Queue is thread-safe but not process-shared.

Could you please show your uvicorn command for running server?

Also, I see you using debug=True. This command involves reloading, which can create two processes.

I could suggest you:

1. Use debug=False:

app.run(host='0.0.0.0', port=PORT_UI, debug=False)

2. Confirming it’s a single process in router handlers

print(os.getpid())