Co-founder of $12B AI startup Thinking Machines fired after workplace relationship surfaced

According to sources cited by the Wall Street Journal, Zoph was dismissed on Jan. 14 following a meeting with Murati.

During that meeting, Zoph reportedly admitted to Murati that he had a romantic relationship with a junior colleague that began while both were working at OpenAI, the developer of ChatGPT. Shortly after the disclosure, the woman left Thinking Machines and returned to OpenAI.

Zoph and two others also advocated during the meeting for him to have more decision-making power, prompting Murati to question why he had not been fulfilling his responsibilities in recent months. Murati had expressed concerns about Zoph’s productivity in recent months after discovering last summer that he was dating a junior colleague who did not report to him.

Co-founders of AI startup Thinking Machines Lab, Mira Murati (L) and Barret Zoph. Photo from AFP and LinkedIn

Murati, a former OpenAI CTO, told staff on Jan 14. that Thinking Machines had terminated Zoph’s employment due to "unethical conduct," according to Fortune.

Zoph told the Wall Street Journal that he was fired after Murati learned he was negotiating with another company and said Thinking Machines never cited performance issues to him.

"At no time did [Thinking Machines Lab] cite to me any performance reasons or any unethical conduct on my part as the reason for my termination and any suggestion otherwise is false and defamatory," he said.

OpenAI’s chief executive of applications, Fidji Simo, said Zoph’s hiring had been in the works for weeks and added that she did not share Thinking Machines’ concerns about his ethics.

Founded in 2025 by Murati and a group of former OpenAI executives and researchers, Thinking Machines Lab quickly became one of Silicon Valley’s most closely watched AI startups. The company raised about $2 billion in July in a record-setting seed funding round that valued it at roughly $12 billion. Bloomberg reported that the company was in talks to raise additional funding at a valuation of up to $50 billion.

Despite the fundraising success, the startup has struggled to retain talent. Andrew Tulloch, considered one of the lab’s co-founders, left late last year to join Meta’s AI efforts. Last week, Simo announced on X that Zoph, Luke Metz, and Sam Schoenholz were returning to OpenAI. Two additional Thinking Machines researchers, Lia Guy and Ian O’Connell, also departed, with Guy joining OpenAI.