But his removal is a blow to Microsoft, which has invested $13 billion in OpenAI and has what amounts to a 49 percent stake in the company. Satya Nadella, Microsoft’s chief executive, introduced an expansive plan this year to use the technology developed at OpenAI in nearly all of Microsoft’s products, from the Bing search engine to its widely used business software. Mr. Altman joined him at a press event to announce the plans.
Microsoft said on Friday afternoon that it planned to continue to work closely with OpenAI.
“We have a long-term partnership with OpenAI, and Microsoft remains committed to Mira and their team as we bring this next era of A.I. to our customers,” Frank Shaw, a spokesman for the company, said in a statement. Microsoft’s stock price fell more than 1 percent in the last 30 minutes of trading, after Mr. Altman’s departure was announced.
OpenAI’s four-member board of directors is a mix of respected A.I. researchers, tech executives and A.I. policy experts, including Ilya Sutskever, the company’s chief scientist and co-founder, and Adam D’Angelo, chief executive of the question-and-answer site Quora. The board members could not be immediately reached for comment.
Current and former OpenAI employees were shocked by the news. As recently as Friday morning, they were discussing Mr. Altman as if he had a long future with the company. Researchers, entrepreneurs and investors outside the company were equally surprised, with many scrambling to determine why the OpenAI had made its decision.
Jack Altman, one of Mr. Altman’s younger brothers and the chief executive of the business software start-up Lattice, defended his sibling on X.
“More important than being one of the most brilliant and impactful people our industry has ever had,” he wrote, “Sam is one of the most generous and caring people I know. I’ve never met someone who has supported and lifted up more people around them than him. Couldn’t be a prouder brother.”