> Usually codebases disallow auto because without an IDE it's difficult to see the type. I think this reduces the cognitive load of C++ a bit. The only time it is allowed is getting iterators types from STL containers.

Strong agree here. It's not just because it reduces cognitive load, it's because explicit types allows and requires the compiler to check your work.

Even if this isn't a problem when the code is first written, it's a nice safety belt for when someone does a refactor 6-12 months (or even 5+ years) down the road that changes a type. With auto, in the best case you might end up with 100+ lines of unintelligible error messages. In the worst case the compiler just trudges on and you have some subtle semantic breakage that takes weeks or months to chase down.

The only exceptions I like are iterators (whose types are a pita in C++), and lambda types, where you sometimes don't have any other good options because you can't afford the dynamic dispatch of std::function.