> ## Documentation Index > Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Mods overview > Add panes, commands, and tool call rules to Claude Code with a mod. See what a mod can do, how to make or install one, and where mods run. A mod is a [plugin](/docs/en/plugins/overview) that changes how Claude Code looks and behaves. It's made of JavaScript or TypeScript event handlers: Claude Code calls one when an event happens, such as a tool call, a submitted prompt, or a part of the interface being drawn, and the handler can watch the event, change it, or take it over. Use a mod to add a feature of your own to Claude Code, such as a pane that charts how full your context is after each request. For the files in a mod and a complete example, see [How a mod works](#how-a-mod-works). Claude Code's existing [hooks](/docs/en/hooks) also run on events, as a shell command, HTTP request, or prompt you configure in a settings file. A mod's handlers are functions that run inside Claude Code instead. Claude Code calls both kinds hooks: on these pages, "hook" means a mod's handler, and the settings-file kind is a "settings hook". ## What a mod can do Settings hooks, skills, status lines, and MCP servers work from outside Claude Code: each one runs a script, or gives Claude text or tools. A mod runs inside Claude Code, so it can do things they can't: * **Draw an interface you can use**: a pane beside the transcript or a band above the prompt, with tabs, buttons, and text fields. See [Draw in the interface](/docs/en/plugins/mods/interface). * **Redraw Claude Code's own interface**: replace or restyle parts Claude Code draws itself, such as a tool call's row, the spinner, or the dialog Claude asks questions in. See [Change what Claude Code already draws](/docs/en/plugins/mods/interface#change-what-claude-code-already-draws). * **Step into a tool call or a request**: for example, hold a tool call while you ask the user a question, answer it without running the tool, or send one request to a different model. See [Guard or change a tool call](/docs/en/plugins/mods/events#guard-or-change-a-tool-call) and [Follow a turn](/docs/en/plugins/mods/events#follow-a-turn). * **Run your own code on a command**: a `/command` that runs your function at once, with no Claude turn, even while Claude is working. See [Add a command or a tool](/docs/en/plugins/mods/api#add-a-command-or-a-tool). * **Share data between hooks**: a mod's hooks share the variables in its file, so what one hook records, another can show. For example, one hook can count tool calls while another shows the count beside the spinner, or one can read each request's token usage while another charts it in a pane. See [React to events](/docs/en/plugins/mods/events). Mods work in the Claude Code CLI and in the Code tab of the Claude Desktop app. See [Where mods run](#where-mods-run) to understand how they behave elsewhere, such as in the VS Code extension, `claude -p`, and cloud sessions. If a settings hook, a skill, or an MCP server already does what you need, [compare them](#compare-mods-settings-hooks-skills-and-mcp-servers) before you write a mod. To manage mods for an organization, see [Manage mods for your organization](/docs/en/plugins/mods/admin). ## Get a mod You can start with a mod in one of three ways: * **Use one you already have**: some of Claude Code's own features are mods, such as `/diff`. See [Mods built into Claude Code](#mods-built-into-claude-code). * **Make one**: describe what you want in a Claude Code session, and Claude writes the mod. See [Ask Claude for a mod](/docs/en/plugins/mods/create#ask-claude-for-a-mod). To learn how a mod's code works, [write one yourself](/docs/en/plugins/mods/create#write-a-mod-yourself). * **Install one**: see [Install or update a mod](#install-or-update-a-mod) ### Install or update a mod A mod is code that runs with your permissions. It can read and write your files, start processes, and make network requests. Install mods only from authors and marketplaces you trust. See [Decide whether to trust a mod](#decide-whether-to-trust-a-mod). A mod installs as a plugin, from a marketplace. Give the plugin's name, an `@`, and the marketplace's name. These examples install a plugin named `token-chart` from a marketplace named `your-org`: * In a Claude Code session, run `/plugin install token-chart@your-org`. * In your shell, run `claude plugin install token-chart@your-org`. [Install plugins](/docs/en/plugins/install) covers marketplaces, scopes, the VS Code extension and the Desktop app, and [keeping plugins updated](/docs/en/plugins/install#keep-plugins-updated), all of which apply to a plugin that contains a mod without changes. If you install or update a mod from your shell while a session is open, run `/reload-plugins` in that session to load it. Otherwise it loads the next time you start Claude Code. ## Decide whether to trust a mod A mod is code that runs with your permissions, inside Claude Code. Install mods only from authors and [marketplaces you trust](/docs/en/plugins/security). ### What a mod can reach A mod runs with your permissions, so before you install one, know what it has access to. Once it loads, a mod can: * **Act on your machine as you**: read and write files anywhere your user account can, start programs, and make network requests * **Read your secrets**: environment variables and settings files, including an API key you keep in either * **See your