Port seeded random Ages and authored Rocks to 26.3 beta

ports/mc263/README.md

@@ -194,6 +194,23 @@ The local `1.0.1.39-beta.1` follow-up rejects fluid at both feet and head
 height during safe-landing searches. It also refuses to carve the fallback
 platform into submerged space if no dry footing can be found.
 
+The `1.0.1.40-beta.1` port slice seeds terrain and biome selection for
+Descriptive Books with no authored symbol pages. It uses the same terrain and
+biome-controller rank weights as the 1.21.1 line, freezes the resulting plan
+in the Age index, and accepts the result after restart. The operator-only
+`age create_random <name> <seed>` probe exercises this path. Random feature,
+sky, weather, and instability choices are not yet ported; this slice covers
+terrain and biomes only.
+
+The `1.0.1.41-beta.1` slice establishes an Age-scoped decoration wrapper
+for 26.3 and accepts one Block material page immediately before a Rocks feature
+page. Newly generated surface chunks place small rock clusters made from that
+block without modifying the shared biome registry. The selected block and
+generator survive a restart. Cave and Void terrain remain unsupported for this
+first surface-feature path; unsupported combinations stay in the Binder.
+Random feature selection, unpaired materials, duplicate feature pages, and
+instability scoring remain future port steps.
+
 From the repository root:
 
 ```sh

ports/mc263/RELEASE_NOTES_1.0.1.41-beta.1.md

@@ -0,0 +1,13 @@
+# Rivencraft 26.3 beta 1.0.1.41-beta.1
+
+This beta expands Age generation on Minecraft 26.3.
+
+- Descriptive Books with no authored symbol pages now choose a seeded random terrain and biome distribution. The chosen plan is saved with the Age and restored after restart.
+- A Block material page followed by a Rocks feature page now generates small clusters of that block in newly generated surface chunks. This first feature path supports Standard, Amplified, Island, and Flat terrain; Cave and Void combinations remain unsupported.
+- Expanded dedicated-server checks cover random Age plans and authored Rocks generation across restart.
+
+The player verified the Rocks feature in game. Random feature selection, duplicate feature pages, unpaired materials, and instability scoring are not yet ported. Existing chunks are not regenerated.
+
+This 26.3 port is still experimental and does not yet include all features of the separate Minecraft 1.21.1 version. Use a test world and keep a backup. Minecraft 1.21.1 saves are not supported by this beta.
+
+Requires Minecraft 26.3, NeoForge 26.3.0.99 or a compatible 26.3 build, and Java 25.

ports/mc263/gradle.properties

@@ -7,4 +7,4 @@ neo_version=26.3.0.99
 mod_id=rivencraft
 mod_name=Rivencraft
 mod_license=LGPL-3.0-or-later
-mod_version=1.0.1.39-beta.1
+mod_version=1.0.1.41-beta.1

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/AgeLevelIndex.java

@@ -24,7 +24,9 @@ final class AgeLevelIndex extends SavedData {
                     .forGetter(index -> index.biomePlans),
             Codec.unboundedMap(Identifier.CODEC,
                     Codec.STRING.xmap(PortAgeTerrain::valueOf, PortAgeTerrain::name))
-                    .optionalFieldOf("terrain", Map.of()).forGetter(index -> index.terrain)
+                    .optionalFieldOf("terrain", Map.of()).forGetter(index -> index.terrain),
+            Codec.unboundedMap(Identifier.CODEC, PortRockPlan.CODEC).optionalFieldOf("rocks", Map.of())
+                    .forGetter(index -> index.rocks)
     ).apply(instance, AgeLevelIndex::new));
 
     static final SavedDataType<AgeLevelIndex> TYPE = new SavedDataType<>(
@@ -38,6 +40,7 @@ final class AgeLevelIndex extends SavedData {
     private final Map<Identifier, Identifier> biomeOverrides;
     private final Map<Identifier, PortBiomePlan> biomePlans;
     private final Map<Identifier, PortAgeTerrain> terrain;
+    private final Map<Identifier, PortRockPlan> rocks;
 
     private AgeLevelIndex() {
         this.ages = new LinkedHashMap<>();
@@ -45,17 +48,20 @@ final class AgeLevelIndex extends SavedData {
         this.biomeOverrides = new LinkedHashMap<>();
         this.biomePlans = new LinkedHashMap<>();
         this.terrain = new LinkedHashMap<>();
+        this.rocks = new LinkedHashMap<>();
     }
 
     private AgeLevelIndex(Map<Identifier, Long> ages, List<Identifier> retired,
                           Map<Identifier, Identifier> biomeOverrides,
                           Map<Identifier, PortBiomePlan> biomePlans,
