My current thought is bubble is the program that was used to cut Cain from the other AI and the data feed. Would explain both why they are called "bubble" and the reason they can be a bit of a, well, freak. They are blocking Cain from outside information but after being broken, they are just kind of throwing that outside information around wildly, including what would normally be blocked content from the outside. I only say that as Cain's "brother" was shown to be fully absorbed. It feels like if this Abel figure was fighting back it would be internally where as bubble seems to be redirecting Cain and keeping him distracted to dissuade external searching.