Tailwind Purge Fixer

Found it — the culprit is this line:

@source "../node_modules";

Root cause: In Tailwind v4, @source tells the Oxide engine to scan those files for class names to generate. Pointing it at the entire node_modules directory makes it scan every JS/TS/HTML file in every package you've installed — including packages that have nothing to do with your UI. Any string in any of those files that happens to look like a valid Tailwind utility (text-sm, flex, p-4, etc.) gets generated into your CSS. That's almost certainly your jump from 4KB to 80KB+.

You don't need to scan node_modules at all — shadcn-ui components aren't styled by scanning the library's source; they're

copied into your own project (usually src/components/ui/), so Tailwind already picks them up when it scans your app's source files.

Fix

Remove the broad @source directive entirely:

@import "tailwindcss";

/* Remove this line: */
/* @source "../node_modules"; */

If your @import "tailwindcss"; is at the root of your CSS and your app.css lives inside src/, Tailwind v4's automatic content detection should already pick up everything under your project root (excluding .gitignored paths like node_modules, dist, etc. by default). You likely don't need any manual @source directive at all.

Only add @source back if:

• You have shadcn/ui or other component files living outside the default scan root (e.g., a monorepo package), in which case scope it precisely:

@source "../../packages/ui-components/**/*.{ts,tsx}";

• Never point @source at node_modules as a whole — if you truly need one specific package's compiled output scanned (rare), target the exact subpath, e.g. @source "../node_modules/some-specific-package/dist";.

Verify

npm run build

Check the new CSS file size — it should drop back down near your original ~4KB (plus whatever shadcn-ui components you're actually using). Do a quick visual pass on the pages using shadcn-ui components to confirm nothing broke, since shadcn relies on CSS variables (--background, --primary, etc.) defined in your @theme block — those aren't affected by this fix, just the utility-class bloat.

If size is still high after removing that line, the next place I'd check is whether your @theme block has leftover unused CSS variables from the v3→v4 migration — happy to take a look at that file if you want a second pass.