On May 13, OpenAI's commercial transformation lawsuit reached a pivotal moment as Sam Altman, CEO of OpenAI, appeared as a key witness. During the trial, a document signed by him on April 24 revealed his personal asset portfolio in detail, with its largest component being an investment in nuclear energy startup Helion valued at over $1.6 billion. Altman confirmed under oath that as of the end of 2025, his stake in Helion was worth more than $1.6 billion. He disclosed having first invested in this nuclear company in 2015, subsequently participating in multiple funding rounds. His initial commitment came in November 2021 during Series E financing led by himself, amounting to $375 million. He estimated holding approximately one-third of Helion shares, along with warrants allowing further stock purchases. Currently, Helion is engaged in advanced negotiations with OpenAI regarding power purchase agreements. Former OpenAI board member Shivon Zilis testified she felt "surprised" upon initially hearing about the Helion collaboration proposal since both Altman and Greg Brockman were investors in Helion. Elon Musk's attorney Steven Molo then questioned whether Altman had played "both sides." Altman stated he recused himself from decision-making processes and stepped down as chairman of Helion in March 2026. Additionally, Altman acknowledged conflicts of interest related to Reddit—he held approximately $300 million in shares ahead of Reddit's IPO in March 2024, shortly after which OpenAI entered into a content licensing agreement with Reddit. When directly asked about these potential conflicts, he frankly admitted them before the court recessed. The documents also indicated other assets held by Altman including Stripe ($632 million valuation), anti-aging firm Retro Biosciences ($258 million), and AI chipmaker Cerebras ($30 million).