Hi! I work on TUI rendering for Claude Code. I know this has been a long-standing frustration — it's taken longer than any of us wanted.
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.
Have you guys seriously considered decoupling the TUI / UI so anyone can write their own on top of Claude Code proper? I love how Zed did it, but its not always the most stable experience, but it is definitely better than staring at a TUI.
Why has public comms been so poor on this issue? There's been lots of Github issues posted in the Claude Code repo with lots of new comments each day screaming into the void, but radio silence from Anthropic since the revert in December. It's clearly causing a lot of frustration for users leading to clever workarounds like this.
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.
The communication is definitely on me! There honestly wasn't much new to say -I've been slowly ramping since early Jan just to be extra sure there's no regressions. The main two perf. issues were:
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.
> 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.
I'm using the latest version and see terrible flicker in tmux still. You guys should be ashamed tbh.
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.
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.
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.
I would love to use this but it breaks Ghostty's native scrollback (two-finger scroll), which I want more than I want to solve the flickering. The PTY proxy intercepts the output stream so Ghostty can't access its internal scrollback buffer anymore.
I wanted to believe, but wasn’t able to get most of my config working the same in zellij since it has fewer configuration knobs. Tried writing a plugin, but even those can’t touch much of the internal state. Particularly the keybinds I remember not being able to replicate (smart resizing, respecting vim, context sensitivity):
I have not used Claude Code in a couple months. THEY HAVEN’T FIXED THIS YET?
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
I'm always surprised that Python doesn't have as good TUI libraries as Javascript or Rust. With the amount of CLI tooling written in Python, you'd think it had better libraries than any other language.
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.
Textual is A++. Feels a bit less snappy than Ink, but it makes up in all things with its immense feature-set. Seriously fun building apps of all kinds with this lib.
It’s surprising how quickly the bottleneck starts to become python itself in any nontrivial application, unless you’re very careful to write a thin layer that mostly shells out to C modules.
They started with Ink but have since switched to their own renderer:
> 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).
React is just an abstraction of a State -> View function.
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.)
Thats the problem. Some developers want to avoid learning another programming language and use one for everything (including their technologies.)
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.
I’m a fan of Bubbletea, but it is significantly less ergonomic than React. Although I’d argue that if that starts to matter significantly, your TUI is probably too cluttered anyway and you should pare it down.
FWIW, Ink is working on an incremental rendering system: they have a flag to enable it. It's currently pretty buggy though unfortunately. Definitely wish Anthropic would commit some resources back to the project they're built on to help fix it...
I have a hypothesis: they haven't fixed this because they're using Claude Code to develop Claude Code. I'm a fan of Claude Code, but it isn't good enough to fix tricky issues like this. And because no one looks at the codebase themselves, they haven't been able to fix it after many months. Sometimes, all we need is an engineer to sit down for the weekend and fix the damn bug, not spin up 9 different Claude Agents prompted to fix itself.
I think its clear the team is drowning. They are just trying to keep their head above water. They have massive adoption, high churn in the underlying models, and unlimited numbers of github issues opened every day.
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.
This is a massive commercial product with a serious issue (everyone knows about the flickering) that hasn't been solved for months now. I don't think leeway is warranted.
> it’s because they don’t want people to see what a mess their code base is.
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.
I wouldn't be able to ship this to anyone without fixing it. Sending 5,000 lines of text to a terminal just to clear them all immediately, and in a loop... i'd be so embarrassed. Apps that clear scrollback have their uses, but you don't spam the terminal with unusable garbage.
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.
I mentioned this to Claude and this was the response:
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."
Not sure why you're being downvoted. Oh wait, I am, it's because this garbage doesn't work and nobody's allowed to point out that the emperor has no clothes. "We need the sum total of all capital on earth for our fancy Markov generator, and no, it doesn't redraw the screen properly."
One feature I'd love is a toggle to lock the input to the bottom of the terminal. It's a big inconvenience to have to scroll up and down between the chat and the input when responding to changes.
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.
Codex is so much more responsive for me no matter how long the session is running. Claude just starts stuttering badly when the session is running for sometime.
I don't know if this is my problem but formatting has been completely broken recently. It feels ... vibe coded. I wish they had not blocked opencode :(
I read the other day that one of their devs has a vanilla CC setup that consists of 10 agents running in parallel. Why doesn’t he just ask one of those agents to fix it??
I guess it's not hard to use AI to improve your productivity by 10x when your code is written by 0.1x devs. It's embarrassing an OSS fixed their problem before they did after all that money they raised
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
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