diff --git a/crates/horizon-client/src/entity_nbt.rs b/crates/horizon-client/src/entity_nbt.rs
index d096433396..be56708aab 100644
--- a/crates/horizon-client/src/entity_nbt.rs
+++ b/crates/horizon-client/src/entity_nbt.rs
@@ -4269,8 +4269,14 @@ fn read_variant(m: &mut Mob, tag: &Tag) {
             } else {
                 0
             };
-            m.extra.variant2 = ((packed >> 16) & 15) as u8;
-            m.extra.variant3 = ((packed >> 24) & 15) as u8;
+            // TropicalFish.getBaseColor/getPatternColor use DyeColor.byId:
+            // read the full byte, then default invalid color ids to white.
+            let color = |shift| match (packed >> shift) & 0xFF {
+                value @ 0..=15 => value as u8,
+                _ => 0,
+            };
+            m.extra.variant2 = color(16);
+            m.extra.variant3 = color(24);
         }
         _ => {}
     }
diff --git a/tools/port_map/game-011.tsv b/tools/port_map/game-011.tsv
index 95f1b5d782..5c09371ab6 100644
--- a/tools/port_map/game-011.tsv
+++ b/tools/port_map/game-011.tsv
@@ -138,7 +138,7 @@ Salmon.finalizeSpawn	port	crates/horizon-client/src/mobs/finalize.rs::Ctx::final
 Salmon.getDefaultDimensions	port	crates/horizon-client/src/mobs/living.rs::Mob::awake_dims_in	the variant's bounding box scale (small 0.5, medium 1.0, large 1.5) over the whole box, through aquatic::salmon_scale
 TropicalFish.packVariant	inline	crates/horizon-client/src/entity_nbt.rs::mob_to_nbt	packed pattern, base colour and pattern colour; lan.rs::mob_meta packs it for sync
 TropicalFish.defineSynchedData	port	crates/horizon-client/src/game/lan.rs::mob_meta	packed variant entry
-TropicalFish.readAdditionalSaveData	port	crates/horizon-client/src/entity_nbt.rs::read_variant	an unknown pattern is a kob
+TropicalFish.readAdditionalSaveData	port	crates/horizon-client/src/entity_nbt.rs::read_variant	an unknown pattern is a kob; full color bytes use DyeColor.byId zero fallback
 TropicalFish.setPattern	inline	crates/horizon-client/src/entity_nbt.rs::apply_item_components	only reached from the bucket's pattern component
 TropicalFish.setBaseColor	inline	crates/horizon-client/src/entity_nbt.rs::apply_item_components	only reached from the bucket's base colour component
 TropicalFish.setPatternColor	inline	crates/horizon-client/src/entity_nbt.rs::apply_item_components	only reached from the bucket's pattern colour component
diff --git a/tools/test_tropical_fish_variant_parity.py b/tools/test_tropical_fish_variant_parity.py
new file mode 100644
index 0000000000..b2b3bdfe6b
--- /dev/null
+++ b/tools/test_tropical_fish_variant_parity.py
@@ -0,0 +1,156 @@
+#!/usr/bin/env python3
+"""Tropical fish packed NBT color bytes normalize through DyeColor.byId.
+
+Fresh dedicated servers cover valid colors, invalid bytes and pattern fallback.
+No rendering, bucket, spawn, loot or component parity claim.
+"""
+import argparse
+import json
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+import time
+
+try:
+    from . import lab, test_rust_parity as base
+    from .test_dedicated_server_parity import Server, free_port, game_time
+    from .test_server_world_gen_parity import escape
+except ImportError:
+    import lab
+    import test_rust_parity as base
+    from test_dedicated_server_parity import Server, free_port, game_time
+    from test_server_world_gen_parity import escape
+
+CASES = [None, -1, 0, 1, 2, 1280, 1281, 1536, 65538, 117506305]
+CASES += [value << 16 for value in (15, 16, 17, 255)]
+CASES += [(value << 24) if value < 128 else (value << 24) - (1 << 32)
+          for value in (15, 16, 17, 255)]
+EXPECTED = [0, 0, 0, 1, 0, 1280, 1281, 0, 65536, 117506305,
+            983040, 0, 0, 0, 251658240, 0, 0, 0]
+MESSAGE = re.compile(r'\[Server thread/INFO\]: (?:System chat: )?(.*)$')
+
+
+def run_side(command, out, label):
+    directory = out / label
+    if directory.exists():
+        shutil.rmtree(directory)
+    directory.mkdir(parents=True)
+    props = {'server-ip': '127.0.0.1', 'server-port': str(free_port()),
+             'online-mode': 'false', 'white-list': 'false', 'level-type': 'minecraft:flat',
+             'generate-structures': 'false', 'level-seed': '42', 'difficulty': 'normal',
+             'view-distance': '2', 'simulation-distance': '2', 'spawn-protection': '0',
+             'pause-when-empty-seconds': '-1', 'max-tick-time': '-1'}
+    (directory / 'server.properties').write_text(
+        ''.join(f'{k}={escape(v)}\n' for k, v in props.items()), encoding='iso-8859-1')
+    (directory / 'eula.txt').write_text('eula=true\n')
+    server = Server(command, directory, label)
+    serial, records = 0, []
+
+    def reply(text, timeout=180):
+        nonlocal serial
+        serial += 1
+        marker = f'fish_variant_end_{serial}'
+        start = len(server.lines)
+        server.console(text)
+        server.console(f'say {marker}')
+        server.wait_for(re.escape(f'[Server] {marker}') + '$', timeout=timeout)