-                          Map<Identifier, PortAgeTerrain> terrain) {
+                          Map<Identifier, PortAgeTerrain> terrain,
+                          Map<Identifier, PortRockPlan> rocks) {
         this.ages = new LinkedHashMap<>(ages);
         this.retired = new LinkedHashSet<>(retired);
         this.biomeOverrides = new LinkedHashMap<>(biomeOverrides);
         this.biomePlans = new LinkedHashMap<>(biomePlans);
         this.terrain = new LinkedHashMap<>(terrain);
+        this.rocks = new LinkedHashMap<>(rocks);
     }
 
     Map<Identifier, Long> entries() {
@@ -81,13 +87,17 @@ final class AgeLevelIndex extends SavedData {
         return terrain.getOrDefault(id, PortAgeTerrain.STANDARD);
     }
 
-    void add(Identifier id, long seed, PortBiomePlan biomePlan, PortAgeTerrain ageTerrain) {
+    PortRockPlan rocks(Identifier id) { return rocks.get(id); }
+
+    void add(Identifier id, long seed, PortBiomePlan biomePlan, PortAgeTerrain ageTerrain,
+             PortRockPlan rockPlan) {
         if (contains(id)) {
             throw new IllegalArgumentException("Age already exists: " + id);
         }
         ages.put(id, seed);
         if (biomePlan != null) biomePlans.put(id, biomePlan);
         if (ageTerrain != PortAgeTerrain.STANDARD) terrain.put(id, ageTerrain);
+        if (rockPlan != null) rocks.put(id, rockPlan);
         setDirty();
     }
 
@@ -96,16 +106,18 @@ final class AgeLevelIndex extends SavedData {
         biomeOverrides.remove(id);
         biomePlans.remove(id);
         terrain.remove(id);
+        rocks.remove(id);
         retired.add(id);
         setDirty();
     }
 
     void restoreAfterFailedRetirement(Identifier id, long seed, PortBiomePlan biomePlan,
-                                      PortAgeTerrain ageTerrain) {
+                                      PortAgeTerrain ageTerrain, PortRockPlan rockPlan) {
         if (!retired.remove(id)) throw new IllegalStateException("Age is not retired: " + id);
         ages.put(id, seed);
         if (biomePlan != null) biomePlans.put(id, biomePlan);
         if (ageTerrain != PortAgeTerrain.STANDARD) terrain.put(id, ageTerrain);
+        if (rockPlan != null) rocks.put(id, rockPlan);
         setDirty();
     }
 

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeCommands.java

@@ -112,6 +112,24 @@ public final class PortAgeCommands {
                                                                             : java.util.List.of(Identifier.withDefaultNamespace("plains"),
                                                                                     Identifier.withDefaultNamespace("forest"))));
                                                         })))))
+                        .then(Commands.literal("create_random")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    long seed = LongArgumentType.getLong(context, "seed");
+                                                    PortRandomAgeSelection.Selection selected = PortRandomAgeSelection.select(
+                                                            context.getSource().getServer(), seed);
+                                                    int created = createAge(context, selected.terrain(), selected.biomes());
+                                                    if (created != 0) context.getSource().sendSuccess(() -> Component.literal(
+                                                            "Random Age plan: terrain=" + selected.terrain()
+                                                                    + " biomes=" + selected.biomes()), false);
+                                                    return created;
+                                                }))))
+                        .then(Commands.literal("create_rocks")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.FLAT,
+                                                        null, new PortRockPlan(Identifier.withDefaultNamespace("gold_block")))))))
                         .then(Commands.literal("list")
                                 .executes(context -> {
                                     var ages = RuntimeAgeBackend.savedAges(context.getSource().getServer());
@@ -215,6 +233,9 @@ public final class PortAgeCommands {
                                         .then(Commands.argument("chunkOffset", IntegerArgumentType.integer(0))
                                                 .executes(context -> sampleAge(context,
                                                         IntegerArgumentType.getInteger(context, "chunkOffset"))))))
