When was codex-1 released?

codex-1 was released by OpenAI on Friday, May 16 2025.

codex-1 was built by OpenAI. Creators of ChatGPT and the GPT series of models. Pioneered large-scale language model research.

Is codex-1 open source?

No. codex-1 is a closed model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms.

What came before and after codex-1?

OpenAI's previous tracked release was o4-mini-high on Apr 16 2025, 30 days earlier. It was followed by codex-mini-latest on May 16 2025.

codex-1

Released May 16 2025

codex-1 is an AI model released by OpenAI on Friday, May 16 2025, 30 days after o4-mini-high.

Compare codex-1 with

codex-1

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About

OpenAI introduced codex-1 in May 2025 to power the Codex cloud agent. Trained from o3 for software engineering, the model could inspect a repository, edit files and run tests in an isolated environment.

Codex users could delegate tasks such as fixing a bug or proposing a patch and review the changes after the agent finished. OpenAI evaluated the shipping configuration at medium reasoning effort.

Frequently asked questions

: codex-1 was released by OpenAI on Friday, May 16 2025.
: codex-1 was built by OpenAI. Creators of ChatGPT and the GPT series of models. Pioneered large-scale language model research.
: No. codex-1 is a closed model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms.
: OpenAI's previous tracked release was o4-mini-high on Apr 16 2025, 30 days earlier. It was followed by codex-mini-latest on May 16 2025.