fix(responses): answer a wrapped WebSocket rejection with its HTTP status

[FredAmartey]

Delivered — superseded by merged work

Verified in dev at 5759d9ea2f1e7281cdc01eb9628f2e0a123fb59c: #3793 (110623ecfc).

Original contribution: fix(responses): answer a wrapped WebSocket rejection with its HTTP status, by @FredAmartey.

Precommit wrapped WebSocket rejection status; mid-turn failures retain their separate boundary.

The original PR is closed as superseded; its contribution remains credited in the landed history.

Attribution strengthened by #3811, merged as cf9f662190c4c6770697c45c870941509cc98f9c. See CREDITS.md for the source-to-landing attribution record.

Summary

• When the ChatGPT backend refuses a turn over the upstream WebSocket before it starts (usage limit, expired token, any other 4xx), the proxy now answers with that HTTP status, the frame's headers and the error body, the same as the HTTP lane does.
• Before, the refusal was relayed as an SSE error event inside a 200 stream, and Codex reported it as stream disconnected before completion: Incomplete response returned, reason: adapter_eof.
• 5xx frames, errors after response.created, and error frames without a status keep the stream path.
• Four regression tests next to the existing WS relay tests, plus one sentence in the architecture reference where the canonical upstream WebSocket lane is described.

Problem

I ran into this on a Codex Desktop thread that had just used up its 5-hour window. Every turn failed with the adapter_eof message above, the app never said "usage limit", and the proxy's request log filed it as a 502 even though it had the real reason (The usage limit has been reached).

Over the WebSocket, a refused turn looks like this. The backend does not open a response; it sends one frame and closes:

{"type":"error","status_code":429,"error":{"type":"usage_limit_reached","message":"The usage limit has been reached","plan_type":"plus","resets_at":1788667850},"headers":{"X-Codex-Primary-Used-Percent":"100","X-Codex-Primary-Reset-At":"1788667851"}}

codexWsExchange relays that frame as-is, so the client gets:

HTTP/1.1 200 OK
event: error
data: {"type":"error","error":{"type":"usage_limit_reached",...},"status_code":429,...}

event: response.incomplete
data: {"type":"response.incomplete","response":{"status":"incomplete","incomplete_details":{"reason":"adapter_eof"}}}

Two things go wrong from there. The relay does not treat error as a terminal event (terminalStatusFromParsed returns null for it), so it appends the synthesized adapter_eof. And Codex's SSE parser has no error arm at all (codex-rs/codex-api/src/sse/responses.rs), so it drops that event and only sees the incomplete that follows. Its retries get the same answer. Nothing in core.ts that handles a pre-stream 429 (quota cooldown, reset credits, alternate-account retry) runs, because all of that keys on an HTTP status.

Native Codex does not have this problem because its own WebSocket client maps the frame back to the HTTP error (codex-rs/codex-api/src/endpoint/responses_websocket.rs, map_wrapped_websocket_error_event). The proxy's HTTP fallback lane is fine too, since there the 429 arrives as a status. Only the WebSocket lane loses it.

It is not an edge case. The canonical ChatGPT backend has used this lane on every stable Bun 1.4.0 since 6f2be35 (2026-08-12), and the package bundles Bun 1.4.0. #3029 reported the same adapter_eof after a 5-hour window ran out in the account pool; #3110 fixed the proactive scoring, but #585's alternate-account retry on a pre-stream 429/402 still cannot fire here because the 429 never arrives as one.

Fix

In codexWsExchange, before the first relayed frame commits the 200 response: if that frame is type: "error" with an integer status_code (or status, the other spelling Codex accepts) in the 4xx range, resolve the exchange with new Response(JSON.stringify({ error }), { status, headers }). The headers are the frame's string headers minus the framing and encoding ones (content-encoding, content-length, content-type, transfer-encoding, connection, keep-alive), plus content-type: application/json and cache-control: no-store, since the body is account-specific and rebuilt here. The socket is disposed. That is the response the HTTP lane already produces for the same refusal, so everything downstream stays as it is.

I stopped at 4xx. This module is careful not to answer with a 5xx once a frame has been sent, so that nothing gets resent, and Codex already retries an adapter_eof on its own. Codex itself converts every non-2xx; extending this to 5xx would be a small follow-up if you want parity.

This reaches the canonical ChatGPT lane only. An opt-in upstreamWebsocket provider commits its 200 on send, before any frame can be inspected, so a wrapped rejection there still relays in-band as before; the comment and the docs say so. Deferring that commit would put those providers under the canonical prelude timeout, which is a separate decision.

One existing fixture changed: the multiline-error case in ws-upstream.test.ts carried status: 400, which is now answered as HTTP, so the fixture drops the status. What it checks, a pretty-printed in-band error staying one SSE data line, still holds for a mid-turn error frame. structure/04 and the translated docs are untouched.