+                        .then(Commands.literal("rocks_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeRocks)))
                         .then(Commands.literal("biome")
                                 .then(Commands.argument("name", StringArgumentType.word())
                                         .then(Commands.argument("x", IntegerArgumentType.integer())
@@ -228,12 +249,36 @@ public final class PortAgeCommands {
 
     private static int createAge(CommandContext<CommandSourceStack> context,
                                  PortAgeTerrain terrain, PortBiomePlan biomePlan) {
+        return createAge(context, terrain, biomePlan, null);
+    }
+
+    private static int probeRocks(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null || !(level.getChunkSource().getGenerator() instanceof PortRockChunkGenerator rocks)) {
+            context.getSource().sendFailure(Component.literal("Age has no loaded Rocks generator: " + id));
+            return 0;
+        }
+        var material = net.minecraft.core.registries.BuiltInRegistries.BLOCK.getValue(rocks.rocks().material());
+        int count = 0;
+        for (int x = 0; x < 64; x++) for (int z = 0; z < 64; z++) {
+            int y = level.getHeight(Heightmap.Types.MOTION_BLOCKING, x, z) - 1;
+            if (level.getBlockState(new net.minecraft.core.BlockPos(x, y, z)).is(material)) count++;
+        }
+        int placed = count;
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Rocks probe " + id + " material=" + rocks.rocks().material() + " count=" + placed), false);
+        return placed;
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan, PortRockPlan rockPlan) {
         String name = StringArgumentType.getString(context, "name");
         Identifier id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
         long seed = LongArgumentType.getLong(context, "seed");
         ServerLevel level;
         try {
-            level = RuntimeAgeBackend.create(context.getSource().getServer(), id, seed, biomePlan, terrain);
+            level = RuntimeAgeBackend.create(context.getSource().getServer(), id, seed, biomePlan, terrain, rockPlan);
         } catch (IllegalArgumentException | IllegalStateException exception) {
             context.getSource().sendFailure(Component.literal(exception.getMessage()));
             return 0;

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeTravel.java

@@ -33,7 +33,9 @@ public final class PortAgeTravel {
     }
 
     private static BlockPos findLanding(ServerLevel target) {
-        if (target.getChunkSource().getGenerator() instanceof net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator noise
+        net.minecraft.world.level.chunk.ChunkGenerator generator = target.getChunkSource().getGenerator();
+        if (generator instanceof PortRockChunkGenerator rocks) generator = rocks.base();
+        if (generator instanceof net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator noise
                 && noise.generatorSettings().value().noiseSettings().equals(target.registryAccess()
                 .lookupOrThrow(Registries.NOISE_SETTINGS)
                 .getOrThrow(net.minecraft.world.level.levelgen.NoiseGeneratorSettings.CAVES)
@@ -56,7 +58,7 @@ public final class PortAgeTravel {
         }
         // A Flat Age has a known surface. Use it directly before a heightmap
         // fallback can place a platform in the air above a low superflat world.
-        FlatLevelGeneratorSettings flatSettings = switch (target.getChunkSource().getGenerator()) {
+        FlatLevelGeneratorSettings flatSettings = switch (generator) {
             case FlatLevelSource flat -> flat.settings();
             case PortFlatChunkGenerator flat -> flat.settings();
             default -> null;

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRandomAgeSelection.java

@@ -0,0 +1,81 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Random;
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+
+/** Seed-frozen terrain and biome choices for a book with no authored symbols. */
+public final class PortRandomAgeSelection {
+    private PortRandomAgeSelection() {}
+
+    public record Selection(PortAgeTerrain terrain, PortBiomePlan biomes) {}
+
+    public static Selection select(MinecraftServer server, long seed) {
+        // Match the 1.21.1 Legacy-rank choices: Standard and Flat are common;
+        // the other terrain families are rarer. The sorted order is deliberate.
