Lilian Weng steps down from Thinking Machines Lab citing startup stress

Jul 28, 2026

Lilian Weng, cofounder of AI startup Thinking Machines Lab, is stepping down, citing the physical toll of startup stress and workload. Her departure highlights a trend of health-related exits in the AI industry, following similar moves by leaders at OpenAI and xAI. The move also comes as Thinking Machines faces significant talent attrition, having lost 13 of its 42 founding members amid a competitive "AI talent war."

Weng departure from Thinking Machines

▪Prior to cofounding Thinking Machines Lab, Lilian Weng was OpenAI's vice president of research and safety.
▪Lilian Weng, a cofounder of AI startup Thinking Machines Lab, announced she is stepping down, with her last day being July 28, 2026.
▪Weng reported being sick more often in the seven months prior to her departure than at any other time in her life, though she did not disclose a specific diagnosis.
▪Mira Murati, a cofounder of Thinking Machines Lab, responded to Weng's departure on X, stating "I'm glad that you're putting your health first."
▪Weng stated she was unable to continue at the "pace a startup requires" due to the physical toll of consistent stress and workload.

Health-related exits in AI industry

▪In January 2026, xAI cofounder Greg Yang moved to an informal advisory role after a Lyme disease diagnosis and months of unexplained fatigue.
▪Emad Mostaque, founder of Stability AI, stated he "got real sick" while leading the company before his departure in 2024.
▪In July 2026, Fidji Simo stepped down from her full-time role as OpenAI's CEO of AGI after a flare-up of postural orthostatic tachycardia syndrome (POTS).

Thinking Machines talent attrition

▪The attrition at Thinking Machines Lab is occurring as rivals like Meta and OpenAI offer large compensation packages in a competitive "AI talent war."
▪The departures from Thinking Machines Lab include three of its six original cofounders.
▪A Business Insider review in May 2026 found that 13 of Thinking Machines Lab's 42 founding members had left since the company's launch.