Codex Shim BYOK Models

Skill by ara.so — Codex Skills collection.

Overview

codex-shim is a local Python API shim that intercepts Codex Desktop's model requests and routes them to:

• Any model in your ~/.factory/settings.json (Factory BYOK)
• Your ChatGPT subscription GPT-5.5
• Custom OpenAI/Anthropic/generic chat completion endpoints

It exposes a local Responses API endpoint that Codex Desktop points to, bypassing Codex's server-side Statsig model allowlist.

Key capabilities:

• Use any OpenAI, Anthropic, DeepSeek, Gemini, OpenRouter, or Z.ai model
• Keep ChatGPT subscription GPT-5.5 alongside BYOK models
• No modification to ~/.codex/config.toml (uses launch-time overrides)
• Translates between Codex Responses API ↔ upstream APIs (OpenAI chat completions, Anthropic messages)