fix(claude): surface a declared client refusal as its 4xx, not a retryable 502

[vadymhimself]

Summary

When an upstream answers a Claude Code /v1/messages turn with a 200 SSE that ends in a bare error frame declaring a client-class Anthropic error type (invalid_request_error, authentication_error, permission_error, not_found_error) and no refusal code, Claude Code gets a retryable failure instead of the refusal:

• Streaming: the synthesized relay tail (upstreamErrorTailFrame) stamps the frame upstream_error / upstream_server_error, because recognizedUpstreamError (fix(logs): keep recognized bare upstream error classes in synthesized terminals #6889) only knows the rate-limit and overload classes. The Claude translator maps that to a 502, and Claude Code receives overloaded_error.
• Non-streaming: the collected-error branch in src/server/claude-messages.ts maps only context_length_exceeded to 400. Every other translated error returns 502, including one already typed invalid_request_error.

In both cases Claude Code retries a request whose verdict cannot change. Each doomed retry spends rate limit and quota, a combo advances past a healthy target, and the target is cooled for an error the caller caused.

Fix, extending the existing mechanism rather than adding a parallel one:

• recognizedUpstreamError (src/lib/errors.ts) now also recognizes the four client classes: 400, 401, 403, and 404. Like rate_limit_error / overloaded_error, a recognized type applies only when no explicit code is present, and an explicit code equal to the class name is accepted (the same convention combo-stream-preflight already uses for code: "invalid_request_error"). The relay tail picks this up unchanged, so the declared type survives into response.failed. Codex retry behaviour is unchanged: Codex classifies by error.code, and the new codes are outside its fatal set exactly as upstream_server_error was.
• httpStatusFromTerminalError now checks for client-closed wording before the recognized lookup. Without this, a codeless invalid_request_error saying "client closed request" would answer 400 instead of 499.
• The non-streaming Messages path returns the recognized client status (below 429) for the collected error. Server classes and rate limits keep the 502 this path already returned. overloaded_error still answers 502, not 503 or 529.
• The docs that list the recognized bare-error classes are updated: structure/transports/responses-wire-shapes.md and docs-site/.../reference/management-api.md.

Request-log status for such a bare error now records the 4xx instead of the synthetic 502. That falls out of request-log-terminal-status.ts already routing through recognizedUpstreamError.

Verification

Base: upstream/dev @ 7640a942b. Bun 1.4.3 (the pinned testRunnerBun).

• New regression file tests/claude-integration/claude-client-refusal-status.test.ts, registered in scripts/test-layout/layout.json and tests/fixtures/test-layout-expected.json. It drives a real /v1/messages request through startServer against an openai-responses upstream that emits the bare error frame.
  • Red on unmodified src/: bun test tests/claude-integration/claude-client-refusal-status.test.ts: 1 pass / 6 fail (non-stream got 502 for each of the 4 classes; streaming got overloaded_error).
  • With only src/lib/errors.ts + relay.ts changed (non-stream half reverted): 3 pass / 4 fail. Both halves are needed.
  • With the client-closed check left in its old position: the 499 case fails. The move is needed.
  • Green: 8 pass / 0 fail.
• Focused suites: bun test tests/claude-integration/claude-client-refusal-status.test.ts tests/responses/sse-failed-tail.test.ts tests/server/relay-eager.test.ts tests/usage/request-log.test.ts tests/server/error-fidelity.test.ts tests/claude-integration/claude-outbound.test.ts tests/claude-integration/claude-messages-endpoint.test.ts tests/claude-integration/claude-529-mapping.test.ts tests/test-layout.test.ts tests/test-layout-tooling.test.ts tests/ci-workflows/file-size-ratchet.test.ts: 445 pass / 0 fail.
• bun test tests/ci-workflows: 1544 pass / 1 fail. The failure, bun-runtime.test.ts "PATH-selected process provenance…", fails identically on clean upstream/dev and is caused by the local Bun install path.
• bun run typecheck: clean.
• bun run structure:check: passed. bun run privacy:scan: passed.
• bun run test:changed (src/lib/errors.ts pulls in 1757 files): 38223 pass / 107 skip / 27 fail. None of the 27 is in the error, relay, or Claude path. I re-ran each failing file alone on both this branch and a clean upstream/dev worktree, with identical per-file results:
  • 7 reproduce on clean upstream/dev too: cli-connect-readiness 1, ocx-launcher-runtime 5, codex-runtime 1. These are local-environment failures.
  • 20 pass in isolation on both trees: cli-access-audio-live, native-codex-toggle, native-grok-toggle, service*. These are contention timeouts during the 1757-file run alongside other worktrees.
  • test:changed ran before the final amend, which added only the doc edits and the one 499 unit case.
• The full bun run test was not run separately: test:changed already covered 1757 of the files on this change, so the cross-platform remainder is left to CI.
• Maintainer fix 2c38e8051: httpStatusFromTerminalError keeps dev's order again. Only a recognized 400 yields to the client-closed (499) check, so a permission_error or rate_limit_error whose text contains client-closed wording still records 403 or 429 as it does on dev. The unit case covers both, and the KNOWN_BARE_ERROR_CODES comment now matches the set.
• Maintainer local evidence at 2c38e8051: the focused set (claude-client-refusal-status, sse-failed-tail, relay-eager, request-log, error-fidelity, claude-outbound, claude-messages-endpoint, claude-529-mapping) gave 409 pass / 0 fail. bun run typecheck and bun run structure:check are clean. bun run test:changed gave 38228 pass / 107 skip / 23 fail across 1757 files. Every failing file (cli-access-audio-live, native-codex-toggle, native-grok-toggle, codex-native-residue, service*, lab-fabric-task) passes in isolation, except sibling-home-client-sync "a secondary ensure parent…", which times out identically on a dev-equivalent tree. An independent review traced every recognizedUpstreamError / httpStatusFromTerminalError consumer and found no defects. Rate-limit, overload, and 5xx classes keep their retry behaviour, combo failover is unchanged, and the change merges cleanly with fix(bridge): end the turn on a terminal upstream refusal instead of a retryable incomplete #7152 and fix(responses): normalize explicit incomplete reasons #7122 and stays consistent with them.

