ui: detect outdated daemon via WailsUIReady probe

Add a no-op WailsUIReady RPC the UI probes once at startup. A reachable
daemon that returns Unimplemented predates this UI and is too old to
drive it; the probe distinguishes that from an unreachable daemon. On an
outdated daemon the UI fires a localized OS notification, since the main
window may not open to show an in-app error.

Proto regenerated with protoc 33.1 to keep the v6.33.1 header.

client/ui/frontend/src/lib/compat.ts

@@ -0,0 +1,19 @@
+import { Compat } from "@bindings/services";
+
+let cached: boolean | null = null;
+
+/**
+ * isDaemonCompatible probes whether the running daemon implements the WailsUIReady
+ * RPC. A false result means the daemon predates this UI (Unimplemented) and is too
+ * old to drive it. The Go side returns an error instead when the daemon is simply
+ * unreachable, so a throw here is NOT an outdated daemon — treat it as "unknown"
+ * and let the normal connection flow report it.
+ *
+ * The result is cached for the session: daemon identity does not change without a
+ * UI restart, and a freshly started daemon is reachable again under the same socket.
+ */
+export async function isDaemonCompatible(): Promise<boolean> {
+    if (cached !== null) return cached;
+    cached = await Compat.DaemonReady();
+    return cached;
+}

client/ui/i18n/locales/de/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "NetBird beenden"
     },
+    "notify.daemonOutdated.title": {
+        "message": "NetBird-Dienst ist veraltet"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Aktualisieren Sie den NetBird-Dienst, um diese App zu verwenden."
+    },
     "notify.update.title": {
         "message": "NetBird-Update verfügbar"
     },

client/ui/i18n/locales/en/common.json

@@ -143,6 +143,14 @@
         "message": "Quit NetBird",
         "description": "Tray menu item that fully exits the app and removes the tray icon. Keep short."
     },
+    "notify.daemonOutdated.title": {
+        "message": "NetBird service is outdated",
+        "description": "Title of the OS desktop notification shown when the running daemon is too old for this UI."
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Update the NetBird service to use this app.",
+        "description": "Body of the desktop notification telling the user to upgrade the daemon."
+    },
     "notify.update.title": {
         "message": "NetBird update available",
         "description": "Title of the OS desktop notification shown when an app update is available."

client/ui/i18n/locales/es/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "Salir de NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "El servicio de NetBird está desactualizado"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Actualice el servicio de NetBird para usar esta aplicación."
+    },
     "notify.update.title": {
         "message": "Actualización de NetBird disponible"
     },

client/ui/i18n/locales/fr/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "Quitter NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "Le service NetBird est obsolète"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Mettez à jour le service NetBird pour utiliser cette application."
+    },
     "notify.update.title": {
         "message": "Mise à jour de NetBird disponible"
     },

client/ui/i18n/locales/hu/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "NetBird bezárása"
     },
+    "notify.daemonOutdated.title": {
+        "message": "A NetBird szolgáltatás elavult"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Frissítsd a NetBird szolgáltatást az alkalmazás használatához."
+    },
     "notify.update.title": {
         "message": "NetBird frissítés elérhető"
     },

client/ui/i18n/locales/it/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "Esci da NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "Il servizio NetBird è obsoleto"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Aggiorna il servizio NetBird per usare questa app."
+    },
     "notify.update.title": {
         "message": "Aggiornamento NetBird disponibile"
     },

client/ui/i18n/locales/pt/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "Sair do NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "O serviço NetBird está desatualizado"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Atualize o serviço NetBird para usar este aplicativo."
+    },
     "notify.update.title": {
         "message": "Atualização do NetBird disponível"
     },

client/ui/i18n/locales/ru/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "Выйти из NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "Служба NetBird устарела"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "Обновите службу NetBird, чтобы использовать это приложение."
+    },
     "notify.update.title": {
         "message": "Доступно обновление NetBird"
     },

client/ui/i18n/locales/zh-CN/common.json

@@ -107,6 +107,12 @@
     "tray.menu.quit": {
         "message": "退出 NetBird"
     },
+    "notify.daemonOutdated.title": {
+        "message": "NetBird 服务版本过旧"
+    },
+    "notify.daemonOutdated.body": {
+        "message": "请更新 NetBird 服务以使用此应用。"
+    },
     "notify.update.title": {
         "message": "NetBird 有可用更新"
     },

