OpenAI Codex engineering lead Thibault Sottiaux says Codex tools can now be configured to run any open-source model
Story Overview
OpenAI's Codex tools have gained the ability to connect with any open-source model through local endpoints, letting users bypass exclusive reliance on OpenAI-hosted options and instead point the App, CLI, and SDK at self-hosted setups like Ollama or LM Studio.
Routing traffic to custom providers
A simple CLI flag or config file tweak now directs Codex traffic to local servers or compatible third-party endpoints, with built-in support for common providers and custom definitions for base URLs and headers.
Unified tooling across model types
Developers gain the option to blend local open-source models with hosted ones inside the same agentic coding workflows, though exact rollout timing and adoption numbers remain unspecified in current documentation.
Many users praised OpenAI Codex tools for supporting any open source model through local providers because of the added flexibility and openness, while others criticized bizarre configuration and limited Linux access.
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@thsottiaux Hey Tibo, is it possible to set up a hybrid approach in Codex where we use GPT models as architects and open source models as executors?
I'm trying to get it working, but it seems Codex expects the same tool-calling protocol from other models, which they don’t have.
How’s glm in the codex harness
Reminder that you can use the Codex App, CLI and SDK with any open source model, not just with OpenAI models.
https://developers.openai.com/codex/config-advanced#oss-mode-local-providers

@FilipBaturan @thsottiaux Yes! You can edit Codex CLI and build whatever routing layer you want.
I use a Custom Pi setup called Takomi: GPT orchestrates, other models execute. It’s my hybrid architect/worker flow. Happy to keep improving it with others: https://github.com/J-StaR-Films-Studios/VibeCode-Protocol-Suite

@thsottiaux Can I use a GPT model to orchestrate other models as subagents?

@thsottiaux If you want to use third-party models in Chat Completions format with Codex(which is very common like DeepSeek), feel free to give CC Switch a try😜 https://www.ccswitch.io/en/tutorials/codex-deepseek-routing-guide
TIL you can use open-source models in codex
Reminder that you can use the Codex App, CLI and SDK with any open source model, not just with OpenAI models.
https://developers.openai.com/codex/config-advanced#oss-mode-local-providers

@thsottiaux And also we can use chatgpt pro for planning and codex or any other harness for implementation or go full rampage with chatgpt

@thsottiaux

@bxsck_ @thsottiaux Yes you can, I've done this many times. Once you add model provider and model/name, you can use it in agent toml file. Ask Codex to do it for you.

@FilipBaturan @thsottiaux You should try this , i built it exactly for this workflow

@thsottiaux @thsottiaux please fix windows codex app

@thsottiaux Wow, how did I not know this. Thanks Tibo

@FilipBaturan @thsottiaux Yes sure, just set up codex app itself with the openai frontier model, then tell it to spawn codex cli with the models of your choice for work. In fact, just put this post and yours into codex now and tell it to write a good AGENTS.md that will do this, job done

@thsottiaux It can be configured globally, but it can’t be mixed. In one case, I want to use GPT-5.5 as the main intelligence model, while using another provider for subagents. In another case, I want to use 2 different providers, neither of which is OpenAI. not enough flexibility.

@FilipBaturan @thsottiaux not so well and efficient as it would be with say @opencode . just use codex as the architect, write a tasks.md file and then execute with opencode and any agent you like

@thsottiaux opensource codex please

@thsottiaux The model picker on desktop doesn’t show external provider models atm due to a bug.

@trashpandaemoji @thsottiaux https://github.com/0xSero/codex-shim

@thsottiaux Who would want to? Codex is such a unusable buggy mess on windows - and I have a i7, 32gb ram ssd.

@thsottiaux 这个意思是我可以在 codex 中使用 deepseek?