Day four of the high-stakes civil trial between Elon Musk and Sam Altman concluded Thursday in a California federal court, offering critical insights into the conflict over OpenAI's conversion from a nonprofit to a for-profit entity. Musk returned to the witness stand, facing aggressive questioning by William Savitt, the lead attorney for Altman, and a brief session with a lawyer representing Microsoft, a co-defendant. The proceedings featured testimony from Jared Birchall, Musk's former money manager and a key financial figure in his companies. A primary focus of Musk's defense was countering allegations that his lawsuit was a strategic move to eliminate his AI competitor, xAI. When questioned about the rivalry, Musk characterized xAI as significantly smaller than its peers. He ranked the AI landscape with Anthropic in the lead, followed by OpenAI, Google, and various Chinese open-source models. Musk emphasized that his company represents only about one-tenth the size of OpenAI. This defense came despite Musk's recent aggressive business maneuvers, such as merging xAI with SpaceX and securing an option to acquire the coding startup Cursor for $60 billion. Tensions regarding the nature of AI risks also surfaced when Musk referenced a "Terminator" scenario or an existential robot apocalypse. US District Judge Yvonne Gonzalez Rogers firmly interrupted this line of questioning, ruling that discussions about human extinction were irrelevant to the specific legal claims at hand. The judge instructed Musk to focus on the trial's facts rather than hypothetical future dangers. Musk clarified that while the movie scenario is negative, the worst-case outcome would be AI causing human death. He denied that Tesla or other Musk ventures build weapons, stating a clear desire to avoid such a future. Birchall's testimony provided financial context to the dispute, confirming that Musk donated approximately $38 million to OpenAI through roughly 60 separate gifts. Savitt questioned whether these funds came with specific usage restrictions. Birchall suggested there was a mutual understanding among the founders that the money was not intended for unrestricted use at any time. The cross-examination also touched on a 2018 office-sharing agreement between OpenAI and Musk's Neuralink. Birchall testified that the building required constant armed security, a cost shared between the two entities, reflecting OpenAI's growing profile and security needs during that period. Birchall, who has served as corporate secretary for xAI and held leadership roles at Neuralink and The Boring Company, served as a bridge between Musk's various ventures and the financial details of the case. The first week of the trial ended with Birchall's testimony, as the jury will not be present on Friday. Next week, the nine-person jury is scheduled to hear from Greg Brockman, OpenAI's president and co-founder. Brockman is considered a pivotal witness due to personal diary entries that illuminate the period leading up to Musk's departure from the board in 2018. One entry quotes a team member admitting dishonesty toward Musk regarding their plan to continue as a for-profit entity without him. Brockman wrote that converting the organization to a B-corp without Musk's consent would have been morally bankrupt, noting that Musk was not easily fooled. OpenAI has described these diary entries as being cherry-picked by Musk's legal team to support their narrative. Despite this, the judge previously cited these writings as sufficient grounds to proceed with a jury trial. If the jury finds Musk liable, he has requested that Altman and Brockman be removed from their positions as officers and be forced to forfeit their equity in the company. The trial continues to unfold with the jury's perspective on these internal conflicts being central to the upcoming verdict.