Techcrunch： Lilian Weng is leaving Thinking Machines Lab for OpenAI， moving from co-founder role into a narrower research post.
Weng said startup stress and workload had pushed her health beyond what she could sustain， after months of considering the decision.
She also said a scoped role in a more predictable place， without co-founder responsibility， would suit her better.
OpenAI says she will lead a top-level group focused on accelerating internal research into recursive self-improvement.
Weng returns with direct institutional knowledge from 2018 to 2024， including GPT-4 development and leadership of Safety Systems.
Her appointment puts a former safety leader near work that OpenAI's Preparedness group is already hiring researchers to manage.
For Thinking Machines Lab， the departure deepens a retention problem， with only 2 of the original 6 co-founders remaining.
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techcrunch .com/2026/07/29/thinking-machines-co-founder-lilian-weng-left-the-company-citing-health-reasons-then-joined-openai/