Cartesia Text-to-Speech Accelerates Retell AI's Enterprise Voice Agent Platform

Retell AI operates a no-code platform enabling businesses to deploy voice agents for 24/7 call center automation, handling appointment booking, lead qualification, and customer inquiries. The company manages over 40 million calls monthly for 3,000+ customers across healthcare, financial services, logistics, and retail. Retell's founding team from Google, Meta, and ByteDance recognized a critical gap in production voice AI: traditional text-to-speech providers suffered from reliability issues during peak hours, inconsistent accuracy on alphanumeric sequences (phone numbers, addresses, confirmation codes), and latency that made conversations feel unnatural. Enterprise customers required a voice solution that could guarantee accuracy on edge cases while maintaining 24/7 uptime.

Retell deployed Cartesia's text-to-speech as its primary voice provider with automatic failover capabilities. Cartesia's architecture, built on state space models rather than traditional transformers, delivered three critical improvements. First, Time-to-First-Audio latency was 2-3x faster than competing providers on Retell's platform, enabling natural-sounding conversations essential for high-stakes calls. Second, the model achieved a <0.1% error rate on production calls through specialized fine-tuning for the alphanumeric sequences that cause other systems to fail—phone numbers, addresses, and confirmation codes are pronounced correctly consistently. Third, Cartesia provided 99.9% uptime with enterprise-grade reliability, eliminating the random outages that plagued legacy providers. The integration required a single API call, allowing Retell customers to enable Cartesia voices in minutes without re-engineering existing systems. Native support for 40+ languages eliminated the need for manually adapted language models.

Retell achieved the fastest adoption rate for any new voice provider in company history, driven by measurable improvements across latency, accuracy, and reliability metrics. Cartesia is now embedded as a core component of Retell's platform, with solutions engineers relying on it for enterprise accounts where reliability is paramount. The partnership enabled Retell to expand across industries and customer segments, including enterprises like Asbury Auto, Anker, and Storagevault. Retell users now access Cartesia's Sonic 3 model, which supports 27 additional languages, custom pronunciations, speed and volume controls, and improved accuracy—strengthening Retell's competitive position in the production-grade voice AI market.