OpenAI Codex CLI: Terminal-First Coding Agent Tutorial (2026)SitePoint Team

Share this article 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 op

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Share this article 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 1. Install Node.js 22+ and verify with node --version. 2. Runnpm install -g @openai/codex@ to install Codex CLI globally. 3. Set your OPENAI_API_KEY securely using read -rs, direnv, or a secrets manager. 4. Initialize a Git repository and create a dedicated branch for agent work. 5. Configure global defaults in ~/.codex/config.yaml and project conventions in codex.md. 6. Execute your first prompt in suggest mode: codex -- "your task description". 7. Review the proposed diffs in the terminal and approve, reject, or refine each change. 8. Escalate to auto-edit or full-auto mode on trusted, version-controlled projects once comfortable. Table of Contents * Why Codex CLI Is the Terminal-First Coding Agent Yo