Codex (OpenAI)
by OpenAI
OpenAI’s coding agent: one agent across CLI, IDE extension, desktop app and cloud.
Summary
Codex launched in May 2025 as a cloud software-engineering agent in ChatGPT. It ran in its own sandboxed Linux container per task and was powered by codex-1, a version of OpenAI o3 optimized for software engineering (OpenAI’s launch post and system card). The earlier note of this page said the model derived from o1; that was wrong. It has since become a multi-surface product.
Features
- Surfaces: Codex CLI (local terminal agent, Apache-2.0, open source at github.com/openai/codex; install via script, npm
@openai/codexor Homebrew), IDE extension (VS Code, Cursor, Windsurf), desktop app (Windows, macOS), and Codex web/cloud in ChatGPT. - Cloud tasks in isolated environments; DevDay 2026-09-29 added reusable cloud development environments usable across devices, a refreshed CLI with voice control and an
/agentsview for delegating and monitoring several tasks, code review in the ChatGPT desktop app, and Codex Security Cloud (repo scans plus prepared fixes). - Reads
AGENTS.mdproject instructions (the format OpenAI contributed; see agents-md).
Models
GPT-6.1 Sol was added as the default model in CLI 0.159.1 (2026-09-29). OpenAI’s docs also mention GPT-6 Sol and Luna rolling out at lower token prices than GPT-5.6. Claims about the retirement of dedicated “Codex” models in July 2026 (from a prior research pass) could not be verified.
Version
Codex CLI latest stable in GitHub releases on 2026-09-30: 0.159.2 (2026-09-29); alpha 0.161.0 in progress. Multiple releases a day around DevDay.
Plans
Reported (secondary sources): included in every ChatGPT plan (Free, Go, Plus, Pro with 5x/20x usage levels, Business, Enterprise/Edu); usage is metered against token-based limits, and on 2026-09-29 OpenAI reportedly reopened a higher-usage Pro tier and added a further top tier. Current prices: see OpenAI’s pricing page https://learn.chatgpt.com/docs/pricing.
Sources
- https://openai.com/index/introducing-codex/ and https://openai.com/index/o3-o4-mini-codex-system-card-addendum/ (lineage: codex-1 = o3 variant; via search result text, 2026-09-30)
- https://github.com/openai/codex (2026-09-30)
- https://github.com/openai/codex/releases (2026-09-30)
- https://learn.chatgpt.com/docs (Codex overview, 2026-09-30)
- https://techcrunch.com/2026/09/29/openai-gives-codex-reusable-cloud-environments-that-work-across-devices/ (2026-09-30)
- https://www.morphllm.com/codex-pricing, https://uibakery.io/blog/openai-codex-pricing (secondary, 2026-09-30)