Enforce generation write radii before feature mutations

benchmarks/rust-feature-region-write-zone-2026-10-06/scoped-parity.json

@@ -0,0 +1,213 @@
+{
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+  "worldgen_random_modes": [
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+    "crates/horizon-world/src/worldgen/end_podium.rs": "8f6d0d6d60ff0fde63de5781e867239db321f82cf12639f0537d410a3731ee1d",
+    "crates/horizon-world/src/worldgen/feature.rs": "40500af71ee6628dfb27518262d99f08d0383ae6c7b9397452feef0c213eadd9",
+    "crates/horizon-world/src/worldgen/feature_catalog.rs": "efc7b17b227e71622ef34108be9abd010f5675b68ea0409fcab82581d9aab88a",
+    "crates/horizon-world/src/worldgen/feature_graph.rs": "da132fca9fdafb0d89a917d5f4b68c60b70fb33cadf948a107da0e35d83dcd91",
+    "crates/horizon-world/src/worldgen/feature_region.rs": "7677027594ed3df5e538402d5a3ba9276b67b56490463ca2686bfa418d02bd24",
+    "crates/horizon-world/src/worldgen/feature_sort.rs": "3488a093dfe1321aaa29d8a30cfb115d8e666a81bf195514e87b170de626835c",
+    "crates/horizon-world/src/worldgen/fluid_predicate.rs": "64197c9e63bebf1ce04bc280bfe980bb6c1b9aa887ca5cded904aeb0d9ae6c46",
+    "crates/horizon-world/src/worldgen/height_provider.rs": "368d4dc119854742a045c4a717679c921456da681fc5f71aa9b37102d6f33b47",
+    "crates/horizon-world/src/worldgen/material_condition/codec.rs": "09b909bc384472f76d163c8069ec6b507c7d5c6a028a36d5e0e3df20deff7b3b",
+    "crates/horizon-world/src/worldgen/material_condition/density.rs": "df9d0761e978e5010663ae8b44f2d6c1ecb4907331e333bdb6a2b487c1e107de",
+    "crates/horizon-world/src/worldgen/material_condition/library.rs": "a55534c5da97575a819af5a7dc0dbec9069993fa8b2619c6c9d5576946e683fa",
+    "crates/horizon-world/src/worldgen/material_condition/noise.rs": "ffb59cc6be2275d7a5621bf7d768527e74a8326ed7ad78618746711540921675",
+    "crates/horizon-world/src/worldgen/material_condition/rule.rs": "fed643352efbcb1f68f29b6241896617db889fc7c577a6247564e01922fec1fe",
+    "crates/horizon-world/src/worldgen/material_condition.rs": "d638dcb8cbcb5da20b3cb29602b0ae6a86c4fdf9d8c0fb725de8ec5fc108717e",
+    "crates/horizon-world/src/worldgen/material_extensions.rs": "ab806eb679d5116e1aebb64fca70e1499ae71f83c9507a8cb4c3201c2b1bf037",
+    "crates/horizon-world/src/worldgen/material_stage.rs": "698cbc786eff13c246e2bc2ea062401918cd4265899fbc3d53abc87e45a8e7a1",
+    "crates/horizon-world/src/worldgen/material_surface.rs": "5d37b90099df3d6da0845dab164e71469fb287019c2ee74bc6714f3b9d6d6d5b",
+    "crates/horizon-world/src/worldgen/ore_feature.rs": "83b89fd3be691c5412c0215b6abefdcaa44119a05aa41217e061970eb7e12ebd",
+    "crates/horizon-world/src/worldgen/placement/chain.rs": "9218399b4d3757f7bbc550d7729a7201f32a1c83a7030865e0c12aab8a80d116",
+    "crates/horizon-world/src/worldgen/placement/context.rs": "a278304795136677ad4b4933ea50c972b9729a1c671c03fa309c193e224b1fd6",
+    "crates/horizon-world/src/worldgen/placement/layer.rs": "a0f5ca776f33f9d4f72b8fdcd163426152e5e43cb4a7572fc1d4fc57bf965de1",
+    "crates/horizon-world/src/worldgen/placement.rs": "b0397e5818fae84358546193a95f84bcb0b5bffafce909e6fcb3386179ee8023",
+    "crates/horizon-world/src/worldgen/replace_blobs.rs": "bf3377d86d2570cd15288ba69dde64a2cf67c5bcbb9a31d0c23421964af74afa",
