Lilian Weng rejoins OpenAI after leaving Thinking Machines Lab over the startup's grueling pace

Lilian Weng, a Thinking Machines Lab cofounder, is returning to OpenAI. Business Wire/AP; Tyler Le/BI Thinking Machines Lab cofounder Lilian Weng returns to OpenAI, leading an AI research team. Weng said she left Thinking Machines Lab for health reasons, writing that the gig was grueling. At OpenAI, she'll support the high-stakes push to build AI models that can improve their successors. Lilian Weng, a cofounder of the AI startup Thinking Machines Lab who stepped down this week, is rejoining…