diff --git a/daemon/src/main.rs b/daemon/src/main.rs
index 0dd4291..f732485 100644
--- a/daemon/src/main.rs
+++ b/daemon/src/main.rs
@@ -505,6 +505,15 @@ fn recover_display_env() {
 }
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Ensure single instance to avoid duplicate daemon processes
+    let _listener = match std::os::unix::net::UnixListener::bind("\0vietc-daemon-lock") {
+        Ok(l) => l,
+        Err(_) => {
+            eprintln!("[vietc] Another instance is already running. Exiting.");
+            std::process::exit(0);
+        }
+    };
+
     recover_display_env();
     let config_path = config::find_config_path();
     let config = Config::load()?;
diff --git a/ui/src/main.rs b/ui/src/main.rs
index 3fb5211..6152764 100644
--- a/ui/src/main.rs
+++ b/ui/src/main.rs
@@ -180,6 +180,15 @@ fn config_path() -> PathBuf {
 }
 
 fn main() {
+    // Ensure single instance to avoid duplicate tray icons
+    let _listener = match std::os::unix::net::UnixListener::bind("\0vietc-tray-lock") {
+        Ok(l) => l,
+        Err(_) => {
+            eprintln!("[vietc-tray] Another instance is already running. Exiting.");
+            std::process::exit(0);
+        }
+    };
+
     eprintln!("[vietc-tray] Starting");
 
     // Start daemon (with password prompt if first launch)