Resigned for Health Reasons, Joined OpenAI Three Days Later: Talent Flow Truths Aren't in PR Releases

Let's look at some data first. Before Lilian Weng left, Thinking Machines had a valuation of $4.2 billion, raised over $1.2 billion in cumulative funding, and had about 800 employees. Meanwhile, OpenAI is valued at $300 billion, has around 5,000 employees, and an annual compute budget exceeding $7 billion. Lilian Weng herself is one of the most prominent technical leaders in AI safety; she previously led the safety team at OpenAI, co-founded Thinking Machines in 2023, and served as Chief Scientist.