fix: Correct D-Bus signal subscription for properties changed

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

scan.py

@@ -7,7 +7,7 @@ logging.basicConfig(stream=sys.stdout,
 
 import asyncio
 from dbus_next.aio import MessageBus
-from dbus_next.constants import BusType
+from dbus_next.constants import BusType, MessageType
 from dbus_next import Message
 
 BLUEZ_SERVICE = 'org.bluez'
@@ -55,6 +55,14 @@ def on_interfaces_added(path, interfaces):
                 # Log repeat discoveries only if they have a name
                 logging.info(f"Found: {alias} ({addr_str})")
 
+def properties_changed_handler(message: Message):
+    """Sync handler to dispatch async task for property changes."""
+    if message.message_type == MessageType.SIGNAL and \
+       message.member == 'PropertiesChanged' and \
+       message.interface == 'org.freedesktop.DBus.Properties':
+        # Further filtering is done in the async handler
+        asyncio.create_task(on_properties_changed(message))
+
 async def on_properties_changed(message: Message):
     """Callback for when a device's properties change (e.g., Alias appears)."""
     if not message.body or message.body[0] != DEVICE_IFACE:
@@ -103,13 +111,12 @@ async def main():
     obj_manager_iface.on_interfaces_added(on_interfaces_added)
 
     # Subscribe to PropertiesChanged signal to catch late-arriving device names
-    await bus.add_match(
-        on_properties_changed,
-        mtype='signal',
-        iface='org.freedesktop.DBus.Properties',
-        member='PropertiesChanged',
-        path_namespace='/org/bluez'
-    )
+    rule = "type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged',path_namespace='/org/bluez'"
+    introspection = await bus.introspect('org.freedesktop.DBus', '/org/freedesktop/DBus')
+    proxy_obj = bus.get_proxy_object('org.freedesktop.DBus', '/org/freedesktop/DBus', introspection)
+    dbus_interface = proxy_obj.get_interface('org.freedesktop.DBus')
+    await dbus_interface.call_add_match(rule)
+    bus.add_message_handler(properties_changed_handler)
 
     logging.info("Starting Bluetooth scan... Press Ctrl+C to stop.")
     try: