---
title: "Thinking Machines co-founder Lilian Weng returns to OpenAI"
url: https://www.parallelquant.com/posts/thinking-machines-co-founder-lilian-weng-returns-to-openai-d5f326
source_name: "TechCrunch"
source_url: https://techcrunch.com/2026/07/29/thinking-machines-co-founder-lilian-weng-left-the-company-citing-health-reasons-then-joined-openai/
published: 2026-07-29T21:07:48.000Z
topics: ["llms", "research"]
publisher: "Parallel Quant"
---

# Thinking Machines co-founder Lilian Weng returns to OpenAI

*2026-07-29 · Source: [TechCrunch](https://techcrunch.com/2026/07/29/thinking-machines-co-founder-lilian-weng-left-the-company-citing-health-reasons-then-joined-openai/)*

Lilian Weng, a co-founder of Thinking Machines Lab, has left the company citing health reasons and subsequently joined OpenAI. Weng previously served as OpenAI's VP of AI Safety Research before co-founding Thinking Machines.

**Why it matters:** Weng's return is a notable reversal for a high-profile safety researcher who left OpenAI to help build a competitor alongside Mira Murati, and a reminder of how thin and fluid the senior safety-research talent pool remains across labs. Her departure also raises questions about Thinking Machines' leadership bench as it competes for talent against better-funded rivals.

**Topics:** llms, research

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Read the original: https://techcrunch.com/2026/07/29/thinking-machines-co-founder-lilian-weng-left-the-company-citing-health-reasons-then-joined-openai/
Canonical: https://www.parallelquant.com/posts/thinking-machines-co-founder-lilian-weng-returns-to-openai-d5f326
Published by Parallel Quant — https://www.parallelquant.com