Xi Yin, Harvard's youngest Chinese full professor and a specialist in string theory and quantum gravity, confirmed his departure from OpenAI in a post on X, stating it was his final day at the company. Yin left academia to join OpenAI in late May 2026 but did not disclose his next destination. Yin thanked colleagues Alex Lupsasca, Boris Alexeev, and Dan Roberts in his farewell post. He joined Harvard's physics department as a full professor at age 31 in 2015 and received the 2017 Breakthrough Prize "New Horizons in Physics" award. His move from OpenAI marks another high-profile exit from the AI lab amid ongoing talent reshuffling across the industry.