diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6c3837abf85c..5428fa88f59f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Find utilities when using the Angular class shorthand syntax ([#15974](https://github.com/tailwindlabs/tailwindcss/pull/15974))
- Find utilities when using functions inside arrays ([#15974](https://github.com/tailwindlabs/tailwindcss/pull/15974))
- Ensure that `@tailwindcss/browser` does not pollute the global namespace ([#15978](https://github.com/tailwindlabs/tailwindcss/pull/15978))
+- Ensure that `tailwind-merge` is not scanned when using the Vite plugin ([#16005](https://github.com/tailwindlabs/tailwindcss/pull/16005))
- Ensure CSS theme variables are available within shadow roots ([#15975](https://github.com/tailwindlabs/tailwindcss/pull/15975))
- Fix crash when project lives in the `/` directory ([#15988](https://github.com/tailwindlabs/tailwindcss/pull/15988))
- Ensure `@custom-variant` has a non-empty selector list ([#16009](https://github.com/tailwindlabs/tailwindcss/pull/16009))
diff --git a/integrations/vite/ignored-packages.test.ts b/integrations/vite/ignored-packages.test.ts
new file mode 100644
index 000000000000..f7f85ff14975
--- /dev/null
+++ b/integrations/vite/ignored-packages.test.ts
@@ -0,0 +1,81 @@
+import { candidate, css, fetchStyles, html, js, retryAssertion, test, ts, txt } from '../utils'
+
+const WORKSPACE = {
+ fs: {
+ 'package.json': txt`
+ {
+ "type": "module",
+ "dependencies": {
+ "tailwind-merge": "^2",
+ "@tailwindcss/vite": "workspace:^",
+ "tailwindcss": "workspace:^"
+ },
+ "devDependencies": {
+ "vite": "^6"
+ }
+ }
+ `,
+ 'vite.config.ts': ts`
+ import tailwindcss from '@tailwindcss/vite'
+ import { defineConfig } from 'vite'
+
+ export default defineConfig({
+ build: { cssMinify: false },
+ plugins: [tailwindcss()],
+ })
+ `,
+ 'index.html': html`
+
+
+
+
+ `,
+ 'src/index.js': js`
+ import { twMerge } from 'tailwind-merge'
+
+ twMerge('underline')
+
+ console.log('underline')
+ `,
+ 'src/index.css': css`@import 'tailwindcss/utilities' layer(utilities);`,
+ },
+}
+
+test(
+ 'does not scan tailwind-merge in production builds',
+ WORKSPACE,
+ async ({ fs, exec, expect }) => {
+ await exec('pnpm vite build')
+
+ let files = await fs.glob('dist/**/*.css')
+ expect(files).toHaveLength(1)
+ let [, content] = files[0]
+
+ expect(content).toMatchInlineSnapshot(`
+ "@layer utilities {
+ .underline {
+ text-decoration-line: underline;
+ }
+ }
+ "
+ `)
+ },
+)
+
+test('does not scan tailwind-merge in dev builds', WORKSPACE, async ({ spawn, expect }) => {
+ let process = await spawn('pnpm vite dev')
+ await process.onStdout((m) => m.includes('ready in'))
+
+ let url = ''
+ await process.onStdout((m) => {
+ let match = /Local:\s*(http.*)\//.exec(m)
+ if (match) url = match[1]
+ return Boolean(url)
+ })
+
+ await retryAssertion(async () => {
+ let styles = await fetchStyles(url, '/index.html')
+
+ expect(styles).not.toContain(candidate`flex`)
+ })
+})
diff --git a/packages/@tailwindcss-vite/src/index.ts b/packages/@tailwindcss-vite/src/index.ts
index 2fedf73231f2..c8976c0276da 100644
--- a/packages/@tailwindcss-vite/src/index.ts
+++ b/packages/@tailwindcss-vite/src/index.ts
@@ -9,6 +9,8 @@ import type { Plugin, ResolvedConfig, Rollup, Update, ViteDevServer } from 'vite
const DEBUG = env.DEBUG
const SPECIAL_QUERY_RE = /[?&](raw|url)\b/
+const IGNORED_DEPENDENCIES = ['tailwind-merge']
+
export default function tailwindcss(): Plugin[] {
let servers: ViteDevServer[] = []
let config: ResolvedConfig | null = null
@@ -62,6 +64,18 @@ export default function tailwindcss(): Plugin[] {
})
function scanFile(id: string, content: string, extension: string, isSSR: boolean) {
+ for (let dependency of IGNORED_DEPENDENCIES) {
+ // We validated that Vite IDs always use posix style path separators, even on Windows.
+ // In dev build, Vite precompiles dependencies
+ if (id.includes(`.vite/deps/${dependency}.js`)) {
+ return
+ }
+ // In prod builds, use the node_modules path
+ if (id.includes(`/node_modules/${dependency}/`)) {
+ return
+ }
+ }
+
let updated = false
for (let candidate of moduleGraphScanner.scanFiles([{ content, extension }])) {
updated = true