Thinking Machines cofounders Barret Zoph and Luke Metz are leaving the fledgling AI lab and rejoining OpenAI, the ChatGPT-maker announced on Thursday. OpenAI’s CEO of applications, Fidji Simo, shared the news in a memo to staff Thursday afternoon.

The news was first reported on X by technology reporter Kylie Robison, who wrote that Zoph was fired for “unethical conduct.”

A source close to Thinking Machines said that Zoph had shared confidential company information with competitors. WIRED was unable to verify this information with Zoph, who did not immediately respond to WIRED’s request for comment.

Zoph told Thinking Machines CEO Mira Murati on Monday he was considering leaving, then was fired today, according to the memo from Simo. She goes on to write that OpenAI doesn’t share the same concerns about Zoph as Murati.

The personnel shake-up is a major win for OpenAI, which recently lost its VP of research, Jerry Tworek.

Another Thinking Machines Lab staffer, Sam Schoenholz, is also rejoining OpenAI, the source said.

Zoph and Metz left OpenAI in late 2024 to start Thinking Machines with Murati, who had been the ChatGPT-maker’s chief technology officer.

This is a developing story. Please check back for updates.