fixed the ensure one instanve only logic.

requirements.txt

@@ -2,3 +2,4 @@ keyboard==0.13.5
 pyperclip==1.9.0
 pystray==0.19.5
 Pillow==12.0.0
+psutil>=5.8.0

src/main.pyw

@@ -179,6 +179,11 @@ def cleanup_lock():
 
 def is_process_running(pid):
     """Check if a process with the given PID is still running."""
+    try:
+        import psutil
+        return psutil.pid_exists(pid)
+    except:
+        # Fallback if psutil is not available
         try:
             os.kill(pid, 0)  # Signal 0 doesn't kill, just checks if process exists
             return True
@@ -189,6 +194,12 @@ def ensure_single_instance():
     """Ensure only one instance of the app is running. Exit if another instance exists."""
     if os.path.exists(LOCK_FILE):
         try:
+            # Read the PID from the lock file
+            with open(LOCK_FILE, 'r') as f:
+                old_pid = int(f.read().strip())
+            
+            # Check if the process with that PID is still running
+            if is_process_running(old_pid):
                 # Another instance is running, show message and exit
                 import ctypes
                 ctypes.windll.user32.MessageBoxW(
@@ -198,8 +209,17 @@ def ensure_single_instance():
                     0x40  # MB_ICONINFORMATION
                 )
                 os._exit(1)
+            else:
+                # Process is not running, remove the stale lock file
+                try:
+                    os.remove(LOCK_FILE)
+                except OSError:
+                    pass
         except (ValueError, OSError):
-            # Lock file exists but is invalid or unreadable, clean it up
+            # Lock file exists but is invalid or unreadable, clean it up and continue
+            try:
+                os.remove(LOCK_FILE)
+            except OSError:
                 pass
     
     # Create lock file with our PID