diff --git a/scripts/check_repository_hygiene.py b/scripts/check_repository_hygiene.py
new file mode 100644
index 00000000..5b5bfffb
--- /dev/null
+++ b/scripts/check_repository_hygiene.py
@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+BLOCKED_PREFIXES = (".codex-input/", ".codex-artifacts/")
+BLOCKED_SUFFIXES = (".db-wal", ".db-shm")
+LARGE_FILE_LIMIT = 20 * 1024 * 1024
+LARGE_FILE_ALLOWLIST_PREFIXES = (
+    "artifacts/evidence/accuracy/",
+    "docs/assets/",
+    "frontend/public/portfolio/",
+    "output/pdf/",
+)
+
+
+def tracked_files() -> list[str]:
+    result = subprocess.run(
+        ["git", "ls-files", "-z"],
+        cwd=ROOT,
+        check=True,
+        capture_output=True,
+    )
+    return [item for item in result.stdout.decode("utf-8").split("\0") if item]
+
+
+def main() -> int:
+    violations: list[str] = []
+    for relative in tracked_files():
+        normalized = relative.replace("\\", "/")
+        if normalized.startswith(BLOCKED_PREFIXES):
+            violations.append(f"{normalized}: local agent scratch must not be tracked")
+            continue
+        if normalized.endswith(BLOCKED_SUFFIXES):
+            violations.append(f"{normalized}: transient database state must not be tracked")
+            continue
+
+        path = ROOT / relative
+        if not path.is_file():
+            continue
+        size = path.stat().st_size
+        if size > LARGE_FILE_LIMIT and not normalized.startswith(
+            LARGE_FILE_ALLOWLIST_PREFIXES
+        ):
+            violations.append(
+                f"{normalized}: {size} bytes exceeds the "
+                f"{LARGE_FILE_LIMIT}-byte tracked-file budget"
+            )
+
+    if violations:
+        print("Repository hygiene violations:", file=sys.stderr)
+        for violation in violations:
+            print(f" - {violation}", file=sys.stderr)
+        return 1
+
+    print("Repository hygiene check passed.")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())