+        PortAgeTerrain terrain = weighted(new Random(seed ^ 0x5445525241494E4CL),
+                List.of(PortAgeTerrain.AMPLIFIED, PortAgeTerrain.CAVE, PortAgeTerrain.FLAT,
+                        PortAgeTerrain.ISLAND, PortAgeTerrain.STANDARD, PortAgeTerrain.VOID),
+                new int[]{1, 1, 5, 1, 6, 1});
+        if (terrain == PortAgeTerrain.VOID)
+            return new Selection(terrain, new PortBiomePlan(PortBiomePlan.Distribution.SINGLE,
+                    List.of(Identifier.withDefaultNamespace("the_void"))));
+
+        PortBiomePlan.Distribution distribution = weighted(new Random(seed ^ 0x524956454E435241L),
+                List.of(PortBiomePlan.Distribution.NATIVE, PortBiomePlan.Distribution.SINGLE,
+                        PortBiomePlan.Distribution.MEDIUM, PortBiomePlan.Distribution.TILED,
+                        PortBiomePlan.Distribution.GRID, PortBiomePlan.Distribution.TINY,
+                        PortBiomePlan.Distribution.SMALL, PortBiomePlan.Distribution.LARGE,
+                        PortBiomePlan.Distribution.HUGE),
+                new int[]{3, 3, 3, 1, 1, 1, 1, 1, 1});
+        List<Identifier> eligible = eligibleBiomes(server, terrain);
+        if (eligible.size() < 2 && distribution != PortBiomePlan.Distribution.NATIVE)
+            distribution = PortBiomePlan.Distribution.SINGLE;
+        // 26.3 has no native multi-cave biome source; choose a seeded Cave
+        // biome rather than silently using Lush Caves for every random Age.
+        if (terrain == PortAgeTerrain.CAVE && distribution == PortBiomePlan.Distribution.NATIVE)
+            distribution = PortBiomePlan.Distribution.SINGLE;
+        if (distribution == PortBiomePlan.Distribution.NATIVE)
+            return new Selection(terrain, new PortBiomePlan(distribution, List.of()));
+
+        int count = distribution == PortBiomePlan.Distribution.SINGLE ? 1 : 2;
+        if (count > 1) {
+            Random countRandom = new Random(seed ^ 0x42494F4D45434F55L);
+            while (count < eligible.size() && countRandom.nextInt(3) != 0) count++;
+        }
+        List<Identifier> shuffled = new ArrayList<>(eligible);
+        Collections.shuffle(shuffled, new Random(seed ^ 0x42494F4D45504F4FL));
+        return new Selection(terrain, new PortBiomePlan(distribution, shuffled.subList(0, count)));
+    }
+
+    private static List<Identifier> eligibleBiomes(MinecraftServer server, PortAgeTerrain terrain) {
+        if (terrain == PortAgeTerrain.CAVE) {
+            List<Identifier> caves = server.registryAccess().lookupOrThrow(Registries.BIOME).listElements()
+                    .filter(PortRegistryPages::isCaveBiome)
+                    .map(holder -> holder.key().identifier())
+                    .sorted().toList();
+            return caves.isEmpty() ? List.of(Identifier.withDefaultNamespace("lush_caves")) : caves;
+        }
+        List<Identifier> surface = server.overworld().getChunkSource().getGenerator().getBiomeSource()
+                .possibleBiomes().stream().flatMap(holder -> holder.unwrapKey().stream())
+                .map(key -> key.identifier()).distinct().sorted(Comparator.naturalOrder()).toList();
+        return surface.isEmpty() ? List.of(Identifier.withDefaultNamespace("plains")) : surface;
+    }
+
+    private static <T> T weighted(Random random, List<T> choices, int[] weights) {
+        int total = 0;
+        for (int weight : weights) total += weight;
+        int ticket = random.nextInt(total);
+        for (int index = 0; index < choices.size(); index++) {
+            ticket -= weights[index];
+            if (ticket < 0) return choices.get(index);
+        }
+        throw new IllegalStateException("Random Age ticket was not consumed");
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRockChunkGenerator.java

@@ -0,0 +1,134 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.core.HolderSet;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** Delegates 26.3 terrain generation and adds one Age-scoped Rocks decoration. */
+public final class PortRockChunkGenerator extends ChunkGenerator {
+    public static final MapCodec<PortRockChunkGenerator> CODEC = RecordCodecBuilder.mapCodec(instance -> instance.group(
+            ChunkGenerator.CODEC.fieldOf("base").forGetter(generator -> generator.base),
+            PortRockPlan.CODEC.fieldOf("rocks").forGetter(generator -> generator.rocks),
+            com.mojang.serialization.Codec.LONG.fieldOf("age_seed").forGetter(generator -> generator.ageSeed)
