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Using LiteLLM with OpenAI Codex

This guide walks you through connecting OpenAI Codex to LiteLLM. Using LiteLLM with Codex allows teams to:

  • Access 100+ LLMs through the Codex interface
  • Use powerful models like Gemini through a familiar interface
  • Track spend and usage with LiteLLM's built-in analytics
  • Control model access with virtual keys

Quickstart​

info

Requires LiteLLM v1.66.3.dev5 and higher

Make sure to set up LiteLLM with the LiteLLM Getting Started Guide.

1. Install OpenAI Codex​

Install the OpenAI Codex CLI tool globally using npm:

npm i -g @openai/codex

2. Start LiteLLM Proxy​

docker run \
    -v $(pwd)/litellm_config.yaml:/app/config.yaml \
    -p 4000:4000 \
    ghcr.io/berriai/litellm:main-latest \
    --config /app/config.yaml

LiteLLM should now be running on http://localhost:4000

3. Configure LiteLLM for Model Routing​

Ensure your LiteLLM Proxy is properly configured to route to your desired models. Create a litellm_config.yaml file with the following content:

model_list:
  - model_name: o3-mini
    litellm_params:
      model: openai/o3-mini
      api_key: os.environ/OPENAI_API_KEY
  - model_name: claude-3-7-sonnet-latest
    litellm_params:
      model: anthropic/claude-3-7-sonnet-latest
      api_key: os.environ/ANTHROPIC_API_KEY
  - model_name: gemini-2.0-flash
    litellm_params:
      model: gemini/gemini-2.0-flash
      api_key: os.environ/GEMINI_API_KEY

litellm_settings:
  drop_params: true

This configuration enables routing to specific OpenAI, Anthropic, and Gemini models with explicit names.

4. Configure Codex to Use LiteLLM Proxy​

Set the required environment variables to point Codex to your LiteLLM Proxy:

# Point to your LiteLLM Proxy server
export OPENAI_BASE_URL=http://0.0.0.0:4000 

# Use your LiteLLM API key (if you've set up authentication)
export OPENAI_API_KEY="sk-1234"

5. Run Codex with Gemini​

With everything configured, you can now run Codex with Gemini:

codex --model gemini-2.0-flash --full-auto

The --full-auto flag allows Codex to automatically generate code without additional prompting.

6. Advanced Options​

Using Different Models​

You can use any model configured in your LiteLLM proxy:

# Use Claude models
codex --model claude-3-7-sonnet-latest

# Use Google AI Studio Gemini models
codex --model gemini/gemini-2.0-flash

Troubleshooting​

  • If you encounter connection issues, ensure your LiteLLM Proxy is running and accessible at the specified URL
  • Verify your LiteLLM API key is valid if you're using authentication
  • Check that your model routing configuration is correct
  • For model-specific errors, ensure the model is properly configured in your LiteLLM setup

Additional Resources​