diff --git a/src/pipeline/gates.py b/src/pipeline/gates.py
index a7bd8062..a55df090 100644
--- a/src/pipeline/gates.py
+++ b/src/pipeline/gates.py
@@ -252,9 +252,27 @@ def check(self, recipe: RecipeSpec, ctx: GateContext) -> GateResult:
             return GateResult(self.name, False,
                               f"artifact {actual_mb:.1f} MB exceeds the "
                               f"declared {float(size_mb):.1f} MB budget")
-        return GateResult(self.name, True,
-                          f"{actual_mb:.1f} MB within the "
-                          f"{float(size_mb):.1f} MB budget")
+        detail = (f"{actual_mb:.1f} MB within the "
+                  f"{float(size_mb):.1f} MB budget")
+
+        budget_ms = perf.get("decode_ms_per_row")
+        if budget_ms is not None:
+            measured = (ctx.extra or {}).get("measured") or {}
+            ms = measured.get("decode_ms_per_row")
+            if ms is None:
+                return GateResult(
+                    self.name, False,
+                    "perf.decode_ms_per_row declared but never assumed: "
+                    "no measurement supplied — run tools/bench_decode.py "
+                    "or the CI decode bench")
+            if float(ms) > float(budget_ms):
+                return GateResult(
+                    self.name, False,
+                    f"decode {float(ms):.1f} ms/row exceeds the declared "
+                    f"{float(budget_ms):.1f} ms/row budget")
+            detail += (f"; decode {float(ms):.1f} ms/row within the "
+                       f"{float(budget_ms):.1f} ms/row budget")
+        return GateResult(self.name, True, detail)
 
 
 register_gate(QualityGate())
diff --git a/tests/test_pipeline_latency_budget.py b/tests/test_pipeline_latency_budget.py
new file mode 100644
index 00000000..93ddedf0
--- /dev/null
+++ b/tests/test_pipeline_latency_budget.py
@@ -0,0 +1,49 @@
+"""WO73/C3 — the decode-latency budget: perf.decode_ms_per_row declared
+in the index entry vs the measured value (ctx.extra["measured"]), which
+the bench tool (tools/bench_decode.py) or CI produces.
+"""
+
+from __future__ import annotations
+
+from pipeline.gates import BudgetGate, GateContext
+
+
+def _ctx(perf: dict, measured: dict | None) -> GateContext:
+    entry = {"size": 1_000_000, "perf": perf}
+    extra = {"index_entry": entry}
+    if measured is not None:
+        extra["measured"] = measured
+    return GateContext(extra=extra)
+
+
+def test_latency_within_budget_passes() -> None:
+    result = BudgetGate().check(
+        recipe=None,
+        ctx=_ctx({"size_mb": 10, "decode_ms_per_row": 500},
+                 {"decode_ms_per_row": 321.5}),
+    )
+    assert result.passed
+    assert "321.5" in result.detail
+
+
+def test_latency_over_budget_fails() -> None:
+    result = BudgetGate().check(
+        recipe=None,
+        ctx=_ctx({"size_mb": 10, "decode_ms_per_row": 100},
+                 {"decode_ms_per_row": 140.0}),
+    )
+    assert not result.passed
+    assert "exceeds" in result.detail
+
+
+def test_declared_latency_without_measurement_fails() -> None:
+    result = BudgetGate().check(
+        recipe=None, ctx=_ctx({"size_mb": 10, "decode_ms_per_row": 100}, None))
+    assert not result.passed
+    assert "never assumed" in result.detail
+
+
+def test_no_budgets_passes_with_note() -> None:
+    result = BudgetGate().check(recipe=None, ctx=_ctx({}, None))
+    assert result.passed
+    assert "no perf budgets declared" in result.detail
diff --git a/tools/bench_decode.py b/tools/bench_decode.py
new file mode 100644
index 00000000..d93211bf
--- /dev/null
+++ b/tools/bench_decode.py
@@ -0,0 +1,68 @@
+"""WO73/C3 — decode-latency bench: the measured half of the
+perf.decode_ms_per_row budget.
+
+Decodes a model's frozen conformance fixtures through the shipped
+decode mode (single-row greedy) and reports wall-clock ms/row. The
+number feeds BudgetGate via ctx.extra["measured"]; a budget is never
+assumed without it.
+
+Usage:
+    python tools/bench_decode.py <model-id> [--repeats 3] \
+        [--vectors conformance/<id>-vectors.json]
+
+Resolves the artifact through the index (sha256-verified), so the
+measured number always corresponds to the shipped bytes.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import statistics
+import sys
+import time
+from pathlib import Path
+
+REPO = Path(__file__).parent.parent
+sys.path.insert(0, str(REPO / "runtime" / "src"))
+
+from interscript_ml import Model  # noqa: E402
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("model_id")
+    ap.add_argument("--repeats", type=int, default=3)
+    ap.add_argument("--vectors", type=Path, default=None)
+    args = ap.parse_args()
+
+    vectors_path = args.vectors or (
+        REPO / "conformance" / f"{args.model_id}-vectors.json")
+    vectors = json.loads(vectors_path.read_text(encoding="utf-8"))
+    rows = vectors["vectors"]
+    if not rows:
+        sys.exit(f"no vectors in {vectors_path}")
+
+    model = Model.load(args.model_id)  # resolves via the index, verifies sha256
+
+    # warm-up (index fetch, ORT session init, first-graph allocation)
+    model.translate(rows[0]["src"])
+
+    per_row = []
+    for _ in range(args.repeats):
+        t0 = time.perf_counter()
+        for row in rows:
+            model.translate(row["src"])
+        per_row.append((time.perf_counter() - t0) * 1000 / len(rows))
+
+    print(json.dumps({
+        "model": args.model_id,
+        "rows": len(rows),
+        "repeats": args.repeats,
+        "decode_ms_per_row_median": round(statistics.median(per_row), 2),
+        "decode_ms_per_row_max": round(max(per_row), 2),
+    }))
+
+
+if __name__ == "__main__":
+    main()