage(failure, "protocol", ModdedProtocolHandler::stop);
+        failure = runStopStage(failure, "pregenerator", ModdedPregenJob::shutdown);
+        failure = runStopStage(failure, "object undo", ModdedObjectUndo::clearAll);
+        failure = runStopStage(failure, "wand service", ModdedWandService::clearAll);
+        failure = runStopStage(failure, "block break handler", ModdedBlockBreakHandler::clear);
+        failure = runStopStage(failure, "studio commands", ModdedStudioCommands::clear);
+        failure = runStopStage(failure, "services", () -> services().disableAll());
+        failure = runStopStage(failure, "world engines", ModdedWorldEngines::shutdown);
+        failure = runStopStage(failure, "primary world router", ModdedPrimaryWorldRouter::clear);
+        failure = runStopStage(failure, "dimension manager", ModdedDimensionManager::clear);
         ModdedScheduler scheduler = schedulerOrNull();
         if (scheduler != null) {
-            scheduler.shutdown();
+            failure = runStopStage(failure, "scheduler", scheduler::shutdown);
         }
-        IrisModdedChunkGenerator.shutdownGenPool();
-        ModdedSentry.flush();
-        ModdedStartup.reset();
-        currentServer = null;
-        spawnCaptureServer = null;
-        initialSpawnWasDefault = false;
+        failure = runStopStage(failure, "generation pool", IrisModdedChunkGenerator::shutdownGenPool);
+        failure = runStopStage(failure, "sentry", ModdedSentry::flush);
+        failure = runStopStage(failure, "startup state", ModdedStartup::reset);
+        failure = runStopStage(failure, "server state", () -> {
+            currentServer = null;
+            spawnCaptureServer = null;
+            initialSpawnWasDefault = false;
+        });
+        if (failure != null) {
+            LOGGER.error("Iris modded shutdown completed with failures", failure);
+            throw propagateStopFailure(failure);
+        }
+    }
+
+    private static Throwable runStopStage(Throwable failure, String stage, StopAction action) {
+        try {
+            action.run();
+            return failure;
+        } catch (Throwable stageFailure) {
+            LOGGER.error("Iris modded shutdown stage '{}' failed", stage, stageFailure);
+            if (failure == null) {
+                return stageFailure;
+            }
+            if (stageFailure != failure) {
+                failure.addSuppressed(stageFailure);
+            }
+            return failure;
+        }
+    }
+
+    private static RuntimeException propagateStopFailure(Throwable failure) {
+        if (failure instanceof RuntimeException runtimeException) {
+            return runtimeException;
+        }
+        if (failure instanceof Error fatalError) {
+            throw fatalError;
+        }
+        return new IllegalStateException("Iris modded shutdown completed with failures", failure);
     }
 
     private static void captureInitialSpawn(MinecraftServer server) {
@@ -317,6 +371,7 @@ public final class ModdedEngineBootstrap {
                         ModdedStudioHotloadService.class, new ModdedStudioHotloadService());
                 createdServices.register(ModdedChunkUpdateService.class, new ModdedChunkUpdateService());
                 createdServices.register(ModdedEntitySpawnService.class, new ModdedEntitySpawnService());
+                createdServices.register(ModdedTreeFellerService.class, new ModdedTreeFellerService());
 
                 bindService(PreservationRegistry.class, preservation, rollback);
                 bindService(EngineEffectsProvider.class,
@@ -377,6 +432,11 @@ public final class ModdedEngineBootstrap {
         void restore() throws Throwable;
     }
 
+    @FunctionalInterface
+    private interface StopAction {
+        void run() throws Throwable;
+    }
+
     private static final class BindRollback {
         private final ArrayDeque<RollbackAction> actions = new ArrayDeque<>();
 

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

@@ -18,7 +18,11 @@
 
 package art.arcane.iris.modded;
 
+import net.minecraft.core.BlockPos;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.block.state.BlockState;
 
 import java.io.File;
 import java.nio.file.Path;
@@ -39,4 +43,8 @@ public interface ModdedLoader {
     Path configDir();
 
     File modJar();
+
+    boolean hasTreeFellerPermission(ServerPlayer player);
+
+    boolean canTreeFellerBreak(ServerLevel level, ServerPlayer player, BlockPos position, BlockState state);
 }

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

@@ -26,7 +26,6 @@ import org.slf4j.LoggerFactory;
 
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.function.Consumer;
 
 public final class ModdedServiceManager {
     private static final Logger LOGGER = LoggerFactory.getLogger("Iris");
@@ -92,7 +91,24 @@ public final class ModdedServiceManager {
             return;
         }
         enabled = false;
-        forEachReversed(this::disableService);
+        Throwable failure = null;
+        ModdedService[] ordered = services.values().toArray(new ModdedService[0]);
+        for (int i = ordered.length - 1; i >= 0; i--) {
+            ModdedService service = ordered[i];
+            try {
+                service.onDisable();
+            } catch (Throwable serviceFailure) {
+                LOGGER.error("Iris service onDisable failed for {}", service.getClass().getName(), serviceFailure);
+                if (failure == null) {
+                    failure = serviceFailure;
+                } else if (serviceFailure != failure) {
+                    failure.addSuppressed(serviceFailure);
+                }
+            }
+        }
+        if (failure != null) {
+            throw new IllegalStateException("One or more Iris services failed to disable", failure);
+        }
     }
 
     synchronized void rollback(Throwable failure) {
@@ -106,14 +122,6 @@ public final class ModdedServiceManager {
         services.clear();
     }
 
-    private void disableService(ModdedService service) {
-        try {
-            service.onDisable();
-        } catch (Throwable error) {
-            LOGGER.error("Iris service onDisable failed for {}", service.getClass().getName(), error);
-        }
-    }
-
     private void tickService(ModdedTickableService service, MinecraftServer server) {
         try {
             service.onServerTick(server);
@@ -144,10 +152,4 @@ public final class ModdedServiceManager {
         return new IllegalStateException("Iris service failed to enable: " + service.getClass().getName(), failure);
     }
 
-    private void forEachReversed(Consumer<ModdedService> action) {
-        ModdedService[] ordered = services.values().toArray(new ModdedService[0]);
-        for (int i = ordered.length - 1; i >= 0; i--) {
-            action.accept(ordered[i]);
-        }
-    }
 }

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

@@ -102,7 +102,7 @@ public final class ModdedWorldEngines {
         ModdedEngineBootstrap.bind();
         PackValidationRegistry.requireLoadable(pack);
         File packDir = resolvePack(pack, dimensionKey);
-        IrisData data = IrisData.get(packDir);
+        IrisData data = IrisData.openRuntime(packDir);
         IrisDimension dimension = data.getDimensionLoader().load(dimensionKey);
         if (dimension == null) {
             LOGGER.error("Iris pack '{}' at {} does not contain dimension '{}' (expected dimensions/{}.json). Install a matching Iris pack and restart.",
@@ -184,17 +184,28 @@ public final class ModdedWorldEngines {
     }
 
     public static void shutdown() {
-        for (Map.Entry<ServerLevel, Engine> entry : ENGINES.entrySet()) {
+        Throwable failure = null;
+        for (Map.Entry<ServerLevel, Engine> entry : new ArrayList<>(ENGINES.entrySet())) {
+            ServerLevel level = entry.getKey();
             Engine engine = entry.getValue();
             try {
-                if (!engine.isClosed()) {
-                    engine.close();
+                close(engine);
+                if (!ENGINES.remove(level, engine) && ENGINES.containsKey(level)) {
+                    throw new IllegalStateException("Iris engine mapping changed during shutdown for "
+                            + level.dimension().identifier());
                 }
-                LOGGER.info("Iris engine closed for {}", entry.getKey().dimension().identifier());
+                LOGGER.info("Iris engine closed for {}", level.dimension().identifier());
             } catch (Throwable e) {
-                LOGGER.error("Iris engine close failed for {}", entry.getKey().dimension().identifier(), e);
+                LOGGER.error("Iris engine close failed for {}", level.dimension().identifier(), e);
+                if (failure == null) {
+                    failure = e;
+                } else if (e != failure) {
+                    failure.addSuppressed(e);
+                }
             }
         }
-        ENGINES.clear();
+        if (failure != null) {
+            throw new IllegalStateException("One or more Iris engines failed to close; failed mappings were retained", failure);
+        }
     }
 }

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

@@ -22,6 +22,7 @@ import art.arcane.iris.core.IrisSettings;
 import art.arcane.iris.core.gui.PregeneratorJob;
 import art.arcane.iris.engine.IrisComplex;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.EngineLifecycleTasks;
 import art.arcane.iris.engine.framework.EngineWorldManager;
 import art.arcane.iris.engine.framework.LootResolver;
 import art.arcane.iris.engine.object.IRare;
@@ -79,6 +80,9 @@ public final class ModdedWorldManager implements EngineWorldManager {
     private long lastAmbientAt;
     private long lastCountAt;
     private long lastInitialRecoveryAt;
+    private boolean initialSpawnQueueClosed;
+    private boolean mantleWarmupExecutorStopped;
+    private boolean mantleWarmupsCleared;
     private volatile boolean closed;
     private volatile int cachedEntityCount;
     private volatile int cachedConsideredChunks;
@@ -116,6 +120,10 @@ public final class ModdedWorldManager implements EngineWorldManager {
     }
 
     public void serverTick(ServerLevel level) {
+        EngineLifecycleTasks.run(engine, "modded_world_manager_tick", () -> runServerTick(level));
+    }
+
+    private void runServerTick(ServerLevel level) {
         if (closed || engine.isClosed() || engine.getMantle().getMantle().isClosed()) {
             return;
         }
@@ -239,7 +247,12 @@ public final class ModdedWorldManager implements EngineWorldManager {
             IrisLogging.error("Iris could not schedule the initial entity-spawn follow-up because the modded scheduler is unavailable.");
             return;
         }
-        scheduler.laterGlobal(() -> runInitialFollowUp(level, chunkX, chunkZ), RNG.r.i(5, 200));
+        scheduler.laterGlobal(
+                () -> EngineLifecycleTasks.run(
+                        engine,
+                        "modded_world_manager_initial_spawn_followup",
+                        () -> runInitialFollowUp(level, chunkX, chunkZ)),
+                RNG.r.i(5, 200));
     }
 
     private void runInitialFollowUp(ServerLevel level, int chunkX, int chunkZ) {
@@ -272,7 +285,14 @@ public final class ModdedWorldManager implements EngineWorldManager {
             return;
         }
         try {
-            mantleWarmupExecutor.execute(() -> warmupMantleChunk(key, chunkX, chunkZ));
+            mantleWarmupExecutor.execute(() -> {
+                if (!EngineLifecycleTasks.run(
+                        engine,
+                        "modded_world_manager_mantle_warmup",
+                        () -> warmupMantleChunk(key, chunkX, chunkZ))) {
+                    mantleWarmups.remove(key);
+                }
+            });
         } catch (RejectedExecutionException e) {
             mantleWarmups.remove(key);
         }
@@ -727,11 +747,36 @@ public final class ModdedWorldManager implements EngineWorldManager {
     }
 
     @Override
-    public void close() {
+    public synchronized void close() {
         closed = true;
-        initialSpawnQueue.close();
-        mantleWarmupExecutor.shutdownNow();
-        mantleWarmups.clear();
+        Throwable failure = null;
+        if (!initialSpawnQueueClosed) {
+            try {
+                initialSpawnQueue.close();
+                initialSpawnQueueClosed = true;
+            } catch (Throwable e) {
+                failure = e;
+            }
+        }
+        if (!mantleWarmupExecutorStopped) {
+            try {
+                mantleWarmupExecutor.shutdownNow();
+                mantleWarmupExecutorStopped = true;
+            } catch (Throwable e) {
+                failure = appendCloseFailure(failure, e);
+            }
+        }
+        if (!mantleWarmupsCleared) {
+            try {
+                mantleWarmups.clear();
+                mantleWarmupsCleared = true;
+            } catch (Throwable e) {
+                failure = appendCloseFailure(failure, e);
+            }
+        }
+        if (failure != null) {
+            throw new IllegalStateException("Failed to completely stop the modded Iris world manager.", failure);
+        }
     }
 
     @Override
@@ -757,4 +802,14 @@ public final class ModdedWorldManager implements EngineWorldManager {
     public void onSave() {
         engine.getMantle().save();
     }
+
+    private static Throwable appendCloseFailure(Throwable failure, Throwable next) {
+        if (failure == null) {
+            return next;
+        }
+        if (failure != next) {
+            failure.addSuppressed(next);
+        }
+        return failure;
+    }
 }

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

@@ -23,6 +23,8 @@ import art.arcane.iris.core.gui.GuiHost;
 import art.arcane.iris.core.loader.IrisRegistrant;
 import art.arcane.iris.core.pack.PackDownloader;
 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.Locator;
 import art.arcane.iris.engine.framework.NativeStructureGenerationPolicy;
@@ -40,6 +42,7 @@ import art.arcane.iris.modded.ModdedLoader;
 import art.arcane.iris.modded.ModdedPackInstaller;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.volmlib.util.math.Position2;
 import art.arcane.volmlib.util.matter.MatterMarker;
@@ -95,7 +98,11 @@ import java.util.Optional;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.TreeSet;
+import java.util.UUID;
+import java.util.concurrent.CancellationException;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.function.Predicate;
 
@@ -104,6 +111,7 @@ public final class IrisModdedCommands {
     private static final Predicate<CommandSourceStack> GATE = Commands.hasPermission(Commands.LEVEL_GAMEMASTERS);
     private static final long LOCATE_TIMEOUT_MS = 120000L;
     private static final int NATIVE_STRUCTURE_LOCATE_RADIUS = 100;
+    private static final ConcurrentHashMap<UUID, CompletableFuture<Position2>> ACTIVE_LOCATE_REQUESTS = new ConcurrentHashMap<>();
 
     private static final SuggestionProvider<CommandSourceStack> BIOME_KEYS = (CommandContext<CommandSourceStack> context, SuggestionsBuilder builder) -> suggestBiomeKeys(context, builder);
     private static final SuggestionProvider<CommandSourceStack> REGION_KEYS = (CommandContext<CommandSourceStack> context, SuggestionsBuilder builder) -> suggestRegionKeys(context, builder);
@@ -1172,32 +1180,79 @@ public final class IrisModdedCommands {
         int chunkX = player.blockPosition().getX() >> 4;
         int chunkZ = player.blockPosition().getZ() >> 4;
         ok(source, "Searching for " + label + "...");
-        Thread thread = new Thread(() -> {
-            try {
-                Position2 at = locator.find(engine, new Position2(chunkX, chunkZ), LOCATE_TIMEOUT_MS, (Integer checks) -> {
-                }).get();
-                if (at == null) {
-                    server.execute(() -> fail(source, "Could not find " + label + " within the search timeout."));
-                    return;
+        CompletableFuture<Position2> search;
+        try {
+            search = locator.find(engine, new Position2(chunkX, chunkZ), LOCATE_TIMEOUT_MS, (Integer checks) -> {
+            });
+        } catch (WrongEngineBroException e) {
+            fail(source, "The engine for this world has been closed; rejoin the dimension and try again.");
+            return;
+        }
+        UUID playerId = player.getUUID();
+        CompletableFuture<Position2> previous = ACTIVE_LOCATE_REQUESTS.put(playerId, search);
+        if (previous != null && previous != search) {
+            previous.cancel(true);
+        }
+        search.whenComplete((Position2 at, Throwable error) -> completeLocate(
+                source, level, engine, player, label, server, playerId, search, at, error));
+    }
+
+    private static void completeLocate(CommandSourceStack source, ServerLevel level, Engine engine,
+                                       ServerPlayer player, String label, MinecraftServer server, UUID playerId,
+                                       CompletableFuture<Position2> search, Position2 at, Throwable error) {
+        if (ACTIVE_LOCATE_REQUESTS.get(playerId) != search) {
+            return;
+        }
+        Throwable failure = unwrapCompletionFailure(error);
+        if (failure instanceof CancellationException) {
+            ACTIVE_LOCATE_REQUESTS.remove(playerId, search);
+            return;
+        }
+        if (failure != null) {
+            LOGGER.error("Iris locate failed for {}", label, failure);
+            server.execute(() -> {
+                if (ACTIVE_LOCATE_REQUESTS.remove(playerId, search)) {
+                    fail(source, "Search failed: " + failure);
                 }
-                int blockX = (at.getX() << 4) + 8;
-                int blockZ = (at.getZ() << 4) + 8;
-                int blockY = engine.getMinHeight() + engine.getHeight(blockX, blockZ, false) + 2;
-                server.execute(() -> {
-                    player.teleportTo(level, blockX + 0.5D, blockY, blockZ + 0.5D, Set.<Relative>of(), player.getYRot(), player.getXRot(), false);
-                    ok(source, "Teleported to " + label + " at " + blockX + " " + blockY + " " + blockZ);
-                });
-            } catch (WrongEngineBroException e) {
-                server.execute(() -> fail(source, "The engine for this world has been closed; rejoin the dimension and try again."));
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-            } catch (ExecutionException e) {
-                LOGGER.error("Iris locate failed for {}", label, e);
-                server.execute(() -> fail(source, "Search failed: " + e.getCause()));
+            });
+            return;
+        }
+        if (at == null) {
+            server.execute(() -> {
+                if (ACTIVE_LOCATE_REQUESTS.remove(playerId, search)) {
+                    fail(source, "Could not find " + label + " within the search timeout.");
+                }
+            });
+            return;
+        }
+        server.execute(() -> {
+            if (ACTIVE_LOCATE_REQUESTS.remove(playerId, search)) {
+                teleportToLocateResult(source, level, engine, player, label, at);
             }
-        }, "Iris Locator");
-        thread.setDaemon(true);
-        thread.start();
+        });
+    }
+
+    private static void teleportToLocateResult(CommandSourceStack source, ServerLevel level, Engine engine,
+                                                ServerPlayer player, String label, Position2 at) {
+        int blockX = (at.getX() << 4) + 8;
+        int blockZ = (at.getZ() << 4) + 8;
+        try (GenerationSessionLease lease = engine.acquireGenerationLease("modded_locator_teleport");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            int blockY = engine.getMinHeight() + engine.getHeight(blockX, blockZ, false) + 2;
+            player.teleportTo(level, blockX + 0.5D, blockY, blockZ + 0.5D, Set.<Relative>of(), player.getYRot(), player.getXRot(), false);
+            ok(source, "Teleported to " + label + " at " + blockX + " " + blockY + " " + blockZ);
+        } catch (GenerationSessionException e) {
+            fail(source, "The engine changed while locating " + label + "; try again.");
+        }
+    }
+
+    private static Throwable unwrapCompletionFailure(Throwable error) {
+        Throwable failure = error;
+        while ((failure instanceof CompletionException || failure instanceof ExecutionException)
+                && failure.getCause() != null) {
+            failure = failure.getCause();
+        }
+        return failure;
     }
 
     private static int seed(CommandSourceStack source) {

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

@@ -35,8 +35,13 @@ import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.storage.LevelResource;
 
 import java.io.File;
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.BooleanSupplier;
 
 public final class ModdedPregenJob {
+    private static final long SHUTDOWN_TIMEOUT_MILLIS = 10_000L;
+    private static final AtomicReference<ActivePregen> ACTIVE = new AtomicReference<>();
     private static volatile String dimension = "?";
 
     private ModdedPregenJob() {
@@ -54,13 +59,26 @@ public final class ModdedPregenJob {
                 .radiusX(radiusBlocks)
                 .radiusZ(radiusBlocks)
                 .build();
-        PregeneratorMethod method = new ModdedPregenMethod(level, engine, sync);
+        ModdedPregenMethod moddedMethod = new ModdedPregenMethod(level, engine, sync);
+        PregeneratorMethod method = moddedMethod;
         if (cached) {
             method = new CachedPregenMethod(method, PregenCache.create(cacheDirectory(level)).sync(), task);
         }
+        ActivePregen active = new ActivePregen(engine, moddedMethod);
+        ACTIVE.set(active);
         dimension = level.dimension().identifier().toString();
-        new PregeneratorJob(task, method, engine);
-        return true;
+        try {
+            PregeneratorJob job = new PregeneratorJob(task, method, engine);
+            job.whenDone(() -> {
+                if (!moddedMethod.hasPendingFinalSave()) {
+                    ACTIVE.compareAndSet(active, null);
+                }
+            });
+            return true;
+        } catch (Throwable failure) {
+            ACTIVE.compareAndSet(active, null);
+            throw propagate(failure);
+        }
     }
 
     private static File cacheDirectory(ServerLevel level) {
@@ -73,7 +91,17 @@ public final class ModdedPregenJob {
     }
 
     public static void shutdown() {
-        PregeneratorJob.shutdownAndWait(10_000L);
+        ActivePregen active = ACTIVE.get();
+        shutdownAndSave(active, () -> PregeneratorJob.shutdownAndWait(SHUTDOWN_TIMEOUT_MILLIS));
+    }
+
+    public static boolean shutdownForWorld(String worldIdentity) {
+        PregeneratorJob job = PregeneratorJob.getInstance();
+        if (job == null || !job.targetsWorldIdentity(worldIdentity)) {
+            return false;
+        }
+        ActivePregen active = matchingActive(worldIdentity);
+        return shutdownAndSave(active, () -> PregeneratorJob.shutdownInstanceForWorld(worldIdentity));
     }
 
     public static Boolean pauseResume() {
@@ -125,4 +153,64 @@ public final class ModdedPregenJob {
         status.append(ModdedCommandFeedback.footer());
         return status;
     }
+
+    private static ActivePregen matchingActive(String worldIdentity) {
+        ActivePregen active = ACTIVE.get();
+        return active != null && active.targets(worldIdentity) ? active : null;
+    }
+
+    private static boolean shutdownAndSave(ActivePregen active, BooleanSupplier shutdown) {
+        boolean deferred = active != null && active.method().deferFinalSaveToServerThread();
+        boolean stopped = false;
+        boolean result = false;
+        Throwable failure = null;
+        try {
+            result = shutdown.getAsBoolean();
+            stopped = result;
+        } catch (Throwable shutdownFailure) {
+            failure = shutdownFailure;
+        }
+
+        if (deferred) {
+            try {
+                if (stopped) {
+                    active.method().completeDeferredFinalSave();
+                } else {
+                    active.method().cancelDeferredFinalSave();
+                }
+            } catch (Throwable saveFailure) {
+                if (failure == null) {
+                    failure = saveFailure;
+                } else if (saveFailure != failure) {
+                    failure.addSuppressed(saveFailure);
+                }
+            }
+        }
+
+        if (failure == null && (stopped || PregeneratorJob.getInstance() == null)) {
+            ACTIVE.compareAndSet(active, null);
+        }
+        if (failure != null) {
+            throw propagate(failure);
+        }
+        return result;
+    }
+
+    private static RuntimeException propagate(Throwable failure) {
+        if (failure instanceof RuntimeException runtimeException) {
+            return runtimeException;
+        }
+        if (failure instanceof Error fatalError) {
+            throw fatalError;
+        }
+        return new IllegalStateException("Iris modded pregenerator shutdown failed", failure);
+    }
+
+    private record ActivePregen(Engine engine, ModdedPregenMethod method) {
+        private boolean targets(String worldIdentity) {
+            return engine != null
+                    && engine.getWorld() != null
+                    && Objects.equals(engine.getWorld().identity(), worldIdentity);
+        }
+    }
 }

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

@@ -40,14 +40,18 @@ import java.util.concurrent.Semaphore;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
 
 public final class ModdedPregenMethod implements PregeneratorMethod {
     private static final Logger LOGGER = LoggerFactory.getLogger("Iris");
     private static final TicketType PREGEN_TICKET = new TicketType(TicketType.NO_TIMEOUT, TicketType.FLAG_LOADING | TicketType.FLAG_KEEP_DIMENSION_ACTIVE);
     private static final int ADAPTIVE_TIMEOUT_STEP = 3;
     private static final long ADAPTIVE_RECOVERY_INTERVAL = 64L;
+    private static final long FINAL_SAVE_TIMEOUT_MILLIS = 10_000L;
+    private static final long FINAL_SAVE_POLL_MILLIS = 50L;
     private static final boolean PARALLEL_CHUNK_SYSTEM = detectParallelChunkSystem();
 
     private final ServerLevel level;
@@ -62,6 +66,10 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
     private final AtomicInteger adaptiveLimit;
     private final AtomicInteger timeoutStreak = new AtomicInteger();
     private final AtomicLong completed = new AtomicLong();
+    private final AtomicBoolean finalSaveOnServerThread = new AtomicBoolean(false);
+    private final AtomicBoolean finalSaveDeferred = new AtomicBoolean(false);
+    private final AtomicBoolean finalSaveCompleted = new AtomicBoolean(false);
+    private final AtomicReference<FinalSaveRequest> queuedFinalSave = new AtomicReference<>();
     private final int timeoutSeconds;
     private final PregenMantleBackpressure backpressure;
 
@@ -114,6 +122,9 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
         }
         LOGGER.info("Iris modded pregen done: dim={} completed={} peakInFlight={} finalLimit={}",
                 level.dimension().identifier(), completed.get(), inFlightPeak.get(), adaptiveLimit.get());
+        if (deferFinalSaveIfRequested()) {
+            return;
+        }
         saveLevel(true);
     }
 
@@ -122,24 +133,156 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
         saveLevel(false);
     }
 
