Mira Murati's startup, Thinking Machines Lab, is seeing two of its co-founders depart, with both returning to OpenAI. An additional former OpenAI employee who joined Murati's venture is also making the same move.

On Wednesday, Murati announced via social media the exit of Barret Zoph, the company's co-founder and Chief Technology Officer. "We have parted ways with Barret," Murati stated in a post on X. "Soumith Chintala will be the new CTO of Thinking Machines. He is a brilliant and seasoned leader who has made important contributions to the AI field for over a decade, and he’s been a major contributor to our team. We could not be more excited to have him take on this new responsibility."

Murati's announcement did not reference co-founder Luke Metz or any other departures. However, just 58 minutes later, Fidji Simo, OpenAI's CEO of applications, revealed on X that Zoph would be rejoining OpenAI. "Excited to welcome Barret Zoph, 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.

Luke Metz, a co-founder of Thinking Machines, had previously spent several years on OpenAI's technical staff. Sam Schoenholz, whose LinkedIn profile still indicates employment at Thinking Machines, also has a prior history with OpenAI. Barret Zoph formerly served as OpenAI's Vice President of Research and, before that, spent six years as a research scientist at Google.

Murati, who was OpenAI's Chief Technology Officer until September 2024, left to co-found Thinking Machines with Zoph and Metz. As CEO, Murati has since secured substantial funding for the startup, including a $2 billion seed round last July. The investment was led by Andreessen Horowitz, with participation from Accel, Nvidia, AMD, and Jane Street, among others, valuing the company at $12 billion.

While movement of talent between major AI firms is routine in Silicon Valley, the exit of co-founders from a startup less than a year after its launch is especially significant. Losing two co-founders at once—particularly one who held the CTO role—could be viewed as a substantial setback for Thinking Machines Lab, which had built a prominent team featuring former researchers from OpenAI, Meta, and Mistral AI.

The company has also experienced other key departures, including co-founder Andrew Tulloch, who left to join Meta in October. OpenAI itself has seen several co-founders depart to start or join rival companies, such as John Schulman, who left for Anthropic in August 2024 before joining Thinking Machines Lab as Chief Scientist upon its launch in February of last year.