diff --git a/ostp-client/src/runner.rs b/ostp-client/src/runner.rs
index b464527..db40484 100644
--- a/ostp-client/src/runner.rs
+++ b/ostp-client/src/runner.rs
@@ -32,7 +32,7 @@ fn hide_console() {
 }
 
 #[cfg(target_os = "windows")]
-fn is_admin() -> bool {
+pub fn is_admin() -> bool {
     std::process::Command::new("net")
         .arg("session")
         .stdout(std::process::Stdio::null())
@@ -100,6 +100,12 @@ fn relaunch_as_admin() -> Result<()> {
 }
 
 pub async fn run_client(config: crate::config::ClientConfig) -> Result<()> {
+    #[cfg(target_os = "windows")]
+    if config.mode == "tun" && !is_admin() {
+        println!("[ostp-client] TUN mode requires Administrator privileges. Relaunching executable as Admin...");
+        relaunch_as_admin()?;
+    }
+
     let bg = std::env::args().any(|a| a == "--bg");
 
     if bg {
@@ -130,8 +136,7 @@ pub async fn run_client_core(
 ) -> Result<()> {
     #[cfg(target_os = "windows")]
     if config.mode == "tun" && !is_admin() {
-        println!("[ostp-client] TUN mode requires Administrator privileges. Relaunching executable as Admin...");
-        relaunch_as_admin()?;
+        return Err(anyhow::anyhow!("Administrator privileges are required to initialize TUN mode. Please run the application as Administrator."));
     }
 
     if config.mode == "tun" && !config.exclusions.processes.is_empty() {
diff --git a/ostp-gui/src-tauri/src/lib.rs b/ostp-gui/src-tauri/src/lib.rs
index d7b7b5b..e3db7a6 100644
--- a/ostp-gui/src-tauri/src/lib.rs
+++ b/ostp-gui/src-tauri/src/lib.rs
@@ -234,6 +234,11 @@ async fn start_tunnel(state: tauri::State<'_, AppState>) -> Result<bool, String>
         dns_server: client_cfg.tun.as_ref().and_then(|t| t.dns.clone()),
     };
 
+    #[cfg(target_os = "windows")]
+    if mapped_config.mode == "tun" && !ostp_client::runner::is_admin() {
+        return Err("Administrator privileges are required to initialize TUN mode. Please run the application as Administrator.".to_string());
+    }
+
     let metrics = Arc::new(BridgeMetrics {
         bytes_sent: portable_atomic::AtomicU64::new(0),
         bytes_recv: portable_atomic::AtomicU64::new(0),
diff --git a/ostp-gui/src/main.js b/ostp-gui/src/main.js
index 6e253bc..9de8dd2 100644
--- a/ostp-gui/src/main.js
+++ b/ostp-gui/src/main.js
@@ -118,7 +118,7 @@ async function handleToggleConnect() {
         setUIState('disconnected');
       }
     } catch (err) {
-      console.error(err);
+      alert('Error starting tunnel: ' + err);
       setUIState('disconnected');
     }
   } else {