Well.. not for now at least let me just remove that-

core/src/main/java/art/arcane/iris/generation/runtime/Engine.java

@@ -87,10 +87,6 @@ import java.util.stream.Collectors;
 public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer, Hotloadable {
     IrisComplex getComplex();
 
-    default art.arcane.iris.structure.object.PlacementLifecycles getPlacementLifecycles() {
-        return art.arcane.iris.structure.object.PlacementLifecycles.defaults();
-    }
-
     default BiomeEnvironment getBiomeEnvironment(int x, int y, int z) {
         return new BiomeEnvironment(0L, getBiome(x, y, z), getRegion(x, y, z), getDimension(), getData());
     }

core/src/main/java/art/arcane/iris/generation/runtime/EngineHotloader.java

@@ -96,8 +96,7 @@ final class EngineHotloader {
                             assembly.complex,
                             assembly.upperContext,
                             assembly.dimensionStackContext,
-                            biomeMaxes,
-                            assembly.placementLifecycles);
+                            biomeMaxes);
                     next = previous.withGeneration(nextGeneration);
                 } finally {
                     engine.threadState.setAssembly(null);

core/src/main/java/art/arcane/iris/generation/runtime/EngineRuntimeBuilder.java

@@ -18,8 +18,6 @@
 
 package art.arcane.iris.generation.runtime;
 
-import art.arcane.iris.structure.object.PlacementLifecycles;
-
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.pack.loading.ResourceLoader;
 import art.arcane.iris.generation.runtime.GenerationRuntime.BiomeMaxes;
@@ -422,7 +420,6 @@ final class EngineRuntimeBuilder {
         final GenerationKernelRegistry.RuntimeKernel runtimeKernel;
         final SeedManager seedManager;
         final TransitionGenerationPlan transitionPlan;
-        final PlacementLifecycles placementLifecycles;
 
         static int nextRuntimeId() {
             return RUNTIME_IDS.incrementAndGet();
@@ -471,7 +468,6 @@ final class EngineRuntimeBuilder {
             this.seedManager = this.runtimeKernel.createSeedManager(target.getWorld().getRawWorldSeed());
             this.kernelVersion = this.runtimeKernel.version();
             this.transitionPlan = transitionPlan;
-            this.placementLifecycles = PlacementLifecycles.resolve();
         }
 
         GenerationRuntime freezeGeneration(BiomeMaxes biomeMaxes) {
@@ -494,8 +490,7 @@ final class EngineRuntimeBuilder {
                     mantle,
                     mantleStorageDirectory,
                     hash32,
-                    biomeMaxes,
-                    placementLifecycles);
+                    biomeMaxes);
         }
 
         EngineRuntime freezeRuntime(BiomeMaxes biomeMaxes) {

core/src/main/java/art/arcane/iris/generation/runtime/GenerationRuntime.java

@@ -18,8 +18,6 @@
 
 package art.arcane.iris.generation.runtime;
 
-import art.arcane.iris.structure.object.PlacementLifecycles;
-
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.world.history.TransitionGenerationPlan;
 import art.arcane.iris.world.history.GenerationKernelRegistry;
@@ -46,8 +44,7 @@ record GenerationRuntime(
         EngineMantle mantle,
         Path mantleStorageDirectory,
         CompletableFuture<Long> hash32,
-        BiomeMaxes biomeMaxes,
-        PlacementLifecycles placementLifecycles
+        BiomeMaxes biomeMaxes
 ) {
     GenerationRuntime {
         Objects.requireNonNull(target, "generation target");
@@ -64,7 +61,6 @@ record GenerationRuntime(
         Objects.requireNonNull(mantle, "generation mantle");
         mantleStorageDirectory = IrisEngineMantle.normalizeStorageDirectory(mantleStorageDirectory);
         Objects.requireNonNull(hash32, "generation pack hash");
-        Objects.requireNonNull(placementLifecycles, "placement lifecycles");
         Objects.requireNonNull(biomeMaxes, "generation biome maximums");
         if (target.getData() != data || target.getDimension() != dimension) {
             throw new IllegalArgumentException("Generation target, data, and dimension must describe one runtime.");
@@ -76,8 +72,7 @@ record GenerationRuntime(
             IrisComplex nextComplex,
             UpperDimensionContext nextUpperContext,
             DimensionStackContext nextDimensionStackContext,
-            BiomeMaxes nextBiomeMaxes,
-            PlacementLifecycles nextPlacementLifecycles
+            BiomeMaxes nextBiomeMaxes
     ) {
         return new GenerationRuntime(
                 nextCacheId,
@@ -95,8 +90,7 @@ record GenerationRuntime(
                 mantle,
                 mantleStorageDirectory,
                 hash32,
-                nextBiomeMaxes,
-                nextPlacementLifecycles);
+                nextBiomeMaxes);
     }
 
