My experience with Claude and Ruby, Python, Javascript is similar: it's pretty good at finding the array of strings that was passed to a method instead of an array of integers. Think about record ids coming from a JSON API call. Or the single value instead of an array. I don't remember which Python XML parser is fond of returning one or the other according to the cardinality of the sub elements. Anyway, not only it writes the code to handle those cases but it traces the code and it finds the bugs. So type checking at coding time and who cares about writing the type annotations. They would be probably good to speed up the code at runtime but none of my customers use them and none of them is concerned about the current response time of their systems.