Ask HN: What are your biggest problems and fixes with multisession engineering?

I have run into a lot of issues using multiple sessions at once to build things, and I really want to hear from those that have figured a good amount out.

Or at least hear what problems people are having to know if I am running into the same blockers everyone is.

For example, I often want to have agents stop at certain points, but fail to get a mechanism that works.