feat(desktop): add system tray for background agent status

When the main window is closed, the app now stays running with a
menu bar tray icon showing agent/hub status. Users can toggle the
window visibility and quit from the tray menu.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/desktop/src/main/index.ts

@@ -57,6 +57,7 @@ import path from 'node:path'
 import { registerAllIpcHandlers, initializeApp, cleanupAll, setupDeviceConfirmation, setAuthMainWindow, handleAuthDeepLink } from './ipc/index.js'
 import { appStateManager } from '@multica/core'
 import { createUpdater, AutoUpdater } from './updater/index.js'
+import { createTray, destroyTray } from './tray.js'
 
 // CJS output will have __dirname natively, but TypeScript source needs this for type checking
 const __dirname = path.dirname(fileURLToPath(import.meta.url))
@@ -77,6 +78,7 @@ const forceOnboarding = process.argv.includes('--force-onboarding')
 
 let win: BrowserWindow | null
 let updater: AutoUpdater
+let isQuitting = false
 
 // ============================================================================
 // Custom Protocol for Auth (multica://)
@@ -108,8 +110,9 @@ if (!gotTheLock) {
   app.quit()
 } else {
   app.on('second-instance', (_event, commandLine) => {
-    // Focus window
+    // Show and focus window
     if (win) {
+      if (!win.isVisible()) win.show()
       if (win.isMinimized()) win.restore()
       win.focus()
     }
@@ -144,6 +147,14 @@ function createWindow() {
     return { action: 'deny' }
   })
 
+  // Hide window on close instead of quitting (tray keeps running)
+  win.on('close', (event) => {
+    if (!isQuitting) {
+      event.preventDefault()
+      win?.hide()
+    }
+  })
+
   if (VITE_DEV_SERVER_URL) {
     win.loadURL(VITE_DEV_SERVER_URL)
   } else {
@@ -152,19 +163,20 @@ function createWindow() {
 }
 
 app.on('window-all-closed', () => {
-  if (process.platform !== 'darwin') {
-    app.quit()
-    win = null
-  }
+  // Keep app running with tray on all platforms
 })
 
 app.on('activate', () => {
   if (BrowserWindow.getAllWindows().length === 0) {
     createWindow()
+  } else if (win && !win.isVisible()) {
+    win.show()
   }
 })
 
 app.on('before-quit', () => {
+  isQuitting = true
+  destroyTray()
   cleanupAll()
 })
 
@@ -187,10 +199,11 @@ app.whenReady().then(async () => {
 
   createWindow()
 
-  // Set up device confirmation flow and auth (requires window)
+  // Set up device confirmation flow, auth, and tray (requires window)
   if (win) {
     setupDeviceConfirmation(win)
     setAuthMainWindow(win)
+    createTray(win)
   }
 
   // Initialize auto-updater

apps/desktop/src/main/ipc/hub.ts

@@ -74,7 +74,7 @@ function getHub(): Hub {
 /**
  * Get the default agent.
  */
-function getDefaultAgent(): AsyncAgent | null {
+export function getDefaultAgent(): AsyncAgent | null {
   if (!hub || !defaultAgentId) return null
   return hub.getAgent(defaultAgentId) ?? null
 }

apps/desktop/src/main/ipc/index.ts

@@ -3,7 +3,7 @@
  */
 export { registerAgentIpcHandlers, cleanupAgent } from './agent.js'
 export { registerSkillsIpcHandlers } from './skills.js'
-export { registerHubIpcHandlers, cleanupHub, initializeHub, setupDeviceConfirmation } from './hub.js'
+export { registerHubIpcHandlers, cleanupHub, initializeHub, setupDeviceConfirmation, getDefaultAgent } from './hub.js'
 export { registerProfileIpcHandlers } from './profile.js'
 export { registerProviderIpcHandlers } from './provider.js'
 export { registerChannelsIpcHandlers } from './channels.js'

apps/desktop/src/main/tray.ts

@@ -0,0 +1,113 @@
+/**
+ * System tray (menu bar) for the desktop app.
+ *
+ * Shows agent/hub status and allows window show/hide even
+ * when the main window is closed.
+ */
+import { Tray, Menu, nativeImage, app, type BrowserWindow } from 'electron'
+import path from 'node:path'
+import { getCurrentHub, getDefaultAgent } from './ipc/hub.js'
+
+let tray: Tray | null = null
+let mainWindowRef: BrowserWindow | null = null
+let statusInterval: ReturnType<typeof setInterval> | null = null
+
+/**
+ * Create the system tray and start status polling.
+ */
+export function createTray(window: BrowserWindow): void {
+  mainWindowRef = window
+
+  const iconPath = path.join(process.env.APP_ROOT!, 'build', 'icon.png')
+  const icon = nativeImage.createFromPath(iconPath)
+  const trayIcon = icon.resize({ width: 16, height: 16 })
+
+  if (process.platform === 'darwin') {
+    trayIcon.setTemplateImage(true)
+  }
+
+  tray = new Tray(trayIcon)
+  tray.setToolTip('Multica')
+
+  // Click to toggle window visibility
+  tray.on('click', toggleWindowVisibility)
+
+  // Initial menu
+  updateTrayMenu()
+
+  // Poll status every 2 seconds
+  statusInterval = setInterval(updateTrayMenu, 2000)
+}
+
+/**
+ * Destroy tray and stop polling.
+ */
+export function destroyTray(): void {
+  if (statusInterval) {
+    clearInterval(statusInterval)
+    statusInterval = null
+  }
+  if (tray) {
+    tray.destroy()
+    tray = null
+  }
+  mainWindowRef = null
+}
+
+function toggleWindowVisibility(): void {
+  if (!mainWindowRef || mainWindowRef.isDestroyed()) return
+
+  if (mainWindowRef.isVisible()) {
+    mainWindowRef.hide()
+  } else {
+    mainWindowRef.show()
+    mainWindowRef.focus()
+  }
+}
+
+function updateTrayMenu(): void {
+  if (!tray) return
+
+  const hub = getCurrentHub()
+  const agent = getDefaultAgent()
+
+  let agentStatus = 'Initializing'
+  let hubStatus = 'Disconnected'
+
+  if (hub) {
+    hubStatus = hub.connectionState === 'connected' ? 'Connected' : 'Disconnected'
+  }
+
+  if (agent && !agent.closed) {
+    if (agent.isStreaming) {
+      agentStatus = 'Streaming'
+    } else if (agent.isRunning) {
+      agentStatus = 'Running'
+    } else {
+      agentStatus = 'Idle'
+    }
+  }
+
+  tray.setToolTip(`Multica - Agent: ${agentStatus}`)
+
+  const windowVisible = mainWindowRef && !mainWindowRef.isDestroyed() && mainWindowRef.isVisible()
+
+  const menu = Menu.buildFromTemplate([
+    { label: `Agent: ${agentStatus}`, enabled: false },
+    { label: `Hub: ${hubStatus}`, enabled: false },
+    { type: 'separator' },
+    {
+      label: windowVisible ? 'Hide Window' : 'Show Window',
+      click: toggleWindowVisibility,
+    },
+    { type: 'separator' },
+    {
+      label: 'Quit Multica',
+      click: () => {
+        app.quit()
+      },
+    },
+  ])
+
+  tray.setContextMenu(menu)
+}