Vibing a non-trivial Ghostty feature

Summary

I recently shipped a non-trivial Ghostty feature (unobtrusive macOS automatic updates) that was largely developed with AI. I'm regularly asked to share non-trivial examples of how I use AI and agentic coding tools and this felt like a golden opportunity to walk through my process with a well-scoped, non-trivial, real-world, shipping feature1. This post will share every single agentic coding session I had on the path to shipping this feature, unedited and in full. Alongside it, I'll provide some additional context about my process and reasoning. And yes, I'll also share the token cost for those curious about that, too. Important: there is a lot of human coding, too. I almost always go in after an AI does work and iterate myself for awhile, too. Rather than say that at every turn, I'm just saying it once here. Therefore, you may see some discrepancies between what the AI produced and what ended up in the final code. This is intentional and I believe good AI drivers are experts in their domains and utilize AI as an assistant, not a replacement. The Feature The finished feature this blog post is about is the macOS unobtrusive update notification feature. This feature shows update status within the terminal window without interrupting work by creating windows, grabbing focus, etc. Let's set the stage for what lead to this feature (pun intended, as you'll see shortly). During a high-profile OpenAI keynote, a demo was rudely interrupted by a Ghostty update prompt: I wanted to ensure that never happened again2. The path I decided to take was to make update notifications unobtrusive. Instead of popping up a window, the app would instead show a small, non-modal GUI element somewhere that wouldn't interrupt the user. Pre-AI Planning So I pulled out my AI tooling. Absolutely not. I began by coming up with a rough plan of how I wanted this to work. Ghostty uses Sparkle, an extremely popular macOS update framework. I poked around their docs and found that they support custom UI t...