Claude Sonnet 5.5

Claude Sonnet 5.5 is Anthropic's mid-tier model released 2026-09-28, succeeding Claude Sonnet 5. Anthropic reports it runs more than 30% faster than Sonnet 5 and can reduce the total cost of completing a task by as much as 30% (through faster output and fewer tool calls), while keeping the same list price of $2 / 1M input and $10 / 1M output ($0.20 / 1M cache reads, $2.50 / 1M cache writes). Text and image input, text output; 1,000,000-token context window and 128,000 max output tokens; reliable knowledge cutoff June 2026. It powers the free tier of Claude.ai and is available via the Claude API as claude-sonnet-5-5 and on AWS Bedrock, Google Cloud Vertex AI, and Microsoft Azure. Reported benchmarks: Terminal-Bench 4.0 70.6% (agentic coding), CursorBench 4.0 55.5%, OSWorld 2.1 80.1%, GDPval-AA v2.1 1844, AA-Briefcase 1811, Chartography 61.6%.