+        return [m.group(1) for line in server.lines[start:] if (m := MESSAGE.search(line))
+                and not m.group(1).endswith(f'[Server] {marker}')]
+
+    def advance(ticks):
+        start = game_time(server)
+        reply(f'tick step {ticks}')
+        deadline = time.monotonic() + 180
+        while game_time(server) < start + ticks:
+            assert time.monotonic() < deadline, f'{label}: tick step stalled'
+        assert game_time(server) == start + ticks
+
+    try:
+        server.wait_for(r'Done \(')
+        reply('tick freeze')
+        reply('tick rate 200')
+        assert any('false' in m for m in reply('gamerule minecraft:spawn_mobs false'))
+        assert any('normal' in m.lower() for m in reply('difficulty'))
+        reply('forceload add 0 0 31 31')
+        deadline = time.monotonic() + 300
+        while True:
+            remaining = deadline - time.monotonic()
+            assert remaining > 0, f'{label}: fish scene did not load'
+            ready = [reply(f'execute if loaded {x} 200 {z}', remaining)
+                     for x, z in ((0, 0), (16, 0), (0, 16), (16, 16))]
+            if all(any('Test passed' in m for m in messages) for messages in ready):
+                break
+        assert any('filled' in m for m in reply('fill 0 198 0 31 199 31 stone'))
+        for index, variant in enumerate(CASES):
+            reply('kill @e[type=!minecraft:player]')
+            advance(25)
+            reply('kill @e[type=minecraft:item]')
+            assert any('Test failed' in m for m in reply('execute if entity @e[tag=subject]'))
+            nbt = (f'{{Tags:["subject","fish_{index}"],NoAI:1b,NoGravity:1b,'
+                   'Silent:1b,PersistenceRequired:1b')
+            if variant is not None:
+                nbt += f',Variant:{variant}'
+            assert any('Summoned new' in m for m in reply(
+                f'summon minecraft:tropical_fish 10.5 200 10.5 {nbt}}}'))
+            for tick in (0, 1):
+                if tick:
+                    advance(1)
+                for field, text in (
+                    ('subject', 'execute if entity @e[tag=subject]'),
+                    ('Variant', 'data get entity @e[tag=subject,limit=1] Variant')):
+                    records.append({'case': index, 'input': variant, 'tick': tick,
+                                    'field': field, 'command': text, 'messages': reply(text)})
+        return records
+    finally:
+        server.stop()
+
+
+def validate_reference(records):
+    for row in records:
+        if row['field'] == 'subject':
+            assert row['messages'] == ['Test passed. Count: 1'], row
+        else:
+            values = [int(m.group(1)) for line in row['messages']
+                      if (m := re.search(r'data: (-?\d+)$', line))]
+            assert values == [EXPECTED[row['case']]], row
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--binary', type=Path, help='prebuilt Horizon server (otherwise build fast)')
+    parser.add_argument('--out', type=Path, default=lab.LOCAL / 'tropical-fish-variant-parity')
+    args = parser.parse_args()
+    lock, jars, libraries = base.verify_artifacts()
+    if args.binary:
+        binary = args.binary.resolve(strict=True)
+    else:
+        subprocess.run(['cargo', 'build', '--profile', 'fast', '-p', 'horizon-client',
+                        '--bin', 'horizon-client'], cwd=lab.ROOT, check=True)
+        metadata = json.loads(subprocess.check_output(
+            ['cargo', 'metadata', '--no-deps', '--format-version', '1'], cwd=lab.ROOT, text=True))
+        binary = Path(metadata['target_directory']) / 'fast' / (
+            'horizon-client.exe' if os.name == 'nt' else 'horizon-client')
+    out = args.out.resolve()
+    out.mkdir(parents=True, exist_ok=True)
+    cp = os.pathsep.join(map(str, [jars['server'], *libraries]))
+    commands = {'vanilla': ['java', '-Xmx2g', '-cp', cp, 'net.minecraft.server.Main', 'nogui'],
+                'horizon': [binary, '--resources', lab.RESOURCES.resolve(), '--dedicated', '--nogui']}
+    results = {label: run_side(command, out, label) for label, command in commands.items()}
+    lab.write_json(out / 'records.json', results)
+    expected, actual = results['vanilla'], results['horizon']
+    assert len(expected) == len(actual) == 72
+    validate_reference(expected)
+    failures = [{'vanilla': v, 'horizon': h} for v, h in zip(expected, actual) if v != h]
+    lab.write_json(out / 'report.json', {'schema': 1, 'minecraft': lock['minecraft']['version'],
+                                       'observations': len(expected), 'failures': failures,
+                                       'scope': 'Packed entity NBT only; no render/bucket/spawn/loot/component claim.'})
+    print(f'{len(expected) - len(failures)}/{len(expected)} observations match', flush=True)
+    for failure in failures:
+        print(json.dumps(failure), flush=True)
+    assert not failures, f'{len(failures)} fish variant observations differ; see {out}'
+
+
+if __name__ == '__main__':
+    main()