# Trinity Task Decomposition - EUS

**Command:** `/planning:trinity-decompose`
**Purpose:** Decompose work into atomic tasks using EUS (Task Decomposer)
**Architecture:** EUS task breakdown → Atomic task validation → TDD cycle planning
**Trinity Version:** 2.1.0
**Last Updated:** 2026-01-21

**Agent:** EUS (Task Decomposer)
**Role:** Break work into atomic tasks following "1 task = 1 commit" rule

## What EUS Does

1. **Atomic Task Breakdown:**
   - Each task = 1 commit
   - Maximum 2 hours per task
   - Single responsibility per task
   - Clear success criteria

2. **Task Independence:**
   - Minimal cross-dependencies
   - Can be tested in isolation
   - Clear input/output boundaries

3. **Commit Message Planning:**
   - Conventional commits format
   - `feat:`, `fix:`, `refactor:`, `test:`, `docs:`
   - Descriptive and concise

4. **TDD Enforcement:**
   - RED: Write failing test
   - GREEN: Minimal code to pass
   - REFACTOR: Clean up
   - Each cycle = 1 commit

## Output Format

EUS produces structured JSON handoff:

```json
{
  "atomicTasks": [
    {
      "id": 1,
      "description": "Implement validation logic",
      "commitMessage": "feat(validator): add input validation",
      "estimatedTime": "45min",
      "testStrategy": "Unit tests for edge cases",
      "successCriteria": "All validation tests pass",
      "dependencies": []
    }
  ],
  "tddCycles": [
    {
      "test": "test description",
      "implementation": "impl description",
      "refactor": "refactor description"
    }
  ]
}

EUS Agent Capabilities

EUS specializes in atomic task decomposition following Trinity principles:

Atomic Breakdown: "1 task = 1 commit" rule ensures clean version control
TDD Enforcement: Every task follows RED-GREEN-REFACTOR cycle
Task Independence: Minimal cross-dependencies enable parallel development
Time Boxing: Maximum 2 hours per task for manageable implementation

Integration with Trinity Workflow

EUS's task decomposition follows TRA's strategic planning:

After TRA: Strategic plan created with high-level tasks
EUS Decomposition (Claude adopts EUS persona): Breaks tasks into atomic units (1 commit each)
KIL Execution: Each atomic task implemented following TDD cycle
TDD Cycles: RED (test) → GREEN (implement) → REFACTOR (clean)
BAS Quality Gates: Validate after each atomic task commit

Example workflow:

Phase 3: Implementation
├── EUS Decomposition: Break plan into atomic tasks
│   Output: 12 atomic tasks (each ≤2 hours)
│   Each task = 1 TDD cycle = 1 commit
│
└── KIL Implementation: Execute atomic tasks
    ├── Atomic Task 1: Add validation logic → BAS gates
    ├── Atomic Task 2: Create service layer → BAS gates
    ├── Atomic Task 3: Implement error handling → BAS gates
    └── ... (continue until all tasks complete)

See Also: /trinity-orchestrate for complete workflow planning

Scale-Based Task Decomposition

EUS adjusts decomposition granularity based on task scale:

Small workflows: 2-4 atomic tasks (direct implementation)
Medium workflows: 6-10 atomic tasks (phased approach)
Large workflows: 12-20 atomic tasks (comprehensive breakdown)

Each atomic task always follows Trinity principles:

Maximum 2 hours duration
Single responsibility (one purpose)
Clear success criteria (testable)
BAS quality gate validation (6 phases)

Usage

Provide implementation plan and Claude (as EUS) will decompose into atomic tasks:

What is the implementation plan? (Or provide TRA's output)

For complete workflow planning:

Use /trinity-orchestrate to plan your implementation with EUS decomposition as a key phase

Conventional Commits Quick Reference

Trinity uses Conventional Commits for atomic task commits (1 task = 1 commit).

Format

<type>(<scope>): <subject>

<body>

<footer>

Types

feat: New feature
fix: Bug fix
refactor: Code change (no feature/fix)
test: Add/update tests
docs: Documentation only
style: Formatting (no code change)
perf: Performance improvement
chore: Build/tooling changes

Examples

Feature:

feat(auth): add JWT refresh token endpoint

Implement POST /auth/refresh endpoint with token rotation.
Uses HttpOnly cookies for security.

Closes #42

Fix:

fix(auth): validate token expiration correctly

Token expiration was checked against wrong timestamp.
Now uses UTC comparison.

Fixes #128

Refactor:

refactor(validation): extract email validator to utility

Reduces code duplication across 3 files.
Maintains same validation logic.

Trinity Best Practices

One Task = One Commit: Each EUS task gets exactly one commit
Atomic: Commit must be complete (tests pass, build succeeds)
Descriptive: Subject line explains "what", body explains "why"
Reference Issues: Link to work orders (e.g., "WO-042")

Trinity Decompose

EUS Agent Capabilities

Integration with Trinity Workflow

Scale-Based Task Decomposition

Usage

Conventional Commits Quick Reference

Format

Types

Examples

Trinity Best Practices

Maintain Trinity Decompose?

EUS Agent Capabilities

Integration with Trinity Workflow

Scale-Based Task Decomposition

Usage

Conventional Commits Quick Reference

Format

Types

Examples

Trinity Best Practices

Maintain Trinity Decompose?

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