Error-class-bound fallthrough for OpenRouter models[] fallback#334
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Add an optional `fallthrough?: boolean` to the ErrorResponse fixture type. In the OpenRouter models[] fallback loop, when a matched error response sets `fallthrough: false`, treat it as terminal (stop the loop, serve that error, no failover) instead of falling through to the next candidate. Absent/`true` keeps the current backward-compatible fall-through. This reproduces OpenRouter's inconsistent-by-error-class failover: a 403 budget-exceeded / generic provider error is served as terminal, while 429/503 fail over. The per-fixture gate composes with the request-level `provider.allow_fallbacks`: fall-through happens only when BOTH allow it. Threads the field through types.ts (ErrorResponse) and the fixture-loader (response-level, carried by the existing normalizeResponse shallow clone). validateFixtures rejects a non-boolean `fallthrough` at load, so the fail-closed half cannot silently fail open on a "false"/0/null author typo. Documents it in the OpenRouter docs fallback section and write-fixtures skill.
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July 23, 2026 01:54
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Error-class-bound fallthrough for the OpenRouter
models[]fallback engineFollow-up to #328. That PR shipped
models[]failover (an error-fixture candidate falls through to the next model, unlessprovider.allow_fallbacks:false). But real OpenRouter fails over inconsistently by error class — the loudest authentic user complaint (openclaw#60191, #45834, #19249): a403 budget-exceededor generic "provider error" does not advance to the next model (it retries the same primary), while 429/503 do. Users can't rehearse that.What this adds
An optional
fallthrough?: booleanon the error fixture response:models[]candidate (fully backward-compatible).fallthrough: false→ the error is terminal: the loop stops and serves that error, no failover — reproducing "this error class doesn't fail over."It composes with the request-level
provider.allow_fallbacks:false(either signal makes an error terminal). A dev models an error class by settingfallthrough:falseon that class's fixture (e.g. the 403) and leaving 429/503 fixtures to default — so they can reproduce the exact failure that burned them and assert their handling, and the positive "fallback saved me" path.Correctness
validateFixturesrejects a non-booleanfallthrough("false",0,null) — without this, a JSON author's"false"string would silently invert TERMINAL→fall-through (fail-closed quietly failing open).response.model; a terminal error is served as the OpenRouter error envelope ({error:{code,message,metadata?}}, nomodelfield).Testing / review
fallthrough:falseterminal, default fall-through, composition, and the non-boolean load-time rejection.pnpm test); tsc/lint/build/exports clean. No version bump (release is separate).🤖 Generated with Claude Code
https://claude.ai/code/session_018yy1y2Cwc31DaB4UNqvT8K