That’s a perfect example and interesting to read, thank you for sharing

I'd been imagining taking the Zig Language Server and adding some refactorings to it—it only had a bare minimum like Rename Symbol. It seemed like a huge project with so much context to get familiar with, so I put it off indefinitely. Then on a whim I decided to just ask GPT-5 (this was before Codex, even, I think?) to give it a go. Plopped it down in the repo and said, basically, implement "Extract Function". And it just kind of... did. The code wasn't beautiful, I could barely understand it, some of which must perhaps be blamed on the existing codebase not being exactly optimized for elegance, but it actually worked. On the first try! We continued to implement a few more refactorings. Eventually I realized the code we were churning out actually needs major revision and rewriting—but it took me from less than zero to "hey, this is actually provably possible and we have a working PoC" in, like, fifteen minutes. Which is pretty insanely valuable.

I think it kind of shines in this type of task. I am building my own game engine and it's very good for this type of refactoring. On some other tasks though, it clearly makes bad architectural decisions imo, like more junior developer might not get them but for instance in my game engine, it often tries to be too generalist like trying to build something akin to Unity that can do all sorts of games rather than focus on the type of game I am building it for unless I very explicitly always say it

It’d be probably useful to include this very comment in your system prompt or a separate file which you ask the coding agent to read at the beginning of each session.