azure-ai-agentserver-core: OpenTelemetry context detach failure during streaming responses

[eamonoreilly]

• Package Name: azure-ai-agentserver-core
• Package Version: 1.0.0b1 (or check your installed version with pip show azure-ai-agentserver-core)
• Operating System: macOS (also reproducible on other platforms)
• Python Version: 3.13

Describe the bug

When using streaming responses with azure-ai-agentserver-core, OpenTelemetry raises ValueError: <Token...> was created in a different Context errors during context detach. This is a known issue with OpenTelemetry when async generators aren't properly closed using contextlib.aclosing().

The error occurs in azure/ai/agentserver/core/server/base.py in the gen_async() function where the streaming response iterates over an async generator without wrapping it with aclosing().

To Reproduce

1. Create an agent using agent_framework with streaming enabled

import asyncio
from dotenv import load_dotenv

load_dotenv(override=True)

from agent_framework.azure import AzureAIAgentClient
from azure.ai.agentserver.agentframework import from_agent_framework
from azure.identity.aio import DefaultAzureCredential


async def main():
    async with (
        DefaultAzureCredential() as credential,
        AzureAIAgentClient(credential=credential) as client,
    ):
        agent = client.create_agent(
            name="SimpleAgent",
            instructions="You are a helpful assistant. Just respond briefly to any message.",
        )

        print("Server running on http://localhost:8088")
        server = from_agent_framework(agent, credential)
        await server.run_async()


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

2. Host it using azure.ai.agentserver.agentframework.from_agent_framework()
3. Send requests that trigger streaming responses. curl -X POST http://localhost:8088/responses -H "Content-Type: application/json" -d '{"stream": true, "input": "Hello"}'
4. Observe the error in logs:```
   ValueError: <Token var=<ContextVar name='current_context' default={} at 0x...> at 0x...> was created in a different Context
   Failed to detach context

**Expected behavior**

No OpenTelemetry context detach errors during streaming responses.

**Screenshots**

N/A

**Additional context**

This is a known issue with OpenTelemetry and async generators, fixed in other projects:
- **Root cause**: https://github.com/open-telemetry/opentelemetry-python/issues/2606
- **Fix pattern**: https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3938
- **Documentation**: https://logfire.pydantic.dev/docs/reference/advanced/generators/

**Suggested fix** in `azure/ai/agentserver/core/server/base.py`:

The async generator `resp` should be wrapped with `contextlib.aclosing()`:

```python
from contextlib import aclosing

async def gen_async():
    ctx = TraceContextTextMapPropagator().extract(carrier=context_carrier)
    token = otel_context.attach(ctx)
    error_sent = False
    try:
        yield _event_to_sse_chunk(first_event)
        async with aclosing(resp) as stream:  # <-- ADD THIS
            async for event in stream:
                yield _event_to_sse_chunk(event)
    except Exception as e:
        # ... error handling
    finally:
        otel_context.detach(token)
        # ...

Similarly for the sync generator case using contextlib.closing().

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @dargilco @glharper @howieleung @nick863 @trangevi @trrwilson.

[howieleung]

@xiangyan99 This is agent framework question. Could you triage?