Add eventlet back: use eventlet for SocketIO async mode

app.py

@@ -4,6 +4,10 @@ Pong backend (GPU, eager) for Hugging Face Spaces.
 Broadcasts readiness via Socket.IO so the frontend can auto-hide a loading overlay once the model is ready.
 """
 
+# Eventlet must be imported first and monkey-patched before other imports
+import eventlet
+eventlet.monkey_patch()
+
 import sys
 import os
 import time
@@ -38,11 +42,11 @@ from src.config import Config
 # --------------------------
 app = Flask(__name__, static_folder='static')
 CORS(app)
-# Configure SocketIO - use threading mode (no eventlet needed)
+# Configure SocketIO - use eventlet for proper WebSocket support
 socketio = SocketIO(
     app, 
     cors_allowed_origins="*", 
-    async_mode='threading', 
+    async_mode='eventlet', 
     logger=False, 
     engineio_logger=False,
     ping_timeout=60,