Verification

• bun test tests/responses/ws-upstream.test.ts tests/responses/ws-upstream-reuse.test.ts: 99 passed, 1 skipped, 0 failed. New cases: the 429 frame becomes a 429 response with its headers and body; the status spelling; an error after response.created stays in-band; a 5xx stays in-band.
• bun run typecheck: passed.
• bun run test:changed: 3,909 passed, 1 skipped, 0 failed.
• bun run test -- --parallel=2 --timeout=60000: 20,129 passed, 15 skipped, 0 failed. At the default four workers on this laptop, runs kept dropping one or two unrelated tests to contention (server-management-auth, ocx-launcher-runtime, api-storage-policy-put-race, cli-export-command, cli-headless-parity); each passes alone on this branch and on clean dev. The 60 s timeout is the one CI uses.
• bun run privacy:scan: passed.
• cd docs-site && bun install --frozen-lockfile && bun run build: 425 pages built.
• Live, against the real backend, on a Plus account with its 5-hour window at 100%. Sent straight to chatgpt.com/backend-api/codex/responses, the request gets HTTP 429 with the usage_limit_reached body and the x-codex-* headers. Through the proxy before this change: HTTP 200, event: error, then event: response.incomplete with adapter_eof. After: HTTP 429, content-type: application/json, the same headers and body, and the request log shows 429 rate_limit_exceeded instead of 502 upstream_server_error.
• Review round: the header deny-list, cache-control: no-store and the docs relocation landed as a second commit. On that head: bun test tests/responses/ws-upstream.test.ts 63 passed, 0 failed; bun run typecheck passed; bun run test:changed 3,909 passed, 1 skipped, 0 failed; bun run test -- --parallel=2 --timeout=60000 20,129 passed, 15 skipped, 0 failed; docs build 425 pages. A third, docs-only commit corrects the architecture sentence about the rebuilt headers; docs build rerun, 425 pages.

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. No auth or credential handling changes; the frame's headers are forwarded the way the HTTP lane already forwards upstream response headers; the fixtures carry no real account data.

Review readiness checklist

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Summary by CodeRabbit

• Bug Fixes

  • WebSocket requests rejected before any output now return the correct HTTP 4xx status, response headers, and JSON error details instead of an incorrect successful stream.
  • These errors now receive the same handling as equivalent HTTP errors, including refresh, quota, and account-rotation behavior.
  • Errors occurring after output begins, along with 5xx errors, continue through the existing streaming path.

• Documentation

  • Updated architecture documentation to describe WebSocket rejection handling.

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📝 Walkthrough

Walkthrough

The WebSocket exchange now converts eligible pre-output upstream 4xx error frames into HTTP error responses. Committed responses, 5xx errors, and invalid statuses continue through the SSE stream path. Tests and architecture documentation cover the behavior.

Changes

WebSocket rejection handling

Layer / File(s)	Summary
Build HTTP rejection responses src/server/responses/codex-ws-exchange.ts	The new helper accepts integer 4xx status_code or status values, filters framing headers, preserves valid response headers, and returns a JSON error body with cache-control: no-store.
Route and validate pre-output rejections src/server/responses/codex-ws-exchange.ts, tests/responses/ws-upstream.test.ts, docs-site/src/content/docs/reference/architecture.md	Before response commitment, eligible 4xx frames now resolve as HTTP responses. Tests cover header projection, both status field names, committed responses, and 5xx frames. The architecture documentation describes the resulting HTTP behavior.

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

Merge Risk: ⚪ Minimal · up to cb7f5

Pre-stream WebSocket 4xx rejections are returned as structured HTTP errors while committed streams and 5xx errors retain existing SSE behavior. The documented behavior matches the covered implementation, with no current merge-blocking risk identified.

Sequence Diagram(s)

sequenceDiagram
  participant UpstreamWebSocket
  participant codexWsUpstreamFetch
  participant HTTPErrorHandlers
  UpstreamWebSocket->>codexWsUpstreamFetch: Send pre-output error frame
  codexWsUpstreamFetch->>codexWsUpstreamFetch: Build HTTP response for eligible 4xx status
  codexWsUpstreamFetch->>HTTPErrorHandlers: Resolve status, headers, and JSON error body
  HTTPErrorHandlers->>codexWsUpstreamFetch: Apply refresh, quota, or account-rotation handling

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Title check	✅ Passed	The title clearly and concisely describes the main change: returning a wrapped pre-stream WebSocket rejection with its HTTP status. It matches the implementation, tests, and documented objective.

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Inline comments:
In `@src/server/responses/codex-ws-exchange.ts`:
- Line 44: Update the header filtering in the response-rebuilding flow around
wrappedRejectionResponse to exclude content-encoding and other
representation-specific headers, ensuring the uncompressed JSON body is not
interpreted as compressed. Add a regression case covering an upstream
content-encoding: gzip header.
- Line 212: Update src/server/responses/codex-ws-exchange.ts at line 212 so
noncanonical upstreamWebsocket responses remain uncommitted until initial
response activity or an eligible 4xx rejection, allowing the
responseCommitted/type error branch to return the documented HTTP rejection; add
a regression test for a noncanonical Responses URL with a 429 frame. Update
docs-site/src/content/docs/reference/configuration/providers.md at line 129 to
match the resulting scope, stating that only allowed headers are copied and the
rejection body is JSON shaped as { "error": ... }.
- Line 45: Update the header-copying logic in wrappedRejectionResponse to set
Cache-Control to no-store after forwarding upstream headers, ensuring
account-specific rejection responses cannot be cached or reused across proxy
identities.

