Python: [Bug]: OpenAIChatCompletionClient exception

[unbuilt]

Description

While build hosted agent with Agent Framework,
When use OpenAIChatCompletionClient, to call gpt-4.1 model, the client may raise exception like:

14:18:44.955 [stream] stderr 2026-05-08 06:18:44,954 ERROR azure.ai.agentserver: Handler raised after response.created (response_id=caresp_fff952c7a059d512006yfPdEk7uoALbythPrQXStTjx2tQ2HxF)
14:18:44.955 [stream] stderr Traceback (most recent call last):
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework_openai/_chat_completion_client.py", line 525, in _stream
14:18:44.955 [stream] stderr yield self._parse_response_update_from_openai(chunk)
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework_openai/_chat_completion_client.py", line 735, in _parse_response_update_from_openai
14:18:44.955 [stream] stderr if text_content := self._parse_text_from_openai(choice):
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework_openai/_chat_completion_client.py", line 776, in _parse_text_from_openai
14:18:44.955 [stream] stderr if message.content:
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr AttributeError: 'NoneType' object has no attribute 'content'
14:18:44.955 [stream] stderr
14:18:44.955 [stream] stderr The above exception was the direct cause of the following exception:
14:18:44.955 [stream] stderr
14:18:44.955 [stream] stderr Traceback (most recent call last):
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/azure/ai/agentserver/responses/hosting/_orchestrator.py", line 1243, in _process_handler_events
14:18:44.955 [stream] stderr async for raw in _iter_with_winddown(handler_iterator, ctx.cancellation_signal):
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/azure/ai/agentserver/responses/hosting/_orchestrator.py", line 156, in _iter_with_winddown
14:18:44.955 [stream] stderr item = await aiter.anext()
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/azure/ai/agentserver/responses/hosting/_routing.py", line 347, in _await_and_normalize
14:18:44.955 [stream] stderr async for event in self._normalize_handler_result(inner):
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework_foundry_hosting/_responses.py", line 341, in _handle_inner_agent
14:18:44.955 [stream] stderr async for update in self._agent.run(stream=True, **run_kwargs): # type: ignore[reportUnknownMemberType]
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework/_types.py", line 3024, in anext
14:18:44.955 [stream] stderr update: UpdateT = await self._iterator.anext()
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework/_types.py", line 3024, in anext
14:18:44.955 [stream] stderr update: UpdateT = await self._iterator.anext()
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework/_types.py", line 3024, in anext
14:18:44.955 [stream] stderr update: UpdateT = await self._iterator.anext()
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework/_tools.py", line 2559, in _stream
14:18:44.955 [stream] stderr async for update in inner_stream:
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework/_types.py", line 3024, in anext
14:18:44.955 [stream] stderr update: UpdateT = await self._iterator.anext()
14:18:44.955 [stream] stderr ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
14:18:44.955 [stream] stderr File "/usr/local/lib/python3.12/site-packages/agent_framework_openai/_chat_completion_client.py", line 540, in _stream
14:18:44.955 [stream] stderr raise ChatClientException(
14:18:44.955 [stream] stderr agent_framework.exceptions.ChatClientException: ("<class 'agent_framework_openai._chat_completion_client.OpenAIChatCompletionClient'> service failed to complete the prompt: 'NoneType' object has no attribute 'content'", AttributeError("'NoneType' object has no attribute 'content'"))

Code Sample

    """
    client = FoundryChatClient(
        project_endpoint=os.environ["FOUNDRY_PROJECT_ENDPOINT"],
        model=os.environ["AZURE_AI_MODEL_DEPLOYMENT_NAME"],
        credential=DefaultAzureCredential(),
    )
    """

    project_endpoint=os.environ["FOUNDRY_PROJECT_ENDPOINT"]
    openai_url = project_endpoint.rstrip("/") + "/openai/v1"

    chat_client = OpenAIChatCompletionClient(
        base_url=openai_url,
        model=os.environ["AZURE_AI_MODEL_DEPLOYMENT_NAME"],
        api_key=_token_provider,
    )

    agent = Agent(
        client=chat_client,
        instructions="You are a friendly assistant. Keep your answers brief.",
        # History will be managed by the hosting infrastructure, thus there
        # is no need to store history by the service. Learn more at:
        # https://developers.openai.com/api/reference/resources/responses/methods/create
        default_options={"store": False},
    )

Error Messages / Stack Traces

Package Versions

agent-framework-1.3.0

Python Version

No response

Additional Context

No response

[github-actions]

🤖 Automated triage reproduction notes (agent-authored — trust but verify)

Agent analysis

Repro: OpenAIChatCompletionClient._parse_text_from_openai() in python/packages/openai/agent_framework_openai/_chat_completion_client.py:776 crashes with AttributeError when choice.delta is None during streaming. The method assigns message = choice.delta (line 775) then accesses message.content (line 776) without a None guard. Minimal repro: construct a ChunkChoice via model_construct with delta=None and call client._parse_text_from_openai(choice) — also line 737 has the same issue with getattr(choice.delta, "reasoning_details", None).

• Failing test: python/packages/openai/tests/openai/test_issue_5732_none_delta.py
• Files examined: python/packages/openai/agent_framework_openai/_chat_completion_client.py, python/packages/openai/tests/openai/test_openai_chat_completion_client.py, python/packages/openai/tests/openai/conftest.py, python/packages/openai/pyproject.toml
• Tests run: python/packages/openai/tests/openai/test_issue_5732_none_delta.py::test_parse_response_update_with_none_delta, python/packages/openai/tests/openai/test_issue_5732_none_delta.py::test_parse_text_from_openai_with_none_delta_directly
• Reported version: 1.3.0
• Current version: 1.3.0