The early days of Microsoft’s OpenAI partnership have been revealed in detail in court documents this week.

When OpenAI was busy experimenting with AI-powered gaming bots, Microsoft CEO Satya Nadella and OpenAI CEO Sam Altman were in the early days of forming an AI partnership. Court documents from the ongoing Musk v. Altman trial have provided a rare look at the communications between Microsoft’s top executives about investing in OpenAI and fears the AI startup could “storm off to Amazon” and “shit-talk” Microsoft.

Just days after OpenAI showed a bot beating a Dota 2 professional in the summer of 2017, Altman responded to Nadella’s congratulations email with a proposal for a much bigger partnership with OpenAI to fund its next phase of AI research. OpenAI needed large sums of compute to expand the Dota 2 project, far beyond the Azure credits it was using from Microsoft at the time. “Probably something like $300 million at Azure list prices” according to Altman. This initially spooked some executives inside Microsoft.

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“For those numbers to make sense we’d have to be generating significant incremental revenue directly due to the deal ($500 million+) that couldn’t be gained in a more efficient way,” said Jason Zander, who was Microsoft’s Azure chief at the time, in an August 2017 email to Nadella.