Tailwind V4 with Shadcn Monorepo

[fluid-design-io]

Since Fumadocs V15 uses Tailwind V4, I have upgraded my monorepo (inited from shadcn monorepo) to use V4 as well.

Wanted to share how I've done it and hope someone finds it helpful ✨

You'll need update these files to make it work:

First, remove both tailwind.config.js in your project and packages/ui folders.
Then do the following:

Main Project

Replace everything on apps/web/app/styles.css:

/* the monorepo's ui package globals.css */
@import "@workspace/ui/globals.css";

@import "fumadocs-ui/css/neutral.css";
@import "fumadocs-ui/css/preset.css";

/* relative to the CSS file, make sure it's correct for your app */
@source "../node_modules/fumadocs-ui/dist/**/*.js";
@source "../../../packages/ui/src/components/**/*.tsx";

UI Package

packages/ui/package.json:

remove autoprefixer package.

packages/ui/postcss.config.mjs:

export default {
  plugins: ["@tailwindcss/postcss"],
};

packages/ui/src/styles/globals.css:

source from shadcn's repo

@import "tailwindcss";

@plugin 'tailwindcss-animate';

@custom-variant dark (&:is(.dark *));

@theme {
  --font-sans: var(--font-sans);
  --font-sans--font-feature-settings: "cv11";

  --font-mono: var(--font-mono);
  --font-kaisei: var(--font-kaisei);

  --color-background: hsl(var(--background));
  --color-foreground: hsl(var(--foreground));

  --color-card: hsl(var(--card));
  --color-card-foreground: hsl(var(--card-foreground));

  --color-popover: hsl(var(--popover));
  --color-popover-foreground: hsl(var(--popover-foreground));

  --color-primary: hsl(var(--primary));
  --color-primary-foreground: hsl(var(--primary-foreground));

  --color-secondary: hsl(var(--secondary));
  --color-secondary-foreground: hsl(var(--secondary-foreground));

  --color-muted: hsl(var(--muted));
  --color-muted-foreground: hsl(var(--muted-foreground));

  --color-accent: hsl(var(--accent));
  --color-accent-foreground: hsl(var(--accent-foreground));

  --color-destructive: hsl(var(--destructive));
  --color-destructive-foreground: hsl(var(--destructive-foreground));

  --color-border: hsl(var(--border));
  --color-input: hsl(var(--input));
  --color-ring: hsl(var(--ring));

  --color-chart-1: hsl(var(--chart-1));
  --color-chart-2: hsl(var(--chart-2));
  --color-chart-3: hsl(var(--chart-3));
  --color-chart-4: hsl(var(--chart-4));
  --color-chart-5: hsl(var(--chart-5));

  --color-sidebar: hsl(var(--sidebar-background));
  --color-sidebar-foreground: hsl(var(--sidebar-foreground));
  --color-sidebar-primary: hsl(var(--sidebar-primary));
  --color-sidebar-primary-foreground: hsl(var(--sidebar-primary-foreground));
  --color-sidebar-accent: hsl(var(--sidebar-accent));
  --color-sidebar-accent-foreground: hsl(var(--sidebar-accent-foreground));
  --color-sidebar-border: hsl(var(--sidebar-border));
  --color-sidebar-ring: hsl(var(--sidebar-ring));

  --radius-lg: var(--radius);
  --radius-md: calc(var(--radius) - 2px);
  --radius-sm: calc(var(--radius) - 4px);
}

/*
  The default border color has changed to `currentColor` in Tailwind CSS v4,
  so we've added these compatibility styles to make sure everything still
  looks the same as it did with Tailwind CSS v3.

  If we ever want to remove these styles, we need to add an explicit border
  color utility to any element that depends on these defaults.
*/
@layer base {
  *,
  ::after,
  ::before,
  ::backdrop,
  ::file-selector-button {
    border-color: var(--color-border, currentColor);
  }
  body {
    @apply bg-background text-foreground;
  }
}

@layer base {
  :root {
    --background: 0 0% 100%;
    --foreground: 240 10% 3.9%;
    --card: 0 0% 100%;
    --card-foreground: 240 10% 3.9%;
    --popover: 0 0% 100%;
    --popover-foreground: 240 10% 3.9%;
    --primary: 240 5.9% 10%;
    --primary-foreground: 0 0% 98%;
    --secondary: 240 4.8% 95.9%;
    --secondary-foreground: 240 5.9% 10%;
    --muted: 240 4.8% 95.9%;
    --muted-foreground: 240 3.8% 46.1%;
    --accent: 240 4.8% 95.9%;
    --accent-foreground: 240 5.9% 10%;
    --destructive: 0 84.2% 60.2%;
    --destructive-foreground: 0 0% 98%;
    --border: 240 5.9% 90%;
    --input: 240 5.9% 90%;
    --ring: 240 10% 3.9%;
    --chart-1: 12 76% 61%;
    --chart-2: 173 58% 39%;
    --chart-3: 197 37% 24%;
    --chart-4: 43 74% 66%;
    --chart-5: 27 87% 67%;
    --radius: 0.5rem;
  }
  .dark {
    --background: 240 10% 3.9%;
    --foreground: 0 0% 98%;
    --card: 240 10% 3.9%;
    --card-foreground: 0 0% 98%;
    --popover: 240 10% 3.9%;
    --popover-foreground: 0 0% 98%;
    --primary: 0 0% 98%;
    --primary-foreground: 240 5.9% 10%;
    --secondary: 240 3.7% 15.9%;
    --secondary-foreground: 0 0% 98%;
    --muted: 240 3.7% 15.9%;
    --muted-foreground: 240 5% 64.9%;
    --accent: 240 3.7% 15.9%;
    --accent-foreground: 0 0% 98%;
    --destructive: 0 62.8% 30.6%;
    --destructive-foreground: 0 0% 98%;
    --border: 240 3.7% 15.9%;
    --input: 240 3.7% 15.9%;
    --ring: 240 4.9% 83.9%;
    --chart-1: 220 70% 50%;
    --chart-2: 160 60% 45%;
    --chart-3: 30 80% 55%;
    --chart-4: 280 65% 60%;
    --chart-5: 340 75% 55%;
  }
}