If TypeScript has the integration testing framework in place to verify that the compiler actually works (and it should) - then, presumably, you should be able to swap in a Chinese Room black-box and - at least - know that it works.

You do have to be worried that it's possibly installing trojan horses on your computer while compiling code, or any other number of unwanted side effects.

But you can and should be able to have integration testing in place to know that a compiler - at a minimum - actually works.

Totally fair. The thing is, though, agents often write code in ways I don't expect, and I don't think any human would write, which makes me think that code may also break in a way that no human expects or would have written a test for.