diff --git a/packages/react/src/plugin-pages.ts b/packages/react/src/plugin-pages.ts
index 1c847f02f..1020f3a74 100644
--- a/packages/react/src/plugin-pages.ts
+++ b/packages/react/src/plugin-pages.ts
@@ -1,7 +1,13 @@
-import { dirname, relative } from 'pathslash';
+import { readFileSync } from 'node:fs';
+import { dirname, relative, resolve } from 'pathslash';
 import type { Plugin } from 'vite';
-import { createPagesPlugin, generateComponentManifest } from 'void/pages';
+import {
+  createPagesPlugin,
+  generateComponentManifest,
+  resolveEffectiveLayoutChain,
+} from 'void/pages';
 import type { PageScanResult, StaticPageDataBuildOptions } from 'void/pages';
+import { findIslandImports, resolveSpecifier } from 'void/pages-islands-plugin';
 
 const CLIENT_ENTRY_ID = 'virtual:void-pages-client';
 const WORKER_ENVIRONMENT_NAME = 'void_worker';
@@ -62,10 +68,15 @@ export function pagesPlugin(pagesDir: string, options?: PagesPluginOptions): Plu
           },
           optimizeDeps: {
             exclude: ['@void/react'],
+            // Crawl page modules before the first client request so third-party
+            // imports are pre-bundled instead of triggering a full reload.
+            entries: clientOptimizeEntries(await scan(), pagesDir, root),
             // Pre-include React entries that are discovered late via dynamic
             // imports during SPA navigation, avoiding a full-page reload
-            // from Vite's dep optimizer.
-            include: CLIENT_OPTIMIZE_DEPS,
+            // from Vite's dep optimizer. void/pages-client and
+            // void/pages-prefetch are reached only through virtual entries and
+            // the excluded @void/react, so the scanner cannot see them.
+            include: [...CLIENT_OPTIMIZE_DEPS, 'void/pages-client', 'void/pages-prefetch'],
           },
           ssr: {
             optimizeDeps: {
@@ -109,6 +120,49 @@ export function pagesPlugin(pagesDir: string, options?: PagesPluginOptions): Plu
   });
 }
 
+function clientOptimizeEntries(
+  scan: PageScanResult | null,
+  pagesDir: string,
+  root: string,
+): Array<string> {
+  if (!scan) {
+    return [];
+  }
+  const browserFiles = new Set<string>();
+  const islandFiles = new Set<string>();
+  for (const page of scan.pages) {
+    const layouts = resolveEffectiveLayoutChain(page, scan.layouts, scan.namedLayouts);
+    if (page.island) {
+      islandFiles.add(resolve(pagesDir, page.componentPath));
+      for (const layout of layouts) {
+        if (layout.island) {
+          islandFiles.add(resolve(pagesDir, layout.filePath));
+        }
+      }
+    } else {
+      browserFiles.add(resolve(pagesDir, page.componentPath));
+      for (const layout of layouts) {
+        browserFiles.add(resolve(pagesDir, layout.filePath));
+      }
+    }
+  }
+  // Only hydrated components run in the browser; island pages and their
+  // unmarked imports may depend on Worker-only packages.
+  for (const file of islandFiles) {
+    if (!/\.island\.(tsx|jsx)$/.test(file)) {
+      continue;
+    }
+    for (const { specifier } of findIslandImports(readFileSync(file, 'utf8'), file)) {
+      const component = resolveSpecifier(specifier, dirname(file), ['.tsx', '.jsx', '.ts', '.js']);
+      if (component) {
+        browserFiles.add(component);
+      }
+    }
+  }
+  // Entries are glob patterns, so route names such as [id] must be literal.
+  return [...browserFiles].map((file) => relative(root, file).replace(/[()[\]{}*?!|]/g, '\\$&'));
+}
+
 function generateRendererModule(scan: PageScanResult, pagesDir: string, isDev: boolean): string {
   const preambleScript = isDev ? REACT_REFRESH_PREAMBLE : '';
 
