diff --git a/scripts/check_sample_fixtures.py b/scripts/check_sample_fixtures.py
new file mode 100644
index 00000000..63603e4b
--- /dev/null
+++ b/scripts/check_sample_fixtures.py
@@ -0,0 +1,122 @@
+"""Check or refresh generated dataset sample fixtures.
+
+The check regenerates ``sample_std.json`` from each dataset's checked-in
+``sample_atif.json`` and compares it with the committed fixture.
+"""
+
+from __future__ import annotations
+
+import argparse
+import difflib
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+DATASETS_DIR = REPO_ROOT / "datasets"
+
+
+def dataset_dirs(names: list[str]) -> list[Path]:
+    if names:
+        dirs = [DATASETS_DIR / name for name in names]
+        for dataset_dir in dirs:
+            if not dataset_dir.is_dir():
+                raise SystemExit(f"error: unknown dataset '{dataset_dir.name}'")
+        return dirs
+    return sorted(path for path in DATASETS_DIR.iterdir() if path.is_dir())
+
+
+def render_jsonl(items: list[object]) -> str:
+    return "".join(json.dumps(item, ensure_ascii=True) + "\n" for item in items)
+
+
+def regenerate_sample_std(dataset_dir: Path) -> str:
+    sample_atif = dataset_dir / "sample_atif.json"
+    converter = dataset_dir / "atif_to_std.py"
+    if not sample_atif.exists() or not converter.exists():
+        raise FileNotFoundError(f"{dataset_dir.name} is missing sample_atif.json or atif_to_std.py")
+
+    env = os.environ.copy()
+    existing_pythonpath = os.environ.get("PYTHONPATH", "")
+    env["PYTHONPATH"] = os.pathsep.join(
+        entry for entry in [str(REPO_ROOT), existing_pythonpath] if entry
+    )
+    atif_rows = json.loads(sample_atif.read_text())
+    result = subprocess.run(
+        [sys.executable, str(converter)],
+        input=render_jsonl(atif_rows),
+        text=True,
+        capture_output=True,
+        check=True,
+        env=env,
+    )
+    std_rows = [json.loads(line) for line in result.stdout.splitlines() if line.strip()]
+    return json.dumps(std_rows, indent=2, ensure_ascii=True) + "\n"
+
+
+def check_dataset(dataset_dir: Path, update: bool) -> tuple[bool, str]:
+    sample_std = dataset_dir / "sample_std.json"
+    if not sample_std.exists():
+        return True, f"skip {dataset_dir.name}: missing sample_std.json"
+
+    regenerated = regenerate_sample_std(dataset_dir)
+    current = sample_std.read_text()
+    if regenerated == current:
+        return True, f"ok {dataset_dir.name}"
+
+    if update:
+        sample_std.write_text(regenerated)
+        sft_dir = dataset_dir / "sample_sft"
+        sft_warning = (
+            " (re-run agents/*/std_to_sft.py to refresh sample_sft/)"
+            if sft_dir.is_dir()
+            else ""
+        )
+        return True, f"updated {dataset_dir.name}{sft_warning}"
+
+    diff = "".join(
+        difflib.unified_diff(
+            current.splitlines(keepends=True),
+            regenerated.splitlines(keepends=True),
+            fromfile=f"{dataset_dir.name}/sample_std.json",
+            tofile=f"{dataset_dir.name}/sample_std.json regenerated",
+            n=3,
+        )
+    )
+    return False, f"drift {dataset_dir.name}\n{diff}"
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "--dataset",
+        action="append",
+        default=[],
+        help="Dataset directory name to check. May be repeated. Defaults to all datasets.",
+    )
+    parser.add_argument(
+        "--update",
+        action="store_true",
+        help="Rewrite stale sample_std.json files instead of failing.",
+    )
+    args = parser.parse_args()
+
+    ok = True
+    for dataset_dir in dataset_dirs(args.dataset):
+        try:
+            dataset_ok, message = check_dataset(dataset_dir, args.update)
+        except subprocess.CalledProcessError as exc:
+            dataset_ok = False
+            message = f"error {dataset_dir.name}: converter failed\n{exc.stderr}"
+        except Exception as exc:
+            dataset_ok = False
+            message = f"error {dataset_dir.name}: {exc}"
+        ok = ok and dataset_ok
+        print(message)
+    return 0 if ok else 1
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())