Scala is the language where two developers on the same team write genuinely different dialects. One writes pure functional code with cats-effect IO , typeclass-derived instances, and Either[AppError, A] at every boundary. The other writes what looks like Java with better syntax — null returns, throw new RuntimeException , var counters, ArrayBuffer mutated in a for loop, Future chains with swallowed exceptions, and a deep class hierarchy rooted in an abstract BaseService . Both compile. Both pass tests. Only one of them survives contact with concurrency, error handling, and the production JVM. Then you add an AI assistant. Cursor and Claude Code were trained on fifteen years of Scala code that spans Scala 2.8 Java-in-Scala through modern Scala 3 with ZIO 2 and Cats-Effect 3.…