Anthropic is the only major AI lab that hasn't signed the open-weights letter. In June it argued the same case, when Washington pulled Fable 5.

Chinese open-weight models are gaining steam against leading offerings from American companies. OpenAI and Anthropic did not sign the letter.

Twenty-five companies signed a letter defending open models days after a Chinese AI helped Hugging Face survive a hack triggered by OpenAI.

Can you guess who didn't sign on to the group letter?