vertical-slicing

name	vertical-slicing
type	workflow
description	Guidelines and procedures for planning and implementing end-to-end functional slices for fullstack features.
user-invocable	true
allowed-tools	Read, Glob, Grep, Write
effort	3
argument-hint	[feature, epic, or PRD name]

Skill: /vertical-slice

Use this skill when planning complex fullstack features to ensure delivery by user-value units rather than technical layers.

The Vertical Slicing Workflow

1. Identify the Smallest Value Unit

• Decompose the PRD into slices that represent a functional path.
• Example: Instead of "Authentication System," start with "Login with Email and Password".

2. Define the Contract

• Before implementing, the lead-programmer or backend-developer must define the API contract.
• Document this in a Design Doc or temporary spec.

3. Plan the Slice Tasks

Organize each phase to contain:

• Database/Data Model: Schema changes required for this slice.
• Backend Implementation: Logic and API endpoints.
• Frontend Integration: UI components and API consumption.
• E2E Verification: Test verifying the whole path.

4. Implementation Rules

• Always prioritize the "Deepest" part of the slice first (Database) and move "Upwards" (UI).
• Do not move to the next slice until the current one is "Integration Complete".
• If a horizontal change is absolutely necessary (e.g., shared middleware), implement it as a prerequisite phase 0.

Benefits for Agents

• Context Management: Focusing on a slice keeps the context window filled with relevant code for that specific path.
• Early Feedback: The user can verify functional pieces earlier.
• Reduced Integration Risk: Cross-layer issues are caught within the slice implementation.