Sebastien Bubeck, Microsoft's vice president for generative AI research, has left the company to join OpenAI, a Microsoft-backed AI startup. Bubeck, who played a key role in developing Microsoft's Phi small language models, is expected to contribute to OpenAI's efforts towards achieving artificial general intelligence (AGI), despite the unclear specifics of his new role. This transition is significant as Microsoft is both a major investor in and competitor to OpenAI. The move follows a trend of notable departures from OpenAI, including former CTO Mira Murati. Microsoft has expressed gratitude for Bubeck's contributions and plans to maintain a professional relationship through his work at OpenAI. CEO Sam Altman has denied any connection between these departures and upcoming company restructuring.