diff --git a/tools/agent_control_e2e.py b/tools/agent_control_e2e.py
index 53296669ab..109896b111 100644
--- a/tools/agent_control_e2e.py
+++ b/tools/agent_control_e2e.py
@@ -32,6 +32,11 @@ import tempfile
 import time
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 LAVAPIPE = Path('/run/opengl-driver/share/vulkan/icd.d/lvp_icd.x86_64.json')
 LOG_KINDS = ['oak_log', 'birch_log', 'spruce_log', 'jungle_log', 'acacia_log', 'dark_oak_log',
@@ -431,7 +436,7 @@ def run(mode, ctl, out, resources, which='survival'):
     work = Path(tempfile.mkdtemp(prefix=f'hzac-{mode}-'))
     (work / '.local').mkdir()
     (work / '.local/horizon-client').mkdir()
-    os.symlink(resources, work / '.local/horizon-client/26.3')
+    os.symlink(resources, work / '.local/horizon-client' / lab.VERSION)
     socket = work / 'c.sock'
     env = game_env(os.environ.get('VSCREEN', 'agent-control'))
     driver = (Cli if mode == 'cli' else Mcp)(ctl, socket, work, env)
@@ -472,7 +477,7 @@ def main():
         meta = json.loads(subprocess.run(['cargo', 'metadata', '--format-version', '1', '--no-deps'], cwd=ROOT,
                                          capture_output=True, text=True, check=True).stdout)
         bins = Path(meta['target_directory']) / 'fast'
-    resources = (ROOT / '.local/horizon-client/26.3').resolve()
+    resources = (lab.RESOURCES).resolve()
     if not (resources / 'horizon-resources.json').exists():
         sys.exit(f'no prepared resources in {resources}')
     out = Path(args.out)
diff --git a/tools/audio_harness.py b/tools/audio_harness.py
index 52054c2f2a..6a26f2d443 100644
--- a/tools/audio_harness.py
+++ b/tools/audio_harness.py
@@ -18,7 +18,7 @@ try:
 except ImportError:
     import lab, test_rust_parity as base, test_model_baking_parity as baking
 
-RESOURCES = lab.LOCAL / 'horizon-client/26.3'
+RESOURCES = lab.RESOURCES
 COMMON_SOURCES = [
     lab.ROOT / 'tools/audio_harness.py',
     lab.ROOT / 'tools/test_rust_parity.py',
diff --git a/tools/bench_sprite_mips.py b/tools/bench_sprite_mips.py
index 93e6e88996..68024d6d22 100644
--- a/tools/bench_sprite_mips.py
+++ b/tools/bench_sprite_mips.py
@@ -10,6 +10,11 @@ import os
 from pathlib import Path
 import subprocess
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 
 
@@ -31,7 +36,7 @@ def main():
     mode.add_argument('--test', action='store_true', help='run extracted production upload tests')
     mode.add_argument('--build-only', action='store_true', help='build without measuring')
     parser.add_argument('--label', default='candidate')
-    parser.add_argument('--resources', type=Path, default=ROOT / '.local/horizon-client/26.3')
+    parser.add_argument('--resources', type=Path, default=lab.RESOURCES)
     args = parser.parse_args()
     path = 'crates/horizon-client/src/gfx.rs'
     source = (subprocess.check_output(['git', 'show', f'{args.ref}:{path}'], cwd=ROOT, text=True)
diff --git a/tools/fetch_client_assets.py b/tools/fetch_client_assets.py
index 5139253741..2027593c51 100644
--- a/tools/fetch_client_assets.py
+++ b/tools/fetch_client_assets.py
@@ -21,8 +21,8 @@ def wanted(name):
 
 def main():
     parser = argparse.ArgumentParser(description=__doc__)
-    parser.add_argument('--target', type=Path, default=lab.LOCAL / 'horizon-client/26.3',
-                        help='prepared resource directory (default: .local/horizon-client/26.3)')
+    parser.add_argument('--target', type=Path, default=lab.RESOURCES,
+                        help='prepared resource directory (default: .local/horizon-client/<pinned version>)')
     parser.add_argument('--minecraft-dir', type=Path,
                         help="official launcher game directory (default: the launcher's own)")
     args = parser.parse_args()
diff --git a/tools/gen_block_state_data.py b/tools/gen_block_state_data.py
index 5a4ab40724..0f2db7a630 100644
--- a/tools/gen_block_state_data.py
+++ b/tools/gen_block_state_data.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 """Convert vanilla's BlockStateData.java into a plain data file.
 
-Reads  .local/minecraft/26.3/sources/server/net/minecraft/util/datafix/fixes/BlockStateData.java
+Reads  .local/minecraft/<pinned version>/sources/server/net/minecraft/util/datafix/fixes/BlockStateData.java
 Writes crates/horizon-world/src/datafix/block_state_data.txt
 
 Output: UTF-8, '#' header lines, then one line per register() call, in the order the
@@ -20,8 +20,13 @@ import re
 import sys
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 REPO = Path(__file__).resolve().parent.parent
-DEFAULT_JAVA = REPO / ".local/minecraft/26.3/sources/server/net/minecraft/util/datafix/fixes/BlockStateData.java"
+DEFAULT_JAVA = lab.GAME / "sources/server/net/minecraft/util/datafix/fixes/BlockStateData.java"
 DEFAULT_OUT = REPO / "crates/horizon-world/src/datafix/block_state_data.txt"
 
 TOKEN_RE = re.compile(
@@ -305,7 +310,7 @@ def main():
         raise SystemExit(f"create count mismatch: textual {textual_create}, parsed {total_create}")
 
     header = [
-        "# Generated by tools/gen_block_state_data.py from vanilla 26.3 BlockStateData.java. Do not edit.",
+        f"# Generated by tools/gen_block_state_data.py from vanilla {lab.VERSION} BlockStateData.java. Do not edit.",
         "# One line per register(ID, new, legacy...) call, in execution order of the static initializer",
         "# (bootstrap0, 1, 2, 3_1, 3_2, 4 .. 9, A .. F).",
         "# Format (tab separated): ID <TAB> newName <TAB> newProps [<TAB> legacyName <TAB> legacyProps]...",
diff --git a/tools/gen_flat_tables.py b/tools/gen_flat_tables.py
index 3962091993..78582960f7 100644
--- a/tools/gen_flat_tables.py
+++ b/tools/gen_flat_tables.py
@@ -11,8 +11,13 @@ import subprocess
 import sys
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
-FIXES = ROOT / '.local' / 'minecraft' / '26.3' / 'sources' / 'server' / 'net' / 'minecraft' / 'util' / 'datafix' / 'fixes'
+FIXES = lab.GAME / 'sources' / 'server' / 'net' / 'minecraft' / 'util' / 'datafix' / 'fixes'
 OUT = ROOT / 'crates' / 'horizon-world' / 'src' / 'datafix' / 'flat_tables.rs'
 
 STR = r'"((?:[^"\\]|\\.)*)"'
diff --git a/tools/generate_entity_tracking.py b/tools/generate_entity_tracking.py
index 434033b372..06beb144a4 100644
--- a/tools/generate_entity_tracking.py
+++ b/tools/generate_entity_tracking.py
@@ -5,12 +5,17 @@ trackDeltas, which ChunkMap.TrackedEntity and ServerEntity use to decide who
 sees an entity and how often its movement is sent), read from the decompiled
 EntityTypes.java.
 
