Right-Hand Editable Diffs
2025-06-23 by Philip Zeyliger
When I program with Sketch, I find myself part product manager, part software architect, part code reviewer, and part tester. There's a blog post to write about each, but let's talk about reviewing code.
In our diff view, the right-hand side is editable. If you don't like something the agent did, you can just edit it directly, right there when and where you're reviewing the diff.
I learned this trick many moons ago from John Reese at Google, who introduced me to the idea and kindly shared his perforce-flavored script for the same goal. I long ago adapted it for git in. It's a shell script and a vimrc that lets you navigate (Ctrl-N for next) across your diff and edit the right hand side. I've been doing it to add comments and double-check my patches for decades! It makes just as much sense when the code you're reviewing is coming from an agent.
Of course, our diff view also lets you leave comments for the agent. We thought about introducing a complicated data model for it, but it turns out that just appending your comments to the chat box works quite well.