fcd-design

Trigger: /fcd-design [problem description, feature name, file path, or GitHub issue number]

A full PRD-class design skill that walks a problem through five stages: Discovery → Domains → Surfaces → Architecture → Phases. The key ECD inversion: surfaces (ports) are co-designed before any internal architecture is committed to. Architecture is the consequence of frozen surfaces, not a prerequisite for them.

When to use

Use fcd-design when you need a real PRD — multi-domain work, non-trivial integration with existing systems, decisions a team will need to align on. It supersedes the older forge-design and design-prd skills.

For light-weight specs, use fcd-card instead. To take a finished PRD and decompose it into implementable commissions, follow fcd-design with fcd-plan.

What you get

A complete PRD document with the five stages each filled in. The Domains stage names every component the work touches. The Surfaces stage co-designs every shared port. The Architecture stage is constrained by those frozen surfaces — it cannot bypass them or invent new ones implicitly. The Phases stage breaks delivery into commission-sized slices ordered so Wave 0 (surfaces) is always first.

Canon reference: ECD — FCA Synthesis and FCA — Layers and Domains.