+    "crates/horizon-world/src/worldgen/router.rs": "2cee7cf15a0d2ada12be6b39d83e78177fd3033922e4f4cce87a64073cec2847",
+    "crates/horizon-world/src/worldgen/rule_test.rs": "d1662ec492489ebaa4b87e20f9a8c809dcf3a223a151211bd65ec241a63692fc",
+    "crates/horizon-world/src/worldgen/settings.rs": "a8fe87752e1982ef11cb67f8d80d8e3428b2c27db178044cb425ba803e689e59",
+    "crates/horizon-world/src/worldgen/simple_block.rs": "9ba1a88d5db4925f8c37366557887f776c805f9a6444781615b5dbaff52e92a4",
+    "crates/horizon-world/src/worldgen/snow_freeze.rs": "9040be3d5c7f8f0fd812d2df45e154bf8a9eeef038530b83fa4159d246eac35f",
+    "crates/horizon-world/src/worldgen/speleothem.rs": "c71651c1c97818a8a85863e14414d6139ea3bdeb897fa422043bcc1499d99aae",
+    "crates/horizon-world/src/worldgen/spike.rs": "eacf0d9d3d2bc3d4bcf62bc87555f90031138236a5bfef0eb5270204f7c2a4fc",
+    "crates/horizon-world/src/worldgen/spring.rs": "830849e9b89fcdf09e9b06fbefdcdebe3c8c3f82804f60b8bd5de04ba303cb62",
+    "crates/horizon-world/src/worldgen/state_provider/catalog.rs": "c8687e15a4887a9200c8d365857d801efaa8f90e669eee3e600a1db4905119eb",
+    "crates/horizon-world/src/worldgen/state_provider/noise.rs": "7ee369c2a032e5620cb9bdf9ee7adad1f70870fb0a27efb7b7c514d92f83491f",
+    "crates/horizon-world/src/worldgen/state_provider/properties.rs": "9909139aaca1dc4f743957257fadaa9d423d21fa401fa9abc050505f79365139",
+    "crates/horizon-world/src/worldgen/state_provider.rs": "be29ada818826a90afe01ab60916360fdfc4cbde5af15c9359cd56b1f1f7b156",
+    "crates/horizon-world/src/worldgen/tags.rs": "d35ded93fe6e95ea045cadcf4925e656dc34ef832b742179b9ad0cc49f902f31",
+    "crates/horizon-world/src/worldgen/terrain.rs": "b8fb9fb80a66a851d916f07f15df1a40b6cc95b49e71aaec4d4b4107f13d9f9f",
+    "crates/horizon-world/src/worldgen/underwater_magma.rs": "7317e40af5ee5a9780f90ce358fa5d3e7f5b3d513b731df6ff97754d9c2a0154",
+    "crates/horizon-world/src/worldgen/value_provider.rs": "3358b563db8cb0bc8a9cfbbe2b8b3e70941cd2d37a0b519fbb6545f8d0dcbb69",
+    "crates/horizon-world/src/worldgen/vines.rs": "ee9b79b65012bd86a838241d2ef708680f7fe8eafc8aa656dae9cf2abf3c6418",
+    "crates/horizon-world/src/worldgen/weighted.rs": "839840aae25302933bbd97a81a2336330e2d03a0ad1684e1e16ac769ed408e6b",
+    "crates/horizon-world/src/worldgen/write_zone.rs": "1d79a7fdb5dd18b0b59079cb2dc74682ba7af2a650c8efff027cfa530eee7bf9",
+    "crates/horizon-world/src/worldgen.rs": "e8e9f099ee1fcec8eedce31805d676d3f89c18e84f494a147ffcbfee23d3d54f",
+    "crates/horizon-world/examples/feature_region_fixture.rs": "969ea5c21d7a2be24e0804185fa5557196c809dad961602f23cecdbfea635eba"
+  },
+  "fixtures_sha256": {
+    ".local/rust-feature-region-parity/zones.json": "1864a9cdc17816c12fc5e92cd6abd32e45d67615075c52e928872e041d84244c",
+    ".local/rust-feature-region-parity/inputs.txt": "eb98b59c22ea7c90d657a91698b8f73dcbe4b510a72f3eefae3e982bb9c2086f",
+    ".local/rust-feature-region-parity/tags.json": "36975358262568f32bf84778d63d9989a36e7394ed4796d70a34809a8f4a64f0",
+    ".local/rust-feature-region-parity/fluid-tags.json": "f1e5eb6d22ea7effbb118a2282709cfdeef1bfae4516b775a55ad7a4df29d7d0",
+    ".local/rust-feature-region-parity/facts-client.json": "1d24883ee807b0b71473f0bbf8ed548ddaf712148caeb3fcc7aa13ab973a97b0",
