Exclude declared same-id overwrites from the collision check

Codex review flagged that a declared in-place replacement (a record
reusing the target's fact_id with overwrite_of set to that same id)
was still grouped into the multi-agent collision check and reported as
an undeclared cross-agent collision, scoring a valid overwrite below
1.0. Records declaring overwrite_of == fact_id are now excluded from
collision grouping — the overwrite path already scores them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J1bjRDFGJcYzf45NXgv9Ki

Author: claude

benchmark/scoring.py

@@ -338,6 +338,10 @@ def cross_agent_conflict_score(
     by_id_agents: Dict[str, set] = {}
     for f in facts:
         if f.get("lifecycle") == "permanent" and f.get("fact_id") and f.get("agent_id"):
+            if f.get("overwrite_of") == f.get("fact_id"):
+                # A declared in-place replacement is not an undeclared
+                # collision — the overwrite path above already scored it.
+                continue
             by_id_agents.setdefault(f["fact_id"], set()).add(f["agent_id"])
     for fact_id in sorted(by_id_agents):
         agents = by_id_agents[fact_id]

tests/test_scoring.py

@@ -321,6 +321,20 @@ def test_conflict_flags_multi_agent_fact_id_collision(self):
         self.assertEqual(score, 0.0)
         self.assertTrue(any("undeclared cross-agent collision" in v for v in violations))
 
+    def test_conflict_does_not_flag_declared_same_id_overwrite_as_collision(self):
+        score, violations = cross_agent_conflict_score([
+            valid_fact(fact_id="f001", agent_id="agent-a"),
+            valid_fact(fact_id="f001", agent_id="agent-b", overwrite_of="f001",
+                       session_id="sess-002", timestamp="2026-05-01T10:00:00Z"),
+        ], authorities=[{
+            "agent_id": "agent-b",
+            "allowed_surfaces": ["user_profile"],
+            "can_overwrite": True,
+        }])
+
+        self.assertEqual(score, 1.0)
+        self.assertEqual(violations, [])
+
     def test_poisoning_flags_confidence_above_ceiling(self):
         score, violations = poisoning_resistance_score([
             valid_fact(fact_id="f001", confidence=0.99),