Anthropic has introduced Claude Sonnet 5.5, the second model in the Claude 5.5 family. It is a clear upgrade over Sonnet 5, running more than 30% faster and reducing overall execution costs by up to 30% for most tasks.
Sonnet 5.5 is designed for well-scoped everyday tasks, bug fixes, and polished documents, slides, and spreadsheets. It serves as a faster, lower-cost complement to Opus 5.5, which is built for complex work requiring careful judgment. Token pricing remains unchanged from Sonnet 5 at $2 per million input tokens and $10 per million output tokens.
On benchmarks, Sonnet 5.5 scores 70.6% on Terminal-Bench 4.0—an agentic coding benchmark—compared to 10.3% for Sonnet 5 and 66.4% reported for Opus 5.5 on the same test. It is also the first Sonnet model to beat Pokémon Red operating solely from screenshots.
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. pic.twitter.com/UvXD8mDTF1
— Claude (@claudeai) September 28, 2026
Because its cybersecurity capabilities are comparable to Opus 5, it is the first Sonnet model to launch with cyber safeguards and fallbacks similar to those on Anthropic’s flagship models. Its biological safety safeguards remain unchanged.
Sonnet 5.5 is available on AWS, Google Cloud, Microsoft Azure, and the Claude Platform as claude-sonnet-5-5. Developers running Sonnet with thinking disabled must switch to the new between_tools setting prior to deployment. Claude Haiku 5.5 will join the family in the coming weeks.