Modifiers do not work with static classes

[simjnd]

What version of Tailwind CSS are you using?

v4.1.7

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

Vite 6.3.5

What version of Node.js are you using?

Bun 1.2.5

What browser are you using?

Chrome

What operating system are you using?

macOS

Reproduction URL

https://play.tailwindcss.com/y1AvMNFDTB?file=css

Describe your issue

If I declare my own static classes (not Tailwind utilities), they do not work with modifiers. I cannot conditionally apply them with a Tailwind CSS modifier such as hover: data-<attribute>:, etc.

[wongjn]

You'd need to define the class name rule via @utility: https://play.tailwindcss.com/dZr2prHxAm?file=css

[simjnd]

Thank you! It feels unintuitive that these modifiers only work with utilities and not any class declared in my app.css (although after reading the docs again it is mentioned in the first paragraph, duh)