Thinking Machines co-founder Lilian Weng left the company citing health reasons, then joined OpenAI

Lilian Weng, a co-founder of Thinking Machines, said she stepped down because startup stress and workload had become unsustainable for her health. OpenAI confirmed she is rejoining the company to lead a top-level team focused on accelerating internal research, including work on recursive self-improvement.

The move highlights how intense competition for senior AI researchers can quickly reshape teams across leading labs. It also underscores a growing tension in the AI sector: the pace of frontier research is accelerating, while burnout and founder-level pressure remain serious risks.