Writing the best possible specs for these agents seems the most productive goal they could achieve.
So, no circular prompt feeding at all. Just a normal iterate-test-repeat loop that happened to involve two agents.
Sort of like MS's old chatbot that turned into a Nazi overnight, but this time with one agent simply getting tired of the other agent's lack of progress (for some definition of progress - I'm still not entirely sure what the author was feeding into Claude1 alongside errors from Claude2).