Added modded worldgen catalog

- Captured the worldgen catalog after server start, scanning registries on the server thread and encoding and writing on a worker into config/irisworldgen/catalog/worldgen-catalog.json
- Added WorldgenCatalogFingerprint over namespace versions and registry keys
- Added /iris catalog [namespace|refresh] and /iris ingest mods <source> <target> with keyed dimension, namespaces and replace options
- Added catalog messages and help entries for every shipped locale
- Added tests for catalog assembly, namespace summaries, ingest arguments, the registry scan and command registration

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

@@ -58,6 +58,7 @@ import art.arcane.iris.generation.block.BlockDataMergeSupport;
 import art.arcane.iris.structure.object.IrisObjectRotation;
 import art.arcane.iris.generation.block.TileData;
 import art.arcane.iris.modded.api.ModdedCustomContentRegistry;
+import art.arcane.iris.modded.catalog.ModdedWorldgenCatalogs;
 import art.arcane.iris.modded.command.IrisModdedCommands;
 import art.arcane.iris.modded.command.ModdedGuiHost;
 import art.arcane.iris.modded.command.ModdedObjectUndo;
@@ -173,6 +174,7 @@ public final class ModdedEngineBootstrap {
         ModdedStartup.runOnce(server);
         reconcileSpawn(server);
         ModdedWorldCheck.serverStarted(server);
+        ModdedWorldgenCatalogs.capture(server);
     }
 
     public static void levelLoaded(NativeWorld world) {

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

@@ -0,0 +1,32 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModMetadata;
+
+import java.util.List;
+import java.util.Objects;
+
+public record CatalogCaptureContext(String minecraftVersion, String platform, long capturedAtEpochMillis, List<NativeModMetadata> mods) {
+    public CatalogCaptureContext {
+        Objects.requireNonNull(minecraftVersion, "minecraftVersion");
+        Objects.requireNonNull(platform, "platform");
+        mods = List.copyOf(Objects.requireNonNull(mods, "mods"));
+    }
+}

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

@@ -0,0 +1,139 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.iris.modded.ModdedEngineBootstrap;
+import art.arcane.iris.modded.ModdedIrisLog;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalogStore;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedLoader;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenScan;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.EncodeFailures;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Path;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+public final class ModdedWorldgenCatalogs {
+    private static final AtomicReference<WorldgenCatalog> LATEST = new AtomicReference<>();
+    private static final AtomicReference<CompletableFuture<CaptureResult>> RUNNING = new AtomicReference<>();
+
+    private ModdedWorldgenCatalogs() {
+    }
+
+    public static Optional<WorldgenCatalog> latest() {
+        return Optional.ofNullable(LATEST.get());
+    }
+
+    public static Path catalogFile() {
+        return ModdedEngineBootstrap.loader().configDir().resolve("irisworldgen").resolve("catalog")
+                .resolve(WorldgenCatalogStore.FILE_NAME);
+    }
+
+    public static CompletableFuture<CaptureResult> capture(NativeModdedServer server) {
+        Objects.requireNonNull(server, "server");
+        CompletableFuture<CaptureResult> pending = new CompletableFuture<>();
+        CompletableFuture<CaptureResult> running = RUNNING.compareAndExchange(null, pending);
+        if (running != null) {
+            return running;
+        }
+        long startedAt = System.nanoTime();
+        NativeModdedLoader loader = ModdedEngineBootstrap.loader();
+        NativeWorldgenScan scan;
+        CatalogCaptureContext context;
+        try {
+            scan = NativeWorldgenScan.scan(server, loader);
+            context = new CatalogCaptureContext(loader.minecraftVersion(), loader.platformName(),
+                    System.currentTimeMillis(), loader.mods());
+        } catch (RuntimeException failure) {
+            ModdedIrisLog.error("Iris could not read the worldgen registries for the catalog", failure);
+            finish(pending, null, failure);
+            return pending;
+        }
+        long scanMillis = elapsedMillis(startedAt);
+        Path file = catalogFile();
+        Thread worker = new Thread(() -> encodeAndWrite(new PendingCapture(scan, context, file, startedAt, scanMillis), pending),
+                "Iris Worldgen Catalog");
+        worker.setDaemon(true);
+        worker.start();
+        return pending;
+    }
+
+    private static void encodeAndWrite(PendingCapture capture, CompletableFuture<CaptureResult> pending) {
+        try {
+            NativeWorldgenSnapshot snapshot = capture.scan().encode();
+            WorldgenCatalog catalog = WorldgenCatalogAssembler.assemble(snapshot, capture.context());
+            WorldgenCatalogStore.write(capture.file(), catalog);
+            LATEST.set(catalog);
+            CaptureResult result = new CaptureResult(catalog, capture.file(), elapsedMillis(capture.startedAt()));
+            ModdedIrisLog.info("Iris worldgen catalog: {} namespaces, {} biomes, {} placed features, {} structures, "
+                            + "{} dimension types, {} level stems -> {} ({}ms server thread, {}ms total)",
+                    catalog.namespaces().size(), catalog.biomes().size(), catalog.placedFeatures().size(),
+                    catalog.structures().size(), catalog.dimensionTypes().size(), catalog.levelStems().size(),
+                    capture.file(), capture.scanMillis(), result.millis());
+            reportEncodeFailures(snapshot.failures());
+            finish(pending, result, null);
+        } catch (IOException failure) {
+            ModdedIrisLog.error("Iris could not write the worldgen catalog to " + capture.file(), failure);
+            finish(pending, null, new UncheckedIOException(failure));
+        } catch (RuntimeException failure) {
+            ModdedIrisLog.error("Iris could not build the worldgen catalog", failure);
+            finish(pending, null, failure);
+        }
+    }
+
+    private static void reportEncodeFailures(EncodeFailures failures) {
+        if (failures.count() == 0) {
+            return;
+        }
+        String first = failures.samples().isEmpty() ? "" : failures.samples().getFirst();
+        if (failures.firstException() != null) {
+            ModdedIrisLog.warn("Iris worldgen catalog left {} entries without JSON; first: {}", failures.count(), first,
+                    failures.firstException());
+            return;
+        }
+        ModdedIrisLog.warn("Iris worldgen catalog left {} entries without JSON; first: {}", failures.count(), first);
+    }
+
+    private static void finish(CompletableFuture<CaptureResult> pending, CaptureResult result, RuntimeException failure) {
+        RUNNING.compareAndSet(pending, null);
+        if (failure != null) {
+            pending.completeExceptionally(failure);
+            return;
+        }
+        pending.complete(result);
+    }
+
+    private static long elapsedMillis(long startedAt) {
+        return TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startedAt);
+    }
+
+    public record CaptureResult(WorldgenCatalog catalog, Path file, long millis) {
+    }
+
+    private record PendingCapture(NativeWorldgenScan scan, CatalogCaptureContext context, Path file, long startedAt, long scanMillis) {
+    }
+}

