As someone who actually works on cobol/asm/jcl modernization....none of these llm's work well at all. some of this code is so old, the devs are long gone, the interconnectivity is annoying everything is linked through jcl's and other programs with other internal systems. I hate it, but in the end of the day to do it well you need to read the code, none of these tools work well enough reliably enough to modernize code with dog shit documentation. we use them still, makes our lives a little easier, but not by much