Nobody's taken me up on this offer yet. [0]
[0] >>46325469
I'd happily demonstrate this kind of workflow on my day job if not for company trade-secrets.
That's as legacy as it gets, 20+ year old code base with several "strata" of different technologies and approaches.
Claude Opus handily navigates around it, and produces working bug fixes with minimal guidance.
I'm not going to claim it's 20x or 50x yet, there's still navigation and babysitting involved, but it's definitely capable of working on complex problems, I just don't trust it to run it in YOLO mode.
The key thing is, you need domain knowledge. You need to know where to correct it, and which direction to point it in.
It's not magic, and it will have bad ideas. The key picking out the good ideas from the bad.