Codex
BuildersCoding agentOpenAI
OpenAI's software engineering agent, available as a CLI, IDE extension and cloud agent inside ChatGPT.
- Who it's for: people building software and AI agents
- Pricing: Included with ChatGPT Plus/Pro/Business plans (verify on the official site)
- Official site: https://openai.com/codex/
- Source / changelog: https://developers.openai.com/codex
Best for / Not for
Best for
- ChatGPT subscribers who want a coding agent at no extra subscription
- Delegating well-scoped tasks to a cloud agent
- Terminal-first developers
Not for
- Non-developers
- Codebases you are not allowed to share with OpenAI
3 concrete use cases
- Delegate a bug fix: "Find why the CSV export drops the last row, fix it and add a regression test."
- Code review: Ask Codex to review a branch and list risky changes before you open a PR.
- Scaffold a feature: "Add a /health endpoint that checks the database and returns JSON status."
Pros and cons
Pros
- Included with paid ChatGPT plans
- CLI, IDE extension and cloud agent share one account
- Open-source CLI
Cons
- Usage limits depend on plan
- Cloud tasks need your repo connected
- Output still needs human review
How to get started with Codex in 10 minutes
- Install the CLI: npm install -g @openai/codex (or brew install --cask codex)
- Run codex in a project folder
- Sign in with your ChatGPT account
- Ask it to explain the repo
- Give one small, testable task
Comparisons
Codex alternatives
- Claude Code: Agentic coding tool that runs in the terminal and IDEs, reads a codebase and makes multi-file edits.
- Devin: Autonomous AI software engineer that works on tickets in its own cloud environment.
- Cline: Open-source autonomous coding agent extension for VS Code.
- Aider: Open-source AI pair programming in the terminal that edits files in your git repo.
- Gemini CLI: Open-source AI agent that brings Gemini into the terminal.
Recent changes
Weekly updates for Codex will be logged here as they appear in issues.