> For the complete documentation index, see [llms.txt](https://docs.nuvolos.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nuvolos.com/how-to-guides/application-specific-guides/openai-codex.md).

# OpenAI Codex

The [Codex CLI](https://github.com/openai/codex) Nuvolos application enables you to install OpenAI's open-source Agent with one click. It is based on the Terminal application and supports long-running sessions.

## Authentication

Codex CLI supports using an existing API key directly, which means it's enough to configure the `OPENAI_API_KEY` environment variable to use the application. We recommend to use [Nuvolos secrets](/reference/configuration/environment-variables-and-secrets.md) to store the API key securely.

By using space-level secrets, you can define a shared API key for everyone to use in a specific Nuvolos project.

## Configuration files

Codex CLI stores your user configurations in your HOME folder, in a `.codex` subfolder.