CrantEngine Tweak and a bit more.

- Fixed CE support
- Added some checks for things like paint and so on in the 3d Generator.

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

@@ -8,6 +8,7 @@ import java.util.function.LongPredicate;
 import art.arcane.iris.engine.DimensionStackContext;
 import art.arcane.iris.engine.DimensionStackLayout;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.EngineLifecycleTasks;
 import art.arcane.iris.engine.framework.GenerationSessionException;
 import art.arcane.iris.engine.framework.GenerationSessionLease;
 import art.arcane.iris.engine.framework.IrisStructureLocator;
@@ -930,6 +931,13 @@ public class IrisChunkGenerator extends CustomChunkGenerator implements LongPred
 
     @Override
     public WeightedList<MobSpawnSettings.SpawnerData> getMobsAt(Holder<Biome> holder, StructureManager structuremanager, MobCategory enumcreaturetype, BlockPos blockposition) {
+        return EngineLifecycleTasks.call(engine, "bukkit_nms_mob_spawns",
+                () -> getAdmittedMobsAt(holder, structuremanager, enumcreaturetype, blockposition),
+                WeightedList.of(List.of()));
+    }
+
+    private WeightedList<MobSpawnSettings.SpawnerData> getAdmittedMobsAt(
+            Holder<Biome> holder, StructureManager structuremanager, MobCategory enumcreaturetype, BlockPos blockposition) {
         NativeBiomeSpawnSelection selection = NativeBiomeSpawnSelection.at(
                 engine, blockposition.getX(), blockposition.getY(), blockposition.getZ(),
                 holder.unwrapKey().map(key -> key.identifier().toString()).orElse(""));
@@ -937,9 +945,7 @@ public class IrisChunkGenerator extends CustomChunkGenerator implements LongPred
             return WeightedList.of(List.of());
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope route = openHistoryCoordinateScope(
-                     blockposition.getX(), blockposition.getZ(), "bukkit_nms_mob_spawns");
-             GenerationSessionLease lease = requireGenerationLease("bukkit_nms_mob_spawns");
-             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+                     blockposition.getX(), blockposition.getZ(), "bukkit_nms_mob_spawns")) {
             return getMobsAtWithActiveRuntime(holder, structuremanager, enumcreaturetype, blockposition, selection);
         }
     }

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

@@ -3,13 +3,16 @@ package art.arcane.iris.core.nms.v26_2_R1;
 import art.arcane.iris.engine.history.NativeTerrainReceipt;
 import art.arcane.iris.engine.history.SavedTerrainChunk;
 import art.arcane.iris.util.common.scheduling.J;
+import ca.spottedleaf.concurrentutil.util.Priority;
 import ca.spottedleaf.moonrise.common.PlatformHooks;
 import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
 import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.NewChunkHolder;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.NbtIo;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.storage.SerializableChunkData;
 import org.bukkit.World;
@@ -18,12 +21,17 @@ import org.bukkit.craftbukkit.CraftWorld;
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.LockSupport;
 
 final class NmsSavedTerrainCapture {
+    private static final long WRITE_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(30L);
+
     private NmsSavedTerrainCapture() {
     }
 
@@ -53,9 +61,12 @@ final class NmsSavedTerrainCapture {
         });
         return snapshot.thenApplyAsync(data -> {
             try {
+                Checkpoint checkpoint = checkpoint(chunkX, chunkZ, data);
+                awaitWrite(level, checkpoint.chunk(), System.nanoTime() + WRITE_TIMEOUT_NANOS);
                 if (data == null) {
                     return SavedTerrainChunk.read(world.getWorldFolder().toPath(), chunkX, chunkZ, minimumY, height);
                 }
+                verifyCheckpoint(world.getWorldFolder().toPath(), checkpoint);
                 ByteArrayOutputStream bytes = new ByteArrayOutputStream();
                 try (DataOutputStream output = new DataOutputStream(bytes)) {
                     NbtIo.write(data, output);
@@ -77,17 +88,8 @@ final class NmsSavedTerrainCapture {
             J.runRegionFuture(world, holder.chunkX, holder.chunkZ, () -> {
                 try {
                     ChunkAccess chunk = holder.getCurrentChunk();
-                    if (chunk == null || !chunk.isUnsaved()) {
-                        saved.complete(null);
-                        return;
-                    }
-                    CompoundTag data = saveSnapshot(level, chunk);
-                    byte[] receipt = data.getCompound("ChunkBukkitValues")
-                            .flatMap(values -> values.getByteArray(NativeTerrainReceipt.NBT_KEY)).orElse(null);
-                    saved.complete(new Checkpoint(holder.chunkX, holder.chunkZ,
-                            BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getPersistedStatus()).toString(), receipt,
-                            data.getCompound("ChunkBukkitValues").map(values -> values.getLongOr(
-                                    NativeTerrainReceipt.STRUCTURE_ACTIVATION_KEY, 0)).orElse(0L)));
+                    saved.complete(checkpoint(holder.chunkX, holder.chunkZ,
+                            chunk != null && chunk.isUnsaved() ? saveSnapshot(level, chunk) : null));
                 } catch (Throwable failure) {
                     saved.completeExceptionally(failure);
                 }
@@ -99,22 +101,70 @@ final class NmsSavedTerrainCapture {
         }
         return CompletableFuture.allOf(saves.toArray(CompletableFuture[]::new)).thenRunAsync(() -> {
             try {
-                MoonriseRegionFileIO.flush(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA);
-                MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA);
+                List<Checkpoint> checkpoints = new ArrayList<>(saves.size());
                 for (CompletableFuture<Checkpoint> future : saves) {
-                    Checkpoint saved = future.join();
-                    if (saved == null) {
-                        continue;
-                    }
-                    SavedTerrainChunk.verifyCheckpoint(world.getWorldFolder().toPath(), saved.chunkX(), saved.chunkZ(),
-                            saved.status(), saved.receipt(), saved.structureActivation());
+                    checkpoints.add(future.join());
                 }
+                finishCheckpoint(level, world.getWorldFolder().toPath(), checkpoints);
             } catch (IOException failure) {
                 throw new CompletionException(failure);
             }
         });
     }
 
+    static void finishCheckpoint(ServerLevel level, Path worldFolder, List<Checkpoint> checkpoints) throws IOException {
+        long deadline = System.nanoTime() + WRITE_TIMEOUT_NANOS;
+        for (Checkpoint checkpoint : checkpoints) {
+            awaitWrite(level, checkpoint.chunk(), deadline);
+        }
+        MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA);
+        for (Checkpoint checkpoint : checkpoints) {
+            verifyCheckpoint(worldFolder, checkpoint);
+        }
+    }
+
+    static Checkpoint checkpoint(int chunkX, int chunkZ, CompoundTag data) {
+        if (data == null) {
+            return new Checkpoint(new ChunkPos(chunkX, chunkZ), null);
+        }
+        byte[] receipt = data.getCompound("ChunkBukkitValues")
+                .flatMap(values -> values.getByteArray(NativeTerrainReceipt.NBT_KEY)).orElse(null);
+        long structureActivation = data.getCompound("ChunkBukkitValues").map(values -> values.getLongOr(
+                NativeTerrainReceipt.STRUCTURE_ACTIVATION_KEY, 0)).orElse(0L);
+        return new Checkpoint(new ChunkPos(chunkX, chunkZ), new Verification(
+                data.getStringOr("Status", ""), receipt, structureActivation));
+    }
+
+    private static void verifyCheckpoint(Path worldFolder, Checkpoint checkpoint) throws IOException {
+        Verification expected = checkpoint.verification();
+        if (expected == null) {
+            return;
+        }
+        SavedTerrainChunk.verifyCheckpoint(worldFolder, checkpoint.chunk().x(), checkpoint.chunk().z(),
+                expected.status(), expected.receipt(), expected.structureActivation());
+    }
+
+    static void awaitWrite(ServerLevel level, ChunkPos chunk, long deadlineNanos) throws IOException {
+        ChunkTaskScheduler scheduler = level.moonrise$getChunkTaskScheduler();
+        while (true) {
+            if (Thread.currentThread().isInterrupted()) {
+                throw new IOException("Interrupted while saving terrain checkpoint chunk " + chunk);
+            }
+            if (System.nanoTime() - deadlineNanos >= 0L) {
+                throw new IOException("Timed out saving terrain checkpoint chunk " + chunk);
+            }
+            if (MoonriseRegionFileIO.getPriority(level, chunk.x(), chunk.z(),
+                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA) == Priority.COMPLETING) {
+                return;
+            }
+            boolean helped = scheduler.saveExecutor.executeTask();
+            helped |= scheduler.compressionExecutor.executeTask();
+            if (!helped) {
+                LockSupport.parkNanos(1_000_000L);
+            }
+        }
+    }
+
     private static CompoundTag saveSnapshot(ServerLevel level, ChunkAccess chunk) {
         SerializableChunkData snapshot = SerializableChunkData.copyOf(level, chunk);
         PlatformHooks.get().chunkSyncSave(level, chunk, snapshot);
@@ -124,6 +174,9 @@ final class NmsSavedTerrainCapture {
         return data;
     }
 
-    private record Checkpoint(int chunkX, int chunkZ, String status, byte[] receipt, long structureActivation) {
+    record Checkpoint(ChunkPos chunk, Verification verification) {
+    }
+
+    record Verification(String status, byte[] receipt, long structureActivation) {
     }
 }

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

@@ -0,0 +1,144 @@
+package art.arcane.iris.core.nms.v26_2_R1;
+
+import art.arcane.iris.engine.IrisEngine;
+import art.arcane.iris.engine.framework.GenerationSessionManager;
+import art.arcane.iris.engine.framework.GenerationTransitionGate;
+import art.arcane.iris.engine.history.GenerationHistoryRuntimeRouter;
+import art.arcane.iris.engine.history.NativeBiomeSpawnSelection;
+import art.arcane.iris.engine.history.SavedBiomeRuntime;
+import art.arcane.iris.util.project.context.IrisContext;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.random.WeightedList;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class IrisChunkGeneratorSpawnAdmissionTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void tickSpawnQueryLeavesOwnerThreadAvailableForBoundaryCheckpoint() throws Exception {
+        Fixture fixture = new Fixture();
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        ExecutorService reloader = Executors.newSingleThreadExecutor();
+        AtomicInteger snapshots = new AtomicInteger();
+        long previousSession = fixture.sessions.currentSessionId();
+        try {
+            assertSame(fixture.expected, owner.submit(fixture::query).get(2L, TimeUnit.SECONDS));
+            assertEquals(previousSession, fixture.readSession.get());
+            CompletableFuture<Void> cutover = CompletableFuture.runAsync(() -> {
+                try (GenerationTransitionGate.Transition ignored = fixture.sessions.transitionGate().beginTransition(2_000L)) {
+                    fixture.sessions.sealAndAwait("Studio generation cutover", 2_000L);
+                    Future<?> query = owner.submit(() -> {
+                        assertTrue(fixture.query().isEmpty());
+                        assertNull(IrisContext.get());
+                    });
+                    owner.submit(snapshots::incrementAndGet).get(2L, TimeUnit.SECONDS);
+                    query.get(2L, TimeUnit.SECONDS);
+                    assertEquals(1, fixture.savedReads.get());
+                    assertEquals(1, fixture.routes.get());
+                    fixture.sessions.activateNextSession();
+                } catch (Exception failure) {
+                    throw new IllegalStateException(failure);
+                }
+            }, reloader);
+
+            cutover.get(3L, TimeUnit.SECONDS);
+            assertEquals(1, snapshots.get());
+            assertEquals(0, fixture.sessions.activeLeases());
+            assertSame(fixture.expected, owner.submit(fixture::query).get(2L, TimeUnit.SECONDS));
+            assertEquals(fixture.sessions.currentSessionId(), fixture.readSession.get());
+            assertTrue(fixture.readSession.get() > previousSession);
+            assertEquals(2, fixture.savedReads.get());
+            assertEquals(2, fixture.routes.get());
+            assertEquals(0, fixture.sessions.activeLeases());
+        } finally {
+            owner.shutdownNow();
+            reloader.shutdownNow();
+            assertTrue(owner.awaitTermination(2L, TimeUnit.SECONDS));
+            assertTrue(reloader.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
+    private static void setField(IrisChunkGenerator generator, String name, Object value) throws Exception {
+        Field field = IrisChunkGenerator.class.getDeclaredField(name);
+        field.setAccessible(true);
+        field.set(generator, value);
+    }
+
+    private static final class Fixture {
+        private final GenerationSessionManager sessions = new GenerationSessionManager(true);
+        private final IrisEngine engine = mock(IrisEngine.class);
+        private final IrisChunkGenerator generator = mock(IrisChunkGenerator.class, CALLS_REAL_METHODS);
+        private final Holder<Biome> biome = Holder.direct(mock(Biome.class));
+        private final StructureManager structures = mock(StructureManager.class);
+        private final WeightedList<MobSpawnSettings.SpawnerData> expected = mock(WeightedList.class);
+        private final AtomicInteger savedReads = new AtomicInteger();
+        private final AtomicInteger routes = new AtomicInteger();
+        private final AtomicLong readSession = new AtomicLong();
+
+        private Fixture() throws Exception {
+            GenerationHistoryRuntimeRouter router = mock(GenerationHistoryRuntimeRouter.class);
+            SavedBiomeRuntime saved = mock(SavedBiomeRuntime.class);
+            ChunkGenerator delegate = mock(ChunkGenerator.class);
+            CustomBiomeSource source = mock(CustomBiomeSource.class);
+            when(engine.getGenerationSessions()).thenReturn(sessions);
+            when(engine.getGenerationHistoryRuntimeRouter()).thenReturn(Optional.of(router));
+            when(router.biomes()).thenReturn(saved);
+            when(saved.nativeSpawnSelection(0, 64, 0, "")).thenAnswer(invocation -> {
+                assertAdmitted();
+                savedReads.incrementAndGet();
+                return new NativeBiomeSpawnSelection(NativeBiomeSpawnSelection.Mode.RETAINED, "minecraft:plains");
+            });
+            when(engine.openGenerationHistoryCoordinateScope(0, 0)).thenAnswer(invocation -> {
+                assertAdmitted();
+                routes.incrementAndGet();
+                return null;
+            });
+            when(delegate.getMobsAt(biome, structures, MobCategory.MONSTER, new BlockPos(0, 64, 0)))
+                    .thenReturn(expected);
+            setField(generator, "engine", engine);
+            setField(generator, "delegate", delegate);
+            setField(generator, "customBiomeSource", source);
+        }
+
+        private WeightedList<MobSpawnSettings.SpawnerData> query() {
+            return generator.getMobsAt(biome, structures, MobCategory.MONSTER, new BlockPos(0, 64, 0));
+        }
+
+        private void assertAdmitted() {
+            assertEquals(1, sessions.activeLeases());
+            assertSame(engine, IrisContext.get().getEngine());
+            readSession.set(IrisContext.get().getGenerationSessionId());
+        }
+    }
+}

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

@@ -0,0 +1,114 @@
+package art.arcane.iris.core.nms.v26_2_R1;
+
+import art.arcane.iris.engine.history.SavedTerrainChunk;
+import ca.spottedleaf.concurrentutil.util.Priority;
+import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
+
+public class NmsSavedTerrainCheckpointTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void checkpointWaitsForDirtyAndUnloadedChunkWritesBeforeFlushAndVerification() throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        Path root = Path.of("checkpoint-world");
+        byte[] receipt = new byte[]{1, 2, 3};
+        NmsSavedTerrainCapture.Checkpoint saved = new NmsSavedTerrainCapture.Checkpoint(new ChunkPos(4, -5),
+                new NmsSavedTerrainCapture.Verification("minecraft:full", receipt, 7L));
+        NmsSavedTerrainCapture.Checkpoint unloaded = NmsSavedTerrainCapture.checkpoint(-8, 9, null);
+        Set<ChunkPos> completed = new HashSet<>();
+        AtomicBoolean flushed = new AtomicBoolean();
+        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
+             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
+            io.when(() -> MoonriseRegionFileIO.getPriority(level, 4, -5, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenAnswer(invocation -> {
+                        completed.add(saved.chunk());
+                        return Priority.COMPLETING;
+                    });
+            io.when(() -> MoonriseRegionFileIO.getPriority(level, -8, 9, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenAnswer(invocation -> {
+                        completed.add(unloaded.chunk());
+                        return Priority.COMPLETING;
+                    });
+            io.when(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenAnswer(invocation -> {
+                        assertEquals(Set.of(saved.chunk(), unloaded.chunk()), completed);
+                        flushed.set(true);
+                        return null;
+                    });
+            terrain.when(() -> SavedTerrainChunk.verifyCheckpoint(root, 4, -5, "minecraft:full", receipt, 7L))
+                    .thenAnswer(invocation -> {
+                        assertTrue(flushed.get());
+                        return null;
+                    });
+
+            NmsSavedTerrainCapture.finishCheckpoint(level, root, List.of(saved, unloaded));
+
+            terrain.verify(() -> SavedTerrainChunk.verifyCheckpoint(root, 4, -5, "minecraft:full", receipt, 7L));
+            io.verify(() -> MoonriseRegionFileIO.flush(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), never());
+            io.verify(() -> MoonriseRegionFileIO.getPriority(level, 100, 100, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), never());
+            terrain.verifyNoMoreInteractions();
+        }
+    }
+
+    @Test
+    public void storageFlushFailureCannotCompleteTheCheckpoint() throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        IOException failure = new IOException("storage flush failed");
+        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
+             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
+            io.when(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenThrow(failure);
+
+            assertSame(failure, assertThrows(IOException.class,
+                    () -> NmsSavedTerrainCapture.finishCheckpoint(level, Path.of("checkpoint-world"), List.of())));
+            terrain.verifyNoInteractions();
+        }
+    }
+
+    @Test
+    public void persistedReceiptMismatchCannotCompleteTheCheckpoint() throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        Path root = Path.of("checkpoint-world");
+        byte[] receipt = new byte[]{4, 5};
+        IOException failure = new IOException("saved terrain receipt mismatch");
+        NmsSavedTerrainCapture.Checkpoint saved = new NmsSavedTerrainCapture.Checkpoint(new ChunkPos(1, 2),
+                new NmsSavedTerrainCapture.Verification("minecraft:noise", receipt, 3L));
+        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
+             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
+            io.when(() -> MoonriseRegionFileIO.getPriority(level, 1, 2, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenReturn(Priority.COMPLETING);
+            terrain.when(() -> SavedTerrainChunk.verifyCheckpoint(root, 1, 2, "minecraft:noise", receipt, 3L))
+                    .thenThrow(failure);
+
+            assertSame(failure, assertThrows(IOException.class,
+                    () -> NmsSavedTerrainCapture.finishCheckpoint(level, root, List.of(saved))));
+            io.verify(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA));
+        }
+    }
+}

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

@@ -0,0 +1,135 @@
+package art.arcane.iris.core.nms.v26_2_R1;
+
+import ca.spottedleaf.concurrentutil.executor.thread.BalancedPrioritisedThreadPool;
+import ca.spottedleaf.concurrentutil.util.Priority;
+import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class NmsSavedTerrainWriteBarrierTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void checkpointHelpsSaveAndCompressionWhileNativeGenerationOccupiesTheWorker() throws Exception {
+        BalancedPrioritisedThreadPool pool = new BalancedPrioritisedThreadPool(
+                TimeUnit.MILLISECONDS.toNanos(1), Executors.defaultThreadFactory());
+        BalancedPrioritisedThreadPool.OrderedStreamGroup group = pool.createOrderedStreamGroup();
+        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue generation = group.createExecutor();
+        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue saves = group.createExecutor();
+        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue compression = group.createExecutor();
+        ServerLevel level = level(saves, compression);
+        ChunkPos chunk = new ChunkPos(4, -9);
+        CountDownLatch generationEntered = new CountDownLatch(1);
+        CountDownLatch releaseGeneration = new CountDownLatch(1);
+        AtomicBoolean pendingWrite = new AtomicBoolean(true);
+        AtomicInteger serialized = new AtomicInteger();
+        AtomicInteger compressed = new AtomicInteger();
+        AtomicReference<Thread> saveThread = new AtomicReference<>();
+        AtomicReference<Thread> compressionThread = new AtomicReference<>();
+        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class)) {
+            io.when(() -> MoonriseRegionFileIO.getPriority(level, chunk.x(), chunk.z(),
+                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
+                    .thenAnswer(invocation -> pendingWrite.get() ? Priority.NORMAL : Priority.COMPLETING);
+            generation.queueTask(() -> {
+                generationEntered.countDown();
+                try {
+                    assertTrue(releaseGeneration.await(5, TimeUnit.SECONDS));
+                } catch (InterruptedException interruption) {
+                    Thread.currentThread().interrupt();
+                    throw new AssertionError(interruption);
+                }
+            });
+            pool.adjustThreadCount(1);
+            assertTrue(generationEntered.await(5, TimeUnit.SECONDS));
+            saves.queueTask(() -> {
+                saveThread.set(Thread.currentThread());
+                serialized.incrementAndGet();
+                compression.queueTask(() -> {
+                    compressionThread.set(Thread.currentThread());
+                    compressed.incrementAndGet();
+                    pendingWrite.set(false);
+                });
+            });
+
+            NmsSavedTerrainCapture.awaitWrite(level, chunk, System.nanoTime() + TimeUnit.SECONDS.toNanos(3));
+
+            assertEquals(1L, releaseGeneration.getCount());
+            assertEquals(1, serialized.get());
+            assertEquals(1, compressed.get());
+            assertFalse(pendingWrite.get());
+            assertSame(Thread.currentThread(), saveThread.get());
+            assertSame(Thread.currentThread(), compressionThread.get());
+        } finally {
+            releaseGeneration.countDown();
+            pool.halt(true);
+            assertTrue(pool.joinInterruptable(5_000));
+        }
+    }
+
+    @Test
+    public void waitingForNativeWriteHonorsTheSharedDeadline() throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        ChunkPos chunk = new ChunkPos(2, 3);
+        IOException failure = assertThrows(IOException.class,
+                () -> NmsSavedTerrainCapture.awaitWrite(level, chunk, System.nanoTime() - 1L));
+        assertTrue(failure.getMessage().contains("Timed out"));
+    }
+
+    @Test
+    public void interruptedNativeWriteWaitPreservesInterruption() throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        ChunkPos chunk = new ChunkPos(2, 3);
+        Thread.currentThread().interrupt();
+        try {
+            IOException failure = assertThrows(IOException.class,
+                    () -> NmsSavedTerrainCapture.awaitWrite(level, chunk,
+                            System.nanoTime() + TimeUnit.SECONDS.toNanos(3)));
+            assertTrue(failure.getMessage().contains("Interrupted"));
+            assertTrue(Thread.currentThread().isInterrupted());
+        } finally {
+            Thread.interrupted();
+        }
+    }
+
+    private static ServerLevel level(BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue saves,
+                                     BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue compression) throws Exception {
+        ServerLevel level = mock(ServerLevel.class);
+        ChunkTaskScheduler scheduler = mock(ChunkTaskScheduler.class);
+        Field savesField = ChunkTaskScheduler.class.getField("saveExecutor");
+        Field compressionField = ChunkTaskScheduler.class.getField("compressionExecutor");
+        savesField.setAccessible(true);
+        compressionField.setAccessible(true);
+        savesField.set(scheduler, saves);
+        compressionField.set(scheduler, compression);
+        when(level.moonrise$getChunkTaskScheduler()).thenReturn(scheduler);
+        return level;
+    }
+}

