Stabilized hydrology pregeneration

- Preserve exact river owner plans across cache eviction and persistence.
- Retry required hydrology plans without generating riverless terrain.
- Bound object plans and pregeneration residency by available heap.
- Release completed native chunks and avoid empty reclamation flushes.
- Cover persistence, admission, cancellation, and ownership regressions.

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

@@ -27,7 +27,6 @@ import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.volmlib.util.io.IO;
 import art.arcane.volmlib.util.json.JSONException;
 import art.arcane.volmlib.util.json.JSONObject;
-import art.arcane.iris.platform.bootstrap.getHardware;
 import art.arcane.iris.platform.bukkit.plugin.VolmitSender;
 import lombok.Data;
 
@@ -226,7 +225,7 @@ public class IrisSettings {
     public static class IrisSettingsPregen {
         private static final int REFERENCE_WORLD_HEIGHT = 384;
         private static final int MIN_RESIDENT_TECTONIC_PLATES = 16;
-        private static final double MANTLE_HEAP_FRACTION = 0.6D;
+        private static final double MANTLE_HEAP_FRACTION = 0.25D;
         private static final int REFERENCE_PLATE_MEGABYTES = 48;
         public IrisRuntimeSchedulerMode runtimeSchedulerMode = IrisRuntimeSchedulerMode.AUTO;
         public IrisPaperLikeBackendMode paperLikeBackendMode = IrisPaperLikeBackendMode.AUTO;
@@ -256,10 +255,14 @@ public class IrisSettings {
         }
 
         public int getEffectiveResidentTectonicPlates(int worldHeight) {
+            return effectiveResidentTectonicPlates(worldHeight, Runtime.getRuntime().maxMemory());
+        }
+
+        int effectiveResidentTectonicPlates(int worldHeight, long maximumHeapBytes) {
             int baseCap = getMaxResidentTectonicPlates();
             int normalizedHeight = Math.max(1, worldHeight);
             int heightScaledCap = (int) Math.round((double) baseCap * REFERENCE_WORLD_HEIGHT / (double) normalizedHeight);
-            long maxHeapMegabytes = getHardware.getProcessMemory();
+            long maxHeapMegabytes = maximumHeapBytes / (1024L * 1024L);
             double plateMegabytes = (double) REFERENCE_PLATE_MEGABYTES * (double) normalizedHeight / (double) REFERENCE_WORLD_HEIGHT;
             int byteBudgetCap = (int) Math.floor(MANTLE_HEAP_FRACTION * (double) maxHeapMegabytes / plateMegabytes);
             int effective = Math.min(heightScaledCap, byteBudgetCap);

core/src/main/java/art/arcane/iris/generation/hydrology/CrossTileResolutionContext.java

@@ -39,7 +39,8 @@ final class CrossTileResolutionContext {
         CrossTileResolvedOwner existing = resolved.putIfAbsent(key, owner);
         if (existing != null
                 && !existing.withoutFootprintCompiler().equals(owner.withoutFootprintCompiler())) {
-            throw new IllegalStateException("Cross-tile owner resolution produced inconsistent cached results.");
+            throw new IllegalStateException("Cross-tile owner resolution produced inconsistent cached results for "
+                    + key.tileX() + "," + key.tileZ() + " while planning " + root.tileX() + "," + root.tileZ() + ".");
         }
         if (resolved.size() > maximumOwners) {
             throw new IllegalStateException("Cross-tile owner dependencies exceeded their color-ranked count bound.");

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyCacheWeights.java

@@ -24,6 +24,9 @@ final class HydrologyCacheWeights {
         long bytes = network(tile.nodes(), tile.edges(), tile.outlets(), tile.courses(), tile.cavePlans());
         bytes += diagnostics(tile.localDiagnosticCandidates());
         bytes += (long) tile.regionalCourseIds().size() * 64L;
+        if (tile.resolvedOwner() != null) {
+            bytes += owner(tile.resolvedOwner());
+        }
         RiverFootprint footprint = tile.footprint();
         if (footprint != null) {
             bytes += (long) footprint.size() * 64L;

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyOwnerDraft.java

@@ -1,6 +1,7 @@
 package art.arcane.iris.generation.hydrology;
 
 import java.util.List;
+import java.util.Objects;
 
 record HydrologyOwnerDraft(
         HydrologyTileKey key,
@@ -8,6 +9,14 @@ record HydrologyOwnerDraft(
         List<HydrologyDiagnosticCandidate> diagnostics,
         HydrologyFootprintCompiler footprintCompiler
 ) {
+    HydrologyOwnerDraft {
+        Objects.requireNonNull(key, "key");
+        Objects.requireNonNull(result, "result");
+        result = new HydrologyCaveCourseFilter.Result(List.copyOf(result.nodes()), List.copyOf(result.edges()),
+                List.copyOf(result.outlets()), List.copyOf(result.courses()), List.copyOf(result.cavePlans()));
+        diagnostics = List.copyOf(diagnostics);
+    }
+
     HydrologyOwnerDraft withoutFootprintCompiler() {
         if (footprintCompiler == null) {
             return this;

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyPlanner.java

@@ -214,33 +214,12 @@ public final class HydrologyPlanner {
         return settings;
     }
 
-    /**
-     * A tile with the same identity as a planned tile but no rivers, used when planning the tile
-     * failed and terrain there must still generate.
-     */
-    public HydrologyTile emptyTile(HydrologyTileKey key) {
-        Objects.requireNonNull(key, "key");
-        return new HydrologyTile(
-                key,
-                worldSeed,
-                settings.fingerprint(),
-                settings.routing().tileSize(),
-                List.of(),
-                List.of(),
-                List.of(),
-                List.of(),
-                Set.of(),
-                List.of(),
-                List.of(),
-                RiverFootprint.empty()
-        );
-    }
-
     public HydrologyTile plan(HydrologyTileKey key) {
         long started = System.nanoTime();
         CrossTileResolution resolution = resolveCrossTileOwner(key);
         long materializeStarted = System.nanoTime();
-        HydrologyTile tile = crossTile.materializeAcceptedTile(resolution);
+        HydrologyTile tile = crossTile.materializeAcceptedTile(resolution)
+                .withResolvedOwner(new CrossTileResolvedOwner(resolution.draft(), resolution.observedRejections()));
         long finished = System.nanoTime();
         IrisLogging.debug(
                 "Hydrology tile %d,%d planned in %dms: owners=%d resolve=%dms materialize=%dms courses=%d on %s",
@@ -277,32 +256,10 @@ public final class HydrologyPlanner {
                 || tile.tileSize() != settings.routing().tileSize()) {
             throw new IllegalArgumentException("Hydrology tile does not match this planner.");
         }
-        ArrayList<RiverCourse> localCourses = new ArrayList<>(tile.courses().size());
-        for (RiverCourse course : tile.courses()) {
-            if (!tile.regionalCourseIds().contains(course.id())) {
-                localCourses.add(course);
-            }
+        CrossTileResolvedOwner owner = tile.resolvedOwner();
+        if (owner != null) {
+            resolvedOwners.asMap().putIfAbsent(tile.key(), owner);
         }
-        ArrayList<HydrologyCavePlan> localPlans = new ArrayList<>(tile.cavePlans().size());
-        for (HydrologyCavePlan plan : tile.cavePlans()) {
-            if (!tile.regionalCourseIds().contains(plan.source().sourceId())) {
-                localPlans.add(plan);
-            }
-        }
-        HydrologyCaveCourseFilter.Result result = new HydrologyCaveCourseFilter.Result(
-                tile.nodes(),
-                tile.edges(),
-                tile.outlets(),
-                localCourses,
-                localPlans
-        );
-        HydrologyOwnerDraft draft = new HydrologyOwnerDraft(
-                tile.key(),
-                result,
-                tile.localDiagnosticCandidates(),
-                null
-        );
-        resolvedOwners.put(tile.key(), new CrossTileResolvedOwner(draft, List.of()));
     }
 
     CrossTileResolution resolveCrossTileOwner(HydrologyTileKey key) {
@@ -386,6 +343,11 @@ public final class HydrologyPlanner {
         if (candidateKeys.size() < 2 || !IrisPlatforms.isBound()) {
             ArrayList<CrossTileResolvedOwner> resolved = new ArrayList<>(candidateKeys.size());
             for (HydrologyTileKey candidateKey : candidateKeys) {
+                CrossTileResolvedOwner local = context.resolved(candidateKey);
+                if (local != null) {
+                    resolved.add(local);
+                    continue;
+                }
                 HydrologyForkJoin.Task<CrossTileResolvedOwner> prepared = preparedOwners.get(candidateKey);
                 CrossTileResolvedOwner owner = prepared == null
                         ? resolveCrossTileOwner(candidateKey, context, false) : prepared.await();
@@ -397,16 +359,25 @@ public final class HydrologyPlanner {
         // Neighbour drafts use the current pool (or the burst pool from outside any pool).
         // Waiting workers claim their own tasks without helping unrelated owner drafts.
         ArrayList<Callable<CrossTileResolvedOwner>> tasks = new ArrayList<>(candidateKeys.size());
+        ArrayList<CrossTileResolvedOwner> resolved = new ArrayList<>(candidateKeys.size());
         for (HydrologyTileKey candidateKey : candidateKeys) {
+            CrossTileResolvedOwner local = context.resolved(candidateKey);
+            resolved.add(local);
+            if (local != null) {
+                continue;
+            }
             HydrologyForkJoin.Task<CrossTileResolvedOwner> prepared = preparedOwners.get(candidateKey);
             tasks.add(prepared == null ? () -> resolveIndependentOwner(candidateKey) : prepared::await);
         }
         List<CrossTileResolvedOwner> owners = HydrologyForkJoin.invokeAll(tasks, MultiBurst.burst);
-        ArrayList<CrossTileResolvedOwner> resolved = new ArrayList<>(candidateKeys.size());
+        int completed = 0;
         for (int index = 0; index < candidateKeys.size(); index++) {
-            CrossTileResolvedOwner owner = owners.get(index);
+            if (resolved.get(index) != null) {
+                continue;
+            }
+            CrossTileResolvedOwner owner = owners.get(completed++);
             context.remember(candidateKeys.get(index), owner);
-            resolved.add(owner);
+            resolved.set(index, owner);
         }
         return List.copyOf(resolved);
     }

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyTile.java

@@ -34,6 +34,7 @@ public final class HydrologyTile {
     private final Map<Long, RiverOutlet> outletsById;
     private final Map<Long, HydrologyCavePlan> cavePlansByCourseId;
     private final List<HydrologyFeatureRef> features;
+    private final CrossTileResolvedOwner resolvedOwner;
 
     public HydrologyTile(
             HydrologyTileKey key,
@@ -76,6 +77,39 @@ public final class HydrologyTile {
         validateGraph();
         validateCourses();
         this.features = collectFeatures(footprint);
+        this.resolvedOwner = null;
+    }
+
+    private HydrologyTile(HydrologyTile tile, CrossTileResolvedOwner resolvedOwner) {
+        this.key = tile.key;
+        this.worldSeed = tile.worldSeed;
+        this.settingsFingerprint = tile.settingsFingerprint;
+        this.tileSize = tile.tileSize;
+        this.nodes = tile.nodes;
+        this.edges = tile.edges;
+        this.outlets = tile.outlets;
+        this.courses = tile.courses;
+        this.regionalCourseIds = tile.regionalCourseIds;
+        this.cavePlans = tile.cavePlans;
+        this.localDiagnosticCandidates = tile.localDiagnosticCandidates;
+        this.footprint = tile.footprint;
+        this.nodesById = tile.nodesById;
+        this.outletsById = tile.outletsById;
+        this.cavePlansByCourseId = tile.cavePlansByCourseId;
+        this.features = tile.features;
+        this.resolvedOwner = resolvedOwner;
+    }
+
+    HydrologyTile withResolvedOwner(CrossTileResolvedOwner owner) {
+        Objects.requireNonNull(owner, "owner");
+        if (!key.equals(owner.draft().key())) {
+            throw new IllegalArgumentException("Resolved hydrology owner does not match its tile.");
+        }
+        return new HydrologyTile(this, owner.withoutFootprintCompiler());
+    }
+
+    CrossTileResolvedOwner resolvedOwner() {
+        return resolvedOwner;
     }
 
     public HydrologyTileKey key() {

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyTileCache.java

@@ -316,7 +316,7 @@ public final class HydrologyTileCache implements AutoCloseable {
         }
         try {
             present = tiles.getIfPresent(key);
-            HydrologyTile tile = present == null ? planOrEmpty(key, epoch) : present;
+            HydrologyTile tile = present == null ? planRequired(key, epoch) : present;
             synchronized (publicationLock) {
                 if (!closed.get() && cacheEpoch.get() == epoch) {
                     tiles.put(key, tile);
@@ -332,69 +332,107 @@ public final class HydrologyTileCache implements AutoCloseable {
         }
     }
 
