feat(nextjs): export Mosaic UserButton from an experimental subpath

.changeset/mosaic-experimental-export.md

@@ -0,0 +1,21 @@
+---
+'@clerk/nextjs': minor
+'@clerk/react': minor
+'@clerk/ui': minor
+---
+
+Add an experimental subpath for Mosaic components that mount directly in your app's tree rather than being rendered by clerk-js. `UserButton` is the first one. It reads Clerk through hooks, so a `ClerkProvider` above it is all it needs:
+
+```tsx
+import { UserButton } from '@clerk/nextjs/experimental/mosaic';
+```
+
+Pair it with the stylesheet, which carries the design tokens and every component rule:
+
+```css
+@import '@clerk/nextjs/experimental/mosaic/styles.css' layer(clerk);
+```
+
+The surface and the components behind it will change without a major version while they are experimental.
+
+In `@clerk/ui`, the Mosaic stylesheet moves from `@clerk/ui/styles.css` to `@clerk/ui/experimental/mosaic/styles.css` to sit alongside the components it styles. Update the import if you were using it.

.changeset/mosaic-user-button-custom-pages.md

@@ -0,0 +1,2 @@
+---
+---

.claude/skills/mosaic/references/stylex.md

@@ -621,8 +621,8 @@ export interface PopoverPopupProps extends MosaicComponentProps<'div'> { … }
 
 - **Published** (`build:mosaic` → `@stylexjs/rollup-plugin`): compiles the
   `styles/index.ts` barrel into `dist-mosaic/styles.css`, exported as
-  `@clerk/ui/styles.css`. Consumers choose the cascade layer at import:
-  `@import '@clerk/ui/styles.css' layer(components)`.
+  `@clerk/ui/experimental/mosaic/styles.css`. Consumers choose the cascade layer at import:
+  `@import '@clerk/ui/experimental/mosaic/styles.css' layer(components)`.
 - **Swingset** (source-consumed): `@stylexjs/unplugin/webpack` in `next.config`
   transforms StyleX **JS only** (calls → static atoms; SWC/Emotion untouched);
   `@stylexjs/postcss-plugin` extracts the **CSS** by replacing `@stylex;` in

packages/nextjs/package.json

@@ -55,6 +55,12 @@
       "import": "./dist/esm/experimental.js",
       "require": "./dist/cjs/experimental.js"
     },
+    "./experimental/mosaic": {
+      "types": "./dist/types/experimental/mosaic.d.ts",
+      "import": "./dist/esm/experimental/mosaic.js",
+      "require": "./dist/cjs/experimental/mosaic.js"
+    },
+    "./experimental/mosaic/styles.css": "./dist/experimental/mosaic/styles.css",
     "./legacy": {
       "types": "./dist/types/legacy.d.ts",
       "import": "./dist/esm/legacy.js",
@@ -70,15 +76,15 @@
     "webhooks"
   ],
   "scripts": {
-    "build": "pnpm clean && tsup",
+    "build": "pnpm clean && tsup && node ../../scripts/copy-mosaic-styles.mjs dist/experimental/mosaic/styles.css",
     "build:declarations": "tsc -p tsconfig.declarations.json",
     "clean": "rimraf ./dist",
     "dev": "tsup --watch",
     "dev:pub": "pnpm dev -- --env.publish",
     "format": "node ../../scripts/format-package.mjs",
     "format:check": "node ../../scripts/format-package.mjs --check",
     "lint": "eslint src",
-    "lint:attw": "attw --pack . --profile node16 --ignore-rules unexpected-module-syntax",
+    "lint:attw": "attw --pack . --exclude-entrypoints experimental/mosaic/styles.css --profile node16 --ignore-rules unexpected-module-syntax",
     "lint:publint": "publint",
     "test": "vitest run",
     "test:watch": "vitest watch"
@@ -91,6 +97,7 @@
     "tslib": "catalog:repo"
   },
   "devDependencies": {
+    "@clerk/ui": "workspace:*",
     "crypto-es": "^2.1.0",
     "next": "15.5.19"
   },

