Greg Brockman concluded his testimony in Musk v. Altman on Tuesday with a stake list that runs the breadth of OpenAI's counterparty footprint. The number on his OpenAI shares was already public — close to $30 billion. [1] [2] What Brockman added under cross-examination, and what Shivon Zilis was asked to confirm Wednesday morning, is the catalog of holdings around it: $471 million in Stripe, $2.8 million in Cerebras (acquired in 2017, during the period when OpenAI was discussing a Cerebras acquisition), $817,000 in CoreWeave, $433,000 in Helion Energy, and 1 percent of Sam Altman's personal family office. [3] The paper's Tuesday standard on Brockman's first two days framed the trial as a fiduciary-disclosure document for the Cerebras IPO. Day Three made the document longer.

The Cerebras line is the one that travels. Brockman testified Monday that he bought Cerebras shares "during various moments when OpenAI discussed buying the chipmaker." [4] OpenAI considered acquiring Cerebras in 2017, prior to its for-profit shift; the deal fizzled. [3] In January OpenAI announced a $10 billion compute agreement with Cerebras for 750 megawatts running through 2028, with options for an additional 1.25 gigawatts and a $1 billion loan from OpenAI to Cerebras alongside it. Cerebras prices its IPO Tuesday, May 13, on the Nasdaq under CBRS at a $26.6 billion fully diluted valuation. The S-1/A filed last week names OpenAI as the anchor customer. The S-1/A does not catalog the OpenAI president's personal holdings of Cerebras stock, acquired during merger discussions. The prospectus sits at T-5.

Stripe is the largest of the disclosed positions. Brockman was Stripe's CTO for five years before OpenAI; the $471 million holding predates his OpenAI tenure and is not, on its face, a conflict. [3] Stripe is OpenAI's payments processor, which makes it a counterparty. Helion Energy is the Altman-Brockman overlap that hardens. Altman has invested hundreds of millions in Helion since 2015 and stepped down from its board in March, 2026, as OpenAI and Helion explored a power-purchase agreement. [4] Brockman began acquiring Helion shares in 2023; by year-end the position was worth $433,584. [3] The fusion company has a 2028 power-purchase agreement with Microsoft and a non-binding 2024 agreement with OpenAI to power data centers when its reactors come online. Two OpenAI executives now hold disclosed stakes in the same OpenAI counterparty.

CoreWeave is the third counterparty. Brockman began buying CoreWeave shares in 2019; the holding was valued at $817,365 in April. [3] OpenAI has committed up to $22.4 billion across multiple multi-year deals with CoreWeave since 2025. The Altman family-office stake — Brockman's 1 percent received in 2017 in lieu of Y Combinator stock — was disclosed in a 2017 email from Jared Birchall to Musk: "He compensated Greg on the side by giving him a percentage ownership of Sam's personal family office," Birchall wrote. "Naturally, Greg is going to have greater allegiance toward Sam as a result of this arrangement." [1] Musk forwarded the note to Brockman with two question marks. Asked under oath whether the arrangement compromised his loyalty to OpenAI's mission, Brockman replied: "I don't know I would say it quite like that." [1]

Zilis took the stand Wednesday morning. The former OpenAI board member, longtime Musk associate, and mother of four of Musk's children was asked to confirm Brockman's account of Musk's instruction that OpenAI engineers do months of unpaid work on Tesla's self-driving program — Brockman had named Zilis and Sam Teller as the proxies Musk used to manage that work. [2] The deeper question, in disclosure terms, is whether her testimony produces document evidence beyond Brockman's recollection that the Tesla work happened, and whether the Tesla 10-K's related-party schedule needs amendment to reflect uncompensated OpenAI engineering hours. The Tesla amended 10-K from April 30 already names $573 million in 2025 revenue from Musk-controlled entities. [5] The trial's record now sits one document deep into the question whether the related-party set is complete.

What the trial transcript becomes for Cerebras is the question this week answers. The fiduciary fight is the lawsuit's frame; the disclosure obligations are the trial's output. A stake acquired during merger discussions, held through the period the merger target became the customer, named under oath six trading days before pricing, is the kind of fact securities lawyers test against the 10b-5 standard for material omission. Cerebras has the weekend and Monday to amend the S-1/A. The OpenAI president's portfolio is now a paragraph in someone's risk factors. The trial continues. The IPO prices Tuesday. The two run on the same calendar.

-- KENJI NAKAMURA, Tokyo