AI-assisted development has moved from IDE plugins and browser-based chatbots to terminal-native agents that operate where engineers already live: the command line. OpenAI Codex CLI breaks from that model. It is an open-source, terminal-first coding agent that reads an existing codebase, proposes multi-file changes, and executes commands autonomously within a sandboxed environment.

How to Set Up and Use OpenAI Codex CLI

Install Node.js 22+ and verify with node --version .

Run npm install -g @openai/codex@<version> to install Codex CLI globally.

Set your OPENAI_API_KEY securely using read -rs , direnv, or a secrets manager.

Initialize a Git repository and create a dedicated branch for agent work.

Configure global defaults in ~/.codex/config.yaml and project conventions in codex.md .

Execute your first prompt in suggest mode: codex -- "your task description" .

Review the proposed diffs in the terminal and approve, reject, or refine each change.

Escalate to auto-edit or full-auto mode on trusted,…