Relax lower-frontier delta projection gate

src/aituner/harness.py

@@ -46,6 +46,7 @@ _ADMISSION_PRESSURE_STEP_UP = 1.5
 _FRONTIER_DELTA_MIN_ABS_GAIN = 0.02
 _FRONTIER_DELTA_MIN_REL_GAIN = 0.03
 _FRONTIER_DELTA_PROJECTED_INCUMBENT_FLOOR = 0.98
+_FRONTIER_DELTA_TARGET_BASELINE_COMPETITIVE_FLOOR = 0.75
 
 
 def build_harness_context(
@@ -1746,8 +1747,26 @@ def _frontier_delta_projection_actions(
                     )
                 )
                 continue
+            if (
+                target_parallel < source_parallel
+                and delta["baseline_rate_per_gpu"] > 0
+                and target_rate + EPSILON
+                < delta["baseline_rate_per_gpu"]
+                * _FRONTIER_DELTA_TARGET_BASELINE_COMPETITIVE_FLOOR
+            ):
+                blocked_candidates.append(
+                    _blocked_candidate(
+                        action_id=action_id,
+                        knob_family="frontier-delta-projection",
+                        config_patch={"env_patch": {}, "flag_patch": patch},
+                        blocked_reason="blocked_target_anchor_not_competitive_with_source_baseline",
+                        effective_config_signature=signature,
+                    )
+                )
+                continue
             if (
                 incumbent_rate > 0
+                and target_parallel >= source_parallel
                 and target_rate + source_gain + EPSILON
                 < incumbent_rate * _FRONTIER_DELTA_PROJECTED_INCUMBENT_FLOOR
             ):

tests/test_core_flow.py

@@ -2801,8 +2801,8 @@ class CoreFlowTests(unittest.TestCase):
                         trial_id="trial-0001",
                         status="completed",
                         parallel_size=2,
-                        best_request_rate=3.466,
-                        best_request_rate_per_gpu=1.733,
+                        best_request_rate=2.9,
+                        best_request_rate_per_gpu=1.45,
                         config_patch={"env_patch": {}, "flag_patch": {}},
                     ),
                     TrialSummary(