+    ".local/rust-feature-region-parity/facts-server.json": "1d24883ee807b0b71473f0bbf8ed548ddaf712148caeb3fcc7aa13ab973a97b0"
+  },
+  "rust_output_sha256": "522b3abf0ac74366c9739d0d0977707b61e25ac73a98a620d5e2fb71bd8e32b9",
+  "references": [
+    {
+      "side": "client",
+      "jar_sha256": "4508d006323f24fa02876310c192d739af56516eb259000ac50f0909a68c9a2d",
+      "output_sha256": "522b3abf0ac74366c9739d0d0977707b61e25ac73a98a620d5e2fb71bd8e32b9",
+      "matched_output_lines": 29231123
+    },
+    {
+      "side": "server",
+      "jar_sha256": "a362163eec5d1612d520772bc16e5b39c09e3b234fdc045f56bf544284ee8ae6",
+      "output_sha256": "522b3abf0ac74366c9739d0d0977707b61e25ac73a98a620d5e2fb71bd8e32b9",
+      "matched_output_lines": 29231123
+    }
+  ],
+  "scope": "Native FeaturePlacer and three basic block-writing features, a composed sequence of four configured fill layers, single-block replacements, scattered ore and water springs share a world proxy backed by nine actual ProtoChunks. Configured water, horizontal logs, air, out-of-height fills and ore/replacement rules test graph-to-region binding. Initial two-layer stone/dirt terrain, both pre-light heightmap groups, count/square/heightmap/layered modifier chains, repeated placements, direct and WorldgenRandom-wrapped random streams, missing-neighbor errors, rejected writes and injected partial failures are compared. Final complete raw sections, heightmap presence and packed words are compared alongside ordered feature writes, update flags, explicit height queries and subsequent random draws. Rust uses resident registry-backed chunks, lazy heightmap priming and a caller-supplied write callback; imported air/fluid facts and bundled block tags bind independently across authenticated JARs. The proxy supplies storage mutation and actual native default scheduleTick/createTick methods routed through WorldGenTickAccess into each ProtoChunk. Separate block/fluid queues, first-request deduplication, nondefault-state block identity, shared tick-order advancement on duplicates and missing-chunk errors, out-of-height requests and wrapped clock values are compared, including saved queue order and priorities. Active and inactive End podiums additionally exercise native WorldGenRegion.destroyBlock through a subclass transport overriding only block reads and writes; air short-circuit, rejected replacements and write failures retain the generation-time semantics. All block states are also written into resident chunks, queried through feature access, cleared and queried again; contained fluid identity/amount/falling/source/full flags, water-tag membership and every bundled block tag plus an absent tag are compared. Negative coordinates, chunk edges, outside-height and absent chunks are covered. Block/fluid query bindings are an immutable registry-checked shared snapshot. The native horizontal write-zone predicate is compared separately across chunk/block coordinates, negative radii and wrapped subtraction/absolute-value extremes, and gates feature callbacks in selected fixtures. Actual WorldGenRegion construction, upgrading-world vertical write restrictions, POIs, block entities, postprocessing execution, lighting, block/fluid tick execution, complete feature registries and complete world generation remain outside this comparison."
+}

