Anthropic has released Claude Sonnet 5, an update that is substantially improved over predecessor Claude Sonnet 4.6 in coding, reasoning, tool use, and knowledge work, according to the company.
Claude Sonnet 5 was introduced June 30. It can make plans, use tools like browsers and terminals, and run autonomously at a level that required larger and more expensive models a few months ago, Anthropic said. Safety assessments found that Sonnet 5 shows an overall lower rate of undesirable behaviors than Sonnet 4.6 and is generally safer to use in agentic contexts, the company also noted.
Claude Sonnet 5 is a drop-in upgrade for Claude Sonnet 4.6 with three behavior changes: adaptive thinking is on by default, manual extended thinking now returns a 400 error (it was deprecated on Claude Sonnet 4.6), and setting sampling parameters to non-default values also returns a 400 error. Further, Sonnet 5 uses an updated tokenizer that changes how the model processes text to improve performance. Anthropic said Sonnet 5 offers performance close to that of Opus 4.8 model but at lower prices.
Claude Sonnet 5 is available across all plans: it is the default model for Free and Pro plans, and it is available to Max, Team, and Enterprise users. It is also available in Claude Code and on the Claude Platform, where it launches with introductory pricing of $2 per million input tokens and $10 per million output tokens through August 31, 2026. After that date it will be priced at $3 per million input tokens and $15 per million output tokens. Developers can use Claude Sonnet 5 via the Claude API.