* fix(subagents): cleanup background tasks after completion to prevent memory leak
Added cleanup_background_task() function to remove completed subagent results
from the global _background_tasks dict. Found a small issue: completed tasks
were never removed, causing memory to grow indefinitely with each subagent
execution.
Alternative approaches considered:
- Future + SubagentHandle pattern: Not chosen due to requiring refactoring
Chose the simple cleanup approach for minimal code changes while effectively
resolving the memory leak.
Changes:
- Add cleanup_background_task() in executor.py
- Call cleanup in all task_tool return paths (completed, failed, timed out)
* fix(subagents): prevent race condition in background task cleanup
Address Copilot review feedback on memory leak fix:
- Add terminal state check in cleanup_background_task() to only remove
tasks that are COMPLETED/FAILED/TIMED_OUT or have completed_at set
- Remove cleanup call from polling safety-timeout branch in task_tool
since the task may still be running
- Add comprehensive tests for cleanup behavior including:
- Verification that cleanup is called on terminal states
- Verification that cleanup is NOT called on polling timeout
- Tests for terminal state check logic in executor
This prevents KeyError when the background executor tries to update
a task that was prematurely removed from _background_tasks.
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
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