Codex in a Minute: Getting started

In one sentence

Codex is OpenAI’s agentic coding tool for working in a repository with instructions, tasks, and executable checks.

Why it matters

Suggestion-only assistants stop at drafts. A coding agent that can navigate a repo and apply changes can finish delivery work—if you specify outcome and verification.

How it works

A solid first Codex session usually includes:

1. opening the correct project directory;
2. confirming AGENTS.md (or equivalent) exists;
3. stating outcome, constraints, and verification;
4. reviewing the resulting diff before merge.

Install steps, auth, and CLI flags change. Use current OpenAI Codex documentation for setup details.

Example

Add pagination to the /items JSON endpoint.
Do not change auth middleware.
Verify with the existing API tests.
Summarize files changed when done.

Agentic coding use

Treat Codex like a junior engineer with fast hands: clear tickets beat clever vibes. Your first hour should establish repo instructions and a repeatable task template.

Watch out

Do not start by asking Codex to “improve architecture.” Start with one observable outcome and one gate. Expand scope only after the loop works.