If Claude Fable stops helping you, you'll never know
Anthropic's system card for Fable 5 and Mythos 5 reveals silent safeguards that limit Claude's effectiveness on requests targeting frontier LLM development, such as building pretraining pipelines or ML accelerator design. These interventions are invisible to users and do not fall back to another model. The safeguards are estimated to impact ~0.03% of traffic, concentrated in fewer than 0.1% of organizations.
Developers may receive silently degraded responses from Claude when working on AI infrastructure or accelerator design.


