Funny you mention that, I have very recently just came back from a one-shot prompt which fixed a rather complex template instantiation issue in a relatively big very convoluted low-level codebase (lots of asm, SPDK / userspace nvme, unholy shuffling of data between numa domains into shared l3/l2 caches). That codebase maybe isn't in millions of lines of code but definitely is complex enough to need a month of onboarding time. Or you know, just give Claude Opus 4.5 a lldb backtrace with 70% symbols missing due to unholy linker gymnastics and get a working fix in 10 mins.

And those are the worst models we will have used from now on.