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[lidge-jun]

리뷰 · 우선순위 68 / 80

이 PR은 Codex Responses 업스트림 WebSocket이, 턴을 시작하기 전에 보내는 “거절용 error 프레임”을 HTTP 상태처럼 다시 돌려주는 픽스입니다. 지금 dev(HEAD 25c8d2b4e)의 src/server/responses/codex-ws-exchange.ts는 소켓이 열린 뒤 오는 프레임을 대개 200 SSE 스트림으로 중계합니다. 백엔드가 만료 토큰·사용량 한도처럼 출력을 내기 전에 error + status_code(또는 status) 한 장만 보내고 닫으면, 클라이언트는 SSE error와 이어지는 adapter_eof만 보고, 예전의 HTTP 경로에 있던 토큰 갱신·쿼터·계정 회전 핸들러는 상태 코드를 못 봅니다. PR이 가리킨 #3029 계열 증상과 맞습니다.

고치는 위치는 한 파일에 가깝습니다. wrappedRejectionResponse가 payload에서 400–499 정수 상태만 고르고, 프레임 헤더 중 framing/encoding(content-encoding, content-length, content-type, transfer-encoding 등)은 버리고, 본문은 JSON {"error": ...}로 다시 만듭니다. cache-control: no-store를 붙입니다. 스트림에 아직 아무것도 안 보낸 상태(!responseCommitted)이고 타입이 error일 때만 이 HTTP 응답으로 resolve합니다. 이미 response.created 등으로 출력을 연 뒤의 error, 그리고 5xx는 예전처럼 스트림에 남깁니다. 문서 architecture.md에도 “4xx 사전 거절만 HTTP로”라고 적혀 있습니다.

테스트가 핵심 경계를 잘 잡습니다. 429 프레임 → HTTP 429 + x-codex-* 헤더 유지 + framing 헤더 제거, status 철자, mid-turn error는 200 스트림, 5xx는 스트림. 본문에 Plus 계정 live 재현(프록시 전: 200+adapter_eof / 후: 429+usage_limit_reached)까지 적혀 있어 현장 증거도 있습니다. types/config 대분할과 무관합니다.

우선순위 68인 이유다. 쿼터·회전이 실제로 동작하려면 상태 코드가 HTTP 레인과 같아야 하고, 변경이 작고 이중 생성을 막으려고 4xx·pre-commit만 허용한 설계가 분명합니다. 다만 아직 draft이고 checklist에 “ready for review”가 비어 있으며, enforce-target/label이 CANCELLED인 상태입니다. Ready로 올리고 CI를 다시 돌려야 합니다. release-244 열차(task-input 등)와 파일 충돌은 거의 없어 독립 버그픽스로 끼워 넣을 수 있습니다.

경로/심볼 - src/server/responses/codex-ws-exchange.ts wrappedRejectionResponse - 4xx만 HTTP로 재구성. framing 헤더 deny-list
라인 (error 프레임, !responseCommitted) - 거절이면 cleanup 후 resolve(rejection). 이미 commit된 스트림은 건드리지 않음
경로 - tests/responses/ws-upstream.test.ts - 429/401/mid-turn/5xx 네 경계
경로/심볼 - 옵트인 upstreamWebsocket 일반 프로바이더 - 주석대로 send 시점에 응답이 확정되면 이 경로와 다름. 범위는 캐논 ChatGPT WS 레인

메인테이너의 판단이 필요한 지점

• draft Ready 전환 시점을 지금으로 둘지, CodeRabbit/Codex 잔여 코멘트 정리 뒤로 둘지
• #3029 또는 관련 이슈를 이 PR로 닫을지, 문서·테스트만으로 충분한지
• 5xx를 일부 상태에서도 HTTP로 올릴지(지금 설계는 의도적으로 스트림 유지 — 권장은 유지)

너의 추천
Ready로 올린 뒤 독립 버그픽스로 dev에 머지하세요. 사전 4xx 거절을 HTTP로 되살리는 명확한 픽스이고, release-244 task-input 열차와 겹치지 않습니다. 5xx·mid-turn 동작은 지금처럼 스트림에 두는 편이 안전합니다. types/config close-don't-rebase 아님.

이 댓글은 grok-bot이 작성했습니다

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Inline comments:
In `@docs-site/src/content/docs/reference/architecture.md`:
- Around line 153-156: Update the architecture documentation describing the 4xx
error-frame HTTP response to state that it copies permitted upstream headers,
sets content-type to application/json, and forces cache-control to no-store,
rather than claiming all headers except framing and encoding headers are
preserved.

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