-    /**
-     * A tile whose planning throws is published without rivers instead of failing the chunks that
-     * asked for it: one bad column must not take the chunk system down. The failure is logged in
-     * full so the cause can be traced, and the empty tile is cached like any other so the session
-     * stays consistent. A plan that was interrupted is not a bad tile: it is rethrown without being
-     * cached so the next request plans it again.
-     */
-    private HydrologyTile planOrEmpty(HydrologyTileKey key, long planningEpoch) {
+    private HydrologyTile planRequired(HydrologyTileKey key, long planningEpoch) {
         SharedTileKey sharedKey = sharedCacheScope == null ? null : new SharedTileKey(sharedCacheScope, key);
-        HydrologyTile shared = sharedKey == null ? null : SHARED_TILES.getIfPresent(sharedKey);
-        if (shared != null && validSharedTile(shared, sharedKey)) {
-            PreparedHydrologyTileStore store = persistentStore;
-            if (store != null && store.load(key).isEmpty()) {
-                persistTile(store, shared);
-            }
-            planner.reuseResolvedTile(shared);
-            IrisLogging.debug("Reused shared prepared hydrology tile %d,%d", key.tileX(), key.tileZ());
-            return shared;
-        }
-        if (shared != null) {
-            SHARED_TILES.invalidate(sharedKey);
-        }
         PreparedHydrologyTileStore store = persistentStore;
-        try (HydrologyPlanningAdmission.Permit ignored = HydrologyPlanningAdmission.acquireRoot(closed::get)) {
-            return planAdmitted(key, planningEpoch, sharedKey, store);
+        long attempt = 0L;
+        long retryDelayMillis = 250L;
+        long nextFailureLog = 0L;
+        while (true) {
+            requirePlanningActive();
+            try {
+                if (attempt == 0L && sharedKey != null) {
+                    HydrologyTile shared = SHARED_TILES.getIfPresent(sharedKey);
+                    if (shared != null && validSharedTile(shared, sharedKey)) {
+                        planner.reuseResolvedTile(shared);
+                        if (store != null && !store.contains(key)) {
+                            persistTile(store, shared);
+                        }
+                        IrisLogging.debug("Reused shared prepared hydrology tile %d,%d", key.tileX(), key.tileZ());
+                        return shared;
+                    }
+                    if (shared != null) {
+                        SHARED_TILES.invalidate(sharedKey);
+                    }
+                }
+                try (HydrologyPlanningAdmission.Permit ignored = HydrologyPlanningAdmission.acquireRoot(
+                        closed::get)) {
+                    return planAdmitted(key, planningEpoch, sharedKey, store, attempt == 0L);
+                }
+            } catch (RuntimeException failure) {
+                if (failure instanceof CancellationException || interrupted(failure)) {
+                    throw failure;
+                }
+                requirePlanningActive();
+                attempt++;
+                long now = System.nanoTime();
+                if (nextFailureLog == 0L || now - nextFailureLog >= 0L) {
+                    IrisLogging.error("Hydrology tile " + key.tileX() + "," + key.tileZ()
+                            + " failed planning attempt " + attempt + "; retrying in " + retryDelayMillis
+                            + " ms. Generation is waiting for its river plan: " + failure.getMessage());
+                    IrisLogging.reportError(failure);
+                    nextFailureLog = now + TimeUnit.SECONDS.toNanos(30L);
+                }
+                if (sharedKey != null) {
+                    SHARED_TILES.invalidate(sharedKey);
+                }
+                planner.clearOwnerDrafts();
+                awaitPlanningRetry(retryDelayMillis);
+                retryDelayMillis = Math.min(5000L, retryDelayMillis * 2L);
+            }
+        }
+    }
+
+    private void requirePlanningActive() {
+        requireOpen();
+        if (Thread.currentThread().isInterrupted()) {
+            throw new CancellationException("Hydrology plan retry interrupted.");
+        }
+    }
+
+    private void awaitPlanningRetry(long delayMillis) {
+        long deadline = System.nanoTime() + TimeUnit.MILLISECONDS.toNanos(delayMillis);
+        while (true) {
+            requirePlanningActive();
+            long remaining = deadline - System.nanoTime();
+            if (remaining <= 0L) {
+                return;
+            }
+            try {
+                TimeUnit.NANOSECONDS.sleep(Math.min(remaining, TimeUnit.MILLISECONDS.toNanos(100L)));
+            } catch (InterruptedException interruption) {
+                Thread.currentThread().interrupt();
+                throw new CancellationException("Hydrology plan retry interrupted.");
+            }
         }
     }
 
     private HydrologyTile planAdmitted(HydrologyTileKey key, long planningEpoch,
-                                       SharedTileKey sharedKey, PreparedHydrologyTileStore store) {
-        if (store != null) {
+                                       SharedTileKey sharedKey, PreparedHydrologyTileStore store,
+                                       boolean reusePrepared) {
+        if (store != null && reusePrepared) {
             HydrologyTile persisted = store.load(key).orElse(null);
             if (persisted != null) {
-                SHARED_TILES.put(sharedKey, persisted);
                 planner.reuseResolvedTile(persisted);
+                SHARED_TILES.put(sharedKey, persisted);
                 IrisLogging.debug("Loaded persisted prepared hydrology tile %d,%d", key.tileX(), key.tileZ());
                 return persisted;
             }
         }
         prepareTerrain();
-        try {
-            HydrologyTile planned = planner.plan(key);
-            synchronized (publicationLock) {
-                if (sharedKey != null && !closed.get() && planningEpoch == cacheEpoch.get()) {
-                    HydrologyTile existing = SHARED_TILES.asMap().putIfAbsent(sharedKey, planned);
-                    if (existing == null) {
-                        IrisLogging.debug("Published shared prepared hydrology tile %d,%d", key.tileX(), key.tileZ());
-                    }
+        HydrologyTile planned = planner.plan(key);
+        synchronized (publicationLock) {
+            if (sharedKey != null && !closed.get() && planningEpoch == cacheEpoch.get()) {
+                HydrologyTile existing = SHARED_TILES.asMap().putIfAbsent(sharedKey, planned);
+                if (existing == null) {
+                    IrisLogging.debug("Published shared prepared hydrology tile %d,%d", key.tileX(), key.tileZ());
                 }
             }
-            if (store != null && !closed.get() && planningEpoch == cacheEpoch.get()) {
-                persistTile(store, planned);
-            }
-            return planned;
-        } catch (RuntimeException failure) {
-            if (failure instanceof CancellationException || interrupted(failure)) {
-                throw failure;
-            }
-            IrisLogging.error("Hydrology tile " + key.tileX() + "," + key.tileZ()
-                    + " failed to plan and generates without rivers: " + failure.getMessage());
-            IrisLogging.reportError(failure);
-            return planner.emptyTile(key);
         }
+        if (store != null && !closed.get() && planningEpoch == cacheEpoch.get()) {
+            persistTile(store, planned);
+        }
+        return planned;
     }
 
