Claude Code 2.0 System Prompt Changes

Analyzing the system prompt changes between Claude Code 1.x and 2.0, powered by Sonnet 4.5 Claude Code 2.0 launched in September 2025, powered by Sonnet 4.5 which Anthropic calls the &ldquo;best coding model in the world.&rdquo; The announcement focused on checkpoints and the new VS Code extension, but the underlying prompt and tools changed as well. Claude Code isn&rsquo;t open source, and…