Microsoft’s relationship with OpenAI is reportedly cooling, with the Redmond giant turning off the flow of money to the AI startup.

Microsoft based much of its AI tech on OpenAI’s inventions, continuing to invest in the startup and help fund its growth and innovation. According to a report by The New York Times, citing interviews with 19 sources, the breaking point appears to have been OpenAI’s ouster of Sam Altman as CEO of the startup.

The Times reports that Microsoft began denying OpenAI more funds, despite the $13 billion Microsoft had already funded, as well as the $5 billion OpenAI is expected to lose in 2024.

This is not the first indication that the relationship between the two companies is fraying. Microsoft hired Sam Altman and Greg Brockman when they were ousted from OpenAI, as well as made an offer for any OpenAI employees that wanted to join them. Altman and Brockman returned to OpenAI in short order, but many feared the damage was done.

What appeared to be cracks in the relationship appeared shortly after, with Microsoft releasing its own home-grown “MAI-1” AI model. While not nearly as powerful as OpenAI’s models, Microsoft releasing its own model was an odd decision for a company so heavily invested in OpenAI.

Even more telling, Microsoft CEO Satya Nadella was quick to assure the industry that Microsoft had everything it needed to continue developing AI and innovating, even without OpenAI—a strange statement to make for a relationship Altman referred to as “the best bromance in tech.”

Microsoft also gave up its seat on OpenAI’s board, a seat it was given after Altman’s return. Microsoft made clear the startup needed to make changes to its governance, with the board seat being a reflection of that.

“At this point, I think it’s very clear that something has to change around the governance,” Nadella said in November 2023, adding that Microsoft would have “a good dialogue with their board on that.”

Despite wanting the seat on the board, Microsoft gave it up less than a year later, saying it was no longer needed.

“We accepted the non-voting board observer role at a time when OpenAI was in the process of rebuilding its board,” Microsoft said in mid-2024. “This position provided insights into the board’s activities without compromising its independence, and we appreciated the opportunity to serve as an observer during this period of change.

“Over the past eight months we have witnessed significant progress from the newly formed board and are confident in the company’s direction.”

“Given all of this we no longer believe our limited role as an observer is necessary,” Microsoft added.

While each of these points can be explained away individually, in light of the Times’ report, it’s hard not to take them as indications of a fracturing relationship.