Throw err when work with ag-ui-adk #5026
Description
🔴 Required Information
The latest version, both v1 and v2-alp
Describe the Bug:
{
"type": "RUN_ERROR",
"message": "Event encoding failed: Unable to serialize unknown type: <class 'google.adk.tools.function_tool.FunctionTool'>",
"code": "ENCODING_ERROR"
}
full trackback:
{
"textPayload": "❌ Event encoding error: Unable to serialize unknown type: <class 'google.adk.tools.function_tool.FunctionTool'>\nTraceback (most recent call last):\n File \"/layers/google.python.uv/uv-dependencies/.venv/lib/python3.13/site-packages/ag_ui_adk/endpoint.py\", line 148, in event_generator\n encoded = encoder.encode(event)\n File \"/layers/google.python.uv/uv-dependencies/.venv/lib/python3.13/site-packages/ag_ui/encoder/encoder.py\", line 26, in encode\n return self._encode_sse(event)\n ~~~~~~~~~~~~~~~~^^^^^^^\n File \"/layers/google.python.uv/uv-dependencies/.venv/lib/python3.13/site-packages/ag_ui/encoder/encoder.py\", line 32, in _encode_sse\n return f\"data: {event.model_dump_json(by_alias=True, exclude_none=True)}\\n\\n\"\n ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n File \"/layers/google.python.uv/uv-dependencies/.venv/lib/python3.13/site-packages/pydantic/main.py\", line 528, in model_dump_json\n return self.__pydantic_serializer__.to_json(\n ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^\n self,\n ^^^^^\n ...<13 lines>...\n serialize_as_any=serialize_as_any,\n ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n ).decode()\n ^\npydantic_core._pydantic_core.PydanticSerializationError: Unable to serialize unknown type: <class 'google.adk.tools.function_tool.FunctionTool'>",
"insertId": "xxxxxxxxx",
"httpRequest": {},
"resource": {
"type": "cloud_run_revision",
"labels": {
"location": "us-central1",
"revision_name": "xxxxxxxxxxxxxx",
"configuration_name": "xxxxxxxxxxxx",
"project_id": "xxxxxxxxxxxx",
"service_name": "xxxxxx"
}
},
"timestamp": "2026-03-27T11:28:33.823288Z",
"severity": "ERROR",
"labels": {
"python_logger": "ag_ui_adk.endpoint",
"instanceId": "008c15ff08665ddd84585a93dad34184dcaadd76cb011a55dbd282d83de55894dfb8d8f27a44206112e4dc07ae385b6b7a9da0d50666b961db465929b6d4225180ee528808a26f939062402ae5"
},
"logName": "projects/xxxxxxxxxxxxxxxxxx/logs/run.googleapis.com%2Fstderr",
"sourceLocation": {
"file": "/layers/google.python.uv/uv-dependencies/.venv/lib/python3.13/site-packages/ag_ui_adk/endpoint.py",
"line": "153",
"function": "event_generator"
},
"receiveTimestamp": "2026-03-27T11:28:33.986197905Z",
"errorGroups": [
{
"id": "xxxxxxxxxxxxxxxxxxxx"
}
]
}
Steps to Reproduce:
Please provide a numbered list of steps to reproduce the behavior:
- Install '...'
- Run '....'
- Open '....'
- Provide error or stacktrace
Expected Behavior:
A clear and concise description of what you expected to happen.
Observed Behavior:
What actually happened? Include error messages or crash stack traces here.
Environment Details:
- ADK Library Version (pip show google-adk):
- Desktop OS:** [e.g., macOS, Linux, Windows]
- Python Version (python -V):
Model Information:
- Are you using LiteLLM: Yes/No
- Which model is being used: (e.g., gemini-2.5-pro)
🟡 Optional Information
Providing this information greatly speeds up the resolution process.
Regression:
Did this work in a previous version of ADK? If so, which one?
Logs:
Please attach relevant logs. Wrap them in code blocks (```) or attach a
text file.
// Paste logs here
Screenshots / Video:
If applicable, add screenshots or screen recordings to help explain
your problem.
Additional Context:
Add any other context about the problem here.
Minimal Reproduction Code:
Please provide a code snippet or a link to a Gist/repo that isolates the issue.
// Code snippet hereHow often has this issue occurred?:
- Always (100%)
- Often (50%+)
- Intermittently (<50%)
- Once / Rare