Sierra Raises $950M at $15.8B Valuation as Enterprise AI Agent Race Accelerates

Sierra, the AI customer experience startup co-founded by former Salesforce co-CEO and OpenAI chair Bret Taylor, raised $950 million in a Series E led by Tiger Global and Google Ventures at a $15.8 billion post-money valuation — nearly doubling from $10 billion eight months prior. The company hit $150 million in ARR and serves over 40% of the Fortune 50. In March, Sierra launched Ghostwriter, a self-service 'agent-building agent' that lets businesses create AI customer service agents from natural language prompts without engineering teams. Named customers include Prudential, Cigna, Rocket Mortgage, Nordstrom, and one in three of the world's largest banks.