Closing arguments began Thursday in a landmark trial that could reshape the artificial intelligence industry, as lawyers for Elon Musk and OpenAI presented their final cases in the billionaire's $150 billion lawsuit against the company he co-founded.

Musk, who was absent from court due to travel with President Trump in China, alleges through his legal team that OpenAI CEO Sam Altman and co-founder Greg Brockman violated the company's original nonprofit mission after he invested $38 million in the organization's early years. The lawsuit, filed in 2024, accuses the executives of shifting toward a profit-making model without his knowledge.

A central issue in the trial is whether Musk filed his lawsuit within the statute of limitations. OpenAI argues that Musk waited too long to bring his claims, which include breach of charitable trust and unjust enrichment. The judge has indicated that if the jury finds the lawsuit was filed too late, she will likely direct a verdict in favor of the defendants.

Musk's attorney Steven Molo focused his closing argument on questioning Altman's credibility, citing testimony from five witnesses who called the OpenAI CEO a "liar." These witnesses included Musk himself, former OpenAI chief scientist Ilya Sutskever, former CTO Mira Murati, and two former board members. "If you cannot trust him, if you don't believe him, they cannot win," Molo told jurors.

The trial's outcome could significantly impact the balance of power in the AI industry, as OpenAI, Musk's own AI company, and competitor Anthropic are all moving toward planned initial public offerings expected to be among the largest ever. In addition to monetary damages, Musk is seeking Altman's removal from OpenAI's board, which could potentially derail the company's IPO plans.

Separately, OpenAI reported a security incident involving employee devices, though the company stated that no user data, production systems, or intellectual property were compromised. The company is also reportedly exploring legal options regarding its relationship with Apple, according to Bloomberg News.