In the 2018 paper “The Design and Implementation of XiaoIce, an Empathetic Social Chatbot” (arXiv 1812.08989), Microsoft researchers state that their Chinese social chatbot “has communicated with over 660 million active users.” XiaoIce, launched in 2014, was designed for companionship rather than task completion, and its average Conversation-turns Per Session (CPS) reached 23 - which the authors note “is significantly higher than that of other chatbots and even human conversations.” It was the largest deployment of a social chatbot in the world at the time, years before companion apps reached the West.