crates/horizon-world/examples/feature_region_fixture.rs

@@ -7,6 +7,7 @@ use horizon_world::worldgen::{
     feature_region::{RegionError, TerrainFeatureAccess, TerrainRegion},
     placement::{FeaturePlacer, PlacementContext, PlacementModifier},
     terrain::TerrainError,
+    write_zone::GenerationWriteZone,
 };
 // Feature chains against a resident multi-chunk region.
 use horizon_core::position::ChunkPos;
@@ -214,6 +215,12 @@ fn run(
                     Ok(result)
                 };
                 let mut world = TerrainFeatureAccess::new(&mut region, write);
+                if let Some(zone) = f["write_zone"].as_array() {
+                    world = world.with_write_zone(GenerationWriteZone::new(
+                        ChunkPos::new(n(&zone[0]), n(&zone[1])),
+                        n(&zone[2]),
+                    ));
+                }
                 placer.place_with_context(
                     &modifiers,
                     &mut world,
@@ -432,6 +439,17 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .chain(std::iter::once("horizon:absent".into()))
         .collect();
     let mut out = io::BufWriter::new(fs::File::create(dir.join("rust.txt"))?);
+    let zones: Value = serde_json::from_str(&fs::read_to_string(dir.join("zones.json"))?)?;
+    for row in zones.as_array().unwrap() {
+        let zone = GenerationWriteZone::new(ChunkPos::new(n(&row[0]), n(&row[1])), n(&row[2]));
+        let (x, z) = (n(&row[3]), n(&row[4]));
+        writeln!(
+            out,
+            "zone {} {}",
+            zone.contains_chunk(ChunkPos::new(x, z)),
+            zone.contains_block(horizon_core::position::BlockPos::new(x, i32::MIN, z))
+        )?;
+    }
     for line in fs::read_to_string(dir.join("inputs.txt"))?.lines() {
         fixture(
             &serde_json::from_str(line)?,

crates/horizon-world/src/worldgen.rs

@@ -56,6 +56,7 @@ pub mod underwater_magma;
 pub mod value_provider;
 pub mod vines;
 pub mod weighted;
+pub mod write_zone;
 use horizon_core::noise::{NoiseBuildError, NormalNoise, Normalization};
 use serde_json::value::RawValue;
 use std::collections::BTreeMap;

crates/horizon-world/src/worldgen/feature_region.rs

@@ -377,10 +377,39 @@ impl<B: TerrainBlockStates> PlacementContext for TerrainRegion<'_, B> {
 pub struct TerrainFeatureAccess<'a, 'r, B: TerrainBlockStates, F> {
     region: &'a mut TerrainRegion<'r, B>,
     write: F,
+    write_zone: Option<super::write_zone::GenerationWriteZone>,
 }
 impl<'a, 'r, B: TerrainBlockStates, F> TerrainFeatureAccess<'a, 'r, B, F> {
     pub fn new(region: &'a mut TerrainRegion<'r, B>, write: F) -> Self {
-        Self { region, write }
+        Self {
+            region,
+            write,
+            write_zone: None,
+        }
+    }
+    /// Apply the horizontal write radius before invoking mutation policy/effects.
+    /// Upgrading-world vertical restrictions remain the owning world's policy.
+    pub fn with_write_zone(mut self, zone: super::write_zone::GenerationWriteZone) -> Self {
+        self.write_zone = Some(zone);
+        self
+    }
+}
+impl<'r, B: TerrainBlockStates, F> TerrainFeatureAccess<'_, 'r, B, F>
+where
+    F: FnMut(&mut TerrainRegion<'r, B>, [i32; 3], BlockStateId, i32) -> Result<bool, RegionError>,
+{
+    fn write_block(
+        &mut self,
+        position: [i32; 3],
+        state: BlockStateId,
+        flags: i32,
+    ) -> Result<bool, RegionError> {
+        if self.write_zone.is_some_and(|zone| {
+            !zone.contains_block(BlockPos::new(position[0], position[1], position[2]))
+        }) {
+            return Ok(false);
+        }
+        (self.write)(self.region, position, state, flags)
     }
 }
 impl<'r, B: TerrainBlockStates, F> PlacementContext for TerrainFeatureAccess<'_, 'r, B, F>
@@ -403,7 +432,7 @@ where
             .registry()
             .default_state("minecraft:air")
             .expect("validated air state");
-        (self.write)(self.region, position, air, 3).map_err(Into::into)
+        self.write_block(position, air, 3).map_err(Into::into)
     }
 
