[v4] Tailwind CSS 4 ignores .vitepress directory and files

[Vectrex]

What version of Tailwind CSS are you using?

4.0.1

What build tool (or framework if it abstracts the build tool) are you using?

vite

What version of Node.js are you using?

22.13.1

What browser are you using?

Firefox

What operating system are you using?

Ubuntu 24.04.1

Describe your issue

With Tailwind 3.4.x I can incorporate Tailwind classes in my Vitepress markdown files. My tailwind.config.js looks like this

export default {
    content: [
        './src/**/*.{vue,js,html}',
        './docs/**/*.md',
        './index.html'
    ],
    theme: { ... }

One of the markdown files contains a

<div class="bg-amber-900">

and Vite delivers a stylesheet containing

.bg-amber-900 {
  --tw-bg-opacity: 1;
  background-color: rgb(120 53 15 / var(--tw-bg-opacity, 1));
}

When switching to Tailwind 4 the config file is gone.
Since the .vitepress directory and all its contents is not in a .gitignore all the markdown files should be parsed.

The CSS now looks like this

@import 'tailwindcss';
@theme { ... }

but the resulting CSS provided by Vite does not contain a .bg-amber-900 class.

Adding

@source './docs/**/*.md';

doesn't change anything - the resulting CSS provided by Vite does not contain a .bg-amber-900 class.

package.json

"dependencies": {
    "tailwindcss": "^4.0.1",
    "vite": "^6.0.11",
    "@tailwindcss/vite": "^4.0.1",
    "vitepress": "^1.6.3"
    ...
  },

vite.config.js

import { defineConfig } from 'vite'
import tailwindcss from '@tailwindcss/vite'

export default defineConfig({
 ...
  plugins: [
      tailwindcss(),
  ],
})

Expected behavior:

Tailwind 4.0 should also generate stylesheets containing classes used in Vitepress markdown files.

[RobinMalfait]

Hey!

Can you add a minimal reproduction GitHub repo so we can take a look?

[Vectrex]

Maybe it already helps to link the "real thing".

https://github.com/Vectrex/vxVue

The outcome can be seen here

https://vectrex.github.io/vxVue/accordion.html

where for example the GUI elements are not styled.
Checking out tag 1.1.x provides the Tailwind 3.x setup.