InvalidArgument: 400 Request contains an invalid argument

Gemini API
1

I keep getting this error nowadays. Any idea why?

2025-03-21 16:12:03 WARNING  Retrying langchain_google_vertexai.chat_models._acompletion_with_retry.<locals>._completion_with_retry_inner in 4.0 seconds as it raised InvalidArgument: 400 Request contains an invalid argument..
2025-03-21 16:12:07 WARNING  Retrying langchain_google_vertexai.chat_models._acompletion_with_retry.<locals>._completion_with_retry_inner in 4.0 seconds as it raised InvalidArgument: 400 Request contains an invalid argument..
2025-03-21 16:12:11 WARNING  Retrying langchain_google_vertexai.chat_models._acompletion_with_retry.<locals>._completion_with_retry_inner in 4.0 seconds as it raised InvalidArgument: 400 Request contains an invalid argument..
2025-03-21 16:12:16 WARNING  Retrying langchain_google_vertexai.chat_models._acompletion_with_retry.<locals>._completion_with_retry_inner in 8.0 seconds as it raised InvalidArgument: 400 Request contains an invalid argument..
2025-03-21 16:12:24 WARNING  Retrying langchain_google_vertexai.chat_models._acompletion_with_retry.<locals>._completion_with_retry_inner in 10.0 seconds as it raised InvalidArgument: 400 Request contains an invalid argument..
Traceback (most recent call last):
  File "/home/khteh/.local/lib/python3.12/site-packages/google/api_core/grpc_helpers_async.py", line 77, in wait_for_connection
    await self._call.wait_for_connection()
  File "/home/khteh/.local/lib/python3.12/site-packages/grpc/aio/_call.py", line 659, in wait_for_connection
    await self._raise_for_status()
  File "/home/khteh/.local/lib/python3.12/site-packages/grpc/aio/_call.py", line 272, in _raise_for_status
    raise _create_rpc_error(
grpc.aio._call.AioRpcError: <AioRpcError of RPC that terminated with:
	status = StatusCode.INVALID_ARGUMENT
	details = "Request contains an invalid argument."
	debug_error_string = "UNKNOWN:Error received from peer ipv4:74.125.68.95:443 {grpc_message:"Request contains an invalid argument.", grpc_status:3, created_time:"2025-03-21T16:12:34.945102813+08:00"}"
>

Code snippet in question:

    async for event in agent.astream(
        #{"messages": [{"role": "user", "content": messages}]},
        {"messages": [("user", messages)]},
        stream_mode="values",
        config=config, # This is needed by Checkpointer
    ):
        event["messages"][-1].pretty_print()