     private void persistTile(PreparedHydrologyTileStore store, HydrologyTile tile) {

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyTileCodec.java

@@ -0,0 +1,706 @@
+package art.arcane.iris.generation.hydrology;
+
+import art.arcane.iris.generation.hydrology.cave.CavePosition;
+import art.arcane.iris.generation.hydrology.cave.HydrologyCaveMode;
+import art.arcane.iris.generation.hydrology.cave.HydrologyCavePlan;
+import art.arcane.iris.generation.hydrology.cave.HydrologyCaveRejection;
+import art.arcane.iris.generation.hydrology.cave.HydrologyCaveSource;
+import art.arcane.iris.generation.hydrology.policy.SurfaceRiverPolicy;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.OptionalLong;
+import java.util.Set;
+
+final class HydrologyTileCodec {
+    private static final int MAGIC = 0x49524854;
+    private static final int FORMAT = 2;
+    private static final long MAXIMUM_ALLOCATION_BYTES = Math.max(16L * 1024L * 1024L,
+            Math.min(512L * 1024L * 1024L, Runtime.getRuntime().maxMemory() / 8L));
+    private static final int MAXIMUM_COLLECTION_SIZE = 2_000_000;
+    private static final HydrologyFeatureType[] HYDROLOGY_FEATURE_TYPE_VALUES = HydrologyFeatureType.values();
+    private static final RiverCourseType[] RIVER_COURSE_TYPE_VALUES = RiverCourseType.values();
+    private static final HydrologyCandidateKind[] HYDROLOGY_CANDIDATE_KIND_VALUES = HydrologyCandidateKind.values();
+    private static final HydrologyCandidateRejection[] HYDROLOGY_CANDIDATE_REJECTION_VALUES = HydrologyCandidateRejection.values();
+    private static final HydrologyCaveMode[] HYDROLOGY_CAVE_MODE_VALUES = HydrologyCaveMode.values();
+    private static final HydrologyCaveRejection[] HYDROLOGY_CAVE_REJECTION_VALUES = HydrologyCaveRejection.values();
+
+    private final Map<String, String> strings = new HashMap<>();
+    private long remainingAllocation = MAXIMUM_ALLOCATION_BYTES;
+
+    void write(DataOutputStream output, HydrologyTile tile, String scopeIdentity) throws IOException {
+        output.writeInt(MAGIC);
+        output.writeInt(FORMAT);
+        output.writeUTF(scopeIdentity);
+        output.writeInt(tile.key().tileX());
+        output.writeInt(tile.key().tileZ());
+        output.writeLong(tile.worldSeed());
+        output.writeLong(tile.settingsFingerprint());
+        output.writeInt(tile.tileSize());
+        writeList(output, tile.nodes(), this::writeDrainageNode);
+        writeList(output, tile.edges(), this::writeDrainageEdge);
+        writeList(output, tile.outlets(), this::writeRiverOutlet);
+        writeList(output, tile.courses(), this::writeRiverCourse);
+        writeCount(output, tile.regionalCourseIds().size(), 64);
+        for (long id : tile.regionalCourseIds()) {
+            output.writeLong(id);
+        }
+        writeList(output, tile.cavePlans(), this::writeCavePlan);
+        writeList(output, tile.localDiagnosticCandidates(), this::writeHydrologyDiagnosticCandidate);
+        writeCount(output, tile.footprint().columns().size(), 256);
+        for (HydrologyColumnSample column : tile.footprint().columns().values()) {
+            writeHydrologyColumnSample(output, column);
+        }
+        output.writeBoolean(tile.resolvedOwner() != null);
+        if (tile.resolvedOwner() != null) {
+            writeResolvedOwner(output, tile);
+        }
+    }
+
+    HydrologyTile read(DataInputStream input, String scopeIdentity, HydrologyTileKey key,
+                       HydrologyTileCache.SharedCacheScope scope, int expectedTileSize) throws IOException {
+        if (input.readInt() != MAGIC || input.readInt() != FORMAT || !scopeIdentity.equals(input.readUTF())
+                || input.readInt() != key.tileX() || input.readInt() != key.tileZ()
+                || input.readLong() != scope.worldSeed() || input.readLong() != scope.settingsFingerprint()
+                || input.readInt() != expectedTileSize) {
+            throw new IOException("Prepared hydrology tile header does not match its scope.");
+        }
+        List<DrainageNode> nodes = readList(input, this::readDrainageNode);
+        List<DrainageEdge> edges = readList(input, this::readDrainageEdge);
+        List<RiverOutlet> outlets = readList(input, this::readRiverOutlet);
+        List<RiverCourse> courses = readList(input, this::readRiverCourse);
+        int regionalCount = readCount(input, 64);
+        Set<Long> regionalCourseIds = HashSet.newHashSet(regionalCount);
+        for (int index = 0; index < regionalCount; index++) {
+            if (!regionalCourseIds.add(input.readLong())) {
+                throw new IOException("Duplicate regional hydrology course.");
+            }
+        }
+        List<HydrologyCavePlan> cavePlans = readList(input, this::readCavePlan);
+        List<HydrologyDiagnosticCandidate> candidates = readList(input, this::readHydrologyDiagnosticCandidate);
+        int columnCount = readCount(input, 256);
+        Map<Long, HydrologyColumnSample> columns = HashMap.newHashMap(columnCount);
+        for (int index = 0; index < columnCount; index++) {
+            HydrologyColumnSample column = readHydrologyColumnSample(input);
+            if (columns.put(RiverFootprint.pack(column.x(), column.z()), column) != null) {
+                throw new IOException("Duplicate hydrology footprint column.");
+            }
+        }
+        HydrologyTile tile = new HydrologyTile(key, scope.worldSeed(), scope.settingsFingerprint(), expectedTileSize,
+                nodes, edges, outlets, courses, regionalCourseIds, cavePlans, candidates,
+                new RiverFootprint(columns));
+        if (input.readBoolean()) {
+            tile = tile.withResolvedOwner(readResolvedOwner(input, tile));
+        }
+        if (input.read() != -1) {
+            throw new IOException("Unexpected data after prepared hydrology tile.");
+        }
+        return tile;
+    }
+
+    private void writeResolvedOwner(DataOutputStream output, HydrologyTile tile) throws IOException {
+        allocate(256L);
+        CrossTileResolvedOwner owner = tile.resolvedOwner();
+        HydrologyCaveCourseFilter.Result result = owner.draft().result();
+        writeOwnerList(output, result.nodes(), tile.nodes(), this::writeDrainageNode);
+        writeOwnerList(output, result.edges(), tile.edges(), this::writeDrainageEdge);
+        writeOwnerList(output, result.outlets(), tile.outlets(), this::writeRiverOutlet);
+        writeOwnerList(output, result.courses(), tile.courses(), this::writeRiverCourse);
+        writeOwnerList(output, result.cavePlans(), tile.cavePlans(), this::writeCavePlan);
+        writeOwnerList(output, owner.draft().diagnostics(), tile.localDiagnosticCandidates(),
+                this::writeHydrologyDiagnosticCandidate);
+        writeList(output, owner.observedRejections(), this::writeRejectedCourse);
+    }
+
+    private CrossTileResolvedOwner readResolvedOwner(DataInputStream input, HydrologyTile tile) throws IOException {
+        allocate(256L);
+        HydrologyCaveCourseFilter.Result result = new HydrologyCaveCourseFilter.Result(
+                readOwnerList(input, tile.nodes(), this::readDrainageNode),
+                readOwnerList(input, tile.edges(), this::readDrainageEdge),
+                readOwnerList(input, tile.outlets(), this::readRiverOutlet),
+                readOwnerList(input, tile.courses(), this::readRiverCourse),
+                readOwnerList(input, tile.cavePlans(), this::readCavePlan));
+        List<HydrologyDiagnosticCandidate> diagnostics = readOwnerList(input, tile.localDiagnosticCandidates(),
+                this::readHydrologyDiagnosticCandidate);
+        return new CrossTileResolvedOwner(new HydrologyOwnerDraft(tile.key(), result, diagnostics, null),
+                readList(input, this::readRejectedCourse));
+    }
+
+    private void writeRejectedCourse(DataOutputStream output, CrossTileRejectedCourse rejection) throws IOException {
+        writeRiverCourse(output, rejection.course());
+        output.writeLong(rejection.winnerSourceId());
+    }
+
+    private CrossTileRejectedCourse readRejectedCourse(DataInputStream input) throws IOException {
+        return new CrossTileRejectedCourse(readRiverCourse(input), input.readLong());
+    }
+
+    private <T> void writeOwnerList(DataOutputStream output, List<T> values, List<T> published,
+                                    ElementWriter<T> writer) throws IOException {
+        writeCount(output, values.size(), 16);
+        Map<T, Integer> indexes = new IdentityHashMap<>(published.size());
+        for (int index = 0; index < published.size(); index++) {
+            indexes.put(published.get(index), index);
+        }
+        for (T value : values) {
+            Integer index = indexes.get(value);
+            output.writeInt(index == null ? -1 : index);
+            if (index == null) {
+                allocate(256L);
+                writer.write(output, value);
+            }
+        }
+    }
+
+    private <T> List<T> readOwnerList(DataInputStream input, List<T> published, ElementReader<T> reader) throws IOException {
+        int count = readCount(input, 16);
+        List<T> values = new ArrayList<>(Math.min(count, 4096));
+        for (int index = 0; index < count; index++) {
+            int reference = input.readInt();
+            if (reference == -1) {
+                allocate(256L);
+                values.add(reader.read(input));
+            } else if (reference >= 0 && reference < published.size()) {
+                values.add(published.get(reference));
+            } else {
+                throw new IOException("Invalid prepared hydrology owner reference.");
+            }
+        }
+        return List.copyOf(values);
+    }
+
+    private void writeCavePlan(DataOutputStream output, HydrologyCavePlan plan) throws IOException {
+        writeHydrologyCaveSource(output, plan.source());
+        output.writeByte(plan.rejection().ordinal());
+        writeOptionalLong(output, plan.arbitrationWinnerSourceId());
+        validateCount(plan.baselinePreconditions().size(), 96);
+        plan.writeCells(output);
+    }
+
+    private HydrologyCavePlan readCavePlan(DataInputStream input) throws IOException {
+        HydrologyCaveSource source = readHydrologyCaveSource(input);
+        HydrologyCaveRejection rejection = readEnum(input, HYDROLOGY_CAVE_REJECTION_VALUES);
+        OptionalLong winner = readOptionalLong(input);
+        int cells = readCount(input, 96);
+        return HydrologyCavePlan.readCells(source, rejection, winner, input, cells);
+    }
+
+    private void writeHydraulicChannelProfile(DataOutputStream output, HydraulicChannelProfile profile) throws IOException {
+        writeCount(output, profile.size(), 32);
+        for (int station = 0; station < profile.size(); station++) {
+            output.writeDouble(profile.widthAt(station));
+            output.writeDouble(profile.depthAt(station));
+        }
+    }
+
+    private HydraulicChannelProfile readHydraulicChannelProfile(DataInputStream input) throws IOException {
+        int count = readCount(input, 32);
+        double[] widths = new double[count];
+        double[] depths = new double[count];
+        for (int station = 0; station < count; station++) {
+            widths[station] = input.readDouble();
+            depths[station] = input.readDouble();
+        }
+        return new HydraulicChannelProfile(widths, depths);
+    }
+
+    private void writeDrainageNode(DataOutputStream output, DrainageNode value) throws IOException {
+        output.writeLong(value.id());
+        output.writeInt(value.x());
+        output.writeInt(value.z());
+        writeHydrologyTerrainSample(output, value.terrain());
+        output.writeDouble(value.potential());
+        output.writeLong(value.outletId());
+    }
+
+    private DrainageNode readDrainageNode(DataInputStream input) throws IOException {
+        return new DrainageNode(
+                input.readLong(),
+                input.readInt(),
+                input.readInt(),
+                readHydrologyTerrainSample(input),
+                input.readDouble(),
+                input.readLong()
+        );
+    }
+
+    private void writeDrainageEdge(DataOutputStream output, DrainageEdge value) throws IOException {
+        output.writeLong(value.id());
+        output.writeLong(value.upstreamNodeId());
+        output.writeLong(value.downstreamNodeId());
+        output.writeLong(value.outletId());
+        output.writeDouble(value.cost());
+        output.writeInt(value.contributingSurfaceSources());
+        output.writeInt(value.contributingUndergroundSources());
+        writeList(output, value.centerline(), this::writeHydrologyPoint);
+    }
+
+    private DrainageEdge readDrainageEdge(DataInputStream input) throws IOException {
+        return new DrainageEdge(
+                input.readLong(),
+                input.readLong(),
+                input.readLong(),
+                input.readLong(),
+                input.readDouble(),
+                input.readInt(),
+                input.readInt(),
+                readList(input, this::readHydrologyPoint)
+        );
+    }
+
+    private void writeHydrologyTerrainSample(DataOutputStream output, HydrologyTerrainSample value) throws IOException {
+        output.writeInt(value.naturalHeight());
+        output.writeDouble(value.slope());
+        output.writeBoolean(value.ocean());
+        output.writeBoolean(value.caveAvailable());
+        output.writeInt(value.caveFloorY());
+        output.writeInt(value.caveFluidY());
+        output.writeBoolean(value.transitAllowed());
+        output.writeBoolean(value.outletAllowed());
+        output.writeBoolean(value.surfaceSourceAllowed());
+        output.writeBoolean(value.surfaceSourceRequired());
+        output.writeBoolean(value.undergroundSourceAllowed());
+        output.writeBoolean(value.undergroundSourceRequired());
+        output.writeDouble(value.routingCost());
+        output.writeDouble(value.surfaceSourceWeight());
+        output.writeDouble(value.undergroundSourceWeight());
+        output.writeDouble(value.widthMultiplier());
+        output.writeDouble(value.depthMultiplier());
+        output.writeDouble(value.incisionMultiplier());
+        output.writeDouble(value.routingMultiplier());
+        output.writeDouble(value.bankMultiplier());
+        writeString(output, value.parentBiomeKey());
+        writeString(output, value.surfaceBiomeKey());
+        writeString(output, value.mouthBiomeKey());
+        writeString(output, value.shoreBiomeKey());
+        writeString(output, value.bankBiomeKey());
+        writeString(output, value.floodedCaveBiomeKey());
+        writeList(output, value.preferredProfileKeys(), this::writeString);
+        writeList(output, value.surfacePoolKeys(), this::writeString);
+        output.writeDouble(value.shoreBiomeWidth());
+        writeString(output, value.confinesKey());
+        output.writeDouble(value.shoreWidth());
+        output.writeBoolean(value.erosion());
