Oh lovely, will have to give this a read at some stage!

I'd also be really interested in versioning, and upgrading a cluster over time, without bringing the whole thing down (like with Cloud Haskell). Would be super handy to be able to verify that your migration works first, before actually going ahead with it. I'd also love it if the types could be used in some way to make this kind of thing easier to reason about.

Are you also aware of the work advancing in Akka Typed? After a number of iterations they made some modifications that made things simpler - not sure how it compares with your work though: https://doc.akka.io/docs/akka/2.5/typed/actors.html#relation...