(I spelled it "Monocypher", without the first "h".) I need SHA-512 for tests. The only test vectors I could find were for the official ed25519, with SHA-512.

(I spelled it "Monocypher", without the first "h".) I need SHA-512 for tests. The only test vectors I could find were for the official ed25519, with SHA-512. The option is there anyway, I might as well provide it. I do transparent naming because the choice of primitive has user visible effects. If I have the SHA-512 of some file, I can't just use Blake2b to check that hash. Same for encryption and authentication: changing them is transparent only for transient messages. Encrypted files won't convert themselves to the new encryption scheme, and neither will the authentication tags. Same thing for long term secret/public key pairs. That said, the high level constructions don't mention the primitives. They're all called "crypto_lock" or something. Long term, changes are not expected to be transparent. The only backward compatible path is to stick to the older version of Monocypher. Any transition will need to be handled explicitly. I think that's okay, because I don't think I'll need to make breaking changes often. I expect a stable version to last at least 5 years, possibly 15. Then the next version will break everything, and users will just have to cope, most probably by supporting both v1.0 and v2.0 for a time. Hopefully that won't be too hard, given the small size of the library.