Introducing Claude Sonnet 5.5

Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family. It’s a clear upgrade over Claude Sonnet 5, runs 30%+ faster, and costs up to 30% less for most work.

Sonnet 5.5 is a faster, lower-cost complement to Claude Opus 5.5. Where Opus 5.5 is built for complex work requiring careful judgment, Sonnet 5.5 is strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets. It’s also got a sharp eye for design. Claude Haiku 5.5, built for high-volume and cost-sensitive applications, will join the Claude 5.5 family in the coming weeks.

Performance. Sonnet 5.5 scores 70.6% on Terminal-Bench 4.0, an agentic coding evaluation, compared to Sonnet 5’s 10.3%. It scores two points below Opus 5.5 on GDPval-AA, a test of real-world work across a variety of occupations. And it’s strong on long-horizon work and image understanding—it’s the first Sonnet model to beat Pokémon Red working only from screenshots.

“In Epic’s early testing, Claude Sonnet 5.5 cleared the same quality bar you’d expect from a higher-tier model, holding up on a system design audit and a data flow review. The new model managed tens of thousands of lines of code for gameplay system architecture, kept responses snappy, handled multi-hour tasks, and delivered with less prescriptive prompting.”

Sonnet 5.5 shows gains in multiple areas of knowledge work. On GDPval-AA, which tests models on real-world tasks across 44 occupations and nine major industries, Sonnet 5.5 scores nearly level with Opus 5.5 and about 400 points above Sonnet 5. It’s close to Opus 5.5 in computer use and chart recognition, and clearly outperforms Sonnet 5 and GPT-6 Sol on long-horizon knowledge work.

Claude Sonnet 5.5 is now available on all platforms, including Amazon Web Services, Google Cloud, and Microsoft Azure. Developers can get started on the Claude Platform with claude-sonnet-5-5 . If you run Sonnet with thinking off, you’ll need to switch to the new between_tools setting, which keeps up-front thinking off, before moving to Sonnet 5.5. See our migration guide for details.

Collaboration. Like Opus 5.5, Sonnet 5.5 writes more clearly than our previous generation of models; early testers described it as a better partner for collaboration than Sonnet 5. Its speed also makes it well suited to fast iteration on less complex tasks.

Cost. Sonnet 5.5 is priced the same as Sonnet 5 at $2 per million input tokens and $10 per million output tokens, but it typically needs far fewer tokens to do the same work. Cache reads cost $0.10 per million tokens, half of Sonnet 5's $0.20. In our testing, it costs up to 30% less per task than its predecessor.

Speed. Sonnet 5.5 generates outputs 30%+ faster than Sonnet 5, making it our fastest Sonnet model to date.