Fix #4888: Finalize pending api_req_started messages on task completion

[daniel-lxs]

Summary

Fixes #4888 by ensuring all pending api_req_started messages are properly finalized when a task completes, preventing UI spinners from persisting in task history.

Changes

Core Implementation

• Added finish() method to Task.ts: Finds all api_req_started messages without cost or cancelReason and sets their cost to 0
• Updated attemptCompletionTool.ts: Calls finish() before emitting taskCompleted to ensure all API requests are finalized

Testing

• Added comprehensive unit tests in Task.spec.ts:
  • Test that all pending api_req_started messages get finalized with cost: 0
  • Test that no unnecessary saves occur when no updates are needed
  • Test edge case with no api_req_started messages
  • Verification that ALL api_req_started messages have either cost or cancelReason after completion

Problem Solved

The issue occurred because when tasks completed, some api_req_started messages in the conversation history lacked both cost and cancelReason values. The UI component (ChatRow.tsx) shows a spinner for ANY api_req_started message missing these values, causing spinners to persist in completed task history.

Solution Approach

While operations run sequentially and theoretically only the last api_req_started could be unfinished, the UI checks ALL messages for the spinner condition. Rather than modifying the UI logic (which would require additional complexity), this solution ensures backend compatibility by finalizing all unfinished messages.

Testing

✅ All existing tests pass
✅ New unit tests cover the finish() method functionality
✅ Linting and type checking pass

Verification

After this fix:

• Completed tasks will have all api_req_started messages properly finalized
• No spinners will persist in task history
• UI behavior remains unchanged for active/streaming tasks

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Important

Adds finish() method to Task to finalize pending api_req_started messages, ensuring UI spinners do not persist.

• Behavior:
  • Adds finish() method to Task class in Task.ts to finalize api_req_started messages with no cost or cancelReason by setting cost to 0.
  • Updates attemptCompletionTool in attemptCompletionTool.ts to call finish() before emitting taskCompleted.
• Testing:
  • Adds unit tests in Task.spec.ts to verify finish() method finalizes messages correctly, handles cases with no updates, and processes scenarios with no api_req_started messages.

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[daniel-lxs]

@hannesrudolph Can you check if this PR solves the issue with a task that has any spinner?

I think this solution will only work with new tasks created since this checks the task when saving for any message that still has a spinner.