Run OpenAI Codex with Open-Source and Local Models (OSS Mode)

Melvin Vivas · X post · 2026-06-17 · Open on X

Topics: AI Dev Tools & Productivity, LLM Fundamentals · Level: intermediate

Summary

The OpenAI Codex App, CLI and SDK aren't limited to OpenAI models. You can set them up to use any open-source model through local providers. The setup is covered in the Codex advanced-configuration docs, in the 'OSS mode / local providers' section.

Key points

• The Codex App, CLI and SDK all work with open-source models, not just OpenAI models.
• Setup lives in the Codex advanced-configuration docs, in the 'OSS mode - local providers' section.
• This lets you run Codex on locally hosted models, which can help with cost and privacy and lets you experiment with different models.
• The tip comes from Tibo (@thsottiaux) at OpenAI.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more
• Codex Advanced Configuration – OSS mode / local providers · docs · developers.openai.com · free
  Official docs on setting up Codex to run with open-source models through local providers.
• Tibo (@thsottiaux) · person · x.com · free
  X account of the OpenAI Codex team member who posts Codex updates and usage-limit announcements.
  Also in: Codex Tip: Ask Codex to Organize Your Recent Chats (Melvin Vivas on X · notes), An X research bot built with Hermes (Melvin Vivas on X · notes), Why Codex Usage Drains Faster: Prompt Cache Hit Rate (Melvin Vivas on X · notes), Codex safeguards against accidental destructive actions (Melvin Vivas on X · notes) and 1 more

Try this

• Read the Codex OSS-mode docs and set up Codex CLI with a local open-source model provider.