Microsoft CEO Satya Nadella took the stand to testify in the Musk v. Altman trial. Elon Musk named Microsoft as a defendant in his lawsuit against OpenAI and its CEO Sam Altman. Musk accuses Microsoft of aiding and abetting OpenAI's alleged breach of charitable trust. In this article Wall Street sees 'changing of the guard in AI' as Intel, AMD shares soar while Nvidia lags Musk co-founded OpenAI alongside Altman, Brockman and a handful of other executives and researchers in 2015. After a number of disagreements about OpenAI's direction, including a failed effort to join it with his automaker Tesla , Musk left the OpenAI board in 2018. He went on to launch a competing AI startup, xAI, which he merged with SpaceX earlier this year. OpenAI established a for-profit subsidiary in the months following Musk's departure, which allowed the company to raise outside funding more easily. Investors, including Microsoft, have since poured billions of dollars into OpenAI's for-profit arm, and the company's valuation has swelled to more than $850 billion. In October, OpenAI completed a recapitalization that cemented its structure as a nonprofit with an equity stake in its for-profit business. As part of that announcement, Microsoft disclosed that it held a roughly 27% stake in OpenAI's for-profit unit that was valued at around $135 billion. The relationship between OpenAI and Microsoft has shown signs of strain in recent months, even as both companies continue to tout it as strategic and core to their businesses. Late last month, the same day that jury selection kicked off in Musk v. Altman, the companies announced a revamped partnership agreement that allows OpenAI to cap revenue share payments and serve customers across any cloud provider. OpenAI said in a release that the agreement aimed to "simplify our partnership and the way we work together." Musk testified that he is not entirely against OpenAI having a for-profit unit, but he said it became "the tail wagging the dog." He repeatedly accused Altman and Brockman of enriching themselves from a charity while also reaping the positive associations that come from running a nonprofit. "Microsoft has their own motivations, and that would be different from the motivations of the charity," Musk said from the stand. "All due respect to Microsoft, do you really want Microsoft controlling digital superintelligence?" During a videotaped deposition shown in court last week, former OpenAI director Tasha McCauley recalled a discussion with Nadella and her fellow board members after the 2023 decision to dismiss Altman as OpenAI's CEO. "To the best of my recollection, Satya wanted to restore things to as they had been," McCauley said. The board members didn't think that was the right move, she said. — CNBC's Jordan Novet contributed to this report.