Tailwind didn't scan my UI package

I set up a pnpm monorepo with a shared UI package of shadcn-style components, used by two apps. I had copied the components from a standalone design system where they looked right. In the apps, the padding and layout were broken, and there was no error.

The classes that only the package used, like px-6, py-6, rounded-xl, and gap-6, weren’t in the CSS output. Tailwind v4 finds classes by scanning your files, but it skips node_modules and anything git ignores, and a workspace package is linked into node_modules. So Tailwind never saw the components.

@source adds a path to scan. I added one to each app’s CSS, along with a few other changes, and the components were still broken. The path was one directory short. It pointed at apps/packages/ui, which doesn’t exist. Tailwind resolves @source relative to the CSS file it’s in, which was apps/web/src/styles.css, and a path that doesn’t exist fails silently. Going up one more level fixed it:

@import "@repo/ui/styles.css";
@source "../../../packages/ui";

The components rendered correctly after that. If you have many apps, you can also put the @source in the UI package’s own styles.css, pointing at its components, so each app doesn’t need a relative path into the repo.