Lilian Weng, a co-founder of Thinking Machines and former OpenAI VP of AI Safety Research, announced this week that she would step down from Thinking Machines because of health issues. In an internal Slack message also shared on X, Weng wrote, “I don’t feel I’m able to continue at the pace a startup requires,” and said that “several months” of stress and workload had exceeded what her health could physically sustain.

OpenAI told TechCrunch on Wednesday that Weng would rejoin the company. A company spokesperson said Weng will lead a top-level team focused on accelerating OpenAI’s internal research, including cross-research work on recursive self-improvement (AI improving itself through iteration), a process aimed at letting an AI system iterate on itself to become more powerful.

The move follows Weng’s departure from Thinking Machines, a startup co-founded by former OpenAI CTO Mira Murati. TechCrunch noted the shift may appear contradictory because Weng cited the pace of startup work, but said she likely would face less direct pressure at a company where she is not a co-founder. The outlet also described the departure as notable amid fierce competition for talent among AI labs.

Murati replied to Weng’s X post earlier this week with support for her decision to focus on health. “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,” Murati wrote. It was unclear whether Murati knew Weng would rejoin OpenAI.

Lilian Weng, a co-founder of Thinking Machines and former OpenAI VP of AI Safety Research, announced this week that she would step down from Thinking Machines because of health issues. In an internal Slack message also shared on X, Weng wrote, “I don’t feel I’m able to continue at the pace a startup requires,” and said that “several months” of stress and workload had exceeded what her health could physically sustain.

OpenAI told TechCrunch on Wednesday that Weng would rejoin the company. A company spokesperson said Weng will lead a top-level team focused on accelerating OpenAI’s internal research, including cross-research work on recursive self-improvement (AI improving itself through iteration), a process aimed at letting an AI system iterate on itself to become more powerful.

The move follows Weng’s departure from Thinking Machines, a startup co-founded by former OpenAI CTO Mira Murati. TechCrunch noted the shift may appear contradictory because Weng cited the pace of startup work, but said she likely would face less direct pressure at a company where she is not a co-founder. The outlet also described the departure as notable amid fierce competition for talent among AI labs.

Murati replied to Weng’s X post earlier this week with support for her decision to focus on health. “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,” Murati wrote. It was unclear whether Murati knew Weng would rejoin OpenAI.