What it does

Codex CLI is a coding agent that lives in your terminal. You type natural language requests; it reads your codebase, proposes edits, runs shell commands, and asks for approval before making changes. It authenticates through your existing ChatGPT plan or an OpenAI API key.

The interesting bit

OpenAI shipped this as Apache-2.0 Rust source with prebuilt musl binaries for Linux and macOS. The “runs locally” framing is slightly generous — it still phones home to OpenAI’s models — but the execution sandbox and file-watching happen on your machine, not in a cloud container.

Key highlights

• Installs via curl, npm, or Homebrew; runs on macOS, Linux, and Windows
• Supports ChatGPT plan authentication (Plus, Pro, Business, etc.) or API key
• Prebuilt static binaries for arm64 and x86_64, musl-linked for Linux portability
• Also available as IDE extensions (VS Code, Cursor, Windsurf) and a desktop app (codex app)
• Licensed Apache-2.0 with an open-source fund mentioned in the docs

Caveats

• The README is thin on architecture details; no mention of local model support or offline operation
• “Runs locally” refers to the CLI client, not the inference — you still need OpenAI API access
• No topics or detailed feature list in the repository metadata, so capabilities beyond “coding agent” are unclear from the source alone

Verdict

Worth a look if you want an AI pair programmer that stays in your terminal workflow rather than your browser. Skip it if you need fully offline operation or deep visibility into how the agent plans and reasons.