diff --git a/experiments/wp24b-gc/b2_patch.py b/experiments/wp24b-gc/b2_patch.py
new file mode 100644
index 0000000..c00d301
--- /dev/null
+++ b/experiments/wp24b-gc/b2_patch.py
@@ -0,0 +1,79 @@
+from pathlib import Path
+
+root = Path(__file__).resolve().parent
+main_path = root / "main.zig"
+build_path = root / "build.zig"
+
+main = main_path.read_text(encoding="utf-8")
+build = build_path.read_text(encoding="utf-8")
+
+replacements = [
+    (
+        "const BATCH_HEADROOM: u32 = 128 * 1024;\n",
+        "const BATCH_HEADROOM: u32 = 128 * 1024;\n"
+        "const NATIVE_GRACE_COLLECTIONS: u32 = 3;\n",
+    ),
+    (
+        "var installed = false;\nvar in_gc = false;\nvar closing_lua = false;\n",
+        "var installed = false;\nvar in_gc = false;\nvar closing_lua = false;\n"
+        "var active_g: u32 = 0;\n"
+        "var native_grace_collections: u32 = 0;\n",
+    ),
+    (
+        "    // Never carry private list state into another Lua global_State.\n"
+        "    if (sweeping and g != saved_g) {\n"
+        "        resetSweepState();\n"
+        "        collect_hook.callOriginal(.{L});\n"
+        "        return;\n"
+        "    }\n\n"
+        "    // If another module changed the birth byte during our split cycle,\n",
+        "    // Never carry private list state into another Lua global_State.\n"
+        "    if (sweeping and g != saved_g) {\n"
+        "        resetSweepState();\n"
+        "        collect_hook.callOriginal(.{L});\n"
+        "        return;\n"
+        "    }\n\n"
+        "    // B2: when a fresh Lua global_State appears (initial world entry,\n"
+        "    // /reload, logout/relog), keep the first three collections fully\n"
+        "    // native. This gives WoW ownership of the fragile state-rebuild\n"
+        "    // window before incremental rootgc sweeping resumes.\n"
+        "    if (active_g != g) {\n"
+        "        active_g = g;\n"
+        "        native_grace_collections = NATIVE_GRACE_COLLECTIONS;\n"
+        "    }\n"
+        "    if (native_grace_collections != 0) {\n"
+        "        native_grace_collections -= 1;\n"
+        "        collect_hook.callOriginal(.{L});\n"
+        "        return;\n"
+        "    }\n\n"
+        "    // If another module changed the birth byte during our split cycle,\n",
+    ),
+    (
+        "    reconnectSweep();\n    in_gc = false;\n\n    lua_close_hook.callOriginal(.{L});\n",
+        "    reconnectSweep();\n    in_gc = false;\n"
+        "    active_g = 0;\n"
+        "    native_grace_collections = 0;\n\n"
+        "    lua_close_hook.callOriginal(.{L});\n",
+    ),
+    (
+        'const version: [*:0]const u8 = "2.4-B1-gc-safe-sweep-abi";\n',
+        'const version: [*:0]const u8 = "2.4-B2-gc-safe-sweep-reload-guard";\n',
+    ),
+]
+
+for old, new in replacements:
+    count = main.count(old)
+    if count != 1:
+        raise SystemExit(f"main.zig patch anchor mismatch: expected 1, found {count}: {old[:80]!r}")
+    main = main.replace(old, new, 1)
+
+old_name = '.name = "weirdperformance_gc24b1",'
+new_name = '.name = "weirdperformance_gc24b2",'
+if build.count(old_name) != 1:
+    raise SystemExit("build.zig output-name anchor mismatch")
+build = build.replace(old_name, new_name, 1)
+
+main_path.write_text(main, encoding="utf-8")
+build_path.write_text(build, encoding="utf-8")
+
+print("B2 patch applied: new-global_State native grace = 3 GC cycles")