packages/nextjs/src/experimental/mosaic.ts

@@ -0,0 +1,16 @@
+'use client';
+
+/**
+ * Mosaic components mounted directly in the host app's tree, rather than through clerk-js. They
+ * read Clerk via hooks, so a `ClerkProvider` above them is all they need.
+ *
+ * Pair with the stylesheet, which carries the design tokens and every component rule:
+ *
+ * ```css
+ * @import '@clerk/nextjs/experimental/mosaic/styles.css' layer(clerk);
+ * ```
+ *
+ * @experimental The surface and the components behind it are subject to change.
+ */
+export { UserButton } from '@clerk/react/experimental/mosaic';
+export type { UserButtonProps } from '@clerk/react/experimental/mosaic';

packages/react/package.json

@@ -63,6 +63,17 @@
         "default": "./dist/experimental.cjs"
       }
     },
+    "./experimental/mosaic": {
+      "import": {
+        "types": "./dist/experimental/mosaic.d.mts",
+        "default": "./dist/experimental/mosaic.mjs"
+      },
+      "require": {
+        "types": "./dist/experimental/mosaic.d.cts",
+        "default": "./dist/experimental/mosaic.cjs"
+      }
+    },
+    "./experimental/mosaic/styles.css": "./dist/experimental/mosaic/styles.css",
     "./legacy": {
       "import": {
         "types": "./dist/legacy.d.mts",
@@ -88,14 +99,14 @@
     "dist"
   ],
   "scripts": {
-    "build": "tsdown",
+    "build": "tsdown && node ../../scripts/copy-mosaic-styles.mjs dist/experimental/mosaic/styles.css",
     "clean": "rimraf ./dist",
     "dev": "tsdown --watch",
     "dev:pub": "pnpm dev --env.publish",
     "format": "node ../../scripts/format-package.mjs",
     "format:check": "node ../../scripts/format-package.mjs --check",
     "lint": "eslint src",
-    "lint:attw": "attw --pack . --profile node16",
+    "lint:attw": "attw --pack . --exclude-entrypoints experimental/mosaic/styles.css --profile node16",
     "lint:publint": "publint",
     "test": "vitest run",
     "test:watch": "vitest watch"

packages/react/src/experimental/mosaic.ts

@@ -0,0 +1,16 @@
+'use client';
+
+/**
+ * Mosaic components mounted directly in the host app's tree, rather than through clerk-js. They
+ * read Clerk via `@clerk/shared/react` hooks, so a `ClerkProvider` above them is all they need.
+ *
+ * Pair with the stylesheet, which carries the design tokens and every component rule:
+ *
+ * ```css
+ * @import '@clerk/react/experimental/mosaic/styles.css' layer(clerk);
+ * ```
+ *
+ * @experimental The surface and the components behind it are subject to change.
+ */
+export { UserButton } from '@clerk/ui/experimental/mosaic';
+export type { UserButtonProps } from '@clerk/ui/experimental/mosaic';

packages/react/tsdown.config.mts

@@ -63,6 +63,7 @@ export default defineConfig((overrideOptions: Options) => {
       internal: 'src/internal.ts',
       errors: 'src/errors.ts',
       experimental: 'src/experimental.ts',
+      'experimental/mosaic': 'src/experimental/mosaic.ts',
       legacy: 'src/legacy.ts',
       types: 'src/types/index.ts',
     },
@@ -76,7 +77,12 @@ export default defineConfig((overrideOptions: Options) => {
     // Bundle @clerk/ui/register inline at build time so consumers don't need
     // @clerk/ui as a dependency. The registration code sets up globalThis.__clerkSharedModules
     // to enable @clerk/ui's shared variant to use the host app's React.
-    noExternal: ['@clerk/ui/register'],
+    //
+    // The Mosaic entry is inlined for the same reason: left external, the re-export resolves from
+    // the consumer's tree at runtime, which makes @clerk/ui a dependency and installs its whole
+    // graph (Emotion, the Solana wallet adapters, ...) for every consumer, Mosaic or not. Its build
+    // already bundles everything except React and @clerk/shared, both of which we ship anyway.
+    noExternal: ['@clerk/ui/register', '@clerk/ui/experimental/mosaic'],
     define: {
       PACKAGE_NAME: `"${pkgJson.name}"`,
       PACKAGE_VERSION: `"${pkgJson.version}"`,