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

@@ -0,0 +1,146 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.iris.pack.ingest.catalog.CatalogBiome;
+import art.arcane.iris.pack.ingest.catalog.CatalogDimensionType;
+import art.arcane.iris.pack.ingest.catalog.CatalogLevelStem;
+import art.arcane.iris.pack.ingest.catalog.CatalogNamespace;
+import art.arcane.iris.pack.ingest.catalog.CatalogPlacedFeature;
+import art.arcane.iris.pack.ingest.catalog.CatalogSpawn;
+import art.arcane.iris.pack.ingest.catalog.CatalogStructure;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalogFingerprint;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalogIndex;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModMetadata;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenBiome;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenDimensionType;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenLevelStem;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenPlacedFeature;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenSpawn;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenStructure;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+
+public final class WorldgenCatalogAssembler {
+    private static final String MINECRAFT = "minecraft";
+
+    private WorldgenCatalogAssembler() {
+    }
+
+    public static WorldgenCatalog assemble(NativeWorldgenSnapshot snapshot, CatalogCaptureContext context) {
+        Objects.requireNonNull(snapshot, "snapshot");
+        Objects.requireNonNull(context, "context");
+        List<CatalogBiome> biomes = biomes(snapshot.biomes());
+        List<CatalogPlacedFeature> placedFeatures = placedFeatures(snapshot.placedFeatures());
+        List<CatalogStructure> structures = structures(snapshot.structures());
+        List<CatalogDimensionType> dimensionTypes = dimensionTypes(snapshot.dimensionTypes());
+        List<CatalogLevelStem> levelStems = levelStems(snapshot.levelStems());
+        Map<String, List<String>> registryKeys = new LinkedHashMap<>();
+        registryKeys.put("biome", biomes.stream().map(CatalogBiome::key).toList());
+        registryKeys.put("placed_feature", placedFeatures.stream().map(CatalogPlacedFeature::key).toList());
+        registryKeys.put("structure", structures.stream().map(CatalogStructure::key).toList());
+        registryKeys.put("dimension_type", dimensionTypes.stream().map(CatalogDimensionType::key).toList());
+        registryKeys.put("level_stem", levelStems.stream().map(CatalogLevelStem::key).toList());
+        List<CatalogNamespace> namespaces = namespaces(registryKeys, context);
+        return new WorldgenCatalog(WorldgenCatalog.FORMAT, context.minecraftVersion(), context.platform(),
+                context.capturedAtEpochMillis(), WorldgenCatalogFingerprint.of(namespaces, registryKeys), namespaces,
+                biomes, placedFeatures, structures, dimensionTypes, levelStems);
+    }
+
+    private static List<CatalogNamespace> namespaces(Map<String, List<String>> registryKeys, CatalogCaptureContext context) {
+        Map<String, CatalogNamespace> namespaces = new TreeMap<>();
+        for (NativeModMetadata mod : context.mods()) {
+            namespaces.put(mod.id(), new CatalogNamespace(mod.id(), mod.displayName(), mod.version()));
+        }
+        for (List<String> keys : registryKeys.values()) {
+            for (String key : keys) {
+                String namespace = WorldgenCatalogIndex.namespaceOf(key);
+                if (!namespaces.containsKey(namespace)) {
+                    namespaces.put(namespace, fallbackNamespace(namespace, context));
+                }
+            }
+        }
+        if (!namespaces.containsKey(MINECRAFT)) {
+            namespaces.put(MINECRAFT, fallbackNamespace(MINECRAFT, context));
+        }
+        return List.copyOf(namespaces.values());
+    }
+
+    private static CatalogNamespace fallbackNamespace(String namespace, CatalogCaptureContext context) {
+        if (MINECRAFT.equals(namespace)) {
+            return new CatalogNamespace(MINECRAFT, "Minecraft", context.minecraftVersion());
+        }
+        return new CatalogNamespace(namespace, namespace, "");
+    }
+
+    private static List<CatalogBiome> biomes(List<WorldgenBiome> biomes) {
+        List<CatalogBiome> result = new ArrayList<>(biomes.size());
+        for (WorldgenBiome biome : biomes) {
+            List<CatalogSpawn> spawns = new ArrayList<>(biome.spawns().size());
+            for (WorldgenSpawn spawn : biome.spawns()) {
+                spawns.add(new CatalogSpawn(spawn.category(), spawn.entity(), spawn.weight(), spawn.minCount(), spawn.maxCount()));
+            }
+            result.add(new CatalogBiome(biome.key(), biome.temperature(), biome.downfall(), biome.hasPrecipitation(),
+                    biome.tags(), biome.featureSteps(), spawns, biome.definition()));
+        }
+        return result;
+    }
+
+    private static List<CatalogPlacedFeature> placedFeatures(List<WorldgenPlacedFeature> features) {
+        List<CatalogPlacedFeature> result = new ArrayList<>(features.size());
+        for (WorldgenPlacedFeature feature : features) {
+            result.add(new CatalogPlacedFeature(feature.key(), feature.feature(), feature.featureType(),
+                    feature.config(), feature.placement()));
+        }
+        return result;
+    }
+
+    private static List<CatalogStructure> structures(List<WorldgenStructure> structures) {
+        List<CatalogStructure> result = new ArrayList<>(structures.size());
+        for (WorldgenStructure structure : structures) {
+            result.add(new CatalogStructure(structure.key(), structure.type(), structure.step(),
+                    structure.terrainAdaptation(), structure.biomeTag(), structure.biomes(), structure.structureSets()));
+        }
+        return result;
+    }
+
+    private static List<CatalogDimensionType> dimensionTypes(List<WorldgenDimensionType> types) {
+        List<CatalogDimensionType> result = new ArrayList<>(types.size());
+        for (WorldgenDimensionType type : types) {
+            result.add(new CatalogDimensionType(type.key(), type.minY(), type.height(), type.logicalHeight(), type.definition()));
+        }
+        return result;
+    }
+
+    private static List<CatalogLevelStem> levelStems(List<WorldgenLevelStem> stems) {
+        List<CatalogLevelStem> result = new ArrayList<>(stems.size());
+        for (WorldgenLevelStem stem : stems) {
+            result.add(new CatalogLevelStem(stem.key(), stem.dimensionType(), stem.generatorType(),
+                    stem.biomeSourceType(), stem.generator()));
+        }
+        return result;
+    }
+}

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

@@ -0,0 +1,173 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.iris.pack.ingest.catalog.CatalogBiome;
+import art.arcane.iris.pack.ingest.catalog.CatalogDimensionType;
+import art.arcane.iris.pack.ingest.catalog.CatalogLevelStem;
+import art.arcane.iris.pack.ingest.catalog.CatalogNamespace;
+import art.arcane.iris.pack.ingest.catalog.CatalogPlacedFeature;
+import art.arcane.iris.pack.ingest.catalog.CatalogStructure;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalogIndex;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.TreeMap;
+import java.util.function.Function;
+
+public final class WorldgenCatalogSummary {
+    private static final String VANILLA_PREFIX = "minecraft:";
+
+    private WorldgenCatalogSummary() {
+    }
+
+    public static List<NamespaceSummary> namespaces(WorldgenCatalog catalog) {
+        Map<String, Builder> builders = new TreeMap<>();
+        for (CatalogNamespace namespace : catalog.namespaces()) {
+            builders.put(namespace.namespace(), new Builder(namespace));
+        }
+        collect(builders, catalog.biomes(), CatalogBiome::key, Builder::biomes);
+        collect(builders, catalog.placedFeatures(), CatalogPlacedFeature::key, Builder::placedFeatures);
+        collect(builders, catalog.structures(), CatalogStructure::key, Builder::structures);
+        collect(builders, catalog.dimensionTypes(), CatalogDimensionType::key, Builder::dimensionTypes);
+        collect(builders, catalog.levelStems(), CatalogLevelStem::key, Builder::levelStems);
+        for (CatalogPlacedFeature feature : catalog.placedFeatures()) {
+            builder(builders, WorldgenCatalogIndex.namespaceOf(feature.key())).featureTypes()
+                    .merge(feature.featureType(), 1, Integer::sum);
+        }
+        List<NamespaceSummary> summaries = new ArrayList<>(builders.size());
+        for (Builder builder : builders.values()) {
+            summaries.add(builder.build());
+        }
+        return summaries;
+    }
+
+    public static Optional<NamespaceSummary> namespace(WorldgenCatalog catalog, String namespace) {
+        for (NamespaceSummary summary : namespaces(catalog)) {
+            if (summary.namespace().namespace().equals(namespace)) {
+                return Optional.of(summary);
+            }
+        }
+        return Optional.empty();
+    }
+
+    public static String featureTypes(List<TypeCount> types, int limit) {
+        List<String> labels = new ArrayList<>(Math.min(types.size(), limit));
+        for (int index = 0; index < types.size() && index < limit; index++) {
+            TypeCount type = types.get(index);
+            labels.add(shortType(type.type()) + " " + type.count());
+        }
+        return withRemainder(String.join(", ", labels), types.size() - labels.size());
+    }
+
+    public static String limited(List<String> keys, String namespace, int limit) {
+        List<String> labels = new ArrayList<>(Math.min(keys.size(), limit));
+        String ownPrefix = namespace + ":";
+        for (int index = 0; index < keys.size() && index < limit; index++) {
+            String key = keys.get(index);
+            labels.add(key.startsWith(ownPrefix) ? key.substring(ownPrefix.length()) : key);
+        }
+        return withRemainder(String.join(", ", labels), keys.size() - labels.size());
+    }
+
+    private static String shortType(String type) {
+        return type.startsWith(VANILLA_PREFIX) ? type.substring(VANILLA_PREFIX.length()) : type;
+    }
+
+    private static String withRemainder(String joined, int remainder) {
+        return remainder > 0 ? joined + " (+" + remainder + " more)" : joined;
+    }
+
+    private static <T> void collect(Map<String, Builder> builders, List<T> entries, Function<T, String> key,
+                                    Function<Builder, List<String>> target) {
+        for (T entry : entries) {
+            String entryKey = key.apply(entry);
+            target.apply(builder(builders, WorldgenCatalogIndex.namespaceOf(entryKey))).add(entryKey);
+        }
+    }
+
+    private static Builder builder(Map<String, Builder> builders, String namespace) {
+        return builders.computeIfAbsent(namespace, (String missing) -> new Builder(new CatalogNamespace(missing, missing, "")));
+    }
+
+    public record TypeCount(String type, int count) {
+        public TypeCount {
+            Objects.requireNonNull(type, "type");
+        }
+    }
+
+    public record NamespaceSummary(
+            CatalogNamespace namespace,
+            List<String> biomes,
+            List<String> placedFeatures,
+            List<TypeCount> featureTypes,
+            List<String> structures,
+            List<String> dimensionTypes,
+            List<String> levelStems) {
+        public NamespaceSummary {
+            Objects.requireNonNull(namespace, "namespace");
+            biomes = List.copyOf(biomes);
+            placedFeatures = List.copyOf(placedFeatures);
+            featureTypes = List.copyOf(featureTypes);
+            structures = List.copyOf(structures);
+            dimensionTypes = List.copyOf(dimensionTypes);
+            levelStems = List.copyOf(levelStems);
+        }
+
+        public boolean hasContent() {
+            return !biomes.isEmpty() || !placedFeatures.isEmpty() || !structures.isEmpty()
+                    || !dimensionTypes.isEmpty() || !levelStems.isEmpty();
+        }
+    }
+
+    private record Builder(
+            CatalogNamespace namespace,
+            List<String> biomes,
+            List<String> placedFeatures,
+            Map<String, Integer> featureTypes,
+            List<String> structures,
+            List<String> dimensionTypes,
+            List<String> levelStems) {
+        private Builder(CatalogNamespace namespace) {
+            this(namespace, new ArrayList<>(), new ArrayList<>(), new TreeMap<>(), new ArrayList<>(), new ArrayList<>(),
+                    new ArrayList<>());
+        }
+
+        private NamespaceSummary build() {
+            List<TypeCount> types = new ArrayList<>(featureTypes.size());
+            for (Map.Entry<String, Integer> entry : featureTypes.entrySet()) {
+                types.add(new TypeCount(entry.getKey(), entry.getValue()));
+            }
+            types.sort(Comparator.comparingInt(TypeCount::count).reversed().thenComparing(TypeCount::type));
+            return new NamespaceSummary(namespace, sorted(biomes), sorted(placedFeatures), types, sorted(structures),
+                    sorted(dimensionTypes), sorted(levelStems));
+        }
+
+        private static List<String> sorted(List<String> keys) {
+            List<String> copy = new ArrayList<>(keys);
+            copy.sort(null);
+            return copy;
+        }
+    }
+}

