Gate GMU climb on measured improvement

tests/test_core_flow.py

@@ -2594,10 +2594,9 @@ class CoreFlowTests(unittest.TestCase):
             )
             self.assertNotIn("tensor-parallel-size", proposal.config_patch.flag_patch)
 
-    def test_harness_continues_gpu_mem_util_after_tied_same_topology_probe(self) -> None:
-        """After adjacent topology validation, gpu-memory-utilization should hill-climb
-        on the incumbent topology even if an earlier gmu step tied the incumbent and
-        did not become state.best_trial_id."""
+    def test_harness_stops_gpu_mem_util_climb_after_tied_same_topology_probe(self) -> None:
+        """A same-topology gpu-memory-utilization probe must improve per-GPU rate before
+        the hill-climb continues; launch success alone is not evidence to keep climbing."""
         with tempfile.TemporaryDirectory() as tmp:
             tmp_path = Path(tmp)
             study_path = _write_study_assets(
@@ -2711,11 +2710,14 @@ class CoreFlowTests(unittest.TestCase):
                 window_summary={"prompt_tokens_p95": 1500},
                 state=state,
             )
-            proposal = build_harness_guided_proposal(context)
-            self.assertIsNotNone(proposal)
-            self.assertEqual(
-                proposal.config_patch.flag_patch,
+            candidates = context["experiment_plan"]["candidate_actions"]
+            self.assertNotIn(
                 {"tensor-parallel-size": 2, "gpu-memory-utilization": 0.94},
+                [
+                    item["config_patch"]["flag_patch"]
+                    for item in candidates
+                    if item["knob_family"] == "gpu-memory-utilization"
+                ],
             )
 
     def test_harness_validates_unmeasured_tp_frontier_before_runtime_refinement(self) -> None: