What version of Tailwind CSS are you using?

v4.3.0

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

postcss 8.5.8

What version of Node.js are you using?

v26.1.0

What browser are you using?

Chrome

What operating system are you using?

Arch Linux

Reproduction URL

https://play.tailwindcss.com/hmGRLYCbyv

Describe your issue

There's an issue with parsing custom drop shadows of the form --drop-shadow-broken: 0 0 calc(1 * var(--spacing)) black;, where the calc(...) value is interpreted as the color, and the generated CSS is broken. it works fine without a color specified, but as soon as you do specify it, it overwrites the calc(...) with the color variable and the shadow breaks.