[masklinn]

Yes indeed, does that mean similar katas across multiple languages have to be fully duplicated? I'd have expected an external checking system (à la TAP), doing everything internally with languages like Ruby or Python seems like a pretty bad idea.

[mikeash]

I think it's a bad idea for most languages. Even with C, C++, Go, Rust, or Swift, it's pretty trivial to exploit anything running within the same process. Any user-submitted code needs to be isolated from any code you need to be able to trust.