Impeccable

Impeccable is a design skill and plugin for coding agents that gives them a shared design vocabulary, so they can build new interfaces, improve existing ones and keep to a project's design system. It works from a PRODUCT.md describing your audience and goals, offers focused passes such as typeset, and can run automatic checks that catch common AI design mistakes while the agent works. Anyone shipping AI-built UI can install it in Claude Code, and it comes built into the GitHub Copilot app.