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fix(telemetry): serialize Pydantic BaseModel in _safe_json_serialize #4651

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fix(telemetry): serialize Pydantic BaseModel in _safe_json_serialize #4651

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9 changes: 6 additions & 3 deletions src/google/adk/telemetry/tracing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -116,11 +116,14 @@ def _safe_json_serialize(obj) -> str:
The JSON-serialized object string or <non-serializable> if the object cannot be serialized.
"""

def _default(o: Any) -> Any:
if isinstance(o, BaseModel):
return o.model_dump(mode='json')
return '<not serializable>'

try:
# Try direct JSON serialization first
return json.dumps(
obj, ensure_ascii=False, default=lambda o: '<not serializable>'
)
return json.dumps(obj, ensure_ascii=False, default=_default)
Comment on lines +119 to +126
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@gemini-code-assist gemini-code-assist bot Feb 28, 2026

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medium

This correctly handles Pydantic model serialization. To improve reusability and fix a similar issue in another file, I suggest extracting the _default logic into a module-level function, for example _pydantic_json_default.

# At module level in tracing.py
def _pydantic_json_default(o: Any) -> Any:
  if isinstance(o, BaseModel):
    return o.model_dump(mode='json')
  return '<not serializable>'

A nearly identical function, _safe_json_serialize_no_whitespaces in src/google/adk/telemetry/_experimental_semconv.py, still uses the old lambda and will also need this fix. Making the helper function module-level will allow you to import and reuse it there, avoiding code duplication.

Suggested change
def _default(o: Any) -> Any:
if isinstance(o, BaseModel):
return o.model_dump(mode='json')
return '<not serializable>'
try:
# Try direct JSON serialization first
return json.dumps(
obj, ensure_ascii=False, default=lambda o: '<not serializable>'
)
return json.dumps(obj, ensure_ascii=False, default=_default)
try:
# Try direct JSON serialization first
return json.dumps(obj, ensure_ascii=False, default=_pydantic_json_default)

except (TypeError, OverflowError):
return '<not serializable>'

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