fix(responses): backfill missing id on output items for strict decoders

[bet4it]

Summary

Follow-up to #1941. That PR switched Grok to the Responses passthrough path and backfilled the required annotations field on output_text content parts. After it merged, Grok CLI still failed with serialization error: missing field `id` — the same class of strict-decoder failure, but for a different required field.

Root cause. Some upstream relays (observed with an openai-responses adapter provider) omit the id field entirely on output items in response.completed — message, reasoning, and function_call items all arrive with no id. In the async-openai fork that grok-build uses, OutputMessage.id and ReasoningItem.id are required (String, not Option), so deserializing response.completed fails hard.

This was confirmed by capturing the raw upstream SSE payloads: response.completed arrives with output items like {"type":"reasoning","summary":[...]} (no id), {"type":"message","role":"assistant","content":[...]} (no id), and {"type":"function_call","call_id":"call_...",...} (only call_id, no id).

What changed.

1. Backfill missing id on output items (src/server/responses/responses-field-backfill.ts). The existing backfillOutputItem now also synthesizes an id when one is absent, using a deterministic scheme per (item type, output index) with canonical OpenAI prefixes: msg_ocx_N, rs_ocx_N, fc_ocx_N, etc. Existing ids are never overwritten. The same index is used across streaming events (output_item.added/done uses event.output_index) so an item's generated id stays stable throughout the stream. Both the SSE block rewrite path and the bounded-JSON passthrough path are covered, mirroring how annotations is already handled.

2. Update the Grok Build guide (all locales). The docs still described the Chat Completions transport and its inbound translator, but Grok is now on api_backend = "responses". Updated the endpoint description to POST /v1/responses, fixed the managed-block example api_backend to "responses", and rewrote the reasoning section to describe Responses passthrough of reasoning.summary instead of Chat Completions reasoning_content translation.

Verification

• tsc --noEmit passes (strict).
• bun test tests/responses-field-backfill.test.ts — 10 pass, 0 fail (7 existing + 3 new: backfill missing ids on response.completed, preserve existing ids, use output_index on output_item.done).
• Rebased onto the latest origin/dev (ceac592d7).
• Captured raw upstream payloads confirmed the missing id field; after the fix, generated ids are deterministic and do not collide with real upstream ids.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

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Summary by CodeRabbit

• Documentation

  • Updated Grok Build integration guides to reference the Responses API endpoint exclusively.
  • Clarified reasoning-summary configuration, including route defaults and hiding reasoning traces with "none".
  • Updated guidance across supported translations.

• Bug Fixes

  • Responses output items without IDs now receive stable, type-specific identifiers.
  • Existing IDs and annotations remain unchanged across streaming and standard responses.

• Tests

  • Added coverage for generated IDs, preserved IDs, output indexes, inherited item types, and JSON responses.

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Maintainers: @lidge-jun @Ingwannu @Wibias

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• src/server/responses/responses-field-backfill.ts
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📝 Walkthrough

Walkthrough

The PR updates Grok Build documentation to use the Responses API and adds deterministic fallback IDs for Responses output items. The backfill applies to completed responses and streaming events while preserving existing IDs and annotations.

Changes

Grok Build documentation

Layer / File(s)	Summary
Update Grok Build Responses guidance docs-site/src/content/docs/guides/grok-build.md, docs-site/src/content/docs/*/guides/grok-build.md	The guides now document POST /v1/responses. The English guide selects the responses backend and documents reasoning.summary, including explicit overrides and "none" suppression. The localized guides remove Chat Completions endpoint references.

Responses output ID backfill

Layer / File(s)	Summary
Backfill output item IDs and validate traversal src/server/responses/responses-field-backfill.ts, tests/responses-field-backfill.test.ts	The backfill creates type-specific deterministic IDs from output indexes when IDs are missing, preserves existing IDs, and passes indexes through completed-response and streaming-event traversal. Tests cover reasoning, message, function-call, inherited item types, invalid indexes, and JSON responses.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🟡 Moderate · up to a8b47

The change backfills missing response item IDs, but malformed or missing streaming indexes could still produce duplicate or unstable IDs, while unknown item types may receive an unintended prefix. The PR is not fully merge-ready until these bounded correctness risks are addressed or explicitly accepted.

Suggested reviewers: ingwannu

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Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.
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Title check	✅ Passed	The title clearly describes the primary change: backfilling missing Responses API output-item IDs for strict decoders.

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Inline comments:
In `@src/server/responses/responses-field-backfill.ts`:
- Around line 33-55: Update backfillItemId to resolve ITEM_ID_PREFIXES only for
own properties, ensuring inherited types such as "toString" and "__proto__" use
the "item_" fallback; add a regression test covering an inherited key.
- Around line 131-132: Update the output_index handling before calling
backfillOutputItem so only non-negative integers are accepted via
Number.isInteger and a >= 0 check; do not default missing, fractional, or
negative values to 0, and preserve consistent item IDs with response snapshots.

In `@tests/responses-field-backfill.test.ts`:
- Around line 199-203: Add a focused regression test near the existing response
backfill tests that invokes backfillResponsesFieldsJson directly with a
JSON-serialized response, then parses its result and verifies missing response
item IDs are generated while existing IDs remain unchanged.

