Claude Sonnet 5 is not frontier but has its uses

Sonnet 5 costs $3/$15 per million tokens, cheaper than Opus 4.8 and Fable 5. It offers faster speed and greater robustness in some agentic scenarios, but most users may prefer Opus 4.8 or Fable 5. The model was trained with assistance from the experimental 'Mythos' method.