diff --git a/build-output/minicloud-sync.exe b/build-output/minicloud-sync.exe
new file mode 100755
index 0000000..ea44653
Binary files /dev/null and b/build-output/minicloud-sync.exe differ
diff --git a/build-output/nsis/MiniCloud Sync_0.1.0_x64-setup.exe b/build-output/nsis/MiniCloud Sync_0.1.0_x64-setup.exe
new file mode 100644
index 0000000..8d7f41b
Binary files /dev/null and b/build-output/nsis/MiniCloud Sync_0.1.0_x64-setup.exe differ
diff --git a/clients/desktop/src-tauri/src/lib.rs b/clients/desktop/src-tauri/src/lib.rs
index 0515f1e..be19031 100644
--- a/clients/desktop/src-tauri/src/lib.rs
+++ b/clients/desktop/src-tauri/src/lib.rs
@@ -1,17 +1,26 @@
 mod sync;
 
 use std::path::PathBuf;
-use std::sync::Mutex;
-use tauri::State;
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+use tauri::{
+    menu::{Menu, MenuItem},
+    tray::TrayIconBuilder,
+    AppHandle, Emitter, Manager, State,
+};
 
 use sync::api::MiniCloudApi;
 use sync::engine::SyncEngine;
+use sync::watcher::{FileWatcher, ChangeKind};
 
 struct AppState {
     api: Mutex<Option<MiniCloudApi>>,
     sync_engine: Mutex<Option<SyncEngine>>,
     sync_dir: Mutex<Option<PathBuf>>,
     username: Mutex<Option<String>>,
+    watcher: Mutex<Option<FileWatcher>>,
+    sync_running: Arc<Mutex<bool>>,
+    locked_files: Mutex<Vec<i64>>, // file IDs we have locked
 }
 
 #[tauri::command]
@@ -44,28 +53,36 @@ fn set_sync_dir(state: State<'_, AppState>, path: String) -> Result<String, Stri
 }
 
 #[tauri::command]
-async fn start_sync(state: State<'_, AppState>) -> Result<Vec<String>, String> {
+async fn start_sync(app: AppHandle, state: State<'_, AppState>) -> Result<Vec<String>, String> {
     let api = state.api.lock().unwrap().clone()
         .ok_or("Nicht eingeloggt")?;
     let sync_dir = state.sync_dir.lock().unwrap().clone()
         .ok_or("Kein Sync-Ordner gesetzt")?;
 
-    let mut engine = SyncEngine::new(sync_dir, api);
+    // Full sync
+    let mut engine = SyncEngine::new(sync_dir.clone(), api.clone());
     let log = engine.full_sync().await?;
 
     *state.sync_engine.lock().unwrap() = Some(engine);
+
+    // Start file watcher
+    let watcher = FileWatcher::new(&sync_dir)?;
+    *state.watcher.lock().unwrap() = Some(watcher);
+
+    // Start background auto-sync + watcher processing
+    start_background_sync(app, state.sync_running.clone(), api, sync_dir);
+
+    let _ = app.emit("sync-status", "synced");
     Ok(log)
 }
 
 #[tauri::command]
 async fn delta_sync(state: State<'_, AppState>) -> Result<Vec<String>, String> {
-    // Extract engine from state, dropping the MutexGuard before .await
     let mut engine = {
         let mut guard = state.sync_engine.lock().unwrap();
         guard.take().ok_or("Sync nicht gestartet")?
     };
     let result = engine.delta_sync().await;
-    // Put engine back
     *state.sync_engine.lock().unwrap() = Some(engine);
     result
 }
@@ -75,11 +92,15 @@ async fn get_status(state: State<'_, AppState>) -> Result<serde_json::Value, Str
     let logged_in = state.api.lock().unwrap().is_some();
     let sync_dir = state.sync_dir.lock().unwrap().clone();
     let username = state.username.lock().unwrap().clone();
+    let syncing = *state.sync_running.lock().unwrap();
+    let locked_count = state.locked_files.lock().unwrap().len();
 
