OpenAI executive Fidji Simo is stepping down from her full-time role after a three-month medical leave and will transition to a part-time adviser, she wrote on X. Simo, who was hired a little over a year ago and has been on leave since April, cited an ongoing neuroimmune condition. She oversaw much of OpenAI’s core business while in the role. OpenAI said Simo will hand her responsibilities to three other top executives. The change follows her extended absence and formalizes a shift in operational leadership at the company.