Thanks, I agree that this is a problem that's worth fixing.

I don't think this change is required; see#112509 (comment)

I actually think whether or not static type checkers should consider this behaviour illegal according toPEP-589 has little bearing on what we should do at runtime here. I don't want us to start raising aTypeError if aTypedDict incompatibly overrides a specific key to make itRequired when the subclass specified the same key as beingNotRequired. Doing that now would break backwards compatibility at runtime, and I don't think there's a strong motivation for doing so: it's the job of type checkers to catch this kind of error and emit warnings about it. So, if we've ruled out raising aTypeError in this kind of situation, we just have to do the thing at runtime that makes the most sense -- and the status quo doesn't really make any sense, I don't think :)