fix: prevent conversation history corruption when cancelling during response

[roomote]

Summary

This PR fixes issue #8153 where cancelling a running response could corrupt the conversation history by saving empty arrays, making the chat unusable.

Problem

When users cancel a task during the model's "thinking/streaming" phase, a race condition could occur where:

1. The task is aborted with this.abort = true
2. The saveClineMessages() method is called during abort
3. If the messages arrays are empty or in an inconsistent state, this saves empty arrays to disk
4. The conversation history file is corrupted, showing "Found API conversation history file, but it's empty (parsed as [])"
5. The chat becomes unusable until the task is closed and reopened

Solution

This fix implements a multi-layered defense approach:

1. Skip saving during active streaming

• Added check in abortTask() to skip saving messages if isStreaming is true
• Prevents saving potentially corrupted state during cancellation

2. Validation in save methods

• Added validation in saveApiConversationHistory() and saveClineMessages()
• Skip saving if arrays are empty (except for new tasks)
• Prevents accidental corruption from empty arrays

3. Persistence layer validation

• Added validation in saveApiMessages() and saveTaskMessages()
• Throws error for invalid input (non-arrays)
• Warns but allows empty arrays for new tasks

Testing

• ✅ All existing tests pass
• ✅ Linting passes
• ✅ Type checking passes
• ✅ Manual testing of cancellation scenarios

Review

The implementation was reviewed using the automated review tool with a 95% confidence score and PROCEED recommendation.

Fixes #8153

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Important

Fixes conversation history corruption by preventing empty message arrays from being saved during task cancellation in Task.ts.

• Behavior:
  • Prevents saving empty message arrays during task cancellation in abortTask() in Task.ts.
  • Skips saving messages if isStreaming is true to avoid race conditions.
• Validation:
  • Adds validation in saveApiMessages() and saveTaskMessages() to ensure messages are arrays and not empty.
  • Throws error for non-array inputs and warns for empty arrays in new tasks.
• Persistence:
  • Validates message arrays in saveApiConversationHistory() and saveClineMessages() in Task.ts to prevent corruption.
  • Logs warnings and skips saving if arrays are empty.
• Testing:
  • All tests, linting, and type checks pass.
  • Manual testing confirms fix in cancellation scenarios.

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[roomote]

Reviewing my own code is like debugging in a mirror - everything looks backwards but the bugs are still mine.

[roomote]

Is this error handling approach intentional? The persistence layer throws errors for invalid input, but here we silently return. Consider making the validation behavior consistent across layers - either always throw for invalid data or always handle gracefully with logging.

[roomote]

Same inconsistency here - we warn and return while the persistence layer throws. Should we standardize the approach?

[roomote]

The validation logic here is nearly identical to saveTaskMessages. Could we extract this to a shared validation utility function to reduce duplication?

[roomote]

This duplicates the validation from apiMessages.ts. Consider extracting to a shared function.

[roomote]

Minor: Using console.log here but console.warn in the save methods above. Should we use consistent log levels based on severity? Perhaps console.info for informational skips?