fix: catch ValueError in safe-JSON serializers for circular refs

Same fix applied to the matching helpers in google.adk.telemetry.

Close #5412

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 905265632

Author: GWeale

src/google/adk/models/lite_llm.py

@@ -543,7 +543,7 @@ def _safe_json_serialize(obj) -> str:
   try:
     # Try direct JSON serialization first
     return json.dumps(obj, ensure_ascii=False)
-  except (TypeError, OverflowError):
+  except (TypeError, ValueError, OverflowError):
     return str(obj)
 
 

src/google/adk/telemetry/_experimental_semconv.py

@@ -139,7 +139,7 @@ def _safe_json_serialize_no_whitespaces(obj) -> str:
         ensure_ascii=False,
         default=lambda o: '<not serializable>',
     )
-  except (TypeError, OverflowError):
+  except (TypeError, ValueError, OverflowError):
     return '<not serializable>'
 
 

src/google/adk/telemetry/tracing.py

@@ -128,7 +128,7 @@ def _safe_json_serialize(obj) -> str:
     return json.dumps(
         obj, ensure_ascii=False, default=lambda o: '<not serializable>'
     )
-  except (TypeError, OverflowError):
+  except (TypeError, ValueError, OverflowError):
     return '<not serializable>'
 
 

tests/unittests/models/test_litellm.py

@@ -45,6 +45,7 @@
 from google.adk.models.lite_llm import _model_response_to_generate_content_response
 from google.adk.models.lite_llm import _parse_tool_calls_from_text
 from google.adk.models.lite_llm import _redirect_litellm_loggers_to_stdout
+from google.adk.models.lite_llm import _safe_json_serialize
 from google.adk.models.lite_llm import _schema_to_dict
 from google.adk.models.lite_llm import _split_message_content_and_tool_calls
 from google.adk.models.lite_llm import _THOUGHT_SIGNATURE_SEPARATOR
@@ -680,6 +681,31 @@ def test_schema_to_dict_filters_none_enum_values():
   ]
 
 
+def test_safe_json_serialize_serializable_object():
+  assert _safe_json_serialize({"a": 1, "b": [2, 3]}) == '{"a": 1, "b": [2, 3]}'
+
+
+def test_safe_json_serialize_non_serializable_object_falls_back_to_str():
+  class _NotJsonable:
+
+    def __repr__(self):
+      return "<not jsonable>"
+
+  assert _safe_json_serialize(_NotJsonable()) == "<not jsonable>"
+
+
+def test_safe_json_serialize_circular_dict_falls_back_to_str():
+  obj = {}
+  obj["self"] = obj
+  assert isinstance(_safe_json_serialize(obj), str)
+
+
+def test_safe_json_serialize_circular_list_falls_back_to_str():
+  obj = []
+  obj.append(obj)
+  assert isinstance(_safe_json_serialize(obj), str)
+
+
 MULTIPLE_FUNCTION_CALLS_STREAM = [
     ModelResponseStream(
         choices=[

tests/unittests/telemetry/test_spans.py

@@ -25,6 +25,8 @@
 from google.adk.models.llm_request import LlmRequest
 from google.adk.models.llm_response import LlmResponse
 from google.adk.sessions.in_memory_session_service import InMemorySessionService
+from google.adk.telemetry._experimental_semconv import _safe_json_serialize_no_whitespaces
+from google.adk.telemetry.tracing import _safe_json_serialize
 from google.adk.telemetry.tracing import ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS
 from google.adk.telemetry.tracing import GCP_MCP_SERVER_DESTINATION_ID
 from google.adk.telemetry.tracing import trace_agent_invocation
@@ -1383,3 +1385,15 @@ def test_trace_tool_call_with_standard_error(
       mock.call('error.type', 'ValueError')
       in mock_span_fixture.set_attribute.call_args_list
   )
+
+
+def test_safe_json_serialize_circular_dict_returns_not_serializable():
+  obj = {}
+  obj['self'] = obj
+  assert _safe_json_serialize(obj) == '<not serializable>'
+
+
+def test_safe_json_serialize_no_whitespaces_circular_dict_returns_not_serializable():
+  obj = {}
+  obj['self'] = obj
+  assert _safe_json_serialize_no_whitespaces(obj) == '<not serializable>'