Microsoft's $5 billion bet on Anthropic produced a $3.2 billion paper gain in the June quarter, a one-period windfall that nearly matched the full-year return on its far larger OpenAI stake and padded diluted earnings per share by 33 cents. The company reported $4.81 diluted EPS for the quarter on $90 billion of revenue and $35.8 billion of net income.
The circular deal that printed money
The Anthropic investment dates to November 2025, when Microsoft put in $5 billion under a circular agreement that also committed the AI lab to buying $30 billion of Azure services. Microsoft does not mark the stake to market every quarter, but this time it did, and the resulting gain accounted for roughly 7 percent of quarterly EPS. For context, the entire fiscal year delivered $17.95 of diluted EPS on $331.8 billion of revenue and $133.7 billion of net income.
OpenAI was the drag this quarter
The OpenAI stake, by contrast, was marked down about $600 million, shaving 7 cents off diluted EPS. Microsoft owns roughly 27 percent of the lab and receives revenue-share payments it does not disclose, accounting for the investment through equity-method valuation instead. The write-down looks trivial against a $35.8 billion quarterly profit, but it stands out because Microsoft chooses to discuss the OpenAI mark quarterly while treating Anthropic as an occasional disclosure.
The full-year picture flips
On a full-year basis the script reverses. The OpenAI investment generated a $5 billion gain and added 67 cents to EPS for fiscal 2026. That means Anthropic delivered nearly as much accounting upside in three months as OpenAI did in twelve. Microsoft thought the contrast noteworthy enough to flag explicitly, a rare instance of the company drawing a direct line between the two competing labs in its earnings materials.
What the disclosure actually says
Neither figure tells you what the businesses are worth. The Anthropic gain reflects a valuation update on a circular commercial arrangement; the OpenAI mark reflects a quarterly equity-method adjustment on a stake that also throws off undisclosed revenue share. Both are accounting artifacts of partnerships Microsoft structured to lock in Azure consumption. The market got $90 billion of quarterly revenue and $35.8 billion of net income. The rest is footnotes.