diff --git a/packages/react/test/integration/react-pages-client.test.ts b/packages/react/test/integration/react-pages-client.test.ts
index ff4cbc3d2..3c8b1e22b 100644
--- a/packages/react/test/integration/react-pages-client.test.ts
+++ b/packages/react/test/integration/react-pages-client.test.ts
@@ -41,12 +41,31 @@ const ROOT = join(import.meta.dirname, '..', '..', '..', '..');
 const REACT_PAGES_ROOT = join(ROOT, 'playground/react-pages');
 const REACT_PAGES_LAYOUT = join(REACT_PAGES_ROOT, 'pages/layout.tsx');
 const LATE_WORKER_DEPS_ROOT = join(REACT_PAGES_ROOT, 'node_modules/@void-repro');
+const OPTIMIZER_PROBE_FILES = {
+  '_optimizer-helper.ts': `import { value } from '@void-repro/worker-only';
+export const readWorkerValue = () => value;`,
+  '_optimizer-browser.ts': `export { value } from '@void-repro/browser-only';`,
+  'optimizer-probe/[id].tsx': `import { value } from '../_optimizer-browser';
+export default function Probe() { return <p>{value}</p>; }`,
+  'optimizer-probe/[id].server.ts': `import { defineHandler } from 'void/handler';
+import { readWorkerValue } from '../_optimizer-helper';
+export const loader = defineHandler(() => ({ value: readWorkerValue() }));`,
+  'optimizer-island.island.tsx': `import Probe from './_OptimizerIsland' with { island: 'load' };
+import { readWorkerValue } from './_optimizer-helper';
+export default function IslandPage() { return <><p>{readWorkerValue()}</p><Probe /></>; }`,
+  '_OptimizerIsland.tsx': `import { value } from '@void-repro/island-only';
+export default function Probe() { return <p>{value}</p>; }`,
+};
 let DEV_BASE: string;
 let PREVIEW_BASE: string;
 
 let browser: Browser;
 
-function writeLateWorkerDep(name: string, source: string) {
+function writeLateWorkerDep(
+  name: string,
+  source: string,
+  exports: string | Record<string, string> = './index.js',
+) {
   const packageDir = join(LATE_WORKER_DEPS_ROOT, name);
   mkdirSync(packageDir, { recursive: true });
   writeFileSync(
@@ -55,7 +74,7 @@ function writeLateWorkerDep(name: string, source: string) {
       name: `@void-repro/${name}`,
       version: '1.0.0',
       type: 'module',
-      exports: './index.js',
+      exports,
     }),
   );
   writeFileSync(join(packageDir, 'index.js'), source);
@@ -63,6 +82,16 @@ function writeLateWorkerDep(name: string, source: string) {
 
 function installLateWorkerDeps() {
   rmSync(LATE_WORKER_DEPS_ROOT, { recursive: true, force: true });
+  writeLateWorkerDep('worker-only', 'export const value = "Worker value";', {
+    workerd: './index.js',
+  });
+  writeLateWorkerDep('browser-only', 'export const value = "Browser value";');
+  writeLateWorkerDep('island-only', 'export const value = "Island value";');
+  for (const [file, source] of Object.entries(OPTIMIZER_PROBE_FILES)) {
+    const path = join(REACT_PAGES_ROOT, 'pages', file);
+    mkdirSync(join(path, '..'), { recursive: true });
+    writeFileSync(path, source);
+  }
   writeLateWorkerDep(
     'boundary',
     `import React from 'react';
@@ -740,6 +769,25 @@ describe('react-pages client (dev)', () => {
       await killChild(child);
     }
     rmSync(LATE_WORKER_DEPS_ROOT, { recursive: true, force: true });
+    for (const file of Object.keys(OPTIMIZER_PROBE_FILES)) {
+      rmSync(join(REACT_PAGES_ROOT, 'pages', file), { force: true });
+    }
+    rmSync(join(REACT_PAGES_ROOT, 'pages/optimizer-probe'), { recursive: true, force: true });
+  });
+
+  it('dev: prebundles browser roots without scanning server-only dependencies', async () => {
+    await vi.waitFor(() => {
+      const metadata = JSON.parse(
+        readFileSync(join(REACT_PAGES_ROOT, 'node_modules/.vite/deps/_metadata.json'), 'utf8'),
+      );
+      expect(metadata.optimized).toHaveProperty('@void-repro/browser-only');
+      expect(metadata.optimized).toHaveProperty('@void-repro/island-only');
+      expect(metadata.optimized).not.toHaveProperty('@void-repro/worker-only');
+    });
+    expect(stderr).not.toContain('Failed to run dependency scan');
+    const response = await fetch(`${DEV_BASE}/optimizer-probe/example`);
+    expect(response.status).toBe(200);
+    expect(await response.text()).toContain('Browser value');
   });
 
