Claude Sonnet 5.5 launches with 70.6% on Terminal-Bench 4.0
Anthropic announced Claude Sonnet 5.5, the second model in the Claude 5.5 family, positioned as a faster and cheaper complement to Opus 5.5. It generates output 30%+ faster and costs up to 30% less per task than Sonnet 5. On Terminal-Bench 4.0 it scores 70.6% versus Sonnet 5's 10.3%; gains also show on FrontierCode, CursorBench, GDPval-AA and OSWorld 2.1, with some results near Opus 5.5. Token pricing is unchanged at $2 input / $10 output per million, with $0.20 cache reads, but fewer tokens are needed per task. It is the first Sonnet released with cybersecurity safeguards that fall back to Sonnet 5 for high-risk requests, plus anti-distillation classifiers and preserved thinking. Relevant to engineers choosing models and budgeting agentic coding.