How to Check a Cluster of Nodes and Upgrades in OTP?

I still some some foot guns or some things where you say okay this is not as yet working as we wanted to be working I mean one thing which pops my mind what I wanted to ask is like clustering and then having lots of different versions of the app that sounds like uh it sounds messy. After travel jersey actually I think this was his idea that you could actually do full type checking of joining a cluster or of upgrading a cluster if you annotated the clusters with all of the type information of the program that they're running. That would probably make them completely safe upgrades because you've got to do a lot of work to be confident the upgrade is going to perform as it should. If