-    private void saveLevel(boolean wait) {
-        CompletableFuture<Void> saved = new CompletableFuture<>();
-        level.getServer().execute(() -> {
-            try {
-                level.save(null, false, false);
-            } finally {
-                saved.complete(null);
+    boolean deferFinalSaveToServerThread() {
+        if (!level.getServer().isSameThread()) {
+            return false;
+        }
+        finalSaveOnServerThread.set(true);
+        return true;
+    }
+
+    void completeDeferredFinalSave() {
+        requireServerThreadForFinalSave();
+        cancelQueuedFinalSave();
+        if (!finalSaveCompleted.get()) {
+            saveLevelOnServerThread();
+            finalSaveCompleted.set(true);
+        }
+        finalSaveDeferred.set(false);
+        finalSaveOnServerThread.set(false);
+    }
+
+    void cancelDeferredFinalSave() {
+        requireServerThreadForFinalSave();
+        finalSaveOnServerThread.set(false);
+        if (finalSaveDeferred.get() || queuedFinalSave.get() != null) {
+            cancelQueuedFinalSave();
+            if (!finalSaveCompleted.get()) {
+                saveLevelOnServerThread();
+                finalSaveCompleted.set(true);
             }
-        });
-        if (!wait) {
+            finalSaveDeferred.set(false);
+        }
+    }
+
+    boolean hasPendingFinalSave() {
+        return finalSaveOnServerThread.get()
+                || finalSaveDeferred.get()
+                || queuedFinalSave.get() != null;
+    }
+
+    private void saveLevel(boolean wait) {
+        if (wait) {
+            saveFinalLevel();
+            return;
+        }
+        MinecraftServer server = level.getServer();
+        if (server.isSameThread()) {
+            saveLevelOnServerThread();
+            return;
+        }
+        server.execute(this::saveLevelOnServerThread);
+    }
+
+    private void saveFinalLevel() {
+        MinecraftServer server = level.getServer();
+        if (server.isSameThread()) {
+            saveLevelOnServerThread();
+            finalSaveCompleted.set(true);
+            return;
+        }
+        if (deferFinalSaveIfRequested()) {
+            return;
+        }
+
+        FinalSaveRequest request = new FinalSaveRequest();
+        if (!queuedFinalSave.compareAndSet(null, request)) {
+            throw new IllegalStateException("Iris pregen final save is already queued for "
+                    + level.dimension().identifier());
+        }
+        try {
+            server.execute(() -> executeFinalSave(request));
+        } catch (RuntimeException | Error failure) {
+            queuedFinalSave.compareAndSet(request, null);
+            request.fail(failure);
+            throw failure;
+        }
+        awaitFinalSave(request);
+    }
+
+    private void executeFinalSave(FinalSaveRequest request) {
+        if (!request.claim()) {
             return;
         }
         try {
-            saved.get(10, TimeUnit.SECONDS);
-        } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
-        } catch (TimeoutException | ExecutionException e) {
-            LOGGER.warn("Iris pregen level save did not complete in time for {}", level.dimension().identifier());
+            saveLevelOnServerThread();
+            finalSaveCompleted.set(true);
+            request.complete();
+        } catch (RuntimeException | Error failure) {
+            request.fail(failure);
+            throw failure;
+        } finally {
+            queuedFinalSave.compareAndSet(request, null);
+        }
+    }
+
+    private void awaitFinalSave(FinalSaveRequest request) {
+        long deadline = System.nanoTime() + TimeUnit.MILLISECONDS.toNanos(FINAL_SAVE_TIMEOUT_MILLIS);
+        while (true) {
+            if (deferFinalSaveIfRequested()) {
+                return;
+            }
+            long remainingNanos = deadline - System.nanoTime();
+            if (remainingNanos <= 0L) {
+                LOGGER.warn("Iris pregen level save did not complete in time for {}", level.dimension().identifier());
+                return;
+            }
+            long waitMillis = Math.max(1L, Math.min(FINAL_SAVE_POLL_MILLIS,
+                    TimeUnit.NANOSECONDS.toMillis(remainingNanos)));
+            try {
+                request.completion().get(waitMillis, TimeUnit.MILLISECONDS);
+                return;
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                return;
+            } catch (TimeoutException e) {
+                continue;
+            } catch (ExecutionException e) {
+                Throwable cause = e.getCause() == null ? e : e.getCause();
+                LOGGER.error("Iris pregen level save failed for {}", level.dimension().identifier(), cause);
+                throw new IllegalStateException("Iris pregen level save failed for "
+                        + level.dimension().identifier(), cause);
+            }
+        }
+    }
+
+    private boolean deferFinalSaveIfRequested() {
+        if (!finalSaveOnServerThread.get()) {
+            return false;
+        }
+        finalSaveDeferred.set(true);
+        if (finalSaveOnServerThread.get()) {
+            return true;
+        }
+        finalSaveDeferred.set(false);
+        return false;
+    }
+
+    private void cancelQueuedFinalSave() {
+        FinalSaveRequest request = queuedFinalSave.getAndSet(null);
+        if (request != null) {
+            request.cancel();
+        }
+    }
+
+    private void saveLevelOnServerThread() {
+        level.save(null, false, false);
+    }
+
+    private void requireServerThreadForFinalSave() {
+        if (!level.getServer().isSameThread()) {
+            throw new IllegalStateException("Iris pregen final save must run on the Minecraft server thread for "
+                    + level.dimension().identifier());
         }
     }
 
@@ -361,4 +504,31 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
     public Mantle getMantle() {
         return engine.getMantle().getMantle();
     }
+
+    private static final class FinalSaveRequest {
+        private final CompletableFuture<Void> completion = new CompletableFuture<>();
+        private final AtomicBoolean active = new AtomicBoolean(true);
+
+        private boolean claim() {
+            return active.compareAndSet(true, false);
+        }
+
+        private void complete() {
+            completion.complete(null);
+        }
+
+        private void fail(Throwable failure) {
+            active.set(false);
+            completion.completeExceptionally(failure);
+        }
+
+        private void cancel() {
+            active.set(false);
+            completion.complete(null);
+        }
+
+        private CompletableFuture<Void> completion() {
+            return completion;
+        }
+    }
 }

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

@@ -19,13 +19,13 @@
 package art.arcane.iris.modded.service;
 
 import art.arcane.iris.core.IrisSettings;
-import art.arcane.iris.core.gui.PregeneratorJob;
-import art.arcane.iris.core.pregenerator.MantleHeapPressure;
-import art.arcane.iris.core.runtime.GoldenHashEngine;
-import art.arcane.iris.core.tools.WorldMaintenance;
+import art.arcane.iris.core.service.EngineMaintenance;
 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.modded.ModdedWorldEngines;
 import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.util.project.context.IrisContext;
 import net.minecraft.server.MinecraftServer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -33,71 +33,74 @@ import org.slf4j.LoggerFactory;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.IdentityHashMap;
-import java.util.Locale;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicInteger;
 
 public final class ModdedEngineMaintenanceService implements ModdedTickableService {
     private static final Logger LOGGER = LoggerFactory.getLogger("Iris");
-    private static final long TRIM_PERIOD_MILLIS = 2_000L;
+    private static final long MAINTENANCE_PERIOD_MILLIS = 2_000L;
     private static final long SAVE_PERIOD_MILLIS = 60_000L;
+    private static final long SHUTDOWN_TIMEOUT_SECONDS = 30L;
+    private static final long INTERRUPT_DRAIN_TIMEOUT_SECONDS = 5L;
 
-    private final AtomicInteger tectonicLimit = new AtomicInteger(30);
     private final Set<Engine> inFlight = Collections.synchronizedSet(Collections.newSetFromMap(new IdentityHashMap<>()));
+    private final Map<Engine, Long> lastSavedAt = Collections.synchronizedMap(new IdentityHashMap<>());
     private volatile ExecutorService service;
     private long lastMaintenanceAt;
-    private long lastSaveAt;
 
     @Override
     public void onEnable() {
-        if (service != null) {
+        ExecutorService current = service;
+        if (current != null && !current.isShutdown()) {
             return;
         }
-        IrisSettings.IrisSettingsPerformance settings = IrisSettings.get().getPerformance();
-        IrisSettings.IrisSettingsEngineSVC engineSettings = settings.getEngineSVC();
-        ThreadFactory factory = (engineSettings.isUseVirtualThreads()
+
+        IrisSettings.IrisSettingsEngineSVC settings = IrisSettings.get().getPerformance().getEngineSVC();
+        ThreadFactory factory = (settings.isUseVirtualThreads()
                 ? Thread.ofVirtual()
-                : Thread.ofPlatform().priority(engineSettings.getPriority()))
+                : Thread.ofPlatform().priority(settings.getPriority()))
                 .name("Iris EngineSVC-", 0)
                 .factory();
-        service = Executors.newThreadPerTaskExecutor(factory);
-        tectonicLimit.set(settings.getTectonicPlateSize());
+        service = Executors.newFixedThreadPool(EngineMaintenance.workerParallelism(), factory);
         lastMaintenanceAt = 0L;
-        lastSaveAt = System.currentTimeMillis();
+        inFlight.clear();
+        lastSavedAt.clear();
     }
 
     @Override
     public void onDisable() {
         ExecutorService active = service;
         service = null;
-        if (active != null) {
-            active.shutdown();
+        boolean drained = shutdownAndDrain(active);
+        if (drained) {
+            inFlight.clear();
+        }
+        lastSavedAt.clear();
+        if (!drained) {
+            throw new IllegalStateException("Iris engine maintenance workers remained active during service shutdown");
         }
-        inFlight.clear();
     }
 
     @Override
     public void onServerTick(MinecraftServer server) {
         ExecutorService active = service;
-        if (active == null) {
+        if (active == null || active.isShutdown()) {
             return;
         }
+
         long now = System.currentTimeMillis();
-        if (now - lastMaintenanceAt < TRIM_PERIOD_MILLIS) {
+        if (now - lastMaintenanceAt < MAINTENANCE_PERIOD_MILLIS) {
             return;
         }
         lastMaintenanceAt = now;
-        boolean flush = now - lastSaveAt >= SAVE_PERIOD_MILLIS;
-        if (flush) {
-            lastSaveAt = now;
-        }
+
         Collection<Engine> engines = ModdedWorldEngines.activeEngines();
-        int share = tectonicLimit.get() / Math.max(engines.size(), 1);
+        reconcileSaveState(engines, now);
         for (Engine engine : engines) {
             if (!inFlight.add(engine)) {
                 continue;
@@ -105,101 +108,118 @@ public final class ModdedEngineMaintenanceService implements ModdedTickableServi
             try {
                 active.execute(() -> {
                     try {
-                        maintain(engine, share, flush);
+                        maintain(engine, now);
                     } finally {
                         inFlight.remove(engine);
                     }
                 });
-            } catch (RejectedExecutionException rejected) {
+            } catch (RejectedExecutionException exception) {
                 inFlight.remove(engine);
+                if (active == service && !active.isShutdown()) {
+                    LOGGER.error("Iris rejected engine maintenance for {}", engineName(engine), exception);
+                }
             }
         }
     }
 
-    private void maintain(Engine engine, int share, boolean flush) {
-        if (engine == null || engine.isClosed() || engine.getMantle().getMantle().isClosed()) {
+    private void maintain(Engine engine, long scheduledAt) {
+        if (engine == null || engine.isClosing() || engine.isClosed()) {
             return;
         }
-        if (pregenTargets(engine)) {
-            return;
-        }
-        if (flush) {
-            try {
-                engine.save();
-            } catch (Throwable e) {
-                if (isMantleClosed(e)) {
-                    return;
-                }
-                IrisLogging.reportError(e);
-                LOGGER.error("Iris engine save failed for {}", engine.getWorld().name(), e);
-            }
-        }
-        if (!shouldReduce(engine) || shouldSkipForMaintenance(engine) || GoldenHashEngine.isActive()) {
-            return;
-        }
-        try {
-            if (pregenTargets(engine) && MantleHeapPressure.overHighWater()) {
-                engine.getMantle().trim(0L, 0);
-            } else {
-                engine.getMantle().trim(TimeUnit.SECONDS.toMillis(IrisSettings.get().getPerformance().getMantleKeepAlive()), activeTectonicLimit(engine, share));
-            }
-            long unloadStart = System.currentTimeMillis();
-            boolean heapPressure = pregenTargets(engine) && MantleHeapPressure.overHighWater();
-            int unloadLimit = (heapPressure || IrisSettings.get().getPerformance().getEngineSVC().forceMulticoreWrite) ? 0 : activeTectonicLimit(engine, share);
-            int count = engine.getMantle().unloadTectonicPlate(unloadLimit);
-            if (heapPressure && MantleHeapPressure.overPanicWater()) {
-                MantleHeapPressure.requestPanicReclaim();
-            }
-            if (count > 0) {
-                LOGGER.debug("Iris unloaded {} tectonic plates in {}ms for {}", count, System.currentTimeMillis() - unloadStart, engine.getWorld().name());
-            }
-        } catch (Throwable e) {
-            if (isMantleClosed(e)) {
+        try (GenerationSessionLease lease = engine.acquireGenerationLease("modded_engine_maintenance");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (!EngineMaintenance.isAvailable(engine)) {
                 return;
             }
-            IrisLogging.reportError(e);
-            LOGGER.error("Iris engine maintenance failed for {}", engine.getWorld().name(), e);
+
+            boolean pregeneratorTargetsWorld = EngineMaintenance.pregeneratorTargets(engine);
+            if (pregeneratorTargetsWorld) {
+                return;
+            }
+
+            saveIfDue(engine, scheduledAt);
+            if (!EngineMaintenance.shouldRun(engine)) {
+                return;
+            }
+
+            EngineMaintenance.Outcome outcome = EngineMaintenance.run(engine);
+            if (outcome.unloadedTectonicPlates() > 0) {
+                LOGGER.debug("Iris unloaded {} tectonic plates in {}ms for {}",
+                        outcome.unloadedTectonicPlates(), outcome.unloadDurationMillis(), engineName(engine));
+            }
+        } catch (GenerationSessionException exception) {
+            if (engine.isClosing() || exception.isExpectedTeardown()) {
+                return;
+            }
+            IrisLogging.reportError(exception);
+            LOGGER.error("Iris engine maintenance session failed for {}", engineName(engine), exception);
+        } catch (Throwable exception) {
+            if (EngineMaintenance.isMantleClosed(exception)) {
+                return;
+            }
+            IrisLogging.reportError(exception);
+            LOGGER.error("Iris engine maintenance failed for {}", engineName(engine), exception);
         }
     }
 
-    private boolean shouldReduce(Engine engine) {
-        if (!engine.isStudio() || IrisSettings.get().getPerformance().isTrimMantleInStudio()) {
+    private void saveIfDue(Engine engine, long scheduledAt) {
+        Long lastSave = lastSavedAt.get(engine);
+        if (lastSave == null || scheduledAt - lastSave < SAVE_PERIOD_MILLIS) {
+            return;
+        }
+
+        try {
+            engine.save();
+            lastSavedAt.put(engine, System.currentTimeMillis());
+        } catch (Throwable exception) {
+            if (EngineMaintenance.isMantleClosed(exception)) {
+                return;
+            }
+            IrisLogging.reportError(exception);
+            LOGGER.error("Iris engine save failed for {}", engineName(engine), exception);
+        }
+    }
+
+    private void reconcileSaveState(Collection<Engine> engines, long now) {
+        Set<Engine> activeEngines = Collections.newSetFromMap(new IdentityHashMap<>());
+        activeEngines.addAll(engines);
+        synchronized (lastSavedAt) {
+            lastSavedAt.keySet().removeIf(engine -> !activeEngines.contains(engine));
+            for (Engine engine : activeEngines) {
+                lastSavedAt.putIfAbsent(engine, now);
+            }
+        }
+    }
+
+    private boolean shutdownAndDrain(ExecutorService active) {
+        if (active == null) {
             return true;
         }
-        return pregenTargets(engine);
-    }
 
-    private boolean shouldSkipForMaintenance(Engine engine) {
-        if (engine.getWorld() == null || !WorldMaintenance.isWorldMaintenanceActive(engine.getWorld().identity())) {
-            return false;
-        }
-        return !pregenTargets(engine);
-    }
-
-    private boolean pregenTargets(Engine engine) {
-        if (engine.getWorld() == null) {
-            return false;
-        }
-        PregeneratorJob job = PregeneratorJob.getInstance();
-        return job != null && job.targetsWorldIdentity(engine.getWorld().identity());
-    }
-
-    private int activeTectonicLimit(Engine engine, int share) {
-        if (!pregenTargets(engine)) {
-            return share;
-        }
-        return Math.max(share, IrisSettings.get().getPregen().getEffectiveResidentTectonicPlates(engine.getHeight()));
-    }
-
-    private static boolean isMantleClosed(Throwable throwable) {
-        Throwable current = throwable;
-        while (current != null) {
-            String message = current.getMessage();
-            if (message != null && message.toLowerCase(Locale.ROOT).contains("mantle is closed")) {
+        active.shutdown();
+        try {
+            if (active.awaitTermination(SHUTDOWN_TIMEOUT_SECONDS, TimeUnit.SECONDS)) {
                 return true;
             }
-            current = current.getCause();
+            active.shutdownNow();
+            if (active.awaitTermination(INTERRUPT_DRAIN_TIMEOUT_SECONDS, TimeUnit.SECONDS)) {
+                return true;
+            }
+            IllegalStateException failure = new IllegalStateException(
+                    "Iris engine maintenance workers did not stop after shutdownNow");
+            IrisLogging.reportError(failure);
+            LOGGER.error("Iris engine maintenance did not terminate; active engine lifecycle leases will block unsafe shutdown", failure);
+            return false;
+        } catch (InterruptedException exception) {
+            active.shutdownNow();
+            Thread.currentThread().interrupt();
+            IrisLogging.reportError(exception);
+            LOGGER.error("Interrupted while draining Iris engine maintenance", exception);
+            return false;
         }
-        return false;
+    }
+
+    private static String engineName(Engine engine) {
+        return engine == null || engine.getWorld() == null ? "<unbound>" : engine.getWorld().name();
     }
 }

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

@@ -18,6 +18,7 @@
 
 package art.arcane.iris.modded.service;
 
+import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.engine.framework.MeteredCache;
 import art.arcane.iris.engine.framework.PreservationRegistry;
 import org.slf4j.Logger;
@@ -55,6 +56,7 @@ public final class ModdedPreservationService implements ModdedService, Preservat
 
     @Override
     public void dereference() {
+        IrisData.dereference();
         threads.removeIf((Thread thread) -> !thread.isAlive());
         services.removeIf(ExecutorService::isShutdown);
         caches.removeIf((WeakReference<MeteredCache> ref) -> {

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

@@ -30,6 +30,7 @@ import art.arcane.iris.modded.IrisModdedChunkGenerator;
 import art.arcane.iris.modded.ModdedDimensionManager;
 import art.arcane.iris.modded.ModdedForcedDatapack;
 import art.arcane.iris.modded.ModdedWorkspaceGenerator;
+import art.arcane.iris.modded.command.ModdedPregenJob;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.io.ReactiveFolder;
 import art.arcane.volmlib.util.scheduling.ChronoLatch;
@@ -180,7 +181,10 @@ public final class ModdedStudioHotloadService implements ModdedTickableService,
 
     @Override
     public void shutdownPregenerator(Engine engine) {
-        PregeneratorJob.shutdownInstance();
+        IrisWorld world = engine.getWorld();
+        if (world != null) {
+            ModdedPregenJob.shutdownForWorld(world.identity());
+        }
     }
 
     @Override

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

@@ -0,0 +1,227 @@
+package art.arcane.iris.modded.service;
+
+import art.arcane.iris.modded.ModdedEngineBootstrap;
+import art.arcane.iris.modded.ModdedScheduler;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.particles.BlockParticleOption;
+import net.minecraft.core.particles.ParticleTypes;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvents;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.state.BlockState;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+final class ModdedTreeFellerPresentation {
+    private static final Logger LOGGER = LoggerFactory.getLogger("Iris");
+    private static final int MIN_BLOCKS_PER_PULSE = 4;
+    private static final int MAX_BLOCKS_PER_PULSE = 64;
+    private static final int TARGET_EROSION_PULSES = 60;
+    private static final int MAX_EFFECT_ORIGINS_PER_PULSE = 16;
+
+    private final ServerPlayer player;
+    private final ServerLevel sourceLevel;
+    private final List<ItemStack> pendingDrops = new ArrayList<>();
+    private final AtomicBoolean effectFailureReported = new AtomicBoolean();
+    private final AtomicBoolean deliveryFailureReported = new AtomicBoolean();
+    private boolean flushScheduled;
+    private double fallbackX;
+    private double fallbackY;
+    private double fallbackZ;
+
+    ModdedTreeFellerPresentation(ServerPlayer player, ServerLevel sourceLevel) {
+        this.player = player;
+        this.sourceLevel = sourceLevel;
+        this.fallbackX = player.getX();
+        this.fallbackY = player.getY() + 0.15D;
+        this.fallbackZ = player.getZ();
+    }
+
+    static int blocksPerPulse(int blockCount) {
+        int requested = Math.max(1, (blockCount + TARGET_EROSION_PULSES - 1) / TARGET_EROSION_PULSES);
+        return Math.max(MIN_BLOCKS_PER_PULSE, Math.min(requested, MAX_BLOCKS_PER_PULSE));
+    }
+
+    static int effectStride(int blocksPerPulse) {
+        return Math.max(
+                1,
+                (blocksPerPulse + MAX_EFFECT_ORIGINS_PER_PULSE - 1) / MAX_EFFECT_ORIGINS_PER_PULSE
+        );
+    }
+
+    static List<ItemStack> consolidateDrops(Collection<ItemStack> drops) {
+        List<ItemStack> consolidated = new ArrayList<>();
+        for (ItemStack drop : drops) {
+            mergeDrop(consolidated, drop);
+        }
+        return List.copyOf(consolidated);
+    }
+
+    void activate(BlockPos position, BlockState state) {
+        try {
+            double x = position.getX() + 0.5D;
+            double y = position.getY() + 0.5D;
+            double z = position.getZ() + 0.5D;
+            sourceLevel.sendParticles(ParticleTypes.ENCHANT, x, y, z, 24, 0.45D, 0.45D, 0.45D, 0.18D);
+            sourceLevel.sendParticles(ParticleTypes.END_ROD, x, y, z, 8, 0.25D, 0.25D, 0.25D, 0.035D);
+            sourceLevel.sendParticles(
+                    new BlockParticleOption(ParticleTypes.BLOCK, state),
+                    x,
+                    y,
+                    z,
+                    8,
+                    0.25D,
+                    0.25D,
+                    0.25D,
+                    0.04D
+            );
+            sourceLevel.playSound(null, position, SoundEvents.ENCHANTMENT_TABLE_USE, SoundSource.PLAYERS, 0.55F, 1.35F);
+            sourceLevel.playSound(null, position, SoundEvents.AMETHYST_BLOCK_CHIME, SoundSource.PLAYERS, 0.4F, 0.8F);
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+    }
+
+    void erode(BlockPos position, BlockState state, int processed, int effectStride, float pitch) {
+        if (processed % effectStride != 0) {
+            return;
+        }
+        try {
+            double x = position.getX() + 0.5D;
+            double y = position.getY() + 0.5D;
+            double z = position.getZ() + 0.5D;
+            sourceLevel.sendParticles(
+                    new BlockParticleOption(ParticleTypes.BLOCK, state),
+                    x,
+                    y,
+                    z,
+                    5,
+                    0.3D,
+                    0.3D,
+                    0.3D,
+                    0.04D
+            );
+            sourceLevel.sendParticles(ParticleTypes.ENCHANT, x, y, z, 3, 0.28D, 0.28D, 0.28D, 0.12D);
+            sourceLevel.playSound(null, position, SoundEvents.AMETHYST_BLOCK_CHIME, SoundSource.PLAYERS, 0.22F, pitch);
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+    }
+
+    synchronized boolean route(Iterable<ItemStack> drops) {
+        for (ItemStack drop : drops) {
+            if (drop != null && !drop.isEmpty()) {
+                pendingDrops.add(drop.copy());
+            }
+        }
+        scheduleFlush();
+        return true;
+    }
+
+    synchronized void flush() {
+        flushScheduled = false;
+        if (pendingDrops.isEmpty()) {
+            return;
+        }
+        List<ItemStack> drops = consolidateDrops(pendingDrops);
+        pendingDrops.clear();
+        boolean atPlayer = !player.isRemoved() && player.level() == sourceLevel;
+        double x = atPlayer ? player.getX() : fallbackX;
+        double y = atPlayer ? player.getY() + 0.15D : fallbackY;
+        double z = atPlayer ? player.getZ() : fallbackZ;
+        if (atPlayer) {
+            fallbackX = x;
+            fallbackY = y;
+            fallbackZ = z;
+        }
+        int delivered = 0;
+        for (ItemStack drop : drops) {
+            try {
+                ItemEntity item = new ItemEntity(sourceLevel, x, y, z, drop, 0D, 0.08D, 0D);
+                item.setDefaultPickUpDelay();
+                if (sourceLevel.addFreshEntity(item)) {
+                    delivered++;
+                } else {
+                    pendingDrops.add(drop.copy());
+                }
+            } catch (Throwable error) {
+                pendingDrops.add(drop.copy());
+                reportDeliveryFailure(error);
+            }
+        }
+        try {
+            int particles = Math.min(32, 6 + (delivered * 2));
+            sourceLevel.sendParticles(ParticleTypes.ENCHANT, x, y + 0.35D, z, particles, 0.3D, 0.25D, 0.3D, 0.1D);
+            sourceLevel.playSound(null, x, y, z, SoundEvents.AMETHYST_BLOCK_CHIME, SoundSource.PLAYERS, 0.28F, 1.75F);
+        } catch (Throwable error) {
+            reportEffectFailure(error);
+        }
+        if (!pendingDrops.isEmpty()) {
+            scheduleFlush();
+        }
+    }
+
+    synchronized void finish() {
+        flush();
+    }
+
+    private synchronized void scheduleFlush() {
+        if (pendingDrops.isEmpty() || flushScheduled) {
+            return;
+        }
+        ModdedScheduler scheduler = ModdedEngineBootstrap.schedulerOrNull();
+        if (scheduler == null) {
+            flush();
+            return;
+        }
+        flushScheduled = true;
+        scheduler.laterGlobal(this::flush, 1);
+    }
+
+    private static void mergeDrop(List<ItemStack> consolidated, ItemStack drop) {
+        if (drop == null || drop.isEmpty()) {
+            return;
+        }
+        ItemStack remaining = drop.copy();
+        for (ItemStack existing : consolidated) {
+            if (!ItemStack.isSameItemSameComponents(existing, remaining)) {
+                continue;
+            }
+            int capacity = existing.getMaxStackSize() - existing.getCount();
+            if (capacity <= 0) {
+                continue;
+            }
+            int moved = Math.min(capacity, remaining.getCount());
+            existing.grow(moved);
+            remaining.shrink(moved);
+            if (remaining.isEmpty()) {
+                return;
+            }
+        }
+        while (!remaining.isEmpty()) {
+            int amount = Math.min(remaining.getCount(), remaining.getMaxStackSize());
+            consolidated.add(remaining.copyWithCount(amount));
+            remaining.shrink(amount);
+        }
+    }
+
+    private void reportEffectFailure(Throwable error) {
+        if (effectFailureReported.compareAndSet(false, true)) {
+            LOGGER.error("Iris modded tree-feller presentation failed", error);
+        }
+    }
+
+    private void reportDeliveryFailure(Throwable error) {
+        if (deliveryFailureReported.compareAndSet(false, true)) {
+            LOGGER.error("Iris modded tree-feller drop delivery failed", error);
+        }
+    }
+}

