Tighten topology and auto-high validation

src/aituner/harness.py

@@ -1755,31 +1755,23 @@ def _parallel_size_can_vary(study: StudySpec) -> bool:
     effective_gpu_count = _effective_gpu_count(study)
     if effective_gpu_count <= 1:
         return False
-    constraints = study.engine.topology_constraints
-    if constraints is not None and constraints.allowed_tp_dp_products:
-        legal_products = {
-            item for item in constraints.allowed_tp_dp_products if item <= effective_gpu_count
-        }
-        return len(legal_products) > 1
-    if constraints is not None:
-        tp_values = (
-            constraints.allowed_tensor_parallel_sizes
-            if constraints.allowed_tensor_parallel_sizes
-            else [1, 2, 4, 8]
-        )
-        dp_values = (
-            constraints.allowed_data_parallel_sizes
-            if constraints.allowed_data_parallel_sizes
-            else [1]
-        )
-        products = {
-            int(tp) * int(dp)
-            for tp in tp_values
-            for dp in dp_values
-            if int(tp) > 0 and int(dp) > 0 and int(tp) * int(dp) <= effective_gpu_count
-        }
-        return len(products) > 1
-    return True
+    base = _normalized_topology_flags(study.engine.base_flags)
+    legal = _legal_topology_points(
+        study,
+        current_tp=int(base["tensor-parallel-size"]),
+        current_dp=int(base["data-parallel-size"]),
+        current_ep=int(base["expert-parallel-size"]),
+        current_enable_ep=bool(base["enable-expert-parallel"]),
+    )
+    signatures: set[str] = set()
+    for point in legal:
+        patch = _topology_patch(study, point)
+        flags = {**study.engine.base_flags, **patch}
+        normalized = _normalized_topology_flags(flags)
+        if any(normalized.get(key) != point.get(key) for key in point):
+            continue
+        signatures.add(_config_signature({"env_patch": {}, "flag_patch": patch}))
+    return len(signatures) > 1
 
 
 def _score_topology_candidate(

src/aituner/store.py

@@ -381,6 +381,9 @@ def resolve_auto_high_search(
         return search, evidence
     ceiling = min(float(policy.max_sampling_u), 1.0, float(trace_max_sampling_u))
     evidence["effective_ceiling"] = ceiling
+    if ceiling < float(search.low):
+        evidence["reason"] = "auto_high_ceiling_below_search_low"
+        return search, evidence
     if abs(float(search.high) - ceiling) <= 1e-12:
         evidence["reason"] = "search_high_already_at_auto_high_ceiling"
         return search, evidence