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

@@ -26,12 +26,16 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CopyOnWriteArraySet;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.ForkJoinPool;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.LockSupport;
 import java.util.function.IntConsumer;
 
@@ -291,6 +295,87 @@ public class NativeStructureVolumeIndexTest {
         }
     }
 
+    @Test
+    public void contendedNativeWindowsAllowQueuedTerrainWorkToRun() throws Exception {
+        assertQueuedTerrainCanComplete(false);
+    }
+
+    @Test
+    public void interruptedNativeWindowWaitStillAcquiresAndReleasesOnce() throws Exception {
+        assertQueuedTerrainCanComplete(true);
+    }
+
+    private static void assertQueuedTerrainCanComplete(boolean interruptWaiter) throws Exception {
+        CountDownLatch ownerEntered = new CountDownLatch(1);
+        CompletableFuture<Void> terrain = new CompletableFuture<>();
+        AtomicBoolean firstOrigin = new AtomicBoolean(true);
+        AtomicBoolean interruptedAfterQuery = new AtomicBoolean();
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting((engine, chunkX, chunkZ) -> {
+            if (firstOrigin.compareAndSet(true, false)) {
+                ownerEntered.countDown();
+                terrain.join();
+            }
+            return new KList<>(new NativeStructureVolume(chunkX + ":" + chunkZ,
+                    -256, 0, -256, 256, 100, 256));
+        });
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        ForkJoinPool workers = new ForkJoinPool(2);
+        AtomicReference<Thread> firstWaiter = new AtomicReference<>();
+        AtomicReference<Thread> secondWaiter = new AtomicReference<>();
+        try {
+            Future<KList<NativeStructureVolume>> original = owner.submit(
+                    () -> index.resolve(null, 0, 0, 15, 15));
+            assertTrue(ownerEntered.await(5, TimeUnit.SECONDS));
+            Future<KList<NativeStructureVolume>> adjacent = workers.submit(() -> {
+                firstWaiter.set(Thread.currentThread());
+                KList<NativeStructureVolume> result = index.resolve(null, 16, 0, 31, 15);
+                interruptedAfterQuery.set(Thread.currentThread().isInterrupted());
+                return result;
+            });
+            Future<KList<NativeStructureVolume>> next = workers.submit(() -> {
+                secondWaiter.set(Thread.currentThread());
+                return index.resolve(null, 32, 0, 47, 15);
+            });
+            awaitOriginWindowWaiter(firstWaiter);
+            awaitOriginWindowWaiter(secondWaiter);
+            if (interruptWaiter) {
+                firstWaiter.get().interrupt();
+            }
+
+            Future<?> terrainTask = workers.submit(() -> terrain.complete(null));
+            terrainTask.get(3, TimeUnit.SECONDS);
+            assertEquals(289, original.get(3, TimeUnit.SECONDS).size());
+            KList<NativeStructureVolume> adjacentVolumes = adjacent.get(3, TimeUnit.SECONDS);
+            assertEquals(289, adjacentVolumes.size());
+            assertEquals(adjacentVolumes, index.resolve(null, 16, 0, 31, 15));
+            assertEquals(289, next.get(3, TimeUnit.SECONDS).size());
+            assertEquals(interruptWaiter, interruptedAfterQuery.get());
+        } finally {
+            terrain.complete(null);
+            owner.shutdownNow();
+            workers.shutdownNow();
+            assertTrue(owner.awaitTermination(5, TimeUnit.SECONDS));
+            assertTrue(workers.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    private static void awaitOriginWindowWaiter(AtomicReference<Thread> reference) {
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(5);
+        while (System.nanoTime() < deadline) {
+            Thread thread = reference.get();
+            if (thread != null && thread.getState() == Thread.State.WAITING) {
+                for (StackTraceElement frame : thread.getStackTrace()) {
+                    if (frame.getClassName().equals(NativeStructureVolumeIndex.class.getName())
+                            && frame.getMethodName().equals("lockOriginWindow")) {
+                        return;
+                    }
+                }
+            }
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(1));
+        }
+        throw new AssertionError("Native query did not wait for the occupied origin window");
+    }
+
     @Test
     public void distantColdQueriesCanResolveOriginsConcurrently() throws Exception {
         BlockingResolver resolver = new BlockingResolver();

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

@@ -26,6 +26,7 @@ import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.runtime.ObjectStudioActivation;
 import art.arcane.iris.core.runtime.StudioOpenCoordinator;
 import art.arcane.iris.core.runtime.WorldRuntimeControlService;
+import art.arcane.iris.core.service.ExternalDataSVC;
 import art.arcane.iris.core.service.ObjectSVC;
 import art.arcane.iris.core.service.StudioSVC;
 import art.arcane.iris.core.service.WandSVC;
@@ -41,6 +42,8 @@ import art.arcane.iris.engine.object.IrisObjectRotation;
 import art.arcane.iris.engine.object.IrisObjectScale;
 import art.arcane.iris.engine.object.TileData;
 import art.arcane.iris.platform.bukkit.BukkitBlockState;
+import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.volmlib.util.data.Cuboid;
 import art.arcane.iris.util.common.data.IrisCustomData;
@@ -223,11 +226,19 @@ public class CommandObject implements DirectorExecutor {
                 //Prevent blocks being set in or bellow bedrock
                 if (y <= world.getMinHeight() || block.getType() == Material.BEDROCK) return;
 
-                futureBlockChanges.putIfAbsent(block, block.getBlockData());
+                ExternalDataSVC external = IrisServices.getOrNull(ExternalDataSVC.class);
+                futureBlockChanges.computeIfAbsent(block, target -> {
+                    BlockData previous = target.getBlockData();
+                    return external == null ? previous : external.captureBlockData(previous);
+                });
 
                 if (d instanceof IrisCustomData data) {
+                    if (external != null && external.placeBlock(block, data.getCustom())) {
+                        return;
+                    }
                     block.setBlockData(data.getBase(), false);
-                    Iris.warn("Tried to place custom block at " + x + ", " + y + ", " + z + " which is not supported!");
+                    IrisLogging.warnOnce("object-paste:external:" + data.getCustom(),
+                            "Direct placement of %s is unavailable; only its base block was placed.", data.getCustom());
                 } else block.setBlockData(d, false);
             }
 

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

@@ -53,11 +53,11 @@ dependencies:
       required: false
       join-classpath: false
     MythicLib:
-      load: BEFORE
+      load: OMIT
       required: false
       join-classpath: true
     MMOItems:
-      load: BEFORE
+      load: OMIT
       required: false
       join-classpath: true
     eco:
@@ -69,11 +69,11 @@ dependencies:
       required: false
       join-classpath: true
     MythicMobs:
-      load: BEFORE
+      load: OMIT
       required: false
       join-classpath: true
     MythicCrucible:
-      load: BEFORE
+      load: OMIT
       required: false
       join-classpath: true
     KGenerators:

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

@@ -11,12 +11,8 @@ softdepend:
   - ItemsAdder
   - SCore
   - ExecutableItems
-  - MythicLib
-  - MMOItems
   - eco
   - EcoItems
-  - MythicMobs
-  - MythicCrucible
   - KGenerators
   - WorldEdit
 loadbefore: [ Multiverse-Core ]

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

@@ -41,8 +41,11 @@ public class PaperPluginMetadataTest {
     private static final List<String> JOINED_PLUGIN_IDS = OPTIONAL_PLUGIN_IDS.stream()
             .filter(pluginId -> !"ExecutableItems".equals(pluginId) && !"Multiverse-Core".equals(pluginId))
             .toList();
+    private static final List<String> UNORDERED_PLUGIN_IDS = List.of(
+            "MythicLib", "MMOItems", "MythicMobs", "MythicCrucible");
     private static final List<String> BUKKIT_SOFT_DEPEND_IDS = OPTIONAL_PLUGIN_IDS.stream()
             .filter(pluginId -> !"Multiverse-Core".equals(pluginId))
+            .filter(pluginId -> !UNORDERED_PLUGIN_IDS.contains(pluginId))
             .toList();
 
     @Test
@@ -72,7 +75,8 @@ public class PaperPluginMetadataTest {
                 + "    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)));
+            String loadOrder = UNORDERED_PLUGIN_IDS.contains(pluginId) ? "OMIT" : "BEFORE";
+            assertTrue(metadata.contains(optionalDependencyBlock(pluginId, loadOrder, true)));
         }
         assertTrue(metadata.contains(optionalDependencyBlock("ExecutableItems", "BEFORE", false)));
         assertTrue(metadata.contains(optionalDependencyBlock("Multiverse-Core", "AFTER", true)));

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

@@ -0,0 +1,80 @@
+package art.arcane.iris.core.commands;
+
+import art.arcane.iris.core.link.Identifier;
+import art.arcane.iris.core.service.ExternalDataSVC;
+import art.arcane.iris.engine.object.IObjectPlacer;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.util.common.data.IrisCustomData;
+import org.bukkit.Material;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.data.BlockData;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertSame;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class CommandObjectCustomBlockPlacementTest {
+    @Test
+    public void customPasteUsesProviderAndKeepsOriginalSemanticUndoState() {
+        World world = mock(World.class);
+        Block target = mock(Block.class);
+        when(world.getBlockAt(7, 80, -9)).thenReturn(target);
+        when(target.getType()).thenReturn(Material.STONE);
+        BlockData previous = mock(BlockData.class);
+        when(target.getBlockData()).thenReturn(previous);
+        BlockData previousCustom = IrisCustomData.of(previous, new Identifier("craftengine", "test/lamp[lit=false]"));
+        Identifier id = new Identifier("craftengine", "test/lamp[lit=true]");
+        BlockData base = mock(BlockData.class);
+        PlatformBlockState state = mock(PlatformBlockState.class);
+        when(state.nativeHandle()).thenReturn(IrisCustomData.of(base, id));
+        ExternalDataSVC external = mock(ExternalDataSVC.class);
+        when(external.captureBlockData(previous)).thenReturn(previousCustom);
+        when(external.placeBlock(target, id)).thenReturn(true);
+        Map<Block, BlockData> changes = new HashMap<>();
+        try (MockedStatic<IrisServices> services = mockStatic(IrisServices.class)) {
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(external);
+            IObjectPlacer placer = CommandObject.createPlacer(world, changes, null);
+
+            placer.set(7, 80, -9, state);
+            placer.set(7, 80, -9, state);
+
+            assertSame(previousCustom, changes.get(target));
+            verify(external).captureBlockData(previous);
+            verify(external, times(2)).placeBlock(target, id);
+            verify(target, times(0)).setBlockData(any(BlockData.class), anyBoolean());
+        }
+    }
+
+    @Test
+    public void unsupportedFurniturePreservesBaseOnlyPreview() {
+        World world = mock(World.class);
+        Block target = mock(Block.class);
+        when(world.getBlockAt(7, 80, -9)).thenReturn(target);
+        when(target.getType()).thenReturn(Material.STONE);
+        BlockData base = mock(BlockData.class);
+        Identifier id = new Identifier("craftengine", "test/chair[variant=alpha]");
+        PlatformBlockState state = mock(PlatformBlockState.class);
+        when(state.nativeHandle()).thenReturn(IrisCustomData.of(base, id));
+        ExternalDataSVC external = mock(ExternalDataSVC.class);
+        try (MockedStatic<IrisServices> services = mockStatic(IrisServices.class)) {
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(external);
+
+            CommandObject.createPlacer(world, new HashMap<>(), null).set(7, 80, -9, state);
+
+            verify(external).placeBlock(target, id);
+            verify(target).setBlockData(base, false);
+        }
+    }
+}

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

@@ -39,6 +39,9 @@ import java.util.Set;
 import java.util.WeakHashMap;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.IntBinaryOperator;
 import java.util.function.IntConsumer;
@@ -516,11 +519,30 @@ public final class NativeStructureVolumeIndex {
         long pending = stripeMask;
         while (pending != 0L) {
             int stripe = Long.numberOfTrailingZeros(pending);
-            originWindowStripes[stripe].lock();
+            lockOriginStripe(originWindowStripes[stripe]);
             pending &= pending - 1L;
         }
     }
 
+    private static void lockOriginStripe(ReentrantLock lock) {
+        if (lock.tryLock()) {
+            return;
+        }
+        if (!ForkJoinTask.inForkJoinPool()) {
+            lock.lock();
+            return;
+        }
+        OriginLockBlocker blocker = new OriginLockBlocker(lock);
+        try {
+            ForkJoinPool.managedBlock(blocker);
+        } catch (InterruptedException interruption) {
+            Thread.currentThread().interrupt();
+            blocker.block();
+        } catch (RejectedExecutionException exhaustedPool) {
+            blocker.block();
+        }
+    }
+
     private void unlockOriginWindow(long stripeMask) {
         long pending = stripeMask;
         while (pending != 0L) {
@@ -530,6 +552,32 @@ public final class NativeStructureVolumeIndex {
         }
     }
 
+    private static final class OriginLockBlocker implements ForkJoinPool.ManagedBlocker {
+        private final ReentrantLock lock;
+        private boolean acquired;
+
+        private OriginLockBlocker(ReentrantLock lock) {
+            this.lock = lock;
+        }
+
+        @Override
+        public boolean block() {
+            if (!acquired) {
+                lock.lock();
+                acquired = true;
+            }
+            return true;
+        }
+
+        @Override
+        public boolean isReleasable() {
+            if (!acquired) {
+                acquired = lock.tryLock();
+            }
+            return acquired;
+        }
+    }
+
     private static GenerationHistoryRuntimeRouter.CoordinateScope openHistoryCoordinateScope(
             Engine engine,
             int chunkX,

core/build.gradle

@@ -453,6 +453,18 @@ sourceSets {
 }
 
 dependencies {
+    externalProviderTestImplementation(libs.craftengine.core) {
+        transitive = false
+    }
+    externalProviderTestImplementation(libs.craftengine.bukkit) {
+        transitive = false
+    }
+    externalProviderTestImplementation('net.momirealms:sparrow-nbt:0.22')
+    externalProviderTestImplementation('net.momirealms:sparrow-util:0.121')
+    externalProviderTestImplementation('net.momirealms:sparrow-reflection:0.33')
+    externalProviderTestImplementation('net.momirealms:sparrow-yaml:1.0.18')
+    externalProviderTestImplementation('net.momirealms:antigrieflib:1.0.17')
+    externalProviderTestImplementation('org.incendo:cloud-core:2.0.0')
     externalProviderTestImplementation(libs.oraxen) {
         transitive = false
     }

core/src/externalProviderTest/java/art/arcane/iris/core/link/data/CraftEngineDataProviderTest.java

