Vouch request: fix 401 Insufficient balance retry classification

[JagravNaik]

Hi there,

I would like to be vouched so my PR can be reviewed and merged. I have identified and implemented a fix for an issue where OpenCode Go 401 Insufficient balance errors are not triggering OMP's retry/fallback pipeline.

Problem

OpenCode Go returns 401 Insufficient balance when quota is exhausted. This phrasing is not matched by USAGE_LIMIT_PATTERN in packages/ai/src/rate-limit-utils.ts, so isUsageLimitError() returns false, the retry pipeline never engages, and fallback chains (retry.fallbackChains) are never consulted.

Fix (PR #3102)

Two-line change in packages/ai/src/rate-limit-utils.ts:

• Add insufficient.?balance to USAGE_LIMIT_PATTERN
• Add insufficient balance check to parseRateLimitReason → QUOTA_EXHAUSTED

Testing

Unit: 18/18 pass (2 new test cases added for isUsageLimitError and parseRateLimitReason with the actual OpenCode Go 401 response body)

Live end-to-end: Built locally and ran against an exhausted OpenCode Go account with a fallback chain configured. The retry pipeline engaged and the fallback fired correctly:

Error: 401 Insufficient balance. …
Warning: Fallback: opencode-go/<model> → <fallback-provider>/<model>
Fallback succeeded on <fallback-provider>/<model>

Before this fix, the same exhausted account errored out immediately with no retry or fallback attempt.

Thanks!

[can1357]

!vouch @JagravNaik 🫡