# Sprint 5: Async Worker Agents

**Status**: ✅ Complete
**Duration**: Week 5 (November 2025)
**Epic/Issues**: cf-48

## Goal
Convert worker agents from synchronous to asynchronous execution to resolve event loop deadlocks.

## User Story
As a developer, I want worker agents to broadcast WebSocket updates reliably without threading deadlocks or race conditions.

## Implementation Tasks

### Core Features (P0)
- [x] **Phase 1**: Convert BackendWorkerAgent to async/await - 9ff2540
- [x] **Phase 2**: Convert FrontendWorkerAgent to async/await - 9ff2540
- [x] **Phase 3**: Convert TestWorkerAgent to async/await - 9ff2540
- [x] **Phase 4**: Migrate all worker agent tests to async - 8e91e9f, 324e555, b4b61bf
- [x] **Phase 5**: Complete self-correction integration tests - debcf57

## Definition of Done
- [x] All worker agents use `async def execute_task()`
- [x] LeadAgent removes `run_in_executor()` wrapper
- [x] Direct `await broadcast_*()` calls instead of `_broadcast_async()`
- [x] All existing tests updated to async patterns
- [x] WebSocket broadcasts work reliably
- [x] No event loop deadlocks
- [x] 100% test pass rate maintained

## Key Commits
- `9ff2540` - feat: convert worker agents to async/await (cf-48 Phase 1-3)
- `8e91e9f` - test: migrate frontend and backend worker tests to async
- `324e555` - fix: correct async test migration issues
- `b4b61bf` - test: migrate all worker agent tests to async/await
- `debcf57` - fix: complete async migration for self-correction integration tests
- `4e13667` - Merge pull request #11 from frankbria/048-async-worker-agents
- `084b524` - docs: update README with Sprint 5 async migration details

## Architecture Changes

### Before (Sync + Threading)
```python
# LeadAgent
await loop.run_in_executor(None, agent.execute_task, task_id)

# Worker Agent
def execute_task(self, task_id):
    self._broadcast_async("task_status_changed", ...)  # DEADLOCK
```

### After (Native Async)
```python
# LeadAgent
await agent.execute_task(task_id)

# Worker Agent
async def execute_task(self, task_id):
    await broadcast_task_status(...)  # WORKS
```

## Metrics
- **Tests**: 150+ async tests migrated
- **Coverage**: 85%+ maintained
- **Pass Rate**: 100%
- **Agents**: 3 (all async)
- **Performance**: Reduced threading overhead

## Key Features Delivered
- **Native Async Execution**: All worker agents use proper async/await
- **AsyncAnthropic Client**: Replaced sync Anthropic client
- **Reliable Broadcasts**: Direct async WebSocket broadcasts without deadlocks
- **Thread-Free**: Eliminated `run_in_executor()` wrapper
- **Better Error Handling**: Proper async exception handling and cancellation
- **True Concurrency**: Cooperative multitasking without thread overhead

## Problem Statement (Sprint 4 Technical Debt)

### Root Cause
- Worker agents used sync `execute_task()` methods
- LeadAgent wrapped calls in `loop.run_in_executor()`
- Agents tried to broadcast from thread pool context
- Event loop access from threads caused deadlocks

### Symptoms
- WebSocket broadcast failures
- Event loop deadlock errors
- Unpredictable broadcast delivery
- Thread context switching overhead

## Sprint Retrospective

### What Went Well
- Clean async migration without major breaking changes
- All Sprint 3 and Sprint 4 tests continue passing
- Broadcast reliability significantly improved
- Threading overhead eliminated

### Challenges & Solutions
- **Challenge**: AsyncAnthropic API differences from sync client
  - **Solution**: Updated all LLM call sites to use async methods
- **Challenge**: Test migration complexity (150+ tests)
  - **Solution**: Phased migration with validation at each step
- **Challenge**: Self-correction loop async conversion
  - **Solution**: Careful refactoring with comprehensive integration tests

### Key Learnings
- Threading and async don't mix well - use one or the other
- AsyncAnthropic client requires different initialization
- Test migration benefits from automated tools (pytest-asyncio)
- Proper async architecture simpler than sync + threading

### Performance Improvements
- Eliminated thread pool overhead
- Faster WebSocket broadcast delivery
- Better CPU utilization with cooperative multitasking
- Reduced memory footprint (no thread stacks)

## References
- **Beads**: cf-48
- **Specs**: specs/048-async-worker-agents/spec.md
- **Docs**: claudedocs/SPRINT_4_FINAL_STATUS.md (problem diagnosis)
- **Branch**: 048-async-worker-agents
- **PR**: #11
