Lilian Weng Departs Thinking Machines, Returns to OpenAI Over Health

Lilian Weng Thinking Machines Lab OpenAI recursive self‑improvement Inkling Small

Lilian Weng, a co‑founder of the AI startup Thinking Machines Lab, announced she was leaving the company because the sustained stress and workload exceeded her physical health limits. In an internal Slack message shared on X, she wrote that she could no longer keep pace with a startup’s demands and that the “consistent stress and workload” had pushed her beyond what her health could sustain. Her last day at Thinking Machines was set for July 27, 2026.

Days later OpenAI confirmed she would rejoin the organization to lead a top‑level team focused on recursive self‑improvement, a research area that aims to enable AI systems to iteratively enhance themselves. Mira Murati, co‑founder of Thinking Machines and former OpenAI CTO, publicly expressed support for Weng’s decision and thanked her for her contributions. By May 2026, 13 of the lab’s 42 founding members—including three co‑founders—had already left the startup. The company had recently launched its first open‑weight model, Inkling, and in early August released Inkling‑Small, a 276‑billion‑parameter multimodal model roughly one‑quarter the size of Inkling, offered under an Apache 2.0 license with discounted API pricing.

Entities

Fidji Simo · Lilian Weng · Mira Murati · OpenAI · Thinking Machines Lab

Claims

What the coverage asserts, and how well corroborated each claim is across sources.

[● 6 SOURCES] Lilian Weng co‑founded Thinking Machines Lab. techcrunch.com · thenextweb.com · www.business-punk.com · www.itmedia.co.jp · americanbazaaronline.com · +1 more
[● 2 SOURCES] By May 2026, 13 of Thinking Machines Lab’s 42 founding members, including three of six co‑founders, had left the company. thenextweb.com · www.business-punk.com
[● 4 SOURCES] OpenAI announced Lilian Weng will lead a top‑level team accelerating internal research on recursive self‑improvement. techcrunch.com · americanbazaaronline.com · www.ocafezinho.com · thenextweb.com
[● 2 SOURCES] She rejoined OpenAI within days to lead a team focused on recursive self‑improvement. techcrunch.com · thenextweb.com
[● 2 SOURCES] Other AI executives such as Fidji Simo and Greg Yang have stepped back from full‑time roles for health reasons. www.ithome.com · thenextweb.com
[● 2 SOURCES] Weng previously served as Vice President of AI Safety Research at OpenAI. techcrunch.com · thenextweb.com
[● 6 SOURCES] Lilian Weng left Thinking Machines Lab because stress and workload exceeded what her health could sustain. techcrunch.com · thenextweb.com · www.business-punk.com · www.itmedia.co.jp · americanbazaaronline.com · +1 more
[● 2 SOURCES] Mira Murati expressed support for Weng’s decision to prioritize her health. techcrunch.com · thenextweb.com
[● 2 SOURCES] Co‑founders Barrett Zoph, Luke Metz, and Sam Shoenho‑ltz returned to OpenAI earlier in 2026 after leaving Thinking Machines Lab. www.itmedia.co.jp · thenextweb.com
[● 3 SOURCES] Thinking Machines Lab launched its first open‑weight AI model named Inkling. www.business-punk.com · www.itmedia.co.jp · thenextweb.com
[● 5 SOURCES] Mira Murati publicly supported Lilian Weng’s decision to leave Thinking Machines Lab for health reasons. www.business-punk.com · americanbazaaronline.com · techcrunch.com · www.ocafezinho.com · thenextweb.com
[○ 1 SOURCE] Thinking Machines released Inkling‑Small, a 276‑billion‑parameter multimodal model about one‑quarter the size of Inkling, under an Apache 2.0 license with discounted API pricing. venturebeat.com