Claude Sonnet 5: Anthropic's most agentic Sonnet model

Claude Sonnet 5 is Anthropic's mid-tier LLM, released in mid-2025, tuned for multi-step tasks and tool use. It occupies the practical middle ground between Haiku and Opus, with a focus on agentic workflows. The model is sometimes referred to by its API identifier claude-sonnet-4-5.