Deepgram combines streaming STT, LLM orchestration, turn detection, barge-in, and streaming TTS over one WebSocket while preserving paths for standalone speech models and bring-your-own LLM or TTS.
ElevenLabs has expanded from a TTS vendor into the ElevenAgents platform: Scribe Realtime listens, Flash speaks, and the platform connects the LLM, turn-taking, tools, and telephony. The key choice is whether you need a voice model or the whole agent control plane.
LiveKit models a voice agent as a server participant in a realtime media room, with AgentSession orchestrating STT, turn detection, LLM, TTS, and interruption. It raised a $100 million Series C at a $1 billion valuation in 2026. It fits products needing WebRTC, multiple client platforms, telephony, and swappable models, but self-hosting the media server does not self-host the entire AI pipeline.
Vapi connects phone and web audio, STT, LLMs, TTS, tool calls, and call observability in a managed voice runtime. Providers are swappable, but Vapi's realtime orchestration is not portable. In May 2026, the company reported one million developers and announced a $50 million Series B.