> Anecdotally, we use Opus 4.5 constantly on Zed's code base, which is almost a million lines of Rust code and has over 150K active users, and we use it for basically every task you can think of - new features, bug fixes, refactors, prototypes, you name it. The code base is a complex native GUI with no Web tech anywhere in it.

https://news.ycombinator.com/item?id=46522437

Zed is open source so you can look at their PRs and commit history. They even rolled their own Rust GUI framework for the project so it’s a decent case study of working on code that is barely in the training data (if at all).