This is remarkable. Man, there are all those ancient things that "we've lost the source code for". One time, in a past job 10 years ago we were reimplementing something that was lost to the sands of time, using an out of date spec it had used. It was such a tedious job with verification but we got there. Amazing how easy that would be today.
I don't think this kind of thing works nearly so well without a comprehensive test suite or the ability to easily use the reference version as a test harness. The typical enterprise relic for which no specification or source remains almost surely lacks the former and probably isn't very amenable to the latter.
Are you sure you will be able to spend time playing around that kind of stuff when anthropic/openai/google/etc make you jobless? (well, perhaps not YOU precisely, but 90% of devs, so there’s a high chance).
We always think it’s not gonna hit us… we may be wrong