CLAUDE.md for Scala: 13 Rules That Make AI Write Idiomatic Functional Code

CLAUDE.md for Scala: 13 Rules That Make AI Write Idiomatic Functional Code You ask Claude to "add a Subscription service that calls Stripe" inside your Scala codebase, and you get back something that compiles cleanly and is still wrong: A function that returns null when the user isn't found, instead of Option[User] . Three Future { … } blocks chained with .map / .flatMap and an Await.result at the bottom — inside a service that's otherwise running on cats-effect. A class Order(var status: String