diff --git a/client/src/components/apps/tabs/RepositorySourcePanel.jsx b/client/src/components/apps/tabs/RepositorySourcePanel.jsx
index 97622d45f9..15fc75a2e4 100644
--- a/client/src/components/apps/tabs/RepositorySourcePanel.jsx
+++ b/client/src/components/apps/tabs/RepositorySourcePanel.jsx
@@ -342,6 +342,7 @@ export default function RepositorySourcePanel({ appId, appName, onUpdated, refre
             <li>Pull the application checkout from its configured origin</li>
             {companions.length > 0 && <li>Pull {companions.length} independent companion checkout{companions.length === 1 ? '' : 's'}</li>}
             <li>Install dependencies and run the app&apos;s setup script when configured</li>
+            <li>Rebuild the production UI when a build script is configured</li>
             {status?.updateRestartsApp && <li>Restart the app&apos;s managed processes</li>}
           </ul>
         </div>
diff --git a/client/src/components/apps/tabs/RepositorySourcePanel.test.jsx b/client/src/components/apps/tabs/RepositorySourcePanel.test.jsx
index e5d84b4e3e..cef4464cac 100644
--- a/client/src/components/apps/tabs/RepositorySourcePanel.test.jsx
+++ b/client/src/components/apps/tabs/RepositorySourcePanel.test.jsx
@@ -148,6 +148,7 @@ describe('managed app repository sources', () => {
     fireEvent.click(await screen.findByRole('button', { name: 'Sync fork & update app' }));
     const dialog = await screen.findByRole('dialog');
     expect(dialog).toHaveTextContent('Pull 1 independent companion checkout');
+    expect(dialog).toHaveTextContent('Rebuild the production UI when a build script is configured');
     expect(dialog).toHaveTextContent('Restart the app\'s managed processes');
 
     fireEvent.click(screen.getByRole('button', { name: 'Sync fork and update' }));
diff --git a/server/services/appUpdater.js b/server/services/appUpdater.js
index ccc854d265..0b67ea1cd6 100644
--- a/server/services/appUpdater.js
+++ b/server/services/appUpdater.js
@@ -8,6 +8,7 @@ import { bufferedSpawnOrThrow } from '../lib/bufferedSpawn.js';
 import { parseCommandArgs } from '../lib/commandSecurity.js';
 import { isDetachedRunning, spawnDetached } from '../lib/detachedSpawn.js';
 import { PORTOS_APP_ID } from '../lib/appIdentity.js';
+import { parseBuildCommand } from './appBuilder.js';
 import { syncManagedAppFork } from './managedAppRepositories.js';
 
 const CMD_TIMEOUT_MS = 5 * 60 * 1000;
@@ -70,7 +71,10 @@ async function startDashboardHandoff(app) {
  * 2. install dependencies in each package directory (Bun apps use their
  *    frozen lockfile; existing apps retain npm install)
  * 3. run setup with the same package manager when the script exists
- * 4. Restart PM2 processes
+ * 4. rebuild the production UI when a build command or `scripts.build` exists
+ *    (a pull that only restarts leaves `client/dist` stale and PortOS then
+ *    reports "install out of sync")
+ * 5. Restart PM2 processes
  *
  * @param {object} app - The app object (must have repoPath, pm2ProcessNames, pm2Home)
  * @param {function} emit - Callback (step, status, message) for progress updates
@@ -143,14 +147,28 @@ async function _doUpdate(app, emit, { syncFork }) {
   }
 
   const pkgPath = join(dir, 'package.json');
-  if (existsSync(pkgPath)) {
-    const pkg = JSON.parse(await readFile(pkgPath, 'utf-8'));
-    if (pkg.scripts?.setup) {
-      emit('setup', 'running', 'Running setup...');
-      await runCommand(packageManagerCommand, ['run', 'setup'], dir);
-      emit('setup', 'done', 'Setup complete');
-      steps.push({ step: 'setup', success: true });
-    }
+  const pkg = existsSync(pkgPath) ? JSON.parse(await readFile(pkgPath, 'utf-8')) : null;
+  if (pkg?.scripts?.setup) {
+    emit('setup', 'running', 'Running setup...');
+    await runCommand(packageManagerCommand, ['run', 'setup'], dir);
+    emit('setup', 'done', 'Setup complete');
+    steps.push({ step: 'setup', success: true });
+  }
+
+  const configuredBuild = typeof app.buildCommand === 'string' ? app.buildCommand.trim() : '';
+  let build;
+  if (configuredBuild) {
+    const parsed = parseBuildCommand(configuredBuild);
+    if (!parsed.ok) throw new Error(parsed.message);
+    build = { cmd: parsed.cmd, args: parsed.args };
+  } else if (pkg?.scripts?.build) {
+    build = { cmd: packageManagerCommand, args: ['run', 'build'] };
+  }
+  if (build) {
+    emit('build', 'running', 'Building production UI...');
+    await runCommand(build.cmd, build.args, dir);
+    emit('build', 'done', 'Production UI built');
+    steps.push({ step: 'build', success: true });
   }
 
   const processNames = app.pm2ProcessNames || [];
diff --git a/server/services/appUpdater.test.js b/server/services/appUpdater.test.js
index ba744df67e..2a7ba3f241 100644
--- a/server/services/appUpdater.test.js
+++ b/server/services/appUpdater.test.js
@@ -15,7 +15,10 @@ const mock = vi.hoisted(() => ({
 