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

@@ -0,0 +1,125 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.command;
+
+import java.util.HashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.regex.Pattern;
+
+record ModIngestArguments(String sourcePack, String targetPack, String dimension, Set<String> namespaces, boolean replace) {
+    static final List<String> OPTION_SUGGESTIONS = List.of("dimension=", "namespaces=", "replace=true");
+    private static final Pattern PACK = Pattern.compile("[A-Za-z0-9_.-]+");
+    private static final Pattern DIMENSION = Pattern.compile("[A-Za-z0-9_/.-]+");
+    private static final Pattern NAMESPACE = Pattern.compile("[a-z0-9_.-]+");
+    private static final String DIMENSION_KEY = "dimension";
+    private static final String NAMESPACES_KEY = "namespaces";
+    private static final String REPLACE_KEY = "replace";
+
+    ModIngestArguments {
+        Objects.requireNonNull(sourcePack, "sourcePack");
+        Objects.requireNonNull(targetPack, "targetPack");
+        Objects.requireNonNull(dimension, "dimension");
+        namespaces = Set.copyOf(Objects.requireNonNull(namespaces, "namespaces"));
+    }
+
+    static ModIngestArguments parse(String raw) {
+        String trimmed = raw == null ? "" : raw.trim();
+        String[] tokens = trimmed.isEmpty() ? new String[0] : trimmed.split("\\s+");
+        String source = null;
+        String target = null;
+        Map<String, String> options = new HashMap<>(4);
+        for (String token : tokens) {
+            int equals = token.indexOf('=');
+            if (equals < 0) {
+                if (source == null) {
+                    source = token;
+                } else if (target == null) {
+                    target = token;
+                } else {
+                    throw new IllegalArgumentException("unexpected argument '" + token + "'");
+                }
+                continue;
+            }
+            String key = token.substring(0, equals);
+            if (!key.equals(DIMENSION_KEY) && !key.equals(NAMESPACES_KEY) && !key.equals(REPLACE_KEY)) {
+                throw new IllegalArgumentException("unknown option '" + key + "'");
+            }
+            if (options.putIfAbsent(key, token.substring(equals + 1)) != null) {
+                throw new IllegalArgumentException("option '" + key + "' given twice");
+            }
+        }
+        if (source == null) {
+            throw new IllegalArgumentException("missing source pack");
+        }
+        if (target == null) {
+            throw new IllegalArgumentException("missing target pack");
+        }
+        requirePack(source);
+        requirePack(target);
+        if (source.equals(target)) {
+            throw new IllegalArgumentException("source and target must be different packs");
+        }
+        String dimension = options.getOrDefault(DIMENSION_KEY, source);
+        if (!DIMENSION.matcher(dimension).matches() || dimension.contains("..")) {
+            throw new IllegalArgumentException("invalid dimension key '" + dimension + "'");
+        }
+        return new ModIngestArguments(source, target, dimension, namespaces(options.get(NAMESPACES_KEY)),
+                replace(options.get(REPLACE_KEY)));
+    }
+
+    private static void requirePack(String pack) {
+        if (!PACK.matcher(pack).matches() || pack.contains("..")) {
+            throw new IllegalArgumentException("invalid pack name '" + pack + "'");
+        }
+    }
+
+    private static Set<String> namespaces(String raw) {
+        if (raw == null) {
+            return Set.of();
+        }
+        Set<String> namespaces = new LinkedHashSet<>();
+        for (String part : raw.split(",")) {
+            if (part.isEmpty()) {
+                continue;
+            }
+            if (!NAMESPACE.matcher(part).matches()) {
+                throw new IllegalArgumentException("invalid namespace '" + part + "'");
+            }
+            namespaces.add(part);
+        }
+        if (namespaces.isEmpty()) {
+            throw new IllegalArgumentException("namespaces must not be empty");
+        }
+        return namespaces;
+    }
+
+    private static boolean replace(String raw) {
+        if (raw == null || raw.equals("false")) {
+            return false;
+        }
+        if (raw.equals("true")) {
+            return true;
+        }
+        throw new IllegalArgumentException("replace must be true or false");
+    }
+}

