Codex CLI on Windows 2026: Complete Setup Guide (OpenAI's Coding Agent)

OpenAI's Codex CLI is a strong terminal agent but the setup differs on Windows. Here is what works.

## Codex CLI on Windows 2026: Complete Setup Guide (OpenAI's Coding Agent) OpenAI's Codex CLI brings the coding agent that powers ChatGPT Codex into your terminal. It is open source (Apache-2.0) and sits at 102,900 GitHub stars. Windows setup has a few gotchas - here is the path that works. ## Step 1: Prerequisites - Node.js 20+ (for npm) - Git for Windows (for repo operations) - An OpenAI API key (or ChatGPT Plus subscription for some plans) ## Step 2: Install ```bash npm install -g @openai/codex codex --version ``` ## Step 3: Authenticate ```bash codex login ``` This opens a browser window to authorize with your OpenAI account. On Windows, if the browser does not auto-open, copy the printed URL manually. ## Step 4: Windows-Specific Setup Open a terminal (use Git Bash or Windows Terminal - plain cmd works but Git Bash handles paths better): ```bash codex ``` Then try: "list the files in this directory and summarize the README". ## Windows Troubleshooting | Issue | Fix | |-------|-----| | codex not recognized | Reinstall Node, confirm %APPDATA% pm is in PATH | | Login window won't open | Run codex login --headless and paste the URL | | Path errors on repos | Use Git Bash instead of cmd | | Firewall blocks | Allow Node.js in Windows Defender Firewall | | Slow first run | Codex downloads models/schema on first launch | ## What Codex CLI Does Well - Executes multi-step coding tasks with plan-then-act behavior - Sandboxed command execution (approval prompts) - Reads your whole repo for context - Works with GPT-5-class models via API ## FAQ **Is Codex CLI free?** The CLI is open source. API usage is billed at OpenAI rates; Plus subscribers get limited monthly usage. **Codex CLI vs Claude Code?** Both are terminal agents; Codex is OpenAI-tied, Claude Code is Anthropic-tied. Choose by which model you prefer. **Can it run local models?** No - Codex CLI is designed for OpenAI models.