@@ -0,0 +1,371 @@
+package art.arcane.iris.core.link.data;
+
+import art.arcane.iris.core.link.Identifier;
+import art.arcane.iris.core.service.ExternalDataSVC;
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.SeedManager;
+import art.arcane.iris.platform.bukkit.BukkitBlockResolution;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.testsupport.BukkitTestServer;
+import art.arcane.iris.util.common.data.IrisCustomData;
+import art.arcane.iris.util.common.data.registry.RegistryUtil;
+import art.arcane.volmlib.util.collection.KMap;
+import net.momirealms.craftengine.bukkit.api.CraftEngineBlocks;
+import net.momirealms.craftengine.bukkit.api.CraftEngineFurniture;
+import net.momirealms.craftengine.bukkit.api.CraftEngineItems;
+import net.momirealms.craftengine.bukkit.api.event.CraftEngineReloadEvent;
+import net.momirealms.craftengine.bukkit.item.BukkitItemDefinition;
+import net.momirealms.craftengine.bukkit.plugin.BukkitCraftEngine;
+import net.momirealms.craftengine.core.block.BlockDefinition;
+import net.momirealms.craftengine.core.block.ImmutableBlockState;
+import net.momirealms.craftengine.core.block.property.BooleanProperty;
+import net.momirealms.craftengine.core.entity.furniture.FurnitureDefinition;
+import net.momirealms.craftengine.core.entity.furniture.FurnitureVariant;
+import net.momirealms.craftengine.core.registry.Holder;
+import net.momirealms.craftengine.core.util.Key;
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.block.Block;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.plugin.Plugin;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.List;
+import java.util.Map;
+import java.util.MissingResourceException;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class CraftEngineDataProviderTest {
+    @Test
+    public void startupWaitsForReloadEventAndEmptyLoadedRegistriesAreReady() {
+        CraftEngineDataProvider provider = spy(new CraftEngineDataProvider());
+        Plugin plugin = mock(Plugin.class);
+        doReturn(plugin).when(provider).getPlugin();
+        when(plugin.isEnabled()).thenReturn(true);
+        try (MockedStatic<BukkitCraftEngine> engine = mockStatic(BukkitCraftEngine.class);
+             MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class);
+             MockedStatic<CraftEngineItems> items = mockStatic(CraftEngineItems.class)) {
+            provider.init();
+
+            assertFalse(provider.isReady());
+            assertTrue(provider.getTypes(DataType.BLOCK).isEmpty());
+            assertFalse(provider.isValidProvider(new Identifier("test", "lamp"), DataType.BLOCK));
+            blocks.verifyNoInteractions();
+            furniture.verifyNoInteractions();
+            items.verifyNoInteractions();
+
+            provider.onReload(mock(CraftEngineReloadEvent.class));
+
+            assertTrue(provider.isReady());
+            when(plugin.isEnabled()).thenReturn(false);
+            assertFalse(provider.isReady());
+        }
+    }
+
+    @Test
+    public void lateInitializationUsesFullyLoadedFlagAndRefreshesExactClaims() {
+        CraftEngineDataProvider provider = new CraftEngineDataProvider();
+        BukkitCraftEngine plugin = mock(BukkitCraftEngine.class);
+        when(plugin.isFullyLoaded()).thenReturn(true);
+        Key oldKey = Key.of("test:old");
+        Key newKey = Key.of("test:new");
+        try (MockedStatic<BukkitCraftEngine> engine = mockStatic(BukkitCraftEngine.class);
+             MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class);
+             MockedStatic<CraftEngineItems> items = mockStatic(CraftEngineItems.class);
+             MockedStatic<IrisServices> services = mockStatic(IrisServices.class)) {
+            ExternalDataSVC service = mock(ExternalDataSVC.class);
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(service);
+            engine.when(BukkitCraftEngine::instance).thenReturn(plugin);
+            blocks.when(CraftEngineBlocks::loadedBlocks).thenReturn(Map.of(oldKey, mock(BlockDefinition.class)));
+            items.when(CraftEngineItems::loadedItems).thenReturn(Map.of(oldKey, mock(BukkitItemDefinition.class)));
+            provider.init();
+
+            assertTrue(provider.isValidProvider(new Identifier("test", "old"), DataType.BLOCK));
+            assertTrue(provider.isValidProvider(new Identifier("test", "old"), DataType.ITEM));
+            assertFalse(provider.isValidProvider(new Identifier("test", "missing"), DataType.ITEM));
+            assertFalse(provider.isValidProvider(new Identifier("test", "old"), DataType.ENTITY));
+
+            blocks.when(CraftEngineBlocks::loadedBlocks).thenReturn(Map.of());
+            items.when(CraftEngineItems::loadedItems).thenReturn(Map.of(newKey, mock(BukkitItemDefinition.class)));
+            furniture.when(CraftEngineFurniture::loadedFurniture).thenReturn(Map.of(newKey, mock(FurnitureDefinition.class)));
+            when(plugin.isFullyLoaded()).thenReturn(false);
+            when(plugin.isReloading()).thenReturn(true);
+            provider.onReload(mock(CraftEngineReloadEvent.class));
+
+            assertFalse(provider.isValidProvider(new Identifier("test", "old"), DataType.BLOCK));
+            assertFalse(provider.isValidProvider(new Identifier("test", "old"), DataType.ITEM));
+            assertEquals(Set.of(new Identifier("test", "new")), provider.getTypes(DataType.BLOCK));
+            assertEquals(Set.of(new Identifier("test", "new")), provider.getTypes(DataType.ITEM));
+            verify(service).notifyContentChanged();
+        }
+    }
+
+    @Test
+    public void blockPropertiesProduceNativeCarrierAndCanonicalIdentifier() {
+        Identifier id = new Identifier("test", "lamp");
+        BooleanProperty property = BooleanProperty.create("lit", false);
+        BlockDefinition definition = mock(BlockDefinition.class);
+        ImmutableBlockState initial = blockState(definition, "test:lamp[lit=false]");
+        ImmutableBlockState lit = blockState(definition, "test:lamp[lit=true]");
+        BlockData data = mock(BlockData.class);
+        when(definition.defaultState()).thenReturn(initial);
+        doReturn(property).when(definition).getProperty("lit");
+        when(initial.with(property, true)).thenReturn(lit);
+        KMap<String, String> properties = new KMap<>();
+        properties.put("lit", "true");
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class)) {
+            blocks.when(() -> CraftEngineBlocks.byId(Key.of("test:lamp"))).thenReturn(definition);
+            blocks.when(() -> CraftEngineBlocks.getBukkitBlockData(lit)).thenReturn(data);
+
+            IrisCustomData result = (IrisCustomData) new CraftEngineDataProvider().getBlockData(id, properties);
+
+            assertSame(data, result.getBase());
+            assertEquals(new Identifier("test", "lamp[lit=true]"), result.getCustom());
+            verify(initial).with(property, true);
+        }
+    }
+
+    @Test
+    public void unknownOrInvalidBlockPropertiesFailBeforeNativeConversion() {
+        Identifier id = new Identifier("test", "lamp");
+        BlockDefinition definition = mock(BlockDefinition.class);
+        ImmutableBlockState initial = blockState(definition, "test:lamp[lit=false]");
+        when(definition.defaultState()).thenReturn(initial);
+        doReturn(BooleanProperty.create("lit", false)).when(definition).getProperty("lit");
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class)) {
+            blocks.when(() -> CraftEngineBlocks.byId(Key.of("test:lamp"))).thenReturn(definition);
+            for (Map.Entry<String, String> entry : List.of(Map.entry("missing", "true"), Map.entry("lit", "yes"))) {
+                KMap<String, String> properties = new KMap<>();
+                properties.put(entry.getKey(), entry.getValue());
+                assertThrows(MissingResourceException.class, () -> new CraftEngineDataProvider().getBlockData(id, properties));
+            }
+            blocks.verify(() -> CraftEngineBlocks.getBukkitBlockData(any()), times(0));
+        }
+    }
+
+    @Test
+    public void reverseCaptureUsesSemanticStateInsteadOfSyntheticNativeName() {
+        BlockData nativeData = mock(BlockData.class);
+        when(nativeData.getAsString()).thenReturn("craftengine:custom_12");
+        ImmutableBlockState state = blockState(mock(BlockDefinition.class), "test:lamp[lit=true]");
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class)) {
+            blocks.when(() -> CraftEngineBlocks.getCustomBlockState(nativeData)).thenReturn(state);
+            CraftEngineDataProvider provider = new CraftEngineDataProvider();
+
+            assertEquals(new Identifier("test", "lamp[lit=true]"), provider.identifyBlock(nativeData).orElseThrow());
+            assertTrue(provider.identifyBlock(mock(BlockData.class)).isEmpty());
+        }
+    }
+
+    @Test
+    public void currentSyntheticSlotResolvesOnlyWhenBoundToCustomContent() {
+        CraftEngineDataProvider provider = new CraftEngineDataProvider();
+        Identifier id = new Identifier("craftengine", "custom_12");
+        BlockData data = mock(BlockData.class);
+        ImmutableBlockState state = blockState(mock(BlockDefinition.class), "test:lamp[lit=true]");
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+             MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class);
+             MockedStatic<CraftEngineItems> items = mockStatic(CraftEngineItems.class)) {
+            bukkit.when(() -> Bukkit.createBlockData("craftengine:custom_12")).thenReturn(data);
+            blocks.when(() -> CraftEngineBlocks.getCustomBlockState(data)).thenReturn(state);
+            blocks.when(() -> CraftEngineBlocks.getBukkitBlockData(state)).thenReturn(data);
+            provider.onReload(mock(CraftEngineReloadEvent.class));
+
+            assertTrue(provider.isValidProvider(id, DataType.BLOCK));
+            IrisCustomData result = (IrisCustomData) provider.getBlockData(id, new KMap<>());
+            assertEquals(new Identifier("test", "lamp[lit=true]"), result.getCustom());
+
+            blocks.when(() -> CraftEngineBlocks.getCustomBlockState(data)).thenReturn(null);
+            assertFalse(provider.isValidProvider(id, DataType.BLOCK));
+            assertThrows(MissingResourceException.class, () -> provider.getBlockData(id, new KMap<>()));
+            bukkit.when(() -> Bukkit.createBlockData("craftengine:custom_12")).thenThrow(new IllegalArgumentException("Unknown block"));
+            assertFalse(provider.isValidProvider(id, DataType.BLOCK));
+        }
+    }
+
+    @Test
+    public void deferredPlacementUsesCraftEngineAndAcceptsAlreadyMatchingState() {
+        Identifier id = new Identifier("test", "lamp");
+        BlockDefinition definition = mock(BlockDefinition.class);
+        ImmutableBlockState state = blockState(definition, "test:lamp");
+        when(definition.defaultState()).thenReturn(state);
+        Block block = mock(Block.class);
+        Location location = new Location(null, 17, 80, -12);
+        when(block.getLocation()).thenReturn(location);
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class)) {
+            blocks.when(() -> CraftEngineBlocks.byId(Key.of("test:lamp"))).thenReturn(definition);
+            blocks.when(() -> CraftEngineBlocks.getCustomBlockState(block)).thenReturn(state);
+
+            new CraftEngineDataProvider().processUpdate(mock(Engine.class), block, id);
+
+            blocks.verify(() -> CraftEngineBlocks.place(location, state, false));
+            blocks.when(() -> CraftEngineBlocks.getCustomBlockState(block)).thenReturn(null);
+            assertThrows(MissingResourceException.class, () -> new CraftEngineDataProvider().processUpdate(mock(Engine.class), block, id));
+        }
+    }
+
+    @Test
+    public void missingBlockAndFurnitureCannotBePlaced() {
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class)) {
+            assertThrows(MissingResourceException.class, () -> new CraftEngineDataProvider().processUpdate(
+                    mock(Engine.class), mock(Block.class), new Identifier("test", "missing")));
+        }
+    }
+
+    @Test
+    public void furnitureValidatesPropertiesAndStoresDeterministicDefaultVariant() {
+        BukkitTestServer.install();
+        FurnitureDefinition definition = furnitureDefinition();
+        Identifier id = new Identifier("test", "chair");
+        BlockData air = mock(BlockData.class);
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class);
+             MockedStatic<RegistryUtil> registry = materialRegistry();
+             MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            furniture.when(() -> CraftEngineFurniture.byId(Key.of("test:chair"))).thenReturn(definition);
+            resolution.when(BukkitBlockResolution::getAir).thenReturn(air);
+            CraftEngineDataProvider provider = new CraftEngineDataProvider();
+            IrisCustomData result = (IrisCustomData) provider.getBlockData(id, new KMap<>());
+
+            assertSame(air, result.getBase());
+            assertEquals("test:chair[variant=alpha]", result.getCustom().toString());
+            assertEquals("alpha", provider.getBlockProperties(id).stream()
+                    .filter(property -> property.name().equals("variant")).findFirst().orElseThrow().defaultValue());
+            for (Map.Entry<String, String> invalid : List.of(Map.entry("variant", "missing"), Map.entry("randomYaw", "yes"),
+                    Map.entry("randomPitch", "1"), Map.entry("yaw", "NaN"), Map.entry("yaw", "Infinity"),
+                    Map.entry("pitch", "360"), Map.entry("pitch", "-1"), Map.entry("yaw", "word"), Map.entry("unknown", "true"))) {
+                KMap<String, String> properties = new KMap<>();
+                properties.put(invalid.getKey(), invalid.getValue());
+                assertThrows(MissingResourceException.class, () -> provider.getBlockData(id, properties));
+            }
+        }
+    }
+
+    @Test
+    public void furniturePlacementUsesRepeatablePositionSeededRotation() {
+        FurnitureDefinition definition = furnitureDefinition();
+        Engine engine = mock(Engine.class);
+        SeedManager seeds = mock(SeedManager.class);
+        when(engine.getSeedManager()).thenReturn(seeds);
+        when(seeds.getSeed()).thenReturn(1234L);
+        Block block = mock(Block.class);
+        when(block.getX()).thenReturn(7);
+        when(block.getY()).thenReturn(80);
+        when(block.getZ()).thenReturn(-9);
+        when(block.getLocation()).thenAnswer(invocation -> new Location(null, 7, 80, -9));
+        Identifier id = new Identifier("test", "chair[randomYaw=true,randomPitch=true,variant=beta]");
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class)) {
+            furniture.when(() -> CraftEngineFurniture.byId(Key.of("test:chair"))).thenReturn(definition);
+            Location[] observed = new Location[2];
+            int[] count = new int[1];
+            furniture.when(() -> CraftEngineFurniture.place(any(Location.class), eq(definition), eq("beta"), eq(false)))
+                    .thenAnswer(invocation -> {
+                        observed[count[0]++] = invocation.getArgument(0, Location.class).clone();
+                        return null;
+                    });
+            CraftEngineDataProvider provider = new CraftEngineDataProvider();
+            assertThrows(MissingResourceException.class, () -> provider.processUpdate(engine, block, id));
+            assertThrows(MissingResourceException.class, () -> provider.processUpdate(engine, block, id));
+
+            assertEquals(observed[0], observed[1]);
+            assertTrue(observed[0].getYaw() >= 0 && observed[0].getYaw() < 360);
+            assertTrue(observed[0].getPitch() >= 0 && observed[0].getPitch() < 360);
+        }
+    }
+
+    @Test
+    public void itemsAreBuiltThroughCraftEngineAndMissingItemsFail() {
+        BukkitItemDefinition definition = mock(BukkitItemDefinition.class);
+        ItemStack stack = mock(ItemStack.class);
+        when(definition.buildBukkitItem()).thenReturn(stack);
+        try (MockedStatic<CraftEngineItems> items = mockStatic(CraftEngineItems.class)) {
+            items.when(() -> CraftEngineItems.byId(Key.of("test:lamp"))).thenReturn(definition);
+            CraftEngineDataProvider provider = new CraftEngineDataProvider();
+
+            assertSame(stack, provider.getItemStack(new Identifier("test", "lamp"), new KMap<>()));
+            assertThrows(MissingResourceException.class, () -> provider.getItemStack(new Identifier("test", "missing"), new KMap<>()));
+        }
+    }
+
+    @Test
+    public void directPlacementUsesCustomBlockPropertiesWithoutAnEngine() {
+        BlockDefinition definition = mock(BlockDefinition.class);
+        BooleanProperty property = BooleanProperty.create("lit", false);
+        ImmutableBlockState initial = blockState(definition, "test:lamp[lit=false]");
+        ImmutableBlockState lit = blockState(definition, "test:lamp[lit=true]");
+        when(definition.defaultState()).thenReturn(initial);
+        doReturn(property).when(definition).getProperty("lit");
+        when(initial.with(property, true)).thenReturn(lit);
+        Block block = mock(Block.class);
+        Location location = new Location(null, 7, 80, -9);
+        when(block.getLocation()).thenReturn(location);
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class)) {
+            blocks.when(() -> CraftEngineBlocks.byId(Key.of("test:lamp"))).thenReturn(definition);
+            blocks.when(() -> CraftEngineBlocks.place(location, lit, false)).thenReturn(true);
+
+            assertTrue(new CraftEngineDataProvider().placeBlock(block, new Identifier("test", "lamp[lit=true]")));
+
+            blocks.verify(() -> CraftEngineBlocks.place(location, lit, false));
+        }
+    }
+
+    @Test
+    public void directFurniturePlacementDoesNotSpawnEntities() {
+        FurnitureDefinition definition = furnitureDefinition();
+        Block block = mock(Block.class);
+        try (MockedStatic<CraftEngineBlocks> blocks = mockStatic(CraftEngineBlocks.class);
+             MockedStatic<CraftEngineFurniture> furniture = mockStatic(CraftEngineFurniture.class)) {
+            furniture.when(() -> CraftEngineFurniture.byId(Key.of("test:chair"))).thenReturn(definition);
+
+            assertFalse(new CraftEngineDataProvider().placeBlock(block, new Identifier("test", "chair[variant=alpha]")));
+            assertThrows(MissingResourceException.class, () -> new CraftEngineDataProvider().placeBlock(
+                    block, new Identifier("test", "chair[variant=missing]")));
+
+            furniture.verify(() -> CraftEngineFurniture.place(any(Location.class), any(FurnitureDefinition.class), any(String.class), eq(false)), times(0));
+            verify(block, times(0)).getLocation();
+        }
+    }
+
+    private static MockedStatic<RegistryUtil> materialRegistry() {
+        MockedStatic<RegistryUtil> registry = mockStatic(RegistryUtil.class);
+        registry.when(() -> RegistryUtil.find(Material.class, "grass", "short_grass")).thenReturn(Material.SHORT_GRASS);
+        return registry;
+    }
+
+    private static ImmutableBlockState blockState(BlockDefinition definition, String semanticId) {
+        ImmutableBlockState state = mock(ImmutableBlockState.class);
+        when(state.owner()).thenReturn(Holder.direct(definition));
+        when(state.toString()).thenReturn(semanticId);
+        return state;
+    }
+
+    private static FurnitureDefinition furnitureDefinition() {
+        FurnitureDefinition definition = mock(FurnitureDefinition.class);
+        when(definition.id()).thenReturn(Key.of("test:chair"));
+        when(definition.variants()).thenReturn(Map.of("beta", mock(FurnitureVariant.class), "alpha", mock(FurnitureVariant.class)));
+        return definition;
+    }
+}

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

@@ -27,6 +27,7 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.MissingResourceException;
+import java.util.Optional;
 
 @Getter
 @RequiredArgsConstructor
@@ -46,6 +47,14 @@ public abstract class ExternalDataProvider {
 
     public abstract void init();
 
+    public Optional<Identifier> identifyBlock(@NotNull BlockData blockData) {
+        return Optional.empty();
+    }
+
+    public boolean placeBlock(@NotNull Block block, @NotNull Identifier blockId) {
+        return false;
+    }
+
     /**
      * @see ExternalDataProvider#getBlockData(Identifier, KMap)
      */

core/src/main/java/art/arcane/iris/core/link/data/CraftEngineDataProvider.java

@@ -1,20 +1,24 @@
 package art.arcane.iris.core.link.data;
 
-import art.arcane.iris.platform.bukkit.BukkitBlockResolution;
-
 import art.arcane.iris.core.link.ExternalDataProvider;
 import art.arcane.iris.core.link.Identifier;
 import art.arcane.iris.core.nms.container.BlockProperty;
+import art.arcane.iris.core.nms.container.Pair;
 import art.arcane.iris.core.service.ExternalDataSVC;
 import art.arcane.iris.engine.data.cache.Cache;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.platform.bukkit.BukkitBlockResolution;
+import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.util.common.data.IrisCustomData;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.volmlib.util.math.RNG;
 import net.momirealms.craftengine.bukkit.api.CraftEngineBlocks;
 import net.momirealms.craftengine.bukkit.api.CraftEngineFurniture;
 import net.momirealms.craftengine.bukkit.api.CraftEngineItems;
+import net.momirealms.craftengine.bukkit.api.event.CraftEngineReloadEvent;
 import net.momirealms.craftengine.bukkit.item.BukkitItemDefinition;
+import net.momirealms.craftengine.bukkit.plugin.BukkitCraftEngine;
 import net.momirealms.craftengine.core.block.BlockDefinition;
 import net.momirealms.craftengine.core.block.ImmutableBlockState;
 import net.momirealms.craftengine.core.block.property.BooleanProperty;
@@ -22,27 +26,36 @@ import net.momirealms.craftengine.core.block.property.IntegerProperty;
 import net.momirealms.craftengine.core.block.property.Property;
 import net.momirealms.craftengine.core.entity.furniture.FurnitureDefinition;
 import net.momirealms.craftengine.core.util.Key;
+import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.block.Block;
 import org.bukkit.block.data.BlockData;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.Arrays;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.MissingResourceException;
+import java.util.Optional;
+import java.util.Set;
 import java.util.function.Function;
-import java.util.stream.Stream;
+import java.util.stream.Collectors;
 
-public class CraftEngineDataProvider extends ExternalDataProvider {
-    private static final BlockProperty[] FURNITURE_PROPERTIES = new BlockProperty[]{
+public class CraftEngineDataProvider extends ExternalDataProvider implements Listener {
+    private static final List<BlockProperty> FURNITURE_PROPERTIES = List.of(
             BlockProperty.ofBoolean("randomYaw", false),
             BlockProperty.ofDouble("yaw", 0, 0, 360f, false, true),
             BlockProperty.ofBoolean("randomPitch", false),
-            BlockProperty.ofDouble("pitch", 0, 0, 360f, false, true),
-    };
+            BlockProperty.ofDouble("pitch", 0, 0, 360f, false, true)
+    );
+    private static final ContentRegistry EMPTY_CONTENT = new ContentRegistry(Set.of(), Set.of(), false);
+
+    private volatile ContentRegistry content = EMPTY_CONTENT;
 
     public CraftEngineDataProvider() {
         super("CraftEngine");
@@ -50,130 +63,244 @@ public class CraftEngineDataProvider extends ExternalDataProvider {
 
     @Override
     public void init() {
+        content = EMPTY_CONTENT;
+        BukkitCraftEngine plugin = BukkitCraftEngine.instance();
+        if (plugin != null && plugin.isFullyLoaded()) {
+            updateContent();
+        }
+    }
+
+    @Override
+    public boolean isReady() {
+        return content.ready() && super.isReady();
+    }
+
+    @EventHandler
+    public void onReload(CraftEngineReloadEvent event) {
+        if (!updateContent()) {
+            return;
+        }
+        ExternalDataSVC service = IrisServices.getOrNull(ExternalDataSVC.class);
+        if (service != null) {
+            service.notifyContentChanged();
+        }
     }
 
     @Override
     public @NotNull List<BlockProperty> getBlockProperties(@NotNull Identifier blockId) throws MissingResourceException {
-        Key key = Key.of(blockId.namespace(), blockId.key());
-        BlockDefinition block = CraftEngineBlocks.byId(key);
-        if (block != null) {
-            return block.properties().stream().map(CraftEngineDataProvider::convert).toList();
+        ImmutableBlockState blockState = findBlockState(blockId);
+        if (blockState != null) {
+            return blockState.owner().value().properties().stream().map(CraftEngineDataProvider::convert).toList();
         }
-
-        FurnitureDefinition furniture = CraftEngineFurniture.byId(key);
-        if (furniture != null) {
-            BlockProperty[] properties = Arrays.copyOf(FURNITURE_PROPERTIES, 5);
-            properties[4] = new BlockProperty(
-                    "variant",
-                    String.class,
-                    furniture.anyVariantName(),
-                    furniture.variants().keySet(),
-                    Function.identity()
-            );
-            return List.of(properties);
-        }
-
-        throw new MissingResourceException("Failed to find BlockData!", blockId.namespace(), blockId.key());
+        FurnitureDefinition furniture = requireFurniture(blockId);
+        List<BlockProperty> properties = new ArrayList<>(FURNITURE_PROPERTIES);
+        properties.add(new BlockProperty("variant", String.class, defaultVariant(furniture),
+                furniture.variants().keySet(), Function.identity()));
+        return List.copyOf(properties);
     }
 
     @Override
     public @NotNull ItemStack getItemStack(@NotNull Identifier itemId, @NotNull KMap<String, Object> customNbt) throws MissingResourceException {
         BukkitItemDefinition item = CraftEngineItems.byId(Key.of(itemId.namespace(), itemId.key()));
         if (item == null) {
-            throw new MissingResourceException("Failed to find ItemData!", itemId.namespace(), itemId.key());
+            throw missing(itemId, "Failed to find CraftEngine item.");
         }
-
         return item.buildBukkitItem();
     }
 
     @Override
     public @NotNull BlockData getBlockData(@NotNull Identifier blockId, @NotNull KMap<String, String> state) throws MissingResourceException {
-        Key key = Key.of(blockId.namespace(), blockId.key());
-        if (CraftEngineBlocks.byId(key) == null && CraftEngineFurniture.byId(key) == null) {
-            throw new MissingResourceException("Failed to find BlockData!", blockId.namespace(), blockId.key());
+        ImmutableBlockState blockState = findBlockState(blockId);
+        if (blockState != null) {
+            ImmutableBlockState resolved = applyProperties(blockId, blockState, state);
+            return IrisCustomData.of(CraftEngineBlocks.getBukkitBlockData(resolved), Identifier.fromString(resolved.toString()));
+        }
+        FurnitureDefinition furniture = requireFurniture(blockId);
+        KMap<String, String> properties = validateFurnitureProperties(blockId, furniture, state);
+        return IrisCustomData.of(BukkitBlockResolution.getAir(), ExternalDataSVC.buildState(blockId, properties));
     }
 
-        return IrisCustomData.of(BukkitBlockResolution.getAir(), ExternalDataSVC.buildState(blockId, state));
+    @Override
+    public Optional<Identifier> identifyBlock(@NotNull BlockData blockData) {
+        BlockData nativeData = blockData instanceof IrisCustomData custom ? custom.getBase() : blockData;
+        ImmutableBlockState state = CraftEngineBlocks.getCustomBlockState(nativeData);
+        return state == null || state.isEmpty() ? Optional.empty() : Optional.of(Identifier.fromString(state.toString()));
+    }
+
+    @Override
+    public boolean placeBlock(@NotNull Block block, @NotNull Identifier blockId) {
+        Pair<Identifier, KMap<String, String>> parsed = ExternalDataSVC.parseState(blockId);
+        ImmutableBlockState state = findBlockState(parsed.getA());
+        if (state == null) {
+            validateFurnitureProperties(parsed.getA(), requireFurniture(parsed.getA()), parsed.getB());
+            return false;
+        }
+        placeBlockState(block, applyProperties(parsed.getA(), state, parsed.getB()), blockId);
+        return true;
     }
 
     @Override
     public void processUpdate(@NotNull Engine engine, @NotNull Block block, @NotNull Identifier blockId) {
-        art.arcane.iris.core.nms.container.Pair<Identifier, KMap<String, String>> statePair = ExternalDataSVC.parseState(blockId);
+        Pair<Identifier, KMap<String, String>> statePair = ExternalDataSVC.parseState(blockId);
         Identifier baseBlockId = statePair.getA();
         KMap<String, String> state = statePair.getB();
-        Key key = Key.of(baseBlockId.namespace(), baseBlockId.key());
+        ImmutableBlockState blockState = findBlockState(baseBlockId);
+        if (blockState != null) {
+            placeBlockState(block, applyProperties(baseBlockId, blockState, state), blockId);
+            return;
+        }
+        FurnitureDefinition furniture = requireFurniture(baseBlockId);
+        KMap<String, String> properties = validateFurnitureProperties(baseBlockId, furniture, state);
+        Location location = parseYawAndPitch(engine, block, properties);
+        if (CraftEngineFurniture.place(location, furniture, properties.get("variant"), false) == null) {
+            throw missing(blockId, "Failed to place CraftEngine furniture.");
+        }
+    }
 
-        BlockDefinition customBlock = CraftEngineBlocks.byId(key);
-        if (customBlock != null) {
-            ImmutableBlockState blockState = customBlock.defaultState();
+    @Override
+    public @NotNull Collection<@NotNull Identifier> getTypes(@NotNull DataType dataType) {
+        return switch (dataType) {
+            case ENTITY -> List.of();
+            case ITEM -> content.items();
+            case BLOCK -> content.blocks();
+        };
+    }
 
