Python: [Bug]: OpenAI Responses streaming final response loses created_at, causing durabletask persistence warning

[madebygps]

Description

When using OpenAIChatClient from agent_framework.openai with stream=True, the final streamed response loses created_at.

More specifically:

• await agent.run(..., stream=False) returns an AgentResponse with created_at populated
• await agent.run(..., stream=True) followed by await stream.get_final_response() returns an AgentResponse with created_at=None

This becomes especially visible when using agent-framework-durabletask, because its durable entity path prefers stream=True first and then persists the final response. During persistence it logs:

Invalid or missing created_at value in durable agent state; defaulting to current UTC time, None

The durable flow still works because it falls back to the current UTC time, but the final streamed response metadata is wrong and the warning is noisy.

Minimal repro

import asyncio
import os
from azure.identity.aio import DefaultAzureCredential, get_bearer_token_provider
from agent_framework import Agent
from agent_framework.openai import OpenAIChatClient

async def main():
    async_credential = DefaultAzureCredential()
    token_provider = get_bearer_token_provider(
        async_credential,
        "https://cognitiveservices.azure.com/.default",
    )

    client = OpenAIChatClient(
        base_url=f"{os.environ['AZURE_OPENAI_ENDPOINT']}/openai/v1/",
        api_key=token_provider,
        model=os.environ["AZURE_OPENAI_CHAT_DEPLOYMENT"],
    )

    agent = Agent(
        name="Probe",
        instructions="Reply with ok only.",
        client=client,
    )

    non_stream = await agent.run("say ok")

    stream = await agent.run("say ok", stream=True)
    async for _ in stream:
        pass
    final = await stream.get_final_response()

    print("non_stream.created_at =", repr(non_stream.created_at))
    print("stream_final.created_at =", repr(final.created_at))

    await async_credential.close()

asyncio.run(main())

Observed output:

non_stream.created_at = '2026-04-18T12:48:06.000000Z'
stream_final.created_at = None

Additional validation

I also checked the raw final OpenAI streaming event. The final response.completed event still contains a populated timestamp on the embedded response object:

• event.type == "response.completed"
• event.response.created_at is populated

So the timestamp still exists in the raw streamed response, but it is not propagated into the final ChatResponse / AgentResponse.

Impact

• noisy warning in durabletask samples/apps
• incorrect metadata on final streamed responses
• fallback timestamp masks the issue, so behavior still appears to work while metadata is wrong

Code Sample

Error Messages / Stack Traces

Package Versions

agent-framework-core==1.0.0, agent-framework-openai==1.0.0, agent-framework-durabletask==1.0.0b260402

Python Version

3.12

Additional Context

No response