-  generate_entity_tracking.py [--sources .local/minecraft/26.3/sources/client]
+  generate_entity_tracking.py [--sources .local/minecraft/<pinned version>/sources/client]
 """
 import argparse
 import re
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 INT_MAX = 2147483647
 
@@ -34,7 +39,7 @@ def parse(sources):
 
 def main():
     parser = argparse.ArgumentParser(description=__doc__)
-    parser.add_argument("--sources", type=Path, default=ROOT / ".local/minecraft/26.3/sources/client")
+    parser.add_argument("--sources", type=Path, default=lab.GAME / "sources/client")
     parser.add_argument("--out", type=Path, default=ROOT / "crates/horizon-client/src/lan/tracking.rs")
     args = parser.parse_args()
     rows = parse(args.sources)
diff --git a/tools/generate_packet_ids.py b/tools/generate_packet_ids.py
index c5c0b90f83..eddcc12fc8 100644
--- a/tools/generate_packet_ids.py
+++ b/tools/generate_packet_ids.py
@@ -10,6 +10,11 @@ import argparse
 import json
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 STATES = ["handshake", "status", "login", "configuration", "play"]
 DIRECTIONS = ["clientbound", "serverbound"]
@@ -25,8 +30,9 @@ def main():
     parser.add_argument("--out", type=Path, default=ROOT / "crates/horizon-protocol/src/ids.rs")
     args = parser.parse_args()
     report = json.loads(args.report.read_text())
+    info = lab.version_info()
     lines = [
-        "//! Packet ids per connection state and direction for protocol 777 (26.3).",
+        f"//! Packet ids per connection state and direction for protocol {info['protocol_version']} ({info['name']}).",
         "//! Generated by tools/generate_packet_ids.py from the data generator's",
         "//! packets report; do not edit by hand.",
         "#![allow(missing_docs)]",
diff --git a/tools/graphics_bench.py b/tools/graphics_bench.py
index 3de8be73a3..202a5ea3c6 100644
--- a/tools/graphics_bench.py
+++ b/tools/graphics_bench.py
@@ -25,6 +25,11 @@ import sys
 import time
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
 SEED = "1234"
 WORLD = "GraphicsBench"
@@ -153,7 +158,7 @@ def main():
     p.add_argument("--seconds", type=float, default=12.0, help="flight duration per scene")
     p.add_argument("--settle", type=float, default=2.0, help="seconds to wait before each flight")
     p.add_argument("--offscreen", action="store_true", help="render offscreen on the discrete GPU")
-    p.add_argument("--resources", default=str(ROOT / ".local/horizon-client/26.3"))
+    p.add_argument("--resources", default=str(lab.RESOURCES))
     p.add_argument("--build", default=str(ROOT / "target/release"))
     p.add_argument("--out", help="JSON file (default benchmarks/graphics/<label>.json)")
     p.add_argument("--compare", nargs=2, metavar=("BEFORE", "AFTER"),
diff --git a/tools/interaction_lab.py b/tools/interaction_lab.py
index 2c8944f020..0851b6d06c 100644
--- a/tools/interaction_lab.py
+++ b/tools/interaction_lab.py
@@ -12,7 +12,7 @@ except ImportError:
     import lab
     import test_rust_parity as base
 
-RESOURCES = lab.LOCAL / 'horizon-client' / '26.3'
+RESOURCES = lab.RESOURCES
 PARITY = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity'
 
 
diff --git a/tools/lab.py b/tools/lab.py
index 43770091b1..308aff5a71 100644
--- a/tools/lab.py
+++ b/tools/lab.py
@@ -24,6 +24,28 @@ LOCAL = ROOT / ".local"
 LOCK = ROOT / "research-lock.json"
 
 
+def pinned_version():
+    """The Minecraft version research-lock.json pins: every tool reads it from there, never by hand."""
+    version = json.loads(LOCK.read_text(encoding="utf-8"))["minecraft"]["version"]
+    if not re.fullmatch(r"[A-Za-z0-9_.-]+", version) or version in {".", ".."}:
+        raise ValueError("Unsafe version identifier in lock file")
+    return version
+
+
+VERSION = pinned_version()
+# The pinned version's imported jars, libraries and sources (tools/lab.py prepare), and the resources
+# horizon-prepare made from them.
+GAME = LOCAL / "minecraft" / VERSION
+RESOURCES = LOCAL / "horizon-client" / VERSION
+
+
+def version_info(client_jar=None):
+    """What the pinned client jar states about itself in its version.json (protocol_version, world_version,
+    pack_version, java_version...)."""
+    with zipfile.ZipFile(client_jar or GAME / "jars" / "client.jar") as archive:
+        return json.loads(archive.read("version.json"))
+
+
 def cargo_target():
     """Cargo's target directory, honouring CARGO_TARGET_DIR (tools/parity.py sets it)."""
     return ROOT / os.environ.get("CARGO_TARGET_DIR", "target")
@@ -260,10 +282,7 @@ def launcher_object(assets, checksum):
 
 def config():
     lock = json.loads(LOCK.read_text(encoding="utf-8"))
-    version = lock["minecraft"]["version"]
-    if not re.fullmatch(r"[A-Za-z0-9_.-]+", version) or version in {".", ".."}:
-        raise ValueError("Unsafe version identifier in lock file")
-    return lock, LOCAL / "minecraft" / version
+    return lock, LOCAL / "minecraft" / pinned_version()
 
 
 def bundle_entries(archive, name):
diff --git a/tools/launcher_mcp_e2e.py b/tools/launcher_mcp_e2e.py
index 1bc82485f6..8dd3dc1bc0 100644
--- a/tools/launcher_mcp_e2e.py
+++ b/tools/launcher_mcp_e2e.py
@@ -22,6 +22,11 @@ import sys
 import tempfile
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 TAG = 'v2099.1.1'
 
@@ -98,7 +103,7 @@ def main():
     parser.add_argument('--out', default=str(ROOT / '.local/launcher-mcp-e2e'), help='the screenshot goes here')
     args = parser.parse_args()
     bins = Path(args.bin_dir).resolve()
-    resources = (ROOT / '.local/horizon-client/26.3').resolve()
+    resources = (lab.RESOURCES).resolve()
     if not (resources / 'horizon-resources.json').exists():
         sys.exit(f'no prepared resources in {resources}')
     out = Path(args.out)
@@ -108,7 +113,7 @@ def main():
     (version / '.local/horizon-client').mkdir(parents=True)
     for name in ['horizon-client', 'horizon-ctl']:
         os.symlink(bins / name, version / name)
-    os.symlink(resources, version / '.local/horizon-client/26.3')
+    os.symlink(resources, version / '.local/horizon-client' / lab.VERSION)
     (version / '.installed').write_text('')
     env = dict(os.environ, HORIZON_LAUNCHER_HOME=str(work / 'launcher'), HORIZON_HOME=str(work / 'home'),
                HORIZON_NO_AUDIO='1')
diff --git a/tools/package_native_client.py b/tools/package_native_client.py
index 70f8c64ace..2d7b313437 100644
--- a/tools/package_native_client.py
+++ b/tools/package_native_client.py
@@ -15,6 +15,11 @@ import subprocess
 import tarfile
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
 LOCAL = ROOT / '.local'
 # Inputs of the exporters, not read by the game at runtime.
@@ -31,7 +36,7 @@ if [ "$1" = "--install" ]; then
 [Desktop Entry]
 Type=Application
 Name=Horizon
-Comment=Minecraft Java Edition 26.3 in Rust
+Comment=Minecraft Java Edition @MINECRAFT@ in Rust
 Exec="$here/horizon.sh"
 Icon=$here/horizon.png
 Terminal=false
@@ -73,7 +78,7 @@ def add_bytes(tar, name, data, mode=0o644):
 def main():
     parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
     parser.add_argument('--binary', type=Path, help='built horizon-client (default: cargo release target)')
-    parser.add_argument('--resources', type=Path, default=LOCAL / 'horizon-client/26.3')
+    parser.add_argument('--resources', type=Path, default=lab.RESOURCES)
     parser.add_argument('--out', type=Path, default=LOCAL / 'dist')
     args = parser.parse_args()
 
