fix(responses): preserve streamed response IDs for conversation continuation

[grahamking]

Chat-backed Responses streams added a resp_ prefix to response IDs, but stored history remained keyed by the upstream ID. Follow-up requests using the returned ID silently lost prior turns.

Now we preserve the upstream ID during streaming, matching buffered responses and history storage.

Fixes: https://linear.app/nvidia/issue/SWITCH-1564

Assisted-by: Pi:GPT 6 Astra medium
Reviewed-by: Claude:Opus 5.5 medium
Signed-off-by: Graham King grahamk@nvidia.com

Summary by CodeRabbit

• Bug Fixes
  • OpenAI Responses now retains the original source or target message ID as the response ID, instead of modifying IDs with a prefix. When neither message ID is available, the response uses resp_switchyard as a fallback. This keeps response identifiers consistent with the upstream message when translating streaming events.

[coderabbitai]

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: NVIDIA-NeMo/Switchyard/.coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 600aa3c9-7eb5-438d-971c-4ff0ead0b71f

📥 Commits

Reviewing files that changed from the base of the PR and between a601a9a and 00b67e3.

📒 Files selected for processing (2)

• crates/switchyard-translation/src/codecs/responses/stream.rs
• crates/switchyard-translation/tests/stream_translation.rs

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Walkthrough

The Responses stream translator now uses the target or source message ID unchanged. If neither ID exists, it uses resp_switchyard. A streaming test checks that an OpenAI Chat event ID is preserved in the emitted response.id.

Changes

Response ID preservation

Layer / File(s)	Summary
Message ID mapping and stream test crates/switchyard-translation/src/codecs/responses/stream.rs, crates/switchyard-translation/tests/stream_translation.rs	The translator uses the target or source message ID unchanged, with resp_switchyard as the fallback. A streaming test checks that chatcmpl-test remains unchanged in response.id.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~8 minutes

Merge Risk: ⚪ Minimal · up to 00b67

Streamed chat-backed responses retain the upstream ID used to restore continuation history. No actionable merge blocker is evident.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preserving streamed response IDs for conversation continuation.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

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_{A rabbit checks the stream at dawn
The message ID hops through unchanged
No extra prefix trails behind
A fallback waits when IDs hide
The test confirms the path is sound}

_{Comment @coderabbitai help to get the list of available commands.}