The good news: we shipped our differential renderer to everyone today. We rewrote our rendering system from scratch[1] and only ~1/3 of sessions see at least a flicker. Very, very few sessions see flickers in rapid succession which was so annoying before. Those numbers will keep dropping as people update.
We've also been working upstream to add synchronized output / DEC mode 2026 support to environments where CC runs and have had patches accepted to VSCode's terminal[2] and tmux[3]. Synchronized output totally eliminates flickering. As always, I recommend using Ghostty which has 2026 support and zero flicker.
Happy to answer questions!
[1]: https://github.com/anthropics/claude-code/issues/769#issueco... [2]: https://github.com/xtermjs/xterm.js/pull/5453 [3]: https://github.com/tmux/tmux/pull/4744
Thanks for the update!
It was obviously a complex issue (I appreciate that and your work!). But I think there's a lot to be improved on with communication. This issue in particular seems like it has lost a lot of user trust - not because it was hard to solve and took awhile - but because the comms and progress around it was so limited.
Eg issues: * https://github.com/anthropics/claude-code/issues/1913 * https://github.com/anthropics/claude-code/issues/826 * https://github.com/anthropics/claude-code/issues/3648
1. Since we no longer have <Static> components the app re-renders much more frequently with larger component trees. We were seeing unusual GC pauses because of having too much JSX... Better memoization has largely solved that. 2. The new renderer double buffers and blits similar cells between the front and back buffer to reduce memory pressure. However, we were still seeing large GC pauses from that so I ended up converting the screen buffer to packed TypedArrays.
...after many months, for such a visible bug, is such a crazy thing to say.
In case the above comes across as too hostile, to balance this, I would say thank you to the claude code team for such an amazing product!
I'm using the latest version and see terrible flicker in tmux still. You guys should be ashamed tbh.
Another option is to rebuild tmux from latest source so it buffers synchronized output, which should prevent the flicker entirely.
If you're still seeing a terrible flicker please file a `/bug`!
> How tall is your tmux pane? If it's very small it might still flicker as CC tries to redraw scrollback. I've noticed several tmux users have layouts where they stack several panes on top of each other making each one quite short.
It's full screen ("maximized" as tmux calls it).
> Another option is to rebuild tmux from latest source so it buffers synchronized output, which should prevent the flicker entirely.
I'll give it a shot.
What else do you want me to say? It's ironic that one has to jump through hoops (like this post) to get basic functionality right in a tool that claims it'll replace software engineers.
Am I missing some complexity here?
I’m starting to think that the reason why anthropic doesn’t open source Claude code isn’t due to competitive reasons, it’s because they don’t want people to see what a mess their code base is.
Maybe they bought Bun to increase the rate of flickering so that the text looks solid again
https://github.com/anthropics/claude-code/issues/769
I locally patched the closed-source CLI npm package but it's not perfect. They would have to switch how their TUI is rendered on their side.
Apparently OpenAI Codex is rust+ratatui which does not have this issue.
https://github.com/jquast/blessed
One reason for the lack of python might be the timing of the TUI renaissance, which I think happened (is happening?) alongside the rise of languages like Go and Rust.
example: `ranger` is written in python and it's freaking slow. in comparison, `yazi` (Rust) has been a breeze.
Edit: Sorry, I meant GIL, not single thread.
You probably mean GIL, as python has supported multi threading for like 20 years.
Idk if ranger is slow because it is written in python. Probably it is the specific implementation.
> We originally built Claude Code on Ink, a React renderer for the terminal. [...] Over the past few months, we've rewritten our rendering system from scratch (while still using React).
https://github.com/anthropics/claude-code/issues/769#issueco...
While not universally applicable, it's very convenient during development to focus on State without thinking about View, or focus on View without thinking about State.
The concept itself has nothing to do with the actual renderer: HTML, TUI, or whatever. You can render your state to a text file if you want to.
So the flickering is caused either by a faulty renderer, or by using a render target (terminal) that is incompatible with the UI behavior (frequent partial re-renders, outputting a lot of text etc.)
Any web react project out there will install react AND react-dom, which is the son implementation of react.
It’s how react translates into mobile, web, etc so well.
It defines contracts and packages like react-dom handle th specific implementation.
Using TS, React here doesn’t make sense for stability in the long term. As you can see, even when they replaced Ink and built their own, the problem still exists.
There are other alternatives that are better than whatever Anthropic did such as Bubbletea (Go) or Ratatui (Rust) which both are better suited for this.
Maybe they were thinking more about job security with TypeScript over technical correctness and a robust implementation architecture and this shows the lack of it.
We moved from the go+bubbletea based TUI which had performance and capability issues to an in-house framework (OpenTUI) written in zig+solidjs
Should it be solved by now? Yes. If anyone on the team is dogfooding it in a typical tmux environment, its painful. But lets give them some leeway here.
if Amodei hadn't said "90% of code will be written by AI", at least I wouldn't call them hypocrites, but the fact that the company that makes such wild claims can't fix a freaking flicker and scroll issue until an indie-dev steps in just shows how far behind their product is from their claims.
I have CC and use many models with it (Codex in CC, try it!), but I won't let Anthropic "lecture" us about how "the roots of the problem go deep". Literally no other CLI tool has these issues: opencode, codex, gemini, droid, etc.
And we solved this problem over 30 years ago? Ncurses was made for this. The buffer is kept in memory, you hit page-up and it renders the previous page, page-down and it renders the next page, let it roll and it renders each successive page as a stream, or just the last page, etc.
Ha! The irony is not lost on anyone.
"We've built the world's most advanced AI coding assistant. It can refactor entire codebases, debug complex issues, and ship production features autonomously. Anyway, here's a terminal bug that makes your screen look like a slot machine. We'll get to it eventually."
It would be a game changer for mobile usage.
nit but CC itself doesn't write anything, much like a body w/o brain doesn't program anything. it's possible the OP was using other models like codex/gemini/etc. in CC.
We've rewritten Claude Code's terminal rendering to reduce flickering by 85% - https://news.ycombinator.com/item?id=46312507 - Dec 2025 (3 comments)
Anthropic: Please fix this ASAP