fix(checkpoint): degrade non-array history instead of crashing resume

[soroush5]

Summary

A checkpoint file with valid JSON but a non-array history crashed /resume resume with a raw TypeError. loadCheckpoint now verifies the shape and degrades to an empty checkpoint, like it already does for unparseable files.

Details

The object branch of loadCheckpoint only checked that the history key exists, then handed the raw value to resume — where null.length / number.slice threw. Corrupt shapes like these come from a crash mid-save, a full disk, or a hand edit. The fix checks Array.isArray before returning parsed content; anything else falls through to the existing corrupt-file warning + empty checkpoint. Valid checkpoints (including extra fields like authType) are untouched.

Related Issues

Fixes #29194

How to Validate

1. npx vitest run src/core/logger.test.ts in packages/core — 41 passed, including 2 new wrong-shape regressions (null/number history).
2. npm run preflight-relevant gates on touched files: ESLint zero warnings, Prettier clean.

• Tests added, all passing
• No breaking change (only corrupt files change behavior: clean miss instead of throw)
• Validated on macOS; pure Node fs/path logic, platform-independent

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[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 addresses a stability issue where malformed checkpoint files containing non-array history data would cause the application to crash during the resume process. By validating the structure of the loaded checkpoint data, the system now gracefully degrades to an empty state when encountering corrupted files, ensuring consistent behavior across different failure scenarios.

Highlights

• Robustness Improvement: Added a validation check in loadCheckpoint to ensure the history field is an array, preventing runtime crashes when encountering malformed checkpoint files.
• Graceful Degradation: Implemented logic to treat checkpoints with non-array history as corrupt, causing them to fall back to an empty checkpoint state instead of throwing a TypeError.
• Regression Testing: Added new test cases in logger.test.ts to verify that null or numeric history values are handled correctly without crashing.

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[github-actions]

📊 PR Size: size/S

• Lines changed: 28
• Additions: +26
• Deletions: -2
• Files changed: 2

[gemini-code-assist]

Code Review

This pull request ensures that the 'history' property of a loaded checkpoint is validated as an array before returning it. If the history is not an array (e.g., due to file corruption), it is handled gracefully as a corrupt file, returning an empty history. Unit tests have been added to verify this behavior. I have no further feedback to provide.

[soroush5]

/cla-check