+    ).apply(instance, PortRockChunkGenerator::new));
+
+    private final ChunkGenerator base;
+    private final PortRockPlan rocks;
+    private final long ageSeed;
+
+    public PortRockChunkGenerator(ChunkGenerator base, PortRockPlan rocks, long ageSeed) {
+        super(base.getBiomeSource(), base::getBiomeGenerationSettings);
+        this.base = base;
+        this.rocks = rocks;
+        this.ageSeed = ageSeed;
+    }
+
+    public ChunkGenerator base() { return base; }
+    public PortRockPlan rocks() { return rocks; }
+
+    @Override protected MapCodec<? extends ChunkGenerator> codec() { return CODEC; }
+    @Override public void validate() { base.validate(); }
+    @Override public ChunkPos getOrigin(RandomState random) { return base.getOrigin(random); }
+    @Override public java.util.Optional<Identifier> getTypeNameForDataFixer() { return base.getTypeNameForDataFixer(); }
+    @Override public CompletableFuture<ChunkAccess> createBiomes(RandomState random, Blender blender,
+                                                                  StructureManager structures, ChunkAccess chunk) {
+        return base.createBiomes(random, blender, structures, chunk);
+    }
+    @Override public ChunkGeneratorStructureState createState(HolderLookup<StructureSet> sets,
+                                                               RandomState random, long seed) {
+        return base.createState(sets, random, seed);
+    }
+    @Override public void createStructures(RegistryAccess registries, ChunkGeneratorStructureState state,
+                                           StructureManager structures, ChunkAccess chunk,
+                                           StructureTemplateManager templates, ResourceKey<Level> dimension) {
+        base.createStructures(registries, state, structures, chunk, templates, dimension);
+    }
+    @Override public void createReferences(WorldGenLevel level, StructureManager structures, ChunkAccess chunk) {
+        base.createReferences(level, structures, chunk);
+    }
+    @Override public Pair<BlockPos, Holder<Structure>> findNearestMapStructure(ServerLevel level,
+            HolderSet<Structure> targets, BlockPos origin, int radius, boolean skipKnown) {
+        return base.findNearestMapStructure(level, targets, origin, radius, skipKnown);
+    }
+    @Override public void spawnOriginalMobs(WorldGenRegion level) { base.spawnOriginalMobs(level); }
+    @Override public int getSpawnHeight(LevelHeightAccessor height) { return base.getSpawnHeight(height); }
+    @Override public int getGenDepth() { return base.getGenDepth(); }
+    @Override public int getSeaLevel() { return base.getSeaLevel(); }
+    @Override public int getMinY() { return base.getMinY(); }
+    @Override public CompletableFuture<ChunkAccess> buildTerrain(ChunkAccess chunk, Blender blender,
+            RandomState random, StructureManager structures, BiomeManager biomes,
+            WorldGenRegion carverBiomeRegion, Set<Holder<Biome>> possibleBiomes) {
+        return base.buildTerrain(chunk, blender, random, structures, biomes, carverBiomeRegion, possibleBiomes);
+    }
+    @Override public int getBaseHeight(int x, int z, Heightmap.Types type,
+                                       LevelHeightAccessor height, RandomState random) {
+        return base.getBaseHeight(x, z, type, height, random);
+    }
+    @Override public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor height, RandomState random) {
+        return base.getBaseColumn(x, z, height, random);
+    }
+    @Override public void addDebugScreenInfo(List<String> info, RandomState random,
+                                              BlockPos pos, SamplerContext context) {
+        base.addDebugScreenInfo(info, random, pos, context);
+    }
+    @Override public void refreshFeaturesPerStep() {
+        base.refreshFeaturesPerStep();
+        super.refreshFeaturesPerStep();
+    }
+
+    @Override public void applyBiomeDecoration(WorldGenLevel level, ChunkAccess chunk,
+                                                StructureManager structures) {
+        base.applyBiomeDecoration(level, chunk, structures);
+        ChunkPos chunkPos = chunk.getPos();
+        long seed = ageSeed ^ (long) chunkPos.x() * 341873128712L ^ (long) chunkPos.z() * 132897987541L;
+        RandomSource random = RandomSource.create(seed);
+        if (random.nextInt(5) != 0) return;
+        BlockState material = BuiltInRegistries.BLOCK.getValue(rocks.material()).defaultBlockState();