@@ -107,7 +112,7 @@ def main():
         ctl = args.binary.with_name('horizon-ctl')  # built with --bins: scripts and agents play through it
         if ctl.is_file():
             tar.add(ctl, 'horizon/horizon-ctl')
-        add_bytes(tar, 'horizon/horizon.sh', LAUNCHER.encode(), 0o755)
+        add_bytes(tar, 'horizon/horizon.sh', LAUNCHER.replace('@MINECRAFT@', lab.VERSION).encode(), 0o755)
         tar.add(ROOT / 'docs/media/icon-256.png', 'horizon/horizon.png')
         add_bytes(tar, 'horizon/README.txt', README.format(version=version, commit=commit, platform=plat).encode())
         for path in sorted(args.resources.iterdir()):
diff --git a/tools/perf_bench.py b/tools/perf_bench.py
index 6d0c5571d6..eb6b3fda29 100644
--- a/tools/perf_bench.py
+++ b/tools/perf_bench.py
@@ -63,7 +63,7 @@ except ImportError:
 
 ROOT = lab.ROOT
 WORK = ROOT / ".local/perf-bench"
-VANILLA = ROOT / ".local/minecraft/26.3"
+VANILLA = lab.GAME
 SEED = 1234
 WORLD = "PerfBench"
 # (name, from xyz, to xyz, pitch): straight 192-block flights over fixed
@@ -81,7 +81,7 @@ SCENES = [
 # minimized turns off the 30 FPS limit both games apply after a minute without
 # input. Everything not listed stays at vanilla's default.
 OPTIONS = {
-    "version": "5023",
+    "version": "{data_version}",
     "graphicsPreset": '"custom"',
     "renderDistance": "{distance}",
     "simulationDistance": "12",
@@ -249,8 +249,9 @@ def nvidia_memory_mb(pid):
 
 def write_options(game_dir, distance, version=None):
     game_dir.mkdir(parents=True, exist_ok=True)
+    data_version = lab.version_info()["world_version"]
     options = dict(OPTIONS, version=version) if version else OPTIONS
-    text = "".join(f"{k}:{v.format(distance=distance)}\n" for k, v in options.items())
+    text = "".join(f"{k}:{v.format(distance=distance, data_version=data_version)}\n" for k, v in options.items())
     (game_dir / "options.txt").write_text(text)
     return text
 
@@ -543,7 +544,7 @@ def run_vanilla(args, distance):
                "-cp", os.pathsep.join(map(str, game_jars + fabric)),
                "net.fabricmc.loader.impl.launch.knot.KnotClient",
                "--username", "Bench", "--uuid", "00000000000000000000000000000000", "--accessToken", "0",
-               "--offlineDeveloperMode", "--version", "26.3", "--gameDir", str(game_dir),
+               "--offlineDeveloperMode", "--version", lab.VERSION, "--gameDir", str(game_dir),
                "--assetsDir", str(assets), "--assetIndex", manifest["assetIndex"]["id"],
                "--width", str(args.width), "--height", str(args.height)]
     env = dict(os.environ, ALSOFT_DRIVERS="null")
@@ -784,7 +785,7 @@ def main():
     p.add_argument("--heap", default="2G", help="vanilla -Xmx (the official launcher's default is 2G)")
     p.add_argument("--offscreen", action="store_true",
                    help="Horizon renders into a texture and does not wait for the window (locked macOS sessions)")
-    p.add_argument("--resources", default=str(ROOT / ".local/horizon-client/26.3"))
+    p.add_argument("--resources", default=str(lab.RESOURCES))
     p.add_argument("--build", default=str(ROOT / "target/release"))
     p.add_argument("--repeats", type=int, default=3, help="games per render distance; the report gives means and 95%% CIs")
     p.add_argument("--port-work", help="horizon: also load the mods carried over in this horizon-port-pack work folder")
@@ -830,7 +831,7 @@ def app(args):
     mods = [{"name": "fabric-loader", "version": lock["fabric_loader"]}]
     if args.game == "vanilla-mods":
         mods += [{"name": n, "version": lock["projects"][n]["version"]} for n in PERF_MODS]
-    return {"name": "minecraft", "version": "26.3", "mods": mods}
+    return {"name": "minecraft", "version": lab.VERSION, "mods": mods}
 
 
 if __name__ == "__main__":
diff --git a/tools/test_block_entity_anim_parity.py b/tools/test_block_entity_anim_parity.py
index eb47285d8c..8935afef46 100755
--- a/tools/test_block_entity_anim_parity.py
+++ b/tools/test_block_entity_anim_parity.py
@@ -261,7 +261,7 @@ def main():
     libraries = baking.client_libraries()
     build = lab.LOCAL / 'rust-block-entity-anim-parity'
     build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     chosen = [c for c in cases() if args.filter in c['name']]
     inputs = build / 'inputs.jsonl'
     inputs.write_text(''.join(json.dumps(c) + '\n' for c in chosen))
diff --git a/tools/test_block_entity_render_parity.py b/tools/test_block_entity_render_parity.py
index 8d11389fd3..3c096bdcc8 100644
--- a/tools/test_block_entity_render_parity.py
+++ b/tools/test_block_entity_render_parity.py
@@ -285,7 +285,7 @@ def main():
     lock, jars, _ = base.verify_artifacts()
     libraries = baking.client_libraries()
     build = lab.LOCAL / 'rust-block-entity-render-parity'; build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     chosen = [c for c in cases() if args.filter in c['block']]
     inputs = build / 'inputs.jsonl'; inputs.write_text(''.join(json.dumps(c) + '\n' for c in chosen))
     classes = build / 'classes'; classes.mkdir(exist_ok=True)
diff --git a/tools/test_block_particles_parity.py b/tools/test_block_particles_parity.py
index c4e1918318..3f0f0f99c0 100644
--- a/tools/test_block_particles_parity.py
+++ b/tools/test_block_particles_parity.py
@@ -10,7 +10,7 @@ except ImportError:
 
 def main():
     lock, jars, _ = base.verify_artifacts()
-    resources = lab.LOCAL / "horizon-client/26.3"
+    resources = lab.RESOURCES
     build = lab.LOCAL / "block-particles-parity"
     build.mkdir(exist_ok=True)
     paths = [lab.ROOT / p for p in ["tools/test_block_particles_parity.py", "tools/test_breaking_model_parity.py", "tools/oracle_harness.py", "tools/lab.py", "crates/horizon-client/src/particles.rs", "crates/horizon-client/src/game.rs", "crates/horizon-client/src/blocks.rs", "crates/horizon-client/src/mesher.rs", "crates/horizon-client/examples/block_particles_fixture.rs", "mods/horizon/src/test/java/dev/horizonlab/parity/VanillaBlockParticlesOracle.java", "crates/horizon-core/src/random.rs", "Cargo.lock", "mods/horizon/src/test/java/dev/horizonlab/parity/VanillaGameplayFactsExporter.java"]]
diff --git a/tools/test_breaking_model_parity.py b/tools/test_breaking_model_parity.py
index 11e627d123..92b74d5822 100644
--- a/tools/test_breaking_model_parity.py
+++ b/tools/test_breaking_model_parity.py
@@ -28,7 +28,7 @@ def canonical(quads):
 
