slice

Bridge the spec's user-language description to the codebase's module structure. The napkin sketch says "something renders the editor" — your job is to say "the <WriteScreen> component at apps/web/src/features/write/WriteScreen.tsx renders it."

A vertical slice is the full stack a feature touches — UI, API, domain, data, external. TDD without a slice plan drifts to the easiest starting point (usually a backend unit) and quietly drops the UI.

Read the spec

Load the spec and any Technology Decisions from /spike. Summarise back: the headline interaction, the supporting jobs, and the tech choices.

Explore the codebase

Build a mental model of what already exists — real exploration, not guessing. For each supporting job, look for:

• Existing modules that match the responsibility
• Codebase conventions — monorepo layout, feature folders, layering patterns, how new features are typically added
• Frontend layer — framework, feature folder pattern, how screens handle state and API calls
• Data layer — where entities live, persistence approach

Use the Explore subagent or Grep/Glob directly. Be specific about files you looked at and patterns you found. The user knows things about the codebase you can't read from files — present findings and invite correction.