They chose to use a react rendering to native TUI renderer, which was a source of a lot of performance issues.
AFAIK, they have written a new renderer.
The source of the performance issue here is their own incompetence, actually. I have never in my entire career heard of a rendering pipeline as idiotic as the custom one they built.
Which is equally terrible and has earned them every single rendering engineer in the world taking the piss out of them when they proudly announced it was as complicated as rendering a video game.
That's such a stupid engineering choice that it really makes one question if the people working at Anthropic have any software engineering ability at all. There's no excuse for running React in a freaking TUI.
Which makes the parent comment’s “Bun performance hacks and optimizations” sound a little far-fetched, at least in this scenario I don’t think that’s gonna be the deciding factor. Their vendored JSC is also not touched by this port-rewrite at all whatsoever (still Cpp), so I’m not sure if it’s even possible to hack-improve all that much there.