codex-shim
Local Responses-API shim that exposes Factory BYOK models (and optional ChatGPT GPT-5.5 passthrough) to Codex Desktop.
The Lens
codex-shim is a local proxy that lets Codex Desktop talk to models it was never built to support. OpenAI's Codex app normally locks you into a short list of models. This shim sits between the app and whatever provider you want, translating Codex's Responses API format into calls to Anthropic, DeepSeek, or any generic chat-completion endpoint, with an optional ChatGPT passthrough that reuses your existing subscription. MIT licensed and completely free.
Running it means Python 3.11 or newer, a pip install, and editing a JSON config to point Codex at localhost. On macOS you may also patch the app so your custom models show up in the picker. None of this is hard for someone comfortable in a terminal, but it is fiddly, and it can break when Codex ships an update that changes its internal API.
This is a workaround, not a product. Solo developers who want Claude or DeepSeek inside Codex without paying for a second tool get real value here. Small teams might standardize on it to route through a cheaper model. Larger teams should think hard before depending on an unofficial shim that lives or dies by one maintainer.
The catch is fragility. You are patching around a closed app's limits, so every Codex release is a chance for this to stop working. Use it knowing that.
Free vs Self-Hosted vs Paid
fully freeFree tier: Everything. The shim is MIT licensed and fully open source. There is no paid version.
Self-hosted: Self-hosted by design. It runs as a local proxy on your machine, so the only cost is your own time setting it up and keeping it working across Codex updates.
Paid: None from codex-shim. Your real bill is whatever upstream model you point it at: Anthropic, DeepSeek, OpenAI, or a ChatGPT subscription you reuse via passthrough.
Free and open source under MIT. You still pay for whatever model provider you route through it.
Get tools like this every Wednesday
One featured tool, three on the radar. No fluff.
License: MIT License
Use freely, including commercial. Just keep the license.
Commercial use: ✓ Yes
About
- Owner
- 0xSero (User)
- Stars
- 491
- Forks
- 41
Explore Further
More tools in the directory
openclaw
Your own personal AI assistant. Any OS. Any Platform. The lobster way. 🦞
373.3k ★claw-code
The repo is finally unlocked. enjoy the party! The fastest repo in history to surpass 100K stars ⭐. Join Discord: https://discord.gg/5TUQKqFWd Built in Rust using oh-my-codex.
192.0k ★everything-claude-code
The agent harness performance optimization system. Skills, instincts, memory, security, and research-first development for Claude Code, Codex, Opencode, Cursor and beyond.
191.2k ★