Elon Musk was partly behind OpenAI's decision to partner with Microsoft, having pushed founder Sam Altman to the cloud provider in 2016.

In documents recently published related to the ongoing lawsuit between Musk - a former cofounder of OpenAI - and OpenAI, Musk is shown expressing a preference for Microsoft and calling Amazon CEO Jeff Bezos a "tool," reports The Information.

The Musk vs. OpenAI lawsuit, filed in August 2024, regards the AI startups' transition into a for-profit. Musk argued that the $44 million he invested in the company was with the understanding that they were "charitable contributions." Originally, he aimed to stymie the business restructure, even bidding $97 billion for the non-profit, but OpenAI successfully became a for-profit public benefit corporation called OpenAI Group PBC in October 2025, of which Microsoft holds a 27 percent stake.

Despite this, the lawsuit between Musk and OpenAI continues, with Microsoft dragged into the mix, being listed as a defendant - though the company has denied any "knowledge of any alleged duties or breaches by OpenAI, Altman, or Brockman" regarding its investments and partnership with OpenAI.

In an exhibit shared on Court Listener, the exchange between Musk and Altman is summarized, showing that Musk, in fact, pushed for OpenAI to go into partnership with Microsoft, writing negatively about alternative provider Amazon Web Services.

"In 2016, Musk expressed a preference for OpenAI to change its cloud services provider from Amazon to Microsoft. Shortly after, Musk helped arrange for Microsoft’s supply of Azure services," the exhibit explains, citing several email interactions between the parties.

Other exhibits show Musk contacting Satya Nadella on behalf of OpenAI regarding accessing compute, and later thanking Microsoft for its role in enabling OpenAI to beat a human player in the Dota 2 video game in 2017.

OpenAI has long maintained that Musk's lawsuits are little more than "ongoing harassment." In September, Musk filed another lawsuit alleging that OpenAI had stolen xAI's trade secrets through targeted hires. OpenAI responded that the lawsuit was baseless and just one of many from xAI CEO Elon Musk.

“This new lawsuit is the latest chapter in Mr. Musk’s ongoing harassment," the company said in a statement. "We have no tolerance for any breaches of confidentiality, nor any interest in trade secrets from other labs."