Anthropic · Claude Sonnet 5.5

Claude Sonnet 5.5

Released 28 September, six days after Claude Opus 5.5 (covered here in week 40), at Sonnet 5's API price of $2 input and $10 output per million tokens, with $0.20 cache reads and $2.50 cache writes. Anthropic states over 30% faster output and up to 30% lower cost per task than Sonnet 5. Its own table shows 70.6% on Terminal-Bench 4.0, ahead of Opus 5.5 at 66.4%, plus 55.5% on CursorBench 4.0 (Sonnet 5: 34.1%), 80.1% on OSWorld 2.1 (57.0%) and 1844 Elo on GDPval-AA v2.1 (1449), all vendor-reported. Ships with the same cybersecurity safeguards as Opus 5.5. Available on the Claude Platform, AWS, Google Cloud and Azure as claude-sonnet-5-5. Context window not stated on the page.