feat(retry): refetch once on zero-output mid-stream socket reset - #3389
feat(retry): refetch once on zero-output mid-stream socket reset#3389Yum-wu wants to merge 2 commits into
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Pre-stream retry wrappers (fetchWithResetRetry / fetchWithTransientRetry) only cover fetch() rejecting before response headers. A mid-stream socket reset (Cloudflare closing idle keep-alive connections while Bun's pool reuses the half-closed socket) surfaces as a ReadableStream read() rejection and kills the turn with response.failed/upstream_reset even when zero bytes were relayed to the client. Add wrapWithZeroOutputRefetch + refetchOnZeroOutputReset to src/lib/upstream-retry.ts: a body wrapper that, on a reset-shaped read() error before the first byte is consumed, transparently refetches ONCE on a fresh connection (connection-reset recovery init: Connection: close + keepalive: false). Partial-output failures, clean EOF, non-reset errors, and failed/empty refetches keep the existing fail-closed tail. Wire the wrapper into both streaming lanes before any tee/eager/parser branch, so inspection and client relays need no changes: - src/server/responses/core.ts: wrap the raw passthrough body before the terminal-repair layer (the refetched body then runs through the same repair pipeline). - src/server/chat-native.ts: wrap the native chat SSE body with an inline refetch thunk that uses the finalized active request/provider. Add focused regression tests (12 cases) covering the refetch gate, zero-output swap, partial-output fail-closed, single-retry ceiling, and cancel forwarding.
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drafts: true📝 WalkthroughWalkthroughThe change adds one-time recovery for zero-output upstream SSE connection resets. It wraps native chat and responses streams, refetches with connection-reset settings, preserves original failures, and tests replacement, cancellation, and retry-limit behavior. ChangesZero-output reset recovery
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to Zero-output reset recovery can currently turn an unsuccessful retry into a misleading successful stream and may expose sensitive provider error details in logs. These cases should be fixed before enabling the new retry behavior. Suggested reviewers: Sequence Diagram(s)sequenceDiagram
participant UpstreamSSE
participant wrapWithZeroOutputRefetch
participant fetchWithHeaderTimeout
participant nativeChatSse
UpstreamSSE->>wrapWithZeroOutputRefetch: provide response body
wrapWithZeroOutputRefetch->>fetchWithHeaderTimeout: refetch after zero-output reset
fetchWithHeaderTimeout-->>wrapWithZeroOutputRefetch: return replacement response
wrapWithZeroOutputRefetch->>nativeChatSse: continue recovered stream
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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In `@src/lib/upstream-retry.ts`:
- Line 476: Update the replacement-response handling around the
!replacement.body check to also reject responses where replacement.ok is false;
cancel the failed replacement body, return null, and preserve the wrapper’s
original reset failure. Add a regression test covering a body-bearing 503
replacement response.
- Line 471: Update the error logging in doFetch’s retry path so the refetch
failure never emits the raw retryErr message; instead log a fixed failure
category or sanitize the message with redactSecretString before interpolation,
while preserving the existing warning behavior.
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📒 Files selected for processing (4)
src/lib/upstream-retry.tssrc/server/chat-native.tssrc/server/responses/core.tstests/upstream-retry-zero-output.test.ts
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리뷰 · 우선순위 68 / 80이 PR은 Responses 네이티브 패스스루와 네이티브 Chat SSE에서, 헤더는 왔는데 본문 첫 바이트가 오기 전에 소켓이 끊기면 턴이 바로 죽는 문제를 고칩니다. 지금 같은 종류의 구멍은 다른 길에서는 이미 막혀 있습니다. 콤보 페일오버는 #3236이 출력 0인 불완전 스트림을 다음 타깃으로 넘깁니다. Kiro 어댑터는 #519 쪽에서 출력 0이거나 하트비트만 있는 중단을 클라이언트가 다시 시도할 수 있게 표시합니다. 그런데 단일 제공자 패스스루와 네이티브 Chat SSE에는 그 게이트가 없습니다. 이 PR은 그 두 길에만, 그리고 아직 한 바이트도 안 읽었고 에러가 고치는 방법은 본문 스트림을 한 겹 감싸는 것입니다. types.ts / config.ts 분할과는 무관합니다. 설정 스키마를 안 건드리므로 close-don't-rebase 대상이 아닙니다. 이슈 #3384를 고친다고 적혀 있지만, 그 이슈는 템플릿이 없어서 봇이 not_planned로 닫았습니다. PR은 아직 초안이고 본문 체크리스트 네 칸이 비어 있습니다. 방금 확인한 게이트는 hygiene, enforce-target, label, resolve-pr가 초록이고 CodeRabbit만 진행 중입니다. 이 댓글에서 라벨은 바꾸지 않습니다. 최신 알아 둘 점은 재요청이 업스트림 비용과 할당량을 한 번 더 쓴다는 것입니다. 클라이언트에는 아직 아무것도 안 줬으니 턴을 살리는 쪽을 고른 것이고,
