Thanks! For the context, I ran into this error when trying to update the branch of this PR to 3.0.0-RC2 (discussed in https://contributors.scala-lang.org/t/porting-ammonite-to-dotty). It uses Scala 2 libraries from Scala 3 and the other way around too, so the tasty format has to match exactly. As soon as a 2.13 nightly for tasty 28.0.3 is available, it should be possible to update to 3.0.0-RC2 (and merge this PR, at last).