US controls halt new Anthropic, OpenAI models, accelerating open-source shift

Amid tighter US government controls on frontier AI models, Anthropic abruptly cut off access to its new Fable 5 and Mythos 5 models for all users, and OpenAI limited the release of a new model, exposing the risks of depending on closed-source systems. Against this backdrop, developers are reportedly accelerating their shift toward open-source (open weights) models.