Restore demo.queue() for Spaces runtime

app.py

@@ -1853,7 +1853,10 @@ def build_demo() -> gr.Blocks:
     return demo
 
 
-demo = build_demo() if os.environ.get("SPACE_ID") else None
+# When running inside a Space, create the demo and call `.queue()` to
+# ensure the Gradio background queue keeps the process active for the
+# Spaces runtime to serve the app.
+demo = build_demo().queue() if os.environ.get("SPACE_ID") else None
 # Expose `app` name as an alias — some deploy tooling looks for `app`.
 app = demo