Here's a way to get a cycle in the dependency graph

[axch]

assume switchx (flip)
assume switchy (flip)
force switchx true
assume x (if switchx 0 (exactly y))
assume y (if switchy 0 (exactly x))
observe switchx false
observe switchy false

It doesn't complain as long as you do (mh default one), but when you do (mh default all) it blows up because there's a cycle in the regen graph.

[axch]

So, what do we want to do about this (even in principle, as opposed to right now)?