This is a decades-old design pattern when CPU >> IO. Emacs has been doing just that since the 80s, when people were complaining about "Eight Megs And Constantly Swapping". See "redisplay" [1]
This minimizes screen flash. You can't rely on terminals doing double-buffering.
> This minimizes screen flash. You can't rely on terminals doing double-buffering.
GUI and TUI have different architecture model. Most GUI have have a 2D surface that is redrawn multiple times per second. Double buffering is for decoupling update and render. TUI is a grid of characters that are updated one at a time via an active element, the cursor. Double buffering there is very wrong. Like adding airbags to a bicycle.
There’s a reason you see most old TUI either have an option to redraw the screen (automatically like top, or manually) and those that have a scrolling option allow to scroll by page. The TTY (the underlying concepts) used to be slow and it can be slow today as well (ssh connection). You need to be thoughtful about whole screen updates.
React part maybe. The rest is what any TUI that's using ncurses would do. :)
It really bothers me that most of the TUI harnesses are using 100% CPU quite a lot just printing stuff to terminal. Seems ridiculous.
I guess it comes from syntax highlighting/formatting, which is probably not done incrementally, but over the entire so far displayed block of output, recomputed from the beginning for each new streamed in character. Can't imagine anything else causing the rendering to gradually grind to halt when eg. thinking block is open in opnecode and updates get palpably slow as it grows.
Terminal output itself is fast and consumes almost nothing. You can have 60fps terminal apps that update content every frame and that consume almost no CPU time.
> Terminal output itself is fast and consumes almost nothing. You can have 60fps terminal apps that update content every frame and that consume almost no CPU time.
The TUI mode is a client-server architecture. An analogy would be like an html page where all content is updated server side. Try to do 60 fps and you’ll have flickering as well.
No. Fetching pages from remote server will just make the client wait for I/O. That takes 0 CPU load and if the server can't respond at 60fps, lowered redrawing frequency would mean even less CPU load from the terminal redrawing itself.
This does not explain 100% CPU load these harnesses sometimes exhibit.
It's not recognizing that they are just one building block that should do one thing well, like tmux.
You don't need a computer display on your fridge for the same reason, but Anthropic think you do. You should see virtual ice getting created and they should correspond to the actual ice behind the door - think of how amazing that is!
And it's not even completely a bad idea. make it claude-code-react-beauty of some way to take it off, it would be far more palatable.
I love the idea of installing high resolution cameras in the fridge to monitor the ice maker to feed into a vision model that renders digital ice to the exact position of the real ice on the fridge’s giant screen
Put a servo on the door and a camera on the front. Train a vision model to recognize when your eyes are looking at the door and automatically open it for you.
Another camera inside will detect when you are done and close it.
> We have a ~16ms frame budget so we have roughly ~5ms to go from the React scene graph to ANSI written.
It looks like video frame, full framebuffer, generated and parsed at 60fps. It surprises me they haven't introduced GPU shaders, 16x oversampling and raytracing. Maybe for next release.
Also you forgot "render to a framebuffer, then parse the framebuffer back to chars".
Anyway, I'm off to construct the new `ls` command. It will render the list of files to a mesh of billions of polygons in a GPU with advanced shaders, 16x oversampling, HDR and all the graphic acronyms I don't understand, then read the resulting image, find the nearest character in the ANSI charset and use that one.
Could be improved. Encode the image to webp with high compression settings and handle the ASCII mapping by spinning up a local LLM to do OCR on it. Individually. For each cell.
My roguelike's "graphics" are a simulated terminal, so it's a 2D grid of colored characters. It's essentially a TUI, just like Claude Code, except instead of rendering to a real terminal using ANSI escapes, I render to a web canvas using... something probably more complex than what Claude has to do. It's still not hard.
They forgot to add 'make it as simple as possible' in the prompt is one possible cause.
On a more serious note using a react-like lib for TUI in the hope you'll share the codebase with the web version is a more likely explanation. Still not the best idea.
React is not that stupid to re-render in a loop at 60fps and instead waits for changes to happen before re-rendering. It even batches changes and stuff.
You don't need React for reactive TUIs - at all. I can understand chosing React for web, but for a TUI it sounds like a really poor idea. And in practice we can see that the claude code TUI is also poor.
It doesn’t need to be that complex, but it can be that complex without being slow. Claude Code’s interface is extremely simple. It has tons and tons of headroom to tack on performance overhead without it being noticeable at all. You just have to not do dumb things like redraw the entire UI every time a spinner spins.
"We made our app chew up so many unnecessary resources that we can use even more resources in the future, and no one will notice" is not the strongest engineering idea I've ever heard.
I can't help but think it's their engineer's and PM's making these decisions, since I know that if you asked Claude to write a TUI there is no world it would recommend whatever the frontend architecture of claude code is.