client/ui/main.go

@@ -64,6 +64,7 @@ type registeredServices struct {
 	update          *services.Update
 	daemonFeed      *services.DaemonFeed
 	notifier        *notifications.NotificationService
+	compat          *services.Compat
 	profileSwitcher *services.ProfileSwitcher
 	bundle          *i18n.Bundle
 	prefStore       *preferences.Store
@@ -103,6 +104,7 @@ func main() {
 	update := services.NewUpdate(conn, updaterHolder)
 	daemonFeed := services.NewDaemonFeed(conn, app.Event, updaterHolder, debugLog)
 	notifier := notifications.New()
+	compat := services.NewCompat(conn)
 	// macOS shows no toast until permission is requested. Run it after
 	// ApplicationStarted so the notifier's Startup has initialised the
 	// notification-center delegate. No-op on Linux/Windows (stubs report
@@ -132,6 +134,7 @@ func main() {
 		update:          update,
 		daemonFeed:      daemonFeed,
 		notifier:        notifier,
+		compat:          compat,
 		profileSwitcher: profileSwitcher,
 		bundle:          bundle,
 		prefStore:       prefStore,
@@ -190,6 +193,10 @@ func main() {
 	// Mint). ApplicationStarted fires after the startup loop, so the bus is up.
 	app.Event.OnApplicationEvent(events.Common.ApplicationStarted, func(*application.ApplicationEvent) {
 		daemonFeed.Watch(context.Background())
+		// Probe daemon compatibility once the notifier bus is up; an outdated
+		// daemon may keep the main window from showing, so the OS toast is the
+		// only reliable signal the user gets.
+		go notifyIfDaemonOutdated(compat, notifier, localizer)
 	})
 
 	if err := app.Run(); err != nil {
@@ -322,6 +329,7 @@ func registerServices(app *application.App, conn *Conn, s registeredServices) {
 	app.RegisterService(application.NewService(services.NewAutostart(app.Autostart)))
 	app.RegisterService(application.NewService(services.NewVersion()))
 	app.RegisterService(application.NewService(services.NewUILog()))
+	app.RegisterService(application.NewService(s.compat))
 }
 
 // newMainWindow creates the hidden main window, sized to the user's last view

client/ui/services/compat.go

@@ -0,0 +1,40 @@
+//go:build !android && !ios && !freebsd && !js
+
+package services
+
+import (
+	"context"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	"github.com/netbirdio/netbird/client/proto"
+)
+
+// Compat answers whether the running daemon is new enough to drive this UI.
+type Compat struct {
+	conn DaemonConn
+}
+
+func NewCompat(conn DaemonConn) *Compat {
+	return &Compat{conn: conn}
+}
+
+// DaemonReady probes the WailsUIReady RPC once. A true result means the daemon
+// implements it and is compatible. An Unimplemented response means the daemon
+// predates this UI and is too old; the caller should surface an upgrade prompt.
+// Any other error (daemon not running, transport failure) is returned so the
+// frontend can tell "outdated" apart from "not reachable".
+func (c *Compat) DaemonReady(ctx context.Context) (bool, error) {
+	client, err := c.conn.Client()
+	if err != nil {
+		return false, err
+	}
+	if _, err := client.WailsUIReady(ctx, &proto.WailsUIReadyRequest{}); err != nil {
+		if st, ok := status.FromError(err); ok && st.Code() == codes.Unimplemented {
+			return false, nil
+		}
+		return false, err
+	}
+	return true, nil
+}

client/ui/tray_notify.go

@@ -3,10 +3,16 @@
 package main
 
 import (
+	"context"
+
 	log "github.com/sirupsen/logrus"
 	"github.com/wailsapp/wails/v3/pkg/services/notifications"
+
+	"github.com/netbirdio/netbird/client/ui/services"
 )
 
+const notifyIDDaemonOutdated = "netbird-daemon-outdated"
+
 // sendFn fits both NotificationService.SendNotification and SendNotificationWithActions.
 type sendFn func(notifications.NotificationOptions) error
 
@@ -31,3 +37,22 @@ func safeSendNotification(send sendFn, what string, opts notifications.Notificat
 	}
 	return nil
 }
+
+// notifyIfDaemonOutdated probes the daemon once and fires an OS toast when it
+// is reachable but too old for this UI. A probe error means the daemon isn't
+// reachable (not outdated), so it is left to the normal connection flow.
+func notifyIfDaemonOutdated(compat *services.Compat, notifier *notifications.NotificationService, loc *Localizer) {
+	ready, err := compat.DaemonReady(context.Background())
+	if err != nil {
+		log.Debugf("daemon compatibility probe: %v", err)
+		return
+	}
+	if ready {
+		return
+	}
+	_ = safeSendNotification(notifier.SendNotification, "daemon-outdated", notifications.NotificationOptions{
+		ID:    notifyIDDaemonOutdated,
+		Title: loc.T("notify.daemonOutdated.title"),
+		Body:  loc.T("notify.daemonOutdated.body"),
+	})
+}