     record BiomeMaxes(double objectDensity, double layerDensity, double decoratorDensity) {

core/src/main/java/art/arcane/iris/generation/runtime/IrisEngine.java

@@ -1403,20 +1403,6 @@ public class IrisEngine implements Engine {
         return current == null ? null : current.complex();
     }
 
-    @Override
-    public art.arcane.iris.structure.object.PlacementLifecycles getPlacementLifecycles() {
-        EngineThreadState.Frame frame = threadState.current();
-        RuntimeAssembly assembly = frame == null ? null : frame.assembly;
-        if (assembly != null) {
-            return assembly.placementLifecycles;
-        }
-        GenerationRuntime current = selectedGenerationRuntime(frame);
-        if (current == null) {
-            throw new IllegalStateException("Placement requires an active Iris runtime.");
-        }
-        return current.placementLifecycles();
-    }
-
     @Override
     public EngineTarget getTarget() {
         return targetIn(threadState.current());

core/src/main/java/art/arcane/iris/structure/object/IrisObjectPlacementRunner.java

@@ -27,7 +27,7 @@ import art.arcane.volmlib.util.math.RNG;
 
 import java.util.function.BiConsumer;
 
-/** Entry point for executing an engine's resolved placement plan. */
+/** Entry point for executing the resolved placement plan of a mode. */
 final class IrisObjectPlacementRunner {
     private final IrisObject self;
     private final IrisObjectPlacementAlignment alignment;
@@ -40,6 +40,6 @@ final class IrisObjectPlacementRunner {
     int place(int x, int yv, int z, IObjectPlacer placer, IrisObjectPlacement config, RNG rng,
               BiConsumer<BlockPosition, NativeBlockState> listener, CarveResult cave, IrisData data) {
         PlacementContext context = new PlacementContext(config, data, placer, cave, rng, self, alignment, x, z, yv, listener);
-        return PlacementLifecycles.forPlacer(placer).get(config.getMode()).execute(context).heightOrRejected();
+        return PlacementLifecycles.defaults().get(config.getMode()).execute(context).heightOrRejected();
     }
 }

core/src/main/java/art/arcane/iris/structure/object/PlacementLifecycles.java

@@ -3,16 +3,17 @@ package art.arcane.iris.structure.object;
 
 import java.util.EnumMap;
 import java.util.Map;
+import java.util.Objects;
 
-/** One resolved plan per mode in an engine runtime. Engine-less tools share a separate default set. */
-public final class PlacementLifecycles {
+/** One resolved plan per mode. Plans are immutable, so every placement shares the default set. */
+final class PlacementLifecycles {
     private final Map<ObjectPlaceMode, PlacementLifecycle> plans;
 
     private PlacementLifecycles(Map<ObjectPlaceMode, PlacementLifecycle> plans) {
         this.plans = Map.copyOf(plans);
     }
 
-    public static PlacementLifecycles resolve() {
+    static PlacementLifecycles resolve() {
         Map<ObjectPlaceMode, PlacementLifecycle> plans = new EnumMap<>(ObjectPlaceMode.class);
         for (ObjectPlaceMode mode : ObjectPlaceMode.values()) {
             try {
@@ -24,18 +25,12 @@ public final class PlacementLifecycles {
         return new PlacementLifecycles(plans);
     }
 
-    public static PlacementLifecycles defaults() {
+    static PlacementLifecycles defaults() {
         return Defaults.INSTANCE;
     }
 
-    static PlacementLifecycles forPlacer(IObjectPlacer placer) {
-        var engine = placer.getEngine();
-        PlacementLifecycles plans = engine == null ? null : engine.getPlacementLifecycles();
-        return plans == null ? defaults() : plans;
-    }
-
-    public PlacementLifecycle get(ObjectPlaceMode mode) {
-        return plans.get(java.util.Objects.requireNonNull(mode, "Placement mode"));
+    PlacementLifecycle get(ObjectPlaceMode mode) {
+        return plans.get(Objects.requireNonNull(mode, "Placement mode"));
     }
 
     private static final class Defaults {

core/src/test/java/art/arcane/iris/generation/runtime/EnginePlacementLifecycleTest.java