 def main():
     lock,jars,_=base.verify_artifacts();libraries=baking.client_libraries()
-    resources=lab.LOCAL/"horizon-client/26.3";build=lab.LOCAL/"breaking-model-parity";build.mkdir(exist_ok=True)
+    resources=lab.RESOURCES;build=lab.LOCAL/"breaking-model-parity";build.mkdir(exist_ok=True)
     paths=[lab.ROOT/"tools/test_breaking_model_parity.py",lab.ROOT/"crates/horizon-client/src/breaking.rs",lab.ROOT/"crates/horizon-client/src/game.rs",lab.ROOT/"crates/horizon-client/src/gfx.rs",lab.ROOT/"crates/horizon-client/src/entity.wgsl",lab.ROOT/"crates/horizon-client/src/models/catalog.rs",lab.ROOT/"crates/horizon-client/src/mesher.rs",lab.ROOT/"crates/horizon-client/src/camera.rs",lab.ROOT/"crates/horizon-client/examples/breaking_fixture.rs",lab.ROOT/"mods/horizon/src/test/java/dev/horizonlab/parity/VanillaBreakingModelOracle.java",lab.ROOT/"mods/horizon/src/test/java/dev/horizonlab/parity/VanillaSectionMeshOracle.java",lab.ROOT/"Cargo.lock"]
     tested=base.source_hashes(paths)
     rows=[dict(case=i,**row) for i,row in enumerate(cases(resources))]
diff --git a/tools/test_chunk_generation_parity.py b/tools/test_chunk_generation_parity.py
index 864ad4cace..9e2487206c 100644
--- a/tools/test_chunk_generation_parity.py
+++ b/tools/test_chunk_generation_parity.py
@@ -40,7 +40,7 @@ SEEDS = [12345, -7046029254386353131, 987654321987, 4242, -1, 0x5DEECE66D, 20260
 REGRESSIONS = [
     (-1860902098141295193, 'the_nether', '-1,6,3,9', 'bastion_remnant across 20 chunks (#249)'),
 ]
-RESOURCES = lab.LOCAL / 'horizon-client/26.3'
+RESOURCES = lab.RESOURCES
 ORACLE = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaChunkGenerationOracle.java'
 
 
diff --git a/tools/test_client_graphics.py b/tools/test_client_graphics.py
index a230408436..2eb8d4c14d 100644
--- a/tools/test_client_graphics.py
+++ b/tools/test_client_graphics.py
@@ -10,6 +10,11 @@ import re
 import shutil
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
     from .test_culling_rays import FixtureTimeout, run_fixture
@@ -179,7 +184,7 @@ def main():
         print(json.dumps(report), flush=True)
     output = root / 'dist/client-graphics-smoke.json'
     output.write_text(json.dumps({'schema': 1, 'platform': platform.platform(),
-        'architecture': platform.machine(), 'minecraft': '26.3',
+        'architecture': platform.machine(), 'minecraft': lab.VERSION,
         'original_mod_sha256': original_hash, 'results': results,
         'limits': ['Short scene startup and nonuniform framebuffer readback only.',
                   'World mode uses the ordinary limited demo; world files remain private.',
diff --git a/tools/test_command_exec_parity.py b/tools/test_command_exec_parity.py
index 2aa0c757a5..9d57d3f69e 100644
--- a/tools/test_command_exec_parity.py
+++ b/tools/test_command_exec_parity.py
@@ -83,7 +83,7 @@ def main():
     shutil.rmtree(rust_dir, ignore_errors=True)
     rust_dir.mkdir()
     env = dict(os.environ, HORIZON_NO_AUDIO='1', HORIZON_COMMAND_SCRIPT=str(script_path), HORIZON_COMMAND_OUTPUT=str(build / 'rust.jsonl'))
-    run([binary, '--resources', lab.LOCAL / 'horizon-client/26.3', '--world', 'harness', '--seed', SEED, '--radius', 4], 'rust', cwd=rust_dir, env=env)
+    run([binary, '--resources', lab.RESOURCES, '--world', 'harness', '--seed', SEED, '--radius', 4], 'rust', cwd=rust_dir, env=env)
 
     vanilla = [json.loads(l) for l in (build / 'vanilla.jsonl').open(encoding='utf-8')]
     rust = [json.loads(l) for l in (build / 'rust.jsonl').open(encoding='utf-8')]
diff --git a/tools/test_command_parse_parity.py b/tools/test_command_parse_parity.py
index bb80dc39ef..192cc5b9f3 100644
--- a/tools/test_command_parse_parity.py
+++ b/tools/test_command_parse_parity.py
@@ -67,7 +67,7 @@ def main():
     run(['cargo', 'build', '--release', '-p', 'horizon-client', '--example', 'command_parse_fixture'], 'compile-rust')
     metadata = json.loads(subprocess.check_output(['cargo', 'metadata', '--no-deps', '--format-version', '1'], cwd=lab.ROOT, text=True))
     binary = Path(metadata['target_directory']) / 'release/examples' / ('command_parse_fixture.exe' if os.name == 'nt' else 'command_parse_fixture')
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     total_failures = 0
     summary = []
     for permission in args.permission:
diff --git a/tools/test_culling_empty.py b/tools/test_culling_empty.py
index d2bcbbc391..37a74b0239 100644
--- a/tools/test_culling_empty.py
+++ b/tools/test_culling_empty.py
@@ -9,6 +9,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -50,7 +55,7 @@ def main():
         raise AssertionError("Empty shortcut did not apply to actual methods")
     output = root / "dist/culling-empty-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "entity_culling": "1.11.2", "results": results,
+        "minecraft": lab.VERSION, "entity_culling": "1.11.2", "results": results,
         "notes": ["Actual publisher whitelist methods inside Fabric; live registration and block-entity callbacks checked.",
                   "Nonempty iteration, callback order, short circuit, null/wrong-type inputs and clearing retain upstream behavior.",
                   "Empty-state iterator counts use a private instrumented set; allocation loop uses normal empty HashSets.",
diff --git a/tools/test_culling_rays.py b/tools/test_culling_rays.py
index b0dfba84be..39a5f8338f 100644
--- a/tools/test_culling_rays.py
+++ b/tools/test_culling_rays.py
@@ -11,6 +11,11 @@ import signal
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -86,7 +91,7 @@ def main():
             raise AssertionError(f"Scratch redirect changed upstream geometry: {key}")
     output = root / "dist/culling-rays-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "entity_culling": "1.11.2", "original_mod_sha256": original_sha256, "results": results,
+        "minecraft": lab.VERSION, "entity_culling": "1.11.2", "original_mod_sha256": original_sha256, "results": results,
         "notes": ["Actual upstream culling methods inside Fabric; private fixture invokers do not enter production packs.",
                   "Two interleaved instances and several occluder patterns; matching boolean and query digests.",
                   "Signed zero, tiny/large values, infinities and NaN are exercised directly in ray intersection.",
diff --git a/tools/test_dedicated_server_parity.py b/tools/test_dedicated_server_parity.py
index 23f3043184..22677bf07a 100644
--- a/tools/test_dedicated_server_parity.py
+++ b/tools/test_dedicated_server_parity.py
@@ -342,7 +342,7 @@ def horizon_client_joins(vanilla_server, binary, world, build, reference):
         server.wait_for(r'Done \(')
         env = dict(os.environ, HORIZON_NO_AUDIO='1', HORIZON_NET_REPORT=str(report))
         with (build / 'horizon-client-run.log').open('w') as log:
-            subprocess.run([str(c) for c in [binary, '--resources', lab.LOCAL / 'horizon-client/26.3', '--render-distance', 2,
+            subprocess.run([str(c) for c in [binary, '--resources', lab.RESOURCES, '--render-distance', 2,
                                              '--server', f'127.0.0.1:{port}', '--name', PLAYER]],
                            cwd=client_dir, env=env, stdout=log, stderr=subprocess.STDOUT, timeout=300, check=True)
         server.wait_for(r'left the game', timeout=30)
@@ -394,7 +394,7 @@ def main():
                                                   cwd=lab.ROOT, text=True))
     binary = Path(metadata['target_directory']) / 'release' / ('horizon-client.exe' if os.name == 'nt' else 'horizon-client')
     vanilla_server = ['java', '-Xmx2g', '-Duser.timezone=UTC', '-cp', dependencies, 'net.minecraft.server.Main', 'nogui']
-    horizon_server = [binary, '--resources', lab.LOCAL / 'horizon-client/26.3', '--dedicated', '--nogui']
+    horizon_server = [binary, '--resources', lab.RESOURCES, '--dedicated', '--nogui']
 