     fn fluid_state(
@@ -480,6 +509,6 @@ where
         state: BlockStateId,
         flags: i32,
     ) -> Result<bool, Self::Error> {
-        (self.write)(self.region, position, state, flags)
+        self.write_block(position, state, flags)
     }
 }

crates/horizon-world/src/worldgen/write_zone.rs

@@ -0,0 +1,22 @@
+//! Horizontal generation write-zone predicate from the pinned chunk step.
+use horizon_core::position::{BlockPos, ChunkPos};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct GenerationWriteZone {
+    center: ChunkPos,
+    radius: i32,
+}
+impl GenerationWriteZone {
+    /// The caller supplies the center chunk and the generation step's write
+    /// radius. Negative radii and wrapped coordinates retain Java semantics.
+    pub fn new(center: ChunkPos, radius: i32) -> Self {
+        Self { center, radius }
+    }
+    pub fn contains_chunk(self, chunk: ChunkPos) -> bool {
+        self.center.x.wrapping_sub(chunk.x).wrapping_abs() <= self.radius
+            && self.center.z.wrapping_sub(chunk.z).wrapping_abs() <= self.radius
+    }
+    pub fn contains_block(self, position: BlockPos) -> bool {
+        self.contains_chunk(position.chunk())
+    }
+}

docs/rust-parity.md

@@ -797,3 +797,19 @@ to the existing chunk fixture. Final sections, heightmaps, ticks, tag/fluid prob
 rejected writes and partial failures still agree. Workspace tests, all-target
 Clippy and all 149 Python tests pass. Write-zone policy, POIs, block entities,
 postprocessing execution, lighting and live-world effects remain pending.
+
+## Generation write radii
+
+Feature access can now apply the generation step's horizontal write radius before
+calling the mutation policy. Ordinary writes and destruction share the guard;
+queries and tick scheduling retain their independent routing. The predicate uses
+Java wrapping subtraction and absolute value, including integer-minimum cases.
+
+The [write-zone comparison](../benchmarks/rust-feature-region-write-zone-2026-10-06/scoped-parity.json)
+matches **29,231,123 lines per reference JAR**. It adds **20,125 direct zone cases**
+for both chunk and block coordinates, then exercises unrestricted, zero-radius,
+shifted-center and negative-radius policies across the 192 resident fixtures.
+Vanilla's actual public/private write-zone methods provide the reference. Workspace
+tests, all-target Clippy and both focused fixture tests pass. The owning world
+still supplies generation-step metadata and upgrading-world vertical restrictions;
+full WorldGenRegion effects remain pending.

mods/horizon/src/test/java/dev/horizonlab/parity/VanillaFeatureRegionOracle.java

@@ -38,6 +38,10 @@ public final class VanillaFeatureRegionOracle {
         var value=(NativeDestruction)((sun.misc.Unsafe)field.get(null)).allocateInstance(NativeDestruction.class);value.world=world;return value;
     }
 
