Claude Sonnet 4.5 is a large language model from Anthropic with particular strengths in software coding, agentic tasks where it runs in a loop and uses tools, and in using computers. The model maintains focus for more than 30 hours on complex, multi-step tasks. Pricing remains the same as Claude Sonnet 4, at $3/$15 per million tokens. It is the most aligned frontier model Anthropic has released, showing large improvements across several areas of alignment compared to previous Claude models.