[3/n] Add vLLM mask reuse capture

examples/vllm_serve/create_fa4_source_witness.py

@@ -0,0 +1,57 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Create an exact FlashAttention source archive and its runtime witness."""
+
+from __future__ import annotations
+
+import argparse
+
+from modelopt.torch.sparsity.attention_sparsity.calibration.source_manifest import (
+    create_source_manifest_from_git_archive,
+)
+
+
+def _parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(
+        description="Create a Git-free runtime witness for one exact FlashAttention commit"
+    )
+    parser.add_argument("checkout", help="Clean FlashAttention Git checkout")
+    parser.add_argument("--expected-commit", required=True, help="Required 40-hex HEAD commit")
+    parser.add_argument("--archive-output", required=True, help="New exact git-archive tar path")
+    parser.add_argument(
+        "--manifest-output", required=True, help="New canonical source-witness JSON path"
+    )
+    return parser
+
+
+def main(argv: list[str] | None = None) -> int:
+    args = _parser().parse_args(argv)
+    generated = create_source_manifest_from_git_archive(
+        args.checkout,
+        expected_commit=args.expected_commit,
+        source_kind="flash-attention-4",
+        archive_output=args.archive_output,
+        manifest_output=args.manifest_output,
+    )
+    print(f"git_commit={generated.git_commit}")
+    print(f"git_tree={generated.git_tree}")
+    print(f"git_archive_sha256={generated.git_archive_sha256}")
+    print(f"source_manifest_sha256={generated.manifest_sha256}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())