     # The world, generated once by vanilla.
     generate = build / 'generate'
diff --git a/tools/test_dispatch.py b/tools/test_dispatch.py
index a38df01b5b..5c54836661 100644
--- a/tools/test_dispatch.py
+++ b/tools/test_dispatch.py
@@ -11,6 +11,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
     from .test_culling_rays import run_fixture
@@ -69,7 +74,7 @@ def main():
         print(json.dumps(report), flush=True)
     output = root / "dist/dispatch-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "results": results,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "results": results,
         "notes": ["Synthetic full physical worker queue; both modes use the actual publisher dispatcher inside Fabric.",
                   "Allocation and CPU measure the submission caller only; retry scheduler activity is excluded.",
                   "Upstream keeps the caller blocked for the requested 200 ms observation window; patched returns earlier.",
diff --git a/tools/test_enchanting_parity.py b/tools/test_enchanting_parity.py
index 38c4baa18d..4b5c975d0f 100644
--- a/tools/test_enchanting_parity.py
+++ b/tools/test_enchanting_parity.py
@@ -38,7 +38,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     catalog = json.loads((resources / 'items.json').read_text())
     items = sorted(k for k, v in catalog.items() if 'minecraft:enchantable' in v)
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaEnchantingOracle.java'
diff --git a/tools/test_entity_components_parity.py b/tools/test_entity_components_parity.py
index fe9fcac96f..9e35381bb0 100644
--- a/tools/test_entity_components_parity.py
+++ b/tools/test_entity_components_parity.py
@@ -19,7 +19,7 @@ SPECIES = ('wolf', 'cat', 'frog', 'pig', 'cow', 'chicken')
 def predicates():
     """Every criterion's entity predicate, plus the components alone and
     with the wrong type."""
-    folder = lab.LOCAL / 'horizon-client/26.3/data/minecraft/advancement/husbandry'
+    folder = lab.RESOURCES / 'data/minecraft/advancement/husbandry'
     out = []
     for name in ADVANCEMENTS:
         data = json.loads((folder / f'{name}.json').read_text())
@@ -33,7 +33,7 @@ def predicates():
 
 
 def variants(species):
-    folder = lab.LOCAL / f'horizon-client/26.3/data/minecraft/{species}_variant'
+    folder = lab.RESOURCES / f'data/minecraft/{species}_variant'
     return sorted('minecraft:' + p.stem for p in folder.glob('*.json'))
 
 
diff --git a/tools/test_entity_death_loot_parity.py b/tools/test_entity_death_loot_parity.py
index 5f5e5cbdc7..000a2ea6f9 100644
--- a/tools/test_entity_death_loot_parity.py
+++ b/tools/test_entity_death_loot_parity.py
@@ -118,7 +118,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     tables = resources / 'data/minecraft/loot_table/entities'
     types = sorted('minecraft:' + p.stem for p in tables.glob('*.json') if p.stem not in SKIPPED)
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaEntityDeathLootOracle.java'
diff --git a/tools/test_entity_model_parity.py b/tools/test_entity_model_parity.py
index 5298e1cd71..37c61b4ac1 100644
--- a/tools/test_entity_model_parity.py
+++ b/tools/test_entity_model_parity.py
@@ -36,7 +36,7 @@ try:
 except ImportError:
     import lab, test_rust_parity as base, test_model_baking_parity as baking
 
-CLIENT = lab.LOCAL / 'minecraft' / '26.3' / 'sources' / 'client' / 'net' / 'minecraft' / 'client'
+CLIENT = lab.GAME / 'sources' / 'client' / 'net' / 'minecraft' / 'client'
 
 # Models that no renderer builds with a plain `new Model(context.bakeLayer(CONSTANT))`.
 EXTRAS = [
@@ -341,7 +341,7 @@ def main():
     lock, jars, _ = base.verify_artifacts()
     libraries = baking.client_libraries()
     build = lab.LOCAL / 'rust-entity-model-parity'; build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     models = json.loads((resources / 'entity-models.json').read_text())
     chosen = {k: v for k, v in layers(models).items() if args.filter in k}
     extra_cases = json.loads((Path(__file__).with_suffix('.cases.json')).read_text()) \
diff --git a/tools/test_environment_render_parity.py b/tools/test_environment_render_parity.py
index 4a1979fc21..2e14bb3564 100755
--- a/tools/test_environment_render_parity.py
+++ b/tools/test_environment_render_parity.py
@@ -51,7 +51,7 @@ def main():
     args = parser.parse_args()
     lock, jars, libraries = base.verify_artifacts()
     build = lab.LOCAL / 'rust-environment-parity'; build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     inputs = build / 'inputs.txt'; inputs.write_text('\n'.join(cases(resources)) + '\n')
     classes = build / 'classes'; classes.mkdir(exist_ok=True)
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaEnvironmentOracle.java'
diff --git a/tools/test_finalize_spawn_parity.py b/tools/test_finalize_spawn_parity.py
index 23948d7b9e..7c995fa83a 100644
--- a/tools/test_finalize_spawn_parity.py
+++ b/tools/test_finalize_spawn_parity.py
@@ -116,7 +116,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaFinalizeSpawnOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/finalize_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/finalize.rs']
diff --git a/tools/test_friends.py b/tools/test_friends.py
index 04399fe0fa..f89f3e5999 100644
--- a/tools/test_friends.py
+++ b/tools/test_friends.py
@@ -31,6 +31,11 @@ import tempfile
 import time
 import urllib.request
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 
 
@@ -330,7 +335,7 @@ def main():
     parser.add_argument('--client', type=Path, required=True)
     parser.add_argument('--relay', type=Path, help='horizon-relay binary (started on a free local port)')
     parser.add_argument('--relay-url', help='--role: a relay already running elsewhere, HOST:PORT')
-    parser.add_argument('--resources', type=Path, default=ROOT / '.local/horizon-client/26.3')
+    parser.add_argument('--resources', type=Path, default=lab.RESOURCES)
     parser.add_argument('--role', choices=['host', 'guest'])
     parser.add_argument('--code')
     parser.add_argument('--path', choices=['relay', 'direct'])
diff --git a/tools/test_hud_parity.py b/tools/test_hud_parity.py
index bb39c43be5..a0baa32146 100644
--- a/tools/test_hud_parity.py
+++ b/tools/test_hud_parity.py
@@ -99,7 +99,7 @@ def main():
     lock, jars, _ = base.verify_artifacts()
     libraries = baking.client_libraries()
     build = lab.LOCAL / 'rust-hud-parity'; build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     chosen = cases(args.count, kinds)
     inputs = build / 'inputs.jsonl'; inputs.write_text(''.join(json.dumps(c) + '\n' for c in chosen))
     classes = build / 'classes'; classes.mkdir(exist_ok=True)
diff --git a/tools/test_lan_lifecycle.py b/tools/test_lan_lifecycle.py
index 1ad67d0f97..14c74971e8 100644
--- a/tools/test_lan_lifecycle.py
+++ b/tools/test_lan_lifecycle.py
@@ -16,6 +16,11 @@ import subprocess
 import tempfile
 import time
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
 GROUP = '224.0.2.60'
 DISCOVERY_PORT = 4445
@@ -145,7 +150,7 @@ def guest_names(endpoint, port, guests):
 def main():
     parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument('--client', type=Path, required=True)
-    parser.add_argument('--resources', type=Path, default=ROOT / '.local/horizon-client/26.3')
+    parser.add_argument('--resources', type=Path, default=lab.RESOURCES)
     args = parser.parse_args()
     client, resources = args.client.resolve(), args.resources.resolve()
     with tempfile.TemporaryDirectory(prefix='horizon-lan-') as directory:
diff --git a/tools/test_light_parity.py b/tools/test_light_parity.py
index 3e42acd5c1..ad3945ba8d 100755
--- a/tools/test_light_parity.py
+++ b/tools/test_light_parity.py
@@ -16,10 +16,15 @@ import subprocess
 import sys
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
 LOCAL = ROOT / '.local'
-RESOURCES = LOCAL / 'horizon-client' / '26.3'
-SERVER = LOCAL / 'minecraft' / '26.3' / 'jars' / 'server.jar'
+RESOURCES = lab.RESOURCES
+SERVER = lab.GAME / 'jars' / 'server.jar'
 