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

@@ -0,0 +1,309 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.command;
+
+import art.arcane.iris.localization.IrisLanguage;
+import art.arcane.iris.modded.ModdedIrisLog;
+import art.arcane.iris.modded.catalog.ModdedWorldgenCatalogs;
+import art.arcane.iris.modded.catalog.ModdedWorldgenCatalogs.CaptureResult;
+import art.arcane.iris.modded.catalog.WorldgenCatalogSummary;
+import art.arcane.iris.modded.catalog.WorldgenCatalogSummary.NamespaceSummary;
+import art.arcane.iris.modded.localization.ModdedCatalogMessages;
+import art.arcane.iris.pack.PackDirectoryResolver;
+import art.arcane.iris.pack.ingest.ModIngestReport;
+import art.arcane.iris.pack.ingest.ModIngestRequest;
+import art.arcane.iris.pack.ingest.ModIngester;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandRegistration;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandSource;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.util.localization.MessageArgument;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.suggestion.SuggestionProvider;
+import com.mojang.brigadier.suggestion.Suggestions;
+import com.mojang.brigadier.suggestion.SuggestionsBuilder;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Predicate;
+
+final class ModdedCatalogCommands {
+    private static final Predicate<NativeCommandSource> GATE = NativeCommandRegistration.GAMEMASTERS;
+    private static final int LIST_FEATURE_TYPES = 3;
+    private static final int DETAIL_LIMIT = 24;
+    private static final String NONE = "-";
+    private static final AtomicReference<NamespaceCache> NAMESPACE_CACHE = new AtomicReference<>();
+    private static final SuggestionProvider<NativeCommandSource> NAMESPACES = (CommandContext<NativeCommandSource> context,
+                                                                             SuggestionsBuilder builder) ->
+            NativeCommandRegistration.suggest(contentNamespaces(), builder);
+    private static final SuggestionProvider<NativeCommandSource> INGEST_ARGUMENTS = ModdedCatalogCommands::suggestIngestArguments;
+
+    private ModdedCatalogCommands() {
+    }
+
+    static LiteralArgumentBuilder<NativeCommandSource> catalogTree() {
+        return NativeCommandRegistration.literal("catalog").requires(GATE)
+                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> list(context.getSource())))
+                .then(NativeCommandRegistration.literal("refresh")
+                        .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> refresh(context.getSource()))))
+                .then(NativeCommandRegistration.argument("namespace", StringArgumentType.word()).suggests(NAMESPACES)
+                        .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) ->
+                                detail(context.getSource(), StringArgumentType.getString(context, "namespace")))));
+    }
+
+    static LiteralArgumentBuilder<NativeCommandSource> ingestTree() {
+        return NativeCommandRegistration.literal("ingest").requires(GATE)
+                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> ModdedCommandHelp.send(context.getSource(), "ingest")))
+                .then(NativeCommandRegistration.literal("mods")
+                        .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> ingest(context.getSource(), "")))
+                        .then(NativeCommandRegistration.argument("arguments", StringArgumentType.greedyString()).suggests(INGEST_ARGUMENTS)
+                                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) ->
+                                        ingest(context.getSource(), StringArgumentType.getString(context, "arguments"))))));
+    }
+
+    private static int list(NativeCommandSource source) {
+        Optional<WorldgenCatalog> latest = ModdedWorldgenCatalogs.latest();
+        if (latest.isEmpty()) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.MISSING));
+            return 0;
+        }
+        WorldgenCatalog catalog = latest.get();
+        IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.HEADER,
+                MessageArgument.untrusted("name", catalog.platform()),
+                MessageArgument.untrusted("version", catalog.minecraftVersion()),
+                MessageArgument.untrusted("count", catalog.namespaces().size()),
+                MessageArgument.untrusted("value", catalog.biomes().size()),
+                MessageArgument.untrusted("value2", catalog.placedFeatures().size()),
+                MessageArgument.untrusted("value3", catalog.structures().size()),
+                MessageArgument.untrusted("value4", catalog.dimensionTypes().size()),
+                MessageArgument.untrusted("value5", catalog.levelStems().size())));
+        int quiet = 0;
+        for (NamespaceSummary summary : WorldgenCatalogSummary.namespaces(catalog)) {
+            if (!summary.hasContent()) {
+                quiet++;
+                continue;
+            }
+            IrisModdedCommands.ok(source, namespaceLine(summary));
+        }
+        if (quiet > 0) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.QUIET, MessageArgument.untrusted("count", quiet)));
+        }
+        return 1;
+    }
+
+    private static int detail(NativeCommandSource source, String namespace) {
+        Optional<WorldgenCatalog> latest = ModdedWorldgenCatalogs.latest();
+        if (latest.isEmpty()) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.MISSING));
+            return 0;
+        }
+        Optional<NamespaceSummary> found = WorldgenCatalogSummary.namespace(latest.get(), namespace);
+        if (found.isEmpty() || !found.get().hasContent()) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.UNKNOWN_NAMESPACE,
+                    MessageArgument.untrusted("name", namespace)));
+            return 0;
+        }
+        NamespaceSummary summary = found.get();
+        IrisModdedCommands.ok(source, namespaceLine(summary));
+        if (!summary.biomes().isEmpty()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.DETAIL_BIOMES,
+                    MessageArgument.untrusted("count", summary.biomes().size()),
+                    MessageArgument.untrusted("value", WorldgenCatalogSummary.limited(summary.biomes(), namespace, DETAIL_LIMIT))));
+        }
+        if (!summary.placedFeatures().isEmpty()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.DETAIL_FEATURES,
+                    MessageArgument.untrusted("count", summary.placedFeatures().size()),
+                    MessageArgument.untrusted("value", WorldgenCatalogSummary.featureTypes(summary.featureTypes(), DETAIL_LIMIT))));
+        }
+        if (!summary.structures().isEmpty()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.DETAIL_STRUCTURES,
+                    MessageArgument.untrusted("count", summary.structures().size()),
+                    MessageArgument.untrusted("value", WorldgenCatalogSummary.limited(summary.structures(), namespace, DETAIL_LIMIT))));
+        }
+        if (!summary.dimensionTypes().isEmpty() || !summary.levelStems().isEmpty()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.DETAIL_DIMENSIONS,
+                    MessageArgument.untrusted("value", orNone(WorldgenCatalogSummary.limited(summary.dimensionTypes(), namespace, DETAIL_LIMIT))),
+                    MessageArgument.untrusted("value2", orNone(WorldgenCatalogSummary.limited(summary.levelStems(), namespace, DETAIL_LIMIT)))));
+        }
+        return 1;
+    }
+
+    private static int refresh(NativeCommandSource source) {
+        NativeModdedServer server = source.server();
+        IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.REFRESHING));
+        ModdedWorldgenCatalogs.capture(server).whenComplete((CaptureResult result, Throwable failure) ->
+                source.execute(() -> reportRefresh(source, result, failure)));
+        return 1;
+    }
+
+    private static void reportRefresh(NativeCommandSource source, CaptureResult result, Throwable failure) {
+        if (failure != null) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.REFRESH_FAILED,
+                    MessageArgument.untrusted("reason", reason(failure))));
+            return;
+        }
+        IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.REFRESHED,
+                MessageArgument.untrusted("duration", result.millis() + " ms"),
+                MessageArgument.untrusted("path", result.file().toString())));
+    }
+
+    private static int ingest(NativeCommandSource source, String raw) {
+        ModIngestArguments arguments;
+        try {
+            arguments = ModIngestArguments.parse(raw);
+        } catch (IllegalArgumentException invalid) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_INVALID,
+                    MessageArgument.untrusted("reason", invalid.getMessage())));
+            return 0;
+        }
+        Optional<WorldgenCatalog> catalog = ModdedWorldgenCatalogs.latest();
+        if (catalog.isEmpty()) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.MISSING));
+            return 0;
+        }
+        File packsRoot = ModdedPackCommands.packsRoot();
+        File sourcePack = PackDirectoryResolver.resolveExisting(packsRoot, arguments.sourcePack());
+        if (sourcePack == null) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_PACK_MISSING,
+                    MessageArgument.untrusted("pack", arguments.sourcePack()),
+                    MessageArgument.untrusted("path", packsRoot.getAbsolutePath())));
+            return 0;
+        }
+        Path targetPack = packsRoot.toPath().toAbsolutePath().normalize().resolve(arguments.targetPack());
+        ModIngestRequest request = new ModIngestRequest(sourcePack.toPath(), targetPack, arguments.dimension(),
+                catalog.get(), arguments.namespaces(), arguments.replace());
+        IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_STARTED,
+                MessageArgument.untrusted("source", arguments.sourcePack()),
+                MessageArgument.untrusted("target", arguments.targetPack()),
+                MessageArgument.untrusted("dimension", arguments.dimension())));
+        Thread worker = new Thread(() -> runIngest(source, request), "Iris Mod Ingest");
+        worker.setDaemon(true);
+        worker.start();
+        return 1;
+    }
+
+    private static void runIngest(NativeCommandSource source, ModIngestRequest request) {
+        try {
+            ModIngestReport report = ModIngester.ingest(request);
+            source.execute(() -> reportIngest(source, report));
+        } catch (IOException | RuntimeException failure) {
+            ModdedIrisLog.error("Iris mod ingest into " + request.targetPack() + " failed", failure);
+            String reason = reason(failure);
+            source.execute(() -> IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_FAILED,
+                    MessageArgument.untrusted("reason", reason))));
+        }
+    }
+
+    private static void reportIngest(NativeCommandSource source, ModIngestReport report) {
+        for (String line : report.summaryLines()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_LINE, MessageArgument.untrusted("summary", line)));
+        }
+        IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCatalogMessages.INGEST_COMPLETE,
+                MessageArgument.untrusted("path", report.targetPack().toString())));
+    }
+
+    private static String namespaceLine(NamespaceSummary summary) {
+        String version = summary.namespace().version().isEmpty() ? NONE : summary.namespace().version();
+        return IrisLanguage.plain(ModdedCatalogMessages.NAMESPACE,
+                MessageArgument.untrusted("name", summary.namespace().namespace()),
+                MessageArgument.untrusted("version", version),
+                MessageArgument.untrusted("value", summary.biomes().size()),
+                MessageArgument.untrusted("value2", summary.placedFeatures().size()),
+                MessageArgument.untrusted("detail", orNone(WorldgenCatalogSummary.featureTypes(summary.featureTypes(), LIST_FEATURE_TYPES))),
+                MessageArgument.untrusted("value3", summary.structures().size()),
+                MessageArgument.untrusted("value4", summary.dimensionTypes().size()),
+                MessageArgument.untrusted("value5", summary.levelStems().size()));
+    }
+
+    private static String orNone(String value) {
+        return value.isEmpty() ? NONE : value;
+    }
+
+    private static String reason(Throwable failure) {
+        Throwable cause = failure instanceof CompletionException && failure.getCause() != null ? failure.getCause() : failure;
+        String message = cause.getMessage();
+        return message == null || message.isBlank() ? cause.getClass().getSimpleName() : message;
+    }
+
+    private static List<String> contentNamespaces() {
+        Optional<WorldgenCatalog> latest = ModdedWorldgenCatalogs.latest();
+        if (latest.isEmpty()) {
+            return List.of();
+        }
+        NamespaceCache cached = NAMESPACE_CACHE.get();
+        if (cached != null && cached.catalog() == latest.get()) {
+            return cached.namespaces();
+        }
+        List<String> namespaces = new ArrayList<>();
+        for (NamespaceSummary summary : WorldgenCatalogSummary.namespaces(latest.get())) {
+            if (summary.hasContent()) {
+                namespaces.add(summary.namespace().namespace());
+            }
+        }
+        NamespaceCache created = new NamespaceCache(latest.get(), List.copyOf(namespaces));
+        NAMESPACE_CACHE.set(created);
+        return created.namespaces();
+    }
+
+    private static CompletableFuture<Suggestions> suggestIngestArguments(CommandContext<NativeCommandSource> context,
+                                                                         SuggestionsBuilder builder) {
+        String remaining = builder.getRemaining();
+        int lastSpace = remaining.lastIndexOf(' ');
+        int bareArguments = 0;
+        List<String> usedOptions = new ArrayList<>(3);
+        for (String token : remaining.substring(0, Math.max(0, lastSpace)).trim().split("\\s+")) {
+            if (token.isEmpty()) {
+                continue;
+            }
+            int equals = token.indexOf('=');
+            if (equals < 0) {
+                bareArguments++;
+            } else {
+                usedOptions.add(token.substring(0, equals + 1));
+            }
+        }
+        SuggestionsBuilder current = builder.createOffset(builder.getStart() + lastSpace + 1);
+        if (bareArguments < 2) {
+            List<String> packs = new ArrayList<>();
+            for (File pack : PackDirectoryResolver.listVisiblePackDirectories(ModdedPackCommands.packsRoot())) {
+                packs.add(pack.getName());
+            }
+            return NativeCommandRegistration.suggest(packs, current);
+        }
+        List<String> options = new ArrayList<>(ModIngestArguments.OPTION_SUGGESTIONS.size());
+        for (String option : ModIngestArguments.OPTION_SUGGESTIONS) {
+            if (!usedOptions.contains(option.substring(0, option.indexOf('=') + 1))) {
+                options.add(option);
+            }
+        }
+        return NativeCommandRegistration.suggest(options, current);
+    }
+
+    private record NamespaceCache(WorldgenCatalog catalog, List<String> namespaces) {
+    }
+}

