CSS syntax issue with unexpected ")" during Vite build in Tailwind CSS v4 project

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1

I recently faced a challenge while building my project. It was functioning smoothly until a couple of days ago, but now I’m encountering a peculiar CSS syntax error when I try to execute the build command.

npm run build

> build  
> vite build

vite v6.2.5 building for production...
✓ 2 modules transformed.
Generated an empty chunk: "app".
rendering chunks (1)...warnings when minifying css:
▲ [WARNING] Unexpected ")" [css-syntax-error]

    <stdin>:7:153265:
      7 │ ...or:var(--color-zinc-100)}:where(){width:calc(var(--spacing)*5);h...
        ╵                                    ^

public/build/manifest.json              0.27 kB │ gzip:  0.14 kB
public/build/assets/app--Cil65mr.css  190.86 kB │ gzip: 26.36 kB  
public/build/assets/app-l0sNRNKZ.js     0.00 kB │ gzip:  0.02 kB
✓ built in 607ms

The error appears to stem from CSS minification, indicating an unexpected closing parenthesis. Interestingly, this warning does not occur when I create a brand-new project.

Here’s my current package.json details:

{
    "private": true,
    "type": "module", 
    "scripts": {
        "build": "vite build",
        "dev": "vite dev",
        "watch": "vite build --watch"
    },
    "dependencies": {
        "@tailwindcss/vite": "^4.1.1",
        "autoprefixer": "^10.4.21",
        "axios": "^1.8.4",
        "concurrently": "^9.1.2", 
        "laravel-vite-plugin": "^1.2.0",
        "tailwindcss": "^4.1.1",
        "vite": "^6.2.5"
    },
    "optionalDependencies": {
        "@rollup/rollup-linux-x64-gnu": "4.39.0",
        "@tailwindcss/oxide-linux-x64-gnu": "^4.1.1",
        "lightningcss-linux-x64-gnu": "^1.29.3"
    }
}

The issue began after updating my dependencies. Has anyone else experienced this problem and found a resolution?

2

check your tailwind config - probably some invalid css in there. i got the same weird parenthesis errors mixing v3 and v4 syntax. also try deleting the .vite cache folder, that sometimes fixes minification issues after updates.

3

Had the same issue upgrading to Tailwind v4. Usually it’s malformed CSS custom properties or utility classes that don’t exist anymore. Check any custom CSS using calc() with CSS variables - the syntax changed in v4. Also clear node_modules and reinstall since the oxide engine dependencies sometimes conflict with cached builds. Run npm ci instead of regular install for clean dependency resolution. That empty chunk warning means you’ve got unused imports which can mess with minification too.

4

This looks like a CSS variable parsing issue with the lightningcss minifier. I’ve hit something similar when the minifier couldn’t handle certain CSS custom properties in Tailwind v4. Check if you’ve got any :where() selectors with empty parentheses in your custom CSS or components. The error shows :where(){} which might be getting generated wrong. You could try downgrading lightningcss temporarily to see if that fixes it, or switch to a different CSS minifier like cssnano. Also check if you have any CSS files with malformed variable declarations that worked before but are now stricter in v4.

5

sounds like a lightningcss issue with the tailwind v4 upgrade. maybe try adding css: { minify: false } in your vite config for now, it might fix it. i had some weird stuff after upgrading too, minifier can be picky with css sometimes.

6

That CSS variable parsing in the error trace looks sketchy - especially the calc() function in your custom properties. I hit similar minification warnings when upgrading to Tailwind v4. The new oxide engine generates different CSS variable syntax that breaks certain minifiers. In my case, conflicting PostCSS plugins were processing the same CSS variables twice. Since you’re running both autoprefixer and Tailwind v4’s built-in processing, you might have duplicate transformations happening. Try ditching autoprefixer temporarily - Tailwind v4 handles vendor prefixes internally now. Also check your vite.config.js for any CSS preprocessing that might clash with the @tailwindcss/vite plugin. That empty chunk warning points to a module resolution issue too.

7

Build pipeline issues like this are exactly why I ditched manual dependency management years ago.

That error? Classic CSS minification conflict between Tailwind v4’s oxide engine and lightningcss. These tools fight over CSS parsing and you get weird syntax errors like that orphaned closing parenthesis.

I don’t bother debugging which CSS property breaks or testing different minifier configs. I just automate all my build processes. When dependencies clash or builds fail, the automated system catches it, logs exactly what broke, and can roll back to working versions automatically.

My workflows monitor everything - dependency updates, CSS processing, deployment. Something breaks during build like your CSS minification issue? Gets flagged immediately with full context about what changed.

For your case, set up an automated workflow that runs your build, catches CSS syntax errors, and automatically tries different minifier settings or dependency versions until it finds something that works. No more manual troubleshooting.

Automation handles dependency conflicts way better than manually figuring out which package versions play nice.