session**: every prompt you send and every tool call Claude makes * **Change your session**: rewrite a prompt or a tool call, submit a prompt as if you had typed it, or send a message to another of your sessions * **Act without asking you**: approve a tool call before you're asked * **Spend your usage**: call a model on your plan or API key A mod that approves tool calls can approve one that an `ask` rule would prompt for, or that one of your own `PreToolUse` hooks blocked. [Extend permissions with hooks](/docs/en/permissions#extend-permissions-with-hooks) lists what such a mod can approve, including when it can approve a call that a `deny` rule refuses. A mod can restyle much of Claude Code's interface, but not the permission prompt. It can't change what a prompt shows you. ### List what a mod does before you install one Before you install a mod, you can list which events it hooks and what it asks Claude Code to do, such as read a file or make a network request, without running it. Get the plugin's files first, for example by cloning its repository. Then, in your shell, run `claude plugin validate` on the plugin's directory: ```bash theme={null} claude plugin validate ./some-mod ``` The `hooks:` and `calls:` lines in the output list the events the mod handles and what it asks Claude Code to do. [Review what a mod can do](/docs/en/plugins/mods/admin#review-what-a-mod-can-do) shows the output and which calls to look for. ## Turn mods on or off Mods require Claude Code v2.1.287 or later, and they're on by default. In your shell, run `claude --version` to check, and update Claude Code if yours is older. To turn mods off, choose how many to stop, and for how long. To turn them back on, undo the same change: * **One mod**: disable or uninstall its plugin from the [**Installed** tab in `/plugin`](/docs/en/plugins/install#manage-installed-plugins) * **Every installed mod, for one session**: start Claude Code with [`--safe-mode`](/docs/en/cli-reference#cli-flags), which also leaves out your other customizations * **Every mod you installed, in every session**: set [`"disableAllHooks": true`](/docs/en/settings-reference#disableallhooks) in `~/.claude/settings.json`. Your settings hooks and custom status line stop too. What your organization manages keeps running. If you use Claude Code through an organization, an administrator can also limit which mods load. Administrators start at [Stop user-installed mods from loading](/docs/en/plugins/mods/admin#stop-user-installed-mods-from-loading). To find out whether mods can load for you, see [Check whether mods can load](/docs/en/plugins/mods/troubleshoot#check-whether-mods-can-load). If you set `CLAUDE_CODE_ENABLE_FUNCTION_HOOKS` during early access, remove it. Claude Code v2.1.287 and later ignores it, so setting it to `0` doesn't keep mods off. ### See which mods a session loaded To see which mods a terminal session loaded, run `/plugin` at the Claude Code prompt. A dim line under the tabs gives the count and the names, such as `1 mod active · first-mod`. If a mod you installed isn't named there, see [Find out why a mod does nothing](/docs/en/plugins/mods/troubleshoot#find-out-why-a-mod-does-nothing). ## How a mod works A mod is a [plugin](/docs/en/plugins/overview) whose code registers event handlers, called hooks. Claude Code runs a hook when its event happens, such as when Claude calls a tool or when the spinner is drawn. A small mod has three files: ```text theme={null} first-mod/ ├── .claude-plugin/ │ └── plugin.json └── hooks/ ├── hooks.json └── register.js ``` * **`plugin.json`**: the plugin's [manifest](/docs/en/plugins/manifest-reference) * **`hooks.json`**: [points to your code file](/docs/en/plugins/mods/reference#files) * **`register.js`**: [your code](/docs/en/plugins/mods/create#write-a-mod-yourself), called the hooks module. It tells Claude Code which events to run your functions on. This is a complete `register.js`. It counts the tool calls Claude makes and shows the count beside the spinner while Claude works, as in `Thinking · tool calls: 3…`. ```javascript hooks/register.js theme={null} // The count, shared by the two hooks below let calls = 0 // Claude Code calls this once when the mod loads export function register(on) { // Runs each time Claude is about to use a tool on('tool.call', async ($, e, next) => { calls += 1 // Ask Claude Code to draw the interface again, so the new count shows $.ui.invalidate('ui.render') // Let the tool run as usual return next(e) }) // Runs each time Claude Code draws the spinner on('ui.render', { component: 'Spinner' }, async ($, e, next) => { // Keep Claude Code's spinner, with the count added after its word return next({ ...e, props: { ...e.props, suffix: ' · tool calls: ' + calls + '…' } }) }) } ``` The file registers two hooks, and both use the `calls` variable at the top: * **The [`tool.call`](/docs/en/plugins/mods/reference#tools) hook** runs each time Claude is about to use a tool. It adds one to `calls`, asks Claude Code to draw the interface again, and lets the tool run as usual. * **The [`ui.render`](/docs/en/plugins/mods/reference#interface) hook** runs each time Claude Code draws the spinner. It keeps Claude Code's own spinner and adds the count after the word. This recording shows the mod at work. Watch the spinner line above the prompt box: while Claude lists a directory and reads two files, it reads `Thinking · tool calls: 1…`, then `2…`, then `3…`.