task-decomposition

This skill provides methodology for decomposing complex tasks into independent, parallelizable units that can be executed by multiple engineers simultaneously.

When to Invoke This Skill

Automatically activate for:

• Complex features requiring multiple components
• Large refactoring spanning many files
• Multi-domain work (frontend + backend + database)
• Any task where "this could be parallelized" applies
• Planning sprints or implementation roadmaps

Task Decomposition Principles

1. Independence First

Tasks must be independent to run in parallel:

GOOD: Each task can complete without waiting
┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐
│ Task A: Auth UI │  │ Task B: Auth API│  │ Task C: DB Schema│
│ (no deps)       │  │ (no deps)       │  │ (no deps)        │
└─────────────────┘  └─────────────────┘  └─────────────────┘

BAD: Sequential dependency chain
Task A → Task B → Task C (no parallelism possible)

2. Clear Boundaries

Each task must have:

• Single responsibility: One deliverable per task
• Defined inputs: What data/context is needed
• Expected outputs: What artifact is produced
• Acceptance criteria: How to verify completion

3. Right-Sized Tasks

Size	Duration	Complexity	Assignment
Small	< 30 min	Single file, routine	Junior engineer
Medium	30-60 min	Multi-file, some decisions	Senior engineer
Large	1-2 hours	Cross-cutting, architectural	Lead or split further

Rule: If a task is "Large", decompose it further.

Decomposition Framework

Step 1: Identify Domains

Map the work to distinct domains:

Feature: User Authentication
├── Frontend Domain
│   ├── Login form component
│   ├── Registration flow
│   └── Password reset UI
├── Backend Domain
│   ├── Auth middleware
│   ├── JWT token service
│   └── User validation
├── Data Domain
│   ├── User schema
│   ├── Session storage
│   └── Migration scripts
└── Infrastructure Domain
    ├── OAuth provider setup
    └── Environment config

Step 2: Map Dependencies

Create dependency graph:

[DB Schema] ──┬──> [Auth Middleware] ──> [Integration Tests]
              │
              ├──> [JWT Service]
              │
              └──> [User Validation]

[Login UI] ────────────────────────────> [E2E Tests]
[Registration UI] ─────────────────────> [E2E Tests]

Step 3: Identify Parallel Lanes

Group independent tasks into lanes:

Lane 1 (Backend)     Lane 2 (Frontend)    Lane 3 (Infra)
─────────────────    ─────────────────    ─────────────────
[DB Schema]          [Login UI]           [OAuth Setup]
     │               [Registration UI]    [Env Config]
     ▼               [Reset UI]
[Auth Middleware]
[JWT Service]
[User Validation]

Step 4: Define Integration Points

Where lanes must synchronize:

Sync Point 1: API Contract
- Backend exposes POST /auth/login
- Frontend implements against contract
- Both can develop in parallel with mock

Sync Point 2: Integration Testing
- All lanes complete
- Run integration test suite
- Fix cross-cutting issues

Task Template

Use this template for each decomposed task:

## Task: [Clear, action-oriented title]

**Lane**: [Backend | Frontend | Infra | Data]
**Size**: [Small | Medium]
**Dependencies**: [None | Task IDs that must complete first]

### Context
[1-2 sentences on why this task exists]

### Deliverables
- [ ] [Specific artifact 1]
- [ ] [Specific artifact 2]

### Acceptance Criteria
- [ ] [Measurable criterion 1]
- [ ] [Measurable criterion 2]
- [ ] Tests pass
- [ ] Linting clean

### Notes
[Any implementation hints or decisions already made]

Parallelization Patterns

Pattern 1: Component Parallel

Split by UI component when each is independent:

/leader --team-size=3 --mode=parallel

Task 1: Build LoginForm component
Task 2: Build RegistrationForm component
Task 3: Build PasswordResetForm component

Pattern 2: Layer Parallel

Split by architectural layer:

/leader --team-size=3 --mode=parallel

Task 1: Implement API endpoints (backend)
Task 2: Implement UI components (frontend)
Task 3: Set up infrastructure (devops)

Pattern 3: Hybrid

Critical path sequential, supporting work parallel:

/leader --team-size=3 --mode=hybrid

Sequential (Critical Path):
  Task 1: Design database schema
  Task 2: Implement core API

Parallel (After Task 1):
  Task 3: Build UI components
  Task 4: Write integration tests
  Task 5: Set up monitoring

Anti-Patterns to Avoid

Over-Decomposition

BAD: 20 tiny tasks that have coordination overhead
GOOD: 3-5 meaningful tasks per engineer

Hidden Dependencies

BAD: "Task B assumes Task A's schema design"
GOOD: "Task B depends on Task A (schema must be finalized)"

Unclear Ownership

BAD: "Someone should handle auth"
GOOD: "Engineer 2 owns auth middleware (Task B)"

Missing Integration Plan

BAD: 5 parallel tasks with no sync point
GOOD: Parallel tasks + defined integration checkpoint

Output Format

When decomposing tasks, produce:

## Task Decomposition: [Feature Name]

### Overview
- Total tasks: N
- Parallel lanes: M
- Critical path: [sequence]
- Estimated parallelism: X%

### Dependency Graph
[ASCII diagram showing task relationships]

### Task Breakdown

#### Lane 1: [Domain]
| ID | Task | Size | Deps | Engineer |
|----|------|------|------|----------|
| T1 | ... | Medium | None | Senior 1 |
| T2 | ... | Small | T1 | Senior 1 |

#### Lane 2: [Domain]
| ID | Task | Size | Deps | Engineer |
|----|------|------|------|----------|
| T3 | ... | Medium | None | Senior 2 |

### Integration Points
1. After T1, T3: API contract validation
2. After all: Full integration test

### Execution Plan
Phase 1: T1, T3, T5 (parallel)
Phase 2: T2, T4 (parallel, after Phase 1)
Phase 3: Integration (sequential)

Checklist

Before finalizing decomposition:

• Each task has single responsibility
• Dependencies are explicit (not assumed)
• No task exceeds "Medium" size
• Integration points defined
• Ownership is clear
• Acceptance criteria are testable
• Critical path identified
• Parallelism opportunities maximized