Python: fix (openai): only propagate usage metadata for final streaming chunk without choices

[daydaychen]

Motivation and Context

1. Why is this change required?

   • The previous condition copied usage metadata whenever chunk.usage existed, which could incorrectly propagate usage into chunks that already contained choices.

2. What problem does it solve?

   • Prevents incorrect propagation of usage metadata that can cause empty messages or duplicated metadata when a streaming chunk contains choices plus usage.

3. What scenario does it contribute to?

   • Streaming OpenAI chat responses where the API may send a final usage-only chunk (no choices) to report usage stats.

4. If it fixes an open issue, please link to the issue here.

   • No linked issue.

Description

• File modified:

  • python/semantic_kernel/connectors/ai/open_ai/services/open_ai_chat_completion_base.py

• Change summary:

  • In OpenAIChatCompletionBase._inner_get_streaming_chat_message_contents,
    replace:
    if chunk.usage is not None
    with:
    if len(chunk.choices) == 0 and chunk.usage is not None

• Design notes:

  • This is a minimal, targeted fix to ensure usage metadata is only copied when the streaming chunk contains no choices (typical for the final usage-only chunk).
  • Behavior of other streaming logic is unchanged.
  • Recommend adding unit tests covering:
    • A chunk that contains choices and usage (should not propagate usage).
    • A usage-only final chunk (should propagate usage to the synthesized choice).

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

Files changed:

• python/semantic_kernel/connectors/ai/open_ai/services/open_ai_chat_completion_base.py

[Copilot]

Pull Request Overview

This PR fixes a bug in the OpenAI chat completion streaming logic to prevent incorrect propagation of usage metadata when it appears alongside actual content choices. The change ensures usage metadata is only copied to synthesized choices when the streaming chunk contains no choices, which is the expected pattern for final usage-only chunks from the OpenAI API.

Key Changes

• Modified the condition in _inner_get_streaming_chat_message_contents to check for empty choices before propagating usage metadata
• Prevents incorrect behavior when streaming chunks contain both choices and usage metadata

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[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
connectors/ai/open_ai/services
open_ai_chat_completion_base.py	128	7	94%	71, 81, 102, 122, 143, 179, 320
TOTAL	27111	4727	82%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3715	22 💤	0 ❌	0 🔥	1m 36s ⏱️