Lilian Weng Leaves Thinking Machines Lab, Rejoins OpenAI
Weng's return to OpenAI marks a notable reversal of the AI safety talent exodus that followed her 2024 departure, bringing a key safety voice back to the company.
Reporting from 1 source: GIGAZINE.
Lilian Weng, co-founder of Thinking Machines Lab and former OpenAI safety lead, has left the startup citing health issues and stress. OpenAI confirmed she will rejoin the company. Weng announced her departure on X on July 27, 2026, saying she could no longer keep up with the startup pace.
Lilian Weng, co-founder of Thinking Machines Lab, announced her resignation on July 27, 2026, citing health problems and the intense workload of startup life. In a post on X, she said the past seven months were the worst for her health and that the stress exceeded her limits. She also congratulated the company on the release of its product Inkling, which she called a landmark milestone.
OpenAI has confirmed that Weng will rejoin the company. Weng previously led OpenAI's safety team and became Vice President of Research and Safety in August 2024 before departing in November 2024. She then co-founded Thinking Machines Lab with former OpenAI CTO Mira Murati.
Synthesized by Yomimono from the 1 cited source below, including Japanese-language reporting where cited, then editorially reviewed before publishing.