@@ -1,62 +0,0 @@
-package art.arcane.iris.generation.runtime;
-
-import art.arcane.iris.generation.runtime.EngineEffects;
-import art.arcane.iris.generation.runtime.EngineMode;
-import art.arcane.iris.generation.runtime.EngineTarget;
-import art.arcane.iris.generation.runtime.EngineWorldManager;
-import art.arcane.iris.structure.object.ObjectPlaceMode;
-import org.junit.Test;
-
-import java.util.concurrent.CompletableFuture;
-
-import static org.junit.Assert.*;
-import static org.mockito.Mockito.mock;
-
-public class EnginePlacementLifecycleTest {
-    @Test
-    public void runtimeAssemblyResolvesBeforePublicationAndKeepsOldPlansIntact() {
-        var initial = assembly(1);
-        EngineRuntime previous = initial.freezeRuntime(new GenerationRuntime.BiomeMaxes(0, 0, 0));
-        var replacement = assembly(2);
-        EngineRuntime next = replacement.freezeRuntime(new GenerationRuntime.BiomeMaxes(0, 0, 0));
-
-        assertSame(initial.placementLifecycles, previous.generation().placementLifecycles());
-        assertSame(replacement.placementLifecycles, next.generation().placementLifecycles());
-        for (ObjectPlaceMode mode : ObjectPlaceMode.values()) {
-            assertNotNull(next.generation().placementLifecycles().get(mode));
-            assertNotSame(previous.generation().placementLifecycles().get(mode), next.generation().placementLifecycles().get(mode));
-        }
-        assertSame(initial.placementLifecycles, previous.generation().placementLifecycles());
-    }
-
-    @Test
-    public void complexReplacementCarriesNewPlansAlongsideTheNewComplex() {
-        var initial = assembly(1);
-        EngineRuntime previous = initial.freezeRuntime(new GenerationRuntime.BiomeMaxes(0, 0, 0));
-        var replacement = assembly(2);
-        EngineRuntime next = previous.withGeneration(previous.generation().withComplex(2, replacement.complex, null, null,
-                new GenerationRuntime.BiomeMaxes(1, 1, 1), replacement.placementLifecycles));
-
-        assertSame(replacement.placementLifecycles, next.generation().placementLifecycles());
-        assertSame(replacement.complex, next.generation().complex());
-        assertSame(previous.worldManager(), next.worldManager());
-        assertSame(initial.placementLifecycles, previous.generation().placementLifecycles());
-    }
-
-    private EngineRuntimeBuilder.RuntimeAssembly assembly(int id) {
-        EngineTarget target = mock(EngineTarget.class);
-        var world = mock(art.arcane.iris.world.IrisWorld.class);
-        org.mockito.Mockito.when(target.getWorld()).thenReturn(world);
-        org.mockito.Mockito.when(target.getData()).thenReturn(mock(art.arcane.iris.pack.loading.IrisData.class));
-        org.mockito.Mockito.when(target.getDimension()).thenReturn(mock(art.arcane.iris.generation.terrain.IrisDimension.class));
-        var assembly = new EngineRuntimeBuilder.RuntimeAssembly(id, target,
-                java.nio.file.Path.of("build", "test-mantles", "placement-" + id));
-        assembly.mantle = mock(art.arcane.iris.generation.mantle.EngineMantle.class);
-        assembly.complex = mock(IrisComplex.class);
-        assembly.effects = mock(EngineEffects.class);
-        assembly.mode = mock(EngineMode.class);
-        assembly.worldManager = mock(EngineWorldManager.class);
-        assembly.hash32 = CompletableFuture.completedFuture(0L);
-        return assembly;
-    }
-}

core/src/test/java/art/arcane/iris/generation/runtime/EngineShutdownDrainTest.java