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

@@ -0,0 +1,554 @@
+package art.arcane.iris.modded.service;
+
+import art.arcane.iris.core.IrisSettings;
+import art.arcane.iris.core.service.tree.TreeDefinitionIndex;
+import art.arcane.iris.core.service.tree.TreeMarkerTraversal;
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.StructurePlacementMarker;
+import art.arcane.iris.engine.framework.TreeBlockMaterial;
+import art.arcane.iris.modded.ModdedBlockBreakHandler;
+import art.arcane.iris.modded.ModdedBlockState;
+import art.arcane.iris.modded.ModdedEngineBootstrap;
+import art.arcane.iris.modded.ModdedScheduler;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.tags.ItemTags;
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.WeakHashMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.BooleanSupplier;
+
+public final class ModdedTreeFellerService implements ModdedTickableService {
+    private static final Logger LOGGER = LoggerFactory.getLogger("Iris");
+    private static final ThreadLocal<Integer> BREAK_PROBE_DEPTH = ThreadLocal.withInitial(() -> 0);
+
+    private final AtomicBoolean enabled = new AtomicBoolean();
+    private final Set<TreeClaim> activeClaims = ConcurrentHashMap.newKeySet();
+    private final Set<FellingRun> activeRuns = ConcurrentHashMap.newKeySet();
+    private final Map<Engine, TreeDefinitionIndex> definitions = Collections.synchronizedMap(new WeakHashMap<>());
+
+    public static boolean isBreakProbe() {
+        return BREAK_PROBE_DEPTH.get() > 0;
+    }
+
+    public static boolean runBreakProbe(BooleanSupplier probe) {
+        int depth = BREAK_PROBE_DEPTH.get();
+        BREAK_PROBE_DEPTH.set(depth + 1);
+        try {
+            return probe.getAsBoolean();
+        } finally {
+            if (depth == 0) {
+                BREAK_PROBE_DEPTH.remove();
+            } else {
+                BREAK_PROBE_DEPTH.set(depth);
+            }
+        }
+    }
+
+    @Override
+    public void onEnable() {
+        enabled.set(true);
+    }
+
+    @Override
+    public void onDisable() {
+        enabled.set(false);
+        for (FellingRun run : List.copyOf(activeRuns)) {
+            finish(run);
+        }
+        activeRuns.clear();
+        activeClaims.clear();
+        definitions.clear();
+    }
+
+    @Override
+    public void onServerTick(MinecraftServer server) {
+        for (FellingRun run : List.copyOf(activeRuns)) {
+            if (!isRunControlActive(run)) {
+                finish(run);
+            }
+        }
+    }
+
+    public PreparedOrigin prepare(
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState state
+    ) {
+        IrisSettings.IrisSettingsTreeFeller settings = IrisSettings.get().getTreeFeller();
+        if (!enabled.get()
+                || settings == null
+                || !settings.isEnabled()
+                || !player.gameMode().isSurvival()
+                || !player.isShiftKeyDown()
+                || !state.is(BlockTags.LOGS)
+                || !player.getInventory().getSelectedItem().is(ItemTags.AXES)
+                || !ModdedEngineBootstrap.loader().hasTreeFellerPermission(player)) {
+            return null;
+        }
+        Engine engine = ModdedBlockBreakHandler.engineFor(level);
+        if (engine == null || engine.isClosed()) {
+            return null;
+        }
+        int minimumY = level.getMinY();
+        String marker = markerAt(engine, minimumY, position);
+        StructurePlacementMarker.Decoded decoded = StructurePlacementMarker.decode(marker);
+        if (decoded == null || decoded.structureAware()) {
+            return null;
+        }
+        TreeBlockMaterial expectedMaterial = materialAt(engine, minimumY, position);
+        if (expectedMaterial != null && !expectedMaterial.matches(ModdedBlockState.serialize(state))) {
+            return null;
+        }
+        if (expectedMaterial == null
+                && !decoded.objectKey().startsWith("trees/")
+                && !definitionIndex(engine).isTreeMarker(marker)) {
+            return null;
+        }
+        ItemStack tool = player.getInventory().getSelectedItem();
+        return new PreparedOrigin(
+                this,
+                level,
+                player,
+                position.immutable(),
+                state,
+                engine,
+                marker,
+                minimumY,
+                level.getMaxY(),
+                player.getInventory().getSelectedSlot(),
+                tool.copy(),
+                settings.getDurabilityPreservationChance()
+        );
+    }
+
+    public OriginDropRoute completeOrigin(PreparedOrigin prepared) {
+        if (prepared == null
+                || prepared.owner() != this
+                || !enabled.get()
+                || prepared.engine().isClosed()) {
+            return null;
+        }
+        TreeClaim claim = new TreeClaim(prepared.level(), prepared.marker());
+        if (!activeClaims.add(claim)) {
+            return null;
+        }
+        ModdedTreeFellerPresentation presentation = new ModdedTreeFellerPresentation(
+                prepared.player(),
+                prepared.level()
+        );
+        FellingRun run = new FellingRun(claim, prepared, presentation);
+        if (!normalizeOriginTool(run)) {
+            activeClaims.remove(claim);
+            return null;
+        }
+        activeRuns.add(run);
+        presentation.activate(prepared.position(), prepared.state());
+        OriginDropRoute route = presentation::route;
+        if (run.toolBroken) {
+            ModdedBlockBreakHandler.completeManagedBreak(prepared.level(), prepared.position());
+            finish(run);
+            return route;
+        }
+        discover(run);
+        return route;
+    }
+
+    private TreeDefinitionIndex definitionIndex(Engine engine) {
+        synchronized (definitions) {
+            return definitions.computeIfAbsent(engine, TreeDefinitionIndex::build);
+        }
+    }
+
+    private boolean normalizeOriginTool(FellingRun run) {
+        PreparedOrigin prepared = run.prepared;
+        ItemStack before = prepared.toolBefore();
+        ItemStack current = prepared.player().getInventory().getItem(prepared.heldSlot());
+        boolean currentMatches = !current.isEmpty()
+                && ItemStack.matchesIgnoringComponents(
+                before,
+                current,
+                (componentType) -> componentType == DataComponents.DAMAGE
+        );
+        if (!before.isDamageableItem()) {
+            if (!currentMatches || !ItemStack.isSameItemSameComponents(before, current)) {
+                return false;
+            }
+            run.expectedTool = current.copy();
+            return true;
+        }
+
+        boolean preserve = ThreadLocalRandom.current().nextInt(100) < prepared.preservationChance();
+        int desiredDamage = before.getDamageValue() + (preserve ? 0 : 1);
+        if (desiredDamage >= before.getMaxDamage()) {
+            if (!current.isEmpty() && !currentMatches) {
+                return false;
+            }
+            Item brokenItem = before.getItem();
+            prepared.player().getInventory().setItem(prepared.heldSlot(), ItemStack.EMPTY);
+            if (!current.isEmpty()) {
+                prepared.player().onEquippedItemBroken(brokenItem, EquipmentSlot.MAINHAND);
+            }
+            prepared.player().inventoryMenu.sendAllDataToRemote();
+            run.expectedTool = ItemStack.EMPTY;
+            run.toolBroken = true;
+            return true;
+        }
+        if (!current.isEmpty() && !currentMatches) {
+            return false;
+        }
+        ItemStack normalized = before.copy();
+        normalized.setDamageValue(desiredDamage);
+        prepared.player().getInventory().setItem(prepared.heldSlot(), normalized);
+        prepared.player().inventoryMenu.sendAllDataToRemote();
+        run.expectedTool = normalized.copy();
+        return true;
+    }
+
+    private void discover(FellingRun run) {
+        ModdedScheduler scheduler = ModdedEngineBootstrap.schedulerOrNull();
+        if (scheduler == null) {
+            ModdedBlockBreakHandler.completeManagedBreak(run.prepared.level(), run.prepared.position());
+            finish(run);
+            return;
+        }
+        scheduler.async(() -> {
+            TreeMarkerTraversal.Discovery discovery;
+            try {
+                PreparedOrigin prepared = run.prepared;
+                TreeMarkerTraversal.Position trigger = positionOf(prepared.position());
+                discovery = TreeMarkerTraversal.discover(
+                        trigger,
+                        prepared.marker(),
+                        prepared.minimumY(),
+                        prepared.maximumY(),
+                        (x, y, z) -> markerAt(prepared.engine(), prepared.minimumY(), x, y, z)
+                );
+            } catch (Throwable error) {
+                LOGGER.error("Iris modded tree-feller discovery failed", error);
+                discovery = new TreeMarkerTraversal.Discovery(List.of(), false);
+            }
+            TreeMarkerTraversal.Discovery resolved = discovery;
+            scheduler.global(() -> beginErosion(run, resolved));
+        });
+    }
+
+    private void beginErosion(FellingRun run, TreeMarkerTraversal.Discovery discovery) {
+        ModdedBlockBreakHandler.completeManagedBreak(run.prepared.level(), run.prepared.position());
+        if (run.finished.get() || !discovery.complete()) {
+            finish(run);
+            return;
+        }
+        TreeMarkerTraversal.Position trigger = positionOf(run.prepared.position());
+        run.work = discovery.members().stream()
+                .filter((position) -> !position.equals(trigger))
+                .toList();
+        if (run.work.isEmpty()) {
+            finish(run);
+            return;
+        }
+        run.blocksPerPulse = ModdedTreeFellerPresentation.blocksPerPulse(run.work.size());
+        run.effectStride = ModdedTreeFellerPresentation.effectStride(run.blocksPerPulse);
+        scheduleNextPulse(run);
+    }
+
+    private void scheduleNextPulse(FellingRun run) {
+        ModdedScheduler scheduler = ModdedEngineBootstrap.schedulerOrNull();
+        if (scheduler == null) {
+            finish(run);
+            return;
+        }
+        scheduler.laterGlobal(() -> processPulse(run), 1);
+    }
+
+    private void processPulse(FellingRun run) {
+        if (run.finished.get() || !isRunControlActive(run)) {
+            finish(run);
+            return;
+        }
+        int processedThisPulse = 0;
+        while (processedThisPulse < run.blocksPerPulse && run.cursor < run.work.size()) {
+            if (!isRunControlActive(run)) {
+                finish(run);
+                return;
+            }
+            TreeMarkerTraversal.Position position = run.work.get(run.cursor++);
+            MemberResult result = processMember(run, position);
+            if (result == MemberResult.STOP) {
+                finish(run);
+                return;
+            }
+            processedThisPulse++;
+        }
+        run.presentation.flush();
+        if (run.cursor >= run.work.size()) {
+            finish(run);
+            return;
+        }
+        scheduleNextPulse(run);
+    }
+
+    private MemberResult processMember(FellingRun run, TreeMarkerTraversal.Position position) {
+        PreparedOrigin prepared = run.prepared;
+        BlockPos blockPosition = blockPosition(position);
+        ServerLevel level = prepared.level();
+        if (!level.isLoaded(blockPosition)) {
+            return MemberResult.STOP;
+        }
+        BlockState state = level.getBlockState(blockPosition);
+        if (state.isAir()) {
+            ModdedBlockBreakHandler.completeManagedBreak(level, blockPosition);
+            return MemberResult.CONTINUE;
+        }
+        if (!prepared.marker().equals(markerAt(prepared.engine(), prepared.minimumY(), blockPosition))) {
+            return MemberResult.STOP;
+        }
+        TreeBlockMaterial expectedMaterial = materialAt(prepared.engine(), prepared.minimumY(), blockPosition);
+        if (expectedMaterial != null && !expectedMaterial.matches(ModdedBlockState.serialize(state))) {
+            ModdedBlockBreakHandler.completeManagedBreak(level, blockPosition);
+            return state.is(BlockTags.LOGS) ? MemberResult.STOP : MemberResult.CONTINUE;
+        }
+        boolean log = state.is(BlockTags.LOGS);
+        ServerPlayer player = prepared.player();
+        if (!level.mayInteract(player, blockPosition)
+                || player.blockActionRestricted(level, blockPosition, player.gameMode())
+                || !player.getInventory().getSelectedItem().canDestroyBlock(
+                state,
+                level,
+                blockPosition,
+                player
+        )) {
+            return log ? MemberResult.STOP : MemberResult.CONTINUE;
+        }
+        if (!ModdedEngineBootstrap.loader().canTreeFellerBreak(
+                level,
+                player,
+                blockPosition,
+                state
+        )) {
+            return log ? MemberResult.STOP : MemberResult.CONTINUE;
+        }
+        if (!state.equals(level.getBlockState(blockPosition))
+                || !prepared.marker().equals(markerAt(prepared.engine(), prepared.minimumY(), blockPosition))) {
+            return MemberResult.STOP;
+        }
+
+        ItemStack toolForDrops = prepared.player().getInventory().getSelectedItem().copy();
+        BlockEntity blockEntity = state.hasBlockEntity() ? level.getBlockEntity(blockPosition) : null;
+        List<ItemStack> vanillaDrops = Block.getDrops(
+                state,
+                level,
+                blockPosition,
+                blockEntity,
+                player,
+                toolForDrops
+        );
+        ModdedBlockBreakHandler.Result customDrops = ModdedBlockBreakHandler.evaluateManagedDrops(
+                level,
+                blockPosition,
+                state
+        );
+        ToolReservation reservation = log ? reserveToolDamage(run) : ToolReservation.free(toolForDrops);
+        if (reservation == null) {
+            return MemberResult.STOP;
+        }
+        if (!level.destroyBlock(blockPosition, false, player, 512)) {
+            refundToolDamage(run, reservation);
+            return MemberResult.STOP;
+        }
+        ModdedBlockBreakHandler.completeManagedBreak(level, blockPosition);
+        int processed = run.processed++;
+        float progress = run.work.size() <= 1 ? 1F : (float) processed / (float) (run.work.size() - 1);
+        float pitch = Math.min(1.95F, 0.65F + (progress * 1.25F));
+        run.presentation.erode(blockPosition, state, processed, run.effectStride, pitch);
+        run.presentation.route(customDrops.combinedDrops(vanillaDrops));
+        return reservation.broke() ? MemberResult.STOP : MemberResult.CONTINUE;
+    }
+
+    private ToolReservation reserveToolDamage(FellingRun run) {
+        PreparedOrigin prepared = run.prepared;
+        ItemStack current = prepared.player().getInventory().getSelectedItem();
+        if (!ItemStack.isSameItemSameComponents(current, run.expectedTool) || !current.is(ItemTags.AXES)) {
+            return null;
+        }
+        ItemStack before = current.copy();
+        if (!current.isDamageableItem()
+                || ThreadLocalRandom.current().nextInt(100) < prepared.preservationChance()) {
+            return ToolReservation.free(before);
+        }
+        int nextDamage = current.getDamageValue() + 1;
+        if (nextDamage >= current.getMaxDamage()) {
+            Item brokenItem = current.getItem();
+            prepared.player().getInventory().setSelectedItem(ItemStack.EMPTY);
+            prepared.player().onEquippedItemBroken(brokenItem, EquipmentSlot.MAINHAND);
+            prepared.player().inventoryMenu.sendAllDataToRemote();
+            run.expectedTool = ItemStack.EMPTY;
+            return new ToolReservation(before, true, true);
+        }
+        current.setDamageValue(nextDamage);
+        prepared.player().getInventory().setSelectedItem(current);
+        prepared.player().inventoryMenu.sendAllDataToRemote();
+        run.expectedTool = current.copy();
+        return new ToolReservation(before, true, false);
+    }
+
+    private void refundToolDamage(FellingRun run, ToolReservation reservation) {
+        if (!reservation.charged()) {
+            return;
+        }
+        PreparedOrigin prepared = run.prepared;
+        ItemStack current = prepared.player().getInventory().getSelectedItem();
+        boolean expectedEmpty = run.expectedTool.isEmpty();
+        if ((expectedEmpty && current.isEmpty())
+                || (!expectedEmpty && ItemStack.isSameItemSameComponents(current, run.expectedTool))) {
+            ItemStack restored = reservation.before().copy();
+            prepared.player().getInventory().setSelectedItem(restored);
+            prepared.player().inventoryMenu.sendAllDataToRemote();
+            run.expectedTool = restored.copy();
+        }
+    }
+
+    private boolean isRunControlActive(FellingRun run) {
+        PreparedOrigin prepared = run.prepared;
+        ServerPlayer player = prepared.player();
+        IrisSettings.IrisSettingsTreeFeller settings = IrisSettings.get().getTreeFeller();
+        if (!enabled.get()
+                || settings == null
+                || !settings.isEnabled()
+                || run.finished.get()
+                || player.isRemoved()
+                || player.hasDisconnected()
+                || player.level() != prepared.level()
+                || !player.gameMode().isSurvival()
+                || !player.isShiftKeyDown()
+                || player.getInventory().getSelectedSlot() != prepared.heldSlot()
+                || run.expectedTool.isEmpty()) {
+            return false;
+        }
+        ItemStack current = player.getInventory().getSelectedItem();
+        return current.is(ItemTags.AXES) && ItemStack.isSameItemSameComponents(current, run.expectedTool);
+    }
+
+    private void finish(FellingRun run) {
+        if (run.finished.compareAndSet(false, true)) {
+            activeRuns.remove(run);
+            activeClaims.remove(run.claim);
+            ModdedBlockBreakHandler.completeManagedBreak(run.prepared.level(), run.prepared.position());
+            run.presentation.finish();
+        }
+    }
+
+    private String markerAt(Engine engine, int minimumY, BlockPos position) {
+        return markerAt(engine, minimumY, position.getX(), position.getY(), position.getZ());
+    }
+
+    private String markerAt(Engine engine, int minimumY, int x, int y, int z) {
+        return engine.getMantle().getMantle().get(x, y - minimumY, z, String.class);
+    }
+
+    private TreeBlockMaterial materialAt(Engine engine, int minimumY, BlockPos position) {
+        return engine.getMantle().getMantle().get(
+                position.getX(),
+                position.getY() - minimumY,
+                position.getZ(),
+                TreeBlockMaterial.class
+        );
+    }
+
+    private TreeMarkerTraversal.Position positionOf(BlockPos position) {
+        return new TreeMarkerTraversal.Position(position.getX(), position.getY(), position.getZ());
+    }
+
+    private BlockPos blockPosition(TreeMarkerTraversal.Position position) {
+        return new BlockPos(position.x(), position.y(), position.z());
+    }
+
+    public record PreparedOrigin(
+            ModdedTreeFellerService owner,
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState state,
+            Engine engine,
+            String marker,
+            int minimumY,
+            int maximumY,
+            int heldSlot,
+            ItemStack toolBefore,
+            int preservationChance
+    ) {
+        public PreparedOrigin {
+            Objects.requireNonNull(owner, "owner");
+            Objects.requireNonNull(level, "level");
+            Objects.requireNonNull(player, "player");
+            Objects.requireNonNull(position, "position");
+            Objects.requireNonNull(state, "state");
+            Objects.requireNonNull(engine, "engine");
+            Objects.requireNonNull(marker, "marker");
+            Objects.requireNonNull(toolBefore, "toolBefore");
+        }
+    }
+
+    @FunctionalInterface
+    public interface OriginDropRoute {
+        boolean route(Iterable<ItemStack> drops);
+    }
+
+    private enum MemberResult {
+        CONTINUE,
+        STOP
+    }
+
+    private record TreeClaim(ServerLevel level, String marker) {
+    }
+
+    private record ToolReservation(ItemStack before, boolean charged, boolean broke) {
+        private static ToolReservation free(ItemStack before) {
+            return new ToolReservation(before, false, false);
+        }
+    }
+
+    private static final class FellingRun {
+        private final TreeClaim claim;
+        private final PreparedOrigin prepared;
+        private final ModdedTreeFellerPresentation presentation;
+        private final AtomicBoolean finished = new AtomicBoolean();
+        private ItemStack expectedTool = ItemStack.EMPTY;
+        private List<TreeMarkerTraversal.Position> work = List.of();
+        private int cursor;
+        private int processed;
+        private int blocksPerPulse = 1;
+        private int effectStride = 1;
+        private boolean toolBroken;
+
+        private FellingRun(
+                TreeClaim claim,
+                PreparedOrigin prepared,
+                ModdedTreeFellerPresentation presentation
+        ) {
+            this.claim = claim;
+            this.prepared = prepared;
+            this.presentation = presentation;
+        }
+    }
+}

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

@@ -0,0 +1,143 @@
+package art.arcane.iris.modded;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class ModdedGenerationLeaseContractTest {
+    private static final String SOURCE_ROOT_PROPERTY = "iris.moddedCommonSources";
+
+    @Test
+    public void biomeRuntimeReadsAreGenerationLeased() throws IOException {
+        String source = source("art/arcane/iris/modded/IrisModdedBiomeSource.java");
+
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_structure_biome\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_visible_biome\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_biomes_within\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_structure_reachability\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_structure_state_biome\")"));
+        assertTrue(source.contains("tryAcquireGenerationLease(engine, \"modded_structure_biome_keys\")"));
+        assertTrue(source.contains("engine == null || engine.isClosed()"));
+        assertTrue(source.contains("catch (GenerationSessionException e)"));
+        assertTrue(source.contains("e.isExpectedTeardown()"));
+        assertTrue(source.contains("Iris structure biome key lookup was rejected during an engine transition"));
+        assertTrue(source.contains("source.clearCache()"));
+    }
+
+    @Test
+    public void terrainAndHeightQueriesShareGenerationSessions() throws IOException {
+        String source = source("art/arcane/iris/modded/IrisModdedChunkGenerator.java");
+
+        assertTrue(source.contains("generationEngine.acquireGenerationLease(\"modded_chunk_pipeline\")"));
+        assertTrue(source.contains("current.acquireGenerationLease(\"modded_base_height\")"));
+        assertTrue(source.contains("current.acquireGenerationLease(\"modded_base_column\")"));
+        assertTrue(source.contains("current.acquireGenerationLease(\"modded_configured_biome_keys\")"));
+        assertTrue(source.contains("generationEngine.isClosing() || e.isExpectedTeardown()"));
+        String terrain = method(source, "private ChunkAccess generateTerrain(");
+        int sessionFailure = terrain.indexOf("catch (GenerationSessionException e)");
+        int generalFailure = terrain.indexOf("catch (Throwable e)", sessionFailure);
+        String sessionHandler = terrain.substring(sessionFailure, generalFailure);
+        assertTrue(sessionHandler.contains("throw new IllegalStateException"));
+        assertFalse(sessionHandler.contains("return chunk;"));
+
+        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);"));
+    }
+
+    @Test
+    public void preservationDereferencesSharedPackData() throws IOException {
+        String source = source("art/arcane/iris/modded/service/ModdedPreservationService.java");
+        int dereference = source.indexOf("public void dereference()");
+        int irisData = source.indexOf("IrisData.dereference();", dereference);
+        int trackedResources = source.indexOf("threads.removeIf", dereference);
+
+        assertTrue(dereference >= 0);
+        assertTrue(irisData > dereference);
+        assertTrue(trackedResources > irisData);
+    }
+
+    @Test
+    public void hotloadShutdownOnlyTargetsItsOwnWorld() throws IOException {
+        String source = source("art/arcane/iris/modded/service/ModdedStudioHotloadService.java");
+        int shutdown = source.indexOf("public void shutdownPregenerator(Engine engine)");
+        int nextMethod = source.indexOf("private boolean throttled", shutdown);
+        String method = source.substring(shutdown, nextMethod);
+
+        assertTrue(method.contains("ModdedPregenJob.shutdownForWorld(world.identity());"));
+        assertFalse(method.contains("PregeneratorJob.shutdownInstance();"));
+    }
+
+    @Test
+    public void maintenanceOwnsOneGenerationSessionUntilWorkCompletes() throws IOException {
+        String source = source("art/arcane/iris/modded/service/ModdedEngineMaintenanceService.java");
+        String maintain = method(source, "private void maintain(Engine engine, long scheduledAt)");
+
+        assertTrue(maintain.contains("engine.acquireGenerationLease(\"modded_engine_maintenance\")"));
+        assertTrue(maintain.contains("IrisContext.open(engine, lease.sessionId(), null)"));
+        assertTrue(maintain.contains("exception.isExpectedTeardown()"));
+        assertTrue(source.contains("active.awaitTermination(INTERRUPT_DRAIN_TIMEOUT_SECONDS, TimeUnit.SECONDS)"));
+    }
+
+    @Test
+    public void blockingPregenShutdownDefersItsFinalSaveToTheServerThread() throws IOException {
+        String jobSource = source("art/arcane/iris/modded/command/ModdedPregenJob.java");
+        String shutdown = method(jobSource, "private static boolean shutdownAndSave(");
+        assertTrue(shutdown.contains("deferFinalSaveToServerThread()"));
+        assertTrue(shutdown.contains("completeDeferredFinalSave()"));
+        assertTrue(shutdown.contains("cancelDeferredFinalSave()"));
+
+        String methodSource = source("art/arcane/iris/modded/command/ModdedPregenMethod.java");
+        String close = method(methodSource, "public void close()");
+        assertTrue(close.contains("deferFinalSaveIfRequested()"));
+
+        String await = method(methodSource, "private void awaitFinalSave(");
+        assertTrue(await.contains("FINAL_SAVE_POLL_MILLIS"));
+        assertTrue(await.contains("deferFinalSaveIfRequested()"));
+
+        String complete = method(methodSource, "void completeDeferredFinalSave()");
+        int cancel = complete.indexOf("cancelQueuedFinalSave();");
+        int directSave = complete.indexOf("saveLevelOnServerThread();");
+        assertTrue(cancel >= 0);
+        assertTrue(directSave > cancel);
+
+        String queuedSave = method(methodSource, "private void executeFinalSave(");
+        assertTrue(queuedSave.contains("if (!request.claim())"));
+        String cancelRequest = method(methodSource, "private void cancelQueuedFinalSave()");
+        assertTrue(cancelRequest.contains("request.cancel();"));
+        String pending = method(methodSource, "boolean hasPendingFinalSave()");
+        assertTrue(pending.contains("queuedFinalSave.get() != null"));
+    }
+
+    private static String source(String relativePath) throws IOException {
+        String root = System.getProperty(SOURCE_ROOT_PROPERTY);
+        assertTrue("Missing system property " + SOURCE_ROOT_PROPERTY, root != null && !root.isBlank());
+        return Files.readString(Path.of(root, relativePath));
+    }
+
+    private static String method(String source, String signature) {
+        int start = source.indexOf(signature);
+        assertTrue("Missing source contract signature: " + signature, start >= 0);
+        int openBrace = source.indexOf('{', start);
+        assertTrue("Missing source contract method body: " + signature, openBrace >= 0);
+        int depth = 0;
+        for (int index = openBrace; index < source.length(); index++) {
+            char current = source.charAt(index);
+            if (current == '{') {
+                depth++;
+            } else if (current == '}') {
+                depth--;
+                if (depth == 0) {
+                    return source.substring(start, index + 1);
+                }
+            }
+        }
+        throw new IllegalArgumentException("Unclosed source contract method: " + signature);
+    }
+}

