First attempt at fixing windows auth.

public/electron.js

@@ -8,7 +8,9 @@ import {
   createWindow,
   setupMainWindowIPC,
   setupMainWindowAppEvents,
-  setupDevAuthServer
+  setupDevAuthServer,
+  setupSingleInstanceLock,
+  handleDeepLinkFromArgv
 } from './mainWindow.js'
 
 // --- Keytar-backed auth session storage (main process) ---
@@ -27,14 +29,19 @@ try {
 const KEYTAR_SERVICE = app.name || 'Farm Control'
 const KEYTAR_ACCOUNT = 'authSession'
 
-app.whenReady().then(() => {
-  createWindow()
-  registerGlobalShortcuts()
-  setupSpotlightIPC()
-  setupMainWindowIPC()
-  setupMainWindowAppEvents(app)
-  setupDevAuthServer()
-})
+const gotTheLock = setupSingleInstanceLock(app)
+
+if (gotTheLock) {
+  app.whenReady().then(() => {
+    createWindow()
+    registerGlobalShortcuts()
+    setupSpotlightIPC()
+    setupMainWindowIPC()
+    setupMainWindowAppEvents(app)
+    setupDevAuthServer()
+    handleDeepLinkFromArgv()
+  })
+}
 
 app.on('will-quit', () => {
   globalShortcut.unregisterAll()

public/mainWindow.js

@@ -7,6 +7,72 @@ const __dirname = dirname(__filename)
 
 let win
 
+const PROTOCOL_PREFIX = 'farmcontrol://'
+
+function findProtocolUrl(args) {
+  return args.find(
+    (arg) => typeof arg === 'string' && arg.startsWith(PROTOCOL_PREFIX)
+  )
+}
+
+function sendNavigateToRenderer(redirectPath) {
+  const deliver = () => {
+    win.webContents.send('navigate', redirectPath)
+    win.show()
+    win.focus()
+  }
+
+  if (!win || win.isDestroyed()) {
+    createWindow()
+    win.webContents.once('did-finish-load', () => {
+      setTimeout(deliver, 100)
+    })
+    return
+  }
+
+  if (win.webContents.isLoading()) {
+    win.webContents.once('did-finish-load', () => {
+      setTimeout(deliver, 100)
+    })
+    return
+  }
+
+  deliver()
+}
+
+export function handleDeepLink(url) {
+  if (!url?.startsWith(`${PROTOCOL_PREFIX}app`)) return
+  const redirectPath = url.replace(`${PROTOCOL_PREFIX}app`, '') || '/'
+  sendNavigateToRenderer(redirectPath)
+}
+
+export function handleDeepLinkFromArgv() {
+  if (process.platform === 'darwin') return
+  const url = findProtocolUrl(process.argv)
+  if (url) handleDeepLink(url)
+}
+
+export function setupSingleInstanceLock(app) {
+  const gotTheLock = app.requestSingleInstanceLock()
+  if (!gotTheLock) {
+    app.quit()
+    return false
+  }
+
+  app.on('second-instance', (_event, commandLine) => {
+    const url = findProtocolUrl(commandLine)
+    if (url) {
+      handleDeepLink(url)
+    } else if (win && !win.isDestroyed()) {
+      if (win.isMinimized()) win.restore()
+      win.show()
+      win.focus()
+    }
+  })
+
+  return true
+}
+
 function attachKeyboardShortcuts(browserWindow) {
   if (!browserWindow) return
   // Keyboard shortcuts for the main window can be added here if needed
@@ -155,13 +221,7 @@ export function setupMainWindowAppEvents(app) {
 
   app.on('open-url', (event, url) => {
     event.preventDefault()
-    if (url.startsWith('farmcontrol://app')) {
-      // Extract the path/query after 'farmcontrol://app'
-      const redirectPath = url.replace('farmcontrol://app', '') || '/'
-      if (win && win.webContents) {
-        win.webContents.send('navigate', redirectPath)
-      }
-    }
+    handleDeepLink(url)
   })
 }