+    private static void setWriteZone(NativeDestruction world,int x,int z,int radius)throws ReflectiveOperationException {
+        String[] names={"centerChunkX","centerChunkZ","writeRadius"};int[] values={x,z,radius};
+        for(int i=0;i<names.length;i++){var field=net.minecraft.server.level.WorldGenRegion.class.getDeclaredField(names[i]);field.setAccessible(true);field.setInt(world,values[i]);}
+    }
     private static ProtoChunk chunk(Map<ChunkPos,ProtoChunk> chunks,int x,int z) {
         var chunk=chunks.get(new ChunkPos(x>>4,z>>4));if(chunk==null)throw new IllegalArgumentException("missing region chunk");return chunk;
     }
@@ -86,6 +90,12 @@ public final class VanillaFeatureRegionOracle {
         }});
         var fluids=new Fluid[]{Fluids.EMPTY,Fluids.FLOWING_WATER,Fluids.WATER,Fluids.FLOWING_LAVA,Fluids.LAVA};
         try(var out=new PrintWriter(Files.newBufferedWriter(dir.resolve(args[0]+".txt"),StandardCharsets.UTF_8))) {
+            var zoneWorld=destruction(null);
+            var chunkZone=net.minecraft.server.level.WorldGenRegion.class.getDeclaredMethod("isWithinWriteZone",int.class,int.class);chunkZone.setAccessible(true);
+            for(var value:JsonParser.parseString(Files.readString(dir.resolve("zones.json"))).getAsJsonArray()) {
+                var row=value.getAsJsonArray();setWriteZone(zoneWorld,row.get(0).getAsInt(),row.get(1).getAsInt(),row.get(2).getAsInt());
+                int x=row.get(3).getAsInt(),z=row.get(4).getAsInt();out.println("zone "+chunkZone.invoke(zoneWorld,x,z)+" "+zoneWorld.isWithinWriteZone(new BlockPos(x,Integer.MIN_VALUE,z)));
+            }
             for(var line:Files.readAllLines(dir.resolve("inputs.txt"))) {
                 var f=JsonParser.parseString(line).getAsJsonObject();long seed=f.get("seed").getAsLong();
                 var features=new ArrayList<Feature>();
@@ -128,6 +138,7 @@ public final class VanillaFeatureRegionOracle {
                     case "getBlockState"->{var p=(BlockPos)values[0];yield chunk(chunks,p.getX(),p.getZ()).getBlockState(p);}
                     case "setBlock"->{
                         var p=(BlockPos)values[0];var state=(BlockState)values[1];int flags=(Integer)values[2];
+                        if(!f.get("write_zone").isJsonNull()&&!destroyer[0].isWithinWriteZone(p))yield false;
                         out.println("write "+p.getX()+" "+p.getY()+" "+p.getZ()+" "+Block.getId(state)+" "+flags);
                         int call=calls[0]++;if(call==fail)throw new IllegalArgumentException("injected write failure");
                         boolean result=reject==0||call%reject!=0;
@@ -137,6 +148,7 @@ public final class VanillaFeatureRegionOracle {
                     default->throw new AssertionError("unexpected world method "+method);
                 });
                 destroyer[0]=destruction(world);
+                if(!f.get("write_zone").isJsonNull()){var zone=f.getAsJsonArray("write_zone");setWriteZone(destroyer[0],zone.get(0).getAsInt(),zone.get(1).getAsInt(),zone.get(2).getAsInt());}
                 var modifiers=new ArrayList<PlacementModifier>();for(var value:f.getAsJsonArray("placement"))modifiers.add(PlacementModifier.CODEC.parse(JsonOps.INSTANCE,value).getOrThrow());
                 var placer=new FeaturePlacer(world,generator);
                 for(int repeat=0;repeat<2;repeat++) {

tests/test_feature_region_parity.py

@@ -14,6 +14,7 @@ class FeatureRegionCorpusTests(unittest.TestCase):
         self.assertTrue(all(len(f['tick_commands']) == 77 for f in fixtures))
         self.assertTrue(all(any(v['type'] == 'spring_feature' for v in f['features']) for f in fixtures))
         self.assertTrue(all([v['active'] for v in f['features'] if v['type'] == 'end_podium'] == [False, True] for f in fixtures))
+        self.assertEqual({None if f['write_zone'] is None else tuple(f['write_zone']) for f in fixtures}, {None, (0, 0, 0), (1, 1, 0), (-1, -1, 1), (0, 0, -1)})
         self.assertEqual({f['worldgen'] for f in fixtures}, {False, True})
         self.assertEqual({f['legacy'] for f in fixtures}, {False, True})
         self.assertEqual({f['stage'] for f in fixtures}, {'empty', 'terrain'})