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

@@ -20,6 +20,7 @@ package art.arcane.iris.modded.command;
 
 import art.arcane.iris.localization.IrisLanguage;
 import art.arcane.iris.localization.IrisMessages;
+import art.arcane.iris.modded.localization.ModdedCatalogMessages;
 import art.arcane.iris.modded.localization.ModdedHelpMessages;
 import art.arcane.volmlib.util.director.help.DirectorHelpMessages;
 import art.arcane.volmlib.util.localization.MessageArgument;
@@ -68,6 +69,8 @@ final class ModdedCommandHelp {
                 Entry.command("debug", "", ModdedHelpMessages.COMMAND_DEBUG_TOGGLE_IRIS_DEBUG_LOGGING_AND_SAVE_SETTINGS_JSON),
                 Entry.command("reload", "", ModdedHelpMessages.COMMAND_RELOAD_RELOAD_SETTINGS_JSON_ALSO_HOTLOADED_AUTOMATICALLY_EVERY_3S),
                 Entry.command("download", "<pack=overworld|pack=underworld|link=<zip-url>> [overwrite=true]", ModdedHelpMessages.COMMAND_DOWNLOAD_DOWNLOAD_A_PACK_PROJECT, "dl"),
+                Entry.command("catalog", "[namespace|refresh]", ModdedCatalogMessages.HELP_CATALOG),
+                Entry.group("ingest", ModdedCatalogMessages.HELP_INGEST),
                 Entry.command("metrics", "", ModdedHelpMessages.COMMAND_METRICS_PRINT_GENERATION_METRICS_FOR_YOUR_CURRENT_IRIS_DIMENSION, "measure"),
                 Entry.command("regen", "[radius]", ModdedHelpMessages.COMMAND_REGEN_DELETE_AND_REGENERATE_NEARBY_CHUNKS_IN_PLACE, "rg"),
                 Entry.group("pregen", ModdedHelpMessages.GROUP_PREGEN_PREGENERATE_AN_IRIS_DIMENSION, "pregenerate"),
@@ -165,6 +168,9 @@ final class ModdedCommandHelp {
                 Entry.command("compat", "[pack]", ModdedHelpMessages.COMMAND_COMPAT_SHOW_CONTENT_THAT_CANNOT_GENERATE_ON_THIS_MINECRAFT_VERSION, "cp")
         ));
         SECTIONS.put("pk", SECTIONS.get("pack"));
+        SECTIONS.put("ingest", List.of(
+                Entry.command("mods", "<source> <target> [dimension=<key>] [namespaces=<a,b>] [replace=true]", ModdedCatalogMessages.HELP_INGEST_MODS)
+        ));
         SECTIONS.put("world", List.of(
                 Entry.command("enable", "<dimension> <pack|pack:dimensionKey> [seed|random]", ModdedHelpMessages.COMMAND_ENABLE_CREATE_AND_INJECT_A_PERSISTENT_IRIS_DIMENSION_AT_RUNTIME_DOWNLOADS_THE_PACK, "create"),
                 Entry.command("replace-overworld", "<pack|pack:dimensionKey> [seed|random]", ModdedHelpMessages.COMMAND_REPLACE_OVERWORLD_INJECT_AN_IRIS_PRIMARY_WORLD_AND_ROUTE_PLAYERS_THERE_INSTEAD_OF_THE),

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

@@ -114,6 +114,9 @@ final class ModdedCommandTree {
         root.then(downloadTree("download"));
         root.then(downloadTree("dl"));
 
+        root.then(ModdedCatalogCommands.catalogTree());
+        root.then(ModdedCatalogCommands.ingestTree());
+
         root.then(metricsTree("metrics"));
         root.then(metricsTree("measure"));
 

