Sierra raises $950M at $15.8B valuation for AI customer service agents

Sierra, the AI customer service agent startup co-founded by Bret Taylor (OpenAI board chairman) and Clay Bavor, raised $950 million at a $15.8 billion post-money valuation in a Series E round led by Tiger Global and GV, with participation from Benchmark, Sequoia, Greenoaks, and others. The valuation triples Sierra's worth from its September 2025 round at $4.5 billion. The company generates $150 million in annual recurring revenue, and its AI agents manage billions of customer interactions across insurance, mortgage refinancing, and product returns.