Configure a model provider for Codex

Connect Flatrouter to Codex CLI with CC Switch, and pick models that support the Responses protocol.

The easiest route is CC Switch, an open-source provider manager with a visual UI. No hand-edited JSON, no environment variables.

1. Install CC Switch

macOS

brew install --cask cc-switch

Or download the .dmg from Releases and install it manually.

Windows

Download the .msi installer from Releases.

Linux

# Debian / Ubuntu
sudo dpkg -i CC-Switch-*.deb

# Fedora / RHEL
sudo rpm -i CC-Switch-*.rpm

# AppImage
chmod +x CC-Switch-*.AppImage && ./CC-Switch-*.AppImage

Requires macOS 12+, Windows 10+, or Ubuntu 22.04+ / Debian 11+ / Fedora 34+.

2. Add the provider

Step 1: create a provider

Switch to the Codex tab at the top, then click the + button in the top right.

Step 2: fill in the details

Fill in the fields below, then click + Add.

Field	Value	Notes
❶ Provider name	`flatrouter-codex`	Anything you like — it is just a label
❷ Website	`https://flatrouter.com`	The provider's site
❸ API key	Your Flatrouter API key	From Console → API Keys
❹ Base URL	`https://api.flatrouter.com/v1`	No trailing slash
❺ API format	`OpenAI Compatible`	Pick the OpenAI-compatible format
❻ Write to global config	✅ Ticked	Applies the config to every project

CC Switch writes the config file for you — no file editing required.

Back in the list, select flatrouter-codex and click Use. A "switched successfully" toast means you are done. With Write to global config ticked, the settings land in config.toml automatically.

3. Verify

codex "Hi, tell me about yourself"

A normal AI response means the setup worked.

4. Choosing a model

codex --model <model-id> "Refactor this function"

Mind the Responses protocol

Codex CLI uses the OpenAI Responses API (wire_api = "responses"), and not every model supports that format. Before picking one, check the Flatrouter model list to confirm the model supports Responses, otherwise the request will fail.

Troubleshooting

Q: "Authentication error"

Check that the API key is filled in correctly and that the base URL has no trailing slash.

Q: Connection timeouts

Make sure the base URL is exactly https://api.flatrouter.com/v1, with no trailing slash.