This is entirely possible with Claude as it existed even last year.

The LLMs are quite good at re-writes and even better when provided an 'oracle' like a well rounded test suite or existing implementation to work against.

Its part of the reason we keep seeing "I rewrote <library> in <language>" posts on hackernews and when you look at the repo its more like I prompted claude to rewrite this repo in rust or whatever.

As an Anthropic acquihire, not only does he have access to every model and service but he probably has infinite tokens available.

Bun powers Claude.