Claude’s changing system prompt is part of the product

Anthropic’s revised consumer-system prompts changed instructions around copyrighted text, generated images and response style. Simon Willison compared the versions after the documentation moved to an index with separate model pages and retained historical prompts.

The pages are available as Markdown, which makes tracking their changes straightforward. A prompt diff shows what the product is now instructing the model to do, even when the model name stays the same.

These are prompts for Claude’s consumer chat surfaces, not Claude Code or Cowork. They can help explain a behavioral change, but a changed instruction alone does not isolate its effect from model training or other product changes.