packages/swingset/src/stories/menu.component.mdx

@@ -120,10 +120,10 @@ const [open, setOpen] = useState(false);
 Unlike the slot-recipe components, the Mosaic menu is themed with **StyleX**. Each styled part
 carries a stable `.cl-<slot>` class (the slots above) alongside the StyleX atoms. Consumers never
 target the hashed atomic classes — override by targeting the `.cl-*` slot from a CSS layer that wins
-over `@clerk/ui/styles.css`:
+over `@clerk/ui/experimental/mosaic/styles.css`:
 
 ```css
-@import '@clerk/ui/styles.css' layer(components);
+@import '@clerk/ui/experimental/mosaic/styles.css' layer(components);
 
 @layer overrides {
   .cl-menu-popup {

packages/swingset/src/stories/popover.component.mdx

@@ -189,10 +189,10 @@ them through your own typography (`Heading`, `Text`) inside the surface.
 Unlike the slot-recipe components, the Mosaic popover is themed with **StyleX**. Each styled part
 carries a stable `.cl-<slot>` class (the slots in the table above) alongside the StyleX atoms.
 Consumers never target the hashed atomic classes — override by targeting the `.cl-*` slot from a
-CSS layer that wins over `@clerk/ui/styles.css`:
+CSS layer that wins over `@clerk/ui/experimental/mosaic/styles.css`:
 
 ```css
-@import '@clerk/ui/styles.css' layer(components);
+@import '@clerk/ui/experimental/mosaic/styles.css' layer(components);
 
 @layer overrides {
   .cl-popover-popup[data-size='lg'] {

packages/ui/bundlewatch.config.json

@@ -33,6 +33,8 @@
     { "path": "./dist/op-plans-page*.js", "maxSize": "3KB" },
     { "path": "./dist/statement-page*.js", "maxSize": "5KB" },
     { "path": "./dist/payment-attempt-page*.js", "maxSize": "4KB" },
-    { "path": "./dist/web3-solana-wallet-buttons*.js", "maxSize": "85KB" }
+    { "path": "./dist/web3-solana-wallet-buttons*.js", "maxSize": "85KB" },
+    { "path": "./dist-mosaic/styles.css", "maxSize": "8KB" },
+    { "path": "./dist-mosaic/index.js", "maxSize": "88KB" }
   ]
 }

packages/ui/package.json

@@ -57,7 +57,12 @@
       "default": "./dist/experimental/index.js"
     },
     "./themes/shadcn.css": "./dist/themes/shadcn.css",
-    "./styles.css": {
+    "./experimental/mosaic": {
+      "types": "./dist-mosaic/index.d.ts",
+      "import": "./dist-mosaic/index.js",
+      "default": "./dist-mosaic/index.js"
+    },
+    "./experimental/mosaic/styles.css": {
       "types": "./styles.css.d.ts",
       "default": "./dist-mosaic/styles.css"
     },
@@ -81,14 +86,15 @@
     "register"
   ],
   "scripts": {
-    "build": "pnpm build:umd && pnpm build:esm && pnpm build:mosaic && pnpm check:no-rhc && pnpm type-check",
+    "build": "pnpm build:umd && pnpm build:esm && pnpm build:mosaic && pnpm check:no-rhc && pnpm check:no-emotion && pnpm type-check",
     "build:analyze": "rspack build --config rspack.config.js --env production --env analyze",
     "build:esm": "tsdown",
     "build:mosaic": "tsdown --config tsdown.mosaic.config.mts",
     "build:rsdoctor": "RSDOCTOR=true rspack build --config rspack.config.js --env production",
     "build:umd": "rspack build --config rspack.config.js --env production",
     "bundlewatch": "FORCE_COLOR=1 bundlewatch --config bundlewatch.config.json",
     "bundlewatch:fix": "node bundlewatch-fix.mjs",
+    "check:no-emotion": "node scripts/check-mosaic-emotion-free.mjs",
     "check:no-rhc": "node ../../scripts/search-for-rhc.mjs directory dist/no-rhc",
     "clean": "rimraf ./dist",
     "dev": "rspack serve --config rspack.config.js",
@@ -116,7 +122,6 @@
     "@solana/wallet-adapter-base": "catalog:module-manager",
     "@solana/wallet-adapter-react": "catalog:module-manager",
     "@solana/wallet-standard": "catalog:module-manager",
-    "@stylexjs/stylex": "0.19.0",
     "@swc/helpers": "catalog:repo",
     "copy-to-clipboard": "3.3.3",
     "core-js": "catalog:repo",
@@ -135,6 +140,7 @@
     "@rspack/plugin-react-refresh": "catalog:rspack",
     "@stylexjs/eslint-plugin": "0.19.0",
     "@stylexjs/rollup-plugin": "0.19.0",
+    "@stylexjs/stylex": "0.19.0",
     "@stylexjs/unplugin": "0.19.0",
     "@svgr/rollup": "^8.1.0",
     "@svgr/webpack": "^6.5.1",

