Design Atlas
Type
component registry
Verdict
Useful
Licence
Ship licence, open source permissiveopen-source-permissivefree and open source under MIT (repo shadcn-labs/shadcn-cssinjs); no paid tier
Agent channels
llms-txt, registry, skill
Pricing
free
Reviewed

← Atlas · Topics: components, agents-and-prompts

shadcn-cssinjs ​

Type
component registry
Verdict
Useful
Licence
Ship licence, open source permissiveopen-source-permissivefree and open source under MIT (repo shadcn-labs/shadcn-cssinjs); no paid tier
Agent channels
llms-txt, registry, skill
Pricing
free
Reviewed

What it is ​

A shadcn-style registry that restyles the shadcn/ui component set with StyleX, Meta's compile-time CSS-in-JS library, instead of Tailwind utility classes, and builds it on Base UI primitives. It comes from Shadcn Labs (repo started June 2026 by Aniket Pawar, about 120 stars at review). The June 2026 changelog claims full parity with shadcn/ui; the registry index held 54 UI items plus two helper files at review, from accordion and alert dialog to sidebar, data table, chart, calendar and carousel. Every component uses logical CSS properties, so right-to-left layouts are supported.

When to open it ​

When your team prefers typed, colocated styles that compile to atomic CSS but still wants the shadcn/ui API and look. Also useful if you already have a shadcn theme: the components read the same --background, --primary and related variables, so they can sit next to stock shadcn components.

Most useful ​

  • A one-for-one StyleX version of each shadcn/ui component, including the heavier ones (calendar, chart, carousel, resizable, sonner)
  • A token file that maps shadcn's CSS variables into typed StyleX tokens, with dark mode still driven by a .dark class
  • RTL previews on each component page
  • A theme customiser on the site

Using it with agents ​

Well set up. /llms.txt links a Markdown mirror of every page, any URL returns Markdown when you append .md or send Accept: text/markdown, and /llms-full.txt holds the whole docs. An agent skill lives at /.well-known/agent-skills/site-skill.md. Components install with the shadcn CLI by URL or through an @shadcn-cssinjs namespace in components.json, which the shadcn MCP server can then browse.

Watch out for ​

  • Setup is heavier than stock shadcn: StyleX needs a Babel plugin and a PostCSS plugin, and adding .babelrc takes Next.js off Turbopack
  • The MCP page writes the registry URL without www, which redirects; use the www host if the CLI complains
  • A young project from one maintainer; parity with upstream shadcn/ui depends on it keeping pace

Reusable ideas ​

  • Keep the upstream CSS variable names so a port can share a theme with the original
  • Serve every docs page as Markdown by suffix and by Accept header, not only through llms.txt
  • Publish a site skill at a well-known path so agents can find it without a separate install

Shadcn Labs, shadcn/ui, Base UI, coss ui, startercn, shadercn