This version is only breaking because we are now properly emitting mutation events when the mutation is actually occurred. This should not affect your app. Remember when upgrading that all packages needs to install @latest.
You can now customize the delimiter Overmind uses to define state paths. This allows your state keys to contain .. docs
Derived functions can now be added and removed dynamically
Typescript can now define derived with a function, derived, this gives a more natural typing experience with the new dynamic derived. docs