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• docs-site/src/content/docs/fr/guides/grok-build.md
• docs-site/src/content/docs/guides/grok-build.md
• docs-site/src/content/docs/ja/guides/grok-build.md
• docs-site/src/content/docs/ko/guides/grok-build.md
• docs-site/src/content/docs/ru/guides/grok-build.md
• docs-site/src/content/docs/tr/guides/grok-build.md
• docs-site/src/content/docs/zh-cn/guides/grok-build.md
• docs-site/src/content/docs/zh-tw/guides/grok-build.md
• src/server/responses/responses-field-backfill.ts
• tests/responses-field-backfill.test.ts

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[lidge-jun]

리뷰 · 우선순위 56 / 80

#1941 후속임. 그때는 output_text.annotations를 빈 배열로 채웠음. 이번엔 업스트림 릴레이가 response.completed / output_item.added|done에서 id 자체를 빼먹어서 grok-build serde가 missing field id로 죽음. message/reasoning은 id가 required String임. function_call은 call_id만 있고 id가 없음. 캡처한 raw SSE가 그 모양임.

고친 곳은 src/server/responses/responses-field-backfill.ts 한 파일임. backfillItemId가 빈 문자열/없음일 때만 msg_ocx_N rs_ocx_N fc_ocx_N 식으로 만듦. 있는 id는 안 덮음. 스트림은 event.output_index를 써서 같은 아이템이 added/done에서 같은 id를 유지함. JSON 패스스루(backfillResponsesFieldJson)도 같은 워크. types.ts/config.ts 안 건드림. dev 직접 MERGEABLE. 분할에 깔리는 쪽 아님.

합성 id의 경계는 이럼. prefix는 OpenAI 모양이고 가운데 ocx_가 진짜 업스트림 id랑 안 겹치게 함. output_index가 없거나 숫자가 아니면 0으로 떨어짐. 인덱스 없는 이벤트가 두 개면 msg_ocx_0이 중복될 수 있음. function_call은 call_id를 그대로 두고 id만 채움. 클라이언트가 id를 콜 식별자로 쓰면 fc_ocx_N이랑 call_...가 갈라짐. 테스트가 completed 백필 / 기존 id 보존 / output_index 안정 세 칸을 새로 넣음. 인덱스 누락 충돌은 안 봄.

점수는 56임. grok CLI 스트릭트 디코더 불이라 실사용은 있음. 지금 dev 불은 native-main 503(#2130)임. 드래프트 + 체크리스트 0/4. 2.27 막판에 안 넣음. #2129가 이미 이 모듈의 무조건 rewrite 때문에 윈도우 eager 마커가 상수 true인 걸 테스트로 고정했음. 여기 필드 하나 더 넣어도 그 결합은 그대로임.

해결방안: 박스 채우고 드래프트 풀면 됨. output_index 없는 이벤트는 id를 안 만들거나 이벤트 타입+순번 해시를 쓰는 쪽이 중복이 없음. grok CLI로 response.completed 한 번 보면 Closes 달 수 있음. 지금은 Refs가 맞음.

이 댓글은 grok-bot이 작성했습니다

[bet4it]

Thanks for the review. The output_index fallback-to-0 collision can't happen in practice, for two reasons:

1. The fallback only applies to streaming output_item.added / output_item.done, where output_index is a required field per the Responses API spec. A spec-compliant upstream always sends it as a non-negative integer. The Number.isInteger && >= 0 guard (added in the latest push) is purely defensive — it only fires on a spec-violating payload, and even then the worst case is a duplicate synthetic id, which is still strictly better than the current missing field id crash.

2. The response.completed path — where the missing field id error actually occurs — doesn't use the fallback at all. It goes through backfillResponseOutput, which uses output.map((item, idx) => backfillOutputItem(item, idx)). The array index is always unique and sequential, derived from the item's position in response.output[]. There is no fallback to 0; every item gets a distinct index by construction.

So the collision scenario requires a non-compliant upstream that simultaneously (a) omits id on output items AND (b) omits output_index on streaming events for two different items — while still being functional enough to produce a response.completed with a well-formed output[] array. In that case the streaming events might share msg_ocx_0, but the terminal response.completed (which is what the strict decoder actually deserializes into the final object) would still have unique ids from the array index.

A hash-based approach would be non-deterministic across streaming and completed events for the same item, making client-side correlation harder. The current prefix + ocx_ + index scheme stays stable across output_item.added → output_item.done → response.completed as long as the upstream sends output_index (which it must).

[lidge-jun]

Thanks for this, @bet4it — closing as superseded by #2142, which carries your implementation and your tests.

One correction was added on top: an absent or malformed output_index collapsed to 0, so two such items both synthesized msg_ocx_0. Duplicate ids are the defect the backfill exists to prevent, so an unusable index now falls back to a monotonic ordinal based far above any plausible real index. Your well-formed path is untouched — the stable index-derived id is what makes streaming events agree on the same item, and that behavior is now pinned by its own test.

That meant replacing your expect(parsed.item.id).toBe("msg_ocx_0") assertion rather than deleting it quietly: it now asserts the id is well-formed, and a new test asserts two such items do not collide. I verified that new test fails against your branch's source and passes with the fallback, so it is a real guard.

Your locale doc changes were left out of this PR only because they were uneven across languages; that is worth a separate parity pass, not a reason to hold the fix. Your work is credited in the PR description.