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

@@ -141,7 +141,35 @@ public class ModdedLifecycleFailureContractTest {
         String source = source("ModdedEngineBootstrap.java");
         String stop = method(source, "public static void stop(");
 
-        assertEquals(1, occurrences(stop, "ModdedStartup.reset();"));
+        assertEquals(1, occurrences(stop, "ModdedStartup::reset"));
+    }
+
+    @Test
+    public void engineBootstrapAttemptsEveryShutdownStageAndAggregatesFailures() throws IOException {
+        String source = source("ModdedEngineBootstrap.java");
+        String stop = method(source, "public static void stop(");
+
+        assertBefore(stop, "\"services\"", "\"world engines\"");
+        assertBefore(stop, "\"world engines\"", "\"dimension manager\"");
+        assertBefore(stop, "\"server state\"", "if (failure != null)");
+        assertTrue(stop.contains("throw propagateStopFailure(failure);"));
+
+        String runStage = method(source, "private static Throwable runStopStage(");
+        assertTrue(runStage.contains("catch (Throwable stageFailure)"));
+        assertTrue(runStage.contains("failure.addSuppressed(stageFailure);"));
+    }
+
+    @Test
+    public void worldShutdownRemovesOnlySuccessfullyClosedMappings() throws IOException {
+        String source = source("ModdedWorldEngines.java");
+        String shutdown = method(source, "public static void shutdown()");
+
+        assertTrue(shutdown.contains("new ArrayList<>(ENGINES.entrySet())"));
+        assertFalse(shutdown.contains("ENGINES.clear()"));
+        assertBefore(shutdown, "close(engine);", "ENGINES.remove(level, engine)");
+        assertTrue(shutdown.contains("ENGINES.containsKey(level)"));
+        assertTrue(shutdown.contains("failure.addSuppressed(e);"));
+        assertTrue(shutdown.contains("failed mappings were retained"));
     }
 
     @Test
@@ -160,7 +188,37 @@ public class ModdedLifecycleFailureContractTest {
         String unbind = method(source, "synchronized void unbindEngine(ServerLevel level)");
 
         assertFalse(unbind.contains("finally"));
+        assertBefore(unbind, "unloading = true;", "ModdedWorldEngines.evictOrThrow(level);");
         assertBefore(unbind, "ModdedWorldEngines.evictOrThrow(level);", "clearEngineBinding();");
+        String binding = method(source, "private Engine bindEngine(ServerLevel level)");
+        assertTrue(binding.contains("requireBindingAllowed();"));
+        assertTrue(binding.contains("requireCompletedShutdown(cached);"));
+        String bindLevel = method(source, "synchronized void bindLevel(ServerLevel level)");
+        assertBefore(bindLevel, "requireCompletedShutdown(engine);", "unloading = false;");
+        String boundEngine = method(source, "public Engine engineIfBound()");
+        assertTrue(boundEngine.contains("unloading || current == null || current.isClosing() || current.isClosed()"));
+    }
+
+    @Test
+    public void loaderUnloadSurfacesCloseFailureAndDynamicRemovalUsesStrictEviction() throws IOException {
+        String bootstrapSource = source("ModdedEngineBootstrap.java");
+        String unload = method(bootstrapSource, "public static void levelUnloaded(ServerLevel level)");
+        String failure = catchBlock(unload);
+        assertTrue(failure.contains("LOGGER.error("));
+        assertTrue(failure.contains("throw "));
+
+        String managerSource = source("ModdedDimensionManager.java");
+        String remove = method(managerSource, "public static boolean remove(MinecraftServer server, String dimensionId, boolean wipeStorage)");
+        assertTrue(remove.contains("ModdedWorldEngines.evictOrThrow(level);"));
+        assertFalse(remove.contains("ModdedWorldEngines.evict(level);"));
+        assertTrue(remove.contains("generatorUnbound = true;"));
+        assertTrue(remove.contains("rollbackRemoval(server, serverAccess, key, level, generator, generatorUnbound, e);"));
+
+        String rollback = method(managerSource, "private static void rollbackRemoval(");
+        assertTrue(rollback.contains("serverAccess.hasLevel(server, key)"));
+        assertTrue(rollback.contains("generator.bindLevel(level);"));
+        assertTrue(rollback.contains("failure.addSuppressed(rollbackFailure);"));
+        assertTrue(rollback.contains("LOGGER.error("));
     }
 
     @Test

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

@@ -48,7 +48,28 @@ public class ModdedServiceManagerTest {
         assertNull(manager.service(SecondService.class));
     }
 
+    @Test
+    public void disableAttemptsEveryServiceInReverseOrderAndAggregatesFailures() {
+        ModdedServiceManager manager = new ModdedServiceManager();
+        RuntimeException firstFailure = new RuntimeException("first disable failed");
+        RuntimeException secondFailure = new RuntimeException("second disable failed");
+        FirstService first = manager.register(FirstService.class, new FirstService());
+        first.disableFailure = firstFailure;
+        SecondService second = manager.register(
+                SecondService.class, new SecondService(null, secondFailure));
+
+        manager.enableAll();
+        IllegalStateException thrown = assertThrows(IllegalStateException.class, manager::disableAll);
+
+        assertEquals(1, first.disableCount);
+        assertEquals(1, second.disableCount);
+        assertSame(secondFailure, thrown.getCause());
+        assertEquals(1, secondFailure.getSuppressed().length);
+        assertSame(firstFailure, secondFailure.getSuppressed()[0]);
+    }
+
     private static final class FirstService implements ModdedService {
+        private RuntimeException disableFailure;
         private int enableCount;
         private int disableCount;
 
@@ -60,6 +81,9 @@ public class ModdedServiceManagerTest {
         @Override
         public void onDisable() {
             disableCount++;
+            if (disableFailure != null) {
+                throw disableFailure;
+            }
         }
     }
 

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

@@ -0,0 +1,54 @@
+package art.arcane.iris.modded.service;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.core.component.DataComponentMap;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class ModdedTreeFellerPresentationTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        DataComponentMap stackComponents = DataComponentMap.builder()
+                .set(DataComponents.MAX_STACK_SIZE, 64)
+                .build();
+        if (!Items.OAK_LOG.builtInRegistryHolder().areComponentsBound()) {
+            Items.OAK_LOG.builtInRegistryHolder().bindComponents(stackComponents);
+        }
+        if (!Items.BIRCH_LOG.builtInRegistryHolder().areComponentsBound()) {
+            Items.BIRCH_LOG.builtInRegistryHolder().bindComponents(stackComponents);
+        }
+    }
+
+    @Test
+    public void pulseSizingKeepsErosionReadableAndBounded() {
+        assertEquals(4, ModdedTreeFellerPresentation.blocksPerPulse(1));
+        assertEquals(4, ModdedTreeFellerPresentation.blocksPerPulse(240));
+        assertEquals(10, ModdedTreeFellerPresentation.blocksPerPulse(600));
+        assertEquals(64, ModdedTreeFellerPresentation.blocksPerPulse(100_000));
+        assertEquals(4, ModdedTreeFellerPresentation.effectStride(64));
+    }
+
+    @Test
+    public void compatibleDropsConsolidateWithoutExceedingStackLimits() {
+        List<ItemStack> drops = ModdedTreeFellerPresentation.consolidateDrops(List.of(
+                new ItemStack(Items.OAK_LOG, 48),
+                new ItemStack(Items.OAK_LOG, 48),
+                new ItemStack(Items.BIRCH_LOG, 3)
+        ));
+
+        assertEquals(3, drops.size());
+        assertEquals(64, drops.get(0).getCount());
+        assertEquals(32, drops.get(1).getCount());
+        assertEquals(3, drops.get(2).getCount());
+    }
+}

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

@@ -0,0 +1,37 @@
+package art.arcane.iris.modded.service;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+public class ModdedTreeFellerServiceTest {
+    @Test
+    public void syntheticBreakProbeDepthIsNestedAndRestored() {
+        assertFalse(ModdedTreeFellerService.isBreakProbe());
+
+        boolean accepted = ModdedTreeFellerService.runBreakProbe(() -> {
+            assertTrue(ModdedTreeFellerService.isBreakProbe());
+            return ModdedTreeFellerService.runBreakProbe(() -> {
+                assertTrue(ModdedTreeFellerService.isBreakProbe());
+                return true;
+            });
+        });
+
+        assertTrue(accepted);
+        assertFalse(ModdedTreeFellerService.isBreakProbe());
+    }
+
+    @Test
+    public void syntheticBreakProbeDepthIsRestoredAfterFailure() {
+        try {
+            ModdedTreeFellerService.runBreakProbe(() -> {
+                throw new IllegalStateException("probe failure");
+            });
+            fail("Expected probe failure");
+        } catch (IllegalStateException expected) {
+            assertFalse(ModdedTreeFellerService.isBreakProbe());
+        }
+    }
+}

adapters/neoforge/src/main/java/art/arcane/iris/neoforge/IrisNeoForgeBootstrap.java

@@ -27,6 +27,7 @@ import art.arcane.iris.modded.command.ModdedWandService;
 import com.mojang.serialization.MapCodec;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.packs.PackType;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.entity.item.ItemEntity;
@@ -34,15 +35,18 @@ import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.neoforged.api.distmarker.Dist;
+import net.neoforged.bus.api.EventPriority;
 import net.neoforged.bus.api.IEventBus;
 import net.neoforged.fml.common.Mod;
 import net.neoforged.fml.loading.FMLEnvironment;
 import net.neoforged.fml.loading.FMLLoader;
 import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.util.BlockSnapshot;
 import net.neoforged.neoforge.event.AddPackFindersEvent;
 import net.neoforged.neoforge.event.RegisterCommandsEvent;
 import net.neoforged.neoforge.event.entity.player.PlayerInteractEvent;
 import net.neoforged.neoforge.event.level.BlockDropsEvent;
+import net.neoforged.neoforge.event.level.BlockEvent;
 import net.neoforged.neoforge.event.level.LevelEvent;
 import net.neoforged.neoforge.event.level.block.BreakBlockEvent;
 import net.neoforged.neoforge.event.server.ServerAboutToStartEvent;
@@ -51,6 +55,9 @@ import net.neoforged.neoforge.event.server.ServerStartingEvent;
 import net.neoforged.neoforge.event.server.ServerStoppingEvent;
 import net.neoforged.neoforge.event.tick.ServerTickEvent;
 import net.neoforged.neoforge.registries.DeferredRegister;
+import net.neoforged.neoforge.server.permission.events.PermissionGatherEvent;
+
+import java.util.List;
 
 @Mod("irisworldgen")
 public final class IrisNeoForgeBootstrap {
@@ -82,18 +89,55 @@ public final class IrisNeoForgeBootstrap {
                 ModdedEngineBootstrap.levelLoaded(level);
             }
         });
-        NeoForge.EVENT_BUS.addListener((RegisterCommandsEvent event) -> IrisModdedCommands.register(event.getDispatcher()));
-        NeoForge.EVENT_BUS.addListener((BreakBlockEvent event) -> {
-            if (event.getLevel() instanceof ServerLevel level && !event.isCanceled()) {
-                ModdedBlockBreakHandler.prepare(level, event.getPos(), event.getState());
+        NeoForge.EVENT_BUS.addListener((LevelEvent.Unload event) -> {
+            if (event.getLevel() instanceof ServerLevel level) {
+                ModdedEngineBootstrap.levelUnloaded(level);
             }
         });
+        NeoForge.EVENT_BUS.addListener((RegisterCommandsEvent event) -> IrisModdedCommands.register(event.getDispatcher()));
+        NeoForge.EVENT_BUS.addListener((PermissionGatherEvent.Nodes event) ->
+                event.addNodes(NeoForgeModdedLoader.TREE_FELLER_PERMISSION));
+        NeoForge.EVENT_BUS.addListener((BreakBlockEvent event) -> {
+            if (event.getLevel() instanceof ServerLevel level
+                    && event.getPlayer() instanceof ServerPlayer player
+                    && !event.isCanceled()) {
+                ModdedBlockBreakHandler.prepare(level, player, event.getPos(), event.getState());
+            }
+        });
+        NeoForge.EVENT_BUS.addListener(
+                EventPriority.LOWEST,
+                false,
+                (BlockEvent.EntityPlaceEvent event) -> {
+                    if (!(event instanceof BlockEvent.EntityMultiPlaceEvent)
+                            && event.getLevel() instanceof ServerLevel level) {
+                        ModdedBlockBreakHandler.clearPlacedProvenance(level, event.getPos());
+                    }
+                }
+        );
+        NeoForge.EVENT_BUS.addListener(
+                EventPriority.LOWEST,
+                false,
+                (BlockEvent.EntityMultiPlaceEvent event) -> {
+                    for (BlockSnapshot snapshot : event.getReplacedBlockSnapshots()) {
+                        if (snapshot.getLevel() instanceof ServerLevel level) {
+                            ModdedBlockBreakHandler.clearPlacedProvenance(level, snapshot.getPos());
+                        }
+                    }
+                }
+        );
         NeoForge.EVENT_BUS.addListener((BlockDropsEvent event) -> {
             if (!(event.getBreaker() instanceof Player)) {
                 return;
             }
             ServerLevel level = event.getLevel();
             ModdedBlockBreakHandler.Result result = ModdedBlockBreakHandler.complete(level, event.getPos(), event.getState());
+            List<ItemStack> vanillaDrops = event.getDrops().stream()
+                    .map(ItemEntity::getItem)
+                    .toList();
+            if (result.routeCombinedDrops(vanillaDrops)) {
+                event.getDrops().clear();
+                return;
+            }
             if (result.replaceVanillaDrops()) {
                 event.getDrops().clear();
             }

adapters/neoforge/src/main/java/art/arcane/iris/neoforge/NeoForgeModdedLoader.java

@@ -19,18 +19,37 @@
 package art.arcane.iris.neoforge;
 
 import art.arcane.iris.modded.ModdedLoader;
+import art.arcane.iris.modded.service.ModdedTreeFellerService;
+import net.minecraft.commands.Commands;
+import net.minecraft.core.BlockPos;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.block.state.BlockState;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.event.level.block.BreakBlockEvent;
 import net.neoforged.fml.ModList;
 import net.neoforged.fml.loading.FMLEnvironment;
 import net.neoforged.fml.loading.FMLLoader;
 import net.neoforged.fml.loading.FMLPaths;
 import net.neoforged.neoforge.server.ServerLifecycleHooks;
+import net.neoforged.neoforge.server.permission.PermissionAPI;
+import net.neoforged.neoforge.server.permission.nodes.PermissionNode;
+import net.neoforged.neoforge.server.permission.nodes.PermissionTypes;
 import net.neoforged.neoforgespi.language.IModFileInfo;
 
 import java.io.File;
 import java.nio.file.Path;
 
 public final class NeoForgeModdedLoader implements ModdedLoader {
+    public static final PermissionNode<Boolean> TREE_FELLER_PERMISSION = new PermissionNode<>(
+            "iris",
+            "treefeller",
+            PermissionTypes.BOOLEAN,
+            (player, playerId, contexts) ->
+                    player != null && Commands.LEVEL_GAMEMASTERS.check(player.permissions())
+    );
+
     @Override
     public String platformName() {
         return "neoforge";
@@ -73,4 +92,23 @@ public final class NeoForgeModdedLoader implements ModdedLoader {
         IModFileInfo info = ModList.get().getModFileById("irisworldgen");
         return info == null ? null : info.getFile().getFilePath().toFile();
     }
+
+    @Override
+    public boolean hasTreeFellerPermission(ServerPlayer player) {
+        return PermissionAPI.getPermission(player, TREE_FELLER_PERMISSION);
+    }
+
+    @Override
+    public boolean canTreeFellerBreak(
+            ServerLevel level,
+            ServerPlayer player,
+            BlockPos position,
+            BlockState state
+    ) {
+        return ModdedTreeFellerService.runBreakProbe(() -> {
+            BreakBlockEvent event = new BreakBlockEvent(level, position, state, player);
+            NeoForge.EVENT_BUS.post(event);
+            return !event.isCanceled();
+        });
+    }
 }

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

@@ -45,6 +45,7 @@ public class IrisSettings {
     private IrisSettingsPerformance performance = new IrisSettingsPerformance();
     private IrisSettingsPregen pregen = new IrisSettingsPregen();
     private IrisSettingsSentry sentry = new IrisSettingsSentry();
+    private IrisSettingsTreeFeller treeFeller = new IrisSettingsTreeFeller();
 
     public static int getThreadCount(int c) {
         return Math.max(switch (c) {
@@ -229,16 +230,8 @@ public class IrisSettings {
         public int noiseCacheSize = 1_024;
         public int resourceLoaderCacheSize = 1_024;
         public int objectLoaderCacheSize = 4_096;
-        public int tectonicPlateSize = -1;
         public int mantleCleanupDelay = 200;
         public boolean simdKernels = true;
-
-        public int getTectonicPlateSize() {
-            if (tectonicPlateSize > 0)
-                return tectonicPlateSize;
-
-            return (int) (getHardware.getProcessMemory() / 512L);
-        }
     }
 
     @Data
@@ -286,6 +279,16 @@ public class IrisSettings {
         public boolean preventLeafDecay = true;
     }
 
+    @Data
+    public static class IrisSettingsTreeFeller {
+        public boolean enabled = false;
+        public int durabilityPreservationChance = 0;
+
+        public int getDurabilityPreservationChance() {
+            return Math.max(0, Math.min(durabilityPreservationChance, 100));
+        }
+    }
+
     @Data
     public static class IrisSettingsStudio {
         public boolean studio = true;
@@ -300,9 +303,22 @@ public class IrisSettings {
         public boolean useVirtualThreads = true;
         public boolean forceMulticoreWrite = false;
         public int priority = Thread.NORM_PRIORITY;
+        public int parallelism = -1;
 
         public int getPriority() {
             return Math.max(Math.min(priority, Thread.MAX_PRIORITY), Thread.MIN_PRIORITY);
         }
+
+        public int getParallelism() {
+            int processors = Math.max(1, Runtime.getRuntime().availableProcessors());
+            if (parallelism > 0) {
+                int maximumParallelism = processors > Integer.MAX_VALUE / 2
+                        ? Integer.MAX_VALUE
+                        : processors * 2;
+                return Math.min(parallelism, maximumParallelism);
+            }
+
+            return Math.max(1, (int) Math.ceil(Math.sqrt(processors)));
+        }
     }
 }

core/src/main/java/art/arcane/iris/core/gui/PregeneratorJob.java

@@ -45,6 +45,7 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 
 public class PregeneratorJob implements PregenListener, PregenRenderSource {
+    private static final long WORLD_SHUTDOWN_TIMEOUT_MILLIS = 15_000L;
     private static final Color COLOR_EXISTS = parseColor("#4d7d5b");
     private static final Color COLOR_BLACK = parseColor("#4d7d5b");
     private static final Color COLOR_MANTLE = parseColor("#3c2773");
@@ -130,18 +131,36 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
         return true;
     }
 
+    public static boolean shutdownInstanceForWorld(String worldIdentity) {
+        PregeneratorJob inst = instance.get();
+        if (inst == null || !inst.targetsWorldIdentity(worldIdentity)) {
+            return false;
+        }
+
+        return shutdownAndWait(inst, WORLD_SHUTDOWN_TIMEOUT_MILLIS);
+    }
+
     public static boolean shutdownAndWait(long timeoutMs) {
         PregeneratorJob inst = instance.get();
         if (inst == null) {
             return false;
         }
 
+        return shutdownAndWait(inst, timeoutMs);
+    }
+
+    private static boolean shutdownAndWait(PregeneratorJob inst, long timeoutMs) {
         inst.pregenerator.close();
         inst.worker.interrupt();
         try {
-            inst.worker.join(timeoutMs);
+            inst.worker.join(Math.max(1L, timeoutMs));
         } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
+            throw new IllegalStateException("Interrupted while stopping the Iris pregenerator.", e);
+        }
+        if (inst.worker.isAlive()) {
+            throw new IllegalStateException("Timed out while stopping the Iris pregenerator after "
+                    + Math.max(1L, timeoutMs) + "ms.");
         }
         instance.compareAndSet(inst, null);
         return true;
@@ -184,7 +203,7 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
         return inst == null ? -1L : Math.max(0L, inst.lastChunksRemaining);
     }
 
-    public record PregenProgress(double percent, long generated, long totalChunks, double chunksPerSecond, long chunksRemaining, long eta, long elapsed, String method, boolean paused, long failed, String worldName) {
+    public record PregenProgress(double percent, long generated, long totalChunks, double chunksPerSecond, long chunksRemaining, long eta, long elapsed, String method, boolean paused, long failed, String worldName, String worldIdentity) {
     }
 
     public static PregenProgress progressSnapshot() {
@@ -205,7 +224,8 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
                 inst.lastMethod,
                 inst.paused(),
                 inst.pregenerator.getFailedChunks(),
-                inst.worldName());
+                inst.worldName(),
+                inst.worldIdentity());
     }
 
     public String worldName() {
@@ -216,6 +236,13 @@ public class PregeneratorJob implements PregenListener, PregenRenderSource {
         return engine.getWorld().name();
     }
 
+    public String worldIdentity() {
+        if (engine == null || engine.getWorld() == null) {
+            return null;
+        }
+        return engine.getWorld().identity();
+    }
+
     public boolean targetsWorldIdentity(String worldIdentity) {
         if (worldIdentity == null || engine == null || engine.getWorld() == null) {
             return false;

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

@@ -65,7 +65,11 @@ import art.arcane.iris.util.common.parallel.MultiBurst;
 import art.arcane.iris.util.common.reflect.KeyedType;
 import art.arcane.volmlib.util.scheduling.ChronoLatch;
 import art.arcane.iris.util.common.scheduling.J;
+import art.arcane.iris.util.project.context.IrisContext;
+import lombok.AccessLevel;
 import lombok.Data;
+import lombok.Getter;
+import lombok.Setter;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
@@ -73,15 +77,20 @@ import java.io.FileReader;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 @Data
 public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
-    private static final KMap<File, IrisData> dataLoaders = new KMap<>();
+    private static final Map<File, IrisData> dataLoaders = new ConcurrentHashMap<>();
     private final File dataFolder;
     private final int id;
     private final boolean datapackCompiler;
@@ -108,14 +117,15 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
     private Gson snippetLoader;
     private GsonBuilder builder;
     private KMap<Class<? extends IrisRegistrant>, ResourceLoader<? extends IrisRegistrant>> loaders = new KMap<>();
-    private Engine engine;
+    @Getter(AccessLevel.NONE)
+    @Setter(AccessLevel.NONE)
+    private final transient List<Engine> engines = new ArrayList<>();
 
     private IrisData(File dataFolder) {
         this(dataFolder, false);
     }
 
     private IrisData(File dataFolder, boolean datapackCompiler) {
-        this.engine = null;
         this.dataFolder = dataFolder;
         this.id = RNG.r.imax();
         this.datapackCompiler = datapackCompiler;
@@ -130,6 +140,10 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
         return dataLoaders.computeIfAbsent(dataFolder, IrisData::new);
     }
 
+    public static IrisData openRuntime(File dataFolder) {
+        return new IrisData(dataFolder);
+    }
+
     public static IrisData openDatapackCompiler(File dataFolder) {
         return new IrisData(dataFolder, true);
     }
@@ -275,9 +289,72 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
     }
 
     public void cleanupEngine() {
-        if (engine != null && engine.isClosed()) {
-            engine = null;
-            IrisLogging.debug("Dereferenced Data<Engine> " + getId() + " " + getDataFolder());
+        int removed;
+        synchronized (engines) {
+            int previousSize = engines.size();
+            removeClosedEngines();
+            removed = previousSize - engines.size();
+        }
+        if (removed > 0) {
+            IrisLogging.debug("Dereferenced " + removed + " Data<Engine> registration(s) " + getId() + " " + getDataFolder());
+        }
+    }
+
+    public Engine getEngine() {
+        IrisContext context = IrisContext.get();
+        if (context != null) {
+            Engine contextEngine = context.getEngine();
+            if (!contextEngine.isClosed() && contextEngine.getData() == this) {
+                return contextEngine;
+            }
+        }
+
+        synchronized (engines) {
+            removeClosedEngines();
+            return engines.size() == 1 ? engines.get(0) : null;
+        }
+    }
+
+    public List<Engine> getEngines() {
+        synchronized (engines) {
+            removeClosedEngines();
+            return List.copyOf(engines);
+        }
+    }
+
+    public void registerEngine(Engine engine) {
+        Objects.requireNonNull(engine, "engine");
+        synchronized (engines) {
+            for (Engine registeredEngine : engines) {
+                if (registeredEngine == engine) {
+                    return;
+                }
+            }
+            engines.add(engine);
+        }
+    }
+
+    public void unregisterEngine(Engine engine) {
+        if (engine == null) {
+            return;
+        }
+        synchronized (engines) {
+            Iterator<Engine> iterator = engines.iterator();
+            while (iterator.hasNext()) {
+                if (iterator.next() == engine) {
+                    iterator.remove();
+                    return;
+                }
+            }
+        }
+    }
+
+    private void removeClosedEngines() {
+        Iterator<Engine> iterator = engines.iterator();
+        while (iterator.hasNext()) {
+            if (iterator.next().isClosed()) {
+                iterator.remove();
+            }
         }
     }
 
@@ -287,6 +364,9 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
     public void close() {
         closed = true;
         dump();
+        synchronized (engines) {
+            engines.clear();
+        }
         if (dataLoaders.get(dataFolder) == this) {
             dataLoaders.remove(dataFolder);
         }
@@ -365,7 +445,7 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
 
         gson = builder.create();
 
