test: pin the expiry window and close settlement review gaps

tests/unit/test_retry.py

@@ -585,6 +585,22 @@ class TestCancellationSettlement:
         await mw(_REQ)
         assert (await limiter.source_stats("a")).tpm_used == 0
 
+    async def test_circuit_open_rejection_settles_zero_end_to_end(self):
+        """S1 端到端: 开路拒绝的 pick 预扣后按 0 结算, 不给 tpm_used 增加任何量。"""
+        clock = FakeClock()
+        script = [TransientError(str(i)) for i in range(9)]
+        mw, limiter, *_ = _harness(
+            [_src("a", max_concurrency=1, tpm=10000, est_tokens=400)],
+            script,
+            clock=clock,
+            max_attempts=99,
+        )
+        # 3 次瞬时失败后 a 开路 → 第 4 次 pick 被拒绝
+        with pytest.raises(CircuitOpenError):
+            await mw(_REQ)
+        # 三次瞬时失败各保留 est = 1200; 开路那次 pick 若漏了 settle(0) 会再 +400
+        assert (await limiter.source_stats("a")).tpm_used == 1200
+
 
 class TestCancellation:
     async def test_cancel_mid_flight_releases_permit(self):