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View this X/Twitter post from @claudeai published on 28 settembre 2026 alle ore 18:03. This post contains 3 videos and 5 images.
Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family. It’s a clear upgrade over Sonnet 5, runs more than 30% faster, and costs up to 30% less for most work.
Sonnet 5.5 improves on Sonnet 5 across benchmarks, in some cases dramatically. It’s a faster, lower-cost complement to Claude Opus 5.5, strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets.
Sonnet 5.5 is priced the same as Sonnet 5, but it typically needs far fewer tokens to do the same work. In our testing, it costs up to 30% less per task than its predecessor. It also generates output more than 30% faster, making it our fastest Sonnet model to date.
On several benchmarks, Sonnet 5.5 at Low or Medium effort beats Sonnet 5’s best score for about a tenth of the cost.
Sonnet 5.5 also has a knack for design. It adds polish to user interfaces and follows templates to create slides that need minimal editing.
Like Opus 5.5, Sonnet 5.5 writes more clearly than our previous generation of models. Its speed also makes it well suited to fast iteration and collaboration on less complex tasks.
On our automated behavioral audit, Sonnet 5.5 improves on or matches Sonnet 5 on most measures of alignment and honesty. It’s also the first Sonnet model with cyber safeguards and fallbacks like those on our most capable models. Routine software development is unaffected.
Claude Sonnet 5.5 is available everywhere today; Claude Haiku 5.5 will join the family in the coming weeks. Read more: https://www.anthropic.com/claude-sonnet-5-5
