Lilian Weng Leaves Thinking Machines, Rejoins OpenAI for AI Research

Lilian Weng Steps Down from Thinking Machines Due to Health Concerns

Lilian Weng, co-founder of the AI startup Thinking Machines, announced her departure this week, citing the toll of startup life on her health. In an internal Slack message she later shared on X, Weng stated: “I don’t feel I’m able to continue at the pace a startup requires. 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.”

Departure Announcement and Internal Memo

Weng’s exit marks a significant leadership change at Thinking Machines, a company known for its focus on advanced AI systems. Her message emphasized that the decision was difficult but necessary for her well-being.

Key Details from Her Slack Message

• She cited “consistent stress and workload” that exceeded her physical limits.
• The departure was not sudden—she had been contemplating it for months.
• She publicly thanked her colleagues and expressed hope for the future.

Return to OpenAI for AI Research Leadership

Just days after leaving Thinking Machines, OpenAI confirmed to TechCrunch that Weng would rejoin the company. She previously served as OpenAI’s VP of AI Safety Research. This time, she will lead a top-level team focused on accelerating internal research.

New Role Focused on Recursive Self-Improvement

According to an OpenAI spokesperson, Weng’s team will support cross-research work on recursive self-improvement—a process where an AI system iterates on itself to become more powerful. This is a critical area for advancing AGI capabilities while maintaining safety.

Implications for AI Safety

• The role aligns with Weng’s expertise in AI safety and alignment.
• It suggests OpenAI is doubling down on self-improving systems, a controversial yet promising frontier.
• Her move may seem contradictory to her health-driven departure, but working at OpenAI as a non-founder likely reduces pressure.

Industry Reactions and Competitive Landscape

Weng’s high-profile transition has sparked conversations about talent retention in the AI sector. Mira Murati, co-founder of Thinking Machines and former OpenAI CTO, publicly supported Weng’s health-first decision—without revealing she had already joined OpenAI.

Support from Co-Founder Mira Murati

Murati replied to Weng’s X post: “We’ll miss you, it’s been wonderful building Thinky together. I’m glad that you’re putting your health first. Thank you for everything.”

Talent Competition in AI Labs

This episode underscores the fierce competition for top AI researchers. Companies like Microsoft, Anthropic, and OpenAI are vying for experts who can drive breakthroughs in areas like recursive self-improvement. Weng’s return to OpenAI could strengthen its lead in autonomous AI development.

As the story develops, the AI community watches closely to see how Weng’s health recovers and what innovations her team will produce.