AsyncModels.generate_content crashes with cannot pickle '_asyncio.Future' when config is a GenerateContentConfig object containing an MCP ClientSession tool

[SagarTubr]

Environment

• google-genai: 2.9.0
• mcp: 1.28.1
• Python: 3.12.13

The issue

Passing a live MCP ClientSession as a tool works when config is a dict, but the same settings passed as a GenerateContentConfig object raise TypeError: cannot pickle '_asyncio.Future' object.

In AsyncModels.generate_content, the config is deep-copied before MCP sessions are extracted — google/genai/models.py (2.9.0)

Steps to reproduce

1. Create a live MCP ClientSession and pass it as a tool to aio.models.generate_content, with config as a GenerateContentConfig object:
   config=types.GenerateContentConfig(tools=[session]).
2. The call raises TypeError: cannot pickle '_asyncio.Future' object before any network request.
3. Pass the same settings as a dict instead — config={"tools": [session]} — and it works (session is extracted, request proceeds normally).

[Venkaiahbabuneelam]

Hi @SagarTubr, Thanks for reaching out us!
To help us better understand the issue, could you please provide a reproducible code snippet along with the error logs?
Thanks

[SagarTubr]

Hi @Venkaiahbabuneelam

Sure! here is the code snippet and the error traceback, fails at generate_content()

async with mcp_client:
        response = await gemini_client.aio.models.generate_content(
            model="gemini-2.5-flash",
            contents=input,
            config=genai.types.GenerateContentConfig(
                temperature=0,
                tools=[mcp_client.session],
                system_instruction=system_prompt,
                response_mime_type="application/json",
                response_json_schema=ResponseSchema.model_json_schema(),
            ),
        )

Error traceback

File ".../google/genai/models.py", line 8556, in generate_content
      parsed_config = config.model_copy(deep=True)
  File ".../pydantic/main.py", line 412, in model_copy
      copied = self.__deepcopy__() if deep else self.__copy__()
  File ".../pydantic/main.py", line 994, in __deepcopy__
      _object_setattr(m, '__dict__', deepcopy(self.__dict__, memo=memo))
  File ".../copy.py", line 136, in deepcopy
      y = copier(x, memo)
  File ".../copy.py", line 151, in deepcopy
      rv = reductor(4)
  TypeError: cannot pickle '_asyncio.Future' object

Hope this helps, let me know if you need more information.
Thanks!

[Venkaiahbabuneelam]

Hi @SagarTubr, Thank you for the detailed explanation and provided by code snippet, We have successfully reproduced the error you are experiencing and will file an internal bug report.

Thanks