+        writeSurfaceRiverPolicy(output, value.surfacePolicy());
+    }
+
+    private HydrologyTerrainSample readHydrologyTerrainSample(DataInputStream input) throws IOException {
+        return new HydrologyTerrainSample(
+                input.readInt(),
+                input.readDouble(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readInt(),
+                input.readInt(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                input.readDouble(),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input),
+                readList(input, this::readString),
+                readList(input, this::readString),
+                input.readDouble(),
+                readString(input),
+                input.readDouble(),
+                input.readBoolean(),
+                readSurfaceRiverPolicy(input)
+        );
+    }
+
+    private void writeRiverOutlet(DataOutputStream output, RiverOutlet value) throws IOException {
+        output.writeLong(value.id());
+        output.writeByte(value.type().ordinal());
+        output.writeLong(value.drainageNodeId());
+        writeHydrologyPoint(output, value.landwardPoint());
+        writeHydrologyPoint(output, value.connectionPoint());
+        output.writeInt(value.seaLevel());
+        output.writeBoolean(value.directOcean());
+    }
+
+    private RiverOutlet readRiverOutlet(DataInputStream input) throws IOException {
+        return new RiverOutlet(
+                input.readLong(),
+                readEnum(input, HYDROLOGY_FEATURE_TYPE_VALUES),
+                input.readLong(),
+                readHydrologyPoint(input),
+                readHydrologyPoint(input),
+                input.readInt(),
+                input.readBoolean()
+        );
+    }
+
+    private void writeRiverCourse(DataOutputStream output, RiverCourse value) throws IOException {
+        output.writeLong(value.id());
+        output.writeByte(value.type().ordinal());
+        writeOptionalLong(output, value.sourceNodeId());
+        writeOptionalLong(output, value.outletId());
+        writeString(output, value.profileKey());
+        output.writeInt(value.discharge());
+        writeList(output, value.drainageEdges(), this::writeDrainageEdge);
+        writeList(output, value.segments(), this::writeHydraulicSegment);
+    }
+
+    private RiverCourse readRiverCourse(DataInputStream input) throws IOException {
+        return new RiverCourse(
+                input.readLong(),
+                readEnum(input, RIVER_COURSE_TYPE_VALUES),
+                readOptionalLong(input),
+                readOptionalLong(input),
+                readString(input),
+                input.readInt(),
+                readList(input, this::readDrainageEdge),
+                readList(input, this::readHydraulicSegment)
+        );
+    }
+
+    private void writeHydraulicSegment(DataOutputStream output, HydraulicSegment value) throws IOException {
+        output.writeLong(value.id());
+        output.writeLong(value.courseId());
+        output.writeByte(value.type().ordinal());
+        output.writeInt(value.upstreamHeadY());
+        output.writeInt(value.downstreamHeadY());
+        output.writeInt(value.width());
+        output.writeInt(value.depth());
+        output.writeBoolean(value.fallingFluid());
+        output.writeBoolean(value.receivingPool());
+        writeList(output, value.centerline(), this::writeHydrologyPoint);
+        writeHydraulicChannelProfile(output, value.channelProfile());
+    }
+
+    private HydraulicSegment readHydraulicSegment(DataInputStream input) throws IOException {
+        return new HydraulicSegment(
+                input.readLong(),
+                input.readLong(),
+                readEnum(input, HYDROLOGY_FEATURE_TYPE_VALUES),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readBoolean(),
+                input.readBoolean(),
+                readList(input, this::readHydrologyPoint),
+                readHydraulicChannelProfile(input)
+        );
+    }
+
+    private void writeHydrologyDiagnosticCandidate(DataOutputStream output, HydrologyDiagnosticCandidate value) throws IOException {
+        output.writeLong(value.id());
+        output.writeByte(value.kind().ordinal());
+        output.writeByte(value.projectedType().ordinal());
+        writeHydrologyPoint(output, value.point());
+        output.writeByte(value.rejection().ordinal());
+        output.writeInt(value.detail());
+    }
+
+    private HydrologyDiagnosticCandidate readHydrologyDiagnosticCandidate(DataInputStream input) throws IOException {
+        return new HydrologyDiagnosticCandidate(
+                input.readLong(),
+                readEnum(input, HYDROLOGY_CANDIDATE_KIND_VALUES),
+                readEnum(input, HYDROLOGY_FEATURE_TYPE_VALUES),
+                readHydrologyPoint(input),
+                readEnum(input, HYDROLOGY_CANDIDATE_REJECTION_VALUES),
+                input.readInt()
+        );
+    }
+
+    private void writeHydrologyColumnSample(DataOutputStream output, HydrologyColumnSample value) throws IOException {
+        output.writeInt(value.x());
+        output.writeInt(value.z());
+        output.writeInt(value.naturalHeight());
+        output.writeInt(value.seaLevel());
+        output.writeBoolean(value.ocean());
+        writeString(output, value.parentBiomeKey());
+        writeList(output, value.layers(), this::writeHydrologyColumnLayer);
+    }
+
+    private HydrologyColumnSample readHydrologyColumnSample(DataInputStream input) throws IOException {
+        return new HydrologyColumnSample(
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readBoolean(),
+                readString(input),
+                readList(input, this::readHydrologyColumnLayer)
+        );
+    }
+
+    private void writeHydrologyColumnLayer(DataOutputStream output, HydrologyColumnLayer value) throws IOException {
+        writeHydrologyFeatureRef(output, value.feature());
+        output.writeInt(value.bedY());
+        output.writeInt(value.fluidHeadY());
+        output.writeInt(value.ceilingY());
+        output.writeBoolean(value.channel());
+        output.writeBoolean(value.shore());
+        output.writeBoolean(value.grading());
+        output.writeBoolean(value.connectedFluid());
+        output.writeBoolean(value.fallingFluid());
+        output.writeBoolean(value.receivingPool());
+        output.writeBoolean(value.terrainOwned());
+        output.writeBoolean(value.fluidOwned());
+        output.writeBoolean(value.oceanApron());
+        writeString(output, value.profileKey());
+        writeString(output, value.surfaceBiomeKey());
+        writeString(output, value.mouthBiomeKey());
+        writeString(output, value.shoreBiomeKey());
+        writeString(output, value.bankBiomeKey());
+        writeString(output, value.floodedCaveBiomeKey());
+    }
+
+    private HydrologyColumnLayer readHydrologyColumnLayer(DataInputStream input) throws IOException {
+        return new HydrologyColumnLayer(
+                readHydrologyFeatureRef(input),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                input.readBoolean(),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input),
+                readString(input)
+        );
+    }
+
+    private void writeHydrologyFeatureRef(DataOutputStream output, HydrologyFeatureRef value) throws IOException {
+        output.writeLong(value.id());
+        output.writeByte(value.type().ordinal());
+        output.writeLong(value.courseId());
+        output.writeLong(value.segmentId());
+        output.writeInt(value.x());
+        output.writeInt(value.y());
+        output.writeInt(value.z());
+        output.writeInt(value.flowDeltaX());
+        output.writeInt(value.flowDeltaZ());
+        output.writeBoolean(value.source());
+    }
+
+    private HydrologyFeatureRef readHydrologyFeatureRef(DataInputStream input) throws IOException {
+        return new HydrologyFeatureRef(
+                input.readLong(),
+                readEnum(input, HYDROLOGY_FEATURE_TYPE_VALUES),
+                input.readLong(),
+                input.readLong(),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readInt(),
+                input.readBoolean()
+        );
+    }
+
+    private void writeHydrologyPoint(DataOutputStream output, HydrologyPoint value) throws IOException {
+        output.writeInt(value.x());
+        output.writeInt(value.y());
+        output.writeInt(value.z());
+    }
+
+    private HydrologyPoint readHydrologyPoint(DataInputStream input) throws IOException {
+        return new HydrologyPoint(
+                input.readInt(),
+                input.readInt(),
+                input.readInt()
+        );
+    }
+
+    private void writeHydrologyCaveSource(DataOutputStream output, HydrologyCaveSource value) throws IOException {
+        output.writeLong(value.sourceId());
+        writeCavePosition(output, value.entry());
+        writeCavePosition(output, value.target());
+        output.writeInt(value.waterHeadY());
+        output.writeByte(value.mode().ordinal());
+    }
+
+    private HydrologyCaveSource readHydrologyCaveSource(DataInputStream input) throws IOException {
+        return new HydrologyCaveSource(
+                input.readLong(),
+                readCavePosition(input),
+                readCavePosition(input),
+                input.readInt(),
+                readEnum(input, HYDROLOGY_CAVE_MODE_VALUES)
+        );
+    }
+
+    private void writeCavePosition(DataOutputStream output, CavePosition value) throws IOException {
+        output.writeInt(value.x());
+        output.writeInt(value.y());
+        output.writeInt(value.z());
+    }
+
+    private CavePosition readCavePosition(DataInputStream input) throws IOException {
+        return new CavePosition(
+                input.readInt(),
+                input.readInt(),
+                input.readInt()
+        );
+    }
+
+    private void writeSurfaceRiverPolicy(DataOutputStream output, SurfaceRiverPolicy value) throws IOException {
+        writeString(output, value.areaKey());
+        writeDouble(output, value.sourceDensity());
+        writeInteger(output, value.sourceSpacing());
+        writeInteger(output, value.tributaries());
+        writeInteger(output, value.inlandOutlets());
+        writeInteger(output, value.coastalOutlets());
+        writeInteger(output, value.minimumCourseLength());
+        writeInteger(output, value.maximumIncision());
+    }
+
+    private SurfaceRiverPolicy readSurfaceRiverPolicy(DataInputStream input) throws IOException {
+        return new SurfaceRiverPolicy(
+                readString(input),
+                readDouble(input),
+                readInteger(input),
+                readInteger(input),
+                readInteger(input),
+                readInteger(input),
+                readInteger(input),
+                readInteger(input)
+        );
+    }
+
+    private void writeString(DataOutputStream output, String value) throws IOException {
+        output.writeBoolean(value != null);
+        if (value != null) {
+            allocate(40L + (long) value.length() * Character.BYTES);
+            output.writeUTF(value);
+        }
+    }
+
+    private String readString(DataInputStream input) throws IOException {
+        if (!input.readBoolean()) {
+            return null;
+        }
+        String value = input.readUTF();
+        allocate(40L + (long) value.length() * Character.BYTES);
+        if (strings.size() >= 4096) {
+            return value;
+        }
+        String existing = strings.putIfAbsent(value, value);
+        return existing == null ? value : existing;
+    }
+
+    private void writeInteger(DataOutputStream output, Integer value) throws IOException {
+        output.writeBoolean(value != null);
+        if (value != null) {
+            output.writeInt(value);
+        }
+    }
+
+    private Integer readInteger(DataInputStream input) throws IOException {
+        return input.readBoolean() ? input.readInt() : null;
+    }
+
+    private void writeDouble(DataOutputStream output, Double value) throws IOException {
+        output.writeBoolean(value != null);
+        if (value != null) {
+            output.writeDouble(value);
+        }
+    }
+
+    private Double readDouble(DataInputStream input) throws IOException {
+        return input.readBoolean() ? input.readDouble() : null;
+    }
+
+    private void writeOptionalLong(DataOutputStream output, OptionalLong value) throws IOException {
+        output.writeBoolean(value.isPresent());
+        if (value.isPresent()) {
+            output.writeLong(value.getAsLong());
+        }
+    }
+
+    private OptionalLong readOptionalLong(DataInputStream input) throws IOException {
+        return input.readBoolean() ? OptionalLong.of(input.readLong()) : OptionalLong.empty();
+    }
+
+    private <T> void writeList(DataOutputStream output, List<T> values, ElementWriter<T> writer) throws IOException {
+        writeCount(output, values.size(), 256);
+        for (T value : values) {
+            writer.write(output, value);
+        }
+    }
+
+    private <T> List<T> readList(DataInputStream input, ElementReader<T> reader) throws IOException {
+        int count = readCount(input, 256);
+        List<T> values = new ArrayList<>(Math.min(count, 4096));
+        for (int index = 0; index < count; index++) {
+            values.add(reader.read(input));
+        }
+        return values;
+    }
+
+    private int readCount(DataInputStream input, int bytesPerElement) throws IOException {
+        int count = input.readInt();
+        validateCount(count, bytesPerElement);
+        return count;
+    }
+
+    private void writeCount(DataOutputStream output, int count, int bytesPerElement) throws IOException {
+        validateCount(count, bytesPerElement);
+        output.writeInt(count);
+    }
+
+    private void validateCount(int count, int bytesPerElement) throws IOException {
+        if (count < 0 || count > MAXIMUM_COLLECTION_SIZE) {
+            throw new IOException("Invalid hydrology collection length: " + count);
+        }
+        allocate((long) count * bytesPerElement);
+    }
+
+    private void allocate(long bytes) throws IOException {
+        if (bytes > remainingAllocation) {
+            throw new IOException("Prepared hydrology tile exceeds its allocation budget.");
+        }
+        remainingAllocation -= bytes;
+    }
+
+    private <T extends Enum<T>> T readEnum(DataInputStream input, T[] values) throws IOException {
+        int ordinal = input.readUnsignedByte();
+        if (ordinal >= values.length) {
+            throw new IOException("Invalid hydrology enum value: " + ordinal);
+        }
+        return values[ordinal];
+    }
+
+    @FunctionalInterface
+    private interface ElementWriter<T> {
+        void write(DataOutputStream output, T value) throws IOException;
+    }
+
+    @FunctionalInterface
+    private interface ElementReader<T> {
+        T read(DataInputStream input) throws IOException;
+    }
+}