-            for (Map.Entry<String, String> entry : state.entrySet()) {
-                Property<?> property = customBlock.getProperty(entry.getKey());
+    @Override
+    public boolean isValidProvider(@NotNull Identifier id, DataType dataType) {
+        ContentRegistry registry = content;
+        if (!registry.ready()) {
+            return false;
+        }
+        return switch (dataType) {
+            case ENTITY -> false;
+            case ITEM -> registry.items().contains(id);
+            case BLOCK -> registry.blocks().contains(id) || findRuntimeBlockState(id) != null;
+        };
+    }
+
+    private boolean updateContent() {
+        try {
+            Set<Identifier> blocks = new LinkedHashSet<>();
+            for (Key key : CraftEngineBlocks.loadedBlocks().keySet()) {
+                blocks.add(new Identifier(key.namespace(), key.value()));
+            }
+            for (Key key : CraftEngineFurniture.loadedFurniture().keySet()) {
+                blocks.add(new Identifier(key.namespace(), key.value()));
+            }
+            Set<Identifier> items = CraftEngineItems.loadedItems().keySet().stream()
+                    .map(key -> new Identifier(key.namespace(), key.value())).collect(Collectors.toUnmodifiableSet());
+            content = new ContentRegistry(items, Set.copyOf(blocks), true);
+            return true;
+        } catch (RuntimeException | LinkageError error) {
+            content = EMPTY_CONTENT;
+            IrisLogging.reportError("Failed to update CraftEngine content registry.", error);
+            return false;
+        }
+    }
+
+    private static ImmutableBlockState findBlockState(Identifier blockId) {
+        BlockDefinition block = CraftEngineBlocks.byId(Key.of(blockId.namespace(), blockId.key()));
+        return block != null ? block.defaultState() : findRuntimeBlockState(blockId);
+    }
+
+    private static ImmutableBlockState findRuntimeBlockState(Identifier blockId) {
+        if (!Key.CRAFTENGINE_NAMESPACE.equals(blockId.namespace())) {
+            return null;
+        }
+        BlockData data;
+        try {
+            data = Bukkit.createBlockData(blockId.toString());
+        } catch (IllegalArgumentException error) {
+            return null;
+        }
+        ImmutableBlockState state = CraftEngineBlocks.getCustomBlockState(data);
+        return state == null || state.isEmpty() ? null : state;
+    }
+
+    private static ImmutableBlockState applyProperties(Identifier id, ImmutableBlockState state, Map<String, String> properties) {
+        BlockDefinition block = state.owner().value();
+        for (Map.Entry<String, String> entry : properties.entrySet()) {
+            Property<?> property = block.getProperty(entry.getKey());
             if (property == null) {
-                    continue;
+                throw missing(id, "Unknown CraftEngine block property '" + entry.getKey() + "'.");
+            }
+            Comparable<?> value = property.optional(entry.getValue()).orElse(null);
+            if (value == null) {
+                throw missing(id, "Invalid CraftEngine block property '" + entry.getKey() + "=" + entry.getValue() + "'.");
+            }
+            state = ImmutableBlockState.with(state, property, value);
+        }
+        return state;
     }
 
-                Comparable<?> tag = property.optional(entry.getValue()).orElse(null);
-                if (tag == null) {
-                    continue;
+    private static void placeBlockState(Block block, ImmutableBlockState state, Identifier id) {
+        if (!CraftEngineBlocks.place(block.getLocation(), state, false)
+                && !state.equals(CraftEngineBlocks.getCustomBlockState(block))) {
+            throw missing(id, "Failed to place CraftEngine block.");
+        }
     }
 
-                blockState = ImmutableBlockState.with(blockState, property, tag);
-            }
-
-            CraftEngineBlocks.place(block.getLocation(), blockState, false);
-            return;
-        }
-
-        FurnitureDefinition furniture = CraftEngineFurniture.byId(key);
+    private static FurnitureDefinition requireFurniture(Identifier id) {
+        FurnitureDefinition furniture = CraftEngineFurniture.byId(Key.of(id.namespace(), id.key()));
         if (furniture == null) {
-            return;
+            throw missing(id, "Failed to find CraftEngine block or furniture.");
+        }
+        return furniture;
     }
 
-        Location location = parseYawAndPitch(engine, block, state);
-        String variant = state.getOrDefault("variant", furniture.anyVariantName());
-        CraftEngineFurniture.place(location, furniture, variant, false);
+    private static KMap<String, String> validateFurnitureProperties(Identifier id, FurnitureDefinition furniture, Map<String, String> state) {
+        KMap<String, String> properties = new KMap<>();
+        for (Map.Entry<String, String> entry : state.entrySet()) {
+            String value = entry.getValue();
+            switch (entry.getKey()) {
+                case "randomYaw", "randomPitch" -> {
+                    if (!"true".equals(value) && !"false".equals(value)) {
+                        throw missing(id, "Invalid CraftEngine furniture boolean '" + entry.getKey() + "=" + value + "'.");
+                    }
+                }
+                case "yaw", "pitch" -> validateAngle(id, entry.getKey(), value);
+                case "variant" -> {
+                    if (!furniture.variants().containsKey(value)) {
+                        throw missing(id, "Unknown CraftEngine furniture variant '" + value + "'.");
+                    }
+                }
+                default -> throw missing(id, "Unknown CraftEngine furniture property '" + entry.getKey() + "'.");
+            }
+            properties.put(entry.getKey(), value);
+        }
+        properties.putIfAbsent("variant", defaultVariant(furniture));
+        return properties;
+    }
+
+    private static void validateAngle(Identifier id, String property, String value) {
+        float angle;
+        try {
+            angle = Float.parseFloat(value);
+        } catch (NumberFormatException error) {
+            throw missing(id, "Invalid CraftEngine furniture angle '" + property + "=" + value + "'.");
+        }
+        if (!Float.isFinite(angle) || angle < 0 || angle >= 360) {
+            throw missing(id, "CraftEngine furniture angle '" + property + "' must be at least 0 and below 360.");
+        }
+    }
+
+    private static String defaultVariant(FurnitureDefinition furniture) {
+        return furniture.variants().keySet().stream().sorted().findFirst()
+                .orElseThrow(() -> missing(Identifier.fromString(furniture.id().toString()), "CraftEngine furniture has no variants."));
     }
 
     private static Location parseYawAndPitch(@NotNull Engine engine, @NotNull Block block, @NotNull Map<String, String> state) {
         Location location = block.getLocation();
         long seed = engine.getSeedManager().getSeed() + Cache.key(block.getX(), block.getZ()) + block.getY();
         RNG rng = new RNG(seed);
-
-        if ("true".equals(state.get("randomYaw"))) {
-            location.setYaw(rng.f(0, 360));
-        } else if (state.containsKey("yaw")) {
-            location.setYaw(Float.parseFloat(state.get("yaw")));
-        }
-
-        if ("true".equals(state.get("randomPitch"))) {
-            location.setPitch(rng.f(0, 360));
-        } else if (state.containsKey("pitch")) {
-            location.setPitch(Float.parseFloat(state.get("pitch")));
-        }
-
+        location.setYaw("true".equals(state.get("randomYaw")) ? rng.f(0, 360) : Float.parseFloat(state.getOrDefault("yaw", "0")));
+        location.setPitch("true".equals(state.get("randomPitch")) ? rng.f(0, 360) : Float.parseFloat(state.getOrDefault("pitch", "0")));
         return location;
     }
 
-    @Override
-    public @NotNull Collection<@NotNull Identifier> getTypes(@NotNull DataType dataType) {
-        Stream<Key> keys = switch (dataType) {
-            case ENTITY -> Stream.<Key>empty();
-            case ITEM -> CraftEngineItems.loadedItems().keySet().stream();
-            case BLOCK -> Stream.concat(CraftEngineBlocks.loadedBlocks().keySet().stream(),
-                    CraftEngineFurniture.loadedFurniture().keySet().stream());
-        };
-        return keys.map(key -> new Identifier(key.namespace(), key.value())).toList();
-    }
-
-    @Override
-    public boolean isValidProvider(@NotNull Identifier id, DataType dataType) {
-        Key key = Key.of(id.namespace(), id.key());
-        return switch (dataType) {
-            case ENTITY -> false;
-            case ITEM -> CraftEngineItems.byId(key) != null;
-            case BLOCK -> CraftEngineBlocks.byId(key) != null || CraftEngineFurniture.byId(key) != null;
-        };
+    private static MissingResourceException missing(Identifier id, String message) {
+        return new MissingResourceException(message, id.namespace(), id.key());
     }
 
     private static <T extends Comparable<T>> BlockProperty convert(Property<T> raw) {
@@ -183,4 +310,7 @@ public class CraftEngineDataProvider extends ExternalDataProvider {
             default -> new BlockProperty(raw.name(), raw.valueClass(), raw.defaultValue(), raw.possibleValues(), raw::valueName);
         };
     }
+
+    private record ContentRegistry(Set<Identifier> items, Set<Identifier> blocks, boolean ready) {
+    }
 }

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

@@ -27,6 +27,7 @@ import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.engine.framework.BiomeEnvironment;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.EngineLifecycleTasks;
 import art.arcane.iris.engine.history.SavedBiomeUnavailableException;
 import art.arcane.iris.engine.platform.PlatformChunkGenerator;
 import art.arcane.volmlib.util.board.Board;
@@ -498,8 +499,13 @@ public class BoardSVC implements IrisService, BoardProvider {
                 return;
             }
 
+            EngineLifecycleTasks.run(engine, "bukkit_studio_scoreboard",
+                    () -> updateOrdinary(engine, loc, world.getMinHeight()));
+        }
+
+        private void updateOrdinary(Engine engine, Location loc, int minimumY) {
             int x = loc.getBlockX();
-            int y = loc.getBlockY() - world.getMinHeight();
+            int y = loc.getBlockY() - minimumY;
             int z = loc.getBlockZ();
 
             List<String> lines = new ArrayList<>(this.lines.size());

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

@@ -180,6 +180,20 @@ public class ExternalDataSVC implements IrisService {
         }
     }
 
+    public BlockData captureBlockData(BlockData blockData) {
+        Objects.requireNonNull(blockData);
+        if (blockData instanceof IrisCustomData) {
+            return blockData;
+        }
+        for (ExternalDataProvider provider : activeProviders) {
+            Optional<Identifier> identifier = provider.identifyBlock(blockData);
+            if (identifier.isPresent()) {
+                return IrisCustomData.of(blockData, qualifyBlockId(provider, identifier.get()));
+            }
+        }
+        return blockData;
+    }
+
     public Optional<BlockData> getBlockData(final Identifier key) {
         Pair<Identifier, KMap<String, String>> pair;
         try {
@@ -244,6 +258,15 @@ public class ExternalDataSVC implements IrisService {
         match.provider().processUpdate(engine, block, buildState(match.identifier(), state.getB()));
     }
 
+    public boolean placeBlock(Block block, Identifier blockId) {
+        Pair<Identifier, KMap<String, String>> state = parseState(blockId);
+        BlockProvider match = findBlockProvider(state.getA());
+        if (match == null) {
+            throw new MissingResourceException("No matching provider found for external block placement.", blockId.namespace(), blockId.key());
+        }
+        return match.provider().placeBlock(block, buildState(match.identifier(), state.getB()));
+    }
+
     public Entity spawnMob(Location location, Identifier mobId) {
         Optional<ExternalDataProvider> provider = activeProviders.stream().filter(p -> p.isValidProvider(mobId, DataType.ENTITY)).findFirst();
         if (provider.isEmpty()) {

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

@@ -18,6 +18,9 @@
 
 package art.arcane.iris.core.service;
 
+import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.util.common.data.IrisCustomData;
 import art.arcane.iris.util.common.plugin.IrisService;
 import art.arcane.iris.util.common.scheduling.J;
 import lombok.Getter;
@@ -81,7 +84,11 @@ public class ObjectSVC implements IrisService {
             int amount = 0;
             while (it.hasNext()) {
                 Map.Entry<Block, BlockData> entry = it.next();
-                entry.getKey().setBlockData(entry.getValue(), false);
+                Block block = entry.getKey();
+                BlockData data = entry.getValue();
+                if (!J.runAt(block.getLocation(), () -> restoreBlock(block, data))) {
+                    IrisLogging.warn("Could not schedule object undo at %d, %d, %d.", block.getX(), block.getY(), block.getZ());
+                }
                 it.remove();
 
                 if (++amount >= 200) {
@@ -94,4 +101,16 @@ public class ObjectSVC implements IrisService {
             }
         });
     }
+
+    private static void restoreBlock(Block block, BlockData data) {
+        if (data instanceof IrisCustomData custom) {
+            ExternalDataSVC external = IrisServices.getOrNull(ExternalDataSVC.class);
+            if (external != null && external.placeBlock(block, custom.getCustom())) {
+                return;
+            }
+            block.setBlockData(custom.getBase(), false);
+            return;
+        }
+        block.setBlockData(data, false);
+    }
 }

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

@@ -277,6 +277,13 @@ final class EngineRuntimeBuilder {
             throw propagate(failure);
         }
         EngineRuntime next = new EngineRuntime(previous.generation(), effects, worldManager);
+        try {
+            worldManager.start();
+        } catch (Throwable failure) {
+            failure = EngineShutdownSequence.runCleanup(failure, worldManager::close);
+            failure = EngineShutdownSequence.runCleanup(failure, effects::close);
+            throw new IllegalStateException("Failed to start the replacement Studio world manager.", failure);
+        }
         Throwable retirementFailure = EngineShutdownSequence.runCleanup(null, previous.worldManager()::close);
         retirementFailure = EngineShutdownSequence.runCleanup(retirementFailure, previous.effects()::close);
         if (retirementFailure != null) {
@@ -285,7 +292,6 @@ final class EngineRuntimeBuilder {
             throw new IllegalStateException("Failed to retire Studio runtime services.", retirementFailure);
         }
         engine.runtime = next;
-        worldManager.start();
         engine.getGenerationSessions().activateNextSession();
         engine.lifecycleState = LifecycleState.RUNNING;
         engine.getClosing().set(false);

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

@@ -1459,6 +1459,13 @@ public class IrisEngine implements Engine {
         return closing.get();
     }
 
+    @Override
+    public boolean isShuttingDown() {
+        LifecycleState state = lifecycleState;
+        return closed || state == LifecycleState.CLOSING
+                || state == LifecycleState.CLOSED || state == LifecycleState.FAILED;
+    }
+
     @Override
     public void recycle() {
         if (closing.get() || closed) {

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

@@ -195,6 +195,10 @@ public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer,
         return isClosed();
     }
 
+    default boolean isShuttingDown() {
+        return isClosed() || isClosing();
+    }
+
     double getMaxBiomeObjectDensity();
 
     double getMaxBiomeDecoratorDensity();

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

@@ -131,8 +131,9 @@ public abstract class EngineAssignedWorldManager extends EngineAssignedComponent
 
     @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
     public void on(PlayerTeleportEvent e) {
+        Engine engine = getEngine();
         if (!BukkitPlatform.isPaperServer()
-                || !getEngine().isStudio()
+                || !engine.isStudio()
                 || e.getCause() != PlayerTeleportEvent.TeleportCause.COMMAND) {
             return;
         }
@@ -142,6 +143,10 @@ public abstract class EngineAssignedWorldManager extends EngineAssignedComponent
         if (destination == null || targetWorld == null || !targetWorld.equals(destination.getWorld())) {
             return;
         }
+        if (engine.isShuttingDown()) {
+            e.setCancelled(true);
+            return;
+        }
 
         int chunkX = destination.getBlockX() >> 4;
         int chunkZ = destination.getBlockZ() >> 4;
@@ -149,7 +154,7 @@ public abstract class EngineAssignedWorldManager extends EngineAssignedComponent
             return;
         }
 
-        runManagerTask("bukkit_world_manager_teleport_event", () -> teleportAsync(e));
+        teleportAsync(e);
     }
 
     @EventHandler

core/src/main/java/art/arcane/iris/engine/history/GenerationBoundaryStore.java

@@ -619,6 +619,7 @@ public final class GenerationBoundaryStore {
         private final long[] regionKeys;
         private final Long2ObjectOpenHashMap<String> shardHashes;
         private final LinkedHashMap<Long, byte[]> masks;
+        private final ThreadLocal<RegionMask> lastRegion = new ThreadLocal<>();
 
         private MaskSource(
                 Path directory,
@@ -634,13 +635,21 @@ public final class GenerationBoundaryStore {
         @Override
         public boolean contains(int chunkX, int chunkZ) throws IOException {
             long regionKey = packRegion(chunkX >> 5, chunkZ >> 5);
+            RegionMask region = lastRegion.get();
+            if (region == null || region.key() != regionKey) {
                 String hash = shardHashes.get(regionKey);
-            if (hash == null) {
-                return false;
-            }
-            byte[] mask;
+                byte[] loaded = null;
+                if (hash != null) {
                     synchronized (this) {
-                mask = load(regionKey, hash);
+                        loaded = load(regionKey, hash);
+                    }
+                }
+                region = new RegionMask(regionKey, loaded);
+                lastRegion.set(region);
+            }
+            byte[] mask = region.mask();
+            if (mask == null) {
+                return false;
             }
             int localIndex = (Math.floorMod(chunkZ, REGION_SIDE) << 5)
                     | Math.floorMod(chunkX, REGION_SIDE);
@@ -686,6 +695,9 @@ public final class GenerationBoundaryStore {
             }
             return loaded;
         }
+
+        private record RegionMask(long key, byte[] mask) {
+        }
     }
 
     private static final class LimitedInputStream extends InputStream {

core/src/main/java/art/arcane/iris/engine/history/TerrainBoundarySignatureStore.java

@@ -46,6 +46,9 @@ import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.PriorityQueue;
 import java.util.TreeSet;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.LongAdder;
 import java.util.zip.CRC32;
 
 public final class TerrainBoundarySignatureStore {
@@ -936,8 +939,9 @@ public final class TerrainBoundarySignatureStore {
         private final Long2ObjectOpenHashMap<CellReference> cells;
         private final Long2ObjectOpenHashMap<long[]> cellsBySuperCell;
         private final LinkedHashMap<Long, List<TerrainBoundarySignature>> cache;
-        private long catalogProbes;
-        private long shardLoads;
+        private final Map<Long, CompletableFuture<List<TerrainBoundarySignature>>> pendingLoads = new HashMap<>();
+        private final LongAdder catalogProbes = new LongAdder();
+        private final LongAdder shardLoads = new LongAdder();
 
         private CellSource(
                 Path directory,
@@ -951,7 +955,7 @@ public final class TerrainBoundarySignatureStore {
             this.cache = new LinkedHashMap<>(MAXIMUM_CACHED_SHARDS, 0.75F, true);
         }
 
-        private synchronized TerrainBoundarySignature signatureAt(int blockX, int blockZ) throws IOException {
+        private TerrainBoundarySignature signatureAt(int blockX, int blockZ) throws IOException {
             int cellX = Math.floorDiv(blockX, CELL_SIZE);
             int cellZ = Math.floorDiv(blockZ, CELL_SIZE);
             long cellKey = pack(cellX, cellZ);
@@ -967,7 +971,7 @@ public final class TerrainBoundarySignatureStore {
             return null;
         }
 
-        private synchronized List<TerrainBoundarySignature> all() throws IOException {
+        private List<TerrainBoundarySignature> all() throws IOException {
             ArrayList<TerrainBoundarySignature> signatures = new ArrayList<>();
             for (long cellKey : cellKeys) {
                 signatures.addAll(load(cellKey, cells.get(cellKey)));
@@ -978,7 +982,7 @@ public final class TerrainBoundarySignatureStore {
             return List.copyOf(signatures);
         }
 
-        private synchronized List<TerrainBoundarySignature> nearestCandidatesForChunk(
+        private List<TerrainBoundarySignature> nearestCandidatesForChunk(
                 int chunkX,
                 int chunkZ,
                 int searchWidth
@@ -1019,7 +1023,7 @@ public final class TerrainBoundarySignatureStore {
             return nearest.candidates();
         }
 
-        private synchronized boolean intersectsTerrainBand(BlockBounds footprint, int width) throws IOException {
+        private boolean intersectsTerrainBand(BlockBounds footprint, int width) throws IOException {
             double distanceSquared = (double) width * width;
             return visitSuperCells(footprint.expanded(width - 1L), superKey -> {
                 if (footprint.distanceSquared(BlockBounds.cell(superKey, CELL_SIZE * SUPER_CELL_SIZE))
@@ -1050,7 +1054,7 @@ public final class TerrainBoundarySignatureStore {
             long height = (long) maximumZ - minimumZ + 1L;
             if (width > cellsBySuperCell.size() / height) {
                 for (long key : cellsBySuperCell.keySet()) {
-                    catalogProbes++;
+                    catalogProbes.increment();
                     if (cellX(key) >= minimumX && cellX(key) <= maximumX
                             && cellZ(key) >= minimumZ && cellZ(key) <= maximumZ
                             && visitor.visit(key)) {
@@ -1061,7 +1065,7 @@ public final class TerrainBoundarySignatureStore {
             }
             for (long x = minimumX; x <= maximumX; x++) {
                 for (long z = minimumZ; z <= maximumZ; z++) {
-                    catalogProbes++;
+                    catalogProbes.increment();
                     long key = pack((int) x, (int) z);
                     if (cellsBySuperCell.containsKey(key) && visitor.visit(key)) {
                         return true;
@@ -1072,33 +1076,61 @@ public final class TerrainBoundarySignatureStore {
         }
 
         private List<TerrainBoundarySignature> load(long cellKey, CellReference reference) throws IOException {
+            CompletableFuture<List<TerrainBoundarySignature>> pending;
+            boolean loader;
+            synchronized (this) {
                 List<TerrainBoundarySignature> cached = cache.get(cellKey);
                 if (cached != null) {
                     return cached;
                 }
+                pending = pendingLoads.get(cellKey);
+                loader = pending == null;
+                if (loader) {
+                    pending = new CompletableFuture<>();
+                    pendingLoads.put(cellKey, pending);
+                }
+            }
+            if (!loader) {
+                try {
+                    return pending.join();
+                } catch (CompletionException failure) {
+                    if (failure.getCause() instanceof IOException io) {
+                        throw io;
+                    }
+                    throw failure;
+                }
+            }
+            try {
                 Path shard = directory.resolve(shardFileName(reference.hash()));
                 requireRegularFile(shard, "Terrain boundary shard");
                 List<TerrainBoundarySignature> loaded = CellShard.read(
-                    shard,
-                    reference.hash(),
-                    cellX(cellKey),
-                    cellZ(cellKey)
-            );
+                        shard, reference.hash(), cellX(cellKey), cellZ(cellKey));
                 if (loaded.size() != reference.count()) {
                     throw new IOException("Terrain boundary shard count does not match its catalog entry");
                 }
-            shardLoads++;
+                synchronized (this) {
+                    shardLoads.increment();
                     cache.put(cellKey, loaded);
                     trim(cache);
+                }
+                pending.complete(loaded);
                 return loaded;
+            } catch (IOException | RuntimeException | Error failure) {
+                pending.completeExceptionally(failure);
+                throw failure;
+            } finally {
+                synchronized (this) {
+                    pendingLoads.remove(cellKey, pending);
+                }
+            }
         }
 