@@ -858,7 +858,7 @@ public class EngineShutdownDrainTest {
             when(generation.runtimeKernel()).thenReturn(kernel);
             GenerationRuntime nextGeneration = generation(target, mantle);
             when(nextGeneration.complex()).thenReturn(replacement);
-            when(generation.withComplex(anyInt(), same(replacement), isNull(), isNull(), any(), any()))
+            when(generation.withComplex(anyInt(), same(replacement), isNull(), isNull(), any()))
                     .thenReturn(nextGeneration);
             EngineRuntimeBuilder builder = spy(new EngineRuntimeBuilder(engine));
             doReturn(new GenerationRuntime.BiomeMaxes(0D, 0D, 0D)).when(builder).computeBiomeMaxes();

core/src/test/java/art/arcane/iris/generation/runtime/IrisEngineGenerationRuntimeScopeTest.java

@@ -335,7 +335,6 @@ public class IrisEngineGenerationRuntimeScopeTest {
             assertSame(detached.dimension, engine.getDimension());
             assertSame(detached.runtime.seedManager(), engine.getSeedManager());
             assertSame(detached.complex, engine.getComplex());
-            assertSame(detached.runtime.placementLifecycles(), engine.getPlacementLifecycles());
             assertSame(detached.upperContext, engine.getUpperContext());
             assertSame(detached.dimensionStackContext, engine.getDimensionStackContext());
             assertSame(detached.mode, engine.getMode());
@@ -352,7 +351,6 @@ public class IrisEngineGenerationRuntimeScopeTest {
         assertSame(active.target, engine.getTarget());
         assertSame(active.data, engine.getData());
         assertSame(active.runtime.seedManager(), engine.getSeedManager());
-        assertSame(active.runtime.placementLifecycles(), engine.getPlacementLifecycles());
         assertSame(active.mantle, engine.getMantle());
         assertEquals(1, engine.getCacheID());
     }
@@ -1011,8 +1009,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
                 mantle,
                 mantleStorageDirectory,
                 hash32,
-                new BiomeMaxes(objectDensity, layerDensity, decoratorDensity),
-                art.arcane.iris.structure.object.PlacementLifecycles.resolve());
+                new BiomeMaxes(objectDensity, layerDensity, decoratorDensity));
         return new RuntimeFixture(
                 runtime,
                 target,

core/src/test/java/art/arcane/iris/structure/object/IrisObjectPlacementLifecycleRegressionTest.java

@@ -271,7 +271,7 @@ public class IrisObjectPlacementLifecycleRegressionTest {
     }
 
     @Test
-    public void runnerUsesTheEnginePlanAndCompletesTheBlockPassBeforeAfterBlocks() {
+    public void customPlanCompletesTheBlockPassBeforeAfterBlocks() {
         RecordingPlacer placer = new RecordingPlacer(engine);
         PlacementLifecycleBuilder builder = new PlacementLifecycleBuilder();
         ObjectPlaceMode.CENTER_HEIGHT.install(builder);
@@ -280,11 +280,10 @@ public class IrisObjectPlacementLifecycleRegressionTest {
         List<Integer> finishedSizes = new ArrayList<>();
         builder.add(new PlacementLifecycleDependency("test.finished"), PlacementStage.AFTER_BLOCKS,
                 (context, state, ignored) -> finishedSizes.add(placer.writes().size()));
-        PlacementLifecycles plans = mock(PlacementLifecycles.class);
-        when(plans.get(ObjectPlaceMode.CENTER_HEIGHT)).thenReturn(builder.build());
-        when(engine.getPlacementLifecycles()).thenReturn(plans);
+        PlacementContext context = new PlacementContext(placement(), data, placer, null, new RNG(2L), lineObject(3),
+                0, 0, ANCHOR_Y, null);
 
-        assertEquals(ANCHOR_Y + 5, lineObject(3).place(0, ANCHOR_Y, 0, placer, placement(), new RNG(2L), data));
+        assertEquals(ANCHOR_Y + 5, builder.build().execute(context).heightOrRejected());
         assertEquals(List.of(3), finishedSizes);
         assertTrue(placer.writes().stream().allMatch(write -> write.y() == ANCHOR_Y + 5));
     }

core/src/test/java/art/arcane/iris/structure/object/PlacementLifecycleTest.java

@@ -98,7 +98,7 @@ public class PlacementLifecycleTest {
     }
 
     @Test
-    public void everyModeResolvesAndRuntimePlansAreIndependent() {
+    public void everyModeResolvesToIndependentPlans() {
         PlacementLifecycles first = PlacementLifecycles.resolve();
         PlacementLifecycles second = PlacementLifecycles.resolve();
         for (ObjectPlaceMode mode : ObjectPlaceMode.values()) {