Changes from previous version
Positioned as the best coding model in the world at launch, with substantial reasoning and math improvements over Sonnet 4.
Release Summary
Anthropic's coding- and agent-focused Sonnet with checkpoints in Claude Code, computer-use gains, code execution in Claude apps, and the same $3/$15 pricing as Sonnet 4.
Timeline
September 29, 2025
Claude Sonnet 4.5 released
Anthropic ships Sonnet 4.5 with Claude Code checkpoints, VS Code extension, and API memory tools.