The stakes are high. Mr. Musk, who was not in the courtroom on Thursday because he was in China with President Trump, is asking for more than $150 billion in damages from OpenAI and Microsoft, OpenAI’s primary partner, and has said any damages would be shared with the OpenAI nonprofit. He is also asking the court to remove Mr. Altman from the start-up’s board and to stop a shift the company made last year to operate as a for-profit company.
Mr. Musk, Mr. Altman and other A.I. researchers founded OpenAI as a nonprofit in 2015, vowing to freely share its technology with the rest of the world. But Mr. Musk left the start-up in 2018 after a power struggle with Mr. Altman — well before the public launch of ChatGPT in 2022 catapulted OpenAI to commercial success, with Greg Brockman as its president.
Sarah Eddy, a member of OpenAI’s legal team, tried in her closing argument to dull the attacks on Mr. Altman’s credibility and to argue that there was never a firm agreement among the founders that could have been breached. “No one in this case, other than Elon Musk, has testified to any commitments or promises that Sam Altman or Greg Brockman or OpenAI made to Mr. Musk,” she said.
Ms. Eddy also repeatedly made the point that there was evidence that Mr. Musk himself had wanted to turn OpenAI into a for-profit enterprise and that he wanted “unequivocal control” over it.
She also contended that the lawsuit was invalid because the statute of limitations for filing a complaint had expired by the time Mr. Musk brought the suit in August 2024. And to counter Mr. Musk’s allegation that the other founders were guilty of “stealing a charity,” she pointed out that the OpenAI nonprofit still exists and controls the for-profit arm.
If Mr. Musk loses, Mr. Altman would likely solidify his control of OpenAI, which is now valued at about $730 billion and appears headed toward one of the largest initial public offerings in history. The company also would be free to pursue a data center expansion plan that could cost hundreds of billions of dollars.
Mr. Molo was unsparing in his attacks on Mr. Altman.
“Imagine that you’re on a hike, and you come upon one of those wooden bridges that you see on a trail, and it’s over a gorge,” Mr. Molo said. “There’s a river that’s 100 feet below and it looks a little scary, but a woman standing by the entry to the bridge says, ‘Don’t worry, the bridge is built on Sam Altman’s version of the truth.’”
He then asked the jury: “Would you walk across that bridge? I don’t think many people would.”
(The New York Times has sued OpenAI and Microsoft, claiming copyright infringement of news content related to A.I. systems. The two companies have denied the suit’s claims.)
Here’s what else to know:
Major stakes: The trial’s outcome could upend the A.I. landscape. A win for Mr. Musk, who has his own for-profit lab, xAI, would also be a win for OpenAI’s competitors, including industry giants like Google and young companies like Anthropic, as well as international competitors such as China’s DeepSeek.
Trial logistics: Closing arguments will be followed by jury deliberations. If the jury rules in Mr. Musk’s favor, 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.
Statute of limitations: Part of what the jury must decide is whether Mr. Musk brought his suit before the expiration of the statute of limitations. The statute of limitations for his breach of contract claim expires after three years, which means that Mr. Musk’s legal team must show that he was not aware — and had no way of knowing — that OpenAI had breached its founding agreement before August 2021.
A year later, Microsoft invested $1 billion in OpenAI’s new for-profit venture.
That investment has become one of the key points in Mr. Musk’s lawsuit against OpenAI. He claims that after OpenAI took the money — and an additional $12 billion from Microsoft over the next few years — it betrayed its founding mission to be a nonprofit dedicated to the creation of A.I. that is safe for the world.
Several months after suing OpenAI in 2024, Mr. Musk amended the suit to include Microsoft. He accused Microsoft of aiding and abetting OpenAI as the lab abandoned its founding contract as a nonprofit.
On Monday, Mr. Nadella took the witness stand to start the third week of a blockbuster trial in a federal court in Oakland, Calif.
Mr. Nadella said that even though OpenAI went on to enormous success after Microsoft’s investment, he did not think that the venture violated the original mission of the nonprofit. Nor did he believe Microsoft played a role in breaking OpenAI’s founding contract as a nonprofit.
“It has always been my view that the nonprofit approved the creation of the for-profit so that they could pursue the mission,” Mr. Nadella said.
As the chief executive of OpenAI’s biggest investor, Mr. Nadella had behind-the-scenes insight into the lab as it quickly expanded from a small research group into one of the most influential tech companies in the world. As OpenAI grew and Microsoft added to its investment, he said he never heard from Mr. Musk about his objections, even though “we have each other’s phone numbers.”