-        private synchronized long catalogProbeCount() {
-            return catalogProbes;
+        private long catalogProbeCount() {
+            return catalogProbes.sum();
         }
 
-        private synchronized long shardLoadCount() {
-            return shardLoads;
+        private long shardLoadCount() {
+            return shardLoads.sum();
         }
 
         private synchronized int cachedShardCount() {

core/src/main/java/art/arcane/iris/engine/history/TransitionBoundarySampler.java

@@ -3,21 +3,26 @@ package art.arcane.iris.engine.history;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.concurrent.CompletableFuture;
 
 final class TransitionBoundarySampler {
     private static final int NEIGHBOUR_COUNT = 4;
-    private static final int MAXIMUM_CACHED_CHUNKS = 8;
+    private static final int MAXIMUM_CACHED_CHUNKS = 512;
+    private static final int MAXIMUM_CACHED_CANDIDATES = 32_768;
 
     private final int terrainWidth;
     private final int searchWidth;
     private final TerrainBoundarySignatureStore.Snapshot signatures;
     private final LinkedHashMap<Long, CandidateIndex> chunkCandidates;
+    private final Map<Long, CompletableFuture<CandidateIndex>> pendingCandidates = new HashMap<>();
     private final ThreadLocal<ChunkCache> cache;
+    private int cachedCandidates;
     private long candidateBuildCount;
 
     TransitionBoundarySampler(
@@ -35,12 +40,7 @@ final class TransitionBoundarySampler {
     }
 
     TransitionGenerationPlan.TerrainSample sample(int blockX, int blockZ) {
-        ChunkCache chunkCache = cache.get();
-        int chunkX = Math.floorDiv(blockX, GenerationBoundary.CHUNK_SIZE);
-        int chunkZ = Math.floorDiv(blockZ, GenerationBoundary.CHUNK_SIZE);
-        if (chunkCache.chunkX != chunkX || chunkCache.chunkZ != chunkZ) {
-            chunkCache.reset(chunkX, chunkZ, candidatesForChunk(chunkX, chunkZ));
-        }
+        ChunkCache chunkCache = chunkCache(blockX, blockZ);
         int localX = Math.floorMod(blockX, GenerationBoundary.CHUNK_SIZE);
         int localZ = Math.floorMod(blockZ, GenerationBoundary.CHUNK_SIZE);
         int index = localX * GenerationBoundary.CHUNK_SIZE + localZ;
@@ -58,9 +58,7 @@ final class TransitionBoundarySampler {
     }
 
     BoundaryGeometryInfluence geometryAt(int blockX, int blockZ) {
-        CandidateIndex candidates = candidatesForChunk(
-                Math.floorDiv(blockX, GenerationBoundary.CHUNK_SIZE),
-                Math.floorDiv(blockZ, GenerationBoundary.CHUNK_SIZE));
+        CandidateIndex candidates = chunkCache(blockX, blockZ).candidates;
         Nearest nearest = candidates.nearest(blockX, blockZ, square(terrainWidth));
         if (nearest.count == 0 || nearest.distancesSquared[0] >= square(terrainWidth)) {
             return BoundaryGeometryInfluence.none();
@@ -132,31 +130,57 @@ final class TransitionBoundarySampler {
 
     private CandidateIndex candidatesForChunk(int chunkX, int chunkZ) {
         long chunkKey = pack(chunkX, chunkZ);
+        CompletableFuture<CandidateIndex> pending;
+        boolean builder;
         synchronized (this) {
             CandidateIndex existing = chunkCandidates.get(chunkKey);
             if (existing != null) {
                 return existing;
             }
+            pending = pendingCandidates.get(chunkKey);
+            builder = pending == null;
+            if (builder) {
+                pending = new CompletableFuture<>();
+                pendingCandidates.put(chunkKey, pending);
             }
+        }
+        if (!builder) {
+            return pending.join();
+        }
+        try {
             CandidateIndex built = CandidateIndex.build(signatures.nearestCandidatesForChunk(
-                chunkX,
-                chunkZ,
-                searchWidth
-        ));
+                    chunkX, chunkZ, searchWidth));
             synchronized (this) {
-            CandidateIndex raced = chunkCandidates.get(chunkKey);
-            if (raced != null) {
-                return raced;
-            }
                 chunkCandidates.put(chunkKey, built);
+                cachedCandidates += built.size;
                 candidateBuildCount++;
-            while (chunkCandidates.size() > MAXIMUM_CACHED_CHUNKS) {
+                while (chunkCandidates.size() > MAXIMUM_CACHED_CHUNKS
+                        || cachedCandidates > MAXIMUM_CACHED_CANDIDATES) {
                     Iterator<Map.Entry<Long, CandidateIndex>> entries = chunkCandidates.entrySet().iterator();
-                entries.next();
+                    cachedCandidates -= entries.next().getValue().size;
                     entries.remove();
                 }
-            return built;
             }
+            pending.complete(built);
+            return built;
+        } catch (RuntimeException | Error failure) {
+            pending.completeExceptionally(failure);
+            throw failure;
+        } finally {
+            synchronized (this) {
+                pendingCandidates.remove(chunkKey, pending);
+            }
+        }
+    }
+
+    private ChunkCache chunkCache(int blockX, int blockZ) {
+        ChunkCache chunkCache = cache.get();
+        int chunkX = Math.floorDiv(blockX, GenerationBoundary.CHUNK_SIZE);
+        int chunkZ = Math.floorDiv(blockZ, GenerationBoundary.CHUNK_SIZE);
+        if (chunkCache.chunkX != chunkX || chunkCache.chunkZ != chunkZ) {
+            chunkCache.reset(chunkX, chunkZ, candidatesForChunk(chunkX, chunkZ));
+        }
+        return chunkCache;
     }
 
     private static double weightedHeight(Nearest nearest, boolean surface) {
@@ -208,12 +232,14 @@ final class TransitionBoundarySampler {
     }
 
     private static final class CandidateIndex {
-        private static final CandidateIndex EMPTY = new CandidateIndex(null);
+        private static final CandidateIndex EMPTY = new CandidateIndex(null, 0);
 
         private final Node root;
+        private final int size;
 
-        private CandidateIndex(Node root) {
+        private CandidateIndex(Node root, int size) {
             this.root = root;
+            this.size = size;
         }
 
         private static CandidateIndex build(List<TerrainBoundarySignature> candidates) {
@@ -221,7 +247,7 @@ final class TransitionBoundarySampler {
                 return EMPTY;
             }
             TerrainBoundarySignature[] values = candidates.toArray(new TerrainBoundarySignature[0]);
-            return new CandidateIndex(build(values, 0, values.length, 0));
+            return new CandidateIndex(build(values, 0, values.length, 0), values.length);
         }
 
         private Nearest nearest(int blockX, int blockZ, double maximumDistanceSquared) {

core/src/main/java/art/arcane/iris/engine/object/IrisObject.java

@@ -22,13 +22,16 @@ import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.core.compat.CompatStatus;
 import art.arcane.iris.core.compat.ContentGate;
 import art.arcane.iris.core.loader.IrisRegistrant;
+import art.arcane.iris.core.service.ExternalDataSVC;
 import art.arcane.iris.engine.data.cache.AtomicCache;
 import art.arcane.iris.platform.bukkit.BukkitBlockState;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisPlatform;
 import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.iris.util.common.data.B;
+import art.arcane.iris.util.common.data.IrisCustomData;
 import art.arcane.iris.util.common.data.VectorMap;
 import art.arcane.iris.util.common.math.AxisAlignedBB;
 import art.arcane.iris.util.common.math.IrisBlockVector;
@@ -288,6 +291,10 @@ public class IrisObject extends IrisRegistrant {
             states.remove(v);
         } else {
             BlockData data = block.getBlockData();
+            ExternalDataSVC externalData = IrisServices.getOrNull(ExternalDataSVC.class);
+            if (externalData != null) {
+                data = externalData.captureBlockData(data);
+            }
             blocks.put(v, BukkitBlockState.of(data));
             TileData state = TileData.getTileState(block, legacy);
             if (state != null) {
@@ -363,10 +370,10 @@ public class IrisObject extends IrisRegistrant {
     public void place(Location at) {
         readLock.lock();
         try {
-            for (var entry : blocks) {
-                var i = entry.getKey();
+            for (Map.Entry<IrisBlockVector, PlatformBlockState> entry : blocks) {
+                IrisBlockVector i = entry.getKey();
                 Block b = at.clone().add(0, getCenter().getY(), 0).add(i.getX(), i.getY(), i.getZ()).getBlock();
-                b.setBlockData((BlockData) Objects.requireNonNull(entry.getValue()).nativeHandle(), false);
+                placeBlock(b, (BlockData) Objects.requireNonNull(entry.getValue()).nativeHandle());
 
                 if (states.containsKey(i)) {
                     IrisLogging.info(Objects.requireNonNull(states.get(i)).toString());
@@ -381,10 +388,10 @@ public class IrisObject extends IrisRegistrant {
     public void placeCenterY(Location at) {
         readLock.lock();
         try {
-            for (var entry : blocks) {
-                var i = entry.getKey();
+            for (Map.Entry<IrisBlockVector, PlatformBlockState> entry : blocks) {
+                IrisBlockVector i = entry.getKey();
                 Block b = at.clone().add(getCenter().getX(), getCenter().getY(), getCenter().getZ()).add(i.getX(), i.getY(), i.getZ()).getBlock();
-                b.setBlockData((BlockData) Objects.requireNonNull(entry.getValue()).nativeHandle(), false);
+                placeBlock(b, (BlockData) Objects.requireNonNull(entry.getValue()).nativeHandle());
 
                 if (states.containsKey(i)) {
                     Objects.requireNonNull(states.get(i)).toBukkitTry(b);
@@ -406,6 +413,7 @@ public class IrisObject extends IrisRegistrant {
         }
     }
 
+
     public int volume() {
         return blocks.size();
     }
@@ -429,4 +437,18 @@ public class IrisObject extends IrisRegistrant {
     public CompatStatus evaluateCompat(ContentGate gate) {
         return CompatStatus.OK;
     }
+    private static void placeBlock(Block block, BlockData data) {
+        if (data instanceof IrisCustomData custom) {
+            ExternalDataSVC external = IrisServices.getOrNull(ExternalDataSVC.class);
+            if (external != null && external.placeBlock(block, custom.getCustom())) {
+                return;
+            }
+            block.setBlockData(custom.getBase(), false);
+            IrisLogging.warnOnce("object-paste:external:" + custom.getCustom(),
+                    "Direct placement of %s is unavailable; only its base block was placed.", custom.getCustom());
+            return;
+        }
+        block.setBlockData(data, false);
+    }
+
 }

core/src/main/java/art/arcane/iris/engine/object/IrisObjectIO.java

@@ -138,7 +138,7 @@ public final class IrisObjectIO {
         for (int i = 0; i < s; i++) {
             IrisBlockVector pos = new IrisBlockVector(din.readShort(), din.readShort(), din.readShort());
             PlatformBlockState data = resolvePaletteState(self, din.readUTF());
-            if (isStructureMarker(data)) {
+            if (isExcludedObjectBlock(data)) {
                 continue;
             }
             self.blocks.put(pos, data);
@@ -151,7 +151,7 @@ public final class IrisObjectIO {
             int size = din.readInt();
 
             for (int i = 0; i < size; i++) {
-                self.states.put(new IrisBlockVector(din.readShort(), din.readShort(), din.readShort()), TileData.read(din));
+                readTile(self, din);
             }
         } catch (Throwable e) {
             IrisLogging.reportError(e);
@@ -189,7 +189,7 @@ public final class IrisObjectIO {
         for (i = 0; i < s; i++) {
             IrisBlockVector pos = new IrisBlockVector(din.readShort(), din.readShort(), din.readShort());
             PlatformBlockState data = resolved[din.readShort()];
-            if (isStructureMarker(data)) {
+            if (isExcludedObjectBlock(data)) {
                 continue;
             }
             self.blocks.put(pos, data);
@@ -198,7 +198,15 @@ public final class IrisObjectIO {
         s = din.readInt();
 
         for (i = 0; i < s; i++) {
-            self.states.put(new IrisBlockVector(din.readShort(), din.readShort(), din.readShort()), TileData.read(din));
+            readTile(self, din);
+        }
+    }
+
+    private static void readTile(IrisObject self, DataInputStream input) throws IOException {
+        IrisBlockVector position = new IrisBlockVector(input.readShort(), input.readShort(), input.readShort());
+        TileData tile = TileData.read(input);
+        if (self.blocks.get(position) != null) {
+            self.states.put(position, tile);
         }
     }
 
@@ -251,12 +259,13 @@ public final class IrisObjectIO {
         return B.getState(key);
     }
 
-    private static boolean isStructureMarker(PlatformBlockState data) {
+    private static boolean isExcludedObjectBlock(PlatformBlockState data) {
         if (data == null) {
             return false;
         }
         String material = IrisObjectShaping.materialKey(data);
-        return material.equals("minecraft:jigsaw") || material.equals("minecraft:structure_block") || material.equals("minecraft:structure_void");
+        return material.equals("minecraft:jigsaw") || material.equals("minecraft:structure_block")
+                || material.equals("minecraft:structure_void") || material.equals("minecraft:moving_piston");
     }
 
     /**

core/src/main/java/art/arcane/iris/engine/object/IrisObjectRotation.java

@@ -24,6 +24,7 @@ import art.arcane.iris.core.compat.MissingBlockState;
 import art.arcane.iris.platform.bukkit.BukkitBlockState;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.util.common.data.IrisCustomData;
 import art.arcane.iris.util.common.math.IrisBlockVector;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
@@ -72,6 +73,7 @@ public class IrisObjectRotation {
 
     private static final class Faces {
         private static final List<BlockFace> WALL_FACES = List.of(BlockFace.NORTH, BlockFace.SOUTH, BlockFace.EAST, BlockFace.WEST);
+
     }
 
     @Desc("If this rotator is enabled or not")
@@ -298,7 +300,16 @@ public class IrisObjectRotation {
         }
 
         BlockData original = (BlockData) state.nativeHandle();
-        if (!canRotate() || !canRotateBlockData(original)) {
+        if (!canRotate()) {
+            return state;
+        }
+        if (original instanceof IrisCustomData custom) {
+            BlockData rotated = BukkitBlockState.rotateCustomData(this, custom, spinx, spiny, spinz);
+            if (rotated != null) {
+                return rotated == original ? state : BukkitBlockState.of(rotated);
+            }
+        }
+        if (!canRotateBlockData(original)) {
             return state;
         }
 
@@ -317,6 +328,12 @@ public class IrisObjectRotation {
     }
 
     public BlockData rotate(BlockData dd, int spinxx, int spinyy, int spinzz) {
+        if (canRotate() && dd instanceof IrisCustomData custom) {
+            BlockData rotated = BukkitBlockState.rotateCustomData(this, custom, spinxx, spinyy, spinzz);
+            if (rotated != null) {
+                return rotated;
+            }
+        }
         BlockData d = dd;
         try {
             int spinx = (int) (90D * (Math.ceil(Math.abs((spinxx % 360D) / 90D))));

core/src/main/java/art/arcane/iris/engine/platform/BukkitChunkGenerator.java

@@ -1122,13 +1122,23 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
         Runnable activeOperation = Objects.requireNonNull(operation, "Exclusive control operation");
         CompletableFuture<Void> outward = Objects.requireNonNull(future, "Exclusive control future");
         TimeUnit activeUnit = Objects.requireNonNull(unit, "Exclusive control timeout unit");
+        if (outward.isCancelled()) {
+            return;
+        }
+        ExclusiveControlAcquisition acquisition = new ExclusiveControlAcquisition(Thread.currentThread());
+        outward.whenComplete((ignored, completionFailure) -> {
+            if (outward.isCancelled()) {
+                acquisition.cancel();
+            }
+        });
         boolean acquired = false;
         Throwable failure = null;
         try {
-            acquired = activeGate.tryAcquireExclusive(
-                    acquisitionTimeout,
-                    activeUnit,
-                    outward::isCancelled);
+            try {
+                acquired = activeGate.tryAcquireExclusive(acquisitionTimeout, activeUnit);
+            } finally {
+                acquisition.stopWaiting();
+            }
             if (!acquired) {
                 if (!outward.isCancelled()) {
                     failure = new TimeoutException("Timed out waiting for exclusive Iris generation control after "
@@ -1138,7 +1148,9 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
                 activeOperation.run();
             }
         } catch (InterruptedException e) {
+            if (!acquisition.interruptedByCancellation()) {
                 Thread.currentThread().interrupt();
+            }
             if (!outward.isCancelled()) {
                 failure = e;
             }
@@ -1447,30 +1459,12 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
             permits.acquire(permitCount);
         }
 
-        boolean tryAcquireExclusive(
-                long timeout,
-                TimeUnit unit,
-                BooleanSupplier cancelled
-        ) throws InterruptedException {
+        boolean tryAcquireExclusive(long timeout, TimeUnit unit) throws InterruptedException {
             if (timeout <= 0L) {
                 throw new IllegalArgumentException("Exclusive generation control timeout must be positive.");
             }
             TimeUnit activeUnit = Objects.requireNonNull(unit, "Exclusive generation control timeout unit");
-            BooleanSupplier cancellation = Objects.requireNonNull(cancelled, "Exclusive generation control cancellation");
-            long timeoutNanos = activeUnit.toNanos(timeout);
-            long started = System.nanoTime();
-            long remainingNanos = timeoutNanos;
-            long cancellationPollNanos = TimeUnit.MILLISECONDS.toNanos(50L);
-            while (!cancellation.getAsBoolean() && remainingNanos > 0L) {
-                if (permits.tryAcquire(
-                        permitCount,
-                        Math.min(remainingNanos, cancellationPollNanos),
-                        TimeUnit.NANOSECONDS)) {
-                    return true;
-                }
-                remainingNanos = timeoutNanos - (System.nanoTime() - started);
-            }
-            return false;
+            return permits.tryAcquire(permitCount, timeout, activeUnit);
         }
 
         void releaseExclusive() {
@@ -1491,6 +1485,34 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
         }
     }
 
+    private static final class ExclusiveControlAcquisition {
+        private final Thread waiter;
+        private boolean waiting = true;
+        private boolean cancellationInterrupt;
+
+        private ExclusiveControlAcquisition(Thread waiter) {
+            this.waiter = waiter;
+        }
+
+        private synchronized void cancel() {
+            if (waiting && !waiter.isInterrupted()) {
+                cancellationInterrupt = true;
+                waiter.interrupt();
+            }
+        }
+
+        private synchronized void stopWaiting() {
+            waiting = false;
+            if (cancellationInterrupt) {
+                Thread.interrupted();
+            }
+        }
+
+        private synchronized boolean interruptedByCancellation() {
+            return cancellationInterrupt;
+        }
+    }
+
     static final class GenerationStageExclusivePermit implements AutoCloseable {
         private final Semaphore permits;
         private final int permitCount;

core/src/main/java/art/arcane/iris/platform/bukkit/BukkitBlockState.java

@@ -18,14 +18,24 @@
 
 package art.arcane.iris.platform.bukkit;
 
+import art.arcane.iris.core.link.Identifier;
 import art.arcane.iris.core.nms.INMS;
+import art.arcane.iris.core.nms.container.Pair;
+import art.arcane.iris.core.service.ExternalDataSVC;
+import art.arcane.iris.engine.object.IrisObjectRotation;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.iris.util.common.data.IrisCustomData;
+import art.arcane.iris.util.common.math.IrisBlockVector;
+import art.arcane.volmlib.util.collection.KMap;
+import org.bukkit.Axis;
 import org.bukkit.Bukkit;
 import org.bukkit.Tag;
+import org.bukkit.block.BlockFace;
 import org.bukkit.block.data.BlockData;
 
 import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -33,6 +43,15 @@ import java.util.concurrent.ConcurrentHashMap;
  * Interned Bukkit adapter for a neutral block state backed by BlockData.
  */
 public final class BukkitBlockState implements PlatformBlockState {
+    private static final Map<String, BlockFace> CUSTOM_NAMED_FACES = Map.of(
+            "north", BlockFace.NORTH, "south", BlockFace.SOUTH,
+            "east", BlockFace.EAST, "west", BlockFace.WEST,
+            "up", BlockFace.UP, "down", BlockFace.DOWN);
+    private static final List<BlockFace> CUSTOM_ROTATION_FACES = List.of(
+            BlockFace.SOUTH, BlockFace.SOUTH_SOUTH_WEST, BlockFace.SOUTH_WEST, BlockFace.WEST_SOUTH_WEST,
+            BlockFace.WEST, BlockFace.WEST_NORTH_WEST, BlockFace.NORTH_WEST, BlockFace.NORTH_NORTH_WEST,
+            BlockFace.NORTH, BlockFace.NORTH_NORTH_EAST, BlockFace.NORTH_EAST, BlockFace.EAST_NORTH_EAST,
+            BlockFace.EAST, BlockFace.EAST_SOUTH_EAST, BlockFace.SOUTH_EAST, BlockFace.SOUTH_SOUTH_EAST);
     private static final ConcurrentHashMap<String, BukkitBlockState> CACHE = new ConcurrentHashMap<>();
     // Front cache keyed on the BlockData itself (CraftBlockData equals/hashCode delegate to
     // the canonical NMS state): a hit skips getAsString(), which built the full property
@@ -82,6 +101,64 @@ public final class BukkitBlockState implements PlatformBlockState {
         return state;
     }
 
