Codex Setup

1. Install Codex

Codex App

If you have not installed Codex App yet, download it here:

https://developers.openai.com/codex/quickstart?setup=app

Codex App also reads from the same local Codex configuration after setup.

VS Code Extension

If you use VS Code, install the official extension from:

https://marketplace.visualstudio.com/items?itemName=openai.chatgpt

The extension uses the same FHRouter Codex settings as the CLI after you configure your local Codex folder.

Codex CLI

If you use the command-line version, install it with:

npm i -g @openai/codex@latest

Codex CLI package URL:
https://www.npmjs.com/package/@openai/codex

FH Switch for the next steps for 1 click setup, or continue below.

Go to FH Switch if you want the desktop 1 click setup flow. Otherwise continue with the manual steps below.

2. Find the Codex configuration folder

First, open your terminal, whether you are on Windows or macOS.

Then run the command for your system to open the Codex configuration folder.

Windows

CMD:

start "" "%USERPROFILE%\.codex"

macOS

open "$HOME/.codex"

Linux or WSL

mkdir -p "$HOME/.codex"
cd "$HOME/.codex"

3. Manually create `config.toml` and `auth.json`, then add the following content

config.toml

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

[model_providers.fhrouter]
name = "fhrouter"
base_url = "https://api.fhrouter.com/v1"
wire_api = "responses"
requires_openai_auth = true

auth.json

{
  "OPENAI_API_KEY": ""
}

4. Enter the ApiKey generated in the dashboard in `OPENAI_API_KEY` inside `auth.json`, then save the file

5. Run `codex` in the terminal and start a conversation to check whether setup succeeded

CLI Model Reminder

After the CLI starts, avoid switching models inside the conversation.
If you already switched models, restart with a command like:

codex -m gpt-5.5 -c model_reasoning_effort="xhigh"

Configuration Reload Reminder

Every time you modify config.toml or auth.json, restart codex for the change to take effect.
This configuration also applies to the VS Code extension version of Codex and to Codex App.