Update app.py

app.py

@@ -334,6 +334,7 @@ with gr.Blocks(css=css) as demo:
 # ------------------------------------------------------------------
 # START THE GRADIO SERVER
 # ------------------------------------------------------------------
-demo.queue()                        # optional: allow 20 waiting jobs
+demo.queue(default_concurrency_limit=1,        # ≤ 1 worker per event
+           max_size=20)                        # optional: allow 20 waiting jobs
 
 demo.launch(share=True, mcp_server=True)