Anthropic accuses Alibaba of illicitly extracting Claude model capabilities

Anthropic has accused Alibaba, the Chinese technology and e-commerce group, of illicitly extracting the capabilities of its Claude AI models. According to a letter seen by Reuters, the company describes it as the largest known attack of its kind on Anthropic to date.

What Anthropic alleges

The operation is described as a "distillation" effort, which Anthropic has said involves training a less capable model on the outputs of a stronger one. The company says the campaign ran between April 22 and June 5, 2026, and generated more than 28.8 million exchanges with Claude through almost 25,000 fraudulent accounts.

In the letter, Anthropic says distillation is a way to accelerate China's ability to reach its advanced Mythos Preview capabilities. The campaign, it adds, was conducted by operators affiliated with Alibaba and Alibaba Qwen, the company's AI lab. Alibaba did not immediately respond to a request for comment.

The letter to senators

The letter is dated June 10 and was sent to Senators Tim Scott and Elizabeth Warren, the chair and ranking member of the U.S. Senate Banking Committee, ahead of a scheduled hearing on AI. Anthropic says in it that it supports U.S. government efforts to combat such attacks, including partnering with private-sector AI companies through threat-intelligence sharing and other exercises.

In April, the White House accused China of stealing U.S. AI labs' intellectual property on an industrial scale.

Earlier distillation campaigns

Anthropic said in a February posting that it had identified a campaign by Chinese AI startup DeepSeek — whose low-cost model shook the technology world in January 2025 — along with two other Chinese AI labs, to illicitly extract capabilities from Claude. It said DeepSeek's operation involved over 150,000 exchanges, Moonshot AI over 3.4 million, and MiniMax over 13 million.

The company said at the time that the campaigns were growing in "intensity and sophistication", and that addressing the threat would require "rapid, coordinated action among industry players, policymakers and the global AI community".

A widening dispute

Alibaba was added to the Pentagon's Chinese military companies list this month, a designation it is challenging. Two days after Anthropic sent the letter, on June 12, the Commerce Department imposed restrictions on the company's latest Mythos and Fable AI models because officials feared they could be deployed by military intelligence users in China and other countries of concern. Those restrictions resulted in Anthropic disabling access to the models globally.