Bret Taylor's Sierra, which sells AI customer service agents, raised a $950M Series E led by Tiger and GV at a $15.8B post-money valuation, up from $10B in 2025 (Kate Rooney/CNBC)

Kate Rooney / CNBC: Bret Taylor's Sierra, which sells AI customer service agents, raised a $950M Series E led by Tiger and GV at a $15.8B post-money valuation, up from $10B in 2025 - Artificial intelligence startup Sierra is raising nearly a billion dollars in a new funding round, CNBC has learned …