design-first

Kick off the Data-First Engineering Protocol for any non-trivial task. Classifies the task, invokes the data-architect to produce a concept contract at .claude/concepts/, resolves Open Questions with the user, and hands off to implementer agents with the contract as their authoritative input. Use when: user says /design-first, 'design this feature', 'start a new feature', or is about to request any non-trivial implementation. The concept-gate.py hook will block Edit/Write without an approved contract, so this skill is the entry point.