Fix WebSocket upgrade handling to preserve Next.js HMR handlers

- Save existing upgrade listeners before adding our own
- Call existing listeners for non-matching paths to allow Next.js HMR
- Only handle /ws/script-execution ourselves
- This ensures Next.js can handle its own WebSocket upgrades for HMR

server.js

@@ -79,17 +79,28 @@ class ScriptExecutionHandler {
    * @param {import('http').Server} server
    */
   constructor(server) {
-    // Create WebSocketServer attached to server with path filter
-    // The path option should ensure it only handles /ws/script-execution
+    // Create WebSocketServer without attaching to server
+    // We'll handle upgrades manually to avoid interfering with Next.js HMR
     this.wss = new WebSocketServer({ 
-      server,
-      path: '/ws/script-execution'
+      noServer: true
     });
     this.activeExecutions = new Map();
     this.db = getDatabase();
     this.setupWebSocket();
   }
   
+  /**
+   * Handle WebSocket upgrade for our endpoint
+   * @param {import('http').IncomingMessage} request
+   * @param {import('net').Socket} socket
+   * @param {Buffer} head
+   */
+  handleUpgrade(request, socket, head) {
+    this.wss.handleUpgrade(request, socket, head, (ws) => {
+      this.wss.emit('connection', ws, request);
+    });
+  }
+
   /**
    * Parse Container ID from terminal output
    * @param {string} output - Terminal output to parse
@@ -1187,6 +1198,33 @@ app.prepare().then(() => {
 
   // Create WebSocket handlers
   const scriptHandler = new ScriptExecutionHandler(httpServer);
+  
+  // Handle WebSocket upgrades manually to avoid interfering with Next.js HMR
+  // We need to preserve Next.js's upgrade handlers and call them for non-matching paths
+  // Save any existing upgrade listeners (Next.js might have set them up)
+  const existingUpgradeListeners = httpServer.listeners('upgrade').slice();
+  httpServer.removeAllListeners('upgrade');
+  
+  // Add our upgrade handler that routes based on path
+  httpServer.on('upgrade', (request, socket, head) => {
+    const parsedUrl = parse(request.url || '', true);
+    const { pathname } = parsedUrl;
+    
+    if (pathname === '/ws/script-execution') {
+      // Handle our custom WebSocket endpoint
+      scriptHandler.handleUpgrade(request, socket, head);
+    } else {
+      // For all other paths (including Next.js HMR), call existing listeners
+      // This allows Next.js to handle its own WebSocket upgrades
+      for (const listener of existingUpgradeListeners) {
+        try {
+          listener.call(httpServer, request, socket, head);
+        } catch (err) {
+          console.error('Error in upgrade listener:', err);
+        }
+      }
+    }
+  });
   // Note: TerminalHandler removed as it's not being used by the current application
 
   httpServer