OpenAI’s second-highest-ranking executive, Fidji Simo, announced she is leaving her full-time position as the company’s CEO of artificial general intelligence deployment after a three-month medical leave for a chronic neuroimmune condition, transitioning instead to a part-time role. In a Thursday social-media post, Simo explained that her recovery would take longer than expected and that she needed to prioritize her health. Her departure follows other recent leadership changes at the ChatGPT maker as it nears a public launch. CEO Sam Altman responded online, expressing sadness and thanking Simo for her contributions and friendship. The move matters because Simo was a key figure in OpenAI’s rapid expansion and product strategy.