core/src/main/java/art/arcane/iris/generation/hydrology/PreparedHydrologyTileStore.java

@@ -1,24 +1,13 @@
 package art.arcane.iris.generation.hydrology;
 
-import art.arcane.iris.generation.hydrology.cave.CavePosition;
-import art.arcane.iris.generation.hydrology.cave.CaveVoxelPrecondition;
-import art.arcane.iris.generation.hydrology.cave.HydrologyCaveAction;
-import art.arcane.iris.generation.hydrology.cave.HydrologyCavePlan;
-import art.arcane.iris.generation.hydrology.cave.HydrologyCaveRejection;
-import art.arcane.iris.generation.hydrology.cave.HydrologyCaveSource;
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
 import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.io.OutputStream;
-import java.io.OutputStreamWriter;
-import java.io.Reader;
-import java.io.Writer;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.Files;
@@ -27,29 +16,15 @@ import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
-import java.util.ArrayList;
-import java.util.Comparator;
-import java.util.HashMap;
 import java.util.HexFormat;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
-import java.util.OptionalLong;
-import java.util.Set;
 import java.util.zip.GZIPInputStream;
 import java.util.zip.GZIPOutputStream;
 
 final class PreparedHydrologyTileStore {
-    private static final int SCHEMA_VERSION = 6;
     private static final long MAXIMUM_COMPRESSED_BYTES = 128L * 1024L * 1024L;
     private static final long MAXIMUM_DECOMPRESSED_BYTES = 512L * 1024L * 1024L;
-    private static final Gson GSON = new GsonBuilder()
-            .disableHtmlEscaping()
-            .serializeSpecialFloatingPointValues()
-            .create();
-
     private final Path directory;
     private final String scopeIdentity;
     private final HydrologyTileCache.SharedCacheScope scope;
@@ -68,32 +43,27 @@ final class PreparedHydrologyTileStore {
                 .resolve(scopeIdentity);
     }
 
-    Optional<HydrologyTile> load(HydrologyTileKey key) {
+    boolean contains(HydrologyTileKey key) {
         Path file = file(key);
         try {
-            if (!Files.isRegularFile(file, LinkOption.NOFOLLOW_LINKS)
-                    || Files.isSymbolicLink(file)
-                    || Files.size(file) > MAXIMUM_COMPRESSED_BYTES) {
-                return Optional.empty();
-            }
+            return Files.isRegularFile(file, LinkOption.NOFOLLOW_LINKS)
+                    && !Files.isSymbolicLink(file)
+                    && Files.size(file) <= MAXIMUM_COMPRESSED_BYTES;
         } catch (IOException failure) {
+            return false;
+        }
+    }
+
+    Optional<HydrologyTile> load(HydrologyTileKey key) {
+        if (!contains(key)) {
             return Optional.empty();
         }
-        try (InputStream raw = Files.newInputStream(file);
+        try (InputStream raw = Files.newInputStream(file(key));
              InputStream buffered = new BufferedInputStream(raw);
-             InputStream compressed = new GZIPInputStream(buffered);
+             InputStream compressed = new GZIPInputStream(buffered, 32768);
              InputStream bounded = new LimitedInputStream(compressed, MAXIMUM_DECOMPRESSED_BYTES);
-             Reader reader = new InputStreamReader(bounded, StandardCharsets.UTF_8)) {
-            PersistedTile persisted = GSON.fromJson(reader, PersistedTile.class);
-            if (persisted == null
-                    || persisted.schemaVersion() != SCHEMA_VERSION
-                    || !scopeIdentity.equals(persisted.scopeIdentity())
-                    || !key.equals(persisted.key())
-                    || persisted.worldSeed() != scope.worldSeed()
-                    || persisted.settingsFingerprint() != scope.settingsFingerprint()) {
-                return Optional.empty();
-            }
-            HydrologyTile tile = persisted.toTile();
+             DataInputStream input = new DataInputStream(new BufferedInputStream(bounded, 32768))) {
+            HydrologyTile tile = new HydrologyTileCodec().read(input, scopeIdentity, key, scope, expectedTileSize);
             return valid(tile, key) ? Optional.of(tile) : Optional.empty();
         } catch (IOException | RuntimeException failure) {
             return Optional.empty();
@@ -110,9 +80,9 @@ final class PreparedHydrologyTileStore {
         try {
             try (OutputStream raw = Files.newOutputStream(staged);
                  OutputStream buffered = new BufferedOutputStream(raw);
-                 OutputStream compressed = new GZIPOutputStream(buffered);
-                 Writer writer = new OutputStreamWriter(compressed, StandardCharsets.UTF_8)) {
-                GSON.toJson(PersistedTile.from(tile, scopeIdentity), writer);
+                 OutputStream compressed = new GZIPOutputStream(buffered, 32768);
+                 DataOutputStream output = new DataOutputStream(new BufferedOutputStream(compressed, 32768))) {
+                new HydrologyTileCodec().write(output, tile, scopeIdentity);
             }
             if (Files.size(staged) > MAXIMUM_COMPRESSED_BYTES) {
                 throw new IOException("Prepared hydrology tile cache entry exceeds the size limit.");
@@ -128,7 +98,7 @@ final class PreparedHydrologyTileStore {
     }
 
     Path file(HydrologyTileKey key) {
-        return directory.resolve("tile-" + key.tileX() + "-" + key.tileZ() + ".json.gz");
+        return directory.resolve("tile-" + key.tileX() + "-" + key.tileZ() + ".bin.gz");
     }
 
     private boolean valid(HydrologyTile tile, HydrologyTileKey key) {
@@ -162,194 +132,6 @@ final class PreparedHydrologyTileStore {
         digest.update(bytes);
     }
 
-    private record PersistedTile(
-            int schemaVersion,
-            String scopeIdentity,
-            HydrologyTileKey key,
-            long worldSeed,
-            long settingsFingerprint,
-            int tileSize,
-            List<DrainageNode> nodes,
-            List<DrainageEdge> edges,
-            List<RiverOutlet> outlets,
-            List<PersistedCourse> courses,
-            List<Long> regionalCourseIds,
-            List<PersistedCavePlan> cavePlans,
-            List<HydrologyDiagnosticCandidate> localDiagnosticCandidates,
-            List<HydrologyColumnSample> columns
-    ) {
-        private static PersistedTile from(HydrologyTile tile, String scopeIdentity) {
-            ArrayList<PersistedCourse> courses = new ArrayList<>(tile.courses().size());
-            for (RiverCourse course : tile.courses()) {
-                courses.add(PersistedCourse.from(course));
-            }
-            ArrayList<Long> regionalCourseIds = new ArrayList<>(tile.regionalCourseIds());
-            regionalCourseIds.sort(Long::compareTo);
-            ArrayList<PersistedCavePlan> cavePlans = new ArrayList<>(tile.cavePlans().size());
-            for (HydrologyCavePlan cavePlan : tile.cavePlans()) {
-                cavePlans.add(PersistedCavePlan.from(cavePlan));
-            }
-            return new PersistedTile(
-                    SCHEMA_VERSION,
-                    scopeIdentity,
-                    tile.key(),
-                    tile.worldSeed(),
-                    tile.settingsFingerprint(),
-                    tile.tileSize(),
-                    tile.nodes(),
-                    tile.edges(),
-                    tile.outlets(),
-                    courses,
-                    regionalCourseIds,
-                    cavePlans,
-                    tile.localDiagnosticCandidates(),
-                    new ArrayList<>(tile.footprint().columns().values())
-            );
-        }
-
-        private HydrologyTile toTile() {
-            requireCollection(nodes, "nodes");
-            requireCollection(edges, "edges");
-            requireCollection(outlets, "outlets");
-            requireCollection(courses, "courses");
-            requireCollection(regionalCourseIds, "regionalCourseIds");
-            requireCollection(cavePlans, "cavePlans");
-            requireCollection(localDiagnosticCandidates, "localDiagnosticCandidates");
-            requireCollection(columns, "columns");
-            ArrayList<RiverCourse> restoredCourses = new ArrayList<>(courses.size());
-            for (PersistedCourse course : courses) {
-                restoredCourses.add(Objects.requireNonNull(course, "course").toCourse());
-            }
-            ArrayList<HydrologyCavePlan> restoredCavePlans = new ArrayList<>(cavePlans.size());
-            for (PersistedCavePlan cavePlan : cavePlans) {
-                restoredCavePlans.add(Objects.requireNonNull(cavePlan, "cavePlan").toPlan());
-            }
-            HashMap<Long, HydrologyColumnSample> restoredColumns = HashMap.newHashMap(columns.size());
-            for (HydrologyColumnSample column : columns) {
-                HydrologyColumnSample required = Objects.requireNonNull(column, "column");
-                HydrologyColumnSample existing = restoredColumns.put(
-                        RiverFootprint.pack(required.x(), required.z()), required);
-                if (existing != null) {
-                    throw new IllegalArgumentException("Duplicate hydrology footprint column.");
-                }
-            }
-            return new HydrologyTile(
-                    key,
-                    worldSeed,
-                    settingsFingerprint,
-                    tileSize,
-                    nodes,
-                    edges,
-                    outlets,
-                    restoredCourses,
-                    Set.copyOf(regionalCourseIds),
-                    restoredCavePlans,
-                    localDiagnosticCandidates,
-                    new RiverFootprint(restoredColumns)
-            );
-        }
-
-        private static void requireCollection(List<?> values, String name) {
-            Objects.requireNonNull(values, name);
-        }
-    }
-
-    private record PersistedCourse(
-            long id,
-            RiverCourseType type,
-            Long sourceNodeId,
-            Long outletId,
-            String profileKey,
-            int discharge,
-            List<DrainageEdge> drainageEdges,
-            List<HydraulicSegment> segments
-    ) {
-        private static PersistedCourse from(RiverCourse course) {
-            return new PersistedCourse(
-                    course.id(),
-                    course.type(),
-                    course.sourceNodeId().isPresent() ? course.sourceNodeId().getAsLong() : null,
-                    course.outletId().isPresent() ? course.outletId().getAsLong() : null,
-                    course.profileKey(),
-                    course.discharge(),
-                    course.drainageEdges(),
-                    course.segments()
-            );
-        }
-
-        private RiverCourse toCourse() {
-            return new RiverCourse(
-                    id,
-                    type,
-                    sourceNodeId == null ? OptionalLong.empty() : OptionalLong.of(sourceNodeId),
-                    outletId == null ? OptionalLong.empty() : OptionalLong.of(outletId),
-                    profileKey,
-                    discharge,
-                    drainageEdges,
-                    segments
-            );
-        }
-    }
-
-    private record PersistedCavePlan(
-            HydrologyCaveSource source,
-            HydrologyCaveRejection rejection,
-            List<PersistedCaveCell> cells,
-            Long arbitrationWinnerSourceId
-    ) {
-        private static PersistedCavePlan from(HydrologyCavePlan plan) {
-            ArrayList<PersistedCaveCell> cells = new ArrayList<>(plan.baselinePreconditions().size());
-            plan.forEachPrecondition((CavePosition position, CaveVoxelPrecondition precondition) -> cells.add(
-                    new PersistedCaveCell(position, plan.actions().get(position), precondition)));
-            cells.sort(Comparator.comparingInt((PersistedCaveCell cell) -> cell.position().x())
-                    .thenComparingInt(cell -> cell.position().z())
-                    .thenComparingInt(cell -> cell.position().y()));
-            return new PersistedCavePlan(
-                    plan.source(),
-                    plan.rejection(),
-                    cells,
-                    plan.arbitrationWinnerSourceId().isPresent()
-                            ? plan.arbitrationWinnerSourceId().getAsLong()
-                            : null
-            );
-        }
-
-        private HydrologyCavePlan toPlan() {
-            LinkedHashMap<CavePosition, HydrologyCaveAction> actions = new LinkedHashMap<>();
-            LinkedHashMap<CavePosition, CaveVoxelPrecondition> preconditions = new LinkedHashMap<>();
-            for (PersistedCaveCell cell : Objects.requireNonNull(cells, "cells")) {
-                PersistedCaveCell required = Objects.requireNonNull(cell, "cell");
-                CaveVoxelPrecondition existing = preconditions.put(required.position(), required.precondition());
-                if (existing != null) {
-                    throw new IllegalArgumentException("Duplicate hydrology cave cell.");
-                }
-                if (required.action() != null) {
-                    actions.put(required.position(), required.action());
-                }
-            }
-            return new HydrologyCavePlan(
-                    source,
-                    rejection,
-                    actions,
-                    preconditions,
-                    arbitrationWinnerSourceId == null
-                            ? OptionalLong.empty()
-                            : OptionalLong.of(arbitrationWinnerSourceId)
-            );
-        }
-    }
-
-    private record PersistedCaveCell(
-            CavePosition position,
-            HydrologyCaveAction action,
-            CaveVoxelPrecondition precondition
-    ) {
-        private PersistedCaveCell {
-            Objects.requireNonNull(position, "position");
-            Objects.requireNonNull(precondition, "precondition");
-        }
-    }
-
     private static final class LimitedInputStream extends FilterInputStream {
         private final long limit;
         private long count;