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.

Review readiness checklist

This PR stays in draft until every box below is ticked. Tick all four boxes once the requirements are met:

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🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Upstream invalid-request, authentication, permission, and not-found errors now retain their corresponding HTTP status codes in Claude Messages responses.
  • Streaming responses preserve recognized error types, while client-closed messages continue to return status 499.
• Documentation
  • Clarified how recognized upstream errors are represented in diagnostic logs and synthesized streaming responses.

[coderabbitai]

📝 Walkthrough

Recognized upstream client-refusal errors now map to HTTP 400, 401, 403, or 404 in non-streaming Claude Messages responses. Client-closed messages retain status 499. Integration tests and reference documentation cover the mappings.

Changes: Client-Refusal Status Mapping

Layer / File(s)	Summary
Classify and return upstream error statuses src/lib/errors.ts, src/server/claude-messages.ts, src/server/relay.ts, docs-site/src/content/docs/reference/management-api.md, structure/transports/responses-wire-shapes.md	The error classifier recognizes four client-refusal classes and maps them to HTTP 400, 401, 403, and 404. Non-streaming Claude Messages responses use recognized client-error statuses. Client-closed messages retain status 499. The documentation describes the related mappings.
Verify status mappings and response bodies tests/claude-integration/claude-client-refusal-status.test.ts, scripts/test-layout/layout.json, tests/fixtures/test-layout-expected.json	Integration tests cover non-streaming statuses and error bodies, streaming error types, overloaded errors, and client-closed message handling. Test-layout mappings include the new test.

Priority: ⬇️ Low

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

Change: Bug fix

Suggested reviewers: lidge-jun

Merge Risk: 🔵 Low · up to d9b03

A client-closed Messages request can be reported as a 400 error instead of 499. This is a narrow status-mapping issue that should be fixed or explicitly accepted before merge.

Pre-merge checks: 5

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 4 files. (4 skipped: 4 u…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: Claude client-refusal errors are surfaced as 4xx responses instead of retryable 502 responses.

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[vadymhimself]

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/server/claude-messages.ts:
- Line 1565: Update the refusal-status selection around `refusalStatus` to
detect a translated `invalid_request_error` with a “client closed request”
message before using `recognizedUpstreamError`, and return status 499 to match
`httpStatusFromTerminalError`. Add an endpoint case alongside the existing
classifier test to verify this behavior.

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📥 Commits

Reviewing files that changed from the base of the PR and between 7640a94 and d9b0353.

📒 Files selected for processing: 8

• docs-site/src/content/docs/reference/management-api.md
• scripts/test-layout/layout.json
• src/lib/errors.ts
• src/server/claude-messages.ts
• src/server/relay.ts
• structure/transports/responses-wire-shapes.md
• tests/claude-integration/claude-client-refusal-status.test.ts
• tests/fixtures/test-layout-expected.json

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[lidge-jun]

Being carried into #7225 with your authorship preserved; this PR will be closed when the bundle lands.

[lidge-jun]

Landed on dev in 300e426 via #7225 (your change is its own commit in that bundle, and the squash keeps your authorship as Co-authored-by). Thank you!