Microsoft Anthropic stake gains $3.2bn as OpenAI dips
Microsoft's quarterly earnings reveal a $3.2 billion paper gain from its Anthropic investment, signaling a strategic shift in the tech giant's AI portfolio that challenges OpenAI's dominance in its cloud ecosystem.
Microsoft recorded a $3.2 billion paper gain on its Anthropic investment during the fourth quarter of its 2026 fiscal year, which ended June 30. This unexpected boost added 33 cents to the company's diluted earnings per share, helping push the total to $4.81 for the quarter. The milestone was enough to overshadow a contrasting $600 million write-down in the value of its longstanding AI partner, OpenAI.
The sudden surge in Anthropic's booked value stems from a massive infrastructure deal struck in November 2025. Microsoft poured $5 billion into the AI lab under a circular agreement that tethered the startup to Microsoft's cloud division. As part of that arrangement, Anthropic committed to purchasing $30 billion worth of Azure computing services.
For the European technology sector, this $30 billion cloud commitment represents a major shift in the competitive landscape. It guarantees immense, long-term revenue for Microsoft's cloud infrastructure division. It also signals that Anthropic is willing to align its computing needs heavily with a single provider, altering the dynamics of the global AI race.
Microsoft's relationship with OpenAI, meanwhile, showed signs of quarterly strain. The tech giant marked down its roughly 27% stake in the laboratory by $600 million, a move that reduced diluted earnings per share by 7 cents. Microsoft deliberately avoids reporting the direct revenue-share payments it receives from OpenAI, choosing instead to account only for the investment's fluctuating market valuation.
Viewed over the full fiscal year, the OpenAI position remains highly lucrative. Microsoft reported that the stake generated a $5 billion gain for the 12-month period, contributing 67 cents to the annual earnings per share of $17.95. However, the quarterly divergence between the two competing AI labs is highly unusual.
The fact that Anthropic generated nearly as much value in a single quarter as OpenAI did over the entire year explains why Microsoft broke its usual reporting silence. Microsoft does not routinely update the valuation of its Anthropic investment on a quarterly basis. The decision to highlight this specific gain demonstrates to investors that the company is actively diversifying its AI portfolio.
Ultimately, these shifting valuations are a minor footnote in Microsoft's broader financial engine. The company generated $90 billion in revenue and $35.8 billion in net income for the fourth quarter alone. Annual revenue reached $331.8 billion, anchored by net income of $133.7 billion.
