Agent harnesses
OpenAI Codex
Coding agent in ChatGPT, the Codex IDE extension, and the Codex CLI
★ 134,668 on GitHub · last commit Nov 10, 2026
What it is
Persistent project context comes from AGENTS.md and AGENTS.override.md instruction files that Codex rebuilds on every run (override wins, then AGENTS.md, then configured fallback filenames such as TEAM_GUIDE.md), supplemented by Skills that teach team standards and workflows.
At a glance
- Vendor
- OpenAI
- Business model
- Open source + paid cloud
- Pricing
- Bundled with ChatGPT plans (Free limited, Go $8/mo, Plus $20/mo, Pro from $100/mo); API usage billed separately pricing page ↗
- License
- Apache-2.0
- Self-hosting
- No, hosted only
- Access
- CLI/IDE/web app
GitHub activity
This product has a public repository, so we read it nightly from the GitHub API. Stars measure developer attention, not quality or market share.
“Lightweight coding agent that runs in your terminal” (repository description)
- Stars
- 134,668
- Forks
- 21,319
- Open issues
- 27,019
- Last commit
- Nov 10, 2026
- License (GitHub)
- Apache-2.0
Links and sources
- Official siteopenai.com/codex
- Pricingchatgpt.com/pricing
- GitHub repositorygithub.com/openai/codex
- Sourcedevelopers.openai.com/codex
- Sourcedevelopers.openai.com/codex/guides/agents-md
Facts verified nov 10, 2026; added nov 10, 2026. Vendor facts come from the vendor’s own pages; benchmark claims are self-reported unless we say otherwise.