Anthropic Accuses Alibaba's Qwen Lab of 'Largest Known Distillation Attack' in Letter to Senators, Now Public

Anthropic·medium signal

A letter Anthropic sent to Senators Tim Scott and Elizabeth Warren — dated June 10 and surfacing publicly this week — accuses Alibaba and its Qwen lab of running what Anthropic calls the largest known model-distillation attack against it to date. The claim escalates the open-weights-vs-frontier-lab tension and feeds directly into the ongoing US export-control story around Anthropic's top models. It also raises an unresolved question for the field: how do you even prove distillation from API outputs at scale?