This addendum to our Claude 3 Model Card describes Claude 3.5 Sonnet, a new model which outperformsour previous most capable model, Claude 3 Opus, while operating faster and at a lower cost. Claude 3.5Sonnet offers improved capabilities, including better coding and visual processing. Since it is an evolution ofthe Claude 3 model family, we are providing an addendum rather than a new model card. We provide updatedkey evaluations and results from our safety testing.