Cartesia

Cartesia builds real-time voice AI infrastructure, anchored by Sonic, a text-to-speech model tuned for ultra-low latency. It's made for developers and businesses building voice agents that have to respond fast enough to feel like a real conversation, across sectors like finance, healthcare, and government where both speed and compliance matter. Alongside Sonic, the platform offers streaming speech-to-text and a layer for building and deploying interactive agents.

The technical bet is its State Space Model architecture, which keeps latency very low while handling long context, and the output stays natural even with tricky alphanumerics and jargon. Just as important is deployment flexibility: you can run it in the cloud, on-premise, or even on-device, which helps teams keep data residency under control in regulated environments. It also supports cloned brand voices and multilingual narration, so a product can speak in a consistent voice across languages.

Pricing is freemium, letting developers test the API before they commit. If you're building live support agents, conversational phone systems, or any app where a half-second delay breaks the illusion, Cartesia is purpose-built for that kind of real-time work.