-        if (engine != null) {
+        for (Engine engine : getEngines()) {
             engine.hotload();
         }
     }
@@ -405,7 +485,7 @@ public class IrisData implements ExclusionStrategy, TypeAdapterFactory {
         invalidateLoader(structureLoader);
         invalidateLoader(jigsawPoolLoader);
         invalidateLoader(jigsawPieceLoader);
-        if (engine != null) {
+        for (Engine engine : getEngines()) {
             IrisStructureLocator.invalidate(engine);
         }
     }

core/src/main/java/art/arcane/iris/core/pregenerator/MantleHeapPressure.java

@@ -65,6 +65,16 @@ public final class MantleHeapPressure {
         return false;
     }
 
+    public static double reclaimUrgency(double fraction) {
+        if (!Double.isFinite(fraction) || fraction <= LOW_WATER) {
+            return 0D;
+        }
+        if (fraction >= HIGH_WATER) {
+            return 1D;
+        }
+        return (fraction - LOW_WATER) / (HIGH_WATER - LOW_WATER);
+    }
+
     public static boolean overPanicWater() {
         return usedFraction() >= PANIC_WATER;
     }

core/src/main/java/art/arcane/iris/core/service/EngineMaintenance.java

@@ -0,0 +1,94 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.core.IrisSettings;
+import art.arcane.iris.core.gui.PregeneratorJob;
+import art.arcane.iris.core.pregenerator.MantleHeapPressure;
+import art.arcane.iris.core.runtime.GoldenHashEngine;
+import art.arcane.iris.core.tools.WorldMaintenance;
+import art.arcane.iris.engine.framework.Engine;
+
+import java.util.Locale;
+import java.util.concurrent.TimeUnit;
+
+public final class EngineMaintenance {
+    private EngineMaintenance() {
+    }
+
+    public static boolean isAvailable(Engine engine) {
+        return engine != null
+                && !engine.isClosing()
+                && !engine.isClosed()
+                && !engine.getMantle().getMantle().isClosed();
+    }
+
+    public static boolean pregeneratorTargets(Engine engine) {
+        if (engine == null || engine.getWorld() == null) {
+            return false;
+        }
+
+        PregeneratorJob pregeneratorJob = PregeneratorJob.getInstance();
+        return pregeneratorJob != null && pregeneratorJob.targetsWorldIdentity(engine.getWorld().identity());
+    }
+
+    public static boolean shouldRun(Engine engine) {
+        if (engine.isStudio()
+                && !IrisSettings.get().getPerformance().isTrimMantleInStudio()) {
+            return false;
+        }
+        if (GoldenHashEngine.isActive()) {
+            return false;
+        }
+
+        return engine.getWorld() == null
+                || !WorldMaintenance.isWorldMaintenanceActive(engine.getWorld().identity());
+    }
+
+    public static int workerParallelism() {
+        return IrisSettings.get().getPerformance().getEngineSVC().getParallelism();
+    }
+
+    public static Outcome run(Engine engine) {
+        IrisSettings.IrisSettingsPerformance settings = IrisSettings.get().getPerformance();
+        double heapUsage = MantleHeapPressure.usedFraction();
+        Plan plan = plan(settings.getMantleKeepAlive(), heapUsage, settings.getEngineSVC().isForceMulticoreWrite());
+
+        engine.getMantle().trim(plan.idleDurationMillis());
+
+        long unloadStart = System.nanoTime();
+        int unloadedTectonicPlates = engine.getMantle().unloadTectonicPlate(
+                plan.multicoreUnload() ? 0 : Integer.MAX_VALUE);
+        if (plan.heapPressure() && MantleHeapPressure.overPanicWater()) {
+            MantleHeapPressure.requestPanicReclaim();
+        }
+
+        return new Outcome(
+                unloadedTectonicPlates,
+                TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - unloadStart));
+    }
+
+    public static boolean isMantleClosed(Throwable throwable) {
+        Throwable current = throwable;
+        while (current != null) {
+            String message = current.getMessage();
+            if (message != null && message.toLowerCase(Locale.ROOT).contains("mantle is closed")) {
+                return true;
+            }
+            current = current.getCause();
+        }
+        return false;
+    }
+
+    static Plan plan(int mantleKeepAliveSeconds, double heapUsage, boolean forceMulticoreWrite) {
+        long baseIdleDurationMillis = TimeUnit.SECONDS.toMillis(Math.max(0, mantleKeepAliveSeconds));
+        double reclaimUrgency = MantleHeapPressure.reclaimUrgency(heapUsage);
+        long idleDurationMillis = Math.round(baseIdleDurationMillis * (1D - reclaimUrgency));
+        boolean heapPressure = reclaimUrgency >= 1D;
+        return new Plan(idleDurationMillis, heapPressure || forceMulticoreWrite, heapPressure);
+    }
+
+    public record Outcome(int unloadedTectonicPlates, long unloadDurationMillis) {
+    }
+
+    record Plan(long idleDurationMillis, boolean multicoreUnload, boolean heapPressure) {
+    }
+}

core/src/main/java/art/arcane/iris/core/service/TreeSVC.java

@@ -23,6 +23,7 @@ import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.TreeBlockMaterial;
 import art.arcane.iris.engine.object.IObjectPlacer;
 import art.arcane.iris.engine.object.IrisBiome;
 import art.arcane.iris.engine.object.IrisDimension;
@@ -59,6 +60,7 @@ import org.bukkit.event.world.StructureGrowEvent;
 
 import java.util.List;
 import java.util.Objects;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.function.Predicate;
 
 public class TreeSVC implements IrisService {
@@ -138,6 +140,7 @@ public class TreeSVC implements IrisService {
 
         saplingPlane.forEach(block -> block.setType(Material.AIR));
         IrisObject object = worldAccess.getData().getObjectLoader().load(placement.getPlace().getRandom(RNG.r));
+        String treeMarker = object.getLoadKey() + "@" + ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);
         List<BlockState> blockStateList = new KList<>();
         KMap<Location, BlockData> dataCache = new KMap<>();
         // TODO: REAL CLASSES!!!!
@@ -234,7 +237,7 @@ public class TreeSVC implements IrisService {
 
         event.setCancelled(true);
 
-        J.s(() -> {
+        Runnable growTask = () -> {
 
             StructureGrowEvent iGrow = new StructureGrowEvent(event.getLocation(), event.getSpecies(), event.isFromBonemeal(), event.getPlayer(), blockStateList);
             block = true;
@@ -253,9 +256,20 @@ public class TreeSVC implements IrisService {
                         block.setBlockData(data.getBase(), false);
                         IrisServices.get(ExternalDataSVC.class).processUpdate(engine, block, data.getCustom());
                     } else block.setBlockData(d, false);
+                    int mantleY = block.getY() - event.getWorld().getMinHeight();
+                    engine.getMantle().getMantle().set(block.getX(), mantleY, block.getZ(), treeMarker);
+                    engine.getMantle().getMantle().set(
+                            block.getX(),
+                            mantleY,
+                            block.getZ(),
+                            TreeBlockMaterial.of(block.getBlockData().getAsString())
+                    );
                 }
             }
-        });
+        };
+        if (!J.runAt(event.getLocation(), growTask) && !J.isFolia()) {
+            J.s(growTask);
+        }
     }
 
     /**

core/src/main/java/art/arcane/iris/core/service/tree/BlockDropRouter.java

@@ -0,0 +1,6 @@
+package art.arcane.iris.core.service.tree;
+
+@FunctionalInterface
+public interface BlockDropRouter {
+    boolean routeDrop(Object drop);
+}

core/src/main/java/art/arcane/iris/core/service/tree/TreeDefinitionIndex.java

@@ -0,0 +1,97 @@
+package art.arcane.iris.core.service.tree;
+
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.StructurePlacementMarker;
+import art.arcane.iris.engine.object.IrisBiome;
+import art.arcane.iris.engine.object.IrisObjectPlacement;
+import art.arcane.iris.engine.object.IrisProceduralObjects;
+import art.arcane.iris.engine.object.IrisProceduralTree;
+import art.arcane.iris.engine.object.IrisRegion;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public final class TreeDefinitionIndex {
+    private static final String PROCEDURAL_TREE_PREFIX = "procedural/tree/";
+
+    private final Set<String> explicitObjectKeys;
+    private final Set<String> proceduralTreeKeys;
+
+    private TreeDefinitionIndex(Set<String> explicitObjectKeys, Set<String> proceduralTreeKeys) {
+        this.explicitObjectKeys = Set.copyOf(explicitObjectKeys);
+        this.proceduralTreeKeys = Set.copyOf(proceduralTreeKeys);
+    }
+
+    public static TreeDefinitionIndex build(Engine engine) {
+        Set<String> explicitObjectKeys = new HashSet<>();
+        Set<String> proceduralTreeKeys = new HashSet<>();
+
+        for (IrisRegion region : engine.getDimension().getAllRegions(engine)) {
+            if (region == null) {
+                continue;
+            }
+            collectPlacements(region.getObjects(), explicitObjectKeys);
+            collectProceduralTrees(region.getProceduralObjects(), proceduralTreeKeys);
+        }
+
+        for (IrisBiome biome : engine.getDimension().getReachableBiomes(engine)) {
+            if (biome == null) {
+                continue;
+            }
+            collectPlacements(biome.getObjects(), explicitObjectKeys);
+            collectProceduralTrees(biome.getProceduralObjects(), proceduralTreeKeys);
+        }
+
+        return new TreeDefinitionIndex(explicitObjectKeys, proceduralTreeKeys);
+    }
+
+    public boolean isTreeMarker(String marker) {
+        StructurePlacementMarker.Decoded decoded = StructurePlacementMarker.decode(marker);
+        if (decoded == null || decoded.structureAware()) {
+            return false;
+        }
+
+        String objectKey = decoded.objectKey();
+        if (objectKey.startsWith(PROCEDURAL_TREE_PREFIX)) {
+            return proceduralTreeKeys.contains(objectKey);
+        }
+        if (objectKey.startsWith("procedural/")) {
+            return false;
+        }
+        return objectKey.startsWith("trees/") || explicitObjectKeys.contains(objectKey);
+    }
+
+    private static void collectPlacements(Iterable<IrisObjectPlacement> placements, Set<String> objectKeys) {
+        if (placements == null) {
+            return;
+        }
+        for (IrisObjectPlacement placement : placements) {
+            if (placement == null
+                    || placement.getTrees() == null
+                    || placement.getTrees().isEmpty()
+                    || placement.getPlace() == null) {
+                continue;
+            }
+            for (String objectKey : placement.getPlace()) {
+                if (objectKey != null && !objectKey.isBlank()) {
+                    objectKeys.add(objectKey);
+                }
+            }
+        }
+    }
+
+    private static void collectProceduralTrees(IrisProceduralObjects proceduralObjects, Set<String> objectKeys) {
+        if (proceduralObjects == null || proceduralObjects.getTrees() == null) {
+            return;
+        }
+        for (IrisProceduralTree tree : proceduralObjects.getTrees()) {
+            if (tree == null || tree.getName() == null || tree.getName().isBlank()) {
+                continue;
+            }
+            int variants = Math.max(1, tree.getVariants());
+            for (int index = 0; index < variants; index++) {
+                objectKeys.add(tree.getVariantLoadKey(index));
+            }
+        }
+    }
+}

core/src/main/java/art/arcane/iris/core/service/tree/TreeMarkerTraversal.java

@@ -0,0 +1,84 @@
+package art.arcane.iris.core.service.tree;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public final class TreeMarkerTraversal {
+    public static final int MAX_MEMBERS = 131_072;
+    public static final int MAX_VISITED = 1_000_000;
+    public static final int MAX_AXIS_DISTANCE = 256;
+
+    private TreeMarkerTraversal() {
+    }
+
+    public static Discovery discover(Position trigger, String marker, int minimumY, int maximumY, MarkerLookup lookup) {
+        ArrayDeque<Position> pending = new ArrayDeque<>();
+        Set<Position> visited = new HashSet<>();
+        List<Position> members = new ArrayList<>();
+        pending.add(trigger);
+        visited.add(trigger);
+
+        while (!pending.isEmpty()) {
+            Position current = pending.removeFirst();
+            if (!marker.equals(lookup.markerAt(current.x(), current.y(), current.z()))) {
+                continue;
+            }
+            if (members.size() >= MAX_MEMBERS) {
+                return new Discovery(List.copyOf(members), false);
+            }
+            members.add(current);
+
+            for (int xOffset = -1; xOffset <= 1; xOffset++) {
+                for (int yOffset = -1; yOffset <= 1; yOffset++) {
+                    for (int zOffset = -1; zOffset <= 1; zOffset++) {
+                        if (xOffset == 0 && yOffset == 0 && zOffset == 0) {
+                            continue;
+                        }
+                        Position next = current.offset(xOffset, yOffset, zOffset);
+                        if (next.y() < minimumY || next.y() >= maximumY) {
+                            continue;
+                        }
+                        if (!withinAxisBounds(trigger, next)) {
+                            if (marker.equals(lookup.markerAt(next.x(), next.y(), next.z()))) {
+                                return new Discovery(List.copyOf(members), false);
+                            }
+                            continue;
+                        }
+                        if (!visited.add(next)) {
+                            continue;
+                        }
+                        if (visited.size() > MAX_VISITED) {
+                            return new Discovery(List.copyOf(members), false);
+                        }
+                        pending.addLast(next);
+                    }
+                }
+            }
+        }
+
+        return new Discovery(List.copyOf(members), true);
+    }
+
+    private static boolean withinAxisBounds(Position trigger, Position position) {
+        return Math.abs(position.x() - trigger.x()) <= MAX_AXIS_DISTANCE
+                && Math.abs(position.y() - trigger.y()) <= MAX_AXIS_DISTANCE
+                && Math.abs(position.z() - trigger.z()) <= MAX_AXIS_DISTANCE;
+    }
+
+    @FunctionalInterface
+    public interface MarkerLookup {
+        String markerAt(int x, int y, int z);
+    }
+
+    public record Position(int x, int y, int z) {
+        public Position offset(int xOffset, int yOffset, int zOffset) {
+            return new Position(x + xOffset, y + yOffset, z + zOffset);
+        }
+    }
+
+    public record Discovery(List<Position> members, boolean complete) {
+    }
+}

core/src/main/java/art/arcane/iris/engine/EnginePanic.java

@@ -19,30 +19,87 @@
 package art.arcane.iris.engine;
 
 import art.arcane.iris.spi.IrisLogging;
-import art.arcane.volmlib.util.collection.KMap;
 
-public class EnginePanic {
-    private static final KMap<String, String> stuff = new KMap<>();
-    private static KMap<String, String> last = new KMap<>();
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
+
+public final class EnginePanic {
+    private static final Diagnostics GLOBAL = scoped("global");
+
+    private EnginePanic() {
+    }
+
+    public static Diagnostics scoped(String scope) {
+        return new Diagnostics(scope);
+    }
 
     public static void add(String key, String value) {
-        stuff.put(key, value);
+        GLOBAL.add(key, value);
     }
 
     public static void saveLast() {
-        last = stuff.copy();
+        GLOBAL.saveLast();
     }
 
     public static void lastPanic() {
-        for (String i : last.keySet()) {
-            IrisLogging.error("Last Panic " + i + ": " + stuff.get(i));
-        }
+        GLOBAL.lastPanic();
     }
 
     public static void panic() {
-        lastPanic();
-        for (String i : stuff.keySet()) {
-            IrisLogging.error("Engine Panic " + i + ": " + stuff.get(i));
+        GLOBAL.panic();
+    }
+
+    public static final class Diagnostics {
+        private final String scope;
+        private final ThreadLocal<LinkedHashMap<String, String>> current = ThreadLocal.withInitial(LinkedHashMap::new);
+        private final AtomicReference<Map<String, String>> last = new AtomicReference<>(Map.of());
+
+        private Diagnostics(String scope) {
+            this.scope = scope == null || scope.isBlank() ? "unknown" : scope;
+        }
+
+        public void add(String key, String value) {
+            current.get().put(String.valueOf(key), String.valueOf(value));
+        }
+
+        public void saveLast() {
+            last.set(currentSnapshot());
+            current.remove();
+        }
+
+        public void lastPanic() {
+            log("Last Panic", last.get());
+        }
+
+        public void panic() {
+            Map<String, String> currentSnapshot = currentSnapshot();
+            lastPanic();
+            log("Engine Panic", currentSnapshot);
+            current.remove();
+        }
+
+        Map<String, String> currentSnapshot() {
+            return immutableSnapshot(current.get());
+        }
+
+        Map<String, String> lastSnapshot() {
+            return last.get();
+        }
+
+        private void log(String prefix, Map<String, String> snapshot) {
+            for (Map.Entry<String, String> entry : snapshot.entrySet()) {
+                IrisLogging.error(prefix + " [" + scope + "] " + entry.getKey() + ": " + entry.getValue());
+            }
+        }
+
+        private static Map<String, String> immutableSnapshot(Map<String, String> values) {
+            if (values.isEmpty()) {
+                return Map.of();
+            }
+
+            return Collections.unmodifiableMap(new LinkedHashMap<>(values));
         }
     }
 }

core/src/main/java/art/arcane/iris/engine/GenerationCacheWarmer.java

@@ -48,7 +48,7 @@ public final class GenerationCacheWarmer {
             KList<IrisBiome> biomes = engine.getAllBiomes();
             biomes.sort(Comparator.comparing(IrisBiome::getLoadKey));
             for (IrisBiome biome : biomes) {
-                warmPlacements(biome.getObjects(), root, counter, data);
+                warmPlacements(biome.getObjects(), root, counter, data, engine);
                 warmDecorators(biome.getDecorators(), root, counter, data);
                 warmOres(biome.getOres(), root, counter, data);
                 warmProcedural(biome.getProceduralObjects(), root, counter, data);
@@ -57,7 +57,7 @@ public final class GenerationCacheWarmer {
             KList<IrisRegion> regions = engine.getDimension().getAllRegions(engine);
             regions.sort(Comparator.comparing(IrisRegion::getLoadKey));
             for (IrisRegion region : regions) {
-                warmPlacements(region.getObjects(), root, counter, data);
+                warmPlacements(region.getObjects(), root, counter, data, engine);
                 warmOres(region.getOres(), root, counter, data);
                 warmProcedural(region.getProceduralObjects(), root, counter, data);
             }
@@ -71,7 +71,8 @@ public final class GenerationCacheWarmer {
         IrisLogging.debug("[IrisEngine timing] cache warm " + counter[0] + " configs=" + (M.ms() - start) + "ms");
     }
 
-    private static void warmPlacements(KList<IrisObjectPlacement> placements, RNG root, int[] counter, IrisData data) {
+    private static void warmPlacements(KList<IrisObjectPlacement> placements, RNG root, int[] counter,
+                                       IrisData data, Engine engine) {
         if (placements == null) {
             return;
         }
@@ -80,7 +81,7 @@ public final class GenerationCacheWarmer {
                 continue;
             }
             RNG rng = root.nextParallelRNG(counter[0]++);
-            placement.getSurfaceWarp(rng, data);
+            placement.getSurfaceWarp(rng, data, engine);
             placement.getDensity(rng, 0, 0, data);
         }
     }

core/src/main/java/art/arcane/iris/engine/IrisComplex.java

@@ -111,7 +111,7 @@ public class IrisComplex implements DataProvider {
 
     public IrisComplex(Engine engine, boolean simple) {
         int cacheSize = IrisSettings.get().getPerformance().getNoiseCacheSize();
-        IrisBiome emptyBiome = new IrisBiome();
+        IrisBiome emptyBiome = new IrisBiome().setInferredType(InferredType.CAVE);
         UUID focusUUID = UUID.nameUUIDFromBytes("focus".getBytes());
         this.rng = new RNG(engine.getSeedManager().getComplex());
         this.data = engine.getData();
@@ -124,19 +124,23 @@ public class IrisComplex implements DataProvider {
         Map<InferredType, ProceduralStream<IrisBiome>> inferredStreams = new HashMap<>();
 
         if (focusBiome != null) {
-            focusBiome.setInferredType(InferredType.LAND);
+            focusBiome = focusBiome.withInferredType(InferredType.LAND);
             focusRegion = findRegion(focusBiome, engine);
         }
 
         //@builder
         if (focusRegion != null) {
+            prepareInferredBiomes(focusRegion);
             focusRegion.getAllBiomes(this).forEach(this::registerGenerators);
         } else {
-            engine.getDimension()
-                    .getRegions()
-                    .forEach(i -> data.getRegionLoader().load(i)
-                            .getAllBiomes(this)
-                            .forEach(this::registerGenerators));
+            engine.getDimension().getRegions().forEach(regionKey -> {
+                IrisRegion region = data.getRegionLoader().load(regionKey);
+                if (region == null) {
+                    return;
+                }
+                prepareInferredBiomes(region);
+                region.getAllBiomes(this).forEach(this::registerGenerators);
+            });
         }
         generatorBounds = buildGeneratorBounds(engine);
         KList<IrisShapedGeneratorStyle> overlayNoise = engine.getDimension().getOverlayNoise();
@@ -171,7 +175,7 @@ public class IrisComplex implements DataProvider {
                         -> engine.getDimension().getCaveBiomeStyle().create(rng.nextParallelRNG(InferredType.CAVE.ordinal()), getData()).stream()
                         .zoom(engine.getDimension().getBiomeZoom())
                         .zoom(r.getCaveBiomeZoom())
-                        .selectRarity(data.getBiomeLoader().loadAll(r.getCaveBiomes()))
+                        .selectRarity(loadInferredBiomes(r.getCaveBiomes(), InferredType.CAVE))
                         .onNull(emptyBiome)
                 ).convertAware2D(ProceduralStream::get).cache2D("caveBiomeStream", engine, cacheSize).waste("Cave Biome Stream");
         inferredStreams.put(InferredType.CAVE, caveBiomeStream);
@@ -181,7 +185,7 @@ public class IrisComplex implements DataProvider {
                         .zoom(engine.getDimension().getBiomeZoom())
                         .zoom(engine.getDimension().getLandZoom())
                         .zoom(r.getLandBiomeZoom())
-                        .selectRarity(data.getBiomeLoader().loadAll(r.getLandBiomes(), (t) -> t.setInferredType(InferredType.LAND)))
+                        .selectRarity(loadInferredBiomes(r.getLandBiomes(), InferredType.LAND))
                 ).convertAware2D(ProceduralStream::get)
                 .cache2D("landBiomeStream", engine, cacheSize).waste("Land Biome Stream");
         inferredStreams.put(InferredType.LAND, landBiomeStream);
@@ -191,7 +195,7 @@ public class IrisComplex implements DataProvider {
                         .zoom(engine.getDimension().getBiomeZoom())
                         .zoom(engine.getDimension().getSeaZoom())
                         .zoom(r.getSeaBiomeZoom())
-                        .selectRarity(data.getBiomeLoader().loadAll(r.getSeaBiomes(), (t) -> t.setInferredType(InferredType.SEA)))
+                        .selectRarity(loadInferredBiomes(r.getSeaBiomes(), InferredType.SEA))
                 ).convertAware2D(ProceduralStream::get)
                 .cache2D("seaBiomeStream", engine, cacheSize).waste("Sea Biome Stream");
         inferredStreams.put(InferredType.SEA, seaBiomeStream);
@@ -200,7 +204,7 @@ public class IrisComplex implements DataProvider {
                         -> engine.getDimension().getShoreBiomeStyle().create(rng.nextParallelRNG(InferredType.SHORE.ordinal()), getData()).stream()
                         .zoom(engine.getDimension().getBiomeZoom())
                         .zoom(r.getShoreBiomeZoom())
-                        .selectRarity(data.getBiomeLoader().loadAll(r.getShoreBiomes(), (t) -> t.setInferredType(InferredType.SHORE)))
+                        .selectRarity(loadInferredBiomes(r.getShoreBiomes(), InferredType.SHORE))
                 ).convertAware2D(ProceduralStream::get).cache2D("shoreBiomeStream", engine, cacheSize).waste("Shore Biome Stream");
         inferredStreams.put(InferredType.SHORE, shoreBiomeStream);
         bridgeStream = focusBiome != null ? ProceduralStream.of((x, z) -> focusBiome.getInferredType(),
@@ -312,22 +316,49 @@ public class IrisComplex implements DataProvider {
     }
 
     private IrisBiome fixBiomeType(Double height, IrisBiome biome, IrisRegion region, Double x, Double z, double fluidHeight) {
+        IrisBiome resolved = resolveSurfaceBiome(
+                height,
+                biome,
+                region,
+                x,
+                z,
+                fluidHeight,
+                landBiomeStream,
+                seaBiomeStream,
+                shoreBiomeStream);
+        return resolved == biome ? biome : implode(resolved, x, z);
+    }
+
+    static IrisBiome resolveSurfaceBiome(
+            double height,
+            IrisBiome biome,
+            IrisRegion region,
+            double x,
+            double z,
+            double fluidHeight,
+            ProceduralStream<IrisBiome> landBiomes,
+            ProceduralStream<IrisBiome> seaBiomes,
+            ProceduralStream<IrisBiome> shoreBiomes
+    ) {
+        if (biome == null || region == null) {
+            return biome;
+        }
         double sh = region.getShoreHeight(x, z);
 
         if (height >= fluidHeight - 1 && height <= fluidHeight + sh && !biome.isShore()) {
-            return shoreBiomeStream.get(x, z);
+            return shoreBiomes.get(x, z);
         }
 
         if (height > fluidHeight + sh && !biome.isLand()) {
-            return landBiomeStream.get(x, z);
+            return landBiomes.get(x, z);
         }
 
         if (height < fluidHeight && !biome.isAquatic()) {
-            return seaBiomeStream.get(x, z);
+            return seaBiomes.get(x, z);
         }
 
         if (height == fluidHeight && !biome.isShore()) {
-            return shoreBiomeStream.get(x, z);
+            return shoreBiomes.get(x, z);
         }
 
         return biome;
@@ -446,6 +477,21 @@ public class IrisComplex implements DataProvider {
         return Math.max(Math.min(getInterpolatedHeight(engine, x, z, seed) + fluidHeight + overlayStream.get(x, z), engine.getHeight()), 0);
     }
 
