Anthropic releases Claude Sonnet 5.5, a faster and cheaper model that nearly matches Opus 5.5 on several benchmarks

Anthropic has released Claude Sonnet 5.5, the second model in its Claude 5.5 family. The company says it runs more than 30 percent faster than Sonnet 5 and costs up to 30 percent less for most work.

Anthropic positions Sonnet 5.5 as a quicker, cheaper partner to Claude Opus 5.5, aimed at well-scoped everyday jobs such as bug fixes and polished documents, slides and spreadsheets. Opus 5.5 remains the model for complex work that needs careful judgment. A third model, Claude Haiku 5.5, is meant for high-volume, cost-sensitive use and is due in the coming weeks.

The biggest jump is in coding. On Terminal-Bench 4.0, an agentic coding test, Sonnet 5.5 scores 70.6 percent, up from 10.3 percent for Sonnet 5. On CursorBench 4.0, built from real Cursor editor sessions, it reaches 55.5 percent against 34.1 percent for its predecessor, about two points behind Opus 5.5 at 57.8 percent. At High effort on FrontierCode, it scores 10 points above Sonnet 5 at roughly one fifteenth of the cost per task.

Knowledge work shows a similar gap. On GDPval-AA, which covers tasks from 44 professions across nine industries, Sonnet 5.5 scores 1,844 points, nearly level with Opus 5.5 at 1,846 and about 400 points above Sonnet 5 at 1,449. On OSWorld 2.1, a computer-use test, Sonnet 5.5 scores 80.1 percent against 57.0 percent for Sonnet 5, and on Humanity's Last Exam with tools it reaches 64.5 percent, up from 54.9 percent. It is also the first Sonnet model to beat Pokémon Red using only screenshots.

Token prices do not change: $2 per million input tokens, $10 per million output tokens and $0.20 per million tokens for cache reads. Anthropic says the savings come from the model needing far fewer tokens for the same work. On several benchmarks, Sonnet 5.5 at Low or Medium effort beats Sonnet 5's best score for about a tenth of the cost per task. There is one quirk: at its highest effort setting it scores worse on FrontierCode than one step lower, because it more often calls a code-review function that splits work across sub-agents, sometimes causing timeouts or changes outside the task.

Anthropic says its own testing and that of outside testers still shows Opus 5.5 clearly ahead on complex, open-ended work that needs sustained judgment. Early testers noticed how quickly Sonnet 5.5 understands a codebase and how it batches tool calls, which cuts steps and cost.

Because its cybersecurity skills are comparable to Opus 5's, Sonnet 5.5 is the first Sonnet model to launch with cyber safeguards and fallbacks. Requests involving high-risk cybersecurity tasks are visibly rerouted to Sonnet 5, and qualified professionals can apply for tiered access through an expanded Cyber Verification Program. Anthropic has also added classifiers against distillation attacks.

Sonnet 5.5 is available now on Amazon Web Services, Google Cloud and Microsoft Azure, and through the Claude Platform.