Just come across this. Haven’t dug too deep but sounds like an interesting opportunity. I think it can only succeed if it is fully compliant with current systems. Seems to only be mobile clients. No desktop? Are big tech going to permit this to grow? It would shut down a data mining opportunity …
Looks cute - internally it sounds like XMPP rosters if we imagine all mail messages/attachments are pulled too.
Some issues at a glance
I think there are some gaps on the notification side of things - the agent not being able to verify them (and maybe dropping) or conversely accepting notifications that it should not.
What really puts me off here is the unnecessary use of HTTP .e.g discovery moves from DNS to well known file (webfinger?). Not sure what the benefit is, but ok. And the use of a novel authentication scheme makes me nervous.
It was a nice read and I agree with the point that making this pull based helps. But I wish it did not try to invent so much in one go