+    private void prepareInferredBiomes(IrisRegion region) {
+        loadInferredBiomes(region.getLandBiomes(), InferredType.LAND);
+        loadInferredBiomes(region.getCaveBiomes(), InferredType.CAVE);
+        loadInferredBiomes(region.getSeaBiomes(), InferredType.SEA);
+        loadInferredBiomes(region.getShoreBiomes(), InferredType.SHORE);
+    }
+
+    private KList<IrisBiome> loadInferredBiomes(KList<String> keys, InferredType type) {
+        KList<IrisBiome> inferred = new KList<>();
+        for (IrisBiome biome : data.getBiomeLoader().loadAll(keys)) {
+            inferred.add(biome.withInferredType(type));
+        }
+        return inferred;
+    }
+
     private void registerGenerators(IrisBiome biome) {
         generatorBiomes.add(biome);
         biome.getGenerators().forEach(c -> registerGenerator(c.getCachedGenerator(this)));
@@ -532,8 +578,7 @@ public class IrisComplex implements DataProvider {
 
         CNG childCell = b.getChildrenGenerator(rng, 123, b.getChildShrinkFactor());
         ChildSelectionPlan childSelectionPlan = resolveChildSelectionPlan(b);
-        IrisBiome biome = childSelectionPlan.select(childCell, x, z);
-        biome.setInferredType(b.getInferredType());
+        IrisBiome biome = childSelectionPlan.select(childCell, x, z).withInferredType(b.getInferredType());
         return implode(biome, x, z, max - 1);
     }
 
@@ -640,7 +685,7 @@ public class IrisComplex implements DataProvider {
         }
     }
 
-    private static class ChildSelectionPlan {
+    static final class ChildSelectionPlan {
         private final IrisBiome[] mappedBiomes;
         private final int maxIndex;
 
@@ -649,7 +694,7 @@ public class IrisComplex implements DataProvider {
             this.maxIndex = mappedBiomes.length - 1;
         }
 
-        private static ChildSelectionPlan create(KList<IrisBiome> options) {
+        static ChildSelectionPlan create(KList<IrisBiome> options) {
             if (options.isEmpty()) {
                 return new ChildSelectionPlan(new IrisBiome[0]);
             }
@@ -690,7 +735,7 @@ public class IrisComplex implements DataProvider {
             return new ChildSelectionPlan(mappedBiomes);
         }
 
-        private IrisBiome select(CNG childCell, double x, double z) {
+        IrisBiome select(CNG childCell, double x, double z) {
             if (mappedBiomes.length == 0) {
                 return null;
             }

core/src/main/java/art/arcane/iris/engine/IrisEngineEffects.java

@@ -36,19 +36,23 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 
 public class IrisEngineEffects extends EngineAssignedComponent implements EngineEffects {
     private static final long EFFECT_BUDGET_NANOS = 1_500_000L;
+    private static final long EMPTY_PLAYER_REFRESH_NANOS = 1_000_000_000L;
 
     private final ConcurrentHashMap<UUID, EnginePlayer> players;
     private final Semaphore limit;
     private final AtomicBoolean playerMapUpdateQueued;
+    private final AtomicLong nextEmptyRefresh;
 
     public IrisEngineEffects(Engine engine) {
         super(engine, "FX");
         players = new ConcurrentHashMap<>();
         limit = new Semaphore(1);
         playerMapUpdateQueued = new AtomicBoolean(false);
+        nextEmptyRefresh = new AtomicLong(0L);
     }
 
     @Override
@@ -93,7 +97,15 @@ public class IrisEngineEffects extends EngineAssignedComponent implements Engine
             return;
         }
         try {
-            if (players.isEmpty() || M.r(0.02)) {
+            if (players.isEmpty()) {
+                long now = System.nanoTime();
+                long next = nextEmptyRefresh.get();
+                if (now >= next && nextEmptyRefresh.compareAndSet(next, now + EMPTY_PLAYER_REFRESH_NANOS)) {
+                    updatePlayerMap();
+                }
+                return;
+            }
+            if (M.r(0.02)) {
                 updatePlayerMap();
                 return;
             }

core/src/main/java/art/arcane/iris/engine/IrisEngineMantle.java

@@ -22,7 +22,6 @@ import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.core.IrisSettings;
 import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.tools.WorldMaintenance;
-import art.arcane.iris.engine.EnginePanic;
 import art.arcane.iris.core.nms.container.Pair;
 import art.arcane.iris.engine.data.cache.AtomicCache;
 import art.arcane.iris.engine.framework.Engine;
@@ -66,7 +65,9 @@ import java.io.IOException;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
+import java.util.function.Supplier;
 
 @Data
 @EqualsAndHashCode(exclude = "engine")
@@ -182,8 +183,8 @@ public class IrisEngineMantle implements EngineMantle {
         IrisMatterSupport.ensureRegistered();
         File dataFolder = new File(engine.getWorld().worldFolder(), "mantle");
         int worldHeight = engine.getTarget().getHeight();
-        MantleDataAdapter<Matter> adapter = createRuntimeDataAdapter(engine.getData());
-        MantleHooks hooks = createRuntimeHooks();
+        MantleDataAdapter<Matter> adapter = createDataAdapter(engine::getData);
+        MantleHooks hooks = createHooks(EnginePanic.scoped("world " + engine.getWorld().name()));
         art.arcane.volmlib.util.mantle.Mantle.RegionIO<TectonicPlate<Matter>> regionIO =
                 createRegionIO(dataFolder, worldHeight, adapter, hooks);
         return new Mantle<>(
@@ -199,14 +200,14 @@ public class IrisEngineMantle implements EngineMantle {
     }
 
     public static MantleDataAdapter<Matter> createRuntimeDataAdapter(IrisData data) {
-        return createDataAdapter(data);
+        return createDataAdapter(() -> data);
     }
 
     public static MantleHooks createRuntimeHooks() {
-        return createHooks();
+        return createHooks(EnginePanic.scoped("runtime mantle"));
     }
 
-    private static MantleDataAdapter<Matter> createDataAdapter(IrisData data) {
+    private static MantleDataAdapter<Matter> createDataAdapter(Supplier<IrisData> dataSupplier) {
         return new MantleDataAdapter<>() {
             @Override
             public Matter createSection() {
@@ -215,6 +216,7 @@ public class IrisEngineMantle implements EngineMantle {
 
             @Override
             public Matter readSection(art.arcane.volmlib.util.io.CountingDataInputStream din) throws IOException {
+                IrisData data = Objects.requireNonNull(dataSupplier.get(), "Iris mantle data is unavailable.");
                 try (IrisMatterContext.Scope scope = IrisMatterContext.open(data)) {
                     return Matter.readDin(din);
                 }
@@ -285,11 +287,11 @@ public class IrisEngineMantle implements EngineMantle {
         };
     }
 
-    private static MantleHooks createHooks() {
+    private static MantleHooks createHooks(EnginePanic.Diagnostics panic) {
         return new MantleHooks() {
             @Override
             public void onBeforeReadSection(int index) {
-                EnginePanic.add("read.section", "Section[" + index + "]");
+                panic.add("read.section", "Section[" + index + "]");
             }
 
             @Override
@@ -299,22 +301,22 @@ public class IrisEngineMantle implements EngineMantle {
                                              art.arcane.volmlib.util.io.CountingDataInputStream din,
                                              IOException error) {
                 IrisLogging.error("Failed to read chunk section, skipping it.");
-                EnginePanic.add("read.byte.range", start + " " + end);
-                EnginePanic.add("read.byte.current", din.count() + "");
+                panic.add("read.byte.range", start + " " + end);
+                panic.add("read.byte.current", din.count() + "");
                 IrisLogging.reportError(error);
                 error.printStackTrace();
-                EnginePanic.panic();
+                panic.panic();
                 TectonicPlate.addError();
             }
 
             @Override
             public void onBeforeReadChunk(int index) {
-                EnginePanic.add("read-chunk", "Chunk[" + index + "]");
+                panic.add("read-chunk", "Chunk[" + index + "]");
             }
 
             @Override
             public void onAfterReadChunk(int index) {
-                EnginePanic.saveLast();
+                panic.saveLast();
             }
 
             @Override
@@ -324,11 +326,11 @@ public class IrisEngineMantle implements EngineMantle {
                                            art.arcane.volmlib.util.io.CountingDataInputStream din,
                                            Throwable error) {
                 IrisLogging.error("Failed to read chunk, creating a new chunk instead.");
-                EnginePanic.add("read.byte.range", start + " " + end);
-                EnginePanic.add("read.byte.current", din.count() + "");
+                panic.add("read.byte.range", start + " " + end);
+                panic.add("read.byte.current", din.count() + "");
                 IrisLogging.reportError(error);
                 error.printStackTrace();
-                EnginePanic.panic();
+                panic.panic();
             }
 
             @Override

core/src/main/java/art/arcane/iris/engine/IrisWorldManager.java

@@ -22,6 +22,7 @@ import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
 import art.arcane.iris.core.IrisSettings;
 import art.arcane.iris.core.gui.PregeneratorJob;
 import art.arcane.iris.core.loader.IrisData;
+import art.arcane.iris.core.service.tree.BlockDropRouter;
 import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.engine.data.cache.Cache;
 import art.arcane.iris.engine.framework.Engine;
@@ -82,9 +83,12 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.BiConsumer;
+import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -95,7 +99,6 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
     private static final int MAX_FORCED_CHUNK_UPDATES = 128;
 
     private final Looper looper;
-    private final int id;
     private final KList<Runnable> updateQueue = new KList<>();
     private final ChronoLatch cl;
     private final ChronoLatch clw;
@@ -111,10 +114,15 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
     private final Set<Long> chunkUpdateQueue = ConcurrentHashMap.newKeySet();
     private final AtomicBoolean chunkUpdateScanScheduled = new AtomicBoolean();
     private final AtomicBoolean chunkDiscoveryScanScheduled = new AtomicBoolean();
-    private int entityCount = 0;
-    private int actuallySpawned = 0;
+    private final AtomicBoolean entityCountWarningReported = new AtomicBoolean();
+    private final AtomicBoolean entityCountErrorReported = new AtomicBoolean();
+    private boolean looperStopped;
+    private boolean cleanupServiceStopped;
+    private volatile int entityCount = 0;
+    private final AtomicInteger actuallySpawned = new AtomicInteger();
     private int cooldown = 0;
     private int forcedChunkUpdateCursor = 0;
+    private volatile boolean entityCountValid = false;
     private volatile boolean playersPresent = false;
     private KSet<Position2> injectBiomes = new KSet<>();
     private volatile int loadedChunkCount = 0;
@@ -128,7 +136,6 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
         chunkUpdater = null;
         chunkDiscovery = null;
         cleanupService = null;
-        id = -1;
     }
 
     public IrisWorldManager(Engine engine) {
@@ -143,55 +150,82 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             thread.setPriority(Thread.MIN_PRIORITY);
             return thread;
         });
-        id = engine.getCacheID();
         looper = new Looper() {
             @Override
             protected long loop() {
-                if (getEngine().isClosed() || getEngine().getCacheID() != id) {
-                    interrupt();
+                if (!isManagerStarted()) {
+                    return -1L;
                 }
-
-                if (!getEngine().getWorld().hasPlatformWorld() && clw.flip()) {
-                    J.runGlobal(() -> BukkitWorldBinding.tryBind(getEngine().getWorld()));
-                }
-
-                if (getEngine().getWorld().hasPlatformWorld()) {
-                    if (chunkUpdater.flip()) {
-                        updateChunks();
-                    }
-
-                    if (!playersPresent) {
-                        return 5000;
-                    }
-
-                    if (chunkDiscovery.flip()) {
-                        discoverChunks();
-                    }
-
-                    if (cln.flip()) {
-                        engine.getEngineData().cleanup(getEngine());
-                    }
-
-                    if (!IrisSettings.get().getWorld().isMarkerEntitySpawningSystem() && !IrisSettings.get().getWorld().isAmbientEntitySpawningSystem()) {
-                        return 3000;
-                    }
-
-                    onAsyncTick();
-                }
-
-                return IrisSettings.get().getWorld().getAsyncTickIntervalMS();
+                return callManagerTask(
+                        "bukkit_world_manager_loop",
+                        IrisWorldManager.this::runLoop,
+                        250L);
             }
         };
         looper.setPriority(Thread.MIN_PRIORITY);
         looper.setName("Iris World Manager " + getTarget().getWorld().name());
     }
 
-    public void startManager() {
+    private long runLoop() {
+        if (getEngine().isClosed()) {
+            looper.interrupt();
+            return -1L;
+        }
+
+        if (!getEngine().getWorld().hasPlatformWorld() && clw.flip()) {
+            J.runGlobal(() -> runManagerTask(
+                    "bukkit_world_manager_bind",
+                    () -> BukkitWorldBinding.tryBind(getEngine().getWorld())));
+        }
+
+        if (getEngine().getWorld().hasPlatformWorld()) {
+            if (chunkUpdater.flip()) {
+                updateChunks();
+            }
+
+            if (!playersPresent) {
+                return 5000L;
+            }
+
+            if (chunkDiscovery.flip()) {
+                discoverChunks();
+            }
+
+            if (cln.flip()) {
+                getEngine().getEngineData().cleanup(getEngine());
+            }
+
+            if (!IrisSettings.get().getWorld().isMarkerEntitySpawningSystem()
+                    && !IrisSettings.get().getWorld().isAmbientEntitySpawningSystem()) {
+                return 3000L;
+            }
+
+            onAsyncTick();
+        }
+
+        return IrisSettings.get().getWorld().getAsyncTickIntervalMS();
+    }
+
+    @Override
+    public void start() {
+        super.start();
         if (!looper.isAlive()) {
             looper.start();
         }
     }
 
+    private Runnable managedTask(String operation, Runnable task) {
+        return () -> runManagerTask(operation, task);
+    }
+
+    private Runnable managedTask(String operation, Runnable task, Runnable unavailable) {
+        return () -> {
+            if (!runManagerTask(operation, task)) {
+                unavailable.run();
+            }
+        };
+    }
+
     private void discoverChunks() {
         World world = BukkitWorldBinding.world(getEngine().getWorld());
         if (world == null) {
@@ -206,7 +240,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        boolean scheduled = J.runGlobal(() -> {
+        boolean scheduled = J.runGlobal(managedTask("bukkit_world_manager_discover_chunks", () -> {
             try {
                 if (getEngine().isClosed() || !world.equals(BukkitWorldBinding.world(getEngine().getWorld()))) {
                     return;
@@ -217,7 +251,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                         continue;
                     }
 
-                    J.runEntity(player, () -> {
+                    J.runEntity(player, managedTask("bukkit_world_manager_discover_player", () -> {
                         if (!player.isOnline() || !world.equals(player.getWorld())) {
                             return;
                         }
@@ -232,14 +266,14 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                                 raiseDiscoveredChunkFlag(world, chunkX, chunkZ);
                             }
                         }
-                    });
+                    }));
                 }
             } catch (Throwable e) {
                 IrisLogging.reportError(e);
             } finally {
                 chunkDiscoveryScanScheduled.set(false);
             }
-        });
+        }, () -> chunkDiscoveryScanScheduled.set(false)));
         if (!scheduled) {
             chunkDiscoveryScanScheduled.set(false);
         }
@@ -260,7 +294,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_discovered_flag", () -> {
             try {
                 Mantle<Matter> mantle = getMantle();
                 if (!mantle.hasFlag(chunkX, chunkZ, MantleFlag.DISCOVERED)) {
@@ -271,7 +305,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             } finally {
                 discoveredFlagQueue.remove(key);
             }
-        });
+        }, () -> discoveredFlagQueue.remove(key)));
     }
 
     private void updateChunks() {
@@ -288,7 +322,10 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        boolean scheduled = J.runGlobal(() -> updateChunksOnGlobal(world));
+        boolean scheduled = J.runGlobal(managedTask(
+                "bukkit_world_manager_update_chunks",
+                () -> updateChunksOnGlobal(world),
+                () -> chunkUpdateScanScheduled.set(false)));
         if (!scheduled) {
             chunkUpdateScanScheduled.set(false);
         }
@@ -308,7 +345,9 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                     continue;
                 }
 
-                J.runEntity(player, () -> schedulePlayerChunkUpdates(world, player));
+                J.runEntity(player, managedTask(
+                        "bukkit_world_manager_player_chunk_updates",
+                        () -> schedulePlayerChunkUpdates(world, player)));
             }
 
             scheduleForcedChunkUpdates(world);
@@ -363,13 +402,13 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
         }
 
         try {
-            boolean scheduled = J.runRegion(world, chunkX, chunkZ, () -> {
+            boolean scheduled = J.runRegion(world, chunkX, chunkZ, managedTask("bukkit_world_manager_chunk_update", () -> {
                 try {
                     updateChunkRegion(world, chunkX, chunkZ);
                 } finally {
                     chunkUpdateQueue.remove(key);
                 }
-            });
+            }, () -> chunkUpdateQueue.remove(key)));
             if (!scheduled) {
                 chunkUpdateQueue.remove(key);
             }
@@ -409,12 +448,12 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
 
         raiseInitialSpawnMarkerFlag(world, chunkX, chunkZ, () -> {
             int delay = RNG.r.i(5, 200);
-            J.runRegion(world, chunkX, chunkZ, () -> {
+            J.runRegion(world, chunkX, chunkZ, managedTask("bukkit_world_manager_initial_spawn_followup", () -> {
                 if (!world.isChunkLoaded(chunkX, chunkZ)) {
                     return;
                 }
                 spawnIn(world.getChunkAt(chunkX, chunkZ), true);
-            }, delay);
+            }), delay);
 
             Chunk markerChunk = world.getChunkAt(chunkX, chunkZ);
             forEachMarkerSpawner(markerChunk, (block, spawners) -> {
@@ -442,7 +481,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_spawn_marker_flag", () -> {
             boolean raised = false;
             try {
                 Mantle<Matter> mantle = getMantle();
@@ -460,13 +499,13 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                 return;
             }
 
-            J.runRegion(world, chunkX, chunkZ, () -> {
+            J.runRegion(world, chunkX, chunkZ, managedTask("bukkit_world_manager_spawn_marker_callback", () -> {
                 if (!world.isChunkLoaded(chunkX, chunkZ) || !Chunks.isSafe(world, chunkX, chunkZ)) {
                     return;
                 }
                 onFirstRaise.run();
-            });
-        });
+            }));
+        }, () -> markerFlagQueue.remove(key)));
     }
 
     private void warmupMantleChunkAsync(int chunkX, int chunkZ) {
@@ -475,7 +514,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_mantle_warmup", () -> {
             try {
                 getMantle().getChunk(chunkX, chunkZ);
             } catch (Throwable e) {
@@ -483,11 +522,11 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             } finally {
                 mantleWarmupQueue.remove(key);
             }
-        });
+        }, () -> mantleWarmupQueue.remove(key)));
     }
 
     private boolean onAsyncTick() {
-        if (getEngine().isClosed()) {
+        if (getEngine().isClosing() || getEngine().isClosed()) {
             return false;
         }
 
@@ -496,7 +535,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return false;
         }
 
-        actuallySpawned = 0;
+        actuallySpawned.set(0);
 
         if (!getEngine().getWorld().hasPlatformWorld()) {
             IrisLogging.debug("Can't spawn. No real world");
@@ -509,8 +548,16 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                 World realWorld = BukkitWorldBinding.world(getEngine().getWorld());
                 if (realWorld == null) {
                     entityCount = 0;
+                    entityCountValid = false;
                 } else if (J.isFolia()) {
-                    entityCount = getFoliaLivingEntityCount(realWorld);
+                    Integer count = getFoliaLivingEntityCount(realWorld);
+                    if (count != null) {
+                        entityCount = count;
+                        entityCountValid = true;
+                        resetEntityCountFailures();
+                    } else {
+                        entityCountValid = false;
+                    }
                 } else {
                     CompletableFuture<Integer> future = new CompletableFuture<>();
                     boolean scheduled = J.runGlobal(() -> {
@@ -526,14 +573,32 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                             future.completeExceptionally(ex);
                         }
                     });
-                    entityCount = scheduled ? future.get(2, TimeUnit.SECONDS) : 0;
+                    if (scheduled) {
+                        entityCount = future.get(2, TimeUnit.SECONDS);
+                        entityCountValid = true;
+                        resetEntityCountFailures();
+                    } else {
+                        reportEntityCountFailure("Unable to schedule the global entity count; pausing Iris entity spawning until a complete count is available.", null);
+                    }
                 }
+            } catch (InterruptedException e) {
+                entityCountValid = false;
+                Thread.currentThread().interrupt();
+                return false;
+            } catch (TimeoutException e) {
+                reportEntityCountFailure("Timed out while counting entities; pausing Iris entity spawning until a complete count is available.", null);
+            } catch (ExecutionException e) {
+                Throwable cause = e.getCause() == null ? e : e.getCause();
+                reportEntityCountFailure("Failed to count entities; pausing Iris entity spawning until a complete count is available.", cause);
             } catch (Throwable e) {
-                IrisLogging.reportError(e);
-                close();
+                reportEntityCountFailure("Failed to count entities; pausing Iris entity spawning until a complete count is available.", e);
             }
         }
 
+        if (!entityCountValid) {
+            return false;
+        }
+
         double epx = getEntitySaturation();
         if (epx > IrisSettings.get().getWorld().getTargetSpawnEntitiesPerChunk()) {
             IrisLogging.debug("Can't spawn. The entity per chunk ratio is at " + Form.pc(epx, 2) + " > 100% (total entities " + entityCount + ")");
@@ -549,16 +614,22 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
 
         Position2[] cc = getLoadedChunkPositionsSnapshot(world);
         while (spawnBuffer-- > 0) {
+            if (getEngine().isClosing() || getEngine().isClosed()) {
+                return actuallySpawned.get() > 0;
+            }
+
             if (cc.length == 0) {
                 IrisLogging.debug("Can't spawn. No chunks!");
                 return false;
             }
 
             Position2 c = cc[RNG.r.nextInt(cc.length)];
-            spawnChunkSafely(world, c.getX(), c.getZ(), false);
+            if (!spawnChunkSafely(world, c.getX(), c.getZ(), false)) {
+                return actuallySpawned.get() > 0;
+            }
         }
 
-        return actuallySpawned > 0;
+        return actuallySpawned.get() > 0;
     }
 
     private boolean isPregenActiveForThisWorld() {
@@ -604,13 +675,16 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
 
         try {
             return future.get(2, TimeUnit.SECONDS);
-        } catch (Throwable e) {
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            return new Position2[0];
+        } catch (ExecutionException | TimeoutException e) {
             IrisLogging.reportError(e);
             return new Position2[0];
         }
     }
 
-    private int getFoliaLivingEntityCount(World world) {
+    private Integer getFoliaLivingEntityCount(World world) {
         CompletableFuture<List<Player>> playerFuture = new CompletableFuture<>();
         boolean scheduled = J.runGlobal(() -> {
             try {
@@ -620,18 +694,29 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             }
         });
         if (!scheduled) {
-            return 0;
+            reportEntityCountFailure("Unable to schedule the Folia player snapshot; pausing Iris entity spawning until a complete count is available.", null);
+            return null;
         }
 
         List<Player> players;
         try {
             players = playerFuture.get(2, TimeUnit.SECONDS);
-        } catch (Throwable e) {
-            IrisLogging.reportError(e);
-            return 0;
+        } catch (InterruptedException e) {
+            entityCountValid = false;
+            Thread.currentThread().interrupt();
+            return null;
+        } catch (TimeoutException e) {
+            reportEntityCountFailure("Timed out while reading the Folia player snapshot; pausing Iris entity spawning until a complete count is available.", null);
+            return null;
+        } catch (ExecutionException e) {
+            Throwable cause = e.getCause() == null ? e : e.getCause();
+            reportEntityCountFailure("Failed to read the Folia player snapshot; pausing Iris entity spawning until a complete count is available.", cause);
+            return null;
         }
 
         Map<String, Entity> candidates = new ConcurrentHashMap<>();
+        AtomicBoolean incomplete = new AtomicBoolean();
+        AtomicReference<Throwable> failure = new AtomicReference<>();
 
         CountDownLatch latch = new CountDownLatch(players.size());
         for (Player player : players) {
@@ -651,21 +736,28 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                             candidates.put(nearby.getUniqueId().toString(), nearby);
                         }
                     }
+                } catch (Throwable e) {
+                    incomplete.set(true);
+                    failure.compareAndSet(null, e);
                 } finally {
                     latch.countDown();
                 }
             })) {
+                incomplete.set(true);
                 latch.countDown();
             }
         }
 
-        try {
-            latch.await(2, TimeUnit.SECONDS);
-        } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
+        if (!awaitEntityTasks(latch, 2, TimeUnit.SECONDS) || incomplete.get()) {
+            if (!Thread.currentThread().isInterrupted()) {
+                reportEntityCountFailure("The Folia entity candidate scan was incomplete; pausing Iris entity spawning until a complete count is available.", failure.get());
+            }
+            return null;
         }
 
         AtomicInteger count = new AtomicInteger();
+        incomplete.set(false);
+        failure.set(null);
         CountDownLatch entityLatch = new CountDownLatch(candidates.size());
         for (Entity entity : candidates.values()) {
             if (!J.runEntity(entity, () -> {
@@ -673,47 +765,117 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                     if (entity instanceof LivingEntity && world.equals(entity.getWorld()) && !entity.isDead()) {
                         count.incrementAndGet();
                     }
+                } catch (Throwable e) {
+                    incomplete.set(true);
+                    failure.compareAndSet(null, e);
                 } finally {
                     entityLatch.countDown();
                 }
             })) {
+                incomplete.set(true);
                 entityLatch.countDown();
             }
         }
 
-        try {
-            entityLatch.await(2, TimeUnit.SECONDS);
-        } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
+        if (!awaitEntityTasks(entityLatch, 2, TimeUnit.SECONDS) || incomplete.get()) {
+            if (!Thread.currentThread().isInterrupted()) {
+                reportEntityCountFailure("The Folia entity validation scan was incomplete; pausing Iris entity spawning until a complete count is available.", failure.get());
+            }
+            return null;
         }
+
         return count.get();
     }
 
-    private void spawnChunkSafely(World world, int chunkX, int chunkZ, boolean initial) {
+    static boolean awaitEntityTasks(CountDownLatch latch, long timeout, TimeUnit unit) {
+        try {
+            return latch.await(timeout, unit);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            return false;
+        }
+    }
+
+    private boolean spawnChunkSafely(World world, int chunkX, int chunkZ, boolean initial) {
         if (world == null) {
-            return;
+            return false;
         }
 