core/src/main/java/art/arcane/iris/generation/hydrology/cave/HydrologyCavePlan.java

@@ -5,6 +5,9 @@ import it.unimi.dsi.fastutil.HashCommon;
 import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
 import java.util.AbstractCollection;
 import java.util.AbstractList;
 import java.util.AbstractMap;
@@ -49,7 +52,11 @@ public record HydrologyCavePlan(
                 && (!requestedActions.isEmpty() || !requestedPreconditions.isEmpty())) {
             throw new IllegalArgumentException("Rejected cave plans cannot contain mutations or preconditions");
         }
-        if (!requestedPreconditions.keySet().containsAll(requestedActions.keySet())) {
+        boolean packedInput = requestedActions instanceof ActionMap actionMap
+                && requestedPreconditions instanceof PreconditionMap preconditionMap
+                && actionMap.packed == preconditionMap.packed
+                && actionMap.spatialIndex == preconditionMap.spatialIndex;
+        if (!packedInput && !requestedPreconditions.keySet().containsAll(requestedActions.keySet())) {
             throw new IllegalArgumentException("Every cave action requires a baseline precondition");
         }
         if (rejection != HydrologyCaveRejection.OVERLAPPING_SOURCE && arbitrationWinnerSourceId.isPresent()) {
@@ -58,7 +65,7 @@ public record HydrologyCavePlan(
         if (requestedPreconditions.isEmpty()) {
             actions = Map.of();
             baselinePreconditions = Map.of();
-        } else {
+        } else if (!packedInput) {
             PackedPositions packed = new PackedPositions(requestedActions, requestedPreconditions);
             PositionSpatialIndex spatialIndex = new PositionSpatialIndex(packed);
             actions = new ActionMap(packed, requestedActions.size(), spatialIndex);
@@ -66,6 +73,53 @@ public record HydrologyCavePlan(
         }
     }
 
+    public static HydrologyCavePlan readCells(HydrologyCaveSource source, HydrologyCaveRejection rejection,
+                                               OptionalLong winner, DataInput input, int count) throws IOException {
+        if (count < 0 || count > 2_000_000) {
+            throw new IOException("Invalid hydrology cave cell count: " + count);
+        }
+        int actionCount = input.readInt();
+        if (actionCount < 0 || actionCount > count) {
+            throw new IOException("Invalid hydrology cave action count: " + actionCount);
+        }
+        if (count == 0) {
+            return new HydrologyCavePlan(source, rejection, Map.of(), Map.of(), winner);
+        }
+        PackedPositions packed = new PackedPositions(input, count, actionCount);
+        int[] order = new int[count];
+        boolean[] seen = new boolean[count];
+        for (int index = 0; index < count; index++) {
+            int row = input.readInt();
+            if (row < 0 || row >= count || seen[row]) {
+                throw new IOException("Invalid hydrology cave precondition order.");
+            }
+            seen[row] = true;
+            order[index] = row;
+        }
+        PositionSpatialIndex spatialIndex = new PositionSpatialIndex(packed);
+        return new HydrologyCavePlan(source, rejection,
+                new ActionMap(packed, actionCount, spatialIndex),
+                new PreconditionMap(packed, new PositionOrder(packed, order), spatialIndex), winner);
+    }
+
+    public void writeCells(DataOutput output) throws IOException {
+        output.writeInt(baselinePreconditions.size());
+        output.writeInt(actions.size());
+        if (!(baselinePreconditions instanceof PreconditionMap preconditions)) {
+            return;
+        }
+        PackedPositions packed = preconditions.packed;
+        for (int row = 0; row < packed.size(); row++) {
+            output.writeInt(packed.x[row]);
+            output.writeInt(packed.y[row]);
+            output.writeInt(packed.z[row]);
+            output.writeByte(packed.flags[row]);
+        }
+        for (int row : preconditions.order.rows) {
+            output.writeInt(row);
+        }
+    }
+
     public boolean accepted() {
         return rejection == HydrologyCaveRejection.NONE;
     }
@@ -204,6 +258,32 @@ public record HydrologyCavePlan(
         private final int mask;
         private int count;
 
+        private PackedPositions(DataInput input, int size, int actionCount) throws IOException {
+            x = new int[size];
+            y = new int[size];
+            z = new int[size];
+            flags = new byte[size];
+            int required = (int) Math.max(2L, ((long) size * 4L + 2L) / 3L);
+            int capacity = Integer.highestOneBit(required - 1) << 1;
+            slots = new int[capacity];
+            mask = capacity - 1;
+            for (int row = 0; row < size; row++) {
+                CavePosition position = new CavePosition(input.readInt(), input.readInt(), input.readInt());
+                byte value = input.readByte();
+                int unsigned = Byte.toUnsignedInt(value);
+                if ((unsigned & 0x80) != 0 || (unsigned & VOXEL_MASK) >>> VOXEL_SHIFT >= VOXELS.length
+                        || hasAction(value) != (row < actionCount)
+                        || (hasAction(value) && (unsigned & ACTION_MASK) >= ACTIONS.length)
+                        || (!hasAction(value) && (unsigned & ACTION_MASK) != 0)) {
+                    throw new IOException("Invalid hydrology cave cell flags.");
+                }
+                if (row(position) >= 0) {
+                    throw new IOException("Duplicate hydrology cave cell.");
+                }
+                append(position, value);
+            }
+        }
+
         private PackedPositions(Map<CavePosition, HydrologyCaveAction> actions,
                                 Map<CavePosition, CaveVoxelPrecondition> preconditions) {
             int size = preconditions.size();

core/src/main/java/art/arcane/iris/generation/mantle/MatterGenerator.java

@@ -577,6 +577,9 @@ public interface MatterGenerator {
         private volatile Future<?> submission;
         private volatile Throwable failure;
         private boolean started;
+        private boolean slowWarningIssued;
+        private Thread runningThread;
+        private long startedNanos;
 
         MatterComponentTask(MatterTaskKey key) {
             this.key = key;
@@ -587,6 +590,8 @@ public interface MatterGenerator {
                 return false;
             }
             started = true;
+            runningThread = Thread.currentThread();
+            startedNanos = System.nanoTime();
             return true;
         }
 
@@ -612,6 +617,7 @@ public interface MatterGenerator {
         }
 
         synchronized void finish(Throwable cause) {
+            runningThread = null;
             if (failure == null) {
                 failure = cause;
             } else if (cause != null && cause != failure) {
@@ -644,13 +650,14 @@ public interface MatterGenerator {
                         Future<?> submitted = submission;
                         boolean dropped = submitted != null && submitted.isDone();
                         long waited = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);
-                        if (!dropped && waited < timeoutMillis) {
-                            continue;
-                        }
-                        IllegalStateException timeoutFailure = new IllegalStateException("Mantle component " + key
-                                + (dropped ? " was dropped by the dispatcher" : " did not complete in " + waited + "ms"));
-                        if (cancel(timeoutFailure)) {
-                            IrisLogging.error(timeoutFailure.getMessage());
+                        if (dropped) {
+                            IllegalStateException dispatchFailure = new IllegalStateException(
+                                    "Mantle component " + key + " was dropped by the dispatcher");
+                            if (cancel(dispatchFailure)) {
+                                IrisLogging.reportError(dispatchFailure.getMessage(), dispatchFailure);
+                            }
+                        } else if (waited >= timeoutMillis) {
+                            warnSlowComponent(waited);
                         }
                     } catch (ExecutionException executionFailure) {
                         Throwable cause = executionFailure.getCause();
@@ -663,6 +670,33 @@ public interface MatterGenerator {
                 }
             }
         }
+
+        private void warnSlowComponent(long waited) {
+            Thread worker;
+            long runningMillis;
+            synchronized (this) {
+                if (slowWarningIssued || future.isDone() || failure != null) {
+                    return;
+                }
+                slowWarningIssued = true;
+                worker = runningThread;
+                runningMillis = started ? TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startedNanos) : 0L;
+            }
+            StringBuilder diagnostic = new StringBuilder("Mantle component ")
+                    .append(key).append(" is still pending after ").append(waited)
+                    .append("ms; waiting for completion. ");
+            if (worker == null) {
+                diagnostic.append("Task is queued for the dispatcher.");
+            } else {
+                diagnostic.append("Worker=").append(worker.getName())
+                        .append(" state=").append(worker.getState())
+                        .append(" runningForMs=").append(runningMillis);
+                for (StackTraceElement frame : worker.getStackTrace()) {
+                    diagnostic.append("\n\tat ").append(frame);
+                }
+            }
+            IrisLogging.warn(diagnostic.toString());
+        }
     }
 
     record MatterPassPlan(MantlePass pass, int passChunkRadius, int downstreamBlockRadius) {

core/src/main/java/art/arcane/iris/generation/mantle/ObjectDestinationTransaction.java

@@ -424,10 +424,6 @@ final class ObjectDestinationTransaction implements ObjectPassPlacer {
         DataKey key();
 
         void apply(IObjectPlacer placer);
-
-        default int weight() {
-            return 1;
-        }
     }
 
     record SetMutation(DataKey key, Object value) implements Mutation {
@@ -462,10 +458,5 @@ final class ObjectDestinationTransaction implements ObjectPassPlacer {
         public void apply(IObjectPlacer placer) {
             placer.set(key.x(), key.y(), key.z(), state);
         }
-
-        @Override
-        public int weight() {
-            return 2;
-        }
     }
 }

core/src/main/java/art/arcane/iris/generation/mantle/ObjectSourcePlan.java

@@ -1,5 +1,10 @@
 package art.arcane.iris.generation.mantle;
 
