# Sprint 4: Multi-Agent Coordination

**Status**: ✅ Complete
**Duration**: Week 4 (October 2025)
**Epic/Issues**: cf-21, cf-22, cf-23, cf-24

## Goal
Multiple agents work in parallel with dependency resolution.

## User Story
As a developer, I want to watch Backend, Frontend, and Test agents work simultaneously on independent tasks while respecting dependencies.

## Implementation Tasks

### Core Features (P0)
- [x] **cf-21**: Frontend Worker Agent - React/TypeScript code generation - cc8b46e
- [x] **cf-22**: Test Worker Agent - Unit test generation and execution - cc8b46e
- [x] **cf-23**: Task Dependency Resolution - DAG traversal and blocking - ce2bfdb
- [x] **cf-24**: Parallel Agent Execution - Multi-agent coordination - 8b7d692

### UI Enhancements (P1)
- [x] **Task 5.1**: AgentCard Component - Agent status display - b7e868b
- [x] **Task 5.2**: Dashboard State Management - React Context + useReducer - b7e868b

### Deferred Features (P1)
- [ ] **cf-24.5**: Subagent Spawning - Specialist subagents (future)
- [ ] **cf-24.6**: Claude Code Skills Integration - TDD/debugging skills (future)
- [ ] **cf-25**: Bottleneck Detection - Visual bottleneck alerts (future)

## Definition of Done
- [x] 3 agent types working (Backend, Frontend, Test)
- [x] Agents execute tasks in parallel
- [x] Dependencies respected (tasks wait when needed)
- [x] Dashboard shows all agents and their tasks
- [x] Progress bar updates as tasks complete
- [x] Agent pool with max concurrency limits
- [x] Real-time WebSocket updates for multi-agent coordination

## Key Commits
- `cc8b46e` - feat(sprint-4): Implement Phases 1-2 of Multi-Agent Coordination
- `ce2bfdb` - feat(sprint-4): Implement Phase 3-4 (Dependency Resolution & Agent Pool)
- `8b7d692` - feat(sprint-4): Implement Tasks 4.3-4.4 (Multi-Agent Integration)
- `f9db2fb` - feat(sprint-4): Complete backend implementation with bug fixes
- `c959937` - feat(sprint-4): Complete P1 tasks - dependency visualization and documentation
- `b7e868b` - feat(sprint-4): Complete UI tasks 5.1 & 5.2 - AgentCard and Dashboard state
- `0660ee4` - feat(frontend): implement multi-agent state management with React Context
- `ea76fef` - docs(sprint-4): Complete testing validation and sprint review preparation

## Metrics
- **Tests**: 150+ multi-agent coordination tests
- **Coverage**: 85%+ maintained
- **Pass Rate**: 100%
- **Agents**: 3 (Backend, Frontend, Test Worker Agents)
- **Max Concurrency**: 10 agents

## Key Features Delivered
- **Three Worker Agent Types**: Backend, Frontend, Test agents with specialized capabilities
- **Dependency Resolution**: DAG-based task ordering with automatic blocking/unblocking
- **Agent Pool**: Configurable max concurrency (default: 10 agents)
- **Parallel Execution**: True concurrent task execution with dependency respect
- **Multi-Agent State**: React Context + useReducer for centralized state management
- **AgentCard UI**: Real-time agent status display with current task and progress
- **WebSocket Integration**: Extended events for multi-agent coordination

## Sprint Retrospective

### What Went Well
- Dependency resolution DAG implementation clean and efficient
- Agent pool prevents resource exhaustion with max concurrency
- Frontend/Test agents reuse Backend agent patterns successfully
- React Context + useReducer provides excellent state management

### Challenges & Solutions
- **Challenge**: Thread-safe WebSocket broadcasts from multiple agents
  - **Solution**: Initial fix with `_broadcast_async()` wrapper (later improved in Sprint 5)
- **Challenge**: Complex state management for multiple agents
  - **Solution**: Centralized React Context with reducer pattern
- **Challenge**: Dependency deadlock detection
  - **Solution**: DAG traversal with cycle detection

### Key Learnings
- Agent pool pattern prevents thundering herd problems
- Dependency graphs need careful cycle detection
- Multi-agent state benefits from centralized management
- WebSocket broadcast coordination becomes complex with concurrency

### Technical Debt Created
- Threading model creates event loop deadlocks (resolved in Sprint 5)
- `run_in_executor()` wrapper adds unnecessary overhead (resolved in Sprint 5)
- Broadcast reliability issues from threaded context (resolved in Sprint 5)

## References
- **Beads**: cf-21, cf-22, cf-23, cf-24
- **Specs**: specs/sprint-4-multi-agent/
- **Docs**: claudedocs/SPRINT_4_FINAL_STATUS.md
