> But today trivial to simple applications can be rewritten from spec or scratch in an afternoon with an LLM. And even pretty complex parsers can be ported provided that the tests are robust enough[1]. It's just a metter of time someone rewrites a small to medium size application from one language to another using the previous app as the "spec".

This seems like a sort of I dunno chicken and the egg thing.

The _reason_ you don't rewrite code is because it's hard to know that you truly understand the spec. If you could perfectly understand the spec then you could rewrite the code, but then what is the software, is it the code or the spec that writes the code. So if you built code A from spec, rebuilding it from spec I don't think qualifies a rewrite, it's just a recompile. If you're trying to fundamentally build a new application from spec when an old application was written by hand, you're going to run into the same problems you have in a normal rewrite.

We already have an example of this. Typescript applications are basically rewritten every time that you recompile typescript to node. Typescript isn't the executed code, it's a spec.

edit: I think I missed that you said rewrite in a different language, then yeah fine, you're probably right, but I don't think most people are architecture agnostic when they talk about rewrites. The point of a rewrite is to keep the good stuff and lose a lot of bad stuff. If you're using the original app as a spec to rewrite in a new language, then fine yeah, LLM's may be able to do this relatively trivially.