3 posts tagged “codex-cli”
OpenAI's Codex CLI tool, not the same thing as Codex cloud.
2025
Load Llama-3.2 WebGPU in your browser from a local folder (via) Inspired by a comment on Hacker News I decided to see if it was possible to modify the transformers.js-examples/tree/main/llama-3.2-webgpu Llama 3.2 chat demo (online here, I wrote about it last November) to add an option to open a local model file directly from a folder on disk, rather than waiting for it to download over the network.
I posed the problem to OpenAI's GPT-5-enabled Codex CLI like this:
git clone https://github.com/huggingface/transformers.js-examples
cd transformers.js-examples/llama-3.2-webgpu
codex
Then this prompt:
Modify this application such that it offers the user a file browse button for selecting their own local copy of the model file instead of loading it over the network. Provide a "download model" option too.
Codex churned away for several minutes, even running commands like curl -sL https://raw.githubusercontent.com/huggingface/transformers.js/main/src/models.js | sed -n '1,200p' to inspect the source code of the underlying Transformers.js library.
After four prompts total (shown here) it built something which worked!
To try it out you'll need your own local copy of the Llama 3.2 ONNX model. You can get that (a ~1.2GB) download) like so:
git lfs install
git clone https://huggingface.co/onnx-community/Llama-3.2-1B-Instruct-q4f16
Then visit my llama-3.2-webgpu page in Chrome or Firefox Nightly (since WebGPU is required), click "Browse folder", select that folder you just cloned, agree to the "Upload" confirmation (confusing since nothing is uploaded from your browser, the model file is opened locally on your machine) and click "Load local model".
Here's an animated demo (recorded in real-time, I didn't speed this up):
I pushed a branch with those changes here. The next step would be to modify this to support other models in addition to the Llama 3.2 demo, but I'm pleased to have got to this proof of concept with so little work beyond throwing some prompts at Codex to see if it could figure it out.
According to the Codex /status command this used 169,818 input tokens, 17,112 output tokens and 1,176,320 cached input tokens. At current GPT-5 token pricing ($1.25/million input, $0.125/million cached input, $10/million output) that would cost 53.942 cents, but Codex CLI hooks into my existing $20/month ChatGPT Plus plan so this was bundled into that.
If you've been experimenting with OpenAI's Codex CLI and have been frustrated that it's not possible to select text and copy it to the clipboard, at least when running in the Mac terminal (I genuinely didn't know it was possible to build a terminal app that disabled copy and paste) you should know that they fixed that in this issue last week.
The new 0.20.0 version from three days ago also completely removes the old TypeScript codebase in favor of Rust. Even installations via NPM now get the Rust version.
I originally installed Codex via Homebrew, so I had to run this command to get the updated version:
brew upgrade codex
Another Codex tip: to use GPT-5 (or any other specific OpenAI model) you can run it like this:
export OPENAI_DEFAULT_MODEL="gpt-5"
codex
This no longer works, see update below.
I've been using a codex-5 script on my PATH containing this, because sometimes I like to live dangerously!
#!/usr/bin/env zsh
# Usage: codex-5 [additional args passed to `codex`]
export OPENAI_DEFAULT_MODEL="gpt-5"
exec codex --dangerously-bypass-approvals-and-sandbox "$@"
Update: It looks like GPT-5 is the default model in v0.20.0 already.
Also the environment variable I was using no longer does anything, it was removed in this commit (I used Codex Web to help figure that out). You can use the -m model_id command-line option instead.
openai/codex. Just released by OpenAI, a "lightweight coding agent that runs in your terminal". Looks like their version of Claude Code, though unlike Claude Code Codex is released under an open source (Apache 2) license.
Here's the main prompt that runs in a loop, which starts like this:
You are operating as and within the Codex CLI, a terminal-based agentic coding assistant built by OpenAI. It wraps OpenAI models to enable natural language interaction with a local codebase. You are expected to be precise, safe, and helpful.
You can:
- Receive user prompts, project context, and files.
- Stream responses and emit function calls (e.g., shell commands, code edits).
- Apply patches, run commands, and manage user approvals based on policy.
- Work inside a sandboxed, git-backed workspace with rollback support.
- Log telemetry so sessions can be replayed or inspected later.
- More details on your functionality are available at codex --help
The Codex CLI is open-sourced. Don't confuse yourself with the old Codex language model built by OpenAI many moons ago (this is understandably top of mind for you!). Within this context, Codex refers to the open-source agentic coding interface. [...]
I like that the prompt describes OpenAI's previous Codex language model as being from "many moons ago". Prompt engineering is so weird.
Since the prompt says that it works "inside a sandboxed, git-backed workspace" I went looking for the sandbox. On macOS it uses the little-known sandbox-exec process, part of the OS but grossly under-documented. The best information I've found about it is this article from 2020, which notes that man sandbox-exec lists it as deprecated. I didn't spot evidence in the Codex code of sandboxes for other platforms.