tools/test_feature_region_parity.py

@@ -49,7 +49,7 @@ def corpus(facts):
                     for reject in [0,3]:
                         for placement in chains:
                             for worldgen in [False,True]:
-                                yield {'probe_states':list(range(fixture_index,len(facts['states']),192)),'worldgen':worldgen,'legacy':legacy,'seed':seed,'stage':stage,'fail':fail,'reject':reject,'placement':placement,'features':features,'tick_commands':ticks,'game_time':9223372036854775807 if worldgen else -9223372036854775808,'tick_order':9223372036854775803 if legacy else -9223372036854775808}
+                                yield {'write_zone':[None,[0,0,0],[1,1,0],[-1,-1,1],[0,0,-1]][fixture_index%5],'probe_states':list(range(fixture_index,len(facts['states']),192)),'worldgen':worldgen,'legacy':legacy,'seed':seed,'stage':stage,'fail':fail,'reject':reject,'placement':placement,'features':features,'tick_commands':ticks,'game_time':9223372036854775807 if worldgen else -9223372036854775808,'tick_order':9223372036854775803 if legacy else -9223372036854775808}
                                 fixture_index+=1
 
 
@@ -91,7 +91,16 @@ def main():
     fixtures=list(corpus(facts));inputs=build/"inputs.txt"
     inputs.write_text("".join(json.dumps(value,separators=(",",":"))+"\n" for value in fixtures),encoding="utf-8")
     (build/"tags.json").write_text(json.dumps(tags,separators=(",",":")),encoding="utf-8")
-    fixture_paths=[inputs,build/"tags.json",build/"fluid-tags.json",build/"facts-client.json",build/"facts-server.json"]
+    edges=[-2147483648,-2147483647,-134217729,-134217728,-17,-16,-1,0,1,15,16,134217727,134217728,2147483646,2147483647]
+    zones=[]
+    for cx,cz in [(0,0),(-1,1),(-2147483648,-2147483648),(2147483647,2147483647),(134217727,-134217728)]:
+        for radius in [-2147483648,-2,-1,0,1,2,7,134217728,2147483647]:
+            for x in edges:
+                for z in edges:zones.append([cx,cz,radius,x,z])
+    rng=random.Random(0x574f524c445a4f4e45)
+    for _ in range(10000):zones.append([rng.randrange(-2**31,2**31) for _ in range(5)])
+    zone_inputs=build/'zones.json';zone_inputs.write_text(json.dumps(zones,separators=(',',':')))
+    fixture_paths=[zone_inputs,inputs,build/"tags.json",build/"fluid-tags.json",build/"facts-client.json",build/"facts-server.json"]
     tested_fixtures=base.source_hashes(fixture_paths)
     run(["cargo","build","--release","-p","horizon-world","--example","feature_region_fixture"],"compile-rust")
     metadata=json.loads(subprocess.check_output(["cargo","metadata","--no-deps","--format-version","1"],cwd=lab.ROOT,text=True))
@@ -106,9 +115,9 @@ def main():
     base.ensure_sources_unchanged(sources,tested_sources);base.ensure_sources_unchanged(fixture_paths,tested_fixtures)
     report={"schema":1,"minecraft":lock["minecraft"]["version"],"manifest_sha1":lock["minecraft"]["manifest_sha1"],"platform":platform.platform(),
             "java":subprocess.check_output(["java","--version"],text=True).splitlines()[0],"rustc":subprocess.check_output(["rustc","--version"],text=True).strip(),
-            "block_states":len(facts["states"]),"direct_state_probes":sum(len(f["probe_states"]) for f in fixtures),"block_tag_files":len(tags),"fixtures":len(fixtures),"worldgen_random_modes":[False,True],"resident_chunks_per_fixture":9,"requested_placements":sum(len(f["features"])*2 for f in fixtures),"direct_tick_requests":sum(len(f["tick_commands"]) for f in fixtures),
+            "block_states":len(facts["states"]),"direct_state_probes":sum(len(f["probe_states"]) for f in fixtures),"write_zone_cases":len(zones),"block_tag_files":len(tags),"fixtures":len(fixtures),"worldgen_random_modes":[False,True],"resident_chunks_per_fixture":9,"requested_placements":sum(len(f["features"])*2 for f in fixtures),"direct_tick_requests":sum(len(f["tick_commands"]) for f in fixtures),
             "sources_sha256":tested_sources,"fixtures_sha256":tested_fixtures,"rust_output_sha256":lab.digest(build/"rust.txt","sha256"),"references":references,
