Vertical Slice Planning Skill

This skill guides the decomposition of features into vertical slices - thin, end-to-end pieces of functionality that can be shipped independently.

When to Use

Apply this skill when:

• Breaking down a feature into Subtasks
• Deciding implementation order for a feature
• Planning PR structure for a feature
• Users ask "how should we break this down?"
• Discussing what to build first
• Reviewing feature decomposition plans

What is a Vertical Slice?

A vertical slice cuts through ALL layers of the application to deliver a thin piece of complete functionality.

┌─────────────────────────────────────────┐
│              HORIZONTAL LAYERS           │
├─────────────────────────────────────────┤
│  UI Layer      │ █ │     │     │        │
├────────────────┼───┼─────┼─────┼────────┤
│  API Layer     │ █ │     │     │        │
├────────────────┼───┼─────┼─────┼────────┤
│  Service Layer │ █ │     │     │        │
├────────────────┼───┼─────┼─────┼────────┤
│  Data Layer    │ █ │     │     │        │
└────────────────┴───┴─────┴─────┴────────┘
                  ↑
            Vertical Slice
         (Complete feature)

Vertical vs Horizontal

Horizontal Approach (Avoid)

Building all of one layer before moving to the next.

Problems: Nothing works until everything is done, late integration issues.

Vertical Approach (Prefer)

Building thin, complete features:

1. User can view empty product list (UI → API → DB)
2. User can add a product (UI → API → DB)
3. User can edit a product (UI → API → DB)

Benefits: Each slice is shippable, visible progress, early feedback.

Naming Convention for Jira Subtasks

Since Jira Subtasks are flat (no nesting), use prefixes:

SLICE 1: Basic product list display
SLICE 1.1: Add product image support
SLICE 2: Product search functionality
REFACTOR: Extract shared product utils
TEST: Integration tests for product API

Slice Sizing Guidelines

Integration with Jira Workflow

When creating Jira Stories:

• Parent Story = Full feature context
• Subtasks = Vertical slices (potential PRs)

Each Subtask should be independently deployable, testable, and valuable.

Remember: Ship working software frequently. Slices make this possible.