Thinking Machines Lab Cofounder Lilian Weng Steps Down Citing Startup Stress and Illness

Lilian Weng, cofounder of AI startup Thinking Machines Lab, announced she is stepping down due to repeated illness and unsustainable stress from building the company. In a post on X, Weng said she had been ill more often in the past seven months than ever before and could not maintain the pace required by a startup. She tried to rest during the launch of the company's first open-weight model, Inkling, but felt guilt. Weng plans to seek a more predictable, scoped role outside a cofounder position while remaining in AI. Her departure follows other health-related step-backs by AI leaders, including Fidji Simo of OpenAI and xAI cofounder Greg Yang. Thinking Machines Lab has also lost a significant share of its founding team amid a Silicon Valley AI talent war, with 13 of 42 founding members leaving since launch.