Introducing Claude Sonnet 5, our most agentic Sonnet yet.

It makes plans, uses tools like browsers and terminals, and runs autonomously at a level that, just a few months ago, required larger and more expensive models. Sonnet 5 is a substantial improvement over its predecessor, Sonnet 4.6, on reasoning, tool use, coding, and knowledge work. Its performance is close to Opus 4.8, at lower prices. Early access partners found Sonnet 5 finishes complex tasks where previous Sonnets stopped short, and checks its own output without being asked. Sonnet 5 is now the default