fix: prevent ContextVar reset error in async streaming context.

[JilinJL]

Summary

This PR fixes a runtime error caused by an unexpected reset_current keyword argument passed to Trace.finish() within the RunResultStreaming.stream_events() method.

What was the issue?

Currently, stream_events() calls:
refer #515

Solution

Wrap the .finish(reset_current=True) call in a try/except block to fallback to a safe reset mode:

if self._trace:
    try:
        self._trace.finish(reset_current=True)
    except ValueError:
        logger.warning("ContextVar reset failed — switching to reset_current=False")
        self._trace.finish(reset_current=False)

🧪 Testing

Tested with a minimal FastAPI + StreamingResponse setup. After this patch:

• The stream completes successfully.
• No ValueError is raised.
• Trace finalization still works.

📦 Affected file

openai-agents-python\src\agents\result.py

💬 Related Issue
This PR resolves the bug described in the issue: #515

[rm-openai]

IMO the loud exception is probably a good thing? Catches obvious errors. WDYT?

[JilinJL]

IMO the loud exception is probably a good thing? Catches obvious errors. WDYT?

I realize now that I don’t understand this area as well as I thought — my knowledge is still quite shallow.

I tried to be clever and submitted a PR, thinking I could grab a quick contribution, but clearly I misunderstood how it actually works.

Thanks a lot for the correction and your patience — I’ve learned from this.