+    public static BlockData rotateCustomData(IrisObjectRotation objectRotation, IrisCustomData custom, int spinxx, int spinyy, int spinzz) {
+        Pair<Identifier, KMap<String, String>> parsed = ExternalDataSVC.parseState(custom.getCustom());
+        KMap<String, String> original = parsed.getB();
+        if (original.isEmpty()) {
+            return null;
+        }
+        KMap<String, String> rotated = new KMap<>(original);
+        int spinx = (int) (90D * Math.ceil(Math.abs((spinxx % 360D) / 90D)));
+        int spiny = (int) (90D * Math.ceil(Math.abs((spinyy % 360D) / 90D)));
+        int spinz = (int) (90D * Math.ceil(Math.abs((spinzz % 360D) / 90D)));
+        boolean oriented = false;
+        String facing = original.get("facing");
+        if (facing != null && CUSTOM_NAMED_FACES.containsKey(facing)) {
+            BlockFace face = objectRotation.getFace(rotateFace(objectRotation, CUSTOM_NAMED_FACES.get(facing), spinx, spiny, spinz));
+            rotated.put("facing", face.name().toLowerCase(Locale.ROOT));
+            oriented = true;
+        }
+        Axis axis = switch (original.getOrDefault("axis", "")) {
+            case "x" -> Axis.X;
+            case "y" -> Axis.Y;
+            case "z" -> Axis.Z;
+            default -> null;
+        };
+        if (axis != null) {
+            Axis result = objectRotation.getAxis(rotateFace(objectRotation, objectRotation.faceForAxis(axis), spinx, spiny, spinz));
+            rotated.put("axis", result.name().toLowerCase(Locale.ROOT));
+            oriented = true;
+        }
+        int rotation = rotationIndex(original.get("rotation"));
+        if (rotation >= 0) {
+            BlockFace face = objectRotation.getHexFace(rotateFace(objectRotation, CUSTOM_ROTATION_FACES.get(rotation), spinx, spiny, spinz));
+            int result = CUSTOM_ROTATION_FACES.indexOf(face);
+            if (result >= 0) {
+                rotated.put("rotation", Integer.toString(result));
+            }
+            oriented = true;
+        }
+        for (Map.Entry<String, BlockFace> entry : CUSTOM_NAMED_FACES.entrySet()) {
+            String value = original.get(entry.getKey());
+            if (value == null) {
+                continue;
+            }
+            String destination = objectRotation.getFace(rotateFace(objectRotation, entry.getValue(), spinx, spiny, spinz)).name().toLowerCase(Locale.ROOT);
+            if (original.containsKey(destination)) {
+                rotated.put(destination, value);
+            }
+            oriented = true;
+        }
+        if (!oriented) {
+            return null;
+        }
+        if (rotated.equals(original)) {
+            return custom;
+        }
+        BlockData resolved = BukkitBlockResolution.resolveOrNull(ExternalDataSVC.buildState(parsed.getA(), rotated).toString());
+        return resolved instanceof IrisCustomData ? resolved : custom;
+    }
+
     @Override
     public boolean equals(Object other) {
         if (this == other) {
@@ -369,9 +446,17 @@ public final class BukkitBlockState implements PlatformBlockState {
 
     @Override
     public PlatformBlockState withProperty(String name, String value) {
+        if (data instanceof IrisCustomData custom) {
+            if (ExternalDataSVC.parseState(custom.getCustom()).getB().containsKey(name)) {
+                String merged = mergeProperty(key, name, value);
+                BlockData resolved = BukkitBlockResolution.resolveOrNull(merged);
+                if (!(resolved instanceof IrisCustomData)) {
+                    throw new IllegalArgumentException("Cannot resolve custom block state " + merged);
+                }
+                return of(resolved);
+            }
             // Re-attach the custom identity (as the proxy's own merge/clone cases do) after
             // editing the base block, so auto-waterlogging cannot turn custom blocks into vanilla.
-        if (data instanceof IrisCustomData custom) {
             String merged = mergeProperty(custom.getBase().getAsString(), name, value);
             BlockData resolved = Bukkit.createBlockData(merged);
             return of(IrisCustomData.of(resolved, custom.getCustom()));
@@ -383,4 +468,20 @@ public final class BukkitBlockState implements PlatformBlockState {
     public Object nativeHandle() {
         return data;
     }
+
+    private static IrisBlockVector rotateFace(IrisObjectRotation objectRotation, BlockFace face, int spinx, int spiny, int spinz) {
+        return objectRotation.rotate(new IrisBlockVector(face.getModX(), face.getModY(), face.getModZ()), spinx, spiny, spinz);
+    }
+
+    private static int rotationIndex(String value) {
+        if (value == null) {
+            return -1;
+        }
+        try {
+            int rotation = Integer.parseInt(value);
+            return rotation >= 0 && rotation < CUSTOM_ROTATION_FACES.size() ? rotation : -1;
+        } catch (NumberFormatException ignored) {
+            return -1;
+        }
+    }
 }

core/src/test/java/art/arcane/iris/core/service/BoardSVCSavedBiomeTest.java

@@ -7,6 +7,8 @@ import art.arcane.iris.core.tools.IrisToolbelt;
 import art.arcane.iris.engine.IrisComplex;
 import art.arcane.iris.engine.framework.BiomeEnvironment;
 import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.GenerationSessionManager;
+import art.arcane.iris.engine.framework.GenerationTransitionGate;
 import art.arcane.iris.engine.history.SavedBiomeUnavailableException;
 import art.arcane.iris.engine.mantle.EngineMantle;
 import art.arcane.iris.engine.object.IrisBiome;
@@ -35,7 +37,14 @@ import org.mockito.MockedStatic;
 
 import java.lang.reflect.Field;
 import java.util.ArrayDeque;
+import java.util.List;
 import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -195,6 +204,70 @@ public class BoardSVCSavedBiomeTest {
         }
     }
 
+    @Test
+    public void ordinaryRefreshLeavesOwnerThreadAvailableForStudioCheckpoint() throws Exception {
+        GenerationSessionManager sessions = new GenerationSessionManager(true);
+        AtomicInteger height = new AtomicInteger(70);
+        AtomicInteger checkpoints = new AtomicInteger();
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        ExecutorService reloader = Executors.newSingleThreadExecutor();
+        Fixture fixture = null;
+        try {
+            fixture = owner.submit(() -> {
+                Fixture created = new Fixture();
+                when(created.engine.getGenerationSessions()).thenReturn(sessions);
+                when(created.engine.getHeight(8, 8)).thenAnswer(invocation -> {
+                    try (GenerationTransitionGate.Participation ignored = sessions.transitionGate().enter()) {
+                        return height.get();
+                    }
+                });
+                created.service.updatePlayer(created.player);
+                return created;
+            }).get(3L, TimeUnit.SECONDS);
+            Fixture board = fixture;
+            List<String> previous = board.service.getLines(board.player);
+            assertTrue(board.lines().contains("70"));
+
+            CompletableFuture<Void> cutover = CompletableFuture.runAsync(() -> {
+                try (GenerationTransitionGate.Transition ignored = sessions.transitionGate().beginTransition(2_000L)) {
+                    sessions.sealAndAwait("Studio generation cutover", 2_000L);
+                    Future<?> refresh = owner.submit(board::tick);
+                    owner.submit(checkpoints::incrementAndGet).get(2L, TimeUnit.SECONDS);
+                    refresh.get(2L, TimeUnit.SECONDS);
+                    assertEquals(previous, board.service.getLines(board.player));
+                    verify(board.engine, times(2)).getGeneratedPerSecond();
+                    verify(board.engine, times(1)).getBiomeOrMantleEnvironment(8, 160, 8);
+                    verify(board.engine, times(1)).getHeight(8, 8);
+                    height.set(85);
+                    sessions.activateNextSession();
+                } catch (Exception failure) {
+                    throw new IllegalStateException(failure);
+                }
+            }, reloader);
+            cutover.get(3L, TimeUnit.SECONDS);
+
+            assertEquals(1, checkpoints.get());
+            owner.submit(board::tick).get(2L, TimeUnit.SECONDS);
+            assertTrue(board.lines().contains("85"));
+            assertEquals(1, board.ticks.size());
+            assertEquals(0, sessions.activeLeases());
+            verify(board.engine, times(2)).getBiomeOrMantleEnvironment(8, 160, 8);
+            verify(board.engine, times(2)).getHeight(8, 8);
+        } finally {
+            try {
+                if (fixture != null) {
+                    Fixture board = fixture;
+                    owner.submit(board::close).get(2L, TimeUnit.SECONDS);
+                }
+            } finally {
+                owner.shutdownNow();
+                reloader.shutdownNow();
+                assertTrue(owner.awaitTermination(2L, TimeUnit.SECONDS));
+                assertTrue(reloader.awaitTermination(2L, TimeUnit.SECONDS));
+            }
+        }
+    }
+
     private static BiomeEnvironment environment(String regionName, String biomeName) {
         IrisRegion region = mock(IrisRegion.class);
         IrisBiome biome = mock(IrisBiome.class);

core/src/test/java/art/arcane/iris/core/service/ExternalDataSVCBlockRoutingTest.java

@@ -15,6 +15,7 @@ import org.junit.Test;
 import java.lang.reflect.Field;
 import java.util.List;
 import java.util.MissingResourceException;
+import java.util.Optional;
 import java.util.Set;
 
 import static org.junit.Assert.assertEquals;
@@ -29,6 +30,43 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 public class ExternalDataSVCBlockRoutingTest {
+    @Test
+    public void directPlacementRetainsQualifiedProviderAndProperties() throws Exception {
+        Identifier nativeId = Identifier.fromString("default:palm_log");
+        Identifier stateId = Identifier.fromString("default:palm_log[axis=x]");
+        ExternalDataProvider provider = provider("CraftEngine", nativeId);
+        Block block = mock(Block.class);
+        when(provider.placeBlock(block, stateId)).thenReturn(true);
+
+        assertEquals(true, service(provider).placeBlock(block,
+                Identifier.fromString("craftengine:default/palm_log[axis=x]")));
+        verify(provider).placeBlock(block, stateId);
+    }
+
+    @Test
+    public void capturedBlocksRetainSemanticPropertiesAndProviderIdentity() throws Exception {
+        Identifier id = Identifier.fromString("example:palm_log[axis=x]");
+        ExternalDataProvider provider = provider("CraftEngine", id);
+        BlockData base = mock(BlockData.class);
+        when(base.getAsString()).thenReturn("craftengine:custom_18");
+        when(provider.identifyBlock(base)).thenReturn(Optional.of(id));
+        ExternalDataSVC service = service(provider);
+
+        IrisCustomData captured = (IrisCustomData) service.captureBlockData(base);
+
+        assertSame(base, captured.getBase());
+        assertEquals("craftengine:example/palm_log[axis=x]", captured.getCustom().toString());
+        assertSame(captured, service.captureBlockData(captured));
+    }
+
+    @Test
+    public void vanillaCaptureKeepsOriginalBlockData() throws Exception {
+        ExternalDataProvider provider = provider("CraftEngine", Identifier.fromString("example:wood"));
+        BlockData base = mock(BlockData.class);
+
+        assertSame(base, service(provider).captureBlockData(base));
+    }
+
     @Test
     public void nativeLookupPinsProviderAndRetainsPropertiesUntilPlacement() throws Exception {
         Identifier nativeId = Identifier.fromString("example:wood");

core/src/test/java/art/arcane/iris/core/service/ObjectSVCUndoCustomBlockTest.java

@@ -0,0 +1,67 @@
+package art.arcane.iris.core.service;
+
+import art.arcane.iris.core.link.Identifier;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.util.common.data.IrisCustomData;
+import art.arcane.iris.util.common.scheduling.J;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.data.BlockData;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+public class ObjectSVCUndoCustomBlockTest {
+    @Test
+    public void undoRestoresSemanticCustomStateOnItsOwningRegion() {
+        Block block = mock(Block.class);
+        Location location = new Location(mock(World.class), 7, 80, -9);
+        when(block.getLocation()).thenReturn(location);
+        Identifier id = new Identifier("craftengine", "test/lamp[lit=false]");
+        BlockData custom = IrisCustomData.of(mock(BlockData.class), id);
+        ExternalDataSVC external = mock(ExternalDataSVC.class);
+        when(external.placeBlock(block, id)).thenReturn(true);
+        List<Runnable> ownerTasks = new ArrayList<>();
+        try (MockedStatic<IrisServices> services = mockStatic(IrisServices.class);
+             MockedStatic<J> scheduling = mockStatic(J.class)) {
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(external);
+            scheduling.when(() -> J.runGlobal(any(Runnable.class))).thenAnswer(invocation -> {
+                invocation.getArgument(0, Runnable.class).run();
+                return true;
+            });
+            scheduling.when(() -> J.s(any(Runnable.class))).thenAnswer(invocation -> {
+                invocation.getArgument(0, Runnable.class).run();
+                return null;
+            });
+            scheduling.when(() -> J.runAt(any(Location.class), any(Runnable.class))).thenAnswer(invocation -> {
+                ownerTasks.add(invocation.getArgument(1, Runnable.class));
+                return true;
+            });
+            ObjectSVC undo = new ObjectSVC();
+            undo.addChanges(new HashMap<>(Map.of(block, custom)));
+
+            undo.revertChanges(1);
+
+            assertEquals(1, ownerTasks.size());
+            verifyNoInteractions(external);
+            ownerTasks.getFirst().run();
+            verify(external).placeBlock(block, id);
+            verify(block, times(0)).setBlockData(any(BlockData.class), anyBoolean());
+        }
+    }
+}

core/src/test/java/art/arcane/iris/engine/EngineRuntimeBuilderStudioServiceTest.java

@@ -0,0 +1,287 @@
+package art.arcane.iris.engine;
+
+import art.arcane.iris.engine.framework.Engine;
+import art.arcane.iris.engine.framework.EngineAssignedWorldManager;
+import art.arcane.iris.engine.framework.EngineEffects;
+import art.arcane.iris.engine.framework.EngineEffectsProvider;
+import art.arcane.iris.engine.framework.EngineTarget;
+import art.arcane.iris.engine.framework.EngineWorldManagerProvider;
+import art.arcane.iris.engine.framework.GenerationSessionManager;
+import art.arcane.iris.engine.framework.GenerationTransitionGate;
+import art.arcane.iris.engine.object.IrisWorld;
+import art.arcane.iris.platform.bukkit.BukkitPlatform;
+import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
+import art.arcane.iris.spi.IrisServices;
+import org.bukkit.Chunk;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.entity.Player;
+import org.bukkit.event.block.BlockBreakEvent;
+import org.bukkit.event.block.BlockPlaceEvent;
+import org.bukkit.event.player.PlayerTeleportEvent;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.lang.reflect.Field;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.same;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class EngineRuntimeBuilderStudioServiceTest {
+    @Test
+    public void replacementInterceptsCommandsWhileOldManagerRetires() throws Exception {
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        try (Fixture fixture = new Fixture()) {
+            CompletableFuture<Boolean> teleport = new CompletableFuture<>();
+            AtomicInteger requests = new AtomicInteger();
+            fixture.previous.afterUnregister = () -> {
+                try {
+                    owner.submit(() -> fixture.teleportDuringRetirement(teleport, requests))
+                            .get(2L, TimeUnit.SECONDS);
+                } catch (Exception failure) {
+                    throw new IllegalStateException(failure);
+                }
+            };
+
+            try (GenerationTransitionGate.Transition ignored = fixture.sessions.transitionGate().beginTransition(2_000L)) {
+                fixture.sessions.sealAndAwait("Studio generation cutover", 2_000L);
+                fixture.builder.refreshStudioRuntimeServices();
+            }
+
+            assertSame(fixture.replacement, fixture.engine.runtime.worldManager());
+            assertEquals(List.of(fixture.replacement), fixture.registered);
+            assertEquals(1, requests.get());
+            assertFalse(teleport.isDone());
+            assertTrue(teleport.complete(true));
+            fixture.previous.tick.run();
+            fixture.replacement.tick.run();
+            assertEquals(0, fixture.previous.updates);
+            assertEquals(1, fixture.replacement.updates);
+            verify(fixture.previousEffects).close();
+            verify(fixture.nextEffects, never()).close();
+        } finally {
+            owner.shutdownNow();
+            assertTrue(owner.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void failedReplacementStartKeepsThePreviousListenerRegistered() throws Exception {
+        try (Fixture fixture = new Fixture()) {
+            fixture.replacement.failRegistration = true;
+            EngineRuntime previous = fixture.engine.runtime;
+            try (GenerationTransitionGate.Transition ignored = fixture.sessions.transitionGate().beginTransition(2_000L)) {
+                fixture.sessions.sealAndAwait("Studio generation cutover", 2_000L);
+
+                assertThrows(IllegalStateException.class, fixture.builder::refreshStudioRuntimeServices);
+            }
+
+            assertSame(previous, fixture.engine.runtime);
+            assertEquals(List.of(fixture.previous), fixture.registered);
+            assertEquals(0, fixture.previous.closes);
+            assertEquals(1, fixture.replacement.closes);
+            assertEquals(1L, fixture.sessions.currentSessionId());
+            verify(fixture.previousEffects, never()).close();
+            verify(fixture.nextEffects).close();
+        }
+    }
+
+    private static final class Fixture implements AutoCloseable {
+        private final IrisEngine engine = mock(IrisEngine.class);
+        private final GenerationSessionManager sessions = new GenerationSessionManager(true);
+        private final AtomicBoolean closing = new AtomicBoolean(true);
+        private final List<TestWorldManager> registered = new CopyOnWriteArrayList<>();
+        private final EngineEffects previousEffects = mock(EngineEffects.class);
+        private final EngineEffects nextEffects = mock(EngineEffects.class);
+        private final IrisWorld irisWorld = mock(IrisWorld.class);
+        private final World world = mock(World.class);
+        private final TestWorldManager previous;
+        private final TestWorldManager replacement;
+        private final EngineRuntimeBuilder builder;
+        private final MockedStatic<IrisServices> services;
+
+        private Fixture() throws Exception {
+            EngineTarget target = mock(EngineTarget.class);
+            when(engine.getTarget()).thenReturn(target);
+            when(target.getWorld()).thenReturn(irisWorld);
+            when(engine.isStudio()).thenReturn(true);
+            when(engine.isClosing()).thenAnswer(invocation -> closing.get());
+            when(engine.isShuttingDown()).thenCallRealMethod();
+            when(engine.getClosing()).thenReturn(closing);
+            when(engine.getGenerationSessions()).thenReturn(sessions);
+            engine.lifecycleState = IrisEngine.LifecycleState.HOTLOADING;
+            EngineBackgroundTasks background = mock(EngineBackgroundTasks.class);
+            when(background.scheduleTrackedTask(any(Runnable.class))).thenReturn(true);
+            Field backgroundField = IrisEngine.class.getDeclaredField("backgroundTasks");
+            backgroundField.setAccessible(true);
+            backgroundField.set(engine, background);
+            previous = new TestWorldManager(engine, registered);
+            replacement = new TestWorldManager(engine, registered);
+            engine.runtime = new EngineRuntime(mock(GenerationRuntime.class), previousEffects, previous);
+            previous.start();
+            builder = new EngineRuntimeBuilder(engine);
+            EngineEffectsProvider effectsProvider = mock(EngineEffectsProvider.class);
+            EngineWorldManagerProvider managerProvider = mock(EngineWorldManagerProvider.class);
+            when(effectsProvider.create(engine)).thenReturn(nextEffects);
+            when(managerProvider.create(engine)).thenReturn(replacement);
+            services = mockStatic(IrisServices.class);
+            services.when(() -> IrisServices.get(EngineEffectsProvider.class)).thenReturn(effectsProvider);
+            services.when(() -> IrisServices.get(EngineWorldManagerProvider.class)).thenReturn(managerProvider);
+        }
+
+        private void teleportDuringRetirement(CompletableFuture<Boolean> teleport, AtomicInteger requests) {
+            Player player = mock(Player.class);
+            Location destination = new Location(world, 1024.5D, 309D, 0.5D, 45F, 10F);
+            PlayerTeleportEvent event = new PlayerTeleportEvent(player,
+                    new Location(world, 0.5D, 100D, 0.5D), destination,
+                    PlayerTeleportEvent.TeleportCause.COMMAND);
+            try (MockedStatic<BukkitPlatform> platform = mockStatic(BukkitPlatform.class);
+                 MockedStatic<BukkitWorldBinding> binding = mockStatic(BukkitWorldBinding.class)) {
+                platform.when(BukkitPlatform::isPaperServer).thenReturn(true);
+                binding.when(() -> BukkitWorldBinding.world(irisWorld)).thenReturn(world);
+                platform.when(() -> BukkitPlatform.teleportAsync(same(player), any(Location.class),
+                                eq(PlayerTeleportEvent.TeleportCause.COMMAND)))
+                        .thenAnswer(invocation -> {
+                            assertTrue(event.isCancelled());
+                            Location requested = invocation.getArgument(1, Location.class);
+                            assertEquals(destination, requested);
+                            assertNotSame(destination, requested);
+                            requests.incrementAndGet();
+                            return teleport;
+                        });
+                assertEquals(List.of(replacement), registered);
+                for (TestWorldManager manager : registered) {
+                    if (!event.isCancelled()) {
+                        manager.on(event);
+                    }
+                }
+                assertTrue(event.isCancelled());
+                previous.tick.run();
+                replacement.tick.run();
+                assertEquals(0, previous.updates);
+                assertEquals(0, replacement.updates);
+                assertEquals(0, sessions.activeLeases());
+            }
+        }
+
+        @Override
+        public void close() {
+            previous.afterUnregister = null;
+            previous.close();
+            replacement.close();
+            services.close();
+        }
+    }
+
+    private static final class TestWorldManager extends EngineAssignedWorldManager {
+        private final List<TestWorldManager> registered;
+        private final WorldTeleportWarmup warmup = new WorldTeleportWarmup();
+        private Runnable tick;
+        private Runnable afterUnregister;
+        private boolean failRegistration;
+        private int updates;
+        private int closes;
+
+        private TestWorldManager(Engine engine, List<TestWorldManager> registered) {
+            super(engine);
+            this.registered = registered;
+        }
+
+        @Override
+        public void close() {
+            closes++;
+            super.close();
+        }
+
+        @Override
+        protected void registerManagerListener() {
+            registered.add(this);
+            if (failRegistration) {
+                throw new IllegalStateException("listener registration failed");
+            }
+        }
+
+        @Override
+        protected void unregisterManagerListener() {
+            registered.remove(this);
+            if (afterUnregister != null) {
+                afterUnregister.run();
+            }
+        }
+
+        @Override
+        protected int scheduleManagerTick(Runnable tick) {
+            this.tick = tick;
+            return 42;
+        }
+
+        @Override
+        protected void cancelManagerTick(int scheduledTaskId) {
+        }
+
+        @Override
+        public int getEntityCount() {
+            return 0;
+        }
+
+        @Override
+        public int getChunkCount() {
+            return 0;
+        }
+
+        @Override
+        public double getEntitySaturation() {
+            return 0D;
+        }
+
+        @Override
+        public void onTick() {
+            updates++;
+        }
+
+        @Override
+        public void onSave() {
+        }
+
+        @Override
+        public void onBlockBreak(BlockBreakEvent event) {
+        }
+
+        @Override
+        public void onBlockPlace(BlockPlaceEvent event) {
+        }
+
+        @Override
+        public void onChunkLoad(Chunk chunk, boolean generated) {
+        }
+
+        @Override
+        public void onChunkUnload(Chunk chunk) {
+        }
+
+        @Override
+        public void teleportAsync(PlayerTeleportEvent event) {
+            warmup.teleportAsync(event);
+        }
+    }
+}

core/src/test/java/art/arcane/iris/engine/IrisEngineLifecycleGateTest.java

@@ -6,8 +6,38 @@ import java.util.concurrent.TimeoutException;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class IrisEngineLifecycleGateTest {
+    @Test
+    public void studioSessionSealDoesNotMeanWorldShutdown() {
+        IrisEngine engine = mock(IrisEngine.class);
+        when(engine.isShuttingDown()).thenCallRealMethod();
+        when(engine.isClosing()).thenReturn(true);
+        engine.lifecycleState = IrisEngine.LifecycleState.HOTLOADING;
+
+        assertTrue(engine.isClosing());
+        assertFalse(engine.isShuttingDown());
+
+        engine.lifecycleState = IrisEngine.LifecycleState.CLOSING;
+        assertTrue(engine.isShuttingDown());
+        engine.lifecycleState = IrisEngine.LifecycleState.CLOSED;
+        assertTrue(engine.isShuttingDown());
+        engine.lifecycleState = IrisEngine.LifecycleState.FAILED;
+        assertTrue(engine.isShuttingDown());
+    }
+
+    @Test
+    public void closedWorldRejectsNavigationRegardlessOfLifecyclePublication() {
+        IrisEngine engine = mock(IrisEngine.class);
+        when(engine.isShuttingDown()).thenCallRealMethod();
+        engine.lifecycleState = IrisEngine.LifecycleState.RUNNING;
+        engine.closed = true;
+
+        assertTrue(engine.isShuttingDown());
+    }
+
     @Test
     public void incompleteBackgroundDrainBlocksResourceRelease() {
         EngineBackgroundTasks.BackgroundTaskDrain drain = new EngineBackgroundTasks.BackgroundTaskDrain(

core/src/test/java/art/arcane/iris/engine/framework/EngineAssignedWorldManagerTeleportTest.java