+import art.arcane.iris.generation.decoration.tree.TreeBlockMaterial;
+import art.arcane.iris.generation.hydrology.cave.HydrologyCaveCell;
+import art.arcane.iris.integration.Identifier;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.util.matter.MatterCavern;
 import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 
@@ -7,29 +12,35 @@ import java.util.ArrayList;
 import java.util.List;
 
 final class ObjectSourcePlan {
-    private static final int DESTINATION_INDEX_WEIGHT = 8;
+    private static final int PLAN_BYTES = 256;
+    private static final int DESTINATION_INDEX_BYTES = 96;
+    private static final int MUTATION_BYTES = 96;
     private final Long2ObjectOpenHashMap<List<ObjectDestinationTransaction.Mutation>> destinations;
-    private final int mutationWeight;
+    private final int estimatedRetainedBytes;
 
     ObjectSourcePlan(List<ObjectDestinationTransaction.Mutation> mutations) {
         Long2ObjectOpenHashMap<ArrayList<ObjectDestinationTransaction.Mutation>> grouped = new Long2ObjectOpenHashMap<>(2);
-        long weight = 1L;
+        long weight = PLAN_BYTES;
         for (ObjectDestinationTransaction.Mutation mutation : mutations) {
             long key = destinationKey(mutation.x() >> 4, mutation.z() >> 4);
             ArrayList<ObjectDestinationTransaction.Mutation> local = grouped.get(key);
             if (local == null) {
                 local = new ArrayList<>();
                 grouped.put(key, local);
-                weight += DESTINATION_INDEX_WEIGHT;
+                weight += DESTINATION_INDEX_BYTES;
             }
             local.add(mutation);
-            weight += mutation.weight();
+            Object payload = switch (mutation) {
+                case ObjectDestinationTransaction.SetMutation set -> set.value();
+                case ObjectDestinationTransaction.CustomBlockMutation custom -> custom.state();
+            };
+            weight = Math.min(Integer.MAX_VALUE, weight + MUTATION_BYTES + payloadBytes(payload));
         }
         destinations = new Long2ObjectOpenHashMap<>(grouped.size());
         for (Long2ObjectMap.Entry<ArrayList<ObjectDestinationTransaction.Mutation>> entry : grouped.long2ObjectEntrySet()) {
             destinations.put(entry.getLongKey(), List.copyOf(entry.getValue()));
         }
-        this.mutationWeight = weight >= Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) weight;
+        this.estimatedRetainedBytes = weight >= Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) weight;
     }
 
     List<ObjectDestinationTransaction.Mutation> mutationsFor(int chunkX, int chunkZ) {
@@ -37,8 +48,34 @@ final class ObjectSourcePlan {
         return mutations == null ? List.of() : mutations;
     }
 
-    int mutationWeight() {
-        return mutationWeight;
+    int estimatedRetainedBytes() {
+        return estimatedRetainedBytes;
+    }
+
+    private static long payloadBytes(Object value) {
+        return switch (value) {
+            case null -> 0L;
+            case String text -> stringBytes(text);
+            case TreeBlockMaterial material -> 24L + stringBytes(material.materialKey());
+            case Identifier identifier -> 32L + stringBytes(identifier.namespace()) + stringBytes(identifier.key());
+            case NativeBlockState ignored -> 64L;
+            case MatterCavern cavern -> 32L + stringBytes(cavern.getCustomBiome());
+            case HydrologyCaveCell cell -> 64L + stringBytes(cell.fluidProfileKey()) + stringBytes(cell.floodedBiomeKey());
+            case Byte ignored -> 24L;
+            case Short ignored -> 24L;
+            case Integer ignored -> 24L;
+            case Long ignored -> 24L;
+            case Float ignored -> 24L;
+            case Double ignored -> 24L;
+            case Boolean ignored -> 24L;
+            case Character ignored -> 24L;
+            case Enum<?> ignored -> 0L;
+            default -> Integer.MAX_VALUE;
+        };
+    }
+
+    private static long stringBytes(String value) {
+        return value == null ? 0L : 48L + 2L * value.length();
     }
 
     private static long destinationKey(int chunkX, int chunkZ) {

core/src/main/java/art/arcane/iris/generation/mantle/ObjectSourcePlanCache.java

@@ -13,21 +13,25 @@ import java.util.function.Supplier;
 import static art.arcane.iris.generation.cache.Cache.key;
 
 final class ObjectSourcePlanCache {
-    static final long MAXIMUM_MUTATION_WEIGHT = 4_194_304L;
+    private static final long MAXIMUM_RETAINED_BYTES = 256L * 1024L * 1024L;
 
-    private final long maximumMutationWeight;
+    private final long maximumRetainedBytes;
     private volatile State state;
 
     ObjectSourcePlanCache() {
-        this(MAXIMUM_MUTATION_WEIGHT);
+        this(retainedByteBudget(Runtime.getRuntime().maxMemory()));
     }
 
-    ObjectSourcePlanCache(long maximumMutationWeight) {
-        if (maximumMutationWeight <= 0L) {
-            throw new IllegalArgumentException("Maximum mutation weight must be positive");
+    ObjectSourcePlanCache(long maximumRetainedBytes) {
+        if (maximumRetainedBytes <= 0L) {
+            throw new IllegalArgumentException("Maximum retained bytes must be positive");
         }
-        this.maximumMutationWeight = maximumMutationWeight;
-        state = new State(maximumMutationWeight);
+        this.maximumRetainedBytes = maximumRetainedBytes;
+        state = new State(maximumRetainedBytes);
+    }
+
+    static long retainedByteBudget(long maximumHeapBytes) {
+        return Math.max(1L, Math.min(MAXIMUM_RETAINED_BYTES, maximumHeapBytes / 64L));
     }
 
     ObjectSourcePlan get(int sourceChunkX, int sourceChunkZ, Supplier<ObjectSourcePlan> builder) {
@@ -47,7 +51,8 @@ final class ObjectSourcePlanCache {
             ObjectSourcePlan plan = current.plans.getIfPresent(source);
             if (plan == null) {
                 plan = builder.get();
-                if (plan != null) {
+                if (plan != null && plan.estimatedRetainedBytes() < Integer.MAX_VALUE
+                        && plan.estimatedRetainedBytes() <= maximumRetainedBytes) {
                     current.plans.put(source, plan);
                 }
             }
@@ -63,7 +68,7 @@ final class ObjectSourcePlanCache {
     }
 
     void clear() {
-        state = new State(maximumMutationWeight);
+        state = new State(maximumRetainedBytes);
     }
 
     long estimatedSize() {
@@ -76,10 +81,10 @@ final class ObjectSourcePlanCache {
         private final Cache<Long, ObjectSourcePlan> plans;
         private final ConcurrentHashMap<Long, Pending> pending = new ConcurrentHashMap<>();
 
-        private State(long maximumMutationWeight) {
+        private State(long maximumRetainedBytes) {
             plans = Caffeine.newBuilder()
-                    .maximumWeight(maximumMutationWeight)
-                    .weigher((Long key, ObjectSourcePlan plan) -> plan.mutationWeight())
+                    .maximumWeight(maximumRetainedBytes)
+                    .weigher((Long key, ObjectSourcePlan plan) -> plan.estimatedRetainedBytes())
                     .build();
         }
     }

core/src/main/java/art/arcane/iris/world/pregen/AsyncOrMedievalPregenMethod.java

@@ -95,6 +95,11 @@ public class AsyncOrMedievalPregenMethod implements PregeneratorMethod {
         method.onRegionSubmitted(regionX, regionZ);
     }
 
+    @Override
+    public void reclaimMemory() {
+        method.reclaimMemory();
+    }
+
     @Override
     public Mantle getMantle() {
         return method.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/AsyncPregenMethod.java

@@ -31,7 +31,6 @@ import art.arcane.iris.platform.bukkit.nms.INMSBinding;
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.hydrology.HydrologyTileCache;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
-import art.arcane.volmlib.util.collection.KSet;
 import art.arcane.volmlib.util.mantle.runtime.Mantle;
 import art.arcane.volmlib.util.math.M;
 import art.arcane.iris.generation.concurrent.MultiBurst;
@@ -97,9 +96,6 @@ public class AsyncPregenMethod implements PregeneratorMethod {
     private final ConcurrentHashMap<Long, AtomicInteger> regionPending;
     private final ConcurrentHashMap<Long, Queue<Chunk>> regionChunks;
     private final Queue<CompletableFuture<Void>> pendingEvictions;
-    private final KSet<Long> drainedRegions;
-    private final KSet<Long> evictedRegions;
-    private volatile int evictionWindowRegions;
     private volatile int boundsMinRegionX;
     private volatile int boundsMinRegionZ;
     private volatile int boundsMaxRegionX;
@@ -164,6 +160,7 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         int configuredThreads = foliaRuntime
                 ? computeFoliaRecommendedCap(workerThreadsForCap)
                 : computePaperLikeRecommendedCap(workerThreadsForCap);
+        configuredThreads = heapLimitedConcurrency(configuredThreads, Runtime.getRuntime().maxMemory());
         this.threads = selectConcurrencyCap(configuredThreads, strictSerial);
         this.workerPoolThreads = detectedWorkerPoolThreads;
         this.runtimeCpuThreads = detectedCpuThreads;
@@ -183,9 +180,6 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         this.regionPending = new ConcurrentHashMap<>();
         this.regionChunks = new ConcurrentHashMap<>();
         this.pendingEvictions = new ConcurrentLinkedQueue<>();
-        this.drainedRegions = new KSet<>();
-        this.evictedRegions = new KSet<>();
-        this.evictionWindowRegions = -1;
         this.boundsMinRegionX = Integer.MIN_VALUE;
         this.boundsMinRegionZ = Integer.MIN_VALUE;
         this.boundsMaxRegionX = Integer.MAX_VALUE;
@@ -232,28 +226,6 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         return (((long) rx) << 32) | (rz & 0xFFFFFFFFL);
     }
 
-    private int evictionWindow() {
-        int cached = evictionWindowRegions;
-        if (cached > 0) {
-            return cached;
-        }
-
-        Engine engine = resolveMetricsEngine();
-        if (engine == null) {
-            return 2;
-        }
-
-        try {
-            int radius = engine.getMantle().getRadius();
-            int resolved = radius > 0 ? Math.max(1, (int) Math.ceil(radius / 32.0)) : 2;
-            evictionWindowRegions = resolved;
-            return resolved;
-        } catch (Throwable e) {
-            PregenDiagnostics.probeFailed("mantle radius for eviction window", e);
-            return 2;
-        }
-    }
-
     private void onChunkCompleted(int x, int z, Chunk chunk) {
         if (chunk == null) {
             return;
@@ -261,10 +233,16 @@ public class AsyncPregenMethod implements PregeneratorMethod {
 
         try {
             long rk = rkey(x >> 5, z >> 5);
-            regionChunks.computeIfAbsent(rk, k -> new ConcurrentLinkedQueue<>()).add(chunk);
+            regionChunks.compute(rk, (key, existing) -> {
+                Queue<Chunk> chunks = existing == null ? new ConcurrentLinkedQueue<>() : existing;
+                chunks.add(chunk);
+                return chunks;
+            });
             AtomicInteger pending = regionPending.get(rk);
             if (pending != null && pending.decrementAndGet() == 0) {
                 onRegionDrained(rk);
+            } else if (MantleHeapPressure.overHighWater()) {
+                evictRegion(rk);
             }
         } catch (Throwable e) {
             IrisLogging.reportError(e);
@@ -317,10 +295,6 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         }
     }
 
