[BUG] A2A Tasks cancellation didn't work

[edenreich]

Summary

The last changes probably with making it more types safe broke the tasks cancellation, I have to check why.

When I submit the task to the A2A server and then visit /tasks and press "c" to cancel it just disappears from the tasks list and the a2a server still shows activity (didn't received the cancellation token).

[edenreich]

@claude Can you check why this didn't work?

[claude]

Claude finished @edenreich's task —— View job • claude/issue-195-20251022-1634 • Create PR ➔

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A2A Task Cancellation Issue - FIXED! ✅

I've successfully identified and fixed the A2A task cancellation bug.

Todo List:

• Read repository setup and development guidelines
• Search for A2A task cancellation related code
• Analyze the task cancellation flow
• Examine recent commits for type safety changes
• Identify the bug in the cancellation logic
• Fix the identified issue
• Test the solution and run quality checks
• Commit changes and create PR

Root Cause & Fix 🔧

The Problem: Race condition in BackgroundTaskService.CancelBackgroundTask()

The method was using a stale copy of TaskPollingState from GetBackgroundTasks() instead of getting the live polling state from the task tracker. This caused:

1. ✅ Task cleanup happened (removed from UI list)
2. ❌ Wrong CancelFunc() called (from stale copy)
3. ❌ Background polling goroutine kept running
4. ❌ A2A server never received cancellation

The Fix: Changed line 63 in background_task_service.go:

// OLD - used stale copy:
backgroundTasks := s.GetBackgroundTasks()
targetTask := &backgroundTasks[i] // ❌ stale copy

// NEW - gets live state:
targetTask := s.taskTracker.GetPollingState(taskID) // ✅ live state

Changes Made:

• internal/services/background_task_service.go - Fixed the race condition
• All tests pass ✅
• Code formatting and linting pass ✅

Testing:

Now when you:

1. Submit an A2A task
2. Visit /tasks
3. Press "c" to cancel

The task will be properly cancelled AND the A2A server will receive the cancellation token.

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