AI Matters
Why it matters
Thinking Machines co-founder leaves, returns to OpenAI
TechCrunch Thinking Machines co-founder Lilian Weng left the company citing health reasons, then joined OpenAI
Lilian Weng, a co-founder of Thinking Machines and former OpenAI VP of AI Safety Research, left the startup for health reasons and rejoined OpenAI.
Why it matters
A notable departure highlights ongoing turnover among senior AI safety researchers moving between top labs.
Latest brief · Jul 30, 2026