SAN FRANCISCO: The board of directors of OpenAI, the high-flying artificial intelligence start-up, said in a note to employees on Sunday night that its former chief, Sam Altman, would not be returning to his job while naming his second interim replacement in two days.

Hours later, in another head-spinning move, Microsoft said it was hiring Altman and Greg Brockman, OpenAI’s president and a company co-founder who quit in solidarity with Altman. The two men will lead an advanced research lab at Microsoft. At OpenAI, Emmett Shear, the former chief executive of Twitch, will replace Mira Murati as interim chief, the board said. Murati, a longtime OpenAI executive, had been appointed to that role after Altman’s ouster.

At Microsoft, Satya Nadella, the tech giant’s chief executive, said Altman would be chief executive of the new research lab, “setting a new pace for innovation,” in an apparent contrast to the OpenAI board’s desire for caution in developing A.I. technology. Nadella noted in a post to X that Altman’s new group will operate as an independent entity within Microsoft. Altman responded cryptically, writing on X, “the mission continues.”

Altman’s firing startled the tech industry and OpenAI’s investors, which include Microsoft, Sequoia Capital and Thrive Capital. Microsoft, which has invested more than $13 billion in OpenAI, only learned of Altman’s exit one minute before it was announced, while other investors discovered that he had been forced out via social media.

The departure of Altman, 38, also drew attention to a rift in the A.I. community between people who believe A.I. is the most important new technology since web browsers and others who worry that moving too fast to develop it could be dangerous. Sutskever, in particular, was worried that Altman was too focused on building OpenAI’s business while not paying enough attention to the dangers of A.I.

Since OpenAI released its hit ChatGPT chatbot almost a year ago, artificial intelligence has captured the public’s imagination, with hopes that it could be used for important work like drug research or to help teach children. But some A.I. scientists and political leaders worry about its risks, such as jobs getting automated out of existence or autonomous warfare that grows beyond human control.

Altman’s exit also drew attention to a rift between those who believe A.I. is the most important new technology since web browsers and others who worry that moving too fast to develop it could be dangerous