   it('dev: cold SSR startup does not hit invalid React hook calls', () => {
diff --git a/packages/react/test/unit/plugin-pages.test.ts b/packages/react/test/unit/plugin-pages.test.ts
index 365027e65..ef4c5a2ca 100644
--- a/packages/react/test/unit/plugin-pages.test.ts
+++ b/packages/react/test/unit/plugin-pages.test.ts
@@ -202,10 +202,15 @@ describe('pagesPlugin dev config', () => {
     rmSync(TMP, { recursive: true, force: true });
   });
 
-  it('pre-optimizes React dependencies in the Cloudflare worker environment', async () => {
+  it('pre-optimizes page dependencies in the client and Cloudflare worker environments', async () => {
+    writePage('index.tsx', 'export default function Home() { return <h1>Home</h1>; }');
     const config = await loadServeConfig();
 
     expect(config).toMatchObject({
+      optimizeDeps: {
+        entries: ['pages/index.tsx'],
+        include: expect.arrayContaining(['void/pages-client', 'void/pages-prefetch']),
+      },
       environments: {
         void_worker: {
           optimizeDeps: {
@@ -223,6 +228,65 @@ describe('pagesPlugin dev config', () => {
     });
   });
 
+  it('scans browser roots without promoting server-only helpers to client entries', async () => {
+    writePage('index.tsx', 'export default function Home() { return null; }');
+    writePage('index.server.ts', 'import "./_worker-helper";');
+    writePage('_worker-helper.ts', 'import "worker-only-package";');
+    writePage('layout.tsx', 'export default function Layout({ children }) { return children; }');
+    writePage(
+      'users/[id].dev.tsx',
+      'export const layout = "profile"; export default function User() { return null; }',
+    );
+    writePage('users/[id].prod.tsx', 'export default function User() { return null; }');
+    writePage('_layouts/profile.tsx', 'export default function Profile() { return null; }');
+    writePage('_layouts/unused.tsx', 'import "worker-only-package";');
+    writePage('static/layout.tsx', 'import "worker-only-package";');
+    writePage('static/index.island.tsx', 'export default function Static() { return null; }');
+    writePage('__tests__/page.test.tsx', 'import "test-only-package";');
+
+    const config = await loadServeConfig();
+    expect(config).toMatchObject({
+      optimizeDeps: {
+        entries: expect.arrayContaining([
+          'pages/index.tsx',
+          'pages/layout.tsx',
+          'pages/users/\\[id\\].dev.tsx',
+          'pages/_layouts/profile.tsx',
+        ]),
+      },
+    });
+    expect((config.optimizeDeps as { entries: Array<string> }).entries).toHaveLength(4);
+  });
+
+  it('scans hydrated components in island pages and layouts, including outside pages', async () => {
+    writePage(
+      'index.island.tsx',
+      `
+      import Counter from './_Counter' with { island: 'load' };
+      import './_worker-helper';
+      export default function Home() { return <Counter />; }
+    `,
+    );
+    writePage(
+      'layout.island.tsx',
+      `
+      import Header from '../components/Header.tsx' with { island: 'visible' };
+      export default function Layout({ children }) { return <><Header />{children}</>; }
+    `,
+    );
+    writePage('_Counter.tsx', 'export default function Counter() { return null; }');
+    writePage('../components/Header.tsx', 'export default function Header() { return null; }');
+    writePage('_worker-helper.ts', 'import "worker-only-package";');
+
+    const config = await loadServeConfig();
+    expect(config).toMatchObject({
+      optimizeDeps: {
+        entries: expect.arrayContaining(['pages/_Counter.tsx', 'components/Header.tsx']),
+      },
+    });
+    expect((config.optimizeDeps as { entries: Array<string> }).entries).toHaveLength(2);
+  });
+
   it('includes only the React entry points needed by each environment', async () => {
     const config = (await loadServeConfig()) as {
       optimizeDeps: { include: Array<string> };