app/broker.py

"""
A singleton message broker for the application.

This ensures that the same asyncio.Queue instance is shared across all parts
of the application, including background tasks and API request handlers,
solving state-sharing issues in ASGI lifecycles.
"""
import asyncio

class SignalBroker:
    def __init__(self):
        self.queue = asyncio.Queue()

# Create a single, global instance of the broker.
# When any file imports 'signal_broker', they will get this exact same object.
signal_broker = SignalBroker()