Vapi is the developer platform for building real-time voice AI assistants with a unified STT → LLM → TTS pipeline. Smallest AI's Lightning is available as a built-in voice provider in Vapi's assistant configuration, so you can give your assistant production-grade speech without installing a package or maintaining an extra integration. Select Lightning in your assistant's voice settings, add your Smallest AI API key, and pick from multiple voices or clone your own. Speech starts streaming in about a tenth of a second, and the same models scale from prototype to call-center traffic.