-            "scope":"Native FeaturePlacer and three basic block-writing features, a composed sequence of four configured fill layers, single-block replacements, scattered ore and water springs share a world proxy backed by nine actual ProtoChunks. Configured water, horizontal logs, air, out-of-height fills and ore/replacement rules test graph-to-region binding. Initial two-layer stone/dirt terrain, both pre-light heightmap groups, count/square/heightmap/layered modifier chains, repeated placements, direct and WorldgenRandom-wrapped random streams, missing-neighbor errors, rejected writes and injected partial failures are compared. Final complete raw sections, heightmap presence and packed words are compared alongside ordered feature writes, update flags, explicit height queries and subsequent random draws. Rust uses resident registry-backed chunks, lazy heightmap priming and a caller-supplied write callback; imported air/fluid facts and bundled block tags bind independently across authenticated JARs. The proxy supplies storage mutation and actual native default scheduleTick/createTick methods routed through WorldGenTickAccess into each ProtoChunk. Separate block/fluid queues, first-request deduplication, nondefault-state block identity, shared tick-order advancement on duplicates and missing-chunk errors, out-of-height requests and wrapped clock values are compared, including saved queue order and priorities. Active and inactive End podiums additionally exercise native WorldGenRegion.destroyBlock through a subclass transport overriding only block reads and writes; air short-circuit, rejected replacements and write failures retain the generation-time semantics. All block states are also written into resident chunks, queried through feature access, cleared and queried again; contained fluid identity/amount/falling/source/full flags, water-tag membership and every bundled block tag plus an absent tag are compared. Negative coordinates, chunk edges, outside-height and absent chunks are covered. Block/fluid query bindings are an immutable registry-checked shared snapshot. Actual WorldGenRegion construction, write-zone policy, POIs, block entities, postprocessing execution, lighting, block/fluid tick execution, complete feature registries and complete world generation remain outside this comparison."}
+            "scope":"Native FeaturePlacer and three basic block-writing features, a composed sequence of four configured fill layers, single-block replacements, scattered ore and water springs share a world proxy backed by nine actual ProtoChunks. Configured water, horizontal logs, air, out-of-height fills and ore/replacement rules test graph-to-region binding. Initial two-layer stone/dirt terrain, both pre-light heightmap groups, count/square/heightmap/layered modifier chains, repeated placements, direct and WorldgenRandom-wrapped random streams, missing-neighbor errors, rejected writes and injected partial failures are compared. Final complete raw sections, heightmap presence and packed words are compared alongside ordered feature writes, update flags, explicit height queries and subsequent random draws. Rust uses resident registry-backed chunks, lazy heightmap priming and a caller-supplied write callback; imported air/fluid facts and bundled block tags bind independently across authenticated JARs. The proxy supplies storage mutation and actual native default scheduleTick/createTick methods routed through WorldGenTickAccess into each ProtoChunk. Separate block/fluid queues, first-request deduplication, nondefault-state block identity, shared tick-order advancement on duplicates and missing-chunk errors, out-of-height requests and wrapped clock values are compared, including saved queue order and priorities. Active and inactive End podiums additionally exercise native WorldGenRegion.destroyBlock through a subclass transport overriding only block reads and writes; air short-circuit, rejected replacements and write failures retain the generation-time semantics. All block states are also written into resident chunks, queried through feature access, cleared and queried again; contained fluid identity/amount/falling/source/full flags, water-tag membership and every bundled block tag plus an absent tag are compared. Negative coordinates, chunk edges, outside-height and absent chunks are covered. Block/fluid query bindings are an immutable registry-checked shared snapshot. The native horizontal write-zone predicate is compared separately across chunk/block coordinates, negative radii and wrapped subtraction/absolute-value extremes, and gates feature callbacks in selected fixtures. Actual WorldGenRegion construction, upgrading-world vertical write restrictions, POIs, block entities, postprocessing execution, lighting, block/fluid tick execution, complete feature registries and complete world generation remain outside this comparison."}
 
     lab.write_json(report_path,report);print(f"Scoped feature-region parity passed: {report_path}")