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".
> -> layouts elements
> -> rasterizes them to a 2d screen
> -> diffs that against the previous screen
> -> finally uses the diff to generate ANSI sequences to draw
Yup. Overengineering.
This minimizes screen flash. You can't rely on terminals doing double-buffering.
[1] https://github.com/emacs-mirror/emacs/blob/c29071587c64efb30... or a more user-friendly overview, Daniel Colascione's seminal "Buttery Smooth Emacs", snapshotted at e.g. https://gist.github.com/ghosty141/c93f21d6cd476417d4a9814eb7...
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.
An upvote well earned.
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.
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.
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.
> 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.
Ratatouille rust cli lib will be a good start.
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.
1. Maintains an internal representation of what the game thinks is on screen.
2. Runs the game for one frame which updates that representation.
3. Generates a diff to see how that differs from what's actually on screen.
4. Executes the minimum set of draw calls to get the screen to match the internal representation.
It's really not that hard. It's a few hundred lines of code.
> -> rasterizes them to a 2d screen
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.
It will be _glorious_ (and profoundly stupid)
I built a truly glyph based instanced quad system to render millions of characters in space at once.
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???
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.
That’s rather sickening.
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).
If they're doing anything else, the word "rasterizing" is being misused.
What is this?
not that it could be leaner for sure but i get the reasoning behind the tui rendering layer
i'd be ashamed of publishing software with this level of polish as a solo dev, let alone as the hottest multibillion startup on the planet
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.
Other than that I agree with you.
For company with that much AI you'd think if it was actually good, doing that part in fast and performant way would be "easy"
