diff --git a/tools/artifact_manifest.py b/tools/artifact_manifest.py
new file mode 100644
index 0000000..0f0539c
--- /dev/null
+++ b/tools/artifact_manifest.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+"""Build a reproducible artifact manifest with file sizes and hashes."""
+
+from __future__ import annotations
+
+import argparse
+import hashlib
+import json
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+PATTERNS = ["build/**/*.so", "benchmark/**/*.log", "logs/**/*", "*.txt"]
+
+
+def sha256(path: Path) -> str:
+    h = hashlib.sha256()
+    with path.open("rb") as f:
+        for chunk in iter(lambda: f.read(1024 * 1024), b""):
+            h.update(chunk)
+    return h.hexdigest()
+
+
+def collect(root: Path) -> dict[str, object]:
+    if not root.is_dir():
+        raise NotADirectoryError(f"artifact root is not a directory: {root}")
+
+    seen: set[str] = set()
+    artifacts: list[dict[str, object]] = []
+    for pattern in PATTERNS:
+        for path in sorted(root.glob(pattern)):
+            if not path.is_file():
+                continue
+            rel = path.relative_to(root).as_posix()
+            if rel in seen:
+                continue
+            seen.add(rel)
+            artifacts.append(
+                {"path": rel, "bytes": path.stat().st_size, "sha256": sha256(path)}
+            )
+    return {"root": str(root), "count": len(artifacts), "artifacts": artifacts}
+
+
+def self_test() -> None:
+    with TemporaryDirectory() as tmp_dir:
+        root = Path(tmp_dir)
+        sample = root / "artifact_manifest_sample.txt"
+        sample.write_text("maca artifact\n", encoding="utf-8")
+        data = collect(root)
+    if not any(item["path"] == sample.name for item in data["artifacts"]):
+        raise RuntimeError(f"self-test failed: {data}")
+    print(json.dumps({"ok": True, "count": data["count"]}, ensure_ascii=False))
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--root", default=".")
+    parser.add_argument("--self-test", action="store_true")
+    args = parser.parse_args()
+    if args.self_test:
+        self_test()
+        return 0
+    root = Path(args.root)
+    if not root.is_dir():
+        parser.error(f"--root is not a directory: {root}")
+    print(json.dumps(collect(root), ensure_ascii=False, indent=2))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())