Oh it also helps to split refactoring work into three buckets: business logic changes, performance changes (same output as before but faster) and cosmetic changes (rename files/folders/classes, breaking large files up, add logging/comments, domain layering etc). We tend to focus on performance and cosmetic changes for bulk refactors and leave logic changes to more dedicated sessions as to avoid changing what the system do (our domain is fairly complex and we cannot afford breakages). We also managed to port ALL of our code to dotnet 10 lts and have clean boundaries between projects (we have a mono-repo with about 50 projects in it), so we can wholesale upgrade dependencies without a sweat.
Of course, crashes and bugs can happen when applying quickfixes, which isn't nice. Ideally, they should be reported and fixed. You can also ask an agent to fix the occurences instead of using the IDE quickfixes if that's blocking you.
I guess what I'm trying to say is that IDEs shouldn't make that process harder, they can actually improve agents' results. For example, you don't need to write custom skills to prevent agents from writing some class of bugs if the IDE can detect it and agents have access to the results.
> Changing 200K+ lines of code yourself is a nightmare (and to prove it still does the same thing afterwards).
If an agent does it, you still have no proof, but okay.
Full disclosure, I work at JetBrains, but not in the IDE department.
Where now, the compiler flags & strict analyzer settings forces claude to do the right things (we explicitly tell claude not try and bypass or lower the barrier). I think it only works because we don't spend 95% of our time in the IDE anymore like a couple of years back, so we as developers no longer feel that friction, as claude tries to satisfy the compiler instead. Its a massive mental load that is just gone, we haven't had any conversations in meeting about this kinda stuff anymore (remember in the past we would have flameouts in meetings or code reviews about linter settings...).