diff --git a/backend/app.py b/backend/app.py
index ea1c0ab..bee4060 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -22,6 +22,8 @@ app = Flask(__name__)
 CORS(app, resources={r"/*": {"origins": "*"}})
 
 # Initialize SocketIO
+# Note: Frontend uses polling-only transport due to Cloudflare/reverse proxy
+# blocking WebSocket connections. Server supports both transports.
 socketio = SocketIO(
     app,
     cors_allowed_origins="*",
diff --git a/frontend/lib/hooks/useInteractiveTerminal.ts b/frontend/lib/hooks/useInteractiveTerminal.ts
index 1b599b9..b8cc5ac 100644
--- a/frontend/lib/hooks/useInteractiveTerminal.ts
+++ b/frontend/lib/hooks/useInteractiveTerminal.ts
@@ -114,9 +114,10 @@ export function useInteractiveTerminal({
           (window as any)._debugTerminal = term;
         }
 
-        const wsUrl = API_BASE_URL.replace(/^http/, 'ws');
-        socket = io(`${wsUrl}/terminal`, {
-          transports: ['polling', 'websocket'],
+        // Use polling only - WebSocket is blocked by Cloudflare/reverse proxy
+        // This prevents "Invalid frame header" errors during upgrade attempts
+        socket = io(`${API_BASE_URL}/terminal`, {
+          transports: ['polling'],
           reconnectionDelayMax: 10000,
           timeout: 60000,
           forceNew: true,