Tailwind server hangs when config includes border radius default

[alvinleung1996]

What version of VS Code are you using?

v1.104.1

What version of Tailwind CSS IntelliSense are you using?

v0.14.26

What version of Tailwind CSS are you using?

v4.1.13

What package manager are you using?

npm

What operating system are you using?

macOS 15.6.1 (24G90)

Tailwind CSS Stylesheet (v4) or config file (v3)

@import 'tailwindcss';
@config './tailwind.config.cjs';

tailwind.config.cjs:

/** @type {import('tailwindcss').Config} */
module.exports = {
    theme: {
        extend: {
            borderRadius: {
                DEFAULT: 'calc(var(--radius))',
            },
        },
    },
};

VS Code settings

{
}

I test with a new empty VSCode profile.

Reproduction URL

https://github.com/alvinleung1996/tailwind-server-hang-example

Describe your issue

When theme.extend.borderRadius.DEFAULT is set to calc(var(--radius)), hovering rounded will hang the server forever. The hover popup shows "Loading..." and VSCode process explorer shows tailwindServer.js running 100% of the CPU.

It seems the server hangs whenever var(--radius) is inside an calc() expression, e.g. calc(var(--radius) * 2), calc(var(--radius) + 20px).

The server works fine when setting theme.extend.borderRadius.DEFAULT to var(--radius), calc(var(--foo)) and calc(20px).

[thecrypticace]

Haven't verified but this feels like a recursive theme lookup loop.

[thecrypticace]

It's actually a loop in the variable replacement logic b/c of the wrapping calc(…). Fixing this properly is going to need a real parser + directed graph to handle and bail on replacements appropriately.

Basically emulating how the browser does these replacements (and how it decides when to bail). Gonna need to dust off #1330 and continue work on that PR.