Claude Sonnet model releases

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%.

Anthropic's most agentic Sonnet model yet, with performance approaching Claude Opus 4.8 at a lower price. Built for coding, tool use (browsers and terminals), and autonomous multi-step agentic work, with selectable effort levels up to xhigh. A substantial upgrade over its predecessor Sonnet 4.6 on reasoning, tool use, coding, and knowledge work, with gains shown on SWE-bench, OSWorld-Verified, BrowseComp, and Humanity's Last Exam. The default model on the Free and Pro plans and available to Max, Team, and Enterprise users; in Claude Code and via the Claude API as claude-sonnet-5. Uses an updated tokenizer (same approach as Opus 4.7). Ships with real-time cyber safeguards enabled by default. Introductory API pricing of $2/$10 per Mtok through Aug 31, 2026, then standard $3/$15.

Anthropic's September 2025 Sonnet release, positioned as its strongest model for coding, agents, and computer-use workflows at launch. Proprietary API model with text, vision, and code capabilities, 200K context, and Sonnet-tier list pricing.