Claude Sonnet 5.5
Anthropic announced Claude Sonnet 5.5 on 28 September 2026 as the second Claude 5.5 model. Anthropic says it is available now; API id claude-sonnet-5-5.
Also known as: Sonnet 5.5 · claude-sonnet-5-5
Official
Official
Anthropic’s Claude Sonnet 5.5 announcement is dated 28 September 2026 and introduces Claude Sonnet 5.5 as the second model in the Claude 5.5 family.
Anthropic says Claude Sonnet 5.5 is now available on all platforms, including Amazon Web Services, Google Cloud, and Microsoft Azure. Anthropic says developers can get started on the Claude Platform with `claude-sonnet-5-5`.
Anthropic says Sonnet 5.5 is priced the same as Sonnet 5 at $2 per million input tokens, $10 per million output tokens, and $0.20 per million tokens for cache reads.
Anthropic says Sonnet 5.5 is a clear upgrade over Claude Sonnet 5, runs 30%+ faster, and costs up to 30% less for most work.
Anthropic says Sonnet 5.5 is a faster, lower-cost complement to Claude Opus 5.5, and is strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets.
Anthropic says Sonnet 5.5 scores 70.6% on Terminal-Bench 4.0, compared to Sonnet 5’s 10.3%, and scores two points below Opus 5.5 on GDPval-AA.