 # Absolute coordinates well above the terrain, inside force-loaded chunks.
 SCENE = [
diff --git a/tools/test_mipmap_parity.py b/tools/test_mipmap_parity.py
index dce292f886..4970313901 100644
--- a/tools/test_mipmap_parity.py
+++ b/tools/test_mipmap_parity.py
@@ -26,7 +26,7 @@ def size(png):
 
 
 def make_input(build):
-    root = oh.lab.LOCAL / 'horizon-client' / '26.3'
+    root = oh.lab.RESOURCES
     textures = root / 'assets/minecraft/textures'
     names = []
     for folder, every in (('block', 1), ('item', 7)):
diff --git a/tools/test_mob_ai_parity.py b/tools/test_mob_ai_parity.py
index 9bb244ce9a..6eda7583e3 100644
--- a/tools/test_mob_ai_parity.py
+++ b/tools/test_mob_ai_parity.py
@@ -469,7 +469,7 @@ def main():
                        CARGO_PROFILE_RELEASE_LTO='false', CARGO_PROFILE_RELEASE_CODEGEN_UNITS='16')
         oracle_harness.run_logged(command, build, 'compile-rust', env=env)
         binary = target / 'release/examples/mob_ai_probe'
-        oracle_harness.run_logged([binary, lab.ROOT / '.local/horizon-client/26.3', inputs, build / 'horizon.txt'], build, 'horizon')
+        oracle_harness.run_logged([binary, lab.RESOURCES, inputs, build / 'horizon.txt'], build, 'horizon')
     if args.java_only:
         return
     names = {s[0] for _, s in chosen}
diff --git a/tools/test_mob_attributes_parity.py b/tools/test_mob_attributes_parity.py
index 9328d223e3..1e4057eb7e 100755
--- a/tools/test_mob_attributes_parity.py
+++ b/tools/test_mob_attributes_parity.py
@@ -64,7 +64,7 @@ def main():
     run(['java', '-Xmx1G', '-cp', os.pathsep.join([str(classes), str(jars['server']), deps]), 'dev.horizonlab.parity.VanillaMobAttributesOracle', build / 'vanilla.txt'], 'java')
     run(['cargo', 'build', '--release', '-p', 'horizon-client', '--example', 'mob_attributes_fixture'], 'compile-rust')
     binary = lab.cargo_target() / 'release/examples/mob_attributes_fixture'
-    resources = lab.ROOT / '.local/horizon-client/26.3'
+    resources = lab.RESOURCES
     run([binary, resources, build / 'rust.txt'], 'rust')
     vanilla, rust = parse(build / 'vanilla.txt'), parse(build / 'rust.txt')
     problems = []
diff --git a/tools/test_native_client.py b/tools/test_native_client.py
index 0ddb00c031..73e6f32238 100644
--- a/tools/test_native_client.py
+++ b/tools/test_native_client.py
@@ -43,7 +43,7 @@ def main():
     root.mkdir(parents=True, exist_ok=True)
     report = root / 'startup-smoke.json'
     report.unlink(missing_ok=True)
-    resources = resource_fingerprint(root / '26.3')
+    resources = resource_fingerprint(root / lab.VERSION)
     sources = [lab.ROOT / 'Cargo.toml', lab.ROOT / 'Cargo.lock', Path(__file__).resolve(),
                lab.ROOT / 'crates/horizon-client/Cargo.toml', lab.ROOT / 'crates/horizon-assets/Cargo.toml',
                *sorted((lab.ROOT / 'crates/horizon-client/src').rglob('*')),
@@ -91,7 +91,7 @@ def main():
                         '-d', str(classes), str(oracle), str(helper), str(heightmap)], cwd=lab.ROOT, check=True,
                        stdout=log, stderr=subprocess.STDOUT, timeout=3600)
         subprocess.run(['java', '-Xmx512M', '-cp', str(classes)+os.pathsep+dependencies,
-                        'dev.horizonlab.parity.VanillaGallerySelectionOracle', str(report), str(native), str(root/'26.3')],
+                        'dev.horizonlab.parity.VanillaGallerySelectionOracle', str(report), str(native), str(root / lab.VERSION)],
                        cwd=lab.ROOT, check=True, stdout=log, stderr=subprocess.STDOUT, timeout=3600)
     native_result = json.loads(native.read_text())
     selections = native_result['gallery']
@@ -103,12 +103,12 @@ def main():
                                   'client_jar_sha256': lab.digest(jars['client'], 'sha256'),
                                   'output_sha256': lab.digest(native, 'sha256'),
                                   'scope': 'Actual native registry states, blockstate dispatch, tagged root baking and legacy collection using state.getSeed(position). All 16 featured placements match model names/transforms. An independently constructed native scene also matches total occupied blocks and visible/culled model faces using native parent resolution, rotated culling directions and Block.shouldRenderFace. No shader/pixel parity claim.'}
-    if resource_fingerprint(root / '26.3') != resources:
+    if resource_fingerprint(root / lab.VERSION) != resources:
         raise RuntimeError('Resources changed during native client verification')
     result['resource_files'] = resources
     result['executable_sha256'] = lab.digest(executable, 'sha256')
     result['resource_manifest_sha256'] = lab.digest(
-        root / '26.3/horizon-resources.json', 'sha256')
+        root / lab.VERSION / 'horizon-resources.json', 'sha256')
     actual_sources = {str(path.relative_to(lab.ROOT)): lab.digest(path, 'sha256') for path in sources if path.is_file()}
     if actual_sources != tested_sources:
         raise RuntimeError('Sources changed during native client verification')
diff --git a/tools/test_natural_spawn_parity.py b/tools/test_natural_spawn_parity.py
index d6db51fbab..fabdc184b6 100644
--- a/tools/test_natural_spawn_parity.py
+++ b/tools/test_natural_spawn_parity.py
@@ -548,7 +548,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaNaturalSpawnOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/natural_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawn_selection.rs',
diff --git a/tools/test_online_mode_parity.py b/tools/test_online_mode_parity.py
index e6679b7b5e..1fba1111d3 100644
--- a/tools/test_online_mode_parity.py
+++ b/tools/test_online_mode_parity.py
@@ -180,7 +180,7 @@ def run_client(binary, build, port, label, token, discovery):
     directory.mkdir()
     report = directory / 'report.json'
     env = dict(os.environ, HORIZON_NO_AUDIO='1', HORIZON_NET_REPORT=str(report), HORIZON_API_DISCOVERY=discovery)
-    command = [binary, '--resources', lab.LOCAL / 'horizon-client/26.3', '--render-distance', 2,
+    command = [binary, '--resources', lab.RESOURCES, '--render-distance', 2,
                '--server', f'127.0.0.1:{port}', '--name', PLAYER]
     if token:
         command += ['--session-file', session_file(directory, token)]
diff --git a/tools/test_quad_reuse.py b/tools/test_quad_reuse.py
index baa95c387c..11172aef29 100644
--- a/tools/test_quad_reuse.py
+++ b/tools/test_quad_reuse.py
@@ -10,6 +10,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -59,7 +64,7 @@ def main():
             raise AssertionError(f"Quad reuse changed upstream geometry: {key}")
     output = root / "dist/quad-reuse-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
         "notes": ["Actual publisher quad builder inside Fabric with generated faces and lighting/material values.",
                   "Opaque/translucent geometry, pooled error flags and every retained quad field match before and after upstream merging.",
                   "Fresh allocations reuse at most one discarded successful-premerge quad; existing pool selection stays upstream.",
diff --git a/tools/test_quad_sizes.py b/tools/test_quad_sizes.py
index 51650e3736..548aefced2 100644
--- a/tools/test_quad_sizes.py
+++ b/tools/test_quad_sizes.py
@@ -11,6 +11,11 @@ import subprocess
 import sys
 import zipfile
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
     from .test_culling_rays import run_fixture
@@ -79,7 +84,7 @@ def main():
                             "additional_builder_and_scratch_bytes": candidate["builder_shallow_bytes"] - control["builder_shallow_bytes"] + candidate["pending_scratch_shallow_bytes"]})
     output = root / "dist/quad-size-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "original_mod_sha256": mod_hash,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "original_mod_sha256": mod_hash,
         "results": results, "differences": differences,
         "notes": ["Instrumentation.getObjectSize measures shallow object sizes inside real applied Fabric clients.",
                   "Four adjacent north-facing quads premerge to one retained geometry quad in each combination.",
diff --git a/tools/test_raid_parity.py b/tools/test_raid_parity.py
index 1aef07ec60..6df5f8fa69 100644
--- a/tools/test_raid_parity.py
+++ b/tools/test_raid_parity.py
@@ -314,7 +314,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaRaidOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/raid_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/raid.rs', lab.ROOT / 'crates/horizon-client/src/patrol.rs']
diff --git a/tools/test_resource_pack_parity.py b/tools/test_resource_pack_parity.py
index 87d173628a..6169542c5a 100644
--- a/tools/test_resource_pack_parity.py
+++ b/tools/test_resource_pack_parity.py
@@ -119,7 +119,7 @@ def main():
         def make(build, selection=selection):
             folder = build / "resourcepacks"
             packs(folder)
-            vanilla = lab.LOCAL / "horizon-client" / "26.3"
+            vanilla = lab.RESOURCES
             path = build / "inputs.txt"
             path.write_text(f"root {vanilla} {folder} {' '.join(selection)}".rstrip() + "\n"
                             + "".join(q + "\n" for q in QUERIES))
diff --git a/tools/test_save_roundtrip_parity.py b/tools/test_save_roundtrip_parity.py
index e912c7a61d..e2531a6571 100644
--- a/tools/test_save_roundtrip_parity.py
+++ b/tools/test_save_roundtrip_parity.py
@@ -41,10 +41,15 @@ sys.path.insert(0, str(Path(__file__).resolve().parent))
 import anvil_dump  # noqa: E402
 import save_roundtrip_scene as scene  # noqa: E402
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
 LOCAL = ROOT / '.local'
-RESOURCES = LOCAL / 'horizon-client' / '26.3'
-SERVER = LOCAL / 'minecraft' / '26.3' / 'jars' / 'server.jar'
+RESOURCES = lab.RESOURCES
+SERVER = lab.GAME / 'jars' / 'server.jar'
 RUN = LOCAL / 'save-roundtrip' / 'run'
 
