I agree, the llm _vastly_ speeds up the process of "rebuilding the theory" of dead code, even faster than the person who wrote it 3 years ago can. I've had to work on old fortran codebases before and recently had the pleasure of including ai in my method and my god, it's so much easier! I can just copy and paste every relevant function into a single prompt, say "explain this to me" and it will not only comment each line with its details, but also elucidate the deeper meaning behind the set of actions. It can tell exactly which kind of theoretical simulation the code is performing without any kind of prompting on my part, even when the functions are named things like "a" or "sv3d2". Then, i can request derivations and explanations of all relevant theory to connect to the code and come away in about 1 days worth of work with a pretty good idea of the complete execution of a couple thousand lines of detailed mathematical simulations in a languages I'm no expert in. LLMs contribution to building theory has actually been more useful to me than is contribution in writing code!