NumPy 2 introduces many API changes, and a forward-incompatible ABI change. Since we can't do one-way ABI compatibility in Gentoo, I went for a full subslot bump. Since Python extensions don't do SOVERSIONs, ABI mismatch causes a runtime error of mismatched data type size. This often shows up in a different package's test suite. When it does, you need to track down the package that hasn't been rebuilt, and make sure to put numpy in DEPEND and include := slot operator, i.e.: DEPEND=" dev-python/numpy:= " Aside from that, you're probably going to see errors about removed stuff, numeric mismatched and other weird errors.