packages/ui/scripts/check-mosaic-emotion-free.mjs

@@ -0,0 +1,23 @@
+#!/usr/bin/env node
+
+/**
+ * The `build:mosaic` entry is published as `@clerk/ui/experimental/mosaic` and mounted directly in
+ * host apps, so it must stay Emotion-free: pulling `@emotion/react` in ships a second styling
+ * runtime to every consumer. Nothing about the barrel enforces that — one legacy component reached
+ * from the graph (an `sx` prop, a `Box`, a `keyframes`) drags it back in silently. This fails the
+ * build instead.
+ */
+
+import { readFileSync } from 'node:fs';
+
+const BUNDLE = new URL('../dist-mosaic/index.js', import.meta.url);
+
+const source = readFileSync(BUNDLE, 'utf8');
+const offenders = source.split('\n').filter(line => line.includes('@emotion'));
+
+if (offenders.length > 0) {
+  console.error(`Found Emotion in the Mosaic build output (dist-mosaic/index.js):\n${offenders.join('\n')}`);
+  process.exit(1);
+}
+
+console.log('✅ No Emotion found in the Mosaic build output');

packages/ui/src/mosaic/components/menu/index.ts

@@ -1,2 +1,2 @@
 export { Menu, MenuContent, MenuItem, MenuSeparator, MenuTrigger } from './menu';
-export type { MenuContentProps, MenuItemProps, MenuProps, MenuSeparatorProps, MenuTriggerProps } from './menu';
+export type { MenuContentProps, MenuItemProps, MenuTriggerProps } from './menu';

packages/ui/src/mosaic/components/menu/menu.tsx

@@ -2,7 +2,6 @@ import type {
   MenuItemProps as PrimitiveMenuItemProps,
   MenuPopupProps,
   MenuPortalProps,
-  MenuProps,
   MenuSeparatorProps,
 } from '@clerk/headless/menu';
 import { Menu as Primitive } from '@clerk/headless/menu';
@@ -16,8 +15,6 @@ import { Icon } from '../icon';
 import { reset } from '../reset.styles';
 import { styles } from './menu.styles';
 
-export type { MenuProps, MenuSeparatorProps };
-
 export type MenuTriggerProps = MosaicComponentProps<'button'>;
 
 /**

packages/ui/src/mosaic/components/popover/index.ts

@@ -3,7 +3,6 @@ export type {
   PopoverCloseProps,
   PopoverDescriptionProps,
   PopoverPopupProps,
-  PopoverRootProps,
   PopoverSize,
   PopoverTitleProps,
   PopoverTriggerProps,

packages/ui/src/mosaic/components/popover/popover.tsx

@@ -1,4 +1,3 @@
-import type { PopoverProps as HeadlessPopoverProps } from '@clerk/headless/popover';
 import { Popover as Primitive } from '@clerk/headless/popover';
 import * as stylex from '@stylexjs/stylex';
 import React from 'react';
@@ -10,8 +9,6 @@ import { sizes, styles } from './popover.styles';
 
 export type PopoverSize = 'sm' | 'md' | 'lg';
 
-export type PopoverRootProps = HeadlessPopoverProps;
-
 /**
  * The headless parts type their props (and the `render` callback's argument) against
  * the raw tag props, which carry the non-standard HTML `color` attribute typed