Anthropic released Claude Sonnet 5, the most agentic Sonnet model. It plans actions, uses a browser and terminal, and handles tasks once needing larger models.

Sonnet 5 narrows the gap with Opus 4.8 at a lower cost. It completes complex tasks fully, unlike earlier Sonnet versions that stalled.

Testers say it writes tests to reproduce bugs, fixes code, and reverts changes to confirm issues without guidance. It also cuts false info, resists manipulation, and declines harmful requests better.

Sonnet 5 is now default on free and Pro plans and available on Max, Team, Enterprise, Claude Code, and API. Intro pricing lasts until August 31.