Claude Code introduces Mods system, letting developers rewrite this AI coding tool from within

Anthropic released a plugin-style Mods system for Claude Code, essentially middleware running inside the tool, allowing developers to hook into events such as tool calls, user prompts, and UI rendering using JavaScript or TypeScript functions, customize panels, intercept tool calls, or integrate new commands; built-in features like /diff are already implemented by Mods. Mods run with user permissions and are not sandboxed; Anthropic advises installing only from trusted sources, and enterprises can control which Mods are allowed to load; the first official Mod plugin, "You Should Know", launches an independent agent that monitors Claude's output and surfaces important information that might otherwise be missed.