It becomes a really huge machine! Do you have any plans for the next release(s)?
Saving progress and restoring partial search?
Using a range in derivation path?
I was briefly comparing what you have with features of 'lostword' and looks like you have (almost) all

For now until version 1.0 I'm focusing on increasing my test coverage and finding bugs while improving the printed reports and messages.
After that I'll start investigating how to add GPU support.
Anything else I'll try to squeeze in if I have any idea of how to implement them efficiently without needing any significant code change.