+        int centerX = chunkPos.getMinBlockX() + 2 + random.nextInt(12);
+        int centerZ = chunkPos.getMinBlockZ() + 2 + random.nextInt(12);
+        for (int dx = -1; dx <= 1; dx++) for (int dz = -1; dz <= 1; dz++) {
+            if (random.nextInt(4) == 0) continue;
+            int x = centerX + dx;
+            int z = centerZ + dz;
+            int y = level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z);
+            BlockPos place = new BlockPos(x, y, z);
+            if (level.getBlockState(place).isAir()
+                    && level.getFluidState(place).isEmpty()
+                    && level.getBlockState(place.below()).isFaceSturdy(level, place.below(), net.minecraft.core.Direction.UP))
+                level.setBlock(place, material, 2);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRockPlan.java

@@ -0,0 +1,12 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.resources.Identifier;
+
+/** First frozen authored feature: one Rocks page with an explicit block material. */
+public record PortRockPlan(Identifier material) {
+    public static final Codec<PortRockPlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Identifier.CODEC.fieldOf("material").forGetter(PortRockPlan::material)
+    ).apply(instance, PortRockPlan::new));
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/RuntimeAgeBackend.java

@@ -57,7 +57,7 @@ public final class RuntimeAgeBackend {
         for (Map.Entry<Identifier, Long> age : index.entries().entrySet()) {
             try {
                 load(server, age.getKey(), age.getValue(), index.biomePlan(age.getKey()),
-                        index.terrain(age.getKey()));
+                        index.terrain(age.getKey()), index.rocks(age.getKey()));
             } catch (RuntimeException exception) {
                 Rivencraft.LOGGER.error("Could not restore Age {}. Its saved index remains intact.", age.getKey(), exception);
             }
@@ -75,12 +75,17 @@ public final class RuntimeAgeBackend {
 
     public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
                                      PortBiomePlan biomePlan, PortAgeTerrain terrain) {
+        return create(server, id, seed, biomePlan, terrain, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks) {
         checkServerThread(server);
         ageName(id);
         AgeLevelIndex index = index(server);
         if (index.contains(id)) throw new IllegalArgumentException("Age already exists: " + id);
-        ServerLevel level = load(server, id, seed, biomePlan, terrain);
-        index.add(id, seed, biomePlan, terrain);
+        ServerLevel level = load(server, id, seed, biomePlan, terrain, rocks);
+        index.add(id, seed, biomePlan, terrain, rocks);
         // A newly bound book may be used immediately. Persist its Age identity
         // before publishing the catalog so a later crash cannot leave that
         // book pointing at a world omitted from the on-disk index.
@@ -100,7 +105,8 @@ public final class RuntimeAgeBackend {
     public static ServerLevel reload(MinecraftServer server, Identifier id) {
         checkServerThread(server);
         long seed = requireSeed(server, id);
-        ServerLevel level = load(server, id, seed, index(server).biomePlan(id), index(server).terrain(id));
+        ServerLevel level = load(server, id, seed, index(server).biomePlan(id), index(server).terrain(id),
+                index(server).rocks(id));
         AgeCatalogSync.onCatalogChanged(server);
         return level;
     }
@@ -112,18 +118,19 @@ public final class RuntimeAgeBackend {
         long previousSeed = requireSeed(server, id);
         PortBiomePlan biomePlan = index.biomePlan(id);
         PortAgeTerrain terrain = index.terrain(id);
+        PortRockPlan rocks = index.rocks(id);
         if (previousSeed == seed) return;
         boolean loaded = server.getLevel(dimensionKey(id)) != null;
         if (loaded) unloadLoaded(server, id);
         try {
-            if (loaded) load(server, id, seed, biomePlan, terrain);
+            if (loaded) load(server, id, seed, biomePlan, terrain, rocks);
             index.reseed(id, seed);
             server.overworld().getDataStorage().saveAndJoin();
             if (loaded) AgeCatalogSync.onCatalogChanged(server);
         } catch (RuntimeException exception) {
             if (loaded) {
                 try {
-                    load(server, id, previousSeed, biomePlan, terrain);
+                    load(server, id, previousSeed, biomePlan, terrain, rocks);
