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Keep your assistant on Vapi and route only its language model through the SLNG context router. You get smart routing, context optimization, in-region execution, and compliant caching on every turn. Speech to text and text to speech stay on Vapi.

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Prerequisites

  • A running Vapi assistant.
  • An SLNG API key from the project you create below: open it and go to Project Vault > SLNG API key. A key from Call TTS/STT models API cannot call the Context Router.
  • A model for the router, chosen in the project’s Think section below: an SLNG model, or an LLM key you registered under Bring your own key.

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Set up in the dashboard

1

Choose Vapi

Start a new project, choose Improve my agent, and under On a voice platform pick Vapi.
New project chooser with the Vapi voice platform highlighted

Pick Vapi on the voice platform path.

2

Pick your model

Open the Think section and choose your LLM model. Keep Context Router on so the model routes through SLNG. Speech to text and text to speech stay on Vapi.
Think section with the LLM model card highlighted, routed through SLNG

Choose your model in the Think section.

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In your Vapi dashboard

Click Integrate in the top right. The modal fills in your router URL and model, then walks you through the steps below in Vapi.
Vapi Model Settings panel with the Custom llm provider, Model, and Custom LLM URL fields

The Model Settings panel in Vapi.

1

Open Model Settings

Open your Vapi assistant and click the edit icon on the Model card to open Model Settings.
2

Select the custom LLM provider

In the Provider dropdown, select Custom llm.
3

Set the model

In the Model field, enter the model you picked in the Think section, for example slng/auto.
4

Set the custom LLM URL

In the Custom LLM URL field, paste https://au.context-router.slng.ai/v1/chat/completions. Swap au for the region closest to your callers.
5

Add your API key

Go to Integrations at the bottom of the side menu. Under Model Providers, click the Custom LLM card and enter your SLNG API key in the API Key field. Click Save.
6

Add agent and session headers

Under Headers for the custom LLM, add these values:
7

Publish and test

Click Publish and run a test conversation to confirm the LLM is routing through SLNG.

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Next steps

  • Context Router for how routing works with your own keys or SLNG-hosted models.