[pacocartones]

Summary

• When a Responses upstream served a Chat Completions client without streaming, finish_reason was only ever tool_calls or stop. A response that ended incomplete on max_output_tokens or content_filter reached the client as a clean stop.
• It now uses computeFinishReason, the rule the streaming path got in fix(sse): map Responses response.incomplete to length/content_filter finish reasons (#15489) #15867, so it gives length or content_filter.

Related Issues

• Related to fix(sse): map Responses response.incomplete to length/content_filter finish reasons (#15489) #15867, fix(providers): Codex streaming request returns 502 "Provider returned empty content" in a long OpenCode session #15489

Target Branch

• Base is the active release/v3.8.x branch (the highest open release/v*), not main
• New feature? From 3.8.55 on it is held with the v4-feature label for the v4 channel

Validation

• Change type: other (translator)
• Focused tests and category gates from the golden path
• npm run lint (eslint on the changed files: only the toNumber error already on the base, responseTranslator.ts:39)
• Reconciled with the current active release base; focused checks rerun afterward
• Production-code changes include a new or updated automated test in this PR

Tests Added Or Updated

• tests/unit/responses-incomplete-nonstreaming-chat.test.ts (new): 4 tests. 2 fail on the base and all 4 pass with the fix. The two that already pass check that a completed response still gives stop and a function call still gives tool_calls.

Coverage Notes

• responseTranslator.ts, OPENAI_RESPONSES → OPENAI branch, through translateNonStreamingResponse.

Reviewer Notes

• On the previous release head (7f3cbb0) the 28 test files that import these modules passed 337/337. On the current head (e23fb0f) the new test is 4/4 with the fix and 2/4 fail without it.
  ⚠️ base-red inherited: 🔴 Release branch not green: release/v3.8.52 #15306