                     AgeCatalogSync.onCatalogChanged(server);
                 } catch (RuntimeException rollbackFailure) {
                     exception.addSuppressed(rollbackFailure);
@@ -141,6 +148,7 @@ public final class RuntimeAgeBackend {
         long seed = requireSeed(server, id);
         PortBiomePlan biomePlan = index.biomePlan(id);
         PortAgeTerrain terrain = index.terrain(id);
+        PortRockPlan rocks = index.rocks(id);
         boolean loaded = server.getLevel(dimensionKey(id)) != null;
         ArchivePaths paths = archivePaths(server, name);
         if (loaded) unloadLoaded(server, id);
@@ -159,14 +167,14 @@ public final class RuntimeAgeBackend {
             }
         } catch (IOException | RuntimeException exception) {
             try {
-                index.restoreAfterFailedRetirement(id, seed, biomePlan, terrain);
+                index.restoreAfterFailedRetirement(id, seed, biomePlan, terrain, rocks);
                 server.overworld().getDataStorage().saveAndJoin();
             } catch (RuntimeException rollbackFailure) {
                 exception.addSuppressed(rollbackFailure);
             }
             if (loaded) {
                 try {
-                    load(server, id, seed, biomePlan, terrain);
+                    load(server, id, seed, biomePlan, terrain, rocks);
                 } catch (RuntimeException rollbackFailure) {
                     exception.addSuppressed(rollbackFailure);
                 }
@@ -282,7 +290,7 @@ public final class RuntimeAgeBackend {
     }
 
     private static ServerLevel load(MinecraftServer server, Identifier id, long seed,
-                                    PortBiomePlan biomePlan, PortAgeTerrain terrain) {
+                                    PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks) {
         ResourceKey<Level> key = ResourceKey.create(Registries.DIMENSION, id);
         if (server.getLevel(key) != null) throw new IllegalArgumentException("Level already loaded: " + id);
 
@@ -353,6 +361,7 @@ public final class RuntimeAgeBackend {
             };
             generator = new NoiseBasedChunkGenerator(source, settings);
         }
+        if (rocks != null) generator = new PortRockChunkGenerator(generator, rocks, seed);
         LevelStem stem = new LevelStem(overworldStem.type(), generator, OptionalLong.of(seed));
         long biomeZoomSeed = BiomeManager.obfuscateSeed(server.getWorldGenSettings().options().seed());
         ServerLevel level = new ServerLevel(server, server.executor, server.storageSource,

ports/mc263/src/main/java/net/dnorberg/rivencraft/network/PortBookNetworking.java

@@ -2,7 +2,9 @@ package net.dnorberg.rivencraft.network;
 
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.age.PortAgeTravel;
+import net.dnorberg.rivencraft.age.PortAgeTerrain;
 import net.dnorberg.rivencraft.age.RuntimeAgeBackend;
+import net.dnorberg.rivencraft.age.PortRandomAgeSelection;
 import net.dnorberg.rivencraft.item.LinkBookTarget;
 import net.dnorberg.rivencraft.item.LinkProperties;
 import net.dnorberg.rivencraft.item.LinkingBookItem;
@@ -125,8 +127,15 @@ public final class PortBookNetworking {
             id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
         }
         try {
-            RuntimeAgeBackend.create(server, id, player.getRandom().nextLong(), biomePlan,
-                    PortAuthoredWriting.terrain(pages));
+            long seed = player.getRandom().nextLong();
+            PortAgeTerrain terrain = PortAuthoredWriting.terrain(pages);
+            if (pages.isEmpty()) {
+                PortRandomAgeSelection.Selection random = PortRandomAgeSelection.select(server, seed);
+                terrain = random.terrain();
+                biomePlan = random.biomes();
+            }
+            RuntimeAgeBackend.create(server, id, seed, biomePlan, terrain,
+                    PortAuthoredWriting.rockPlan(pages));
         } catch (IllegalArgumentException | IllegalStateException exception) {
             player.sendOverlayMessage(Component.literal("Age creation failed: " + exception.getMessage()));
             return null;

ports/mc263/src/main/java/net/dnorberg/rivencraft/registry/PortChunkGenerators.java

@@ -3,6 +3,7 @@ package net.dnorberg.rivencraft.registry;
 import com.mojang.serialization.MapCodec;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.age.PortFlatChunkGenerator;
+import net.dnorberg.rivencraft.age.PortRockChunkGenerator;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.neoforged.bus.api.IEventBus;
