Communicate between finder sync extension and XPC

Working with some Apple Engineers they realized this was a problem and suggested using a LoginItem until a better solution is in place.

So, it is sort of an XPC service, just one that constantly runs. XPC communication is available to both extension and host app.

It works, although it is not the most ideal solution. I recommend the apple sample project that deals with XPC login items for an example of how to get this working.

I implemented MainApp <-> FinderSyncExtension communication via CFMessagePorts. See my question and answer for some details:

How should Finder Sync Extension and Main App communicate?