@@ -12,10 +12,20 @@ import org.bukkit.event.player.PlayerTeleportEvent;
 import org.junit.Test;
 import org.mockito.MockedStatic;
 
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 public class EngineAssignedWorldManagerTeleportTest {
@@ -30,6 +40,68 @@ public class EngineAssignedWorldManagerTeleportTest {
         }
     }
 
+    @Test
+    public void commandTeleportStillConvertsDuringSealedStudioCutover() throws Exception {
+        ExecutorService reloader = Executors.newSingleThreadExecutor();
+        CountDownLatch entered = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        try (TeleportHarness harness = new TeleportHarness(false, true)) {
+            when(harness.engine.isClosing()).thenReturn(true);
+            when(harness.engine.isShuttingDown()).thenReturn(false);
+            Location destination = harness.event.getTo();
+            Future<?> cutover = reloader.submit(() -> {
+                try (GenerationTransitionGate.Transition ignored = harness.sessions.transitionGate().beginTransition(2_000L)) {
+                    harness.sessions.sealAndAwait("Studio generation cutover", 2_000L);
+                    entered.countDown();
+                    assertTrue(release.await(2L, TimeUnit.SECONDS));
+                    harness.sessions.activateNextSession();
+                } catch (Exception failure) {
+                    throw new IllegalStateException(failure);
+                }
+            });
+            assertTrue(entered.await(2L, TimeUnit.SECONDS));
+
+            harness.manager.on(harness.event);
+
+            assertSame(harness.event, harness.manager.teleportEvent);
+            assertSame(destination, harness.manager.teleportEvent.getTo());
+            assertEquals(PlayerTeleportEvent.TeleportCause.COMMAND, harness.manager.teleportEvent.getCause());
+            assertEquals(0, harness.sessions.activeLeases());
+            release.countDown();
+            cutover.get(2L, TimeUnit.SECONDS);
+        } finally {
+            release.countDown();
+            reloader.shutdownNow();
+            assertTrue(reloader.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void closingStudioCancelsCommandInsteadOfFallingThroughToVanilla() {
+        try (TeleportHarness harness = new TeleportHarness(false, true)) {
+            when(harness.engine.isClosing()).thenReturn(true);
+            when(harness.engine.isShuttingDown()).thenReturn(true);
+
+            harness.manager.on(harness.event);
+
+            verify(harness.event).setCancelled(true);
+            assertNull(harness.manager.teleportEvent);
+        }
+    }
+
+    @Test
+    public void closedStudioCancelsEvenAnAlreadyLoadedDestination() {
+        try (TeleportHarness harness = new TeleportHarness(true, true)) {
+            when(harness.engine.isClosed()).thenReturn(true);
+            when(harness.engine.isShuttingDown()).thenReturn(true);
+
+            harness.manager.on(harness.event);
+
+            verify(harness.event).setCancelled(true);
+            assertNull(harness.manager.teleportEvent);
+        }
+    }
+
     @Test
     public void loadedIrisDestinationContinuesWithoutInterception() {
         TeleportHarness harness = new TeleportHarness(true, true);
@@ -80,16 +152,20 @@ public class EngineAssignedWorldManagerTeleportTest {
     public void otherWorldDestinationContinuesWithoutInterception() {
         TeleportHarness harness = new TeleportHarness(false, true);
         World otherWorld = mock(World.class);
+        when(harness.engine.isClosing()).thenReturn(true);
+        when(harness.engine.isShuttingDown()).thenReturn(true);
         when(harness.event.getTo()).thenReturn(new Location(otherWorld, 400.5D, 96D, 2.5D));
 
         try (harness) {
             harness.manager.on(harness.event);
 
             assertNull(harness.manager.teleportEvent);
+            verify(harness.event, never()).setCancelled(true);
         }
     }
 
     private static final class TeleportHarness implements AutoCloseable {
+        private final GenerationSessionManager sessions = new GenerationSessionManager(true);
         private final Engine engine;
         private final TestWorldManager manager;
         private final PlayerTeleportEvent event;
@@ -106,6 +182,7 @@ public class EngineAssignedWorldManagerTeleportTest {
 
             when(engine.getTarget()).thenReturn(target);
             when(engine.isStudio()).thenReturn(true);
+            when(engine.getGenerationSessions()).thenReturn(sessions);
             when(target.getWorld()).thenReturn(irisWorld);
             when(event.getTo()).thenReturn(destination);
             when(event.getCause()).thenReturn(PlayerTeleportEvent.TeleportCause.COMMAND);
@@ -116,10 +193,12 @@ public class EngineAssignedWorldManagerTeleportTest {
             binding = mockStatic(BukkitWorldBinding.class);
             binding.when(() -> BukkitWorldBinding.world(irisWorld)).thenReturn(world);
             manager = new TestWorldManager(engine);
+            manager.start();
         }
 
         @Override
         public void close() {
+            manager.close();
             binding.close();
             platform.close();
         }
@@ -133,9 +212,20 @@ public class EngineAssignedWorldManagerTeleportTest {
         }
 
         @Override
-        protected boolean runManagerTask(String operation, Runnable task) {
-            task.run();
-            return true;
+        protected void registerManagerListener() {
+        }
+
+        @Override
+        protected int scheduleManagerTick(Runnable tick) {
+            return 0;
+        }
+
+        @Override
+        protected void unregisterManagerListener() {
+        }
+
+        @Override
+        protected void cancelManagerTick(int scheduledTaskId) {
         }
 
         @Override

core/src/test/java/art/arcane/iris/engine/history/BoundarySamplingConcurrencyTest.java

@@ -0,0 +1,224 @@
+package art.arcane.iris.engine.history;
+
+import art.arcane.iris.testsupport.DurabilityMode;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.lang.reflect.Field;
+import java.util.AbstractList;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.OptionalInt;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class BoundarySamplingConcurrencyTest {
+    private static final BoundaryColumnGeometry GEOMETRY = new BoundaryColumnGeometry(0,
+            List.of(new BoundaryColumnGeometry.Voxel("minecraft:stone", BoundaryColumnGeometry.Phase.SOLID,
+                    "", false)), new int[]{65}, new short[]{0});
+
+    @ClassRule
+    public static final DurabilityMode DURABILITY = DurabilityMode.relaxed();
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void simultaneousQueriesBuildOneCandidateIndex() throws Exception {
+        TerrainBoundarySignatureStore.Snapshot snapshot = mock(TerrainBoundarySignatureStore.Snapshot.class);
+        CountDownLatch scanning = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        when(snapshot.nearestCandidatesForChunk(0, 0, 32)).thenAnswer(invocation -> {
+            scanning.countDown();
+            assertTrue(release.await(5, TimeUnit.SECONDS));
+            return List.of(signature(0, 0));
+        });
+        TransitionBoundarySampler sampler = new TransitionBoundarySampler(32, snapshot);
+        ExecutorService workers = Executors.newFixedThreadPool(8);
+        CyclicBarrier start = new CyclicBarrier(8);
+        List<Future<BoundaryGeometryInfluence>> queries = new ArrayList<>();
+        try {
+            for (int index = 0; index < 8; index++) {
+                queries.add(workers.submit(() -> {
+                    start.await(5, TimeUnit.SECONDS);
+                    return sampler.geometryAt(1, 1);
+                }));
+            }
+            assertTrue(scanning.await(5, TimeUnit.SECONDS));
+            release.countDown();
+            BoundaryGeometryInfluence expected = queries.getFirst().get(5, TimeUnit.SECONDS);
+            for (Future<BoundaryGeometryInfluence> query : queries) {
+                assertEquals(expected, query.get(5, TimeUnit.SECONDS));
+            }
+            verify(snapshot, times(1)).nearestCandidatesForChunk(0, 0, 32);
+            assertEquals(1L, sampler.candidateBuildCount());
+        } finally {
+            release.countDown();
+            workers.shutdownNow();
+            assertTrue(workers.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void failedCandidateBuildCanBeRetried() {
+        TerrainBoundarySignatureStore.Snapshot snapshot = mock(TerrainBoundarySignatureStore.Snapshot.class);
+        when(snapshot.nearestCandidatesForChunk(0, 0, 32))
+                .thenThrow(new IllegalStateException("Unavailable boundary shard"))
+                .thenReturn(List.of(signature(0, 0)));
+        TransitionBoundarySampler sampler = new TransitionBoundarySampler(32, snapshot);
+
+        assertThrows(IllegalStateException.class, () -> sampler.sample(1, 1));
+        assertEquals(64D, sampler.sample(1, 1).historicalSurfaceHeight(), 0D);
+        verify(snapshot, times(2)).nearestCandidatesForChunk(0, 0, 32);
+    }
+
+    @Test
+    public void generationWindowReusesCandidatesAndEvictsPastItsChunkBound() {
+        TerrainBoundarySignatureStore.Snapshot snapshot = mock(TerrainBoundarySignatureStore.Snapshot.class);
+        when(snapshot.nearestCandidatesForChunk(anyInt(), anyInt(), anyInt())).thenReturn(List.of());
+        TransitionBoundarySampler sampler = new TransitionBoundarySampler(32, snapshot);
+        for (int chunk = 0; chunk < 512; chunk++) {
+            sampler.geometryAt(chunk * 16, 0);
+        }
+        sampler.geometryAt(0, 0);
+        assertEquals(512L, sampler.candidateBuildCount());
+        sampler.geometryAt(512 * 16, 0);
+        sampler.geometryAt(16, 0);
+        assertEquals(514L, sampler.candidateBuildCount());
+    }
+
+    @Test
+    public void denseCandidateIndexesRespectTheReferenceBudget() {
+        List<TerrainBoundarySignature> dense = new ArrayList<>();
+        for (int x = 0; x < 32; x++) {
+            for (int z = 0; z < 32; z++) {
+                dense.add(signature(x, z));
+            }
+        }
+        TerrainBoundarySignatureStore.Snapshot snapshot = mock(TerrainBoundarySignatureStore.Snapshot.class);
+        when(snapshot.nearestCandidatesForChunk(anyInt(), anyInt(), anyInt())).thenReturn(dense);
+        TransitionBoundarySampler sampler = new TransitionBoundarySampler(32, snapshot);
+        for (int chunk = 0; chunk < 33; chunk++) {
+            sampler.geometryAt(chunk * 16, 0);
+        }
+        sampler.geometryAt(0, 0);
+        assertEquals(34L, sampler.candidateBuildCount());
+    }
+
+    @Test
+    public void activeGeometryColumnKeepsItsCandidatesAfterSharedCacheEviction() throws Exception {
+        TerrainBoundarySignatureStore.Snapshot snapshot = mock(TerrainBoundarySignatureStore.Snapshot.class);
+        when(snapshot.nearestCandidatesForChunk(anyInt(), anyInt(), anyInt())).thenReturn(List.of(signature(0, 0)));
+        TransitionBoundarySampler sampler = new TransitionBoundarySampler(32, snapshot);
+        BoundaryGeometryInfluence first = sampler.geometryAt(1, 1);
+        ExecutorService other = Executors.newSingleThreadExecutor();
+        try {
+            other.submit(() -> {
+                for (int chunk = 1; chunk <= 512; chunk++) {
+                    sampler.geometryAt(chunk * 16, 0);
+                }
+            }).get(5, TimeUnit.SECONDS);
+            assertEquals(first, sampler.geometryAt(1, 1));
+            verify(snapshot, times(1)).nearestCandidatesForChunk(0, 0, 32);
+        } finally {
+            other.shutdownNow();
+            assertTrue(other.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void distinctBoundaryScansDoNotHoldTheShardCacheMonitor() throws Exception {
+        TerrainBoundarySignatureStore store = new TerrainBoundarySignatureStore(
+                temporaryFolder.newFolder("parallel-scans").toPath());
+        TerrainBoundarySignatureStore.Snapshot snapshot = store.publish(1L,
+                List.of(signature(0, 0), signature(512, 512)));
+        snapshot.signatureAt(0, 0).orElseThrow();
+        snapshot.signatureAt(512, 512).orElseThrow();
+        Map<Long, List<TerrainBoundarySignature>> cache = shardCache(snapshot);
+        BlockingSignatures blocked = new BlockingSignatures(cache.get(0L));
+        cache.put(0L, blocked);
+        ExecutorService workers = Executors.newFixedThreadPool(2);
+        try {
+            Future<List<TerrainBoundarySignature>> first = workers.submit(
+                    () -> snapshot.nearestCandidatesForChunk(0, 0, 16));
+            assertTrue(blocked.entered.await(5, TimeUnit.SECONDS));
+            Future<List<TerrainBoundarySignature>> distant = workers.submit(
+                    () -> snapshot.nearestCandidatesForChunk(32, 32, 16));
+            assertEquals(512, distant.get(3, TimeUnit.SECONDS).getFirst().blockX());
+            assertFalse(first.isDone());
+            assertTrue(workers.submit(() -> snapshot.intersectsTerrainBand(
+                    new TerrainBoundarySignatureStore.BlockBounds(512, 512, 527, 527), 16))
+                    .get(3, TimeUnit.SECONDS));
+            blocked.release.countDown();
+            assertEquals(0, first.get(3, TimeUnit.SECONDS).getFirst().blockX());
+            assertEquals(2L, snapshot.shardLoadCount());
+        } finally {
+            blocked.release.countDown();
+            workers.shutdownNow();
+            assertTrue(workers.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Map<Long, List<TerrainBoundarySignature>> shardCache(
+            TerrainBoundarySignatureStore.Snapshot snapshot) throws Exception {
+        Field sourceField = TerrainBoundarySignatureStore.Snapshot.class.getDeclaredField("source");
+        sourceField.setAccessible(true);
+        Object source = sourceField.get(snapshot);
+        Field cacheField = source.getClass().getDeclaredField("cache");
+        cacheField.setAccessible(true);
+        return (Map<Long, List<TerrainBoundarySignature>>) cacheField.get(source);
+    }
+
+    private static TerrainBoundarySignature signature(int x, int z) {
+        return new TerrainBoundarySignature(
+                new TerrainBoundarySignature.Column(x, z, 64, 64, OptionalInt.empty(), OptionalInt.empty()),
+                new TerrainBoundarySignature.Samples(new TerrainBoundarySignature.VerticalLayout(0, 4, 0),
+                        new TerrainBoundarySignature.BiomeEncoding(List.of(), new short[0])),
+                GEOMETRY);
+    }
+
+    private static final class BlockingSignatures extends AbstractList<TerrainBoundarySignature> {
+        private final List<TerrainBoundarySignature> values;
+        private final CountDownLatch entered = new CountDownLatch(1);
+        private final CountDownLatch release = new CountDownLatch(1);
+
+        private BlockingSignatures(List<TerrainBoundarySignature> values) {
+            this.values = values;
+        }
+
+        @Override
+        public TerrainBoundarySignature get(int index) {
+            entered.countDown();
+            try {
+                assertTrue(release.await(5, TimeUnit.SECONDS));
+            } catch (InterruptedException interruption) {
+                Thread.currentThread().interrupt();
+                throw new AssertionError(interruption);
+            }
+            return values.get(index);
+        }
+
+        @Override
+        public int size() {
+            return values.size();
+        }
+    }
+}

core/src/test/java/art/arcane/iris/engine/history/GenerationBoundaryStoreTest.java

@@ -262,6 +262,76 @@ public class GenerationBoundaryStoreTest {
         }
     }
 
+    @Test
+    public void repeatedRegionQueriesDoNotWaitForBoundaryIteration() throws Exception {
+        GenerationBoundaryStore store = new GenerationBoundaryStore(
+                temporaryFolder.newFolder("boundary-warm-region").toPath());
+        GenerationBoundary boundary = store.publishPacked(1L,
+                new long[]{GenerationBoundary.packChunk(-1, -1)});
+        CountDownLatch entered = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        ExecutorService queries = Executors.newSingleThreadExecutor();
+        ExecutorService iterator = Executors.newSingleThreadExecutor();
+        try {
+            assertTrue(queries.submit(() -> boundary.isHistoricalChunk(-1, -1)).get(5, TimeUnit.SECONDS));
+            Future<?> iteration = iterator.submit(() -> {
+                boundary.forEachHistoricalChunk((x, z) -> {
+                    entered.countDown();
+                    try {
+                        assertTrue(release.await(5, TimeUnit.SECONDS));
+                    } catch (InterruptedException interruption) {
+                        Thread.currentThread().interrupt();
+                        throw new IOException("Interrupted boundary iteration", interruption);
+                    }
+                });
+                return null;
+            });
+            assertTrue(entered.await(5, TimeUnit.SECONDS));
+            Future<Boolean> warm = queries.submit(() -> {
+                for (int x = -32; x < -1; x++) {
+                    assertFalse(boundary.isHistoricalChunk(x, -1));
+                }
+                return boundary.isHistoricalChunk(-1, -1);
+            });
+            assertTrue(warm.get(3, TimeUnit.SECONDS));
+            assertFalse(iteration.isDone());
+            release.countDown();
+            iteration.get(5, TimeUnit.SECONDS);
+            assertEquals(1, boundary.cachedRegionCount());
+        } finally {
+            release.countDown();
+            queries.shutdownNow();
+            iterator.shutdownNow();
+            assertTrue(queries.awaitTermination(5, TimeUnit.SECONDS));
+            assertTrue(iterator.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void lastRegionChangesPreserveMissingBitsAndCoordinateExtremes() throws Exception {
+        GenerationBoundaryStore store = new GenerationBoundaryStore(
+                temporaryFolder.newFolder("boundary-region-transitions").toPath());
+        List<GenerationBoundary.ChunkCoordinate> chunks = List.of(
+                new GenerationBoundary.ChunkCoordinate(-33, -1),
+                new GenerationBoundary.ChunkCoordinate(-32, -32),
+                new GenerationBoundary.ChunkCoordinate(0, 0),
+                new GenerationBoundary.ChunkCoordinate(31, -32),
+                new GenerationBoundary.ChunkCoordinate(32, 31),
+                new GenerationBoundary.ChunkCoordinate(Integer.MIN_VALUE, Integer.MAX_VALUE),
+                new GenerationBoundary.ChunkCoordinate(Integer.MAX_VALUE, Integer.MIN_VALUE));
+        GenerationBoundary boundary = store.publish(1L, chunks);
+        for (int pass = 0; pass < 3; pass++) {
+            for (GenerationBoundary.ChunkCoordinate chunk : chunks) {
+                assertTrue(boundary.isHistoricalChunk(chunk.chunkX(), chunk.chunkZ()));
+                int neighbor = chunk.chunkX() == Integer.MAX_VALUE ? chunk.chunkX() - 1 : chunk.chunkX() + 1;
+                assertFalse(boundary.isHistoricalChunk(neighbor, chunk.chunkZ()));
+                assertFalse(boundary.isHistoricalChunk(1024, -5555));
+                assertTrue(boundary.isHistoricalChunk(chunk.chunkX(), chunk.chunkZ()));
+            }
+        }
+        assertTrue(boundary.cachedRegionCount() <= 64);
+    }
+
     @Test
     public void knownRegionHitsKeepAccessOrderAndEvictedMasksAreRevalidated() throws Exception {
         GenerationBoundaryStore store = new GenerationBoundaryStore(temporaryFolder.newFolder("boundary-cache-revalidation").toPath());

core/src/test/java/art/arcane/iris/engine/object/IrisObjectDirectPlacementTest.java

