port(omniroute): carry upstream status and retry hint in post-keepalive error frames

[bloodf]

Scope

Ports OmniRoute #14632, the keepalive-frame part of #14572, and the finish-reason part of #14247.

• Late failures keep their status. Once earlyStreamKeepalive has committed a 200, a later failure used to go out as a generic event: error with the raw body, and the HTTP status and Retry-After were lost. The final frame now matches the client's wire format:

  • Responses: a flat error event with sequence_number. It has no top-level error key, because openai-node would throw on one.
  • Chat Completions: a data: {"error":…} line.
  • Claude Messages: an Anthropic event: error.

  Each carries status_code and retry_after_seconds (seconds or an HTTP date, capped at 0..3600). /v1/responses passes errorFormat: "responses" and /v1/messages passes errorFormat: "claude".

• Finish reasons on OpenAI passthrough. Streaming and non-streaming OpenAI passthrough now maps Claude stop_reason literals in finish_reason (end_turn, tool_use, …) to OpenAI values through the existing toOpenAIFinish(…, "claude"). Claude clients are unaffected.

• Not ported:

  • DurinDoor has no synthesized Responses keepalive frames and no Codex WebSocket failure frames. formatTranslatedStreamError already sends sequence_number: 0.
  • The threshold re-tuning and the combo 403 message from #14247.

Review notes:

• pause_turn maps to tool_calls, following the fork's existing Claude translator. OmniRoute maps it to stop.
• The Responses error keeps its event: error line, as OpenAI's stream and our formatTranslatedStreamError do.

Tests

• keepalive-error-frame-status.test.js (8 tests): each wire format, the HTTP-date cap, a missing header, a thrown handler, the fast path, and each route.
• openai-finish-reason-claude-literals.test.js (16 tests).
• Local test:ci: 0 assertion failures out of 12,131. The run was made on a heavily loaded machine, where one suite (db-concurrent) timed out in beforeAll. That suite passes with a longer hook timeout and is unrelated to this change. GitHub CI is the authoritative run.

Docs

docs/troubleshooting.mdx: new section "Streaming request fails after keepalive frames".

Baseline impact

None.

Wire format and migration

The frame fields are additive. The fast path (the handler answers inside the threshold) is unchanged.

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Project	Deployment	Actions	Updated
durindoor	Ready	Preview	Sep 25, 2026 7:35pm UTC