OAKLAND, Calif — Elon Musk on Wednesday again took the stand in his blockbuster case against OpenAI for a second day of testimony in which he has argued the artificial intelligence company and its founders violated promises it made to him and the public.

Musk helped found and donated to OpenAI, which began as a nonprofit in 2015. Musk left the startup three years later after a power struggle with his co-founders. The public launch of ChatGPT catapulted OpenAI to commercial success in 2022.

On Tuesday, Musk took the stand to lay out the claims in his 2024 lawsuit. He argued that OpenAI took advantage of his donations and breached its founding agreement by putting commercial interests first. Musk framed the case as fundamental to “the entire foundation of charitable giving in America,” accusing his co-founders of stealing from the public good.

Musk is seeking more than $150 billion in damages from OpenAI and Microsoft, OpenAI’s biggest financial partner. He is also asking the court to remove OpenAI’s co-founder and CEO, Sam Altman, from the board, and to stop its recent shift to operate as a for-profit company.

OpenAI’s lead counsel, William Savitt, argued Tuesday that Musk filed the lawsuit because the world’s richest person “didn’t get his way at OpenAI.” The startup’s original nonprofit continues to oversee the for-profit company, and is working to redistribute billions of dollars generated by the commercial operation, he added.

The trial’s outcome could upend the AI landscape. OpenAI is a leading AI company. A win for Musk would also be a win for OpenAI’s competitors, from industry giants like Google to young companies like Anthropic and Musk’s own AI lab, xAI.

A loss for Musk would mean that OpenAI, which is now valued at about $730 billion, will be free to continue its commercial course just as it appears to be heading toward one of the biggest initial public offerings in history.

(The New York Times has sued OpenAI and Microsoft, claiming copyright infringement of news content related to AI systems. The two companies have denied the suit’s claims.)

Here’s What to Know:

— High-profile witnesses: Altman and several other key industry figures, including Microsoft’s CEO, Satya Nadella, and Mira Murati, OpenAI’s former chief technology officer, are slated to testify later in the trial.

— Trial logistics: The trial is expected to take about four weeks before a nine-person jury at the federal courthouse in Oakland, California. If the jury rules in Musk’s favor, U.S. District Court Judge Yvonne Gonzalez Rogers, who also oversaw a high-profile lawsuit against Apple over its control of the App Store, will decide on monetary damages and other remedies.

— Musk’s social media: Gonzalez Rogers on Tuesday called Musk, who assailed Altman on Musk’s social platform X before the trial, to the bench to discuss whether there should be a gag order preventing him from posting on social media about the trial. “How can we get things done without you making things worse outside the courtroom?” Gonzalez Rogers asked. The judge asked Musk and Altman to start with a “clean slate” and “keep things to a minimum” on social media. They agreed, and Musk has thus far complied.

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This article originally appeared in The New York Times.

By Cade Metz and Mike Isaac/Brennan Smart
c. 2026 The New York Times Company