Claude Sonnet 5.5 Reaches No. 3 on Agent Arena After Anthropic Launch

Claude Sonnet 5.5, Anthropic's new fast Sonnet-class model, has entered Agent Arena at No. 3 in Max mode with a 12.52% net improvement score, sharply above Claude Sonnet 5 High at 4.40%. The ranking puts the model just behind Claude Fable 5.1 Max and Claude Opus 5.5 High, while its strongest Arena signal is command-line recovery, where it ranks first among listed models.