Tool function with `BaseModel` argument does not work with Temporal

[DouweM]

Initial Checks

• I confirm that I'm using the latest version of Pydantic AI
• I confirm that I searched for my issue in https://github.com/pydantic/pydantic-ai/issues before opening this issue

Description

The object passed into the tool function is a dict instead of an instance of the annotated type:

  File "/home/DouweM/pydantic-ai/scratch/scratchpads/9c8b872dabe381702d009fe29745ee89/scratch9.py", line 21, in weather
    return f'The weather in {f.city} is sunny'
                             ^^^^^^
AttributeError: 'dict' object has no attribute 'city'

Example Code

import asyncio
import uuid

from pydantic import BaseModel
from temporalio import workflow
from temporalio.client import Client
from temporalio.worker import Worker

from pydantic_ai import Agent
from pydantic_ai.durable_exec.temporal import AgentPlugin, PydanticAIPlugin, TemporalAgent

agent = Agent('openai:gpt-4.1', name='test-tool')


class WeatherInput(BaseModel):
    city: str


@agent.tool_plain
def weather(f: WeatherInput) -> str:
    return f'The weather in {f.city} is sunny'


temporal_agent = TemporalAgent(agent)


@workflow.defn
class PydanticWorkflow:
    @workflow.run
    async def run(self, prompt: str) -> str:
        result = await temporal_agent.run(prompt)
        return result.output


async def main():
    client = await Client.connect(
        'localhost:7233',
        plugins=[PydanticAIPlugin()],
    )

    async with Worker(
        client,
        task_queue='pydantic-ai-task-queue',
        workflows=[PydanticWorkflow],
        plugins=[AgentPlugin(temporal_agent)],
    ):
        result = await client.execute_workflow(
            PydanticWorkflow.run,
            args=['What is the weather in Tokyo?'],
            id=f'pydantic-hello-world-workflow-{uuid.uuid4()}',
            task_queue='pydantic-ai-task-queue',
        )
        print(f'Result: {result}')


if __name__ == '__main__':
    asyncio.run(main())

Python, Pydantic AI & LLM client version

latest