Walkthrough

Install and Authenticate

Codex CLI on macOS / Linux, signing in, picking a model.

Steps · 0 / 3 done

Install via npm
Install the Codex CLI globally.
```
npm install -g @openai/codex
```
Verify`codex --version` prints a version.
Authenticate
Run codex once. It will open a browser for sign-in. Or set OPENAI_API_KEY in your shell if you prefer key-based auth.
```
codex
```
VerifyAfter auth, the prompt shows your account and current model.
Pick a model for mobile work
Newer reasoning-tier models are best for app scaffolding; mid-tier for iteration. You can switch mid-session.
```
/model gpt-codex
```
VerifyThe prompt confirms the new model. Ask any question; the model name appears in the response header.

Check your understanding

Q1. Two valid ways to authenticate with Codex are…

· Tick off the 3 step(s) above.

· Score 100% on the quiz.