Codex Setup Guide

This guide shows how to install OpenAI Codex on macOS and Windows, then connect it to Let AI Run.

1. Prepare Your API Key

Prepare a valid Let AI Run key first (typically starts with sk-). You will place it in auth.json.

2. Install on macOS

• Codex APP

Official website download：https://chatgpt.com/codex

• Codex Cli

brew install codex

If Node.js is already installed, you can also install with npm:

npm install -g @openai/codex

3. Configure on macOS

Create the hidden config directory first:

mkdir -p ~/.codex

Create ~/.codex/config.toml with:

model_provider = "letairun"
model = "gpt-5.5"
model_reasoning_effort = "xhigh"
disable_response_storage = true
network_access = "enabled"
model_verbosity = "high"

[model_providers.letairun]
name = "letairun"
base_url = "https://api.letai.run/v1"
wire_api = "responses"
requires_openai_auth = true

[features]
fast_mode = false
prevent_idle_sleep = true
streamable_shell = false

Create ~/.codex/auth.json:

{
  "OPENAI_API_KEY": "your-api-key-here"
}

Replace your-api-key-here with your real API key.

4. Install on Windows

• Codex APP

Official website download：https://chatgpt.com/codex

• Codex Cli

1. Install Node.js: https://nodejs.org/zh-cn/download/current
2. Install Codex:

npm install -g @openai/codex

5. Configure on Windows

Create this folder (note the leading .):

• %USERPROFILE%\\.codex\\

Create %USERPROFILE%\\.codex\\config.toml:

model_provider = "letairun"
model = "gpt-5.5"
model_reasoning_effort = "xhigh"
disable_response_storage = true
network_access = "enabled"
windows_wsl_setup_acknowledged = true
model_verbosity = "high"

[model_providers.letairun]
name = "letairun"
base_url = "https://api.letai.run/v1"
wire_api = "responses"
requires_openai_auth = true

[features]
fast_mode = false
prevent_idle_sleep = true
streamable_shell = false

Create %USERPROFILE%\\.codex\\auth.json:

{
  "OPENAI_API_KEY": "your-api-key-here"
}

6. How To Start

• Terminal: run codex
• VSCode / Cursor: install the official OpenAI Codex extension

7. Troubleshooting

1. codex command not found:
   • Confirm installation completed successfully.
   • If installed via npm, make sure the global npm bin path is in PATH.
2. Authentication failed:
   • Check auth.json file name and location.
   • Make sure OPENAI_API_KEY is your real key, not the placeholder.
3. Requests are not routed to Let AI Run:
   • Verify base_url is https://api.letai.run/v1 in config.toml.