Cartesia

Cartesia is a real-time voice AI company and an API-first platform for speech generation, transcription, and production voice agents. Its two flagship models are Sonic, a text-to-speech engine, and Ink, a streaming speech-to-text engine, both built on State Space Model (SSM) architectures the founding team helped pioneer at Stanford's AI Lab. Sonic is designed around naturalness and speed: it delivers sub-90ms latency, reads emotional subtext from a transcript to calibrate delivery, supports non-verbal cues such as inserted laughter, and natively handles 44 languages for multilingual applications. Ink is positioned as a fast and accurate streaming transcription model with the lowest word error rate among streaming STT systems, sensing structured data like phone numbers, dates, and emails, and providing native turn detection (turn.start, turn.end, and eager end) so agents know when a caller has finished speaking without external voice-activity detection. On top of these models, Cartesia offers Managed Agents, a platform for building and shipping enterprise voice agents with a fully managed runtime, advanced reasoning, tool calling, real-time actions, built-in evaluations, and telephony integration including SIP trunking and Cartesia-provisioned phone numbers. Voice features include instant voice cloning from about ten seconds of audio, professional voice cloning, accent localisation, and custom pronunciation dictionaries for domain terms and proper nouns. Cartesia emphasises deployment flexibility: the same models and agents can run in the cloud through regional API endpoints, on-premise, or on-device, keeping inference in-region to satisfy latency, data-residency, and compliance requirements. The platform is certified or aligned with SOC 2 Type 2, HIPAA, and GDPR, and reports top rankings on the Artificial Analysis Speech Arena and speech-to-text leaderboards, and counts companies such as ServiceNow, Quora, and Retell among its customers. Billing is credit-based, with pay-as-you-go credits for models and per-minute rates for voice agents and telephony. In short, Cartesia sells the speech layer that lets real-time AI products talk and listen.