Codex Manual

What Is Codex

Codex is a coding agent that can enter your development environment, read files, edit code, and run commands.

Codex is OpenAI's coding agent for software development. It can inspect a project, run commands, edit files, add tests, explain errors, review changes, and help you move from a goal to verified code.

It is best understood as an assistant that can use developer tools. You describe the target, Codex explores the project, proposes a plan, edits files when appropriate, and runs checks.

Good Uses

• Explain an unfamiliar repository.
• Find likely causes of a bug.
• Edit code, add tests, and update docs.
• Review code before a commit or pull request.
• Break a larger request into verifiable steps.
• Try local or cloud workflows in parallel.

Boundaries

Codex can run commands and change files, so it should not be treated as an unrestricted executor.

Avoid using it for production systems, sensitive credentials, broad refactors without tests, or full-access mode in repositories you do not understand.

Three Concepts

Start with:

1. Surface: CLI, App, IDE Extension, or Web/Cloud.
2. Environment: the operating system and project directory Codex runs in.
3. Permissions: what Codex can read, write, and execute.