Sierra, an artificial intelligence startup, has raised nearly $1 billion in a new funding round, bringing in $950 million in fresh capital at a $15.8 post-money valuation, led by Tiger and Google's GV. The company, founded three years ago by Bret Taylor and Clay Bavor, sells AI customer service agents and is positioning itself as a leader in a class of software companies built on top of foundational models from OpenAI and Anthropic. Sierra topped $150 million in annual recurring revenue in eight quarters, a growth timeline that is unprecedented in traditional software and highlights "intense demand in the market." The funding round is part of a trend of large deals in the venture landscape as investors identify category leaders in the AI space. Sierra's customers are mostly enterprises like Prudential, Cigna, Blue Cross Blue Shield and Rocket Mortgage, as well as one in three of the world's largest banks. However, Taylor predicts a market correction within the next two years due to over-analysing the market.