     Ok(serde_json::json!({
         "logged_in": logged_in,
         "username": username,
         "sync_dir": sync_dir.map(|p| p.to_string_lossy().to_string()),
+        "syncing": syncing,
+        "locked_files": locked_count,
     }))
 }
 
@@ -91,15 +112,143 @@ async fn get_file_tree(state: State<'_, AppState>) -> Result<serde_json::Value,
     Ok(serde_json::to_value(tree).map_err(|e| e.to_string())?)
 }
 
+#[tauri::command]
+async fn lock_file_cmd(state: State<'_, AppState>, file_id: i64) -> Result<String, String> {
+    let api = state.api.lock().unwrap().clone().ok_or("Nicht eingeloggt")?;
+    api.lock_file(file_id, "Desktop Sync Client").await?;
+    state.locked_files.lock().unwrap().push(file_id);
+    Ok("Datei gesperrt".to_string())
+}
+
+#[tauri::command]
+async fn unlock_file_cmd(state: State<'_, AppState>, file_id: i64) -> Result<String, String> {
+    let api = state.api.lock().unwrap().clone().ok_or("Nicht eingeloggt")?;
+    api.unlock_file(file_id).await?;
+    state.locked_files.lock().unwrap().retain(|&id| id != file_id);
+    Ok("Datei entsperrt".to_string())
+}
+
+/// Background sync: auto-sync every 30s + process file watcher events + heartbeat for locks
+fn start_background_sync(
+    app: AppHandle,
+    sync_running: Arc<Mutex<bool>>,
+    api: MiniCloudApi,
+    sync_dir: PathBuf,
+) {
+    // Auto-sync thread (delta sync every 30 seconds)
+    let app_sync = app.clone();
+    let api_sync = api.clone();
+    let sync_dir_clone = sync_dir.clone();
+    let running = sync_running.clone();
+
+    std::thread::spawn(move || {
+        let rt = tokio::runtime::Runtime::new().unwrap();
+        let mut engine = SyncEngine::new(sync_dir_clone, api_sync);
+
+        loop {
+            std::thread::sleep(Duration::from_secs(30));
+
+            *running.lock().unwrap() = true;
+            let _ = app_sync.emit("sync-status", "syncing");
+
+            match rt.block_on(engine.delta_sync()) {
+                Ok(log) => {
+                    if !log.is_empty() {
+                        let _ = app_sync.emit("sync-log", log);
+                    }
+                }
+                Err(e) => {
+                    let _ = app_sync.emit("sync-error", e);
+                }
+            }
+
+            *running.lock().unwrap() = false;
+            let _ = app_sync.emit("sync-status", "synced");
+        }
+    });
+
+    // Heartbeat thread (every 60 seconds for locked files)
+    let app_hb = app.clone();
+    let api_hb = api.clone();
+    std::thread::spawn(move || {
+        let rt = tokio::runtime::Runtime::new().unwrap();
+        loop {
+            std::thread::sleep(Duration::from_secs(60));
+
+            let state = app_hb.state::<AppState>();
+            let locked = state.locked_files.lock().unwrap().clone();
+
+            for file_id in locked {
+                let _ = rt.block_on(api_hb.heartbeat(file_id));
+            }
+        }
+    });
+
+    // File watcher processing thread
+    let app_watcher = app.clone();
+    std::thread::spawn(move || {
+        loop {
+            std::thread::sleep(Duration::from_secs(2));
+
+            let state = app_watcher.state::<AppState>();
+            let watcher_guard = state.watcher.lock().unwrap();
+            if let Some(watcher) = watcher_guard.as_ref() {
+                while let Ok(change) = watcher.receiver.try_recv() {
+                    let rel_path = change.path.strip_prefix(&sync_dir)
+                        .unwrap_or(&change.path)
+                        .to_string_lossy()
+                        .to_string();
+
+                    let msg = match change.kind {
+                        ChangeKind::Created => format!("Neu: {}", rel_path),
+                        ChangeKind::Modified => format!("Geaendert: {}", rel_path),
+                        ChangeKind::Deleted => format!("Geloescht: {}", rel_path),
+                    };
+                    let _ = app_watcher.emit("file-change", msg);
+                }
+            }
+        }
+    });
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_opener::init())
+        .plugin(tauri_plugin_notification::init())
         .manage(AppState {
             api: Mutex::new(None),
             sync_engine: Mutex::new(None),
             sync_dir: Mutex::new(None),
             username: Mutex::new(None),
+            watcher: Mutex::new(None),
+            sync_running: Arc::new(Mutex::new(false)),
+            locked_files: Mutex::new(Vec::new()),
+        })
+        .setup(|app| {
+            // System Tray
+            let quit = MenuItem::with_id(app, "quit", "Beenden", true, None::<&str>)?;
+            let show = MenuItem::with_id(app, "show", "Oeffnen", true, None::<&str>)?;
+            let menu = Menu::with_items(app, &[&show, &quit])?;
+
+            TrayIconBuilder::new()
+                .tooltip("Mini-Cloud Sync")
+                .menu(&menu)
+                .on_menu_event(|app, event| {
+                    match event.id.as_ref() {
+                        "quit" => std::process::exit(0),
+                        "show" => {
+                            if let Some(window) = app.get_webview_window("main") {
+                                let _ = window.show();
+                                let _ = window.set_focus();
+                            }
+                        }
+                        _ => {}
+                    }
+                })
+                .build(app)?;
+
+            Ok(())
         })
         .invoke_handler(tauri::generate_handler![
             login,
@@ -108,6 +257,8 @@ pub fn run() {
             delta_sync,
             get_status,
             get_file_tree,
+            lock_file_cmd,
+            unlock_file_cmd,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");
diff --git a/clients/desktop/src/App.vue b/clients/desktop/src/App.vue
index 9bb2812..3176735 100644
--- a/clients/desktop/src/App.vue
+++ b/clients/desktop/src/App.vue
@@ -1,6 +1,7 @@
 <script setup>
-import { ref, onMounted } from "vue";
+import { ref, onMounted, onUnmounted } from "vue";
 import { invoke } from "@tauri-apps/api/core";
+import { listen } from "@tauri-apps/api/event";
 
