Claude Sonnet 4.5
Released on September 29, 2025
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.