Log legacy policy constraint drop failures

semantica/context/graph_schema.py

@@ -66,8 +66,11 @@ def create_decision_constraints(graph_store: GraphStore) -> None:
     try:
         # Drop legacy constraint when possible so versioned policies can coexist.
         graph_store.execute_query("DROP CONSTRAINT policy_id_unique IF EXISTS")
-    except Exception:
-        pass
+    except Exception as e:
+        get_logger(__name__).warning(
+            "Failed to drop legacy policy_id_unique constraint before policy "
+            f"versioning migration: {e}"
+        )
 
     try:
         graph_store.execute_query(

tests/context/test_graph_schema_logging.py

@@ -0,0 +1,22 @@
+"""Regression tests for graph schema migration logging behavior."""
+
+import logging
+from unittest.mock import Mock
+
+from semantica.context.graph_schema import create_decision_constraints
+
+
+def test_create_decision_constraints_logs_legacy_drop_failure(caplog):
+    graph_store = Mock()
+
+    def _execute_query(query, *args, **kwargs):
+        if "DROP CONSTRAINT policy_id_unique IF EXISTS" in query:
+            raise RuntimeError("drop failed")
+        return {"records": []}
+
+    graph_store.execute_query = Mock(side_effect=_execute_query)
+
+    with caplog.at_level(logging.WARNING):
+        create_decision_constraints(graph_store)
+
+    assert "Failed to drop legacy policy_id_unique constraint" in caplog.text