Radix UI

This is the accessibility layer, not the design layer — reach for Primitives when you are building a bespoke design system and want correct dialog focus traps, roving tabindex and collision-aware popovers without writing them. In practice you rarely install it directly: `npx shadcn@latest add dialog` already vendors Radix into the project, so check for `components/ui/` before adding a second copy. Use the single `radix-ui` package rather than the old per-component `@radix-ui/react-*` packages for new work, keep Radix Colors in mind as a ready-made 12-step token set, and note there is no llms.txt so the docs must be fetched page by page.

Why it is here. Radix set the modern standard for headless, accessible React components, and shadcn/ui made it the de facto foundation of the entire copy-paste component ecosystem. Almost everything else in this index sits on top of it.