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

@@ -0,0 +1,145 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.localization;
+
+import art.arcane.volmlib.util.localization.MessageKey;
+import art.arcane.volmlib.util.localization.TextKey;
+
+import java.util.List;
+
+public final class ModdedCatalogMessages {
+    public static final TextKey MISSING = TextKey.of(
+            "iris.modded.catalog.missing",
+            "No worldgen catalog has been captured yet. Run /iris catalog refresh."
+    );
+    public static final TextKey HEADER = TextKey.of(
+            "iris.modded.catalog.header",
+            "Worldgen catalog ({name} {version}): {count} namespaces, {value} biomes, {value2} placed features, "
+                    + "{value3} structures, {value4} dimension types, {value5} level stems"
+    );
+    public static final TextKey NAMESPACE = TextKey.of(
+            "iris.modded.catalog.namespace",
+            "{name} {version}: {value} biomes, {value2} placed features ({detail}), {value3} structures, "
+                    + "{value4} dimension types, {value5} level stems"
+    );
+    public static final TextKey QUIET = TextKey.of(
+            "iris.modded.catalog.quiet",
+            "{count} more loaded mods have no worldgen content."
+    );
+    public static final TextKey UNKNOWN_NAMESPACE = TextKey.of(
+            "iris.modded.catalog.unknown_namespace",
+            "The worldgen catalog has no content from namespace {name}."
+    );
+    public static final TextKey DETAIL_BIOMES = TextKey.of(
+            "iris.modded.catalog.detail_biomes",
+            "Biomes ({count}): {value}"
+    );
+    public static final TextKey DETAIL_FEATURES = TextKey.of(
+            "iris.modded.catalog.detail_features",
+            "Placed features by type ({count}): {value}"
+    );
+    public static final TextKey DETAIL_STRUCTURES = TextKey.of(
+            "iris.modded.catalog.detail_structures",
+            "Structures ({count}): {value}"
+    );
+    public static final TextKey DETAIL_DIMENSIONS = TextKey.of(
+            "iris.modded.catalog.detail_dimensions",
+            "Dimension types: {value}; level stems: {value2}"
+    );
+    public static final TextKey REFRESHING = TextKey.of(
+            "iris.modded.catalog.refreshing",
+            "Capturing the worldgen catalog..."
+    );
+    public static final TextKey REFRESHED = TextKey.of(
+            "iris.modded.catalog.refreshed",
+            "Worldgen catalog captured in {duration}: {path}"
+    );
+    public static final TextKey REFRESH_FAILED = TextKey.of(
+            "iris.modded.catalog.refresh_failed",
+            "Worldgen catalog capture failed: {reason}"
+    );
+    public static final TextKey INGEST_INVALID = TextKey.of(
+            "iris.modded.catalog.ingest_invalid",
+            "Invalid arguments: {reason}. Usage: /iris ingest mods <source> <target> [dimension=<key>] "
+                    + "[namespaces=<a,b>] [replace=true]"
+    );
+    public static final TextKey INGEST_PACK_MISSING = TextKey.of(
+            "iris.modded.catalog.ingest_pack_missing",
+            "Pack '{pack}' was not found under {path}."
+    );
+    public static final TextKey INGEST_STARTED = TextKey.of(
+            "iris.modded.catalog.ingest_started",
+            "Ingesting mod worldgen from '{source}' into '{target}' (dimension {dimension})..."
+    );
+    public static final TextKey INGEST_FAILED = TextKey.of(
+            "iris.modded.catalog.ingest_failed",
+            "Mod ingest failed: {reason}"
+    );
+    public static final TextKey INGEST_LINE = TextKey.of(
+            "iris.modded.catalog.ingest_line",
+            "  {summary}"
+    );
+    public static final TextKey INGEST_COMPLETE = TextKey.of(
+            "iris.modded.catalog.ingest_complete",
+            "Mod ingest finished: {path}"
+    );
+    public static final TextKey HELP_CATALOG = TextKey.of(
+            "iris.modded.help.entry.command.catalog",
+            "List the worldgen content of loaded mods, show one namespace, or capture it again"
+    );
+    public static final TextKey HELP_INGEST = TextKey.of(
+            "iris.modded.help.entry.group.ingest",
+            "Build Iris packs from the worldgen content of loaded mods"
+    );
+    public static final TextKey HELP_INGEST_MODS = TextKey.of(
+            "iris.modded.help.entry.command.ingest_mods",
+            "Copy a source pack into a new target pack and adopt the worldgen of loaded mods"
+    );
+
+    private static final List<MessageKey> KEYS = List.of(
+            MISSING,
+            HEADER,
+            NAMESPACE,
+            QUIET,
+            UNKNOWN_NAMESPACE,
+            DETAIL_BIOMES,
+            DETAIL_FEATURES,
+            DETAIL_STRUCTURES,
+            DETAIL_DIMENSIONS,
+            REFRESHING,
+            REFRESHED,
+            REFRESH_FAILED,
+            INGEST_INVALID,
+            INGEST_PACK_MISSING,
+            INGEST_STARTED,
+            INGEST_FAILED,
+            INGEST_LINE,
+            INGEST_COMPLETE,
+            HELP_CATALOG,
+            HELP_INGEST,
+            HELP_INGEST_MODS
+    );
+
+    private ModdedCatalogMessages() {
+    }
+
+    public static List<MessageKey> keys() {
+        return KEYS;
+    }
+}

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

@@ -12,6 +12,7 @@ public final class ModdedMessageContributor implements IrisMessageContributor {
         List<MessageKey> keys = new ArrayList<>();
         keys.addAll(ModdedCommandMessages.keys());
         keys.addAll(ModdedHelpMessages.keys());
+        keys.addAll(ModdedCatalogMessages.keys());
         keys.addAll(ClientUiMessages.keys());
         return List.copyOf(keys);
     }

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

@@ -1,5 +1,6 @@
 package art.arcane.iris.modded;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModMetadata;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedLoader;
 import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 
@@ -20,6 +21,7 @@ import org.junit.rules.TemporaryFolder;
 
 import java.io.File;
 import java.nio.file.Path;
+import java.util.List;
 
 import static org.junit.Assert.assertEquals;
 
@@ -45,6 +47,11 @@ public class ModdedPlatformPathsTest {
                 return "0.0.0";
             }
 
+            @Override
+            public List<NativeModMetadata> mods() {
+                return List.of();
+            }
+
             @Override
             public NativeModdedServer currentServer() {
                 return null;

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

@@ -0,0 +1,129 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.iris.pack.ingest.catalog.CatalogBiome;
+import art.arcane.iris.pack.ingest.catalog.CatalogLevelStem;
+import art.arcane.iris.pack.ingest.catalog.CatalogNamespace;
+import art.arcane.iris.pack.ingest.catalog.CatalogPlacedFeature;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalogFingerprint;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModMetadata;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.EncodeFailures;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenBiome;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenDimensionType;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenLevelStem;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenPlacedFeature;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenSpawn;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenStructure;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonPrimitive;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+public class WorldgenCatalogAssemblerTest {
+    private static final CatalogCaptureContext CONTEXT = new CatalogCaptureContext("26.3", "neoforge", 1234L, List.of(
+            new NativeModMetadata("minecraft", "Minecraft", "26.3"),
+            new NativeModMetadata("examplemod", "Example Mod", "1.0.0"),
+            new NativeModMetadata("quietmod", "Quiet Mod", "2.0.0")));
+
+    @Test
+    public void namespacesCombineLoaderModsWithRegistryKeyNamespaces() {
+        WorldgenCatalog catalog = WorldgenCatalogAssembler.assemble(snapshot(), CONTEXT);
+
+        assertEquals(List.of(
+                new CatalogNamespace("datapack", "datapack", ""),
+                new CatalogNamespace("examplemod", "Example Mod", "1.0.0"),
+                new CatalogNamespace("minecraft", "Minecraft", "26.3"),
+                new CatalogNamespace("quietmod", "Quiet Mod", "2.0.0")), catalog.namespaces());
+    }
+
+    @Test
+    public void minecraftNamespaceFallsBackToTheRunningVersion() {
+        CatalogCaptureContext context = new CatalogCaptureContext("26.3", "forge", 1L, List.of());
+
+        WorldgenCatalog catalog = WorldgenCatalogAssembler.assemble(snapshot(), context);
+
+        assertEquals(new CatalogNamespace("minecraft", "Minecraft", "26.3"), catalog.namespaces().get(2));
+    }
+
+    @Test
+    public void recordsAreCopiedWithTheirJson() {
+        NativeWorldgenSnapshot snapshot = snapshot();
+
+        WorldgenCatalog catalog = WorldgenCatalogAssembler.assemble(snapshot, CONTEXT);
+
+        assertEquals(WorldgenCatalog.FORMAT, catalog.format());
+        assertEquals("26.3", catalog.minecraftVersion());
+        assertEquals("neoforge", catalog.platform());
+        assertEquals(1234L, catalog.capturedAtEpochMillis());
+        CatalogBiome glade = catalog.biomes().getFirst();
+        assertEquals("examplemod:glade", glade.key());
+        assertEquals(0.7F, glade.temperature(), 0F);
+        assertEquals(0.4F, glade.downfall(), 0F);
+        assertEquals(List.of(List.of(), List.of("examplemod:ore_glimmer")), glade.featureSteps());
+        assertEquals("creature", glade.spawns().getFirst().category());
+        assertSame(snapshot.biomes().getFirst().definition(), glade.definition());
+        CatalogPlacedFeature ore = catalog.placedFeatures().getFirst();
+        assertEquals("minecraft:ore", ore.featureType());
+        assertSame(snapshot.placedFeatures().getFirst().config(), ore.config());
+        CatalogLevelStem stem = catalog.levelStems().getFirst();
+        assertEquals("minecraft:multi_noise", stem.biomeSourceType());
+        assertEquals("examplemod:towers", catalog.structures().getFirst().structureSets().getFirst());
+        assertEquals(384, catalog.dimensionTypes().getFirst().height());
+    }
+
+    @Test
+    public void fingerprintCoversNamespacesAndEveryRegistryKey() {
+        WorldgenCatalog catalog = WorldgenCatalogAssembler.assemble(snapshot(), CONTEXT);
+
+        String expected = WorldgenCatalogFingerprint.of(catalog.namespaces(), Map.of(
+                "biome", List.of("datapack:dunes", "examplemod:glade"),
+                "placed_feature", List.of("examplemod:ore_glimmer"),
+                "structure", List.of("examplemod:tower"),
+                "dimension_type", List.of("minecraft:overworld"),
+                "level_stem", List.of("minecraft:overworld")));
+        assertEquals(expected, catalog.contentFingerprint());
+    }
+
+    static NativeWorldgenSnapshot snapshot() {
+        JsonObject definition = new JsonObject();
+        definition.add("downfall", new JsonPrimitive(0.4F));
+        JsonObject config = new JsonObject();
+        config.add("type", new JsonPrimitive("minecraft:ore"));
+        return new NativeWorldgenSnapshot(
+                List.of(new WorldgenBiome("examplemod:glade", 0.7F, 0.4F, true, List.of("minecraft:is_overworld"),
+                                List.of(List.of(), List.of("examplemod:ore_glimmer")),
+                                List.of(new WorldgenSpawn("creature", "minecraft:sheep", 12, 2, 4)), definition),
+                        new WorldgenBiome("datapack:dunes", 2.0F, 0F, false, List.of(), List.of(), List.of(), null)),
+                List.of(new WorldgenPlacedFeature("examplemod:ore_glimmer", "examplemod:ore_glimmer", "minecraft:ore", config, null)),
+                List.of(new WorldgenStructure("examplemod:tower", "minecraft:jigsaw", "surface_structures", "beard_thin",
+                        "examplemod:has_tower", List.of("examplemod:glade"), List.of("examplemod:towers"))),
+                List.of(new WorldgenDimensionType("minecraft:overworld", -64, 384, 384, null)),
+                List.of(new WorldgenLevelStem("minecraft:overworld", "minecraft:overworld", "minecraft:noise",
+                        "minecraft:multi_noise", null)),
+                new EncodeFailures(0, List.of(), null));
+    }
+}