@@ -0,0 +1,72 @@
+package art.arcane.iris.engine.object;
+
+import art.arcane.iris.core.link.Identifier;
+import art.arcane.iris.core.service.ExternalDataSVC;
+import art.arcane.iris.spi.IrisServices;
+import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.util.common.data.IrisCustomData;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.data.BlockData;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class IrisObjectDirectPlacementTest {
+    @Test
+    public void bothDirectPlacementMethodsUseProviderWithoutPassingProxyToBukkit() {
+        BlockData base = mock(BlockData.class);
+        Identifier id = new Identifier("craftengine", "test/lamp[lit=true]");
+        IrisCustomData custom = IrisCustomData.of(base, id);
+        IrisObject object = object(custom);
+        World world = mock(World.class);
+        Block block = mock(Block.class);
+        when(world.getBlockAt(any(Location.class))).thenReturn(block);
+        ExternalDataSVC external = mock(ExternalDataSVC.class);
+        when(external.placeBlock(block, id)).thenReturn(true);
+        try (MockedStatic<IrisServices> services = mockStatic(IrisServices.class)) {
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(external);
+
+            object.place(new Location(world, 7, 80, -9));
+            object.placeCenterY(new Location(world, 7, 80, -9));
+
+            verify(external, times(2)).placeBlock(block, id);
+            verify(block, times(0)).setBlockData(any(BlockData.class), anyBoolean());
+        }
+    }
+
+    @Test
+    public void unsupportedProviderPlacesOnlyBaseDataAndVanillaStillPlacesNormally() {
+        BlockData base = mock(BlockData.class);
+        Identifier id = new Identifier("craftengine", "test/chair[variant=alpha]");
+        World world = mock(World.class);
+        Block block = mock(Block.class);
+        when(world.getBlockAt(any(Location.class))).thenReturn(block);
+        ExternalDataSVC external = mock(ExternalDataSVC.class);
+        try (MockedStatic<IrisServices> services = mockStatic(IrisServices.class)) {
+            services.when(() -> IrisServices.getOrNull(ExternalDataSVC.class)).thenReturn(external);
+
+            object(IrisCustomData.of(base, id)).place(new Location(world, 7, 80, -9));
+            object(base).placeCenterY(new Location(world, 7, 80, -9));
+
+            verify(external).placeBlock(block, id);
+            verify(block, times(2)).setBlockData(base, false);
+        }
+    }
+
+    private static IrisObject object(BlockData data) {
+        IrisObject object = new IrisObject(1, 1, 1);
+        PlatformBlockState state = mock(PlatformBlockState.class);
+        when(state.nativeHandle()).thenReturn(data);
+        object.setUnsigned(0, 0, 0, state);
+        return object;
+    }
+}

core/src/test/java/art/arcane/iris/engine/object/IrisObjectTransientBlockTest.java

@@ -0,0 +1,158 @@
+package art.arcane.iris.engine.object;
+
+import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.testsupport.PlatformBinding;
+import art.arcane.iris.util.common.math.IrisBlockVector;
+import art.arcane.volmlib.util.collection.KMap;
+import art.arcane.volmlib.util.math.RNG;
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class IrisObjectTransientBlockTest {
+    private static final List<String> PALETTE = List.of(
+            "minecraft:moving_piston[facing=down,type=normal]", "minecraft:oak_log[axis=y]",
+            "minecraft:oak_leaves[persistent=true]", "minecraft:chest[facing=north,type=single,waterlogged=false]",
+            "minecraft:piston[facing=north,extended=false]", "minecraft:sticky_piston[facing=north,extended=false]",
+            "minecraft:jigsaw[orientation=north_up]");
+    private static final TypeToken<KMap<String, Object>> TILE_PROPERTIES = new TypeToken<>() { };
+
+    @Rule
+    public final PlatformBinding platform = PlatformBinding.mockPlatform();
+
+    private TileData.TileReader previousReader;
+
+    @Before
+    public void bindStatesAndTiles() {
+        when(platform.registries().blockOrNull(anyString(), eq(false)))
+                .thenAnswer(invocation -> state(invocation.getArgument(0)));
+        Gson gson = new Gson();
+        previousReader = TileData.bindPlatformReader(input -> new TileData(input.readUTF(),
+                gson.fromJson(input.readUTF(), TILE_PROPERTIES)));
+    }
+
+    @After
+    public void restoreTiles() {
+        TileData.restorePlatformReader(previousReader);
+        IrisObjectScale.invalidate(null);
+    }
+
+    @Test
+    public void bothObjectFormatsOmitTransientCellsAndTheirTiles() throws Throwable {
+        for (boolean legacy : new boolean[]{false, true}) {
+            IrisObject object = loadFixture(legacy);
+
+            assertEquals(5, object.getBlocks().size());
+            assertNull(object.getBlocks().get(new IrisBlockVector(0, 0, 0)));
+            assertNull(object.getBlocks().get(new IrisBlockVector(6, 0, 0)));
+            assertEquals("minecraft:oak_log", object.getBlocks().get(new IrisBlockVector(1, 0, 0)).materialKey());
+            assertEquals("minecraft:oak_leaves", object.getBlocks().get(new IrisBlockVector(2, 0, 0)).materialKey());
+            assertEquals("minecraft:piston", object.getBlocks().get(new IrisBlockVector(4, 0, 0)).materialKey());
+            assertEquals("minecraft:sticky_piston", object.getBlocks().get(new IrisBlockVector(5, 0, 0)).materialKey());
+            assertEquals(1, object.getStates().size());
+            assertEquals("chest contents", object.getStates().get(new IrisBlockVector(3, 0, 0))
+                    .getProperties().get("payload"));
+        }
+    }
+
+    @Test
+    public void scalingLoadedObjectsKeepsRealBlockEntitiesWithoutRevivingTransientCells() throws Throwable {
+        IrisObject source = loadFixture(false);
+        IrisObjectPlacement placement = new IrisObjectPlacement();
+        for (double factor : new double[]{0.5D, 1D, 2D}) {
+            IrisObject object = placement.scaleObject(new RNG(1337), source,
+                    new IrisDimension().setAllObjectScaleFactor(factor));
+            assertEquals(factor == 2D ? 8 : 1, object.getStates().size());
+            for (Map.Entry<IrisBlockVector, PlatformBlockState> entry : object.getBlocks()) {
+                assertFalse(entry.getValue().materialKey().equals("minecraft:moving_piston"));
+                if (entry.getValue().materialKey().equals("minecraft:chest")) {
+                    assertNotNull(object.getStates().get(entry.getKey()));
+                    assertEquals("chest contents", object.getStates().get(entry.getKey()).getProperties().get("payload"));
+                }
+            }
+        }
+        assertEquals(5, source.getBlocks().size());
+        assertEquals(1, source.getStates().size());
+    }
+
+    private static IrisObject loadFixture(boolean legacy) throws Throwable {
+        IrisObject object = new IrisObject();
+        ByteArrayInputStream input = new ByteArrayInputStream(fixture(legacy));
+        if (legacy) {
+            IrisObjectIO.readLegacy(object, input);
+        } else {
+            IrisObjectIO.read(object, input);
+        }
+        return object;
+    }
+
+    private static byte[] fixture(boolean legacy) throws IOException {
+        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+        try (DataOutputStream output = new DataOutputStream(bytes)) {
+            output.writeInt(16);
+            output.writeInt(4);
+            output.writeInt(4);
+            if (!legacy) {
+                output.writeUTF("Iris V2 IOB;");
+                output.writeShort(PALETTE.size());
+                for (String key : PALETTE) {
+                    output.writeUTF(key);
+                }
+            }
+            output.writeInt(PALETTE.size());
+            for (int index = 0; index < PALETTE.size(); index++) {
+                writePosition(output, index);
+                if (legacy) {
+                    output.writeUTF(PALETTE.get(index));
+                } else {
+                    output.writeShort(index);
+                }
+            }
+            output.writeInt(4);
+            writeTile(output, 0, "minecraft:moving_piston", "transient");
+            writeTile(output, 3, "minecraft:chest", "chest contents");
+            writeTile(output, 6, "minecraft:jigsaw", "marker");
+            writeTile(output, 7, "minecraft:chest", "orphan");
+        }
+        return bytes.toByteArray();
+    }
+
+    private static void writeTile(DataOutputStream output, int x, String material, String payload) throws IOException {
+        writePosition(output, x);
+        output.writeUTF(material);
+        output.writeUTF("{\"payload\":\"" + payload + "\"}");
+    }
+
+    private static void writePosition(DataOutputStream output, int x) throws IOException {
+        output.writeShort(x);
+        output.writeShort(0);
+        output.writeShort(0);
+    }
+
+    private static PlatformBlockState state(String key) {
+        String material = key.substring(0, key.indexOf('['));
+        PlatformBlockState state = mock(PlatformBlockState.class);
+        when(state.key()).thenReturn(key);
+        when(state.materialKey()).thenReturn(material);
+        return state;
+    }
+}

core/src/test/java/art/arcane/iris/engine/platform/BukkitChunkGeneratorGenerationStageGateTest.java

@@ -313,6 +313,68 @@ public class BukkitChunkGeneratorGenerationStageGateTest {
         }
     }
 
+    @Test
+    public void timedExclusiveRetainsPriorityDuringStaggeredGenerationDrain() throws Exception {
+        BukkitChunkGenerator.GenerationStageGate gate =
+                new BukkitChunkGenerator.GenerationStageGate(3, () -> false);
+        BukkitChunkGenerator.GenerationStagePermit first = gate.acquireStage("first-active");
+        BukkitChunkGenerator.GenerationStagePermit last = gate.acquireStage("last-active");
+        CompletableFuture<Void> outward = new CompletableFuture<>();
+        CountDownLatch exclusiveEntered = new CountDownLatch(1);
+        CountDownLatch releaseExclusive = new CountDownLatch(1);
+        CountDownLatch readerEntered = new CountDownLatch(1);
+        List<String> order = new CopyOnWriteArrayList<>();
+        ExecutorService executor = Executors.newFixedThreadPool(3);
+
+        try {
+            Future<?> exclusive = executor.submit(() -> BukkitChunkGenerator.completeExclusiveControlFuture(
+                    gate,
+                    () -> {
+                        order.add("exclusive");
+                        exclusiveEntered.countDown();
+                        try {
+                            assertTrue(releaseExclusive.await(2L, TimeUnit.SECONDS));
+                        } catch (InterruptedException failure) {
+                            Thread.currentThread().interrupt();
+                            throw new IllegalStateException(failure);
+                        }
+                    },
+                    outward,
+                    2L,
+                    TimeUnit.SECONDS));
+            awaitQueueLength(gate, 1);
+            Runnable reader = () -> {
+                try (BukkitChunkGenerator.GenerationStagePermit ignored = gate.acquireStage("later-reader")) {
+                    order.add("reader");
+                    readerEntered.countDown();
+                }
+            };
+            Future<?> firstReader = executor.submit(reader);
+            Future<?> secondReader = executor.submit(reader);
+            awaitQueueLength(gate, 3);
+
+            assertFalse(readerEntered.await(150L, TimeUnit.MILLISECONDS));
+            first.close();
+            assertFalse(readerEntered.await(150L, TimeUnit.MILLISECONDS));
+            last.close();
+            assertTrue(exclusiveEntered.await(2L, TimeUnit.SECONDS));
+            assertEquals(1L, readerEntered.getCount());
+            releaseExclusive.countDown();
+            exclusive.get(2L, TimeUnit.SECONDS);
+            outward.get(2L, TimeUnit.SECONDS);
+            firstReader.get(2L, TimeUnit.SECONDS);
+            secondReader.get(2L, TimeUnit.SECONDS);
+            assertEquals(List.of("exclusive", "reader", "reader"), order);
+            assertEquals(3, gate.availablePermits());
+        } finally {
+            first.close();
+            last.close();
+            releaseExclusive.countDown();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
     @Test
     public void timedExclusiveControlDoesNotReleaseAnUnacquiredPermit() throws Exception {
         AtomicBoolean closing = new AtomicBoolean(false);
@@ -355,16 +417,19 @@ public class BukkitChunkGeneratorGenerationStageGateTest {
         BukkitChunkGenerator.GenerationStagePermit stage = gate.acquireStage("cancellation-holder");
         CompletableFuture<Void> outward = new CompletableFuture<>();
         AtomicBoolean operationRan = new AtomicBoolean(false);
+        AtomicBoolean interruptedAfterCancellation = new AtomicBoolean(true);
         ExecutorService executor = Executors.newSingleThreadExecutor();
 
         try {
-            Future<?> operation = executor.submit(() ->
+            Future<?> operation = executor.submit(() -> {
                 BukkitChunkGenerator.completeExclusiveControlFuture(
                         gate,
                         () -> operationRan.set(true),
                         outward,
                         30L,
-                            TimeUnit.SECONDS));
+                        TimeUnit.SECONDS);
+                interruptedAfterCancellation.set(Thread.currentThread().isInterrupted());
+            });
             awaitQueueLength(gate, 1);
 
             assertTrue(outward.cancel(true));
@@ -372,6 +437,7 @@ public class BukkitChunkGeneratorGenerationStageGateTest {
 
             assertTrue(outward.isCancelled());
             assertFalse(operationRan.get());
+            assertFalse(interruptedAfterCancellation.get());
             assertEquals(0, gate.availablePermits());
         } finally {
             stage.close();
@@ -380,6 +446,80 @@ public class BukkitChunkGeneratorGenerationStageGateTest {
         }
     }
 
+    @Test
+    public void externalInterruptStillRestoresTheAcquisitionWorkerFlag() throws Exception {
+        BukkitChunkGenerator.GenerationStageGate gate =
+                new BukkitChunkGenerator.GenerationStageGate(1, () -> false);
+        BukkitChunkGenerator.GenerationStagePermit stage = gate.acquireStage("interrupt-holder");
+        CompletableFuture<Void> outward = new CompletableFuture<>();
+        AtomicReference<Thread> worker = new AtomicReference<>();
+        AtomicBoolean interruptedAfterAcquisition = new AtomicBoolean(false);
+        AtomicBoolean operationRan = new AtomicBoolean(false);
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+
+        try {
+            Future<?> operation = executor.submit(() -> {
+                worker.set(Thread.currentThread());
+                BukkitChunkGenerator.completeExclusiveControlFuture(gate, () -> operationRan.set(true),
+                        outward, 30L, TimeUnit.SECONDS);
+                interruptedAfterAcquisition.set(Thread.currentThread().isInterrupted());
+            });
+            awaitQueueLength(gate, 1);
+            worker.get().interrupt();
+            operation.get(2L, TimeUnit.SECONDS);
+
+            ExecutionException failure = assertThrows(ExecutionException.class,
+                    () -> outward.get(2L, TimeUnit.SECONDS));
+            assertTrue(failure.getCause() instanceof InterruptedException);
+            assertTrue(interruptedAfterAcquisition.get());
+            assertFalse(operationRan.get());
+            assertEquals(0, gate.availablePermits());
+        } finally {
+            stage.close();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void cancellationAfterAcquisitionDoesNotInterruptTheRunningOperation() throws Exception {
+        BukkitChunkGenerator.GenerationStageGate gate =
+                new BukkitChunkGenerator.GenerationStageGate(1, () -> false);
+        CompletableFuture<Void> outward = new CompletableFuture<>();
+        CountDownLatch entered = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        AtomicBoolean interrupted = new AtomicBoolean(false);
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+
+        try {
+            Future<?> operation = executor.submit(() -> {
+                BukkitChunkGenerator.completeExclusiveControlFuture(gate, () -> {
+                    entered.countDown();
+                    try {
+                        assertTrue(release.await(2L, TimeUnit.SECONDS));
+                    } catch (InterruptedException failure) {
+                        interrupted.set(true);
+                        Thread.currentThread().interrupt();
+                    }
+                }, outward, 30L, TimeUnit.SECONDS);
+                interrupted.compareAndSet(false, Thread.currentThread().isInterrupted());
+            });
+            assertTrue(entered.await(2L, TimeUnit.SECONDS));
+            assertTrue(outward.cancel(true));
+            assertEquals(0, gate.availablePermits());
+            release.countDown();
+            operation.get(2L, TimeUnit.SECONDS);
+
+            assertFalse(interrupted.get());
+            assertTrue(outward.isCancelled());
+            assertEquals(1, gate.availablePermits());
+        } finally {
+            release.countDown();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
     @Test
     public void queuedStageRemainsAdmittedWhileShutdownIsOnlyQuiesced() throws Exception {
         AtomicBoolean closing = new AtomicBoolean(false);

core/src/test/java/art/arcane/iris/platform/bukkit/BukkitCustomBlockTransformTest.java

@@ -0,0 +1,159 @@
+package art.arcane.iris.platform.bukkit;
+
+import art.arcane.iris.core.link.Identifier;
+import art.arcane.iris.core.service.ExternalDataSVC;
+import art.arcane.iris.engine.object.IrisObjectRotation;
+import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.iris.testsupport.BukkitTestServer;
+import art.arcane.iris.util.common.data.IrisCustomData;
+import art.arcane.iris.util.common.data.registry.RegistryUtil;
+import org.bukkit.Material;
+import org.bukkit.block.data.BlockData;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mockStatic;
+
+public class BukkitCustomBlockTransformTest {
+    @BeforeClass
+    public static void installServer() {
+        BukkitTestServer.install();
+        try (MockedStatic<RegistryUtil> registry = mockStatic(RegistryUtil.class)) {
+            registry.when(() -> RegistryUtil.find(Material.class, "grass", "short_grass")).thenReturn(Material.SHORT_GRASS);
+            BukkitBlockResolution.getAir();
+        }
+    }
+
+    @Test
+    public void waterloggingUpdatesSemanticIdentityAndResolvedCarrier() {
+        IrisCustomData original = custom("craftengine:forest/amber_slab[axis=x,waterlogged=false]", 1);
+        IrisCustomData expected = custom("craftengine:forest/amber_slab[axis=x,waterlogged=true]", 2);
+        PlatformBlockState state = BukkitBlockState.of(original);
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            resolveTo(resolution, expected);
+            PlatformBlockState result = state.withProperty("waterlogged", "true");
+
+            assertSame(expected, result.nativeHandle());
+            assertEquals(expected.getCustom().toString(), result.deferredPlacementKey());
+            assertEquals(expected.getBase().getAsString(), result.placementBaseState().key());
+            assertEquals("craftengine:forest/amber_slab[axis=x,waterlogged=false]", state.key());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void customPropertyRejectsAnUnresolvableValue() {
+        PlatformBlockState state = BukkitBlockState.of(custom("craftengine:forest/amber_log[axis=x]", 1));
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            IllegalArgumentException error = assertThrows(IllegalArgumentException.class,
+                    () -> state.withProperty("axis", "invalid"));
+
+            assertTrue(error.getMessage().contains("axis=invalid"));
+            assertEquals("craftengine:forest/amber_log[axis=x]", state.key());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull("craftengine:forest/amber_log[axis=invalid]"));
+        }
+    }
+
+    @Test
+    public void semanticFacingRotatesWithoutDirectionalCarrier() {
+        IrisCustomData original = custom("craftengine:forest/amber_lamp[facing=north,waterlogged=true]", 1);
+        IrisCustomData expected = custom("craftengine:forest/amber_lamp[facing=west,waterlogged=true]", 2);
+        PlatformBlockState state = BukkitBlockState.of(original);
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            resolveTo(resolution, expected);
+            PlatformBlockState result = IrisObjectRotation.of(0, 90, 0).rotate(state, 0, 0, 0);
+
+            assertSame(expected, result.nativeHandle());
+            assertEquals(expected.getCustom().toString(), result.key());
+            assertEquals("craftengine:forest/amber_lamp[facing=north,waterlogged=true]", state.key());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void semanticAxisRotatesThroughRawBlockDataEntryPoint() {
+        IrisCustomData original = custom("craftengine:forest/amber_log[axis=x,waterlogged=false]", 1);
+        IrisCustomData expected = custom("craftengine:forest/amber_log[axis=z,waterlogged=false]", 2);
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            resolveTo(resolution, expected);
+            BlockData result = IrisObjectRotation.of(0, 90, 0).rotate(original, 0, 0, 0);
+
+            assertSame(expected, result);
+            assertEquals("craftengine:forest/amber_log[axis=x,waterlogged=false]", original.getCustom().toString());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void semanticRotationPreservesSixteenWayOrientation() {
+        PlatformBlockState state = BukkitBlockState.of(custom("craftengine:forest/amber_sign[rotation=0]", 1));
+        IrisCustomData expected = custom("craftengine:forest/amber_sign[rotation=12]", 2);
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            resolveTo(resolution, expected);
+            PlatformBlockState result = IrisObjectRotation.of(0, 90, 0).rotate(state, 0, 0, 0);
+
+            assertSame(expected, result.nativeHandle());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void semanticConnectionsRotateTogether() {
+        PlatformBlockState state = BukkitBlockState.of(custom(
+                "craftengine:forest/amber_fence[north=true,east=false,south=false,west=false]", 1));
+        IrisCustomData expected = custom(
+                "craftengine:forest/amber_fence[north=false,east=false,south=false,west=true]", 2);
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            resolveTo(resolution, expected);
+            PlatformBlockState result = IrisObjectRotation.of(0, 90, 0).rotate(state, 0, 0, 0);
+
+            assertSame(expected, result.nativeHandle());
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void unsupportedRotationRetainsTheOriginalCustomBlock() {
+        PlatformBlockState state = BukkitBlockState.of(custom("craftengine:forest/amber_lamp[facing=north]", 1));
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            assertSame(state, IrisObjectRotation.of(90, 0, 0).rotate(state, 0, 0, 0));
+            resolution.verify(() -> BukkitBlockResolution.resolveOrNull(anyString()));
+        }
+    }
+
+    @Test
+    public void unchangedSemanticAxisDoesNotResolveOrMutateCarrier() {
+        PlatformBlockState state = BukkitBlockState.of(custom("craftengine:forest/amber_log[axis=y]", 1));
+
+        try (MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class)) {
+            assertSame(state, IrisObjectRotation.of(0, 90, 0).rotate(state, 0, 0, 0));
+            resolution.verifyNoInteractions();
+        }
+    }
+
+    private static IrisCustomData custom(String key, int note) {
+        BlockData carrier = BukkitTestServer.blockData("minecraft:note_block[instrument=harp,note=" + note + ",powered=false]");
+        return IrisCustomData.of(carrier, Identifier.fromString(key));
+    }
+
+    private static void resolveTo(MockedStatic<BukkitBlockResolution> resolution, IrisCustomData expected) {
+        resolution.when(() -> BukkitBlockResolution.resolveOrNull(anyString())).thenAnswer(invocation -> {
+            Identifier actual = Identifier.fromString(invocation.getArgument(0, String.class));
+            assertEquals(ExternalDataSVC.parseState(expected.getCustom()), ExternalDataSVC.parseState(actual));
+            return expected;
+        });
+    }
+}

gradle/libs.versions.toml

@@ -46,7 +46,7 @@ mythic = "5.12.1"
 mythic-crucible = "2.2.0"
 kgenerators = "7.3" # https://repo.codemc.io/repository/maven-public/me/kryniowesegryderiusz/kgenerators-core/maven-metadata.xml
 multiverseCore = "5.8.0"
-craftengine = "26.7.3" # https://github.com/Xiao-MoMi/craft-engine/releases
+craftengine = "26.8.2" # https://github.com/Xiao-MoMi/craft-engine/releases
 
 # Fabric API (net.fabricmc.fabric-api) - each module is independently versioned
 fabricApi-base = "2.0.4+ece063239e"