Lilian Weng returns to OpenAI to lead RSI

Why did Lilian Weng return to OpenAI so quickly?

Lilian Weng has returned to OpenAI to lead a self-improving model research team.

1. Lilian Weng

Lilian Weng is back at OpenAI after leaving Thinking Machines Lab for health reasons. According to the report, she will lead an RSI, or self-improving, team inside OpenAI, a group tied to one of the company’s top research priorities.

That return is notable because Weng had already built a long track record at OpenAI before leaving. She spent about six years there, working across reinforcement learning, robotics, applied AI, model safety, and post-training defenses for ChatGPT.

• Former OpenAI role: VP of Research and Safety
• Known for: Lil’Log, a technical blog read widely in AI
• OpenAI contribution: coauthor on the GPT-4 Technical Report

2. RSI research

The new team focuses on RSI, short for self-improving systems. In plain terms, the goal is to build models that can help train and improve future models, which puts the work close to the center of OpenAI’s long-term research agenda.

Weng had written a deep blog post on RSI earlier in the month, so the move fits her public research interests. It also suggests OpenAI wants someone with both theory depth and hands-on safety experience to guide the effort.

3. OpenAI’s pull

Weng is not the only former Thinking Machines Lab leader to end up at OpenAI. Barret Zoph and Luke Metz had already moved there, while Andrew Tulloch went to Meta. The report says three of the four people who left TML chose OpenAI as their next stop.

That pattern makes OpenAI look less like a rival employer and more like a magnet for researchers who want scale, compute, and a direct line to frontier model work. It also shows how quickly the startup’s early talent base has been reshuffled.

• Barret Zoph: moved from TML to OpenAI
• Luke Metz: moved from TML to OpenAI
• Andrew Tulloch: moved from TML to Meta

4. Thinking Machines Lab

Thinking Machines Lab was founded by former OpenAI CTO Mira Murati after OpenAI’s leadership turmoil in 2024. The company raised a huge seed round in 2025, with a reported $2 billion at a $12 billion valuation, and quickly became one of the most watched AI startups.

But the article frames the company’s main asset as people, not products. With Weng gone, the lab has lost another founder-level figure, and only two of its six cofounders remain. The piece also notes that at least 14 of the 42-person founding team have already left.

• Seed round: $2 billion
• Post-money valuation: $12 billion
• Cofounders remaining: 2 of 6

5. Weng’s career arc

Weng’s path helps explain why this move matters. She studied at Peking University, later earned a doctorate, and built an early reputation as a strong RL researcher and unusually prolific technical writer. Her blog posts on Transformer models, reinforcement learning, and agents became reference material for many readers.

Her career has now looped from OpenAI to a startup cofounder role and back to OpenAI again. The shift also reflects a practical point in the story: she said the startup pace had become hard to sustain while dealing with health issues.

How to decide

If you care about research direction, the RSI team is the key detail. If you care about talent flow, the bigger story is OpenAI drawing back people it once helped train. And if you care about startup dynamics, Thinking Machines Lab is a reminder that even well-funded labs can lose their early edge when senior researchers start moving again.

For readers tracking AI org charts, this is less about one hire than about where top researchers think the most important work now sits. In this case, the answer appears to be back at OpenAI.