Great question, and my guess:

If you build React in C++ and Rust, even if the framework is there, you'll likely need to write your components in C++/Rust. That is a difficult problem. There are actually libraries out there that allow you to build web UI with Rust, although they are for web (+ HTML/CSS) and not specifically CLI stuff.

So someone needs to create such a library that is properly maintained and such. And you'll likely develop slower in Rust compared to JS.

These companies don't see a point in doing that. So they just use whatever already exists.

Opencode wrote their own tui library in zig, and then build a solidjs library on top of that.

https://github.com/anomalyco/opentui

This has nothing to do with React style UI building.

I am referring to your comment that the reason they use js is because of a lack of tui libraries in lower level languages, yet opencode chose to develop their own in zig and then make binding for solidjs.

Those Rust libraries have existed for some time:

- https://github.com/ratatui/ratatui

- https://github.com/ccbrown/iocraft

- https://crates.io/crates/dioxus-tui

Where is React? These are TUI libraries, which are not the same thing

iocraft and dioxus-tui implement the React model, or derivatives of it.

Looking at their examples, I imagine people who have written HTML and React before can't possibly use these libraries without losing their sanity.

That's not a criticism of these frameworks -- there are constraints coming from Rust and from the scope of the frameworks. They just can't offer a React like experience.

But I am sure that companies like Anthropic or OpenAI aren't going to build their application using these libraries, even with AI.

and why do they need react...

Is this accurate? I've been coding UIs since the early 2000s and one-way data binding has always been a thing, especially in the web world. Even in the heyday of jQuery, there were still good (but much less popular) libraries for doing it. The idea behind it isn't very revolutionary and has existed for a long time. React is a paradigm shift because of differential rendering of the DOM which enabled big performance gains for very interactive SPAs, not because of data binding necessarily.

Well said.

Why does it matter if Claude Code opens in 3-4 seconds if everything you do with it can take many seconds to minutes? Seems irrelevant to me.

I guess with ~50 years of CPU advancements, 3-4 seconds for a TUI to open makes it seem like we lost the plot somewhere along the way.

Don’t forget they’ve also publicly stated (bragged?) about the monumental accomplishment of getting some text in a terminal to render at 60fps.

Some people[0] like their tools to be well engineered. This is not unique to software.

[0] Perhaps everyone who actually takes pride in their craft and doesn’t prioritise shitty hustle culture and making money over everything else.

Aside from startup time, as a tool Claude Code is tremendous. By far the most useful tool I’ve encountered yet. This seems to be very nit picky compared to the total value provided. I think y'all are missing the forrest for the trees.

Most of the value of Claude Code comes from the model, and that's not running on your device.

The Claude Code TUI itself is a front end, and should not be taking 3-4 seconds to load. That kind of loading time is around what VSCode takes on my machine, and VSCode is a full blown editor.

It’s orders of magnitude slower than Helix, which is also a full blown editor.

When all your other tools are fast and well engineered, slow and bloated is very noticeable.

It’s almost all the model. There are many such tools and Claude Code doesn’t seem to be in any way unique. I prefer OpenCode, so far.

Because when the agent is taking many seconds to minutes, I am starting new agents instead of waiting or switching to non-agent tasks

This is exactly the type of thing that AI code writers don't do well - understand the prioritization of feature development.

Some developers say 3-4 seconds are important to them, others don't. Who decides what the truth is? A human? ClawdBot?

The humans in the company (correctly) realised that a few seconds to open basically the most powerful productivity agent ever made so they can focus on fast iteration of features is a totally acceptable trade off priority wise. Who would think differently???

This is my point...

You kinda suggested the opposite

> Some developers say 3-4 seconds are important to them, others don't.

Wasnt GTA 5 famous for very long start up time and turns out there some bug which some random developer/gamer found out and gave them a fix?

Most Gamers didnt care, they still played it.

Codex team made the right call to rewrite its TypeScript to Rust early on

codex cli is missing a bunch of ux features like resizing on terminal size change.

Opencode's core is actually written in zig, only ui orchestration is in solidjs. It's only slightly slower to load than neo-vim on my system.

https://github.com/anomalyco/opentui

50ms to open and then 2hrs to solve a simple problem vs 4s to open and then 5m to solve a problem, eh?

lol right? I feel like I’m taking crazy pills here. Why do people here want to prioritise the most pointless things? Oh right it’s because they’re bitter and their reaction is mostly emotional…

The "50ms" number was measured by me and you can literally try it on your system as well. it will likely be faster than 50ms

Do you have a proof that gpt-5.2 or 5.3 codex takes 2 hours for the same problem that sonnet/opus4.5/4.6 take 5 minutes to solve? (I use both anthropic and openai models daily almost equally, and i'm not relating to what you said)

Sure codex-cli lacks way-too many features compared to claude-code (I use opencode), but your statement implies that openai models are absolute garbage (2h vs 5m to solve a problem)