Add probe early stop guards

tests/test_core_flow.py

@@ -15,6 +15,8 @@ from aituner.slo import RequestOutcome, summarize_evaluations
 from aituner.spec import Proposal, load_study_spec
 from aituner.store import StudyStore
 from aituner.trace import load_trace_requests, summarize_window
+from aituner.worker import _replay_requests
+from aituner.trace import TraceRequest
 
 
 def _write_study_assets(tmp_path: Path) -> Path:
@@ -668,6 +670,53 @@ class CoreFlowTests(unittest.TestCase):
             self.assertEqual(state.best_request_rate, 2.0)
             self.assertEqual(state.next_trial_index, 3)
 
+    def test_replay_requests_early_stops_when_slo_is_unrecoverable(self) -> None:
+        requests = [
+            TraceRequest(
+                row_id=f"r{i}",
+                arrival_s=0.0,
+                sampling_u=0.1 * i,
+                body={"model": "m", "messages": [{"role": "user", "content": "x"}]},
+                prompt_tokens_hint=8,
+                completion_tokens_hint=4,
+            )
+            for i in range(3)
+        ]
+
+        outcomes = [
+            RequestOutcome(
+                request_id="r0",
+                success=False,
+                ttft_ms=None,
+                tpot_ms=None,
+                prompt_tokens=8,
+                completion_tokens=4,
+                error="request_failed",
+            )
+        ]
+
+        def fake_run_one_request(*args, **kwargs):
+            return outcomes.pop(0)
+
+        def fake_evaluate(outcome: RequestOutcome):
+            return type("Eval", (), {"passed": outcome.success})()
+
+        with mock.patch("aituner.worker._run_one_request", side_effect=fake_run_one_request):
+            replayed, early_stopped, reason = _replay_requests(
+                requests,
+                base_url="http://127.0.0.1:8000",
+                timeout_s=1.0,
+                max_concurrency=1,
+                target_pass_rate=0.95,
+                max_lag_s=None,
+                max_elapsed_s=None,
+                evaluate_outcome=fake_evaluate,
+            )
+        self.assertTrue(early_stopped)
+        self.assertEqual(reason, "slo_pass_rate_unrecoverable")
+        self.assertEqual(len(replayed), 3)
+        self.assertEqual(replayed[1].error, "slo_pass_rate_unrecoverable")
+
 
 if __name__ == "__main__":
     unittest.main()