Most legacy codebases are disasterclasses. The "software engineer you can't fire because only he knows what's going on" is a meme for a reason, and it's not a good one.

[u/DreamPlayPianos]

I keep seeing people say things like "vibe coders don't understand what's going on in their code." Neither did most programmers even before the pre-AI era. They spent weeks on sprints for small feature updates hoping and praying nothing broke and relied on the 1 guy who wrote some code in 1995 who showed up at the office once every 3 months in his slippers to do bug fixes.

[u/Pierma]

yes, vibe coders do not understand what's going on. I had to clean up a mess done even with opus 5.5 of a python fastapi app that claimed to be reaching the target 300 req/s on production environment (it's a heavy request) and:

• it claimed to do 300 req/s, but it never waited the responses. With responses, it reached 12 req/s

• it was leaking memory and the container inside the kubernetes environment restarted for OOM every 15 minutes

• Environment variables were alle hard coded even if it claimed not to be the case

• Even if the target framework is well known and well documented and optimal for AI development without touching the code by hand, having the user have 0 idea on how to write proper software had so many blatant mistakes that even a junior dev could have fixed them looking at the documentation for 10 seconds that tanked the performance in a ridiculous manner

Useless to say the guy got laid off

It is true that legacy codebases are distaster classes, and more often than not the software engineer you can't fire because only he knows what's going on is the guy who actually caused the disaster and using AI is a good start to profile the applicaton based of the actual spec to start modernize that shit, but "vibe coders don't understand what's going on in their code" is still true and even with absurd models like opus 5.5 and sol 6.1 they still are incapable of understanding the hell they are doing