Anthropic has introduced Claude Sonnet 5.5, the second model in its Claude 5.5 family, positioning it as a faster and more affordable counterpart to the higher-tier Claude Opus 5.5. According to the company, Sonnet 5.5 runs more than 30% faster than Claude Sonnet 5 and typically costs up to 30% less per task, even though its per-token pricing is unchanged.
Anthropic describes Sonnet 5.5 as strongest at well-scoped everyday tasks — fixing bugs and producing polished documents, slides, and spreadsheets — while Opus 5.5 remains the choice for complex, open-ended work requiring sustained judgment. The company says a third model, Claude Haiku 5.5, aimed at high-volume and cost-sensitive applications, will join the family in the coming weeks.
The performance jump is most visible in agentic coding. On Terminal-Bench 4.0, Sonnet 5.5 scores 70.6% versus Sonnet 5's 10.3%, and Anthropic says it lands two points below Opus 5.5 on GDPval-AA, a benchmark of real-world work across occupations. The model is also the first Sonnet to beat Pokémon Red using only screenshots, a test of long-horizon reasoning and image understanding.
On cost efficiency, Anthropic reports that Sonnet 5.5 at Low or Medium effort beats Sonnet 5's best scores on several benchmarks for roughly a tenth of the cost per task. At High effort on FrontierCode, it scores 10 points above Sonnet 5 at the same setting for about one fifteenth of the cost, and on CursorBench its best score comes within roughly two points of Opus 5.5.
Because its cybersecurity capabilities are comparable to Opus 5's, Sonnet 5.5 is the first Sonnet model to launch with cyber safeguards and fallbacks like those built for Anthropic's most capable models; its biology safeguards match Sonnet 5's. Anthropic says both target a narrow set of high-risk requests and do not affect routine software development or most life sciences work.
Early testers cited faster codebase comprehension, fewer tool-call steps, and stronger writing and design polish. Anthropic cautions that benchmarks capture only one facet of capability, and that Opus 5.5 remains clearly stronger at complex, open-ended work.