After Microsoft invested $10 billion in OpenAI in early 2023, Elon Musk said in a social media post that OpenAI was “effectively controlled” by the tech giant.
Shivon Zilis, a confidante of Mr. Musk who had spent years working for his companies and had approved the Microsoft deal as a member of OpenAI’s board of directors, disagreed.
“You are naïve,” he told her.
Ms. Zilis, who is also the mother of four of Mr. Musk’s children, described her private conversation with the world’s richest man during testimony on Wednesday in a blockbuster trial in an Oakland, Calif., federal court that pits Mr. Musk against OpenAI and its chief executive, Sam Altman.
Mr. Musk sued OpenAI two years ago, accusing the artificial intelligence company of breaching its founding contract by putting commercial gain over the public good. He founded OpenAI as a nonprofit in 2015 with Mr. Altman and a group of A.I. researchers. But after a power struggle with Mr. Altman, Mr. Musk quit.
Mr. Altman and the other founders later attached a for-profit company to the A.I. lab and began raising billions of dollars from Microsoft and other investors. Now Mr. Musk is asking for $150 billion in damages and a court order that would unravel the for-profit company that OpenAI created. He also wants to remove Mr. Altman from OpenAI’s board of directors.
Ms. Zilis had a unique view of the yearslong struggle between Mr. Musk and Mr. Altman. She started working for OpenAI as an adviser in 2016; developed friendships with Mr. Altman and OpenAI’s president, Greg Brockman; and had a romantic relationship with Mr. Musk around the same time, according to her testimony.
Ms. Zilis worked as Mr. Musk’s de facto chief of staff, Mr. Musk said during his own testimony last week. Ms. Zilis denied on Wednesday that was her role, but she said she had worked for three of his ventures: OpenAI, the electric car company Tesla and the brain-implant company Neuralink.
OpenAI’s lawyers tried to paint Ms. Zilis as Mr. Musk’s woman on the inside at OpenAI. Mr. Musk, they say, was always aware of what was happening at the A.I. lab — in fact, Ms. Zilis kept him well informed — but he did not sue until OpenAI had a hit on its hands with the chatbot ChatGPT.
After Mr. Musk left OpenAI in 2018, Mr. Musk appeared to want her to stay on the board so she could keep him informed about its work, according to evidence in the trial. He also discussed with her poaching OpenAI employees for Tesla.
“Do you prefer I stay close and friendly with OpenAI to keep info flowing or begin to disassociate? Trust game is about to get tricky so any guidance for how to do right by you is appreciated,” she said in a text message to Mr. Musk.
“Close and friendly but we are going to actually try to move three or four people from OpenAI to Tesla,” Mr. Musk replied.
Mr. Brockman, OpenAI’s president, testified on Tuesday that when Ms. Zilis joined OpenAI’s board, many at the company were wary of her. But he said he had trusted her to keep her work with Mr. Musk separate from her involvement with OpenAI.
While Ms. Zilis was serving on the board, she told Mr. Brockman that she was pregnant but did not tell him that Mr. Musk was the father, Mr. Brockman said. He learned that Mr. Musk was the father from news reports, he said.
When Mr. Brockman asked Ms. Zilis about the reports, he said she told him that she had conceived through in vitro fertilization and that her relationship with Mr. Musk was platonic.
Ms. Zilis said on Wednesday that she had a romantic relationship with Mr. Musk going back at least a decade. But, during testimony, she said she had not revealed that Mr. Musk was the father of her children until a reporter from Business Insider contacted her to say the publication was about to release an article naming him as the father.
Ms. Zilis felt comfortable with OpenAI’s $10 billion deal with Microsoft while she was on the board but grew more concerned after she left the board in 2023 and after her conversation with Mr. Musk, she said.
Her worries escalated after OpenAI’s board fired Mr. Altman in late 2023 and Microsoft helped him get his job back five days later. She concluded the nonprofit was no longer in control of the for-profit company.
“I remember being terrified,” she said. “After that ouster happened, everything we put together over so many years with the nonprofit lost its teeth and it was not able to fulfill its role.”
Sarah Eddy, a lawyer for OpenAI, showed a document that Ms. Zillis wrote in 2017 in which she helped plan an event at Tesla, saying the electric car company planned to compete with the world’s leading A.I. companies. OpenAI’s legal team has repeatedly argued that Mr. Musk worked to compete with OpenAI through his own for-profit companies.
Mr. Musk acknowledged during his testimony that he had tried to fold OpenAI into Tesla that year.
Before Ms. Zilis took the stand, the court heard a video deposition from Mira Murati, who joined OpenAI in 2018 and served as its chief technology officer from 2022 until late 2024. Her testimony focused on the weeks before and after the brief firing of Mr. Altman.
Before Mr. Altman was fired, she said, she did not completely trust him, because he was not always candid with her and sometimes undercut her role as a key executive. “It was completely management related,” she said. “I was asking Sam to lead with clarity and not undermine my job.”
She also criticized OpenAI’s board over the way it handled Mr. Altman’s firing. She said the board had not been transparent about its reasons for firing Mr. Altman and had not understood the consequences.
“They were not prepared for the transition and stabilizing the company,” Ms. Murati said.
(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.)
