Remember: “no mistakes “.

Converting works really well when you have an oracle (something that you can test against and that is comprehensive)

I cannot begin to tell you how many places I have seen where this is fundamentally not the case. Not only are those tests missing, the software is fundamentally not written to be easily tested and in cases where multiple services across companies are concerned; how would you?

Rewriting via LLM is just not something the caretakers of a legacy banking- og state infrastructure system would countenance (not should they).

Well if you want to rewrite something like the PHP engine then you can obviously prompt the LLM to test against the existing legacy engine. You don't necessarily want to rewrite it 100% compatible because the goal is to avoid recreating the same security bugs, but it gives you a pretty good starting point.

LLMs still make mistakes, but generally fewer security mistakes than human developers.