 vi.mock('./git.js', () => ({ pull: mock.pull }));
 vi.mock('./pm2.js', () => ({ restartApp: mock.restart }));
-vi.mock('../lib/bufferedSpawn.js', () => ({ bufferedSpawnOrThrow: mock.spawn }));
+vi.mock('../lib/bufferedSpawn.js', async (importOriginal) => {
+  const actual = await importOriginal();
+  return { ...actual, bufferedSpawnOrThrow: mock.spawn };
+});
 vi.mock('../lib/detachedSpawn.js', () => ({
   isDetachedRunning: mock.dashboardRunning,
   spawnDetached: mock.dashboardOpen,
@@ -54,6 +57,7 @@ describe('managed app updates', () => {
   });
 
   it('uses Bun and its frozen lockfile for Bun-managed apps', async () => {
+    await writeFile(join(repo, 'package.json'), JSON.stringify({ scripts: { setup: 'example-setup', build: 'vite build' } }));
     const emit = vi.fn();
     const companionRepo = join(repo, '..', 'eidoverse-video');
     const bunCommand = join(repo, 'tools with spaces', 'bun');
@@ -72,6 +76,7 @@ describe('managed app updates', () => {
     expect(mock.spawn).toHaveBeenCalledWith(bunCommand, ['install', '--frozen-lockfile'], expect.objectContaining({ cwd: repo }));
     expect(mock.spawn).toHaveBeenCalledWith(bunCommand, ['install', '--frozen-lockfile'], expect.objectContaining({ cwd: join(repo, 'client') }));
     expect(mock.spawn).toHaveBeenCalledWith(bunCommand, ['run', 'setup'], expect.objectContaining({ cwd: repo }));
+    expect(mock.spawn).toHaveBeenCalledWith(bunCommand, ['run', 'build'], expect.objectContaining({ cwd: repo }));
     expect(mock.spawn).not.toHaveBeenCalledWith('npm', expect.anything(), expect.anything());
     expect(emit).toHaveBeenCalledWith('git-pull:companion-1', 'done', 'Already up to date');
     expect(emit).toHaveBeenCalledWith('bun-install:root', 'done', 'root dependencies installed');
@@ -139,4 +144,68 @@ describe('managed app updates', () => {
     expect(mock.dashboardOpen).not.toHaveBeenCalled();
     expect(mock.restart).toHaveBeenCalledWith('portos-server', undefined);
   });
+
+  it('rebuilds the production UI before restarting so a managed update does not leave a stale client bundle', async () => {
+    const emit = vi.fn();
+    const managed = {
+      id: 'portos-default',
+      name: 'PortOS',
+      type: 'express',
+      repoPath: repo,
+      buildCommand: 'npm run build',
+      pm2ProcessNames: ['portos-server'],
+    };
+
+    const result = await updateApp(managed, emit);
+
+    expect(result.success).toBe(true);
+    expect(result.steps.some((step) => step.step === 'build' && step.success)).toBe(true);
+    expect(mock.spawn).toHaveBeenCalledWith(
+      'npm',
+      ['run', 'build'],
+      expect.objectContaining({ cwd: repo }),
+    );
+    const buildCall = mock.spawn.mock.invocationCallOrder[
+      mock.spawn.mock.calls.findIndex((call) => call[0] === 'npm' && call[1]?.[1] === 'build')
+    ];
+    expect(buildCall).toBeLessThan(mock.restart.mock.invocationCallOrder[0]);
+    expect(emit).toHaveBeenCalledWith('build', 'done', 'Production UI built');
+  });
+
+  it('rebuilds from package.json when no explicit build command is configured', async () => {
+    await writeFile(join(repo, 'package.json'), JSON.stringify({ scripts: { build: 'vite build' } }));
+    const emit = vi.fn();
+
+    await updateApp({ name: 'Example App', type: 'express', repoPath: repo, pm2ProcessNames: [] }, emit);
+
+    expect(mock.spawn).toHaveBeenCalledWith(
+      'npm',
+      ['run', 'build'],
+      expect.objectContaining({ cwd: repo }),
+    );
+    expect(emit).toHaveBeenCalledWith('build', 'done', 'Production UI built');
+  });
+
+  it('does not invent a production build when the app has none', async () => {
+    const emit = vi.fn();
+
+    await updateApp({ name: 'Example App', type: 'express', repoPath: repo, pm2ProcessNames: [] }, emit);
+
+    expect(mock.spawn).not.toHaveBeenCalledWith('npm', ['run', 'build'], expect.anything());
+    expect(emit).not.toHaveBeenCalledWith('build', expect.anything(), expect.anything());
+  });
+
+  it('refuses a disallowed build command before restarting', async () => {
+    const emit = vi.fn();
+
+    await expect(updateApp({
+      name: 'Example App',
+      type: 'express',
+      repoPath: repo,
+      buildCommand: 'rm -rf /',
+      pm2ProcessNames: ['example-app'],
+    }, emit)).rejects.toThrow(/not allowed/);
+
+    expect(mock.restart).not.toHaveBeenCalled();
+  });
 });