Lilian Weng, former OpenAI safety VP and co-founder of Thinking Machines, announced her departure due to health reasons, just 12 days after the company released its first open-source model, Inkling. Weng spent nearly seven years at OpenAI building safety systems before leaving in November 2024 to co-found Thinking Machines. Her exit has drawn attention, with many colleagues expressing support.
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Just 12 days after the release of Inkling, co-founder Weng Li left Thinking Machines due to health reasons, marking another major personnel change following the departures of core members like Barret Zoph. This reflects the high-intensity culture of AI startups or a continuation of internal issues?
In her public letter, Weng Li clearly stated that the reason for leaving was 'the intensity was too high, my body couldn't take it.' Over the past 7 months, she got sick more times than at any other point in her life, even taking sick leave during the Inkling sprint while battling guilt. She considered switching to a role with narrower responsibilities to reduce anxiety, but believed that 'if I can't give 100% to what I'm responsible for, then I'm not doing the job well,' ultimately choosing to leave.
This decision contrasts sharply with her track record at OpenAI: after joining in 2017, she worked on robotics projects (teaching a five-fingered robotic hand to solve a Rubik's cube), founded the Applied AI Research team, built the Safety Systems team, and became a research VP for safety, witnessing OpenAI's transformation from a non-profit research institute to the ChatGPT era. Additionally, she used her spare time to write the blog Lil'Log, which has over 52,000 Google Scholar citations, and her formula 'Agent = LLM + Memory + Active Planning + Tool Use' has been widely disseminated.
Weng Li's resignation letter did not mention common reasons like strategic disagreements, equity, or KPIs, focusing entirely on personal health. She stated that she still loves AI and enjoys reading papers and following cutting-edge developments, but hopes to go to a more predictable place with clearer boundaries, and no longer serve as a co-founder.
Weng Li's departure is not the first time Thinking Machines has lost core members. In October 2025, co-founder Andrew Tulloch left for Meta; on January 14, 2026, CEO Mira Murati announced at an all-hands meeting that co-founder and CTO Barret Zoph was removed for 'unethical behavior,' and on the same day, co-founder Luke Metz and founding member Sam Schoenholz announced their resignations on Slack. All three later returned to OpenAI, and Zoph himself denied being fired, insisting he resigned first.
This series of personnel changes directly affected the company's fundraising. After the January 2026 turmoil, funding negotiations originally targeting a $50 billion valuation collapsed, leaving the valuation at $12 billion—the same as after the $2 billion seed round in July 2025.
Weng Li's departure came just 12 days after Inkling's release, and Inkling itself is not the strongest model (the company's model card honestly states 'This is not the strongest model today, open-source or closed-source'), further fueling external concerns about the company's prospects. Some netizens pointed out that Weng Li is the 'fourth co-founder to leave,' hinting at possible internal issues.
Weng Li's case reflects the widespread high-intensity work culture in AI startups. During her seven years at OpenAI, she did research during the day and wrote blogs at night, adhering to the motto of 'persistence and humility,' but ultimately in her 20 months at Thinking Machines, she 'lived a lifetime.' This culture is particularly prominent in the AI field, which pursues rapid iteration and breakthroughs, but the cost borne by individuals is often overlooked.
Notably, Weng Li's departure received widespread understanding. Mira Murati expressed on X that she was 'glad you put your health first,' and current CTO Soumith Chintala also expressed nostalgia. Dozens of comments shared a common theme: get well first. This reflects a consensus within the industry about health issues, but in practice, high-intensity work remains the norm.
This article is based on a report by Qubit on Weng Li's departure, which cited Weng Li's public letter, X platform comments, and Thinking Machines' public timeline. All facts come from this single source without external verification. Weng Li's reasons for leaving, the company's personnel timeline, and funding situation are clearly stated in the report, but some details (such as Zoph's denial of being fired) are one-sided statements from the parties involved and should be treated with caution.
Weng Li's departure from Thinking Machines due to health reasons is a manifestation of the individual cost of high-intensity culture in AI startups. Combined with the company's previous core personnel departures and fundraising setbacks, this event may further shake external confidence in Thinking Machines' team stability and development prospects.
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