I've been using Claude to implement an ISO specification and I have to keep telling it we're not interested if the repl is correct but that the test suite is ensuring the implementation is correctly following the spec. But when we're tracking down why a test is failing then it'll go to town using the repl to narrow down out what code path is causing the issue. The only reason there's even is a repl at this point is so it can do its 'spray and pray' debugging outside the code and Claude constantly tried to use it to debug issues so I gave in and had it write a pretty basic one.

Horses for courses, I suppose. Back in the day, when I wanted to play with some C(++) library, I'd quite often write a Python C-API extension so I could do the same thing using Python's repl.