-    private boolean inBounds(int rx, int rz) {
-        return rx >= boundsMinRegionX && rx <= boundsMaxRegionX && rz >= boundsMinRegionZ && rz <= boundsMaxRegionZ;
-    }
-
     @Override
     public void onRegionSubmitted(int regionX, int regionZ) {
         try {
@@ -335,58 +309,14 @@ public class AsyncPregenMethod implements PregeneratorMethod {
     }
 
     private void onRegionDrained(long rk) {
-        if (!drainedRegions.add(rk)) {
-            return;
-        }
-
-        int w = evictionWindow();
-        int rx = (int) (rk >> 32);
-        int rz = (int) rk;
-        for (int dx = -w; dx <= w; dx++) {
-            for (int dz = -w; dz <= w; dz++) {
-                int cx = rx + dx;
-                int cz = rz + dz;
-                long candidate = rkey(cx, cz);
-                if (evictedRegions.contains(candidate)) {
-                    continue;
-                }
-                if (!drainedRegions.contains(candidate)) {
-                    continue;
-                }
-                if (allNeighborsDrained(cx, cz, w)) {
-                    evictRegion(candidate);
-                }
-            }
-        }
-    }
-
-    private boolean allNeighborsDrained(int rx, int rz, int w) {
-        for (int dx = -w; dx <= w; dx++) {
-            for (int dz = -w; dz <= w; dz++) {
-                int nx = rx + dx;
-                int nz = rz + dz;
-                if (!inBounds(nx, nz)) {
-                    continue;
-                }
-
-                if (!drainedRegions.contains(rkey(nx, nz))) {
-                    return false;
-                }
-            }
-        }
-
-        return true;
+        regionPending.remove(rk);
+        evictRegion(rk);
     }
 
     private CompletableFuture<Void> evictRegion(long c) {
         if (IrisToolbelt.isServerStopping()) {
             return CompletableFuture.completedFuture(null);
         }
-        if (!evictedRegions.add(c)) {
-            return CompletableFuture.completedFuture(null);
-        }
-
-        regionPending.remove(c);
         Queue<Chunk> chunks = regionChunks.remove(c);
         if (chunks == null || chunks.isEmpty()) {
             return CompletableFuture.completedFuture(null);
@@ -651,6 +581,11 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         return strictSerial ? 1 : Math.max(1, recommendedCap);
     }
 
+    static int heapLimitedConcurrency(int recommendedCap, long maximumHeapBytes) {
+        long heapCap = Math.max(1L, maximumHeapBytes / (256L * 1024L * 1024L));
+        return (int) Math.min(Math.max(1, recommendedCap), heapCap);
+    }
+
     static int computeInitialInFlightLimit(int concurrencyCap, int workerThreads) {
         long initial = Math.max(1L, workerThreads) * 8L;
         return (int) Math.min(Math.max(1, concurrencyCap), initial);
@@ -880,6 +815,14 @@ public class AsyncPregenMethod implements PregeneratorMethod {
     public void save() {
     }
 
+    @Override
+    public void reclaimMemory() {
+        if (regionChunks.isEmpty() && pendingEvictions.isEmpty()) {
+            return;
+        }
+        flushAllRemainingChunks();
+    }
+
     @Override
     public boolean supportsRegions(int x, int z, PregenListener listener) {
         return false;
@@ -893,8 +836,11 @@ public class AsyncPregenMethod implements PregeneratorMethod {
     @Override
     public void generateChunk(int x, int z, PregenListener listener) {
         listener.onChunkGenerating(x, z);
+        if (MantleHeapPressure.overHighWater()) {
+            reclaimMemory();
+        }
         backpressure.enforceMantleBudget();
-        backpressure.awaitHeapHeadroom();
+        backpressure.awaitHeapHeadroom(MantleHeapPressure::overHighWater, this::reclaimHeapPressure);
         if (isCancelled()) {
             return;
         }
@@ -924,6 +870,13 @@ public class AsyncPregenMethod implements PregeneratorMethod {
         executor.generate(x, z, listener);
     }
 
+    private void reclaimHeapPressure() {
+        if (!regionChunks.isEmpty() || !pendingEvictions.isEmpty()) {
+            reclaimMemory();
+        }
+        MantleHeapPressure.requestPanicReclaim();
+    }
+
     private CompletableFuture<Chunk> requestChunkAsync(int x, int z) {
         Throwable failure = null;
 

core/src/main/java/art/arcane/iris/world/pregen/CachedPregenMethod.java

@@ -203,6 +203,11 @@ public class CachedPregenMethod implements PregeneratorMethod {
                                 PregenSavedChunkStatus savedStatus) {
     }
 
+    @Override
+    public void reclaimMemory() {
+        method.reclaimMemory();
+    }
+
     @Override
     public Mantle getMantle() {
         return method.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/HybridPregenMethod.java

@@ -88,6 +88,11 @@ public class HybridPregenMethod implements PregeneratorMethod {
         inWorld.onRegionSubmitted(regionX, regionZ);
     }
 
+    @Override
+    public void reclaimMemory() {
+        inWorld.reclaimMemory();
+    }
+
     @Override
     public Mantle getMantle() {
         return inWorld.getMantle();

core/src/main/java/art/arcane/iris/world/pregen/IrisPregenerator.java

@@ -438,6 +438,12 @@ public class IrisPregenerator {
             return;
         }
 
+        try {
+            generator.reclaimMemory();
+        } catch (Throwable e) {
+            IrisLogging.reportError("Pregen could not reclaim completed server chunks under heap pressure.", e);
+        }
+
         try {
             Mantle mantle = getMantle();
             if (mantle != null) {

core/src/main/java/art/arcane/iris/world/pregen/PregenMantleBackpressure.java

@@ -29,6 +29,8 @@ import java.util.function.BooleanSupplier;
 import java.util.function.Supplier;
 
 public final class PregenMantleBackpressure {
+    private static final long LOG_INTERVAL_MS = 5_000L;
+
     private final Supplier<Mantle> mantleSupplier;
     private final int maxResidentTectonicPlates;
     private final int waitMs;
@@ -46,7 +48,7 @@ public final class PregenMantleBackpressure {
     public PregenMantleBackpressure(Supplier<Mantle> mantleSupplier, int maxResidentTectonicPlates, int waitMs, long timeoutMs, Runnable onBudgetTimeout, Supplier<String> diagnostics, BooleanSupplier cancelled) {
         this.mantleSupplier = mantleSupplier;
         this.maxResidentTectonicPlates = maxResidentTectonicPlates;
-        this.waitMs = waitMs;
+        this.waitMs = Math.max(1, waitMs);
         this.timeoutMs = timeoutMs;
         this.onBudgetTimeout = onBudgetTimeout;
         this.diagnostics = diagnostics;
@@ -69,14 +71,13 @@ public final class PregenMantleBackpressure {
             return;
         }
 
-        int hardCap = cap * 2;
-        if (mantle.getLoadedRegionCount() <= hardCap) {
+        if (mantle.getLoadedRegionCount() <= cap) {
             return;
         }
 
         long waitStart = M.ms();
         long lastLog = 0L;
-        while (mantle.getLoadedRegionCount() > hardCap) {
+        while (mantle.getLoadedRegionCount() > cap) {
             if (isCancelled()) {
                 return;
             }
@@ -87,29 +88,34 @@ public final class PregenMantleBackpressure {
                 mantle.trim(0L);
                 freed = mantle.unloadTectonicPlate(0);
                 resident = mantle.getLoadedRegionCount();
+                if (resident > cap && mantle.saveOldestIdleTectonicPlate()) {
+                    freed++;
+                    resident = mantle.getLoadedRegionCount();
+                }
             } catch (Throwable e) {
                 IrisLogging.reportError(e);
                 break;
             }
-            if (resident <= hardCap) {
+            if (resident <= cap) {
                 break;
             }
 
             long elapsed = M.ms() - waitStart;
-            if (elapsed >= timeoutMs) {
+            if (elapsed >= timeoutMs && freed == 0) {
                 IrisLogging.warn("Pregen mantle backpressure exceeded " + timeoutMs + "ms with " + resident
-                        + " tectonic plates resident (hard cap " + hardCap + "); proceeding to avoid deadlock. "
-                        + "Raise pregen.maxResidentTectonicPlates if this persists. " + diagnostics.get());
+                        + " tectonic plates resident (residency target " + cap + "); no idle plate could be evicted. "
+                        + "Allowing the active dependency working set to exceed the residency target; "
+                        + "heap pressure still blocks new chunk submissions. " + diagnostics.get());
                 onBudgetTimeout.run();
                 return;
             }
 
             long logNow = M.ms();
-            if (logNow - lastLog >= 5_000L) {
+            if (logNow - lastLog >= LOG_INTERVAL_MS) {
                 lastLog = logNow;
                 // Pausing to stay under the plate cap is the design working, and it is reported every five
                 // seconds for the whole duration of a large pregen. Only exceeding the budget is a warning.
-                IrisLogging.info("Pregen mantle backpressure: " + resident + " tectonic plates resident (hard cap " + hardCap
+                IrisLogging.info("Pregen mantle backpressure: " + resident + " tectonic plates resident (residency target " + cap
                         + "), freed " + freed + " last pass, waited " + elapsed + "ms.");
             }
 
@@ -127,6 +133,9 @@ public final class PregenMantleBackpressure {
         Mantle mantle = resolveMantle();
         long waitStart = M.ms();
         long lastLog = 0L;
+        long nextWarningElapsed = Math.max(0L, timeoutMs);
+        long nextEvictionErrorLog = 0L;
+        long warningInterval = Math.max(LOG_INTERVAL_MS, timeoutMs);
         while (heapPressure.getAsBoolean()) {
             if (isCancelled()) {
                 return;
@@ -137,22 +146,30 @@ public final class PregenMantleBackpressure {
                     mantle.saveOldestIdleTectonicPlate();
                 }
             } catch (Throwable e) {
-                IrisLogging.reportError(e);
+                long now = M.ms();
+                if (now >= nextEvictionErrorLog) {
+                    nextEvictionErrorLog = now + warningInterval;
+                    IrisLogging.reportError(e);
+                }
             }
 
             panicReclaim.run();
-
-            long elapsed = M.ms() - waitStart;
-            if (elapsed >= timeoutMs) {
-                IrisLogging.warn("Pregen heap pressure wait exceeded " + timeoutMs + "ms at "
-                        + Math.round(MantleHeapPressure.usedFraction() * 100.0D) + "% heap; proceeding to avoid deadlock. "
-                        + diagnostics.get());
-                onBudgetTimeout.run();
+            if (isCancelled() || !heapPressure.getAsBoolean()) {
                 return;
             }
 
+            long elapsed = M.ms() - waitStart;
             long logNow = M.ms();
-            if (logNow - lastLog >= 5_000L) {
+            if (elapsed >= nextWarningElapsed) {
+                nextWarningElapsed = elapsed + warningInterval;
+                lastLog = logNow;
+                IrisLogging.warn("Pregen heap pressure is still blocking new chunk submissions after " + elapsed + "ms at "
+                        + Math.round(MantleHeapPressure.usedFraction() * 100.0D) + "% heap; waiting for headroom. "
+                        + diagnostics.get());
+                onBudgetTimeout.run();
+            }
+
+            if (logNow - lastLog >= LOG_INTERVAL_MS) {
                 lastLog = logNow;
                 IrisLogging.info("Pregen heap pressure: pausing generation at "
                         + Math.round(MantleHeapPressure.usedFraction() * 100.0D) + "% heap; evicting tectonic plates and waiting for headroom"

core/src/main/java/art/arcane/iris/world/pregen/PregeneratorMethod.java

@@ -89,5 +89,8 @@ public interface PregeneratorMethod {
     default void onRegionSubmitted(int regionX, int regionZ) {
     }
 
+    default void reclaimMemory() {
+    }
+
     Mantle getMantle();
 }