fix(core): honor retryDelay in RetryInfo for 503 errors

[yunaseoul]

Summary

This PR fixes a bug where gemini-cli was incorrectly terminating sessions with a hard quota error when receiving HTTP 503 MODEL_CAPACITY_EXHAUSTED responses.

The fix modifies classifyGoogleError to properly parse the RetryInfo embedded within 503 errors and treat them as transient RetryableQuotaErrors, thereby allowing the CLI's backoff system to honor the server-provided retryDelay.

Details

Previously, 503 errors returned early from the error classification logic, returning a generic retryable error that did not capture any delay specified by the server. We updated the parser to route 503s through the same detailed analysis used for 429 and 499 errors.

Also fixed a related sticky state persistence issue in ModelAvailabilityService. resetTurn() was correctly resetting the consumed flag but was not removing the sticky_retry state. This meant that any model that experienced a single transient error would be permanently limited to 1 attempt per turn for the rest of the session. Now, resetTurn() completely clears the sticky_retry state, so transient errors don't limit subsequent turns.

Related Issues

Fixes #24815

How to Validate

1. Run the test suite: npm run test
2. Ensure modelAvailabilityService.test.ts passes and googleQuotaErrors.test.ts passes.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request improves the robustness of the gemini-cli error handling mechanism. By updating the classification logic for 503 Service Unavailable errors, the system now properly respects server-side retry instructions instead of incorrectly terminating sessions. Additionally, the change addresses a state management bug that previously caused transient errors to unfairly penalize subsequent turns in a session.

Highlights

• Error Classification Update: Modified classifyGoogleError to correctly parse RetryInfo from 503 errors, ensuring the CLI's backoff system honors server-provided retry delays.
• Code Refactoring: Introduced a GoogleApiType enum to standardize error detail type checking and cleaned up redundant string template literals.
• Bug Fix: Resolved a sticky state persistence issue in ModelAvailabilityService where resetTurn() failed to clear sticky_retry state, causing unnecessary session limitations.

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[github-actions]

Size Change: -373 B (0%)

Total Size: 34 MB

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[gemini-code-assist]

Code Review

This pull request updates the error classification logic in packages/core to include 503 Service Unavailable errors as retryable, alongside 429 and 499 errors. It introduces a GoogleApiType enum to centralize API type string constants, refactors classification logic to use these constants, and adds a new unit test to verify the handling of 503 errors with RetryInfo. I have no feedback to provide as the changes are clean and well-structured.