OpenAI Codex with Ollama

Open models can be used with OpenAI’s Codex CLI through Ollama. Codex can read, modify, and execute code in your working directory using models such as gpt-oss:20b, gpt-oss:120b, or other open-weight alternatives.

Get started

Install Codex CLI:

npm install -g @openai/codex

Start Codex with the --oss flag:

codex --oss

By default, Codex will use the local gpt-oss:20b model.

Note: Codex requires a large context window. We recommend at least 32K tokens. See the documentation for how to adjust context length in Ollama.

Changing models

You can switch to a different model using the -m flag:

codex --oss -m gpt-oss:120b

Cloud models

All models on Ollama Cloud work with Codex.

codex --oss -m gpt-oss:120b-cloud

Learn more

For more detailed setup instructions and configuration options, see the Codex integration guide.