Retell's voice agents reach 100M monthly calls using OpenAI models

Retell says it now handles 100 million calls each month using OpenAI models. In its own testing, GPT-6 Astra topped Retell's voice agent benchmark. The company also credits OpenAI's Codex coding tool for helping it reach a $1.6M annual revenue run rate per employee.
What makes a voice agent feel natural to you on a phone call?

