"If you use Fable, when it refuses for any random thing, it just is like, when was the last time you had a creation tool that was so editorially controlled?" Nadella said, as detailed in a transcript of his remarks shared with CNBC. "It doesn't make sense."
The criticism is notable because Microsoft has deep ties to Anthropic.
As of October, Microsoft's stake in OpenAI's for-profit entity is valued at $135 billion. The company also backs Anthropic through its Azure cloud services.
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Microsoft's relationship with Anthropic is particularly nuanced given its backing of OpenAI as well. While the company has invested billions in both startups, its own AI assistant Copilot is a direct competitor to Anthropic's Fable and OpenAI's ChatGPT. This situation highlights the complex and overlapping relationships that characterize the AI sector's current landscape.
Microsoft shares have fallen 17% so far in 2026, while the Nasdaq Composite has risen 11% over the same period.
Nadella said firms ought to be capable of cost-effectively building tailored models and leveraging proprietary data, while preventing that data from leaving their systems. "It can't be that there are only two companies in the world with token capital, and everybody else is renting it," he told engineers.
Through its Foundry service, Microsoft provides access to over 11,000 models, including those from Anthropic and OpenAI. The company is also merging its consumer and corporate Copilot products. Nadella said the unification is something "we should have done maybe day one."
On Thursday, a Chinese company called Moonshot AI unveiled an open-source model that it claims outperforms recent offerings from Anthropic and OpenAI.
The AI industry is marked by overlapping investments and direct rivalries. Nadella's criticism of Fable's editorial limits, while perhaps surprising given those ties, reflects the growing tension between platform providers and the AI startups they back. As Microsoft builds its own Copilot ecosystem, it must navigate competing interests with both OpenAI and Anthropic - firms that are simultaneously partners and competitors in the race for AI dominance.
Nadella's remarks come at a time when AI companies are grappling with balancing safety restrictions against user experience. The criticism from a major investor underscores the pressure on startups like Anthropic to refine their content moderation policies without alienating users. Meanwhile, Microsoft's own Copilot is integrating AI across its product suite, aiming to capture a larger share of the enterprise market. The tension between safety and usability is a recurring theme in the industry: Microsoft must balance its investments in both OpenAI and Anthropic while competing with their consumer products, and Anthropic faces the challenge of maintaining rigorous safety filters without frustrating users.
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