Stateful AgentsVoice Agents

Connecting with Vapi

Connecting to Letta Cloud

1

Add your LETTA_API_KEY

Add Letta Cloud as an integration by entering your LETTA_API_KEY into the “Custom LLM” field at https://dashboard.vapi.ai/settings/integrations.

2

Create an assistant

Create a Vapi assistant at https://dashboard.vapi.ai/assistants/ and use the “Blank Template”.

3

Connect your Letta agent

Select “Custom LLM” for the model, and enter in the voice endpoint for your agent: https://api.letta.com/v1/voice-beta/{AGENT-ID}

The “Model” field will be ignored (since your agent_id is already configured with a model in Letta), so can be any value.
4

Talk to your agent

You can now interact with your agent through Vapi, including calling and texting your agent!

Connecting to a self-hosted Letta server

To connect to a self-hosted server, you will need to have a internal accessible endpoint for your Letta server and add any authentication tokens (if they exist) instead of LETTA_API_KEY. We recommend using ngrok to expose your Letta server to the internet.

1

Setting up ngrok

If you are self-hosting the Letta server locally (at localhost), you will need to use ngrok to expose your Letta server to the internet:

  1. Create an account on ngrok
  2. Create an auth token and add it into your CLI
ngrok config add-authtoken <YOUR_AUTH_TOKEN>
  1. Point your ngrok server to your Letta server:
ngrok http http://localhost:8283

Now, you should have a forwarding URL like https://{YOUR_FORWARDING_URL}.ngrok.app.

2

Create an assistant

Create a Vapi assistant at https://dashboard.vapi.ai/assistants/ and use the “Blank Template”.

3

Connect your Letta agent

Select “Custom LLM” for the model, and enter in the voice endpoint for your agent: https://{YOUR_FORWARDING_URL}.ngrok.app/v1/voice-beta/{AGENT_ID}

The “Model” field will be ignored (since your agent_id is already configured with a model in Letta), so can be any value.
4

Talk to your agent

You can now interact with your agent through Vapi, including calling and texting your agent!