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

@@ -0,0 +1,117 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.catalog;
+
+import art.arcane.iris.modded.catalog.WorldgenCatalogSummary.NamespaceSummary;
+import art.arcane.iris.modded.catalog.WorldgenCatalogSummary.TypeCount;
+import art.arcane.iris.pack.ingest.catalog.CatalogBiome;
+import art.arcane.iris.pack.ingest.catalog.CatalogDimensionType;
+import art.arcane.iris.pack.ingest.catalog.CatalogLevelStem;
+import art.arcane.iris.pack.ingest.catalog.CatalogNamespace;
+import art.arcane.iris.pack.ingest.catalog.CatalogPlacedFeature;
+import art.arcane.iris.pack.ingest.catalog.CatalogStructure;
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Optional;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class WorldgenCatalogSummaryTest {
+    @Test
+    public void summariesCountEveryRegistryPerNamespace() {
+        List<NamespaceSummary> summaries = WorldgenCatalogSummary.namespaces(catalog());
+
+        assertEquals(List.of("examplemod", "minecraft", "quietmod"),
+                summaries.stream().map((NamespaceSummary summary) -> summary.namespace().namespace()).toList());
+        NamespaceSummary example = summaries.getFirst();
+        assertEquals(List.of("examplemod:glade", "examplemod:marsh"), example.biomes());
+        assertEquals(6, example.placedFeatures().size());
+        assertEquals(List.of("examplemod:tower"), example.structures());
+        assertEquals(List.of("examplemod:sky"), example.dimensionTypes());
+        assertEquals(List.of("examplemod:sky"), example.levelStems());
+        assertTrue(example.hasContent());
+        assertFalse(summaries.get(2).hasContent());
+    }
+
+    @Test
+    public void featureTypesAreRankedByCountThenName() {
+        NamespaceSummary example = WorldgenCatalogSummary.namespace(catalog(), "examplemod").orElseThrow();
+
+        assertEquals(List.of(new TypeCount("minecraft:ore", 3), new TypeCount("minecraft:random_patch", 2),
+                new TypeCount("examplemod:big_tree", 1)), example.featureTypes());
+        assertEquals("ore 3, random_patch 2 (+1 more)", WorldgenCatalogSummary.featureTypes(example.featureTypes(), 2));
+        assertEquals("ore 3, random_patch 2, examplemod:big_tree 1",
+                WorldgenCatalogSummary.featureTypes(example.featureTypes(), 5));
+    }
+
+    @Test
+    public void unknownNamespaceHasNoSummary() {
+        Optional<NamespaceSummary> missing = WorldgenCatalogSummary.namespace(catalog(), "missingmod");
+
+        assertTrue(missing.isEmpty());
+    }
+
+    @Test
+    public void keyNamespacesWithoutModMetadataStillSummarize() {
+        WorldgenCatalog catalog = new WorldgenCatalog(WorldgenCatalog.FORMAT, "26.3", "fabric", 1L, "x",
+                List.of(), List.of(biome("datapack:dunes")), List.of(), List.of(), List.of(), List.of());
+
+        NamespaceSummary summary = WorldgenCatalogSummary.namespace(catalog, "datapack").orElseThrow();
+
+        assertEquals(new CatalogNamespace("datapack", "datapack", ""), summary.namespace());
+        assertEquals(List.of("datapack:dunes"), summary.biomes());
+    }
+
+    @Test
+    public void limitedListsShortenOwnKeysAndCountTheRest() {
+        assertEquals("glade, marsh (+1 more)",
+                WorldgenCatalogSummary.limited(List.of("examplemod:glade", "examplemod:marsh", "examplemod:moor"), "examplemod", 2));
+        assertEquals("glade, minecraft:plains",
+                WorldgenCatalogSummary.limited(List.of("examplemod:glade", "minecraft:plains"), "examplemod", 5));
+        assertEquals("", WorldgenCatalogSummary.limited(List.of(), "examplemod", 5));
+    }
+
+    private static WorldgenCatalog catalog() {
+        return new WorldgenCatalog(WorldgenCatalog.FORMAT, "26.3", "neoforge", 1L, "x",
+                List.of(new CatalogNamespace("examplemod", "Example Mod", "1.0.0"),
+                        new CatalogNamespace("minecraft", "Minecraft", "26.3"),
+                        new CatalogNamespace("quietmod", "Quiet Mod", "2.0.0")),
+                List.of(biome("examplemod:marsh"), biome("examplemod:glade"), biome("minecraft:plains")),
+                List.of(feature("examplemod:ore_a", "minecraft:ore"), feature("examplemod:ore_b", "minecraft:ore"),
+                        feature("examplemod:ore_c", "minecraft:ore"), feature("examplemod:patch_a", "minecraft:random_patch"),
+                        feature("examplemod:patch_b", "minecraft:random_patch"), feature("examplemod:tree", "examplemod:big_tree"),
+                        feature("minecraft:ore_iron", "minecraft:ore")),
+                List.of(new CatalogStructure("examplemod:tower", "minecraft:jigsaw", "surface_structures", "none", "",
+                        List.of(), List.of())),
+                List.of(new CatalogDimensionType("examplemod:sky", 0, 256, 256, null)),
+                List.of(new CatalogLevelStem("examplemod:sky", "examplemod:sky", "minecraft:noise", "minecraft:fixed", null)));
+    }
+
+    private static CatalogBiome biome(String key) {
+        return new CatalogBiome(key, 0.5F, 0.5F, true, List.of(), List.of(), List.of(), null);
+    }
+
+    private static CatalogPlacedFeature feature(String key, String type) {
+        return new CatalogPlacedFeature(key, key, type, null, null);
+    }
+}

