Anthropic's comms chief mocks OpenAI after cofounder's bizarre tweet about jacuzzis and the Middle Ages

• OpenAI has had a wild week.
• The company announced governance changes. And then key figures like Mira Murati and Bob McGrew left.

Tech rivalries are always a hot topic on X, and on Friday, an Anthropic executive couldn't help but take a jab at OpenAI.

The social media scuffle between the two companies follows a wild week for OpenAI.

On Thursday, the company announced it was overhauling its governance structure in order to become a for-profit benefit corporation no longer under the control of the company's nonprofit arm. It also said it would give its CEO, Sam Altman, equity in the company for the first time. The changes marked a full turn from the early days of OpenAI when it was a little-known nonprofit.

Its chief technology officer, Mira Murati, who briefly filled in for Altman during his surprise ousting last year, then announced she was leaving. Key researchers Bob McGrew and Barret Zoph said they were leaving soon after.

It's unclear if the departures were related to the governance changes, but tensions between OpenAI execs over its approach to developing artificial general intelligence, and its commitment to safety, a core part of the nonprofit's mission, have repeatedly spilled into public view.

OpenAI cofounder Wojciech Zaremba took to X on Friday to wax poetic about the latest high-profile departures. He likened the exits of Murati, Zoph, and McGrew to children dying in the Middle Ages.

"Their departures made me think about the hardships parents faced in the Middle Ages when 6 out of 8 children would die prematurely," he wrote. "Despite the profound loss, the parents had to accept it and find deep joy and satisfaction in the 2 who survived."

Zaremba said he had "cool memories" with each of the departing employees. With Zoph, he had a "fierce conflict about compute" that served as the genesis for OpenAI's latest AI model, o1. He also said he had a fond memory of McGrew, who he said reprimanded him for "doing a jacuzzi with a coworker." He did not elaborate. Murati, meanwhile, was a witness to his engagement, he wrote.

Sasha de Marigny, an executive at OpenAI's rival Anthropic, was not impressed by Zaremba's reminiscences and historical allusions. Just hours later she wrote on X, "Happy to report that Anthropic's co-founders all still merrily work at the company. None have been lost to Middle Age plagues or jacuzzis."

Anthropic, incidentally, is home to a number of former OpenAI employees, including one of its cofounders, John Schulman, who left to join a team at Anthropic focused on developing AI technology safely.

Correction: September 27, 2027 — An earlier version of this story misstated when OpenAI announced its plans to restructure. It was Thursday, not Wednesday.