 # Game rules Horizon's player changes before saving: rule -> (vanilla's value, Horizon's).
diff --git a/tools/test_section_mesh_parity.py b/tools/test_section_mesh_parity.py
index 22362bd793..78c0d68e9d 100644
--- a/tools/test_section_mesh_parity.py
+++ b/tools/test_section_mesh_parity.py
@@ -29,7 +29,7 @@ except ImportError:
     import test_model_baking_parity as baking
 
 BUILD = lab.ROOT / 'target/section-mesh-parity'
-RESOURCES = lab.LOCAL / 'horizon-client' / '26.3'
+RESOURCES = lab.RESOURCES
 SECTION_Y = 0
 COLORS = {'grass': 0x91BD59, 'foliage': 0x77AB2F, 'dry_foliage': 0xA88B5E, 'water': 0x3F76E4}
 POSITION_TOLERANCE = 1e-4
diff --git a/tools/test_server_graphics.py b/tools/test_server_graphics.py
index ac30c06807..2edaa8a484 100644
--- a/tools/test_server_graphics.py
+++ b/tools/test_server_graphics.py
@@ -8,6 +8,11 @@ import platform
 import shutil
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
     from .test_culling_rays import run_fixture
@@ -57,7 +62,7 @@ def main():
     if not (instance / 'saves/Demo_World/level.dat').is_file():
         raise AssertionError('Disposable world was not saved')
     report = {'schema': 1, 'platform': platform.platform(), 'architecture': platform.machine(),
-              'minecraft': '26.3', 'original_mod_sha256': digest, 'launcher_exit_code': run.returncode,
+              'minecraft': lab.VERSION, 'original_mod_sha256': digest, 'launcher_exit_code': run.returncode,
               'requested_backend': args.backend or 'pack_default', 'result': result, 'limits': ['Short report-context check, not FPS or physical M2 performance.',
                   'Graphics context is captured at recording start, not continuously monitored.',
                   'World files and full logs remain private.']}
diff --git a/tools/test_spawn_rules_parity.py b/tools/test_spawn_rules_parity.py
index 4050fae468..e71a032b5d 100644
--- a/tools/test_spawn_rules_parity.py
+++ b/tools/test_spawn_rules_parity.py
@@ -134,7 +134,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     entity_types = json.loads((resources / 'entity-types.json').read_text())
     types = sorted(t for t, v in entity_types.items() if 'attributes' in v and t.split(':')[1] not in SKIPPED)
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaSpawnRulesOracle.java'
diff --git a/tools/test_spawner_parity.py b/tools/test_spawner_parity.py
index 028f484426..b1637cf4e7 100644
--- a/tools/test_spawner_parity.py
+++ b/tools/test_spawner_parity.py
@@ -228,7 +228,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaNaturalSpawnOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/natural_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/spawner.rs',
diff --git a/tools/test_subtitle_parity.py b/tools/test_subtitle_parity.py
index 07e17da7b8..21b4c71759 100644
--- a/tools/test_subtitle_parity.py
+++ b/tools/test_subtitle_parity.py
@@ -112,7 +112,7 @@ def main():
     args = parser.parse_args()
     lock, jars, _ = base.verify_artifacts()
     libraries = baking.client_libraries()
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     build = lab.LOCAL / 'subtitle-parity'
     build.mkdir(parents=True, exist_ok=True)
     classes = build / 'classes'
diff --git a/tools/test_tab_list_parity.py b/tools/test_tab_list_parity.py
index 713da626c4..cdf32df65a 100644
--- a/tools/test_tab_list_parity.py
+++ b/tools/test_tab_list_parity.py
@@ -226,7 +226,7 @@ def main():
     lock, jars, _ = base.verify_artifacts()
     libraries = baking.client_libraries()
     build = lab.LOCAL / 'rust-tab-list-parity'; build.mkdir(parents=True, exist_ok=True)
-    resources = lab.LOCAL / 'horizon-client' / '26.3'
+    resources = lab.RESOURCES
     chosen = cases(args.count)
     inputs = build / 'inputs.jsonl'; inputs.write_text(''.join(json.dumps(c) + '\n' for c in chosen))
     classes = build / 'classes'; classes.mkdir(exist_ok=True)
diff --git a/tools/test_terrain_position.py b/tools/test_terrain_position.py
index af4c8b6420..ad081f7cc0 100644
--- a/tools/test_terrain_position.py
+++ b/tools/test_terrain_position.py
@@ -10,6 +10,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -59,7 +64,7 @@ def main():
             raise AssertionError(f"Position redirect changed upstream lookup: {key}")
     output = root / "dist/terrain-position-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
         "notes": ["Actual public full-data lookup inside Fabric with generated numeric column data.",
                   "Thirty owners span positive/negative origins and six detail levels; output digests and source fingerprints match.",
                   "The actual redirect method is checked in each mode; source column data remains unchanged.",
diff --git a/tools/test_terrain_read.py b/tools/test_terrain_read.py
index b829d572e0..67d0438503 100644
--- a/tools/test_terrain_read.py
+++ b/tools/test_terrain_read.py
@@ -10,6 +10,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -54,7 +59,7 @@ def main():
         print(json.dumps(report), flush=True)
     output = root / "dist/terrain-read-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "original_mod_sha256": original_sha256, "results": results,
         "notes": ["Actual game IOWorker under Fabric, with controlled cached blending-read futures.",
                   "DH worker interruption releases only its waiter; the shared future remains consumable.",
