I think it's fair enough to consider porting a subset of rewriting, in which case there are several successful experiments out there:

- JustHTML [1], which in practice [2] is a port of html5ever [3] to Python.

- justjshtml, which is a port of JustHTML to JavaScript :D [4].

- MiniJinja [5] was recently ported to Go [6].

All three projects have one thing in common: comprehensive test suites which were used to guardrail and guide AI.

References:

1. https://github.com/EmilStenstrom/justhtml

2. https://friendlybit.com/python/writing-justhtml-with-coding-...

3. https://github.com/servo/html5ever

4. https://simonwillison.net/2025/Dec/15/porting-justhtml/

5. https://github.com/mitsuhiko/minijinja

6. https://lucumr.pocoo.org/2026/1/14/minijinja-go-port/

Not me personally, but a GitHub user wrote a replacement for Go's regexp library that was "up to 3-3000x+ faster than stdlib": https://github.com/coregx/coregex ... at first I was impressed, so started testing it and reporting bugs, but as soon as I ran my own benchmarks, it all fell apart (https://github.com/coregx/coregex/issues/29). After some mostly-bot updates, that issue was closed. But someone else opened a very similar one recently (https://github.com/coregx/coregex/issues/79) -- same deal, "actually, it's slower than the stdlib in my tests". Basically AI slop with poor tests, poor benchmarks, and way oversold. How he's positioning these projects is the problematic bit, I reckon, not the use of AI.

Same user did a similar thing by creating an AWK interpreter written in Go using LLMs: https://github.com/kolkov/uawk -- as the creator of (I think?) the only AWK interpreter written in Go (https://github.com/benhoyt/goawk), I was curious. It turns out that if there's only one item in the training data (GoAWK), AI likes to copy and paste freely from the original. But again, it's poorly tested and poorly benchmarked.

I just don't see how one can get quality like this, without being realistic about code review, testing, and benchmarking.

I used one of the assistants to reverse and rewrite a browser-hosted JS game-like app to desktop Rust. It required a lot of steering but it was pretty useful.

https://x.com/CanadaHonk/status/2011612084719796272 as well.

I went through the motions. There are various points in the repo history where compilation is possible, but it's obscure. They got it to compile and operate prior to the article, but several of the PRs since that point broke everything, and this guy went through the effort of fixing it. I'm pretty sure you can just identify the last working commit and pull the version from there, but working out when looks like a big pain in the butt for a proof of concept.