The emacs code is not purely diffing. They already have the final output, they’re mostly comparing it to see a cheaper way to update than render the output. I’m pretty sure the curses library have the same thing.

But ink, the library Claude is using, defines a tree data structure for the main concept. The diff there is about comparing the old tree and the new tree created by the update, and then updating the node that has changed. That means if a single character change inside a bing panel, the whole thing is rewritten. And if you have something that is updating a lot, that means flickering.

The diffing that ink does is just architecturally wrong. You can create a dom, but a dom is not a concept for the terminal. It’s up to you to optimize its rendering. But just diffing the dom structure like react does is not optimizing, it’s busywork.