software-design - design before code, then build strategically

Use this skill when a request introduces new behavior into an existing codebase. The job is to keep the interface simple, hide complexity in the right module, and then build the approved design as a thin working slice before widening.

This is the canonical feature skill for existing codebases. It already includes the Pragmatic Programmer build discipline, so do not stack pragmatic on the same existing-codebase feature request.

Phase 4's build rules intentionally duplicate the pragmatic skill — skills install standalone, so the shared discipline must live in both files. If you change a rule here, mirror it there.

When to use

Use for new capabilities: features, endpoints, modules, data flows, routes, actions, components, hooks, integrations, or systems.

Do not use for:

• greenfield, prototype, or standalone feature work with no existing architecture to inspect; use pragmatic
• pure visual/product critique of an existing experience; use product-design
• post-change fit-and-finish; use clean-up
• typo fixes, one-line changes, or purely cosmetic edits