 const screen = ref("login"); // login | main
 const serverUrl = ref("https://");
@@ -12,9 +13,16 @@ const loginLoading = ref(false);
 const syncDir = ref("");
 const syncLog = ref([]);
 const syncing = ref(false);
+const syncStatus = ref("Nicht verbunden");
 const userInfo = ref(null);
 const fileTree = ref([]);
-const statusMsg = ref("Nicht verbunden");
+const fileChanges = ref([]);
+const autoSyncActive = ref(false);
+
+let unlistenStatus = null;
+let unlistenLog = null;
+let unlistenError = null;
+let unlistenFileChange = null;
 
 async function handleLogin() {
   loginError.value = "";
@@ -27,10 +35,12 @@ async function handleLogin() {
     });
     userInfo.value = result;
     screen.value = "main";
-    statusMsg.value = `Verbunden als ${result.username}`;
+    syncStatus.value = `Verbunden als ${result.username}`;
+
+    // Default sync dir
+    const home = navigator.platform.includes("Win") ? "C:\\Users\\" + result.username : "/home/" + result.username;
+    syncDir.value = `${home}/MiniCloud`;
 
-    // Set default sync dir
-    syncDir.value = `${await getDefaultSyncDir()}/MiniCloud`;
     await loadFileTree();
   } catch (err) {
     loginError.value = String(err);
@@ -39,36 +49,18 @@ async function handleLogin() {
   }
 }
 
