Codex
Hand Codex one small bug, then review every change
Use OpenAI's coding agent on a bounded bug with a clear test, and treat its output as a proposal that you read, run and review.
Written from the tool's official pages, listed under Official sources at the end of this guide. Check them for current features, limits and terms.
Try it (opens in a new tab)Steps to try
- Pick a small bug you can reproduce, ideally with a failing test or exact steps to trigger it.
- Work on a new branch or a clean copy of the project so the changes are easy to inspect and discard.
- Describe the bug in plain words: what happens, what should happen, which files you suspect and how to run the tests.
- Read the proposed changes line by line before accepting anything. Ask it to explain any change you do not understand.
- Run the tests yourself, and add a test for the bug if one does not exist.
- Open a pull request and have a person review it, as you would for code written by a colleague.
Limitations
An agent can fix the symptom and miss the cause, change more than you asked, or pass a weak test without solving the problem. Large or vaguely described tasks go worse than small ones. Which interfaces you can use depends on your plan and setup, so check the official page.
Pricing
The official page ties Codex to a ChatGPT account. Plans, usage limits and what is included change, so check the official website for current details.
Privacy and data
Your code and prompts are sent to a service. Check your employer's or client's rules and the provider's data controls before using it on private or licensed code, and keep secrets and credentials out of the project folder you share.
About the sources
The official OpenAI page blocked automated fetching, so its text was collected through a separate public extraction. It describes Codex as an agent for bugs, refactors and features, used across ChatGPT, an editor and the terminal, with pull-request review. The page's performance claims are the vendor's marketing.
Alternatives
OpenCode and other coding agents work in a similar way. For a tiny fix, doing it yourself may be quicker than explaining it.
Official sources
The official pages this guide was written from. Read them for current features, limits and terms.