fix(ontology): handle string attributes from LLM response to prevent TypeError crash

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/graph_builder.py

@@ -240,7 +240,7 @@ class GraphBuilderService:
             attrs = {"__doc__": description}
             annotations = {}
 
-            for attr_def in entity_def.get("attributes", []):
+            for attr_def in GraphBuilderService._normalize_entity_attributes(entity_def.get("attributes", [])):
                 attr_name = safe_attr_name(attr_def["name"])
                 attr_desc = attr_def.get("description", attr_name)
                 attrs[attr_name] = Field(description=attr_desc, default=None)
@@ -260,7 +260,7 @@ class GraphBuilderService:
             attrs = {"__doc__": description}
             annotations = {}
 
-            for attr_def in edge_def.get("attributes", []):
+            for attr_def in GraphBuilderService._normalize_entity_attributes(edge_def.get("attributes", [])):
                 attr_name = safe_attr_name(attr_def["name"])
                 attr_desc = attr_def.get("description", attr_name)
                 attrs[attr_name] = Field(description=attr_desc, default=None)
@@ -430,3 +430,14 @@ class GraphBuilderService:
         """Delete graph"""
         self._graph.delete_graph(graph_id)
 
+    @staticmethod
+    def _normalize_entity_attributes(attributes: list) -> list:
+        """Ensure each attribute item is a dict; convert strings to minimal dicts."""
+        result = []
+        for attr in attributes:
+            if isinstance(attr, str):
+                result.append({"name": attr, "type": "text", "description": attr})
+            elif isinstance(attr, dict):
+                result.append(attr)
+        return result
+

backend/app/services/ontology_generator.py

@@ -201,6 +201,9 @@ class OntologyGenerator:
             max_tokens=8192
         )
 
+        # Normalise string attributes before validation
+        result = OntologyGenerator._normalize_ontology_attributes(result)
+
         # Validate and post-process
         result = self._validate_and_process(result)
 
@@ -264,6 +267,29 @@ Based on the content above, design entity types and relationship types suitable
 
         return message
 
+    @staticmethod
+    def _normalize_ontology_attributes(ontology: dict) -> dict:
+        """Normalize string attributes in LLM-generated ontology to dicts (in-place).
+
+        Handles both ``entities``/``edges`` keys (used in tests) and
+        ``entity_types``/``edge_types`` keys (used in production LLM output).
+        """
+        for key in ("entities", "entity_types"):
+            for entity in ontology.get(key, []):
+                entity["attributes"] = [
+                    attr if isinstance(attr, dict)
+                    else {"name": attr, "type": "text", "description": attr}
+                    for attr in entity.get("attributes", [])
+                ]
+        for key in ("edges", "edge_types"):
+            for edge in ontology.get(key, []):
+                edge["attributes"] = [
+                    attr if isinstance(attr, dict)
+                    else {"name": attr, "type": "text", "description": attr}
+                    for attr in edge.get("attributes", [])
+                ]
+        return ontology
+
     def _validate_and_process(self, result: Dict[str, Any]) -> Dict[str, Any]:
         """Validate and post-process the result"""
 

backend/tests/test_ontology_attributes.py

@@ -0,0 +1,36 @@
+def test_graph_builder_normalizes_string_attributes():
+    """_normalize_entity_attributes converts strings to dicts without crashing."""
+    from app.services.graph_builder import GraphBuilderService
+
+    mixed = ["name", "age", {"name": "email", "type": "text", "description": "Email"}]
+    result = GraphBuilderService._normalize_entity_attributes(mixed)
+
+    assert all(isinstance(a, dict) for a in result)
+    assert result[0] == {"name": "name", "type": "text", "description": "name"}
+    assert result[1] == {"name": "age", "type": "text", "description": "age"}
+    assert result[2]["name"] == "email"
+
+
+def test_graph_builder_normalize_empty():
+    """Empty attribute list returns empty list."""
+    from app.services.graph_builder import GraphBuilderService
+    assert GraphBuilderService._normalize_entity_attributes([]) == []
+
+
+def test_ontology_generator_normalizes_string_attributes():
+    """_normalize_ontology_attributes converts string attrs in entities and edges."""
+    from app.services.ontology_generator import OntologyGenerator
+
+    raw = {
+        "entities": [{"name": "Person", "description": "A person", "attributes": ["name", "age"]}],
+        "edges": [{"name": "KNOWS", "description": "Knows", "attributes": ["since"]}],
+    }
+    result = OntologyGenerator._normalize_ontology_attributes(raw)
+
+    entity_attrs = result["entities"][0]["attributes"]
+    assert all(isinstance(a, dict) for a in entity_attrs)
+    assert entity_attrs[0] == {"name": "name", "type": "text", "description": "name"}
+
+    edge_attrs = result["edges"][0]["attributes"]
+    assert all(isinstance(a, dict) for a in edge_attrs)
+    assert edge_attrs[0] == {"name": "since", "type": "text", "description": "since"}