Fidji Simo, OpenAI's CEO of applications. Bloomberg/Getty Images Fidji Simo is stepping down from her executive role at OpenAI after her medical leave. The former Instacart CEO will transition to a part-time advisor role. Simo's chronic illness pushed her to take medical leave three months ago. Fidji Simo, one of OpenAI's top executives, is stepping down. Simo, the company's CEO of applications, wrote on X on Thursday that she has decided to leave her full-time role and transition to becoming