standalone CLI Cannot apply unknown utility class `*-taupe-*`

[nam-co]

MacOS
node -v: v21.7.3
Tailwind v4.2
Tailwind installed via homebrew
Notes: I already upgraded, restarted, etc.. it only happens with the new colors (taupe,...)

Command:
tailwindcss -i ./resources/css/backend.css -o ./public/assets/css/backend.css --watch
≈ tailwindcss v4.2.0
Done in 288ms
Error: Cannot apply unknown utility class bg-taupe-500

CSS Class in external file external-classes.css

@utility color-taupe {
	@apply bg-taupe-500 text-white;
}

Main CSS file

@import "tailwindcss";
@import "../css/external-classes.css";

[RobinMalfait]

Hey! Can you provide a minimal reproduction repository by any chance? There might be something in your setup that we're missing.

Also are you sure that you are using Tailwind CSS is at version 4.2.0? If you just run tailwindcss without any arguments, what output do you see?

I would expect that it shows the v4.2.0 version:

But when I install from Homebrew, it installs v4.1.8 for me:

Therefore running the tailwindcss command shows v4.1.8:

Warning

Also note that the Homebrew version is not something we officially support, and is setup by 3rd parties. I would recommend to get the official binaries from the releases on GitHub: https://github.com/tailwindlabs/tailwindcss/releases/tag/v4.2.0

Once you have the correct binary it should work as expected:

[nam-co]

@RobinMalfait if you think it could help, I can reinstall tailwind, here is the result of just tailwindcss
≈ tailwindcss v4.2.0
Usage:
tailwindcss [--input input.css] [--output output.css] [--watch] [options…]
Options:
....

Here is the homebrew info (I use Cakebrew, just an UI for homebrew)
==> tailwindcss: stable 4.2.0 (bottled), HEAD
Utility-first CSS framework
https://tailwindcss.com
Installed
/opt/homebrew/Cellar/tailwindcss/4.2.0 (555 files, 17.4MB) *
Poured from bottle using the formulae.brew.sh API on 2026-02-18 at 16:41:10
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/t/tailwindcss.rb
License: MIT
==> Dependencies
Required: node

[RobinMalfait]

I was able to install the latest 4.2.0 version of Tailwind CSS via brew. But given your initial setup it works as expected:

Can you create a minimal reproduction repo, put it on GitHub and share it here so I can clone it? Pretty sure it's going to be related to your setup somehow, just need the setup to debug what's going on.

[nam-co]

Thanks Robin, I will work on the small repo, but it must be me, I deleted/reinstalled tailwind but same result
I will try to figure out whats happening and post here if I find something, because not event class="bg-taupe-500" is working

[nam-co]

@RobinMalfait I did npm install tailwindcss @tailwindcss/cli
and then the homebrew standalone started working
macbookpro@macbookpro laravelV12 % /opt/homebrew/bin/tailwindcss -i ./resources/css/backend.css -o ./public/assets/css/backend.css
≈ tailwindcss v4.2.0

Done in 323ms
Strange

[RobinMalfait]

Hmm interesting. Going to close this for now since it seems to be working. But if you run into an issue again and can setup a minimal reproduction repo then we can figure out what's going on!