Anthropic sent a letter dated June 10, 2026 to Senate Banking Committee Chair Tim Scott and Ranking Member Elizabeth Warren alleging that operators affiliated with Alibaba's Qwen AI lab conducted what Anthropic called the largest known distillation attack on its Claude models. Per Anthropic's letter, the campaign ran from April 22 to June 5, 2026, generating more than 28.8 million exchanges with Claude through approximately 25,000 fraudulent accounts, targeting Claude's software-engineering and agentic-reasoning capabilities. Anthropic characterized the operation as illicit capability extraction via adversarial distillation. The disclosure is already driving legislative action: Senators Bill Hagerty (R-TN) and Andy Kim (D-NJ) are moving to add an amendment to defense legislation to blacklist or sanction entities conducting such campaigns. Alibaba has not publicly responded to the allegations.