OAKLAND, Calif. — Shivon Zilis had her back against the wall.

For more than six years, the tech executive had worked largely outside the public eye as a trusted confidante to Tesla CEO Elon Musk and his three co-founders at the artificial intelligence start-up OpenAI. But now, as the company’s recently launched ChatGPT soared, OpenAI CEO Sam Altman had discovered that Musk was planning a rival AI venture and poaching talent from the start-up, according to federal court testimony this week.