Fix devserver mode in combination with websocket/http merge

Author: Patrick Hagemeister

demo/bin/demo.js

@@ -525,7 +525,34 @@ if (DEV_MODE) {
       strictPort: true,
     },
   });
+  
   await vite.listen();
+  
+  // Attach WebSocket handler AFTER Vite has fully initialized
+  // Use prependListener (not prependOnceListener) so it runs for every request
+  // This ensures our handler runs BEFORE Vite's handlers
+  if (vite.httpServer) {
+    vite.httpServer.prependListener('upgrade', (req, socket, head) => {
+      const pathname = req.url?.split('?')[0] || req.url || '';
+      
+      // ONLY handle /ws - everything else passes through unchanged to Vite
+      if (pathname === '/ws') {
+        if (!socket.destroyed && !socket.readableEnded) {
+          wss.handleUpgrade(req, socket, head, (ws) => {
+            wss.emit('connection', ws, req);
+          });
+        }
+        // Stop here - we handled it, socket is consumed
+        // Don't call other listeners
+        return;
+      }
+      
+      // For non-/ws paths, explicitly do nothing and let the event propagate
+      // The key is: don't return, don't touch the socket, just let it pass through
+      // Vite's handlers (which were added before ours via prependListener) will process it
+    });
+  }
+  
   printBanner(`http://localhost:${HTTP_PORT}/demo/`);
 } else {
   // Production mode: static file server