Claude Code adds 'Mods' system for customizing the tool from inside

Anthropic is adding a Mods system to Claude Code, middleware running inside the tool. Developers can use JavaScript or TypeScript to add custom panels, intercept tool calls, and wire up new commands.

Why it matters: Letting users intercept tool calls and reshape the interface turns a coding agent into a platform, much like editor extensions did for IDEs. It also gives teams a place to enforce policy and guardrails, which matters as agent permissions tighten, as with Apple's Full Disk Access changes.