Hot reloading is always a pit tricky. The programming model needs to explicitly support it. In lunatic it will consist of 2 parts:

1. Stuff inside the vm that lets you keep the process id and message queue, but replaces the code running.

2. Higher level libraries that allows you to preserve state when the code is reloaded and potentially do state modification so that the newly loaded code can continue operating on the existing state.

This is fairly similar to how Erlang does it and I think it's a good approach for most use cases.