fix(core): prevent unhandled AbortError crash during stream loop detection

[7hokerz]

Summary

This PR resolves a critical bug where the CLI crashes with an unhandled AbortError during stream processing.

Details

The crash occurred in processTurn because controller.abort() was being invoked directly within the for await (const event of resultStream) iteration upon detecting a stream loop. This caused the underlying active stream to immediately throw an AbortError. Lacking a try...catch block, this resulted in an unhandled promise rejection that abruptly terminated the Node.js process.

To resolve this structurally, a loopDetectedAbort boolean flag was introduced. The logic now sets this flag and uses break to safely exit the asynchronous iteration first. The controller.abort() method is then called after the loop has gracefully terminated, preventing the exception from leaking into the active stream processing state.

Related Issues

Fixed #21122

How to Validate

1. Run Unit Tests: Execute the test suite containing the newly added test cases covering the loop detection scenario.

   # Example command
   npm test -w @google/gemini-cli-core -- src/core/client.test.ts

Expected Result: Tests should pass successfully without triggering any unhandled AbortError rejections.

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 resolves a critical bug in the CLI that caused unhandled AbortError crashes during stream processing when a loop was detected. The fix introduces a flag to handle the abort signal more gracefully, preventing the error from crashing the application. A new unit test has been added to validate the fix.

Highlights

• Bug Fix: Addresses a critical issue where the CLI was crashing due to an unhandled AbortError during stream processing when a loop was detected.
• Structural Solution: Introduces a loopDetectedAbort flag to ensure the asynchronous iteration is exited gracefully before calling controller.abort(), preventing the exception from leaking.
• Test Coverage: Includes a new unit test to specifically cover the loop detection scenario and ensure no unhandled AbortError rejections occur.

Changelog

• packages/core/src/core/client.test.ts
  • Added a unit test to verify that the stream aborts cleanly and returns a Turn instance when a loop is detected, without causing unhandled promise rejections.
• packages/core/src/core/client.ts
  • Introduced a loopDetectedAbort flag to handle stream loop detection and prevent unhandled AbortErrors.

Activity

• The PR introduces a loopDetectedAbort flag to prevent unhandled AbortErrors during stream processing.
• A new unit test was added to specifically validate the fix for the loop detection scenario.
• The changes ensure that the abort signal is handled gracefully, preventing application crashes.

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[gsquared94]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses a crash caused by an unhandled AbortError during stream processing when a loop is detected. The fix defers aborting the stream's controller until after the stream iteration loop is exited, preventing the error. A new unit test is added to verify this behavior and prevent regressions. The changes are confined to packages/core/src/core/client.ts and its corresponding test file.

[gemini-code-assist]

Code Review

This pull request addresses a critical unhandled AbortError crash that occurs during stream processing when a loop is detected. The fix correctly defers the call to controller.abort() until after the stream's for await loop has been safely exited using a break statement, preventing the unhandled promise rejection. The changes are sound, and the new unit test effectively validates that the fix works as expected without introducing regressions.

[ruomengz]

Thanks for the fix! It looks good, but there is a merge conflict in packages/core/src/core/client.ts. Could you please sync with main and resolve that? I've approved the workflows so we can see the CI results once the conflict is cleared.

[7hokerz]

@ruomengz, I've resolved the conflicts and restructured the code to align with the updated architecture.

[gemini-code-assist]

Code Review

This pull request addresses a crash that occurred when an AbortError was thrown from within an active asynchronous stream iteration. The fix involves deferring the abort() call until after the stream's for await...of loop has terminated. This is achieved by setting a flag within the loop and then acting on it after the loop breaks. This pattern is also applied to the loop recovery logic, which could also trigger an abort. A new unit test has been added to verify that the stream now completes gracefully under these conditions.

[7hokerz]

@ruomengz , Could you please run CI?

[7hokerz]

@ruomengz , A particular test fails due to a timeout, what should I do?