Sierra

Sierra builds AI agents that help businesses handle customer service, sales and retention across voice, chat, email and other digital channels. Its agents execute tasks such as processing insurance claims, returning orders and managing subscriptions. Ghostwriter creates agents from business documents, recordings or plain-language instructions, while Insights provides conversation analysis, testing and visibility into agent actions. Horizon supports longer customer relationships through persistent context, proactive engagement and plans spanning days or months. Sierra offers outcome-based pricing.

Founded in 2023 by CEO Bret Taylor and Clay Bavor, Sierra combines enterprise software and consumer product experience: Taylor previously served as Salesforce co-CEO, while Bavor led Google Labs. Its τ-Bench research, begun in 2024, evaluates whether agents complete tasks end to end. Extensions test knowledge retrieval and tool use by checking changes to simulated backend databases, alongside voice interactions with interruptions, noise and connection problems. Sierra also acquired Takeoff in July 2026.

In May 2026, Sierra reported serving over 40% of the Fortune 50, with its agents powering billions of customer interactions. Sacra estimates annual recurring revenue reached $200 million that month. Sierra’s May financing announcement outlined a $950 million raise led by Tiger Global and GV at a valuation exceeding $15 billion.