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In a surprising move, AI safety expert Lilian Weng has stepped down from her role at Thinking Machines to rejoin OpenAI, raising questions about the future of both organizations.
Lilian Weng, co-founder and former VP of AI Safety Research at OpenAI, has left her position at Thinking Machines, citing health reasons. She is now back at OpenAI, where she previously led efforts to ensure AI systems are safe and aligned with human values. This move highlights the ongoing importance of AI safety research and the competitive landscape in the AI industry.
Weng's departure from Thinking Machines comes as a significant shift for the company, which has been making waves with its innovative approaches to AI. Her return to OpenAI, a leader in AI research, underscores the organization's commitment to advancing safe and ethical AI practices. Weng’s expertise in AI safety is invaluable, especially as AI systems become more complex and pervasive.
Weng’s decision to leave Thinking Machines was made public through a company statement that emphasized her health and well-being. "Lilian has been an integral part of our team, and we respect her decision to prioritize her health," the statement read. While specific details about her health issues were not disclosed, it is clear that Weng's well-being was a primary concern.
Weng's return to OpenAI also signals a significant boost for the organization. OpenAI has been at the forefront of AI research, particularly in areas like natural language processing (NLP) and reinforcement learning. Weng’s experience with AI safety will be instrumental in guiding these efforts.
Weng’s work on AI safety is rooted in her belief that AI systems must be transparent, explainable, and aligned with human values. Her research has focused on developing frameworks and tools to ensure that AI behaves as intended, even in complex and unpredictable environments.
OpenAI’s recent advancements in AI, such as the release of Codex, a code-generating AI, highlight the importance of Weng’s expertise. Codex can automate tasks like web browsing and data entry, but it also raises concerns about security and ethical use. Weng’s return is likely to play a crucial role in addressing these challenges.
Weng’s return to OpenAI not only strengthens the organization’s research capabilities but also sends a strong message about the importance of AI safety in the tech industry. As AI continues to evolve, ensuring that these systems are safe and ethical will be critical for their widespread adoption and trust.
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Thinking Machines co-founder Lilian Weng left the company citing health reasons, then joined OpenAI | TechCrunch
↗ https://techcrunch.com/2026/07/29/thinking-machines-co-founder-lilian-weng-left-the-company-citing-health-reasons-then-joined-openai/?utm_source=tldrai
About the author
Kai built ML infrastructure at a Bay Area startup before developing an obsession with transformer architectures and inference optimisation that eventually pulled him out of product work entirely. A stint at a compute research lab sharpened his instinct for what actually matters in a model release versus what is marketing. He writes from the inside — from the perspective of someone who has debugged the systems he is describing at three in the morning. He is allergic to hype and instinctively drawn to the unglamorous plumbing questions that everyone else skips over.
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17 August 2026
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