A Cipher Thought Experiment

[asteckley]

This depends on the size of the corpus, I think...

It seems there is also the issue of having the plaintext solution available.  
Your use of chatGPT (and Claude) was really well done! (Your solution isn't complete, but it is apparent that it is pretty close.)  How far do you think you might have gotten without having the plaintext solution available? 

The other interesting statistical question (although we can only surmise the answer for this particular cipher and not in general) is just how many crib words would suffice to crack the code.