I'm sure I missed it, but is there any backwards-compatibility offered by scala-cli and the scala-toolkit?

If everyone ends-up using it via scala-cli --toolkit latest, I wonder what would happen if one day one library gets replaced by another or removed. Are we going to have a message like "error: some.library.name has been superseded by the.new.alternative", or will it just result in an import error and a deceived user?