diff --git a/core/src/main/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolver.java b/core/src/main/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolver.java
index 9607089eb..0ef34aff0 100644
--- a/core/src/main/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolver.java
+++ b/core/src/main/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolver.java
@@ -14,7 +14,7 @@ import art.arcane.volmlib.util.noise.CNG;
 
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.Arrays;
 import java.util.IdentityHashMap;
 import java.util.List;
 import java.util.Map;
@@ -81,8 +81,9 @@ public final class IrisDimensionCarvingResolver {
     }
 
     private static IrisDimensionCarvingEntry resolveBoundRootEntry(Engine engine, int worldY, IrisData data, State resolvedState) {
-        if (resolvedState.rootEntriesByWorldY.containsKey(worldY)) {
-            return resolvedState.rootEntriesByWorldY.get(worldY);
+        int slot = resolvedState.rootSlot(worldY);
+        if (slot >= 0) {
+            return resolvedState.roots[slot];
         }
 
         return selectBoundRootEntry(engine.getDimension(), worldY, data, resolvedState);
@@ -91,7 +92,7 @@ public final class IrisDimensionCarvingResolver {
     private static IrisDimensionCarvingEntry selectBoundRootEntry(IrisDimension dimension, int worldY, IrisData data, State resolvedState) {
         List<IrisDimensionCarvingEntry> entries = dimension.getCarving();
         if (entries == null || entries.isEmpty()) {
-            resolvedState.rootEntriesByWorldY.put(worldY, null);
+            resolvedState.rememberRoot(worldY, null);
             return null;
         }
 
@@ -104,7 +105,7 @@ public final class IrisDimensionCarvingResolver {
             resolved = entry;
         }
 
-        resolvedState.rootEntriesByWorldY.put(worldY, resolved);
+        resolvedState.rememberRoot(worldY, resolved);
         return resolved;
     }
 
@@ -324,8 +325,9 @@ public final class IrisDimensionCarvingResolver {
         }
 
         public IrisBiome resolveBiome(int worldX, int worldY, int worldZ) {
-            IrisDimensionCarvingEntry root = state.rootEntriesByWorldY.containsKey(worldY)
-                    ? state.rootEntriesByWorldY.get(worldY)
+            int slot = state.rootSlot(worldY);
+            IrisDimensionCarvingEntry root = slot >= 0
+                    ? state.roots[slot]
                     : selectBoundRootEntry(dimension, worldY, data, state);
             if (root == null) {
                 return null;
@@ -336,7 +338,11 @@ public final class IrisDimensionCarvingResolver {
     }
 
     public static final class State {
-        private final Map<Integer, IrisDimensionCarvingEntry> rootEntriesByWorldY = new HashMap<>();
+        private static final int ROOT_SLOTS = 512;
+
+        private int[] rootWorldYs;
+        private IrisDimensionCarvingEntry[] roots;
+        private boolean[] rootsKnown;
         private final Map<IrisDimensionCarvingEntry, IrisRaritySelection<CarvingChoice>> selectionPlans = new IdentityHashMap<>();
         private final Map<IrisDimensionCarvingEntry, IrisBiome> biomeCache = new IdentityHashMap<>();
         private WeakReference<Engine> engineIdentity;
@@ -357,7 +363,10 @@ public final class IrisDimensionCarvingResolver {
             engineIdentity = new WeakReference<>(engine);
             dimensionIdentity = new WeakReference<>(dimension);
             dataIdentity = new WeakReference<>(data);
-            rootEntriesByWorldY.clear();
+            if (rootsKnown != null) {
+                Arrays.fill(rootsKnown, false);
+                Arrays.fill(roots, null);
+            }
             selectionPlans.clear();
             biomeCache.clear();
             entryIndex = null;
@@ -366,6 +375,23 @@ public final class IrisDimensionCarvingResolver {
             return data;
         }
 
+        private int rootSlot(int worldY) {
+            int slot = worldY & (ROOT_SLOTS - 1);
+            return rootsKnown != null && rootsKnown[slot] && rootWorldYs[slot] == worldY ? slot : -1;
+        }
+
+        private void rememberRoot(int worldY, IrisDimensionCarvingEntry root) {
+            if (rootsKnown == null) {
+                rootWorldYs = new int[ROOT_SLOTS];
+                roots = new IrisDimensionCarvingEntry[ROOT_SLOTS];
+                rootsKnown = new boolean[ROOT_SLOTS];
+            }
+            int slot = worldY & (ROOT_SLOTS - 1);
+            rootWorldYs[slot] = worldY;
+            roots[slot] = root;
+            rootsKnown[slot] = true;
+        }
+
         private static boolean references(WeakReference<?> identity, Object value) {
             return identity != null && identity.get() == value;
         }
diff --git a/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticCapture.java b/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticCapture.java
index edd4de352..8e8c8cb9a 100644
--- a/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticCapture.java
+++ b/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticCapture.java
@@ -227,12 +227,12 @@ public final class GenerationSemanticCapture {
         }
         resolvedCaves.set(position);
         if (explicitBiomeKey != null && !explicitBiomeKey.isBlank()) {
-            semantics.addCaveBiome(explicitBiomeKey);
+            caveBiomes.add(semantics, explicitBiomeKey);
             return;
         }
         IrisBiome caveBiome = caveBiomes.resolve(blockX, y, blockZ);
         if (caveBiome != null && caveBiome.getLoadKey() != null) {
-            semantics.addCaveBiome(caveBiome.getLoadKey());
+            caveBiomes.add(semantics, caveBiome.getLoadKey());
         }
     }
 
@@ -280,6 +280,7 @@ public final class GenerationSemanticCapture {
         private final IrisDimensionCarvingResolver.State fallbackState = new IrisDimensionCarvingResolver.State();
         private IrisDimensionCarvingResolver.Snapshot snapshot;
         private int minimumY;
+        private String lastKey;
 
         private CaveBiomes(Engine engine, boolean scoped) {
             this.engine = engine;
@@ -290,6 +291,13 @@ public final class GenerationSemanticCapture {
                     : null;
         }
 
+        private void add(ChunkGenerationSemantics.Builder semantics, String key) {
+            if (key != lastKey) {
+                semantics.addCaveBiome(key);
+                lastKey = key;
+            }
+        }
+
         private IrisBiome resolve(int x, int y, int z) {
             if (!scoped) {
                 return engine.getCaveBiome(x, y, z);
diff --git a/core/src/test/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolverParityTest.java b/core/src/test/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolverParityTest.java
index 3ee98ec8b..504be0ec7 100644
--- a/core/src/test/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolverParityTest.java
+++ b/core/src/test/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolverParityTest.java
@@ -494,12 +494,11 @@ public class IrisDimensionCarvingResolverParityTest {
         assertSame(fixture.entry(), IrisDimensionCarvingResolver.resolveRootEntry(
                 fixture.engine(), 80, state));
 
-        Field rootEntriesField = IrisDimensionCarvingResolver.State.class
-                .getDeclaredField("rootEntriesByWorldY");
-        rootEntriesField.setAccessible(true);
+        Field rootsField = IrisDimensionCarvingResolver.State.class.getDeclaredField("roots");
+        rootsField.setAccessible(true);
         System.gc();
 
-        assertSame(fixture.entry(), ((Map<?, ?>) rootEntriesField.get(state)).get(80));
+        assertSame(fixture.entry(), ((IrisDimensionCarvingEntry[]) rootsField.get(state))[80]);
     }
 
     private RetainedFixture createRetainedFixture() {