“Claude Sonnet 4.5 is the best coding model in the world. It’s the strongest model for building complex agents. It’s the best model at using computers. And it shows substantial gains in reasoning and math.Code is everywhere. It runs every application, spreadsheet, and software tool you use. Being able to use those tools and reason through hard problems is how modern work gets done.Claude Sonnet 4.5 makes this possible. We’re releasing it along with a set of major upgrades to our products. In Claude Code, we’ve added checkpoints—one of our most requested features—that save your progress and allow you to roll back instantly to a previous state. ”