diff --git a/0-Core-Formalism/otom/tools/genetics/emit_selection_receipt.py b/0-Core-Formalism/otom/tools/genetics/emit_selection_receipt.py
new file mode 100644
index 00000000..fb4185be
--- /dev/null
+++ b/0-Core-Formalism/otom/tools/genetics/emit_selection_receipt.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+"""Emit a provenance-bearing selection-metrics receipt.
+
+Usage:
+  python emit_selection_receipt.py \
+    --fixture ../../data/fixtures/genetics/selection_metrics_fixture.json \
+    --out ../../out/receipts/selection_metrics_demo_v0.receipt.json
+
+The emitted receipt is suitable for plumbing tests only unless the fixture has
+real-data provenance. Synthetic fixtures must never promote genetics claims.
+"""
+
+from __future__ import annotations
+
+import argparse
+import hashlib
+import json
+from dataclasses import asdict
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Any
+
+from selection_metrics import (
+    TajimasDInput,
+    hudson_fst,
+    mass_number_selection_pressure,
+    tajimas_d,
+)
+
+
+RECEIPT_SCHEMA_VERSION = "selection-metrics-receipt/v0"
+
+
+def sha256_text(text: str) -> str:
+    return hashlib.sha256(text.encode("utf-8")).hexdigest()
+
+
+def load_fixture(path: Path) -> tuple[dict[str, Any], str]:
+    raw = path.read_text(encoding="utf-8")
+    return json.loads(raw), sha256_text(raw)
+
+
+def build_receipt(fixture: dict[str, Any], fixture_sha256: str, fixture_path: Path) -> dict[str, Any]:
+    tajima_input = TajimasDInput(**fixture["tajimas_d_input"])
+    fst_input = fixture["hudson_fst_input"]
+
+    tajima = tajimas_d(tajima_input)
+    fst = hudson_fst(
+        within_pairwise_differences=fst_input["within_pairwise_differences"],
+        between_pairwise_differences=fst_input["between_pairwise_differences"],
+    )
+    pressure = mass_number_selection_pressure(tajima, fst)
+
+    provenance = fixture.get("provenance", {})
+    promotion_policy = fixture.get("promotion_policy", {})
+    synthetic = provenance.get("source") == "synthetic_fixture"
+    may_promote = bool(promotion_policy.get("may_promote_claims", False)) and not synthetic
+
+    receipt = {
+        "schema": RECEIPT_SCHEMA_VERSION,
+        "receipt_kind": "selection_metrics_engineering_scaffold",
+        "claim_state": "ENGINEERING_SCAFFOLD",
+        "fixture": {
+            "path": str(fixture_path),
+            "fixture_id": fixture.get("fixture_id"),
+            "sha256": fixture_sha256,
+            "provenance": provenance,
+        },
+        "inputs": {
+            "tajimas_d_input": fixture["tajimas_d_input"],
+            "hudson_fst_input": fst_input,
+        },
+        "results": {
+            "tajimas_d": asdict(tajima),
+            "hudson_fst": asdict(fst),
+            "mass_number_selection_pressure_proxy": pressure,
+        },
+        "promotion": {
+            "may_promote_claims": may_promote,
+            "reason": (
+                "Synthetic fixture; validates code path only."
+                if synthetic
+                else promotion_policy.get("reason", "Promotion requires external review.")
+            ),
+        },
+        "generated_at_utc": datetime.now(timezone.utc).isoformat(),
+    }
+    receipt["receipt_sha256"] = sha256_text(json.dumps(receipt, sort_keys=True))
+    return receipt
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Emit selection metrics receipt JSON")
+    parser.add_argument("--fixture", required=True, type=Path, help="Path to fixture JSON")
+    parser.add_argument("--out", required=True, type=Path, help="Output receipt path")
+    args = parser.parse_args()
+
+    fixture, fixture_sha256 = load_fixture(args.fixture)
+    receipt = build_receipt(fixture, fixture_sha256, args.fixture)
+
+    args.out.parent.mkdir(parents=True, exist_ok=True)
+    args.out.write_text(json.dumps(receipt, indent=2, sort_keys=True) + "\n", encoding="utf-8")
+    print(json.dumps({"wrote": str(args.out), "receipt_sha256": receipt["receipt_sha256"]}, indent=2))
+
+
+if __name__ == "__main__":
+    main()