OPENAI CHAIRMAN’S AI STARTUP SIERRA RAISES $950 MILLION — VALUATION HITS $15.8 BILLION Sierra, the enterprise AI startup cofounded by OpenAI Chairman Bret Taylor, closed a monster $950 million Series E led by Tiger Global and Google’s GV — pushing its valuation from $10 billion to $15.8 billion in under a year. The company went from zero to $100 million in annual revenue in under two years by building AI agents that replace entire customer service departments. When the chairman of OpenAI needs his own AI startup on the side, you know the gold rush is at full gallop. Keywords: Sierra AI funding, Bret Taylor startup, enterprise AI investment, Series E 2026