@@ -15,6 +16,7 @@ public final class PortChunkGenerators {
 
     static {
         GENERATORS.register("age_flat", () -> PortFlatChunkGenerator.CODEC);
+        GENERATORS.register("age_rocks", () -> PortRockChunkGenerator.CODEC);
     }
 
     private PortChunkGenerators() {}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortAuthoredWriting.java

@@ -4,6 +4,7 @@ import java.util.List;
 import java.util.ArrayList;
 import net.dnorberg.rivencraft.age.PortBiomePlan;
 import net.dnorberg.rivencraft.age.PortAgeTerrain;
+import net.dnorberg.rivencraft.age.PortRockPlan;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.minecraft.core.HolderLookup;
 import net.minecraft.core.registries.Registries;
@@ -25,6 +26,8 @@ public final class PortAuthoredWriting {
             Rivencraft.MOD_ID, "terrain/void");
     private static final Identifier CAVE_TERRAIN = Identifier.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "terrain/cave");
+    private static final Identifier ROCKS = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "feature/rocks");
 
     private PortAuthoredWriting() {}
 
@@ -33,11 +36,19 @@ public final class PortAuthoredWriting {
         boolean terrain = false;
         int biomes = 0;
         int controllers = 0;
+        boolean material = false;
+        boolean rocks = false;
         for (Identifier page : pages) {
             if (isTerrain(page) && !terrain) {
                 terrain = true;
             } else if (controller(page) != null && controllers++ == 0) {
                 // An explicit controller needs an authored pool.
+            } else if (isBlockPage(page) && !material && !rocks
+                    && PortSymbolPages.find(page) != null
+                    && PortSymbolPages.find(page).category().equals("rivencraft:block")) {
+                material = true;
+            } else if (page.equals(ROCKS) && material && !rocks) {
+                rocks = true;
             } else if (page.getNamespace().equals(Rivencraft.MOD_ID)
                     && page.getPath().startsWith("biome/") && biomes < MAX_AUTHORED_BIOMES
                     && PortSymbolPages.find(page) != null
@@ -46,6 +57,7 @@ public final class PortAuthoredWriting {
                 biomes++;
             } else return false;
         }
+        if (material != rocks || rocks && (pages.contains(CAVE_TERRAIN) || pages.contains(VOID_TERRAIN))) return false;
         if (controllers != 0) {
             PortBiomePlan.Distribution distribution = pages.stream().map(PortAuthoredWriting::controller)
                     .filter(value -> value != null).findFirst().orElseThrow();
@@ -65,6 +77,10 @@ public final class PortAuthoredWriting {
                 || page.equals(VOID_TERRAIN) || page.equals(CAVE_TERRAIN);
     }
 
+    private static boolean isBlockPage(Identifier page) {
+        return page.getNamespace().equals(Rivencraft.MOD_ID) && page.getPath().startsWith("block/");
+    }
+
     private static PortBiomePlan.Distribution controller(Identifier page) {
         if (!page.getNamespace().equals(Rivencraft.MOD_ID)) return null;
         return switch (page.getPath()) {
@@ -91,6 +107,13 @@ public final class PortAuthoredWriting {
         return PortAgeTerrain.STANDARD;
     }
 
+    public static PortRockPlan rockPlan(List<Identifier> pages) {
+        if (!supports(pages)) throw new IllegalArgumentException("Unsupported authored Age pages");
+        return pages.contains(ROCKS) ? new PortRockPlan(pages.stream()
+                .filter(PortAuthoredWriting::isBlockPage).map(PortRegistryPages::blockId)
+                .findFirst().orElseThrow()) : null;
+    }
+
     /** Resolves all authored biomes from the active registry before creating a level. */
     public static PortBiomePlan biomePlan(List<Identifier> pages, HolderLookup.Provider registries) {
         if (!supports(pages)) throw new IllegalArgumentException(
@@ -99,7 +122,7 @@ public final class PortAuthoredWriting {
         PortBiomePlan.Distribution distribution = null;
         boolean caveTerrain = pages.contains(CAVE_TERRAIN);
         for (Identifier page : pages) {
-            if (isTerrain(page)) continue;
+            if (isTerrain(page) || page.equals(ROCKS) || isBlockPage(page)) continue;
             PortBiomePlan.Distribution selected = controller(page);
             if (selected != null) { distribution = selected; continue; }
             Identifier biome = PortRegistryPages.biomeId(page);