The story
It started with wanting to understand editor architecture in Swift properly, so I went looking through the open-source projects that already existed. I'd been a heavy CotEditor user for a long time, and the more I used it the more I could see exactly where I wanted it to go — so forking it felt like the obvious move. I started in on the parts I cared about most, replace-in-file being the first.
One feature at a time turned into a lot of features. And at some point it became clear the old core — TextKit, built for a different era of files — wasn't going to get me where I wanted to be. So the core engine became a totally new one, written from scratch, and everything built on top of it since has been new too.