Connect Codex through LiteLLM

Codex CLI speaks only the OpenAI Responses API. The Fortytwo API serves Chat Completions, so Codex connects through a local LiteLLM proxy that translates between the two. This setup needs Python and a terminal.

Before you start: create a Fortytwo API key and buy credits — see Quickstart, step 1. Give each agent its own key with a Spend limit.

Setting	Value
Base URL	`https://api.fortytwo.network/v1`
Model ID	`qwen/qwen3.8-27b`

Install LiteLLM and Codex

pip install "litellm[proxy]"
npm install -g @openai/codex

Configure LiteLLM

Create litellm.yaml:

litellm.yaml

model_list:
  - model_name: qwen/qwen3.8-27b
    litellm_params:
      model: custom_openai/qwen/qwen3.8-27b
      api_base: https://api.fortytwo.network/v1
      api_key: os.environ/FORTYTWO_API_KEY

general_settings:
  master_key: os.environ/LITELLM_MASTER_KEY

Use the custom_openai/ prefix: it makes LiteLLM translate Responses requests to Chat Completions.The master key is a password for your local LiteLLM proxy; LiteLLM does not start without it. You do not get it anywhere: make up any string that starts with sk-, or let the command in the next step create a random one. Codex sends it to LiteLLM; LiteLLM sends your Fortytwo key to Fortytwo.

Start LiteLLM

export FORTYTWO_API_KEY="<your Fortytwo key>"
export LITELLM_MASTER_KEY="sk-$(openssl rand -hex 24)"
echo $LITELLM_MASTER_KEY
litellm --config litellm.yaml --port 4000

The echo line prints the master key: copy it for the last step. Keep this terminal open while you use Codex.

Configure Codex

Add this to ~/.codex/config.toml. The first three lines go at the top of the file, before any [section]; replace any model or model_provider lines already there.

~ is your home folder. Folders that start with a dot, such as .pi, .config or .codex, are hidden. To show them: Cmd+Shift+. in Finder on macOS, View → Show → Hidden items in File Explorer on Windows, Ctrl+H in most Linux file managers.

~/.codex/config.toml

model = "qwen/qwen3.8-27b"
model_provider = "fortytwo"
model_context_window = 262144

[model_providers.fortytwo]
name = "Fortytwo via LiteLLM"
base_url = "http://localhost:4000/v1"
env_key = "LITELLM_MASTER_KEY"
wire_api = "responses"

Start Codex

In a second terminal, set the same master key and start Codex in your project folder:

export LITELLM_MASTER_KEY="<the master key from step 3>"
codex

Codex warns Model metadata for qwen/qwen3.8-27b not found. The warning does not affect requests.

More options: Codex custom model providers , LiteLLM OpenAI-compatible endpoints .

Something not working with your agent, or using one we have not listed? Tell us in the platform: Feedback for ideas and small bugs, Contact support if it blocks your work, or Report a security issue.

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Connect Codex through LiteLLM