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Address CodeRabbit review on lidge-jun#3389 (2 Major / quick-win findings): 1. Sensitive-data exposure (CWE-532): the refetch-failure warn logged the raw error message, which can carry provider-returned URLs/headers/tokens. Redact via redactSecretString (leaf module, no new dependency) before it reaches the log. 2. Missing replacement.ok gate: a body-bearing 401/429/5xx/redirect replacement was accepted and its body relayed as SSE stream data under the original 200 response status — a malformed 'successful' stream. Treat any non-ok replacement as a failed refetch (cancel body, return null) so the wrapper propagates the original reset failure. Regression tests added: refetchOnZeroOutputReset rejects a body-bearing 503; wrapWithZeroOutputRefetch propagates the original error for body-bearing 503 and 401 replacements; refetch error messages are redacted before logging. Verified: tests/upstream-retry-zero-output.test.ts 16 pass, adjacent upstream-retry (23) and upstream-transient-retry (15) suites green, tsc --noEmit clean.
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Held, and the reason is a measurement rather than a preference. The safety argument rests on Four out of four. The control — same server, clean close — delivers The consequence: an upstream that already committed a turn and emitted tool calls, then reset, gets read as zero-output and the identical request is sent again. Responses requests are not necessarily idempotent — This repository also decided against exactly this once already. What would make this landable: gate on protocol-level evidence of no output rather than on bytes consumed — the SSE inspector already in the pipeline can say whether any The rest of the implementation is sound and worth keeping: rejecting a non-2xx replacement, propagating the original error on partial output, the single-attempt cap, and the redaction are all correct. The problem is the discriminating power of the gate, not its construction. |
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Summary
Fixes the generic "Upstream stream terminated unexpectedly: The socket connection was closed unexpectedly" turn-kill on the Responses native passthrough and native chat SSE lanes (issue #3384).
Root cause: pre-stream retry wrappers (
fetchWithResetRetry/fetchWithTransientRetry) only coverfetch()rejecting before response headers. Once headers arrive and the relay starts reading the SSE body, a mid-stream socket reset (Cloudflare closing idle keep-alive connections while Bun's pool reuses the half-closed socket) surfaces as aReadableStream.read()rejection — outside every pre-stream retry wrapper — and the turn dies withresponse.failed / upstream_reseteven when zero bytes were relayed to the client.Fix (mirrors the existing Kiro adapter's zero-output retryable semantics, generalized):
src/lib/upstream-retry.ts: addwrapWithZeroOutputRefetch+refetchOnZeroOutputReset. A body wrapper that, on a reset-shaped read() error (socket connection was closed unexpectedly/ECONNRESET/EPIPE) before the first byte is consumed, transparently refetches once on a fresh connection (connection-resetrecovery init:Connection: close+keepalive: false, so Bun never reuses the pooled half-closed socket).src/server/responses/core.ts: wrap the raw passthrough body before the terminal-repair layer, so the refetched body runs through the same repair pipeline; both the eager relay and the tee inspection branches read through the wrapper unchanged.src/server/chat-native.ts: wrap the native chat SSE body with an inline refetch thunk using the finalized active request/provider.Fail-closed is preserved deliberately: partial-output failures, clean EOF, non-reset errors, aborts, and failed/empty refetches all propagate the ORIGINAL error — replaying after emitted tool calls would duplicate side effects (same policy as
relay.ts's "deliberately NOT a resend").Verification
node node_modules/typescript/bin/tsc --noEmit— clean (repo'sbun x tscbin remap fails on this Windows setup; direct tsc used)bun test tests/upstream-retry-zero-output.test.ts— 12 pass / 0 fail (new regression tests: refetch gate, zero-output swap, partial-output fail-closed, single-retry ceiling, cancel forwarding)bun test tests/upstream-retry.test.ts— 23 pass / 0 failbun test tests/upstream-transient-retry.test.ts— 15 pass / 0 failbun test tests/upstream-reachability.test.ts— 27 pass / 0 failbun test tests/transient-budget-scope-source.test.ts— 2 pass / 0 failChecklist
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Reliability
Bug Fixes