Keep target topology explicit in delta projections

tests/test_core_flow.py

@@ -2928,8 +2928,24 @@ class CoreFlowTests(unittest.TestCase):
             self.assertEqual(next_action["knob_family"], "frontier-delta-projection")
             self.assertEqual(
                 next_action["config_patch"]["flag_patch"],
-                {"gpu-memory-utilization": 0.9},
+                {
+                    "tensor-parallel-size": 2,
+                    "data-parallel-size": 1,
+                    "gpu-memory-utilization": 0.9,
+                },
             )
+            proposal = build_harness_guided_proposal(context)
+            self.assertIsNotNone(proposal)
+            materialized_signature = materialized_effective_config_signature(
+                study=study,
+                state=state,
+                proposal=proposal,
+            )
+            tested_signatures = {
+                _effective_config_signature(study, trial.config_patch)
+                for trial in state.trials
+            }
+            self.assertNotIn(materialized_signature, tested_signatures)
             self.assertIsNone(build_harness_stop_proposal(context))
 
     def test_harness_validates_unmeasured_tp_frontier_before_runtime_refinement(self) -> None: