fix(sse): repair orphaned PROVIDER_BREAKER_FAILURE_STATUSES reference on the all-rate-limited path

[diegosouzapw]

Root cause

#8013 extracted shouldTripProviderBreakerForResult() from src/sse/handlers/chat.ts into the new src/sse/handlers/chatPredicates.ts, taking the (non-exported) const PROVIDER_BREAKER_FAILURE_STATUSES = new Set([408, 500, 502, 503, 504]) with it.

A second, independent use of that const survived in chat.ts's handleSingleModelChat(), in the "all credentials rate-limited" block (~line 1340):

if (!forceLiveComboTest && credentials?.allRateLimited && PROVIDER_BREAKER_FAILURE_STATUSES.has(breakerFailureStatus)) {
  breaker._onFailure();
}

The extraction removed the local declaration but left this second reference behind, orphaned.

Production impact

Any request where every credential for a provider+model is simultaneously rate-limited hits ReferenceError: PROVIDER_BREAKER_FAILURE_STATUSES is not defined at runtime in this code path. Concretely:

• breaker._onFailure() was unreachable on the all-rate-limited path — the provider circuit breaker could never trip from it.
• The uncaught ReferenceError propagated up and got mapped to a generic 502, masking the real 503 upstream-unavailable status in combo responses.
• The issue-agent route surfaced a generic 400 instead of the actual 429 provider-rate-limited response.

This sits in the central chat resilience path (handleSingleModelChat), so it fires for any provider whenever all of its credentials are simultaneously cooling down — not an edge case.

Fix

Two-line production fix, no behavior change:

• src/sse/handlers/chatPredicates.ts: export PROVIDER_BREAKER_FAILURE_STATUSES.
• src/sse/handlers/chat.ts: add it to the existing import block from ./chatPredicates.

The classification set ([408, 500, 502, 503, 504]) is unchanged — this only repairs the broken reference.

Also re-points tests/unit/nvidia-quota-phase1.test.ts's regex-based declaration check at chatPredicates.ts, where the const now actually lives (it previously read chat.ts via fs+regex and silently failed to find the declaration — a stale test left behind by the same #8013 extraction). The regex and the classification assertions are unchanged; the test still proves 429 is excluded from the whole-provider breaker.

Validation (TDD — red before fix, green after)

All 6 affected files run sequentially with env -u OMNIROUTE_API_KEY:

Test file	Before	After
tests/unit/chat-rate-limit-body-lock.test.ts	0/2 (2 ReferenceError)	2/2
tests/unit/chat-cooldown-aware-retry.test.ts	4/6 (2 ReferenceError)	6/6
tests/unit/chat-combo-live-test.test.ts	4/5 (1 ReferenceError)	5/5
tests/unit/chat-route-coverage.test.ts	12/15 (503→502 masked + 2 ReferenceError)	15/15
tests/unit/issue-agent-route-execution.test.ts	1/2 (400 instead of 429)	2/2
tests/unit/nvidia-quota-phase1.test.ts	12/13 (regex found no declaration)	13/13
Total	33/43	43/43

Also verified:

• npm run typecheck:core — clean.
• npx eslint on the 3 changed files — clean.
• Adjacent tests/unit/combo-breaker-429.test.ts (uses a deliberately independent, locally-declared const of the same name in open-sse/services/combo/comboPredicates.ts, to avoid an open-sse → src/sse import cycle) — unaffected, still 9/9 green. Confirms this fix is contained to the orphaned single-model path and does not touch the separate combo-layer classification.

Refs #8013