As Elon Musk’s case against OpenAI entered its second week, focus shifted to the company’s president, Greg Brockman. Over the course of several hours on Monday and Tuesday, Brockman faced questions about his emails, texts and one piece of evidence that has become central to the trial: his personal diary.

Musk’s lawsuit revolves around his allegation that Brockman, OpenAI and its CEO, Sam Altman, violated the founding agreement of the artificial intelligence firm by turning it into a for-profit entity. Musk argues that Altman and Brockman also unjustly enriched themselves in the process, essentially taking Musk’s money while deceiving him about their true intent for the business. He is seeking Altman and Brockman’s removal, the undoing of the for-profit restructuring and $134bn, which Musk wants distributed to OpenAI’s non-profit.

The journal, which Brockman kept during the company’s founding years circa 2015, has provided a consistent line of attack for Musk’s attorneys in the lead-up to the trial and during Brockman’s time on the witness stand. Musk’s team has presented numerous embarrassing excerpts, which OpenAI argues are taken out of context, to portray Brockman as self-interested and deceptive. Judge Yvonne Gonzalez Rogers cited Brockman’s entries multiple times in her decision to deny the AI firm’s motion to prevent the case from going to trial.

“Financially what will take me to $1B?” Brockman wrote in one entry in which he asked himself what he “really wants”.

During Brockman’s pre-trial deposition, Musk’s attorney brought up the journal a half-dozen times and asked why Brockman wrote “it would be nice to be making the billions”. Brockman responded that he meant it would be nice to have a revenue plan for the company outside donations.

“It’d be wrong to steal the non-profit from him. to convert to a b-corp without him. that’d be pretty morally bankrupt. and he’s really not an idiot,” Brockman wrote in another entry, which considered Musk’s role in the company.

Musk’s lead attorney, Steven Molo, called Brockman to testify on Monday and questioned what he meant by several of his entries, specifically asking about the line that Musk was “really not an idiot”.

“Did you mean to say that only an idiot would allow you to steal a charity?” Molo asked.

“No,” Brockman responded.

During a series of tense exchanges, Musk’s attorney also repeatedly read out portions of Brockman’s journal to the court and accused him of deceiving Musk.

“You weren’t honest with Elon Musk when you told him that you wanted OpenAI to remain a non-profit, were you?” Molo asked.

“We were absolutely honest with Elon,” Brockman responded.

OpenAI has denied all of Musk’s claims, stating that the Tesla CEO is merely an aggrieved former co-founder who left the company in 2018 after a failed bid to take control. They argue that Musk was always aware of the intent to create a for-profit structure and that OpenAI is still overseen by a non-profit that seeks to benefit humanity through AI.

OpenAI published a blogpost in January, titled “the truth Elon left out”, that attempted to show Musk’s team misused quotes and cut out relevant sections. Brockman meanwhile posted a lengthy thread on X on the same day as OpenAI’s blog, which gave his explanation of his diary entries.

“I have great respect for Elon, but the way he cherrypicked from my personal journal is beyond dishonest,” Brockman said on X, stating that he was looking forward to being able to tell his full version of events.

Musk’s case against OpenAI, Altman and Brockman isn’t the only lawsuit where the diary has drawn interest. In March, a federal judge ruled that OpenAI must give portions of Brockman’s journal to the New York Times and other plaintiffs in a case that accuses the AI firm of copyright infringement and illegally using newspapers’ intellectual property to train their AI models.

OpenAI’s lawyers began their cross-examination of Brockman on Monday afternoon and carried on into Tuesday, giving him a chance to reframe some of Musk’s accusations and reiterate his claim that he never deceived the world’s richest man. When asked about the diary, he downplayed its role as a record of events and referred to it as stream of consciousness writing that he never thought would be public.

“It’s very painful,” Brockman said. “It’s very deeply personal writings that weren’t meant for the world to see but there’s nothing in there that I’m ashamed of.”