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

@@ -0,0 +1,80 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.command;
+
+import org.junit.Test;
+
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class ModIngestArgumentsTest {
+    @Test
+    public void requiredPacksBindPositionallyAndOptionalsDefault() {
+        ModIngestArguments arguments = ModIngestArguments.parse("overworld modded_overworld");
+
+        assertEquals("overworld", arguments.sourcePack());
+        assertEquals("modded_overworld", arguments.targetPack());
+        assertEquals("overworld", arguments.dimension());
+        assertEquals(Set.of(), arguments.namespaces());
+        assertFalse(arguments.replace());
+    }
+
+    @Test
+    public void keyedOptionalsAreParsedInAnyOrder() {
+        ModIngestArguments arguments = ModIngestArguments.parse(
+                "  overworld   modded  replace=true namespaces=biomesoplenty,terralith dimension=overworld_alt ");
+
+        assertEquals("overworld_alt", arguments.dimension());
+        assertEquals(Set.of("biomesoplenty", "terralith"), arguments.namespaces());
+        assertTrue(arguments.replace());
+    }
+
+    @Test
+    public void missingTargetIsRejected() {
+        IllegalArgumentException failure = assertThrows(IllegalArgumentException.class,
+                () -> ModIngestArguments.parse("overworld"));
+
+        assertEquals("missing target pack", failure.getMessage());
+    }
+
+    @Test
+    public void strayPositionalsAndUnknownKeysAreRejected() {
+        assertEquals("unexpected argument 'extra'", reason("overworld modded extra"));
+        assertEquals("unknown option 'seed'", reason("overworld modded seed=1"));
+        assertEquals("option 'replace' given twice", reason("overworld modded replace=true replace=false"));
+    }
+
+    @Test
+    public void valuesAreValidated() {
+        assertEquals("replace must be true or false", reason("overworld modded replace=yes"));
+        assertEquals("invalid pack name '../evil'", reason("../evil modded"));
+        assertEquals("invalid dimension key 'a..b'", reason("overworld modded dimension=a..b"));
+        assertEquals("invalid namespace 'Bad'", reason("overworld modded namespaces=ok,Bad"));
+        assertEquals("namespaces must not be empty", reason("overworld modded namespaces=,"));
+        assertEquals("source and target must be different packs", reason("overworld overworld"));
+    }
+
+    private static String reason(String raw) {
+        return assertThrows(IllegalArgumentException.class, () -> ModIngestArguments.parse(raw)).getMessage();
+    }
+}

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

@@ -0,0 +1,73 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded.command;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandRegistration;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.tree.CommandNode;
+import net.minecraft.SharedConstants;
+import net.minecraft.commands.CommandSourceStack;
+import net.minecraft.server.Bootstrap;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class ModdedCatalogCommandsTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void catalogAndIngestCommandsAreRegistered() {
+        CommandDispatcher<CommandSourceStack> dispatcher = new CommandDispatcher<>();
+        IrisModdedCommands.register(new NativeCommandRegistration(dispatcher));
+
+        CommandNode<CommandSourceStack> iris = child(dispatcher.getRoot(), "iris");
+        CommandNode<CommandSourceStack> catalog = child(iris, "catalog");
+        assertNotNull(catalog.getCommand());
+        assertNotNull(child(catalog, "refresh").getCommand());
+        assertNotNull(child(catalog, "namespace").getCommand());
+        CommandNode<CommandSourceStack> ingest = child(iris, "ingest");
+        assertNotNull(ingest.getCommand());
+        CommandNode<CommandSourceStack> mods = child(ingest, "mods");
+        assertNotNull(child(mods, "arguments").getCommand());
+    }
+
+    @Test
+    public void helpDocumentsCatalogAndIngest() {
+        assertTrue(ModdedCommandHelp.documents("", "catalog"));
+        assertTrue(ModdedCommandHelp.documents("", "ingest"));
+        assertTrue(ModdedCommandHelp.documents("ingest", "mods"));
+        List<String> lines = ModdedCommandHelp.consoleLines("ingest");
+        assertTrue(lines.stream().anyMatch((String line) ->
+                line.startsWith("/iris ingest mods <source> <target> [dimension=<key>] [namespaces=<a,b>] [replace=true] - ")));
+    }
+
+    private static CommandNode<CommandSourceStack> child(CommandNode<CommandSourceStack> parent, String name) {
+        CommandNode<CommandSourceStack> child = parent.getChild(name);
+        assertNotNull(name, child);
+        return child;
+    }
+}

adapters/modded-common/src/test/java/art/arcane/volmlib/nativelib/minecraft26_2/modded/NativeWorldgenScanTest.java

@@ -0,0 +1,129 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.volmlib.nativelib.minecraft26_2.modded;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenBiome;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldgenSnapshot.WorldgenPlacedFeature;
+import com.google.gson.JsonParser;
+import com.mojang.serialization.JsonOps;
+import com.mojang.serialization.Lifecycle;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Holder;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.RegistrationInfo;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.carver.WorldCarver;
+import net.minecraft.world.level.levelgen.feature.Feature;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeWorldgenScanTest {
+    private static final String BIOME_JSON = "{\"has_precipitation\":true,\"temperature\":0.8,\"downfall\":0.4,"
+            + "\"effects\":{\"water_color\":\"#3f76e4\"},\"carvers\":[],"
+            + "\"features\":[[],[],[],[],[],[],[\"examplemod:ore_glimmer\"]]}";
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void scanReadsLiveFeatureStepsAndEncodesDefinitions() {
+        NativeWorldgenSnapshot snapshot = NativeWorldgenScan.scan(server(), loader()).encode();
+
+        WorldgenBiome biome = snapshot.biomes().getFirst();
+        assertEquals("examplemod:glade", biome.key());
+        assertEquals(0.8F, biome.temperature(), 0F);
+        assertEquals(0.4F, biome.downfall(), 0.0001F);
+        assertTrue(biome.hasPrecipitation());
+        assertEquals(GenerationStep.Decoration.values().length, biome.featureSteps().size());
+        assertEquals(List.of("examplemod:ore_glimmer"),
+                biome.featureSteps().get(GenerationStep.Decoration.UNDERGROUND_ORES.ordinal()));
+        assertNotNull(biome.definition());
+        assertEquals(0.4F, biome.definition().getAsJsonObject().get("downfall").getAsFloat(), 0.0001F);
+    }
+
+    @Test
+    public void unencodableFeaturesStayInTheCatalogWithoutJson() {
+        NativeWorldgenSnapshot snapshot = NativeWorldgenScan.scan(server(), loader()).encode();
+
+        WorldgenPlacedFeature feature = snapshot.placedFeatures().getFirst();
+        assertEquals("examplemod:ore_glimmer", feature.key());
+        assertEquals("", feature.feature());
+        assertNull(feature.config());
+        assertTrue(feature.placement().isJsonArray());
+        assertEquals(1, snapshot.failures().count());
+        assertTrue(snapshot.failures().samples().getFirst().startsWith("feature of examplemod:ore_glimmer"));
+        assertTrue(snapshot.levelStems().isEmpty());
+    }
+
+    private static NativeModdedServer server() {
+        MappedRegistry<PlacedFeature> features = new MappedRegistry<>(Registries.PLACED_FEATURE, Lifecycle.stable());
+        features.register(ResourceKey.create(Registries.PLACED_FEATURE, Identifier.parse("examplemod:ore_glimmer")),
+                new PlacedFeature(Holder.direct(mock(Feature.class)), List.of()), RegistrationInfo.BUILT_IN);
+        features.freeze();
+        MappedRegistry<WorldCarver> carvers = new MappedRegistry<>(Registries.CARVER, Lifecycle.stable());
+        carvers.freeze();
+        MappedRegistry<Biome> biomes = new MappedRegistry<>(Registries.BIOME, Lifecycle.stable());
+        MappedRegistry<Structure> structures = new MappedRegistry<>(Registries.STRUCTURE, Lifecycle.stable());
+        structures.freeze();
+        MappedRegistry<StructureSet> structureSets = new MappedRegistry<>(Registries.STRUCTURE_SET, Lifecycle.stable());
+        structureSets.freeze();
+        MappedRegistry<DimensionType> dimensionTypes = new MappedRegistry<>(Registries.DIMENSION_TYPE, Lifecycle.stable());
+        dimensionTypes.freeze();
+        RegistryAccess access = new RegistryAccess.ImmutableRegistryAccess(
+                List.of(biomes, features, carvers, structures, structureSets, dimensionTypes));
+        Biome biome = Biome.DIRECT_CODEC.parse(RegistryOps.create(JsonOps.INSTANCE, access),
+                JsonParser.parseString(BIOME_JSON)).getOrThrow();
+        biomes.register(ResourceKey.create(Registries.BIOME, Identifier.parse("examplemod:glade")), biome, RegistrationInfo.BUILT_IN);
+        biomes.freeze();
+        MinecraftServer server = mock(MinecraftServer.class);
+        when(server.registryAccess()).thenReturn(access.freeze());
+        return NativeModdedServer.fromHandle(server);
+    }
+
+    private static NativeModdedLoader loader() {
+        NativeModdedLoader loader = mock(NativeModdedLoader.class);
+        when(loader.unmodifiedBiome(any())).thenAnswer(invocation -> invocation.getArgument(0));
+        return loader;
+    }
+}