OpenAI chief executive Sam Altman took the witness stand in Oakland, California on Tuesday, delivering some of the most pointed testimony yet in a high-profile trial that has pitted two of Silicon Valley's most powerful figures against each other. Altman told the jury that Elon Musk — now a rival in the artificial intelligence industry through his own company, xAI — initially demanded 90 percent of OpenAI's equity when the company was being restructured. "An early number that Mr Musk threw out was that he should have 90 percent of the equity to start," Altman said. "It then softened, but it always was a majority."

Musk launched his lawsuit against Altman, OpenAI co-founder Greg Brockman, and Microsoft — one of OpenAI's principal investors — alleging that they betrayed the company's founding mission as a non-profit dedicated to developing artificial intelligence for the benefit of humanity. He claims he was induced to invest $38 million on those terms, only to see the company establish a for-profit subsidiary in 2019 as it sought the vast capital required to compete in an increasingly costly field. Musk is seeking $150 billion in damages and is pushing for OpenAI to revert to non-profit status, as well as for the removal of Altman and Brockman from leadership. Altman flatly rejected the narrative, telling the court: "It does not fit with my conception of the words 'stealing a charity' to look at what has actually happened here." He argued that Musk was fully aware of plans for a commercial arm and that Musk's unwillingness to commit in writing to any arrangement that did not leave him in long-term control was what ultimately ended his involvement. Musk departed OpenAI's board in 2018.

Altman used his testimony to portray Musk as a controlling personality poorly suited to running a research organisation. "I don't think Mr Musk understood how to run a good research lab," he said. "He had demotivated some of our most key researchers." He also recalled that when he and Brockman resisted Musk's demands for dominance, Musk predicted the venture had "a zero percent, not one percent, chance of success" without him. For their part, OpenAI's lawyers argue that Musk, now a direct competitor, is motivated by competitive grievance rather than principle. Spanish outlet El País noted that Altman, speaking in a notably calmer tone than his adversary, also testified that Musk had attempted to have Tesla absorb the company entirely — a detail that underscores the depth of the control he allegedly sought.

Musk's attorney, Steven Molo, sought to undermine Altman's credibility on the stand, pressing him pointedly on whether he was "completely trustworthy" and always told the truth. Altman replied that he believed himself to be a truthful person, though the exchange grew tense. The questioning drew on Altman's turbulent history: he was abruptly removed as OpenAI's chief executive in November 2023 by its board, which cited concerns about his transparency, before being reinstated five days later following a revolt by staff and investors. Separately, prosecutors from ten US states wrote to the Securities and Exchange Commission on Tuesday demanding that Altman be required to disclose potential conflicts of interest ahead of a possible initial public offering, alleging he has "a history of self-dealing."

The stakes of the trial extend well beyond the two men at its centre. OpenAI is reportedly preparing for a public offering that could value the company at around $1 trillion. An advisory jury is expected to deliver its view on any wrongdoing by the week of 18 May, after which Judge Yvonne Gonzalez Rogers will issue the final ruling on both liability and remedies. The case arrives at a moment of intense public and political scrutiny of artificial intelligence: a March 2026 Pew Research Center poll found that a majority of Americans believe AI will worsen rather than improve key aspects of life, with only 10 percent saying they are more excited than concerned about its growing role. Meanwhile, the global AI market is projected by the United Nations to reach $4.8 trillion by 2033, ensuring the outcome of this trial carries significant consequences for the industry's future direction.