diff --git a/js/forge.config.ts b/js/forge.config.ts
index 56fb53e..c38cb49 100644
--- a/js/forge.config.ts
+++ b/js/forge.config.ts
@@ -12,6 +12,9 @@ const config: ForgeConfig = {
     asar: true,
     icon: './assets/flowy',
     appBundleId: 'live.flowy.llink',
+    protocols: [
+      { name: 'llink', schemes: ['llink'] },
+    ],
     extendInfo: {
       NSMicrophoneUsageDescription: 'llink needs microphone access to record audio messages.',
       NSCameraUsageDescription: 'llink needs camera access to record video messages.',
diff --git a/js/src/main.ts b/js/src/main.ts
index 31eefdf..4516720 100644
--- a/js/src/main.ts
+++ b/js/src/main.ts
@@ -25,6 +25,21 @@ if (process.platform === 'darwin' && !app.isPackaged) {
   app.dock?.setIcon(path.join(__dirname, '../../assets/icon.png'));
 }
 
+// Single-instance lock: on Windows/Linux, clicking a llink:// URL launches a new
+// process. The lock makes the losing instance quit and fires `second-instance` on
+// the primary, so we focus the existing window instead of spawning a duplicate.
+// macOS uses `open-url` instead and doesn't need this, but the lock is harmless.
+if (!app.requestSingleInstanceLock()) {
+  app.quit();
+}
+
+// Register llink:// as the default handler for this app. macOS also gets this
+// declaratively via CFBundleURLTypes (forge.config.ts `protocols`); Windows relies
+// on this runtime call (Squirrel doesn't register protocols on install).
+if (!app.isDefaultProtocolClient('llink')) {
+  app.setAsDefaultProtocolClient('llink');
+}
+
 let mainWindow: BrowserWindow | null = null;
 let autoplayWindow: BrowserWindow | null = null;
 let huddleWindow: BrowserWindow | null = null;
@@ -438,6 +453,8 @@ ipcMain.on('app:set-dock-badge', (_event, count: number) => {
   }
 });
 
+ipcMain.handle('app:get-version', () => app.getVersion());
+
 ipcMain.handle('link:fetch-metadata', async (_event, url: string) => {
   if (typeof url !== 'string') return null;
   try {
@@ -517,5 +534,27 @@ app.on('activate', () => {
   }
 });
 
+function focusMainWindow() {
+  if (!mainWindow) return;
+  if (mainWindow.isMinimized()) mainWindow.restore();
+  if (!mainWindow.isVisible()) mainWindow.show();
+  mainWindow.focus();
+}
+
+// macOS delivers llink:// URLs via this event, both when the app is already
+// running and on cold start (after `ready`). We prevent the default to silence
+// Electron's warning and focus the window — OS-level focus alone won't restore
+// a hidden or minimized window. Cold start is handled by createWindow().
+app.on('open-url', (event) => {
+  event.preventDefault();
+  focusMainWindow();
+});
+
+// Windows/Linux: the OS launches a second process with the URL in argv; the
+// single-instance lock diverts it here on the primary instance.
+app.on('second-instance', () => {
+  focusMainWindow();
+});
+
 // In this file you can include the rest of your app's specific main process
 // code. You can also put them in separate files and import them here.