-async function getDefaultSyncDir() {
-  // Use home directory
-  try {
-    const home = await invoke("get_status");
-    return home.sync_dir || (navigator.platform.includes("Win") ? "C:\\Users" : "/home");
-  } catch {
-    return "/home";
-  }
-}
-
-async function setSyncFolder() {
-  try {
-    await invoke("set_sync_dir", { path: syncDir.value });
-    statusMsg.value = `Sync-Ordner: ${syncDir.value}`;
-  } catch (err) {
-    statusMsg.value = `Fehler: ${err}`;
-  }
-}
-
 async function runSync() {
   syncing.value = true;
-  statusMsg.value = "Synchronisiere...";
+  syncStatus.value = "Erster Sync...";
   try {
     await invoke("set_sync_dir", { path: syncDir.value });
     const log = await invoke("start_sync");
-    syncLog.value = log;
-    statusMsg.value = `Sync fertig: ${log.length} Aktionen`;
+    syncLog.value = [...log, ...syncLog.value].slice(0, 100);
+    syncStatus.value = "Synchronisiert";
+    autoSyncActive.value = true;
     await loadFileTree();
   } catch (err) {
-    statusMsg.value = `Sync-Fehler: ${err}`;
+    syncStatus.value = `Fehler: ${err}`;
   } finally {
     syncing.value = false;
   }
@@ -90,6 +82,46 @@ function formatSize(bytes) {
   while (size >= 1024 && i < units.length - 1) { size /= 1024; i++; }
   return `${size.toFixed(i > 0 ? 1 : 0)} ${units[i]}`;
 }
+
+function timestamp() {
+  return new Date().toLocaleTimeString("de-DE", { hour: "2-digit", minute: "2-digit", second: "2-digit" });
+}
+
+onMounted(async () => {
+  // Listen for sync events from Rust backend
+  unlistenStatus = await listen("sync-status", (event) => {
+    if (event.payload === "syncing") {
+      syncStatus.value = "Synchronisiere...";
+      syncing.value = true;
+    } else if (event.payload === "synced") {
+      syncStatus.value = "Synchronisiert";
+      syncing.value = false;
+      loadFileTree();
+    }
+  });
+
+  unlistenLog = await listen("sync-log", (event) => {
+    const entries = event.payload.map(msg => `[${timestamp()}] ${msg}`);
+    syncLog.value = [...entries, ...syncLog.value].slice(0, 200);
+  });
+
+  unlistenError = await listen("sync-error", (event) => {
+    syncStatus.value = `Fehler: ${event.payload}`;
+    syncLog.value = [`[${timestamp()}] FEHLER: ${event.payload}`, ...syncLog.value].slice(0, 200);
+    syncing.value = false;
+  });
+
+  unlistenFileChange = await listen("file-change", (event) => {
+    fileChanges.value = [`[${timestamp()}] ${event.payload}`, ...fileChanges.value].slice(0, 50);
+  });
+});
+
+onUnmounted(() => {
+  unlistenStatus?.();
+  unlistenLog?.();
+  unlistenError?.();
+  unlistenFileChange?.();
+});
 </script>
 
 <template>
@@ -127,8 +159,11 @@ function formatSize(bytes) {
     <div class="toolbar">
       <div class="toolbar-left">
         <span class="logo-small">☁</span>
-        <strong>Mini-Cloud</strong>
-        <span class="status-badge">{{ statusMsg }}</span>
+        <strong>Mini-Cloud Sync</strong>
+        <span class="status-badge" :class="{ syncing: syncing, error: syncStatus.startsWith('Fehler') }">
+          <span v-if="syncing" class="spin">⟳</span>
+          {{ syncStatus }}
+        </span>
       </div>
       <div class="toolbar-right">
         <span class="user-info">{{ userInfo?.username }}</span>
@@ -140,29 +175,49 @@ function formatSize(bytes) {
       <div class="section">
         <h3>Sync-Ordner</h3>
         <div class="sync-row">
-          <input v-model="syncDir" class="sync-input" />
+          <input v-model="syncDir" class="sync-input" :disabled="autoSyncActive" />
           <button @click="runSync" :disabled="syncing" class="btn-primary">
-            {{ syncing ? "Synchronisiere..." : "Jetzt synchronisieren" }}
+            {{ autoSyncActive ? "⟳ Auto-Sync aktiv" : (syncing ? "Synchronisiere..." : "Sync starten") }}
           </button>
         </div>
+        <div v-if="autoSyncActive" class="auto-sync-info">
+          Auto-Sync alle 30 Sekunden aktiv. Datei-Watcher ueberwacht lokale Aenderungen.
+        </div>
       </div>
 
