Claude Code adds Mods system so developers can change tool behavior and UI

Claude Code's new Mods system lets developers rewrite the AI coding tool from the inside

Anthropic released Mods, a plugin system for Claude Code. Developers write JavaScript or TypeScript functions that hook into tool calls, user prompts and interface rendering events.

Why it matters: Anthropic is opening Claude Code's internal extension points, and Mods run with user permissions outside the sandbox, so where you install them from affects runtime safety.