@evan Thanks for the response. I think how a given software does double-knocking is up to that software. It is not necessarily true that you have to store the result, but it is ideal. I am much too lazy to refactor a persistent cache and I just double-knock every time. :P

But to start, those libraries need to be able to support both signature implementations as those libraries are already in-use by the majority of software that has not implemented RFC 9421 yet.