There could be s/recursive too, some discussion in https://github.com/metosin/schema-tools/issues/30. If you end up with good solution, PR would be most welcome there.

Thanks, I was not aware of s/recursive. I am ending up checking known schema records, so I am not entirely satisfied (and still miss edge cases). It also means I have to extract the data from some of them (`s/if` and probably others). I also gave up on "unflatten" for a schema, since I loose some information (in my case I stringify the keywords and loose the optional-key position, and some things like the s/if predicates are lost. Although this could still be done for "simple" shemas if I kept an array of keywords). So, still thinking about it but I don't think there is a general solution that would allow to roundtrip between flatten/unflatten (at least not without metadata and I am not willing to go there).