                   "Ordinary callers retain join behavior; completed values, cancellation and exception identity are checked.",
diff --git a/tools/test_tick_dedup.py b/tools/test_tick_dedup.py
index 4a518e062b..c08f643467 100644
--- a/tools/test_tick_dedup.py
+++ b/tools/test_tick_dedup.py
@@ -9,6 +9,11 @@ import shutil
 import subprocess
 import sys
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 try:
     from . import build_mod, build_pack
 except ImportError:
@@ -50,7 +55,7 @@ def main():
         raise AssertionError("Membership hook did not remove repeated entry allocation")
     output = root / "dist/tick-dedup-integration.json"
     output.write_text(json.dumps({"schema": 1, "platform": platform.platform(), "architecture": platform.machine(),
-        "minecraft": "26.3", "distant_horizons": "3.3.4", "results": results,
+        "minecraft": lab.VERSION, "distant_horizons": "3.3.4", "results": results,
         "notes": ["Actual publisher tick holder under Fabric, warmed with preallocated nodes and a reused action list.",
                   "Checks duplicate/null membership, enable/disable precedence, published iteration order and clear boundaries.",
                   "Only private membership checks change; action collections and traversal remain upstream.",
diff --git a/tools/test_trading_parity.py b/tools/test_trading_parity.py
index 2f66362fc0..13ef60880e 100644
--- a/tools/test_trading_parity.py
+++ b/tools/test_trading_parity.py
@@ -182,7 +182,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaTradingOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/trading_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/merchant.rs', lab.ROOT / 'crates/horizon-client/src/menu.rs']
diff --git a/tools/test_trial_spawner_parity.py b/tools/test_trial_spawner_parity.py
index 6fbcdbeee0..6fb79d9e11 100644
--- a/tools/test_trial_spawner_parity.py
+++ b/tools/test_trial_spawner_parity.py
@@ -192,7 +192,7 @@ def main():
     if args.prepare:
         lab.prepare()
     lock, jars, libraries = base.verify_artifacts()
-    resources = lab.LOCAL / 'horizon-client/26.3'
+    resources = lab.RESOURCES
     oracle = lab.ROOT / 'mods/horizon/src/test/java/dev/horizonlab/parity/VanillaNaturalSpawnOracle.java'
     sources = [oracle, Path(__file__), lab.ROOT / 'crates/horizon-client/examples/natural_spawn_fixture.rs',
                lab.ROOT / 'crates/horizon-client/src/mobs/trial_spawner.rs',
diff --git a/tools/test_world_spawn_parity.py b/tools/test_world_spawn_parity.py
index 4aae120009..23b1a47e07 100644
--- a/tools/test_world_spawn_parity.py
+++ b/tools/test_world_spawn_parity.py
@@ -56,7 +56,7 @@ NAME = 'world-spawn-parity'
 REPORT = 1891623539983467248
 RETRIES = 3
 SEEDS = [REPORT, 12345, -7046029254386353131, 987654321987, 4242, -1, 0x5DEECE66D, 20260607, 777, 0]
-RESOURCES = lab.LOCAL / 'horizon-client/26.3'
+RESOURCES = lab.RESOURCES
 
 
 def seeds(count):
diff --git a/tools/upgrade_world.py b/tools/upgrade_world.py
index 76619d8ecb..9db5e4517f 100755
--- a/tools/upgrade_world.py
+++ b/tools/upgrade_world.py
@@ -15,8 +15,13 @@ import sys
 import tempfile
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parent.parent
-SERVER = ROOT / '.local' / 'minecraft' / '26.3' / 'jars' / 'server.jar'
+SERVER = lab.GAME / 'jars' / 'server.jar'
 
 
 def free_port():
diff --git a/tools/vanilla_client.py b/tools/vanilla_client.py
index 41ae385563..64eb82691e 100644
--- a/tools/vanilla_client.py
+++ b/tools/vanilla_client.py
@@ -23,8 +23,13 @@ import uuid
 import zipfile
 from pathlib import Path
 
+try:
+    from . import lab
+except ImportError:
+    import lab
+
 ROOT = Path(__file__).resolve().parents[1]
-GAME = ROOT / ".local/minecraft/26.3"
+GAME = lab.GAME
 MAC = sys.platform == "darwin"
 # The natives of this machine's platform, and the shared libraries in them.
 NATIVES, LIBRARY_SUFFIX = ("natives-macos-arm64.jar", ".dylib") if MAC else ("natives-linux.jar", ".so")
@@ -124,8 +129,8 @@ def command(args):
            "-cp", os.pathsep.join(map(str, jars)), "net.minecraft.client.main.Main",
            "--username", args.name, "--uuid", offline_uuid(args.name).hex,
            "--accessToken", "0", "--offlineDeveloperMode",
-           "--version", "26.3", "--gameDir", str(args.game_dir),
-           "--assetsDir", str(assets), "--assetIndex", "34",
+           "--version", lab.VERSION, "--gameDir", str(args.game_dir),
+           "--assetsDir", str(assets), "--assetIndex", json.loads((GAME / "manifest.json").read_text())["assetIndex"]["id"],
            "--width", str(args.width), "--height", str(args.height)]
     if args.join:
         cmd += ["--quickPlayMultiplayer", args.join]
diff --git a/tools/vanilla_login.py b/tools/vanilla_login.py
index c077a0546d..fa2664c9d2 100644
--- a/tools/vanilla_login.py
+++ b/tools/vanilla_login.py
@@ -19,7 +19,10 @@ import time
 import uuid
 import zlib
 
-PROTOCOL = 777  # 26.3
+try:
+    from . import lab
+except ImportError:
+    import lab
 
 
 def offline_uuid(name):
@@ -101,7 +104,7 @@ def parse_varint(data, pos):
 
 def join(host, port, name, seconds):
     c = Connection(host, port)
-    c.send(0, varint(PROTOCOL) + string(host) + struct.pack('>H', port) + varint(2))
+    c.send(0, varint(lab.version_info()['protocol_version']) + string(host) + struct.pack('>H', port) + varint(2))
     c.send(0, string(name) + offline_uuid(name).bytes)
     # Login: compression, then login finished.
     while True: