Thinking Machines co-founder Lilian Weng left the company citing health reasons, then joined OpenAI
In Brief
2:07 PM PDT · July 29, 2026
Lilian Weng, co-founder of Thinking Machines, announced this week that she would step down from her role, citing health issues.
“I don’t feel I’m able to continue at the pace a startup requires,” she wrote in an internal Slack message, which she also shared on X. “After thinking about it for several months, I ultimately have to admit that the amount of consistent stress and workload have pushed me beyond what my health can sustain physically.”
On Wednesday, OpenAI told TechCrunch that Weng would be rejoining the company, where she previously served as the VP of AI Safety Research.
According to a company spokesperson, Weng will lead a top-level team focused on accelerating OpenAI’s internal research. This team will support cross-research work on recursive self-improvement, a process that would allow an AI system to iterate on itself to become more...
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