Anthropic today announced a major upgrade to its AI model lineup with the official launch of Claude Sonnet 5, replacing the previous Sonnet 4.6 released in February. Positioned as the company’s best mid-range offering, the Sonnet series sits between the lightweight Haiku and the flagship Opus. According to Anthropic, Sonnet 5 is “the most autonomous Sonnet model yet,” capable of planning tasks independently, using tools like browsers and terminals, and running autonomously for extended periods—tasks previously achievable only with larger, more expensive models.
In terms of performance, Sonnet 5 significantly narrows the gap with the top-tier Opus 4.8, while maintaining a much lower price point. Starting today, the model becomes the default option for Claude Free and Pro users. Anthropic also simultaneously released its most powerful models, Mythos 5 and Fable 5, further expanding its product portfolio. For developers and enterprise users, Sonnet 5 offers a promotional rate of $2 per million input tokens and $10 per million output tokens, valid through August 31, 2026, after which standard pricing will apply.