       <!-- File Tree -->
       <div class="section">
-        <h3>Server-Dateien</h3>
+        <div class="section-header">
+          <h3>Server-Dateien</h3>
+          <button v-if="autoSyncActive" @click="loadFileTree" class="btn-small">Aktualisieren</button>
+        </div>
         <div class="file-tree">
-          <div v-for="entry in fileTree" :key="entry.id" class="tree-item">
-            <span class="tree-icon">{{ entry.is_folder ? "📁" : "📄" }}</span>
-            <span class="tree-name">{{ entry.name }}</span>
-            <span v-if="entry.locked" class="tree-lock" :title="'Gesperrt von ' + entry.locked_by">
-              🔒 {{ entry.locked_by }}
-            </span>
-            <span v-if="!entry.is_folder" class="tree-size">{{ formatSize(entry.size) }}</span>
-          </div>
+          <template v-for="entry in fileTree" :key="entry.id">
+            <div class="tree-item">
+              <span class="tree-icon">{{ entry.is_folder ? "📁" : "📄" }}</span>
+              <span class="tree-name">{{ entry.name }}</span>
+              <span v-if="entry.locked" class="tree-lock">🔒 {{ entry.locked_by }}</span>
+              <span v-if="!entry.is_folder" class="tree-size">{{ formatSize(entry.size) }}</span>
+            </div>
+            <div v-if="entry.children" v-for="child in entry.children" :key="child.id" class="tree-item indent">
+              <span class="tree-icon">{{ child.is_folder ? "📁" : "📄" }}</span>
+              <span class="tree-name">{{ child.name }}</span>
+              <span v-if="child.locked" class="tree-lock">🔒 {{ child.locked_by }}</span>
+              <span v-if="!child.is_folder" class="tree-size">{{ formatSize(child.size) }}</span>
+            </div>
+          </template>
           <div v-if="!fileTree.length" class="empty">Keine Dateien</div>
         </div>
       </div>
 
+      <!-- File Changes (Watcher) -->
+      <div v-if="fileChanges.length" class="section">
+        <h3>Lokale Aenderungen</h3>
+        <div class="log-list">
+          <div v-for="(msg, i) in fileChanges" :key="i" class="log-item change">{{ msg }}</div>
+        </div>
+      </div>
+
       <!-- Sync Log -->
       <div v-if="syncLog.length" class="section">
         <h3>Sync-Protokoll</h3>
@@ -180,9 +235,7 @@ body {
   font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
   font-size: 14px; color: #1a1a1a; background: #f0f2f5;
 }
-.login-screen {
-  height: 100vh; display: flex; align-items: center; justify-content: center;
-}
+.login-screen { height: 100vh; display: flex; align-items: center; justify-content: center; }
 .login-card {
   background: white; border-radius: 12px; padding: 2rem; width: 360px;
   box-shadow: 0 2px 12px rgba(0,0,0,0.1);
@@ -200,11 +253,17 @@ body {
 .field input:focus { border-color: #4a90d9; outline: none; background: white; }
 .error { color: #e53e3e; font-size: 0.85rem; margin-bottom: 0.75rem; }
 .btn-primary {
-  width: 100%; padding: 0.6rem; background: #4a90d9; color: white;
+  padding: 0.6rem 1rem; background: #4a90d9; color: white;
   border: none; border-radius: 6px; font-size: 0.9rem; cursor: pointer; font-weight: 500;
+  white-space: nowrap;
 }
 .btn-primary:hover { background: #3a7bc8; }
 .btn-primary:disabled { opacity: 0.6; cursor: not-allowed; }
+.btn-small {
+  padding: 0.25rem 0.5rem; background: #e8e8e8; border: none; border-radius: 4px;
+  font-size: 0.8rem; cursor: pointer;
+}
+.btn-small:hover { background: #ddd; }
 
