OpenAI Codex

What OpenAI Codex does

Codex is OpenAI's software engineering agent, available as a command line tool, an editor extension, and a cloud service that works on tasks in its own sandboxed environment. Given a task it explores the repository, writes code, runs tests and returns a diff or opens a pull request. The cloud mode is designed for delegating several tasks in parallel and reviewing results later, while the local modes keep work on your machine with approval prompts before commands run. It integrates with GitHub for code review and can be driven from chat interfaces. It suits developers already paying for an OpenAI subscription and teams that want tasks handled asynchronously. The limitations are environment setup and verification: cloud tasks need their dependencies configured to be useful, results vary with how precisely the task was specified, and output still requires the same review as any other contribution.

How to use it

Install the command line tool through your package manager, run it in a project, and sign in with a paid OpenAI account; usage is included in subscription tiers with additional capacity available through the API. Start locally rather than in the cloud, with a contained task such as fixing a failing test, so you can watch how it proposes commands and approve them. Choose the approval mode deliberately: fully automatic execution is convenient and risky, and read-only mode is the safe way to evaluate. For cloud tasks, connect the repository and define the environment setup, including dependency installation, because a task that cannot install or run tests will produce plausible but unverified code. Write task descriptions the way you would write a ticket, with acceptance criteria, since precision matters more here than in interactive chat. Expect to review every diff, and keep tasks small enough that a rejected result costs minutes rather than a day.

Best for

• delegated tasks
• test fixing
• parallel work
• pull request generation
• sandboxed execution

Strengths and limitations