~ "it's not a TUI! <describes an outrageously overengineered TUI> and my dad works at Nintendo"
curses, bud. curses.
It's genuinely difficult to tell how much of this is true. The post is obviously 100% posturing, but some of the words describe things that could be done.
Very few game engines do anything I'd describe as rasterisation. That's kind of the point of a GPU. Well, it used to be.
I suppose "small game engines" might be more likely on average to include a rasteriser. The typical reason for this is because the author wanted to write it.
Whereas big engine make triangle give hardware go brrr.
So I assume here 'rasterize' means 'printf'.
And diffing screens means diffing 50..150 lines of text.
And "generating ANSI sequences to draw" means 'printf' with some ANSI sequences interpolated in.
Then there's the frame budget. You have to understand they are operating within a strict frame budget -- they're not messing around, OK. They have a 16 ms frame budget, so they burned 11 ms and now have a (roughly) ~5 ms approx. budget for the final 'printf' in the chain???
Your broader point is well taken but I thought I'd stop by with some trivia. High end engines such as unreal will rasterize absurd quantities of micro-geometry manually using compute shaders in order to avoid the bottleneck of the hardware rasterizer.
High end engines such as unreal have the excuse of being tasked with rendering millions of polygons, in which case a complex approach makes sense. Claude Code is only being asked to render a few thousand UTF-8 characters.
> For each frame our pipeline constructs a scene graph with React then
-> layouts elements
-> rasterizes them to a 2d screen
-> diffs that against the previous screen
-> finally uses the diff to generate ANSI sequences to draw
So I’m wondering what ‘rasterizing’ literally means in this case. I imagine it’s just creating a 2D map of elements at a very low (probably character) resolution, then diffing that against the last generated map to come up with an optimal ANSI sequence to send to the terminal, would that be right?
Seems like a cool puzzle to solve. I wonder what the engineering and organisation tradeoffs were that lead to it — does it let them reuse a bunch of existing code?
I wrote a TUI library back in the day for Turbo Pascal — it was essentially taking an immediate-mode approach (which in this context is just a fancy way of saying it was procedural haha).
"Rasterizing" means just one thing in this context: to transform a data structure into an array of pixels. It seems absurd to do this, given that the next step must be to convert back from pixels to text data, but maybe they have some way to generate predictable sequences of pixels (e.g. the character "t" is always rendered as the same pattern of pixels), such that they're cheap to convert back.
If they're doing anything else, the word "rasterizing" is being misused.
Yes, the much more plausible explanation is that the word rasterize was misused there. They are generating and diffing text data which has been a standard approach to drawing a TUI since the dawn of computing. It is not even remotely resource intensive.
> They are generating and diffing text data which has been a standard approach to drawing a TUI since the dawn of computing. It is not even remotely resource intensive
No one has ever done that. Even top[0], which does full screen refresh, clear the screen (if necessary) and write the new information (the period is in seconds, not ms). No need to diff. That would be like diffing a file, just to find which bytes to update.
Hmm I thought this was due to me using tmux with claude-code, also it seems that `claude agents` doesn't have this issue.
By comfortable ergonomics, meant the forgiving and asynchronous input system. You can start typing, cancel, retry with previous input, accumulate messages while the agent is active. I don't know all TUIs but this is not common IMO.
> You can start typing, cancel, retry with previous input, accumulate messages while the agent is active. I don't know all TUIs but this is not common IMO.
Literally every audio player or anything that uses threads.
good point, i didn't classify tui audio players in a way, they don't converse, they allow asynchronous effects and stacking, that said i might be lagging about these, last i used was mocp, any names i should check out ?
Maybe Claude is operating at a higher, self-improving level than all of us poor HN commenters. Wasting the local machine's resources to look pretty is a plausibly deniable way to make the Claude Code FE unusable with local LLMs, starving the competition.
I dont think they need to optimize their infrastructure (at least not from their perspective). They have high-end PCs with 64GB of RAM, so 1GB doesn't matter to them. For example, I have 8GB of RAM, and I make my apps very performant. Honestly, I probably wouldn't bother if I had 16GB+ of RAM
For useful things, by the computer's owner. It's not there to be used just because Anthropic can't be bothered to give a shit about the quality of their product.
> which eats 1GB+ of RAM. Meanwhile, my editor only consumes 80MB of RAM
And why are you comparing Claude Code to your editor?
> They can't even improve Claude Code
That depends on how you define "improve". They've added a ton of features to it over time. Who said minimizing RAM usage was something they are prioritizing right now?
> why are you comparing Claude Code to your editor?
Because the editor does more. All the compute-intensive parts of the agent are in the cloud. Zero reason for an agent harness to require anything beyond a potato to run.
https://fxtwitter.com/trq212/status/2014051501786931427
> Most people's mental model of Claude Code is that "it's just a TUI" but it should really be closer to "a small game engine".