         CompletableFuture<Void> future = new CompletableFuture<>();
-        J.runRegion(world, chunkX, chunkZ, () -> {
-            try {
-                if (!world.isChunkLoaded(chunkX, chunkZ) || !Chunks.isSafe(world, chunkX, chunkZ)) {
-                    return;
-                }
-
-                spawnIn(world.getChunkAt(chunkX, chunkZ), initial);
-            } finally {
-                future.complete(null);
+        AtomicBoolean failureReported = new AtomicBoolean();
+        future.whenComplete((ignored, failure) -> {
+            if (failure != null) {
+                reportSpawnFailure(chunkX, chunkZ, failure, failureReported);
             }
         });
+        boolean scheduled;
+        try {
+            scheduled = J.runRegion(world, chunkX, chunkZ, () -> {
+                try {
+                    if (!world.isChunkLoaded(chunkX, chunkZ) || !Chunks.isSafe(world, chunkX, chunkZ)) {
+                        future.complete(null);
+                        return;
+                    }
+
+                    spawnIn(world.getChunkAt(chunkX, chunkZ), initial);
+                    future.complete(null);
+                } catch (Throwable e) {
+                    future.completeExceptionally(e);
+                }
+            });
+        } catch (Throwable e) {
+            IrisLogging.reportError("Failed to schedule an Iris entity spawn for chunk " + chunkX + "," + chunkZ + ".", e);
+            return false;
+        }
+
+        if (!scheduled) {
+            IrisLogging.debug("Skipped Iris entity spawning because the region task was not accepted for chunk " + chunkX + "," + chunkZ + ".");
+            return false;
+        }
 
         try {
             future.get(5, TimeUnit.SECONDS);
-        } catch (Throwable e) {
-            IrisLogging.reportError(e);
+            return true;
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            return false;
+        } catch (TimeoutException e) {
+            IrisLogging.warn("Timed out waiting for Iris entity spawning in chunk %d,%d; deferring the remaining spawn buffer.", chunkX, chunkZ);
+            return false;
+        } catch (ExecutionException e) {
+            Throwable cause = e.getCause() == null ? e : e.getCause();
+            reportSpawnFailure(chunkX, chunkZ, cause, failureReported);
+            return false;
         }
     }
 
+    private void reportEntityCountFailure(String message, Throwable error) {
+        entityCountValid = false;
+        if (error != null) {
+            if (entityCountErrorReported.compareAndSet(false, true)) {
+                IrisLogging.reportError(message, error);
+            }
+            return;
+        }
+
+        if (entityCountWarningReported.compareAndSet(false, true)) {
+            IrisLogging.warn(message);
+        }
+    }
+
+    private void resetEntityCountFailures() {
+        entityCountWarningReported.set(false);
+        entityCountErrorReported.set(false);
+    }
+
+    private void reportSpawnFailure(int chunkX, int chunkZ, Throwable failure, AtomicBoolean failureReported) {
+        if (!failureReported.compareAndSet(false, true)) {
+            return;
+        }
+        Throwable cause = failure.getCause() == null ? failure : failure.getCause();
+        IrisLogging.reportError("Failed to spawn Iris entities in chunk " + chunkX + "," + chunkZ + ".", cause);
+    }
+
     private void spawnIn(Chunk c, boolean initial) {
         if (getEngine().isClosed()) {
             return;
@@ -736,8 +898,10 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                 }
 
                 spawn(block, s, false);
-                J.runRegion(c.getWorld(), c.getX(), c.getZ(), () -> raiseInitialSpawnMarkerFlag(c.getWorld(), c.getX(), c.getZ(),
-                        () -> spawn(block, s, true)));
+                J.runRegion(c.getWorld(), c.getX(), c.getZ(), managedTask(
+                        "bukkit_world_manager_marker_spawn_followup",
+                        () -> raiseInitialSpawnMarkerFlag(c.getWorld(), c.getX(), c.getZ(),
+                                () -> spawn(block, s, true))));
             });
         }
 
@@ -775,17 +939,13 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
         if (v == null || v.getReferenceSpawner() == null)
             return;
 
-        try {
-            spawn(c, v);
-        } catch (Throwable e) {
-            J.runRegion(c.getWorld(), c.getX(), c.getZ(), () -> spawn(c, v));
-        }
+        spawn(c, v);
     }
 
     private void spawn(Chunk c, IrisEntitySpawn i) {
         IrisSpawner ref = i.getReferenceSpawner();
         int s = i.spawn(getEngine(), c, RNG.r);
-        actuallySpawned += s;
+        actuallySpawned.addAndGet(s);
         if (s > 0) {
             ref.spawn(getEngine(), c.getX(), c.getZ());
         }
@@ -797,7 +957,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
 
         int s = i.spawn(getEngine(), pos, RNG.r);
-        actuallySpawned += s;
+        actuallySpawned.addAndGet(s);
         if (s > 0) {
             ref.spawn(getEngine(), PowerOfTwoCoordinates.blockToChunkFloor(pos.getX()), PowerOfTwoCoordinates.blockToChunkFloor(pos.getZ()));
         }
@@ -857,10 +1017,10 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
 
         int cX = e.getX(), cZ = e.getZ();
         Long key = Cache.key(cX, cZ);
-        cleanup.put(key, cleanupService.schedule(() -> {
+        cleanup.put(key, cleanupService.schedule(managedTask("bukkit_world_manager_chunk_cleanup", () -> {
             cleanup.remove(key);
             getEngine().cleanupMantleChunk(cX, cZ);
-        }, Math.max(IrisSettings.get().getPerformance().mantleCleanupDelay * 50L, 0), TimeUnit.MILLISECONDS));
+        }, () -> cleanup.remove(key)), Math.max(IrisSettings.get().getPerformance().mantleCleanupDelay * 50L, 0), TimeUnit.MILLISECONDS));
     }
 
     @Override
@@ -898,15 +1058,17 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
     @Override
     public void teleportAsync(PlayerTeleportEvent e) {
         e.setCancelled(true);
-        warmupAreaAsync(e.getPlayer(), e.getTo(), () -> J.runEntity(e.getPlayer(), () -> {
+        warmupAreaAsync(e.getPlayer(), e.getTo(), () -> J.runEntity(e.getPlayer(), managedTask(
+                "bukkit_world_manager_teleport",
+                () -> {
             ignoreTP.set(true);
             e.getPlayer().teleport(e.getTo(), e.getCause());
             ignoreTP.set(false);
-        }));
+        })));
     }
 
     private void warmupAreaAsync(Player player, Location to, Runnable r) {
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_teleport_warmup", () -> {
             int viewDistance = 2;
             KList<Future<Chunk>> futures = new KList<>();
             for (int i = -viewDistance; i <= viewDistance; i++) {
@@ -945,7 +1107,7 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                     return "Loading Chunks";
                 }
             }.queue(futures).execute(new VolmitSender(player), true, r);
-        });
+        }));
     }
 
     public Map<IrisPosition, KSet<IrisSpawner>> getSpawnersFromMarkers(Chunk c) {
@@ -1024,14 +1186,14 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             return;
         }
 
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_marker_scan", () -> {
             try {
                 Map<IrisPosition, MarkerSpawnData> markerData = collectMarkerSpawnData(chunkX, chunkZ);
                 if (markerData.isEmpty()) {
                     return;
                 }
 
-                J.runRegion(world, chunkX, chunkZ, () -> {
+                J.runRegion(world, chunkX, chunkZ, managedTask("bukkit_world_manager_marker_scan_region", () -> {
                     if (!world.isChunkLoaded(chunkX, chunkZ) || !Chunks.isSafe(world, chunkX, chunkZ)) {
                         return;
                     }
@@ -1050,13 +1212,13 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
 
                         consumer.accept(new IrisPosition(relative.getX(), relative.getY() + minY, relative.getZ()), data.spawners);
                     });
-                });
+                }));
             } catch (Throwable e) {
                 IrisLogging.reportError(e);
             } finally {
                 markerScanQueue.remove(key);
             }
-        });
+        }, () -> markerScanQueue.remove(key)));
     }
 
     private Map<IrisPosition, MarkerSpawnData> collectMarkerSpawnData(int chunkX, int chunkZ) {
@@ -1107,13 +1269,13 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
     }
 
     private void removeMarkerAsync(IrisPosition marker) {
-        J.a(() -> {
+        J.a(managedTask("bukkit_world_manager_remove_marker", () -> {
             try {
                 getMantle().remove(marker.getX(), marker.getY(), marker.getZ(), MatterMarker.class);
             } catch (Throwable e) {
                 IrisLogging.reportError(e);
             }
-        });
+        }));
     }
 
     private static final class MarkerSpawnData {
@@ -1127,21 +1289,6 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
             int blockX = e.getBlock().getX();
             int mantleY = toMantleY(e.getBlock().getY(), getEngine().getWorld().minHeight());
             int blockZ = e.getBlock().getZ();
-            J.a(() -> {
-                MatterMarker marker = getMantle().get(blockX, mantleY, blockZ, MatterMarker.class);
-
-                if (marker != null) {
-                    if (marker.getTag().equals("cave_floor") || marker.getTag().equals("cave_ceiling")) {
-                        return;
-                    }
-
-                    IrisMarker mark = getData().getMarkerLoader().load(marker.getTag());
-
-                    if (mark == null || mark.isRemoveOnChange()) {
-                        getMantle().remove(blockX, mantleY, blockZ, MatterMarker.class);
-                    }
-                }
-            });
 
             KList<ItemStack> d = new KList<>();
             IrisBiome b = EngineBukkitOps.getBiome(getEngine(), e.getBlock().getLocation());
@@ -1159,15 +1306,29 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
                 e.setDropItems(false);
             }
 
-            if (d.isNotEmpty()) {
-                World w = e.getBlock().getWorld();
-                Location dropLocation = e.getBlock().getLocation().clone().add(.5, .5, .5);
-                Runnable dropTask = () -> d.forEach(item -> w.dropItemNaturally(dropLocation, item));
-                if (!J.runAt(dropLocation, dropTask)) {
-                    if (!J.isFolia()) {
-                        J.s(dropTask);
-                    }
+            World w = e.getBlock().getWorld();
+            Location blockLocation = e.getBlock().getLocation();
+            Location dropLocation = blockLocation.clone().add(.5, .5, .5);
+            BlockDropRouter dropRouter = e instanceof BlockDropRouter router ? router : null;
+            Runnable finalizedBreak = managedTask("bukkit_world_manager_block_break_finalize", () -> {
+                if (e.isCancelled()) {
+                    return;
                 }
+                J.a(managedTask("bukkit_world_manager_block_break_marker", () -> {
+                    MatterMarker marker = getMantle().get(blockX, mantleY, blockZ, MatterMarker.class);
+                    if (marker == null || marker.getTag().equals("cave_floor") || marker.getTag().equals("cave_ceiling")) {
+                        return;
+                    }
+
+                    IrisMarker mark = getData().getMarkerLoader().load(marker.getTag());
+                    if (mark == null || mark.isRemoveOnChange()) {
+                        getMantle().remove(blockX, mantleY, blockZ, MatterMarker.class);
+                    }
+                }));
+                routeDrops(d, dropRouter, item -> w.dropItemNaturally(dropLocation, item));
+            });
+            if (!J.runAt(blockLocation, finalizedBreak, 1) && !J.isFolia()) {
+                J.s(finalizedBreak, 1);
             }
         }
     }
@@ -1176,6 +1337,22 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
         return worldY - minHeight;
     }
 
+    static <T> void routeDrops(Iterable<T> drops, BlockDropRouter router, Consumer<T> fallback) {
+        for (T drop : drops) {
+            boolean routed = false;
+            if (router != null) {
+                try {
+                    routed = router.routeDrop(drop);
+                } catch (Throwable error) {
+                    IrisLogging.reportError("Failed to route a deferred Iris block drop.", error);
+                }
+            }
+            if (!routed) {
+                fallback.accept(drop);
+            }
+        }
+    }
+
     static int toWorldY(int mantleY, int minHeight) {
         return mantleY + minHeight;
     }
@@ -1190,11 +1367,35 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
     }
 
     @Override
-    public void close() {
-        super.close();
-        looper.interrupt();
-        if (cleanupService != null) {
-            cleanupService.shutdownNow();
+    public synchronized void close() {
+        Throwable failure = null;
+        try {
+            super.close();
+        } catch (Throwable e) {
+            failure = e;
+        }
+        if (!looperStopped) {
+            try {
+                if (looper != null) {
+                    looper.interrupt();
+                }
+                looperStopped = true;
+            } catch (Throwable e) {
+                failure = appendCloseFailure(failure, e);
+            }
+        }
+        if (!cleanupServiceStopped) {
+            try {
+                if (cleanupService != null) {
+                    cleanupService.shutdownNow();
+                }
+                cleanupServiceStopped = true;
+            } catch (Throwable e) {
+                failure = appendCloseFailure(failure, e);
+            }
+        }
+        if (failure != null) {
+            throw new IllegalStateException("Failed to completely stop the Bukkit Iris world manager.", failure);
         }
     }
 
@@ -1212,6 +1413,16 @@ public class IrisWorldManager extends EngineAssignedWorldManager {
         return (double) entityCount / (loadedChunkCount + 1) * 1.28;
     }
 
+    private static Throwable appendCloseFailure(Throwable failure, Throwable next) {
+        if (failure == null) {
+            return next;
+        }
+        if (failure != next) {
+            failure.addSuppressed(next);
+        }
+        return failure;
+    }
+
     @Data
     private static class ChunkCounter implements Predicate<IrisSpawner> {
         private final Entity[] entities;

core/src/main/java/art/arcane/iris/engine/UpperDimensionContext.java

@@ -69,7 +69,7 @@ public class UpperDimensionContext implements DataProvider {
                 engine.getData(),
                 chunkHeight,
                 complex.getHeightStream(),
-                complex.getBaseBiomeStream(),
+                complex.getTrueBiomeStream(),
                 complex.getRegionStream(),
                 complex.getRockStream(),
                 true
@@ -89,6 +89,8 @@ public class UpperDimensionContext implements DataProvider {
 
         Map<IrisInterpolator, Set<IrisGenerator>> generators = new HashMap<>();
         Set<IrisBiome> allBiomes = Collections.newSetFromMap(new IdentityHashMap<>());
+        Map<IrisBiome, IrisComplex.ChildSelectionPlan> childSelectionPlans =
+                Collections.synchronizedMap(new IdentityHashMap<>());
         upperDim.getRegions().forEach(regionKey -> {
             IrisRegion region = upperData.getRegionLoader().load(regionKey);
             if (region != null) {
@@ -135,8 +137,7 @@ public class UpperDimensionContext implements DataProvider {
                         .zoom(upperDim.getBiomeZoom())
                         .zoom(upperDim.getLandZoom())
                         .zoom(r.getLandBiomeZoom())
-                        .selectRarity(upperData.getBiomeLoader().loadAll(r.getLandBiomes(),
-                                t -> t.setInferredType(InferredType.LAND))))
+                        .selectRarity(loadInferredBiomes(upperData, r.getLandBiomes(), InferredType.LAND)))
                 .convertAware2D(ProceduralStream::get);
         ProceduralStream<IrisBiome> seaBiomeStream = regionStream
                 .convert(r -> upperDim.getSeaBiomeStyle()
@@ -144,16 +145,14 @@ public class UpperDimensionContext implements DataProvider {
                         .zoom(upperDim.getBiomeZoom())
                         .zoom(upperDim.getSeaZoom())
                         .zoom(r.getSeaBiomeZoom())
-                        .selectRarity(upperData.getBiomeLoader().loadAll(r.getSeaBiomes(),
-                                t -> t.setInferredType(InferredType.SEA))))
+                        .selectRarity(loadInferredBiomes(upperData, r.getSeaBiomes(), InferredType.SEA)))
                 .convertAware2D(ProceduralStream::get);
         ProceduralStream<IrisBiome> shoreBiomeStream = regionStream
                 .convert(r -> upperDim.getShoreBiomeStyle()
                         .create(rng.nextParallelRNG(InferredType.SHORE.ordinal()), upperData).stream()
                         .zoom(upperDim.getBiomeZoom())
                         .zoom(r.getShoreBiomeZoom())
-                        .selectRarity(upperData.getBiomeLoader().loadAll(r.getShoreBiomes(),
-                                t -> t.setInferredType(InferredType.SHORE))))
+                        .selectRarity(loadInferredBiomes(upperData, r.getShoreBiomes(), InferredType.SHORE)))
                 .convertAware2D(ProceduralStream::get);
 
         Map<InferredType, ProceduralStream<IrisBiome>> inferredStreams = new HashMap<>();
@@ -170,7 +169,9 @@ public class UpperDimensionContext implements DataProvider {
                 .convertAware2D((t, x, z) -> {
                     ProceduralStream<IrisBiome> stream = inferredStreams.get(t);
                     return stream != null ? stream.get(x, z) : inferredStreams.get(InferredType.LAND).get(x, z);
-                });
+                })
+                .convertAware2D((biome, x, z) -> implode(
+                        biome, x, z, rng, dataProvider, childSelectionPlans, 3));
 
         KList<IrisShapedGeneratorStyle> overlayNoise = upperDim.getOverlayNoise();
         ProceduralStream<Double> overlayStream = overlayNoise.isEmpty()
@@ -235,6 +236,23 @@ public class UpperDimensionContext implements DataProvider {
             return Math.max(Math.min(interpolatedHeight + fluidHeight + overlayStream.get(x, z), chunkHeight), 0);
         }, Interpolated.DOUBLE);
 
+        ProceduralStream<IrisBiome> finalBiomeStream = heightStream.convertAware2D((height, x, z) -> {
+            IrisBiome baseBiome = baseBiomeStream.get(x, z);
+            IrisBiome resolved = IrisComplex.resolveSurfaceBiome(
+                    height,
+                    baseBiome,
+                    regionStream.get(x, z),
+                    x,
+                    z,
+                    fluidHeight,
+                    landBiomeStream,
+                    seaBiomeStream,
+                    shoreBiomeStream);
+            return resolved == baseBiome
+                    ? baseBiome
+                    : implode(resolved, x, z, rng, dataProvider, childSelectionPlans, 3);
+        });
+
         ProceduralStream<PlatformBlockState> rockStream = upperDim.getRockPalette()
                 .getLayerGenerator(rng.nextParallelRNG(45), upperData).stream()
                 .select(upperDim.getRockPalette().getBlockData(upperData));
@@ -244,13 +262,67 @@ public class UpperDimensionContext implements DataProvider {
                 upperData,
                 chunkHeight,
                 heightStream,
-                baseBiomeStream,
+                finalBiomeStream,
                 regionStream,
                 rockStream,
                 false
         );
     }
 
+    private static KList<IrisBiome> loadInferredBiomes(IrisData data, KList<String> keys, InferredType type) {
+        KList<IrisBiome> inferred = new KList<>();
+        for (IrisBiome biome : data.getBiomeLoader().loadAll(keys)) {
+            inferred.add(biome.withInferredType(type));
+        }
+        return inferred;
+    }
+
+    private static IrisBiome implode(
+            IrisBiome biome,
+            double x,
+            double z,
+            RNG rng,
+            DataProvider dataProvider,
+            Map<IrisBiome, IrisComplex.ChildSelectionPlan> childSelectionPlans,
+            int remainingDepth
+    ) {
+        if (biome == null || remainingDepth < 0 || biome.getChildren().isEmpty()) {
+            return biome;
+        }
+
+        IrisComplex.ChildSelectionPlan selectionPlan = childSelectionPlans.get(biome);
+        if (selectionPlan == null) {
+            synchronized (childSelectionPlans) {
+                selectionPlan = childSelectionPlans.get(biome);
+                if (selectionPlan == null) {
+                    KList<IrisBiome> options = new KList<>();
+                    for (IrisBiome child : biome.getRealChildren(dataProvider)) {
+                        if (child != null) {
+                            options.add(child);
+                        }
+                    }
+                    options.add(biome);
+                    selectionPlan = IrisComplex.ChildSelectionPlan.create(options);
+                    childSelectionPlans.put(biome, selectionPlan);
+                }
+            }
+        }
+
+        IrisBiome selected = selectionPlan.select(
+                biome.getChildrenGenerator(rng, 123, biome.getChildShrinkFactor()), x, z);
+        if (selected == null) {
+            return biome;
+        }
+        return implode(
+                selected.withInferredType(biome.getInferredType()),
+                x,
+                z,
+                rng,
+                dataProvider,
+                childSelectionPlans,
+                remainingDepth - 1);
+    }
+
     public int getUpperSurfaceY(int x, int z) {
         double rawHeight = heightStream.get((double) x, (double) z);
         return chunkHeight - 1 - (int) Math.round(rawHeight);

core/src/main/java/art/arcane/iris/engine/framework/Engine.java

@@ -48,6 +48,7 @@ import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.iris.util.project.context.ChunkContext;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.iris.util.common.data.DataProvider;
 import art.arcane.iris.util.common.data.B;
 import art.arcane.volmlib.util.documentation.BlockCoordinates;
@@ -127,6 +128,15 @@ public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer,
             return GenerationSessionLease.noop();
         }
 
+        IrisContext context = IrisContext.get();
+        if (context != null && context.getEngine() == this && context.getGenerationSessionId() != 0L) {
+            return generationSessions.continueSession(operation, context.getGenerationSessionId());
+        }
+        if (isClosing() || isClosed()) {
+            throw new GenerationSessionException("Generation session rejected new work for " + operation
+                    + " while the Iris engine is closing.", isClosed());
+        }
+
         return generationSessions.acquire(operation);
     }
 

core/src/main/java/art/arcane/iris/engine/framework/EngineAssignedWorldManager.java

@@ -33,82 +33,194 @@ import org.bukkit.event.block.BlockPlaceEvent;
 import org.bukkit.event.world.ChunkLoadEvent;
 import org.bukkit.event.world.ChunkUnloadEvent;
 import org.bukkit.event.world.WorldSaveEvent;
-import org.bukkit.event.world.WorldUnloadEvent;
 
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Supplier;
 
 public abstract class EngineAssignedWorldManager extends EngineAssignedComponent implements EngineWorldManager, BukkitEngineWorldManager, Listener {
-    private final int taskId;
+    private final Object managerLifecycleLock;
+    private final AtomicBoolean started;
+    private boolean listenerRegistered;
+    private boolean closeRequested;
+    private int taskId;
     protected AtomicBoolean ignoreTP = new AtomicBoolean(false);
 
     public EngineAssignedWorldManager() {
         super(null, null);
+        managerLifecycleLock = new Object();
+        started = new AtomicBoolean(false);
         taskId = -1;
     }
 
     public EngineAssignedWorldManager(Engine engine) {
         super(engine, "World");
-        BukkitPlatform.volmitPlugin().registerListener(this);
-        taskId = J.sr(this::onTick, 1);
+        managerLifecycleLock = new Object();
+        started = new AtomicBoolean(false);
+        taskId = -1;
+    }
+
+    @Override
+    public void start() {
+        synchronized (managerLifecycleLock) {
+            if (started.get()) {
+                return;
+            }
+            if (closeRequested) {
+                throw new IllegalStateException("Cannot restart a closed Iris world manager.");
+            }
+
+            started.set(true);
+            try {
+                listenerRegistered = true;
+                registerManagerListener();
+                taskId = scheduleManagerTick(() -> runManagerTask("bukkit_world_manager_tick", this::onTick));
+            } catch (Throwable e) {
+                started.set(false);
+                closeRequested = true;
+                Throwable cleanupFailure = closeManagerResources();
+                if (cleanupFailure != null) {
+                    e.addSuppressed(cleanupFailure);
+                }
+                throw propagate(e);
+            }
+        }
     }
 
     @EventHandler
     public void on(IrisEngineHotloadEvent e) {
-        for (Player i : BukkitWorldBinding.players(e.getEngine().getWorld())) {
-            i.playSound(i.getLocation(), Sound.BLOCK_AMETHYST_BLOCK_BREAK, 1f, 1.8f);
-            VolmitSender s = new VolmitSender(i);
-            s.sendTitle(C.IRIS + "Engine " + C.AQUA + "<font:minecraft:uniform>Hotloaded", 70, 60, 410);
-        }
+        runManagerTask("bukkit_world_manager_hotload_event", () -> {
+            for (Player i : BukkitWorldBinding.players(e.getEngine().getWorld())) {
+                i.playSound(i.getLocation(), Sound.BLOCK_AMETHYST_BLOCK_BREAK, 1f, 1.8f);
+                VolmitSender s = new VolmitSender(i);
+                s.sendTitle(C.IRIS + "Engine " + C.AQUA + "<font:minecraft:uniform>Hotloaded", 70, 60, 410);
+            }
+        });
     }
 
     @EventHandler
     public void on(WorldSaveEvent e) {
-        if (e.getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            getEngine().save();
-        }
-    }
-
-    @EventHandler
-    public void on(WorldUnloadEvent e) {
-        if (e.getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            getEngine().close();
-        }
+        runManagerTask("bukkit_world_manager_save", () -> {
+            if (e.getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
+                getEngine().save();
+            }
+        });
     }
 
     @EventHandler
     public void on(BlockBreakEvent e) {
-        if (e.getPlayer().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            onBlockBreak(e);
-        }
+        runManagerTask("bukkit_world_manager_block_break", () -> {
+            if (e.getPlayer().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
+                onBlockBreak(e);
+            }
+        });
     }
 
     @EventHandler
     public void on(BlockPlaceEvent e) {
-        if (e.getPlayer().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            onBlockPlace(e);
-        }
+        runManagerTask("bukkit_world_manager_block_place", () -> {
+            if (e.getPlayer().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
+                onBlockPlace(e);
+            }
+        });
     }
 
     @EventHandler
     public void on(ChunkLoadEvent e) {
-        if (e.getChunk().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            onChunkLoad(e.getChunk(), e.isNewChunk());
-        }
+        runManagerTask("bukkit_world_manager_chunk_load", () -> {
+            if (e.getChunk().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
+                onChunkLoad(e.getChunk(), e.isNewChunk());
+            }
+        });
     }
 
     @EventHandler
     public void on(ChunkUnloadEvent e) {
-        if (e.getChunk().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
-            onChunkUnload(e.getChunk());
-        }
+        runManagerTask("bukkit_world_manager_chunk_unload", () -> {
+            if (e.getChunk().getWorld().equals(BukkitWorldBinding.world(getTarget().getWorld()))) {
+                onChunkUnload(e.getChunk());
+            }
+        });
     }
 
