I did some debugging on this today. The results are... sobering.

Memory comparison of AI coding CLIs (single session, idle):

  | Tool        | Footprint | Peak   | Language      |
  |-------------|-----------|--------|---------------|
  | Codex       | 15 MB     | 15 MB  | Rust          |
  | OpenCode    | 130 MB    | 130 MB | Go            |
  | Claude Code | 360 MB    | 746 MB | Node.js/React |

vmmap shows Claude Code reserves 32.8 GB virtual memory just for the V8 heap, has 45% malloc fragmentation, and a peak footprint of 746 MB that never gets released, classic leak pattern.

On my 16 GB Mac, a "normal" workload (2 Claude sessions + browser + terminal) pushes me into 9.5 GB swap within hours. My laptop genuinely runs slower with Claude Code than when I'm running local LLMs.

I get that shipping fast matters, but building a CLI with React and a full Node.js runtime is an architectural choice with consequences. Codex proves this can be done in 15 MB. Every Claude Code session costs me 360+ MB, and with MCP servers spawning per session, it multiplies fast.

There’s nothing wrong with that, except it lets ai skeptics feel superior

Sounds like a web developer defined the solution a year before they knew what the problem was.

Same with opencode and gemini, it's disgusting

Codex (by openai ironically) seems to be the fastest/most-responsive, opens instantly and is written in rust but doesn't contain that many features

Claude opens in around 3-4 seconds

Opencode opens in 2 seconds

Gemini-cli is an abomination which opens in around 16 second for me right now, and in 8 seconds on a fresh install

Codex takes 50ms for reference...

--

If their models are so good, why are they not rewriting their own react in cli bs to c++ or rust for 100x performance improvement (not kidding, it really is that much)

React's core is agnostic when it comes to the actual rendering interface. It's just all the fancy algos for diffing and updating the underlying tree. Using it for rendering a TUI is a very reasonable application of the technology.

Is this a react feature or did they build something to translate react to text for display in the terminal?

It’s really not that crazy.

React itself is a frontend-agnostic library. People primarily use it for writing websites but web support is actually a layer on top of base react and can be swapped out for whatever.

So they’re really just using react as a way to organize their terminal UI into components. For the same reason it’s handy to organize web ui into components.

Also explains why Claude Code is a React app outputting to a Terminal. (Seriously.)

Who cares, and why?

All of the major providers' CLI harnesses use Ink: https://github.com/vadimdemedes/ink