Lilian Weng, a co‑founder of the artificial‑intelligence startup Thinking Machines, sent an internal Slack message that she could no longer sustain the workload demanded by a fast‑growing company. In the note, which she also posted on X, Weng said the “consistent stress and workload” had pushed her health beyond its limits and that she needed to step down.

Weng’s exit, announced on July 27, 2026, prompted an outpouring of support from her former colleague Mira Murati, who had previously served as OpenAI’s chief technology officer. Murati replied on X, “We’ll miss you… I’m glad that you’re putting your health first,” and added a heartfelt thank‑you to the team at Thinking Machines.

Just two days after Weng’s announcement, OpenAI told TechCrunch that the AI research leader would be rejoining the company. The former VP of AI Safety Research will now lead a top‑level team tasked with accelerating OpenAI’s internal research agenda. According to a company spokesperson, the group will focus on cross‑research initiatives, notably recursive self‑improvement—a process that enables an AI system to iteratively enhance its own capabilities.

Weng’s transition from a co‑founder role to a senior research position at OpenAI appears to address the health concerns she raised. While she will still carry significant responsibility, the move removes the founder‑level pressure of steering a nascent startup. Industry observers note that the shift also reflects the intense competition for top AI talent, as leading labs vie to attract experts who can drive breakthrough research.

The announcement arrives at a time when AI labs are racing to secure breakthroughs in safety and capability. By assigning Weng to oversee a team that bridges multiple research areas, OpenAI signals its commitment to both rapid progress and responsible development. The company has not disclosed the size of the new team or the timeline for its initiatives.

Thinking Machines, which Weng helped launch, has not issued a formal comment beyond Murati’s supportive message. The startup’s future direction remains uncertain, but the departure of a co‑founder underscores the personal toll that high‑velocity tech environments can exact.

This article was written with the assistance of AI.
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