 .main-screen { height: 100vh; display: flex; flex-direction: column; }
 .toolbar {
@@ -213,32 +272,50 @@ body {
 }
 .toolbar-left { display: flex; align-items: center; gap: 0.5rem; }
 .logo-small { font-size: 1.2rem; }
-.status-badge { font-size: 0.8rem; color: #666; background: #f0f0f0; padding: 0.2rem 0.5rem; border-radius: 4px; }
+.status-badge {
+  font-size: 0.8rem; padding: 0.2rem 0.5rem; border-radius: 4px;
+  background: #e8f5e9; color: #2e7d32;
+}
+.status-badge.syncing { background: #fff3e0; color: #e65100; }
+.status-badge.error { background: #ffebee; color: #c62828; }
+.spin { display: inline-block; animation: spin 1s linear infinite; }
+@keyframes spin { from { transform: rotate(0deg); } to { transform: rotate(360deg); } }
 .user-info { font-size: 0.85rem; color: #666; }
 .content { flex: 1; overflow-y: auto; padding: 1rem; }
-.section { background: white; border-radius: 8px; padding: 1rem; margin-bottom: 1rem; }
-.section h3 { margin-bottom: 0.75rem; font-size: 0.95rem; }
+.section { background: white; border-radius: 8px; padding: 1rem; margin-bottom: 0.75rem; }
+.section h3 { margin-bottom: 0.5rem; font-size: 0.95rem; }
+.section-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 0.5rem; }
+.section-header h3 { margin: 0; }
 .sync-row { display: flex; gap: 0.5rem; }
-.sync-input { flex: 1; padding: 0.5rem; border: 1px solid #ddd; border-radius: 6px; font-size: 0.85rem; }
-.file-tree { max-height: 300px; overflow-y: auto; }
+.sync-input {
+  flex: 1; padding: 0.5rem; border: 1px solid #ddd; border-radius: 6px; font-size: 0.85rem;
+}
+.sync-input:disabled { background: #f5f5f5; color: #999; }
+.auto-sync-info { margin-top: 0.5rem; font-size: 0.8rem; color: #2e7d32; }
+.file-tree { max-height: 250px; overflow-y: auto; }
 .tree-item {
   display: flex; align-items: center; gap: 0.5rem;
-  padding: 0.375rem 0; border-bottom: 1px solid #f5f5f5; font-size: 0.85rem;
+  padding: 0.3rem 0; border-bottom: 1px solid #f5f5f5; font-size: 0.85rem;
 }
+.tree-item.indent { padding-left: 1.5rem; }
 .tree-icon { flex-shrink: 0; }
-.tree-name { flex: 1; }
-.tree-lock { font-size: 0.75rem; color: #e67e22; }
-.tree-size { font-size: 0.75rem; color: #999; }
+.tree-name { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.tree-lock { font-size: 0.75rem; color: #e67e22; flex-shrink: 0; }
+.tree-size { font-size: 0.75rem; color: #999; flex-shrink: 0; }
 .empty { text-align: center; color: #999; padding: 1rem; }
-.log-list { max-height: 200px; overflow-y: auto; font-family: monospace; font-size: 0.8rem; }
-.log-item { padding: 0.25rem 0; border-bottom: 1px solid #f5f5f5; }
+.log-list { max-height: 150px; overflow-y: auto; font-family: monospace; font-size: 0.78rem; }
+.log-item { padding: 0.2rem 0; border-bottom: 1px solid #f8f8f8; color: #555; }
+.log-item.change { color: #1565c0; }
 
 @media (prefers-color-scheme: dark) {
   body { color: #e0e0e0; background: #1a1a1a; }
   .login-card, .section { background: #2a2a2a; }
   .toolbar { background: #2a2a2a; border-color: #3a3a3a; }
   .field input, .sync-input { background: #333; border-color: #444; color: #e0e0e0; }
-  .status-badge { background: #3a3a3a; color: #aaa; }
+  .status-badge { background: #1b5e20; color: #a5d6a7; }
+  .status-badge.syncing { background: #e65100; color: #ffcc80; }
   .tree-item { border-color: #333; }
+  .log-item { border-color: #333; color: #aaa; }
+  .log-item.change { color: #64b5f6; }
 }
 </style>