What is a Claude Code mod?
A Claude Code mod, often just called a Claude mod, is a plugin made of JavaScript or TypeScript event handlers that run inside Claude Code. Claude Code calls a handler when something happens, such as a tool call, a submitted prompt or part of the interface being drawn. The handler can watch the event, change it, or answer it so the normal behaviour never runs. Anthropic shipped mods in Claude Code 2.1.287, and some built-in features such as /diff are now mods themselves.
What can a mod do that hooks, skills and MCP servers can't?
A mod can draw an interface you use (a pane beside the transcript or a band above the prompt), redraw parts of Claude Code such as the spinner or a tool row, hold or rewrite a tool call, add a slash command that runs code instantly with no Claude turn, and keep state between events. Settings hooks, skills and MCP servers all work from outside Claude Code, so they can't draw or keep in-process state.
How do I install a mod?
Mods install like any plugin. Run claude --version to check you have 2.1.287 or later. Add the mod's marketplace with /plugin marketplace add owner/repo, then install it with /plugin install name@marketplace, and run /reload-plugins. /plugin shows a line naming the mods that loaded.
How do I turn mods off?
Disable one mod from the Installed tab in /plugin. Start one session without installed mods with claude --safe-mode. Turn off every installed mod with "disableAllHooks": true in ~/.claude/settings.json.