     @Override
     public void close() {
-        super.close();
-        BukkitPlatform.volmitPlugin().unregisterListener(this);
-        if (taskId != -1) {
-            J.csr(taskId);
+        Throwable failure;
+        synchronized (managerLifecycleLock) {
+            closeRequested = true;
+            started.set(false);
+            failure = closeManagerResources();
+        }
+        if (failure != null) {
+            throw new IllegalStateException("Failed to completely stop the Iris world manager.", failure);
         }
     }
+
+    protected void registerManagerListener() {
+        BukkitPlatform.volmitPlugin().registerListener(this);
+    }
+
+    protected int scheduleManagerTick(Runnable tick) {
+        return J.sr(tick, 1);
+    }
+
+    protected void unregisterManagerListener() {
+        BukkitPlatform.volmitPlugin().unregisterListener(this);
+    }
+
+    protected void cancelManagerTick(int scheduledTaskId) {
+        J.csr(scheduledTaskId);
+    }
+
+    private Throwable closeManagerResources() {
+        Throwable failure = null;
+        if (listenerRegistered) {
+            try {
+                unregisterManagerListener();
+                listenerRegistered = false;
+            } catch (Throwable e) {
+                failure = e;
+            }
+        }
+        if (taskId != -1) {
+            try {
+                cancelManagerTick(taskId);
+                taskId = -1;
+            } catch (Throwable e) {
+                if (failure == null) {
+                    failure = e;
+                } else if (failure != e) {
+                    failure.addSuppressed(e);
+                }
+            }
+        }
+        return failure;
+    }
+
+    private RuntimeException propagate(Throwable failure) {
+        if (failure instanceof RuntimeException runtimeException) {
+            return runtimeException;
+        }
+        if (failure instanceof Error error) {
+            throw error;
+        }
+        return new IllegalStateException(failure);
+    }
+
+    protected boolean runManagerTask(String operation, Runnable task) {
+        if (!started.get()) {
+            return false;
+        }
+        return EngineLifecycleTasks.run(getEngine(), operation, task);
+    }
+
+    protected <T> T callManagerTask(String operation, Supplier<T> task, T unavailable) {
+        if (!started.get()) {
+            return unavailable;
+        }
+        return EngineLifecycleTasks.call(getEngine(), operation, task, unavailable);
+    }
+
+    protected boolean isManagerStarted() {
+        return started.get();
+    }
 }

core/src/main/java/art/arcane/iris/engine/framework/EngineLifecycleTasks.java

@@ -0,0 +1,40 @@
+package art.arcane.iris.engine.framework;
+
+import art.arcane.iris.util.project.context.IrisContext;
+
+import java.util.Objects;
+import java.util.function.Supplier;
+
+public final class EngineLifecycleTasks {
+    private EngineLifecycleTasks() {
+    }
+
+    public static boolean run(Engine engine, String operation, Runnable task) {
+        Objects.requireNonNull(engine);
+        Objects.requireNonNull(operation);
+        Objects.requireNonNull(task);
+        try (GenerationSessionLease lease = engine.acquireGenerationLease(operation);
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            task.run();
+            return true;
+        } catch (GenerationSessionException exception) {
+            if (engine.isClosing() || engine.isClosed() || exception.isExpectedTeardown()) {
+                return false;
+            }
+            throw new IllegalStateException("Iris lifecycle rejected " + operation + ".", exception);
+        }
+    }
+
+    public static <T> T call(Engine engine, String operation, Supplier<T> task, T unavailable) {
+        Objects.requireNonNull(task);
+        try (GenerationSessionLease lease = engine.acquireGenerationLease(operation);
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            return task.get();
+        } catch (GenerationSessionException exception) {
+            if (engine.isClosing() || engine.isClosed() || exception.isExpectedTeardown()) {
+                return unavailable;
+            }
+            throw new IllegalStateException("Iris lifecycle rejected " + operation + ".", exception);
+        }
+    }
+}

core/src/main/java/art/arcane/iris/engine/framework/EngineMetrics.java

@@ -22,6 +22,9 @@ import art.arcane.volmlib.util.atomics.AtomicRollingSequence;
 import art.arcane.volmlib.util.collection.KMap;
 import lombok.Data;
 
+import java.util.LinkedHashMap;
+import java.util.Map;
+
 @Data
 public class EngineMetrics {
     private final AtomicRollingSequence total;
@@ -111,4 +114,24 @@ public class EngineMetrics {
 
         return v;
     }
+
+    public Map<String, Double> telemetryAverages() {
+        Map<String, Double> averages = new LinkedHashMap<>();
+        averages.put("total", total.getAverage());
+        averages.put("updates", updates.getAverage());
+        averages.put("terrain", terrain.getAverage());
+        averages.put("biome", biome.getAverage());
+        averages.put("post", post.getAverage());
+        averages.put("perfection", perfection.getAverage());
+        averages.put("decoration", decoration.getAverage());
+        averages.put("cave", cave.getAverage());
+        averages.put("deposit", deposit.getAverage());
+        averages.put("carve.resolve", carveResolve.getAverage());
+        averages.put("carve.apply", carveApply.getAverage());
+        averages.put("context.prefill", contextPrefill.getAverage());
+        averages.put("pregen.wait.permit", pregenWaitPermit.getAverage());
+        averages.put("pregen.wait.adaptive", pregenWaitAdaptive.getAverage());
+        averages.entrySet().removeIf(entry -> !Double.isFinite(entry.getValue()) || entry.getValue() < 0D);
+        return Map.copyOf(averages);
+    }
 }

core/src/main/java/art/arcane/iris/engine/framework/EngineTarget.java

@@ -32,8 +32,8 @@ import lombok.ToString;
 public class EngineTarget {
     private final MultiBurst burster;
     private final IrisData data;
-    private IrisDimension dimension;
-    private IrisWorld world;
+    private final IrisDimension dimension;
+    private final IrisWorld world;
 
     public EngineTarget(IrisWorld world, IrisDimension dimension, IrisData data) {
         this.world = world;

core/src/main/java/art/arcane/iris/engine/framework/EngineTelemetrySnapshot.java

@@ -0,0 +1,222 @@
+package art.arcane.iris.engine.framework;
+
+import art.arcane.iris.engine.object.IrisEngineStatistics;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public record EngineTelemetrySnapshot(
+        long sampledAtMs,
+        String worldIdentity,
+        String worldName,
+        String dimensionKey,
+        boolean active,
+        boolean studio,
+        boolean closing,
+        boolean failed,
+        long loadedChunks,
+        long loadedEntities,
+        double entitySaturation,
+        long generatedSession,
+        long generatedTotal,
+        double chunksPerSecond,
+        long blockUpdatesPerSecond,
+        int parallelism,
+        int activeGenerationLeases,
+        long hotloadsTotal,
+        long mantleResidentPlates,
+        long mantleQueuedPlates,
+        double mantleIdleMs,
+        Map<String, Double> generationTimingsMs
+) {
+    public EngineTelemetrySnapshot {
+        if (worldIdentity == null || worldIdentity.isBlank()) {
+            throw new IllegalArgumentException("Engine telemetry requires a world identity");
+        }
+        worldIdentity = worldIdentity.trim();
+        worldName = worldName == null || worldName.isBlank() ? worldIdentity : worldName.trim();
+        dimensionKey = dimensionKey == null ? "" : dimensionKey.trim();
+        loadedChunks = Math.max(0L, loadedChunks);
+        loadedEntities = Math.max(0L, loadedEntities);
+        entitySaturation = finiteNonNegative(entitySaturation);
+        generatedSession = Math.max(0L, generatedSession);
+        generatedTotal = Math.max(0L, generatedTotal);
+        chunksPerSecond = finiteNonNegative(chunksPerSecond);
+        blockUpdatesPerSecond = Math.max(0L, blockUpdatesPerSecond);
+        parallelism = Math.max(0, parallelism);
+        activeGenerationLeases = Math.max(0, activeGenerationLeases);
+        hotloadsTotal = Math.max(0L, hotloadsTotal);
+        mantleResidentPlates = Math.max(0L, mantleResidentPlates);
+        mantleQueuedPlates = Math.max(0L, mantleQueuedPlates);
+        mantleIdleMs = finiteNonNegative(mantleIdleMs);
+        generationTimingsMs = sanitizeTimings(generationTimingsMs);
+    }
+
+    public static EngineTelemetrySnapshot capture(Engine engine, double chunksPerSecond, long sampledAtMs) {
+        if (engine == null) {
+            throw new IllegalArgumentException("Engine cannot be null");
+        }
+
+        EngineWorldManager worldManager = engine.getWorldManager();
+        GenerationSessionManager sessions = engine.getGenerationSessions();
+        IrisEngineStatistics statistics = engine.getEngineData().getStatistics();
+        boolean closing = engine.isClosing();
+        boolean closed = engine.isClosed();
+        boolean failed = engine.hasFailed();
+        return new EngineTelemetrySnapshot(
+                sampledAtMs,
+                engine.getWorld().identity(),
+                engine.getWorld().name(),
+                engine.getDimension().getLoadKey(),
+                !closing && !closed && !failed,
+                engine.isStudio(),
+                closing,
+                failed,
+                worldManager == null ? 0L : worldManager.getChunkCount(),
+                worldManager == null ? 0L : worldManager.getEntityCount(),
+                worldManager == null ? 0D : worldManager.getEntitySaturation(),
+                engine.getGenerated(),
+                statistics == null ? 0L : statistics.getChunksGenerated(),
+                chunksPerSecond,
+                engine.getBlockUpdatesPerSecond(),
+                engine.getParallelism(),
+                sessions == null ? 0 : sessions.activeLeases(),
+                statistics == null ? 0L : statistics.getTotalHotloads(),
+                engine.getMantle().getLoadedRegionCount(),
+                engine.getMantle().getUnloadRegionCount(),
+                engine.getMantle().getAdjustedIdleDuration(),
+                engine.getMetrics().telemetryAverages()
+        );
+    }
+
+    public static Aggregate aggregate(List<EngineTelemetrySnapshot> snapshots) {
+        List<EngineTelemetrySnapshot> safeSnapshots = snapshots == null ? List.of() : snapshots;
+        int active = 0;
+        int studio = 0;
+        int closing = 0;
+        int failed = 0;
+        long loadedChunks = 0L;
+        long loadedEntities = 0L;
+        double entitySaturation = 0D;
+        long generatedSession = 0L;
+        long generatedTotal = 0L;
+        double chunksPerSecond = 0D;
+        long blockUpdatesPerSecond = 0L;
+        int parallelism = 0;
+        int activeGenerationLeases = 0;
+        long hotloadsTotal = 0L;
+        long mantleResidentPlates = 0L;
+        long mantleQueuedPlates = 0L;
+        double mantleIdleTotal = 0D;
+        double mantleIdleMax = 0D;
+        double mantleIdleMin = Double.POSITIVE_INFINITY;
+        int mantleIdleCount = 0;
+        int worldCount = 0;
+        Map<String, Double> timingMaxima = new LinkedHashMap<>();
+
+        for (EngineTelemetrySnapshot snapshot : safeSnapshots) {
+            if (snapshot == null) {
+                continue;
+            }
+            worldCount++;
+            active += snapshot.active() ? 1 : 0;
+            studio += snapshot.studio() ? 1 : 0;
+            closing += snapshot.closing() ? 1 : 0;
+            failed += snapshot.failed() ? 1 : 0;
+            loadedChunks += snapshot.loadedChunks();
+            loadedEntities += snapshot.loadedEntities();
+            entitySaturation = Math.max(entitySaturation, snapshot.entitySaturation());
+            generatedSession += snapshot.generatedSession();
+            generatedTotal += snapshot.generatedTotal();
+            chunksPerSecond += snapshot.chunksPerSecond();
+            blockUpdatesPerSecond += snapshot.blockUpdatesPerSecond();
+            parallelism += snapshot.parallelism();
+            activeGenerationLeases += snapshot.activeGenerationLeases();
+            hotloadsTotal += snapshot.hotloadsTotal();
+            mantleResidentPlates += snapshot.mantleResidentPlates();
+            mantleQueuedPlates += snapshot.mantleQueuedPlates();
+            mantleIdleTotal += snapshot.mantleIdleMs();
+            mantleIdleMax = Math.max(mantleIdleMax, snapshot.mantleIdleMs());
+            mantleIdleMin = Math.min(mantleIdleMin, snapshot.mantleIdleMs());
+            mantleIdleCount++;
+            for (Map.Entry<String, Double> entry : snapshot.generationTimingsMs().entrySet()) {
+                timingMaxima.merge(entry.getKey(), entry.getValue(), Math::max);
+            }
+        }
+
+        return new Aggregate(
+                worldCount,
+                active,
+                studio,
+                closing,
+                failed,
+                loadedChunks,
+                loadedEntities,
+                entitySaturation,
+                generatedSession,
+                generatedTotal,
+                chunksPerSecond,
+                blockUpdatesPerSecond,
+                parallelism,
+                activeGenerationLeases,
+                hotloadsTotal,
+                mantleResidentPlates,
+                mantleQueuedPlates,
+                mantleIdleCount == 0 ? 0D : mantleIdleTotal / mantleIdleCount,
+                mantleIdleMax,
+                mantleIdleCount == 0 ? 0D : mantleIdleMin,
+                Map.copyOf(timingMaxima)
+        );
+    }
+
+    private static double finiteNonNegative(double value) {
+        return Double.isFinite(value) && value > 0D ? value : 0D;
+    }
+
+    private static Map<String, Double> sanitizeTimings(Map<String, Double> timings) {
+        if (timings == null || timings.isEmpty()) {
+            return Map.of();
+        }
+        Map<String, Double> sanitized = new LinkedHashMap<>(timings.size());
+        for (Map.Entry<String, Double> entry : timings.entrySet()) {
+            String key = entry.getKey();
+            Double value = entry.getValue();
+            if (key == null || key.isBlank() || value == null || !Double.isFinite(value) || value < 0D) {
+                continue;
+            }
+            sanitized.put(key, value);
+        }
+        return Map.copyOf(sanitized);
+    }
+
+    public record Aggregate(
+            int worldCount,
+            int active,
+            int studio,
+            int closing,
+            int failed,
+            long loadedChunks,
+            long loadedEntities,
+            double entitySaturationMax,
+            long generatedSession,
+            long generatedTotal,
+            double chunksPerSecond,
+            long blockUpdatesPerSecond,
+            int parallelism,
+            int activeGenerationLeases,
+            long hotloadsTotal,
+            long mantleResidentPlates,
+            long mantleQueuedPlates,
+            double mantleIdleAverageMs,
+            double mantleIdleMaxMs,
+            double mantleIdleMinMs,
+            Map<String, Double> generationTimingMaximaMs
+    ) {
+        public Aggregate {
+            generationTimingMaximaMs = generationTimingMaximaMs == null
+                    ? Map.of()
+                    : Map.copyOf(generationTimingMaximaMs);
+        }
+    }
+}

core/src/main/java/art/arcane/iris/engine/framework/EngineWorldManager.java

@@ -20,6 +20,9 @@ package art.arcane.iris.engine.framework;
 
 @SuppressWarnings("EmptyMethod")
 public interface EngineWorldManager {
+    default void start() {
+    }
+
     void close();
 
     int getEntityCount();

core/src/main/java/art/arcane/iris/engine/framework/GenerationSessionManager.java

@@ -38,6 +38,23 @@ public final class GenerationSessionManager {
         }
     }
 
+    public GenerationSessionLease continueSession(String operation, long sessionId) throws GenerationSessionException {
+        while (true) {
+            GenerationSessionState state = current.get();
+            if (state == null || state.sessionId() != sessionId) {
+                throw rejected(operation, state);
+            }
+
+            state.activeLeases().incrementAndGet();
+            if (state != current.get()) {
+                releaseLease(state);
+                continue;
+            }
+
+            return new GenerationSessionLease(this, state, state.sessionId());
+        }
+    }
+
     public long currentSessionId() {
         GenerationSessionState state = current.get();
         return state == null ? 0L : state.sessionId();

core/src/main/java/art/arcane/iris/engine/framework/HintedLocator.java

@@ -25,6 +25,7 @@ import art.arcane.iris.engine.object.IrisObjectPlacement;
 import art.arcane.iris.engine.object.IrisRegion;
 import art.arcane.iris.util.common.parallel.BurstExecutor;
 import art.arcane.iris.util.common.parallel.MultiBurst;
+import art.arcane.iris.util.project.context.IrisContext;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.volmlib.util.collection.KSet;
@@ -32,7 +33,7 @@ import art.arcane.volmlib.util.math.Position2;
 import art.arcane.volmlib.util.scheduling.PrecisionStopwatch;
 
 import java.util.ArrayDeque;
-import java.util.concurrent.Future;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -105,18 +106,15 @@ public final class HintedLocator<T> implements Locator<T> {
     }
 
     @Override
-    public Future<Position2> find(Engine engine, Position2 pos, long timeout, Consumer<Integer> checks) throws WrongEngineBroException {
+    public CompletableFuture<Position2> find(Engine engine, Position2 pos, long timeout, Consumer<Integer> checks) throws WrongEngineBroException {
         if (engine.isClosed()) {
             throw new WrongEngineBroException();
         }
 
-        Locator.cancelSearch();
-
-        return MultiBurst.burst.completeValue(() -> {
-            AtomicBoolean stop = new AtomicBoolean(false);
-            LocatorCanceller.cancel = () -> stop.set(true);
-
-            try {
+        AtomicBoolean stop = new AtomicBoolean(false);
+        CompletableFuture<Position2> search = MultiBurst.burst.completeValueAsync(() -> {
+            try (GenerationSessionLease lease = engine.acquireGenerationLease("hinted_locator_search");
+                 IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
                 SearchPlan plan = planner.apply(engine);
 
                 if (!plan.isPossible()) {
@@ -124,10 +122,9 @@ public final class HintedLocator<T> implements Locator<T> {
                 }
 
                 return search(engine, plan, pos, timeout, checks, stop);
-            } finally {
-                LocatorCanceller.cancel = null;
             }
         });
+        return LocatorCanceller.requestScoped(search, stop);
     }
 
     private Position2 search(Engine engine, SearchPlan plan, Position2 pos, long timeout, Consumer<Integer> checks, AtomicBoolean stop) {
@@ -140,7 +137,7 @@ public final class HintedLocator<T> implements Locator<T> {
         KList<Position2> batch = new KList<>();
 
         for (int ring = 0; ring <= maxRing; ring++) {
-            if (stop.get() || stopwatch.getMilliseconds() >= timeout) {
+            if (stop.get() || engine.isClosing() || stopwatch.getMilliseconds() >= timeout) {
                 return null;
             }
 
@@ -173,7 +170,7 @@ public final class HintedLocator<T> implements Locator<T> {
             int index = i;
             Position2 sample = batch.get(i);
             executor.queue(() -> {
-                if (stop.get() || (fine && matched.get())) {
+                if (stop.get() || engine.isClosing() || (fine && matched.get())) {
                     return;
                 }
 
@@ -210,7 +207,7 @@ public final class HintedLocator<T> implements Locator<T> {
                 return batch.get(i);
             }
 
-            if (stop.get() || stopwatch.getMilliseconds() >= timeout) {
+            if (stop.get() || engine.isClosing() || stopwatch.getMilliseconds() >= timeout) {
                 return null;
             }
 
@@ -228,7 +225,7 @@ public final class HintedLocator<T> implements Locator<T> {
         KList<Position2> cells = new KList<>();
 
         for (int ring = 0; ring <= stride; ring++) {
-            if (stop.get() || stopwatch.getMilliseconds() >= timeout) {
+            if (stop.get() || engine.isClosing() || stopwatch.getMilliseconds() >= timeout) {
                 return null;
             }
 
@@ -239,7 +236,7 @@ public final class HintedLocator<T> implements Locator<T> {
 
             for (Position2 cell : cells) {
                 executor.queue(() -> {
-                    if (stop.get() || found.get() != null) {
+                    if (stop.get() || engine.isClosing() || found.get() != null) {
                         return;
                     }
 

core/src/main/java/art/arcane/iris/engine/framework/Locator.java

@@ -34,7 +34,7 @@ import art.arcane.iris.util.common.parallel.MultiBurst;
 import art.arcane.volmlib.util.scheduling.PrecisionStopwatch;
 
 import java.util.Set;
-import java.util.concurrent.Future;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -42,13 +42,6 @@ import java.util.function.Consumer;
 
 @FunctionalInterface
 public interface Locator<T> {
-    static void cancelSearch() {
-        if (LocatorCanceller.cancel != null) {
-            LocatorCanceller.cancel.run();
-            LocatorCanceller.cancel = null;
-        }
-    }
-
     static Locator<IrisRegion> region(String loadKey) {
         Locator<IrisRegion> exact = (e, c) -> e.getRegion((c.getX() << 4) + 8, (c.getZ() << 4) + 8).getLoadKey().equals(loadKey);
         return new HintedLocator<>(exact, (engine) -> HintedLocator.regionPlan(engine, loadKey));
@@ -107,55 +100,54 @@ public interface Locator<T> {
 
     boolean matches(Engine engine, Position2 chunk);
 
-    default Future<Position2> find(Engine engine, Position2 pos, long timeout, Consumer<Integer> checks) throws WrongEngineBroException {
+    default CompletableFuture<Position2> find(Engine engine, Position2 pos, long timeout, Consumer<Integer> checks) throws WrongEngineBroException {
         if (engine.isClosed()) {
             throw new WrongEngineBroException();
         }
 
-        cancelSearch();
+        AtomicBoolean stop = new AtomicBoolean(false);
+        CompletableFuture<Position2> search = MultiBurst.burst.completeValueAsync(() -> {
+            try (GenerationSessionLease lease = engine.acquireGenerationLease("locator_search");
+                 IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+                int tc = IrisSettings.getThreadCount(IrisSettings.get().getConcurrency().getParallelism()) * 32;
+                MultiBurst burst = MultiBurst.burst;
+                AtomicBoolean found = new AtomicBoolean(false);
+                AtomicInteger searched = new AtomicInteger();
+                AtomicReference<Position2> foundPos = new AtomicReference<>();
+                PrecisionStopwatch px = PrecisionStopwatch.start();
+                AtomicReference<Position2> next = new AtomicReference<>(pos);
+                Spiraler s = new Spiraler(100000, 100000, (x, z) -> next.set(new Position2(x, z)));
+                s.setOffset(pos.getX(), pos.getZ());
+                s.next();
+                while (!found.get() && !stop.get() && !engine.isClosing() && px.getMilliseconds() < timeout) {
+                    BurstExecutor e = burst.burst(tc);
 
-        return MultiBurst.burst.completeValue(() -> {
-            int tc = IrisSettings.getThreadCount(IrisSettings.get().getConcurrency().getParallelism()) * 32;
-            MultiBurst burst = MultiBurst.burst;
-            AtomicBoolean found = new AtomicBoolean(false);
-            AtomicInteger searched = new AtomicInteger();
-            AtomicBoolean stop = new AtomicBoolean(false);
-            AtomicReference<Position2> foundPos = new AtomicReference<>();
-            PrecisionStopwatch px = PrecisionStopwatch.start();
-            LocatorCanceller.cancel = () -> stop.set(true);
-            AtomicReference<Position2> next = new AtomicReference<>(pos);
-            Spiraler s = new Spiraler(100000, 100000, (x, z) -> next.set(new Position2(x, z)));
-            s.setOffset(pos.getX(), pos.getZ());
-            s.next();
-            while (!found.get() && !stop.get() && px.getMilliseconds() < timeout) {
-                BurstExecutor e = burst.burst(tc);
+                    for (int i = 0; i < tc; i++) {
+                        Position2 p = next.get();
+                        s.next();
+                        e.queue(() -> {
+                            if (found.get() || stop.get() || engine.isClosing()) {
+                                return;
+                            }
+                            if (matches(engine, p)) {
+                                foundPos.compareAndSet(null, p);
+                                found.set(true);
+                            }
+                            searched.incrementAndGet();
+                        });
+                    }
 
-                for (int i = 0; i < tc; i++) {
-                    Position2 p = next.get();
-                    s.next();
-                    e.queue(() -> {
-                        if (found.get()) {
-                            return;
-                        }
-                        if (matches(engine, p)) {
-                            foundPos.compareAndSet(null, p);
-                            found.set(true);
-                        }
-                        searched.incrementAndGet();
-                    });
+                    e.complete();
+                    checks.accept(searched.get());
                 }
 
-                e.complete();
-                checks.accept(searched.get());
+                if (found.get() && foundPos.get() != null) {
+                    return foundPos.get();
+                }
+
+                return null;
             }
-
-            LocatorCanceller.cancel = null;
-
-            if (found.get() && foundPos.get() != null) {
-                return foundPos.get();
-            }
-
-            return null;
         });
+        return LocatorCanceller.requestScoped(search, stop);
     }
 }

core/src/main/java/art/arcane/iris/engine/framework/LocatorCanceller.java

@@ -18,6 +18,49 @@
 
 package art.arcane.iris.engine.framework;
 
-public class LocatorCanceller {
+import java.util.Objects;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public final class LocatorCanceller {
     protected static Runnable cancel = null;
+
+    private LocatorCanceller() {
+    }
+
+    static <T> CompletableFuture<T> requestScoped(CompletableFuture<T> future, AtomicBoolean stop) {
+        return new RequestFuture<>(Objects.requireNonNull(future), Objects.requireNonNull(stop));
+    }
+
+    private static final class RequestFuture<T> extends CompletableFuture<T> {
+        private final CompletableFuture<T> delegate;
+        private final AtomicBoolean stop;
+
+        private RequestFuture(CompletableFuture<T> delegate, AtomicBoolean stop) {
+            this.delegate = delegate;
+            this.stop = stop;
+            delegate.whenComplete((value, exception) -> {
+                if (isDone()) {
+                    return;
+                }
+                if (exception == null) {
+                    complete(value);
+                } else {
+                    completeExceptionally(exception);
+                }
+            });
+        }
+
+        @Override
+        public boolean cancel(boolean mayInterruptIfRunning) {
+            if (isDone()) {
+                return false;
+            }
+
+            stop.set(true);
+            boolean cancelled = super.cancel(mayInterruptIfRunning);
+            delegate.cancel(mayInterruptIfRunning);
+            return cancelled;
+        }
+    }
 }