Cofounders of Thinking Machines Barret Zoph and Luke Metz have left the new AI lab and rejoined OpenAI, ChatGPT-maker announced on Thursday. OpenAI’s CEO of applications, Fidji Simo, shared the news in a staff memo Thursday afternoon.

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

A source close to Thinking Machines said Zoph shared the company’s confidential 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 that he was considering leaving, then was fired today, according to a memo from Simo. He goes on to write that OpenAI does not share the same concerns about Zoph as Murati.

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

Another Thinking Machines Lab employee, Sam Schoenholz, has also joined OpenAI, the source said.

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

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