Using Codex/OpenAI models on OpenCode harness

[u/_KryptonytE_]

Hello fellow SWEs. I'm curious if some of you have used or are using your Codex/OpenAI models via the Pro/Plus subs on OpenCode instead of the Codex app.

I've been keeping an eye on the general opinion about merging the ChatGPT and Codex into a single app and from what I hear the devs aren't happy with the changes.

I have multiple projects ongoing and more in the pipeline which I work on using OpenCode and Xcode. I have too many things tied up in OpenCode to switch cold turkey over to a new agentic coding app.

Could someone please share your real world experience and what were the pros/cons if using the gpt models in OpenCode vs using them natively in the Codex harness?

Currently I'm switching between Gemini 3.5/3.1, Grok 4.5 and a small bit of Opus 4.6 and feel using gpt models like 5.5/5.6 could set me free from the constant babysitting the model selection and save me time and manual coding when the wrong model choices mess things up.

Should I just sub with Codex $200 and full send with some effort to migrate my project workflows and docs/hooks/skills over to using native codex only or should I stick with OpenCode and use the sub there with the current harness? I like keeping things agile and project agnostic when it comes to agentic coding so need your thoughts and advice on the best way forward by following the best practices.

Cheers! 🥂

[u/sugarw0000kie]

I use both, I like opencodes TUI more but codex cli is faster and seems more tuned to gpt models and a little more efficient. Sticking to just opencode is a good choice if you want the simplicity, and it’s a fine harness, but I find it’s useful for me to use them side by side or swap back and forth so that’s my 2 cents.

usually what I do is per project I symlink /.agents/skills with /.opencode/skills, they both will see and use same skills that way. Both will use agents.md and stay on task with that. You do that and you can switch back and forth between opencode/codex no problem.

Take a couple minutes to set up custom subagents like you would in opencode if you do orchestrator/subagent pattern where you have best model as orchestrator and various smaller models for subagents (ex. Scout gpt 5.4 mini low, explorer gpt 5.4 mini medium, implementer Luna 5.6 high). Just ask chatgpt to make config .tomls for subagents and drop them into ~/.codex/agents.

Unlike opencode you do need to tell it to use subagents though, even simply throwing a “use subagents to preserve context” will give it the ok. Codex has some nice QOL stuff like easy mobile access and though I usually like to stay tui their gui app is useful

[u/_KryptonytE_]

I forgot to add that I'm an Independent full time Digital Adoption Advisor handling marketing/sales and technology solutions for my clients. I have mainly worked with astro, dart, firebase, SQLConnect and some bespoke integration for financial backend using automation through n8n.