Sierra

Sierra is the fastest-rising company in conversational AI and the standard-bearer for the new, LLM-native generation of customer agents. Founded in 2023 by Bret Taylor — former co-CEO of Salesforce and chair of OpenAI's board — and Clay Bavor, a former Google executive, and headquartered in San Francisco, Sierra builds AI agents that handle end-to-end customer interactions: answering questions, processing returns, refinancing mortgages, and managing subscriptions in natural conversation.

Rather than depend on a single model, Sierra runs a "constellation of models" with its own fine-tuned proprietary layers, and its agents now handle billions of interactions for more than 40 percent of the Fortune 50. The company reported over $150 million in annual recurring revenue and in May 2026 raised $950 million at a $15.8 billion valuation, led by Tiger Global and Google's GV with Benchmark, Sequoia, and Greenoaks — up from $10 billion only months earlier.

Choose Sierra when you want an outcome-based, LLM-native customer agent backed by the most credible founding team in the category.