Polynote's shading tool doesn't know to re-write the classpath for shadow JARs in the Scala metadata, which causes issues with the Scala kernel. The root cause is a mismatch between bytecode and scala metadata in the classfile. The bytecode names get relocated, but they're also present in the scala metadata which doesn't get altered. If our shading was scala-aware, this problem wouldn't occur.

A good short-term fix is to just try and re-try the cell a few times if we can detect this sort of failure in the kernel. Long-term, the best solution is just to fix how we do shading.