Anthropic has given Claude Code something developers have been asking for since the tool started becoming part of everyday engineering work: a way to change how it behaves without waiting for the next official release.

The feature is called Mods. A Mod is a small TypeScript or JavaScript function that hooks into Claude Code events. It can rewrite a prompt before it reaches the model, inspect or change a tool call, add a button to the interface, or replace part of the built-in experience entirely.