Mira Murati’s Thinking Machines Lab is losing two of its co-founders to OpenAI

Thinking Machines Lab, the startup of former OpenAI exec Mira Murati, is bidding farewell to two of its co-founders, both of whom are returning to OpenAI. Another former OpenAI employee who went to work at Murati’s startup has also returned to the company.

Moratti announced on social media on Wednesday the departure of Barrett Zoff, the company’s co-founder and CTO. “We have parted ways with Barrett,” Moratti said in a post on

Moratti’s announcement made no mention of co-founder Luc Metz or other departures.

Just 58 minutes after Moratti announced Zoph’s departure, Fidji Simo, CEO of Applications at OpenAI, announced that Zoph would be returning to OpenAI. “I’m excited to welcome Barrett Zoff, Luke Metz, and Sam Schoenholz back to OpenAI! This has been in the works for several weeks, and we’re thrilled to have them join the team,” Simo wrote on X’s website.

Metz, a co-founder of Thinking Machines, previously worked at OpenAI for a number of years on the company’s technical staff. So did Schoenholz, whose LinkedIn profile still lists him as working for Thinking Machines.

Zoff previously worked at OpenAI as vice president of research, and before that he worked for six years at Google as a research scientist. Moratti, who served as CTO at OpenAI until September 2024, left the company and co-founded Thinking Machines with Zoph and Metz. The startup, where Moratti serves as CEO, has raised significant financial backing since then, closing a $2 billion seed round last July, with participation from Andreessen Horowitz, who led the round, as well as Accel, Nvidia, AMD and Jane Street, among others. The round valued the company at $12 billion.

TechCrunch has reached out to both Thinking Machines and OpenAI for comment.

While the transfer of talent between AI giants is common in Silicon Valley, the departure of co-founders from startups less than a year after founding is particularly notable. Losing two co-founders at once — especially when one of them was CTO — could be seen as a particularly meaningful setback for Thinking Machines, which has assembled a high-profile team of former OpenAI, Meta, and Mistral researchers.

The company also lost other key employees, including co-founder Andrew Tulloch, who left to join Meta in October. OpenAI itself has seen several co-founders leave to launch or join competing projects, including John Shulman, who left for Anthropic in August 2024 before joining Thinking Machines Lab as chief scientist at its launch in February last year.