Claude Code Mods Let Developers Customize the CLI and Desktop App

Anthropic has introduced Claude Code mods, JavaScript or TypeScript functions that let developers change how Claude Code behaves and looks. Mods can rewrite prompts, change or block tool calls, add interface elements, or replace built-in features. They ship inside plugins, so developers can install and share them through Claude Code's plugin system. (Anthropic's Claude Code mods announcement)

The launch turns Claude Code's customization layer into something developers can extend with small JavaScript or TypeScript modules instead of waiting for a built-in setting. Anthropic says you can write a mod yourself or ask Claude Code to create one. (Anthropic's Claude Code mods announcement)

Key Takeaways

• Customize behavior and interface: Mods can rewrite prompts, block or alter tool calls, respond to permission requests, and add or replace UI elements. (Anthropic's Claude Code mods announcement)
• Use existing plugins: Mods ship inside plugins, and Anthropic says they are available in the Claude Code CLI and desktop app (Anthropic's Claude Code mods announcement). The terminal needs Claude Code v2.1.287 or later, and the Desktop app v2.1.286 or later (Claude Code docs, "Mods overview").
• Ask Claude to build one: Claude Code can write, install, and hot-reload a mod in the current session (Anthropic's Claude Code mods announcement). A mod written by Claude loads only in the session that made it until you copy its directory out and load or install it elsewhere (Claude Code docs, "Create a mod").
• Treat mods like code: They are not sandboxed and run with the same access to your machine as Claude Code. (Anthropic's Claude Code mods announcement)

What a Mod Can Change

Claude Code emits events as it works, and a mod can run before an event, after it, or instead of its default handling. Anthropic's examples include rewriting a prompt, blocking or retrying a tool call, approving or denying a permission request, and redacting secrets from tool output before Claude reads it. (Anthropic's Claude Code mods announcement)

Mods can also add or replace parts of the interface, including buttons, inputs, and custom panels. Anthropic says built-in features such as /diff now ship as mods, which means users can disable that mod or replace it with their own version. (Anthropic's Claude Code mods announcement)

Claude Code v2.1.287 added a built-in mod named You should know. A side agent watches for details that the user or Claude might miss. To enable it, run /plugin enable cc-plugin-you-should-know@builtin; Anthropic's release notes qualify the command for first-party sessions with telemetry on. (Claude Code v2.1.287 release notes)

Install and Share Mods Through Plugins

Anthropic says mods are available in the Claude Code CLI and desktop app. You can install a plugin that includes a mod from the Claude directory or by running /plugin in the CLI. To share a mod, package it in a plugin and submit that plugin to the directory. (Anthropic's Claude Code mods announcement)

Mods are on by default. In the terminal, use Claude Code v2.1.287 or later; the Desktop app includes its own copy of Claude Code, and mods work there from v2.1.286. A mod's hooks run in every kind of session that loads the plugin, but only the terminal and the Desktop app show what it draws: in the VS Code extension's chat panel and in claude -p, hooks run and nothing draws. (Claude Code docs, "Mods overview")

If you ask Claude to write a mod, it loads only in the session that made it. To keep it, copy its directory out of the session's mods folder, then load it with claude --plugin-dir or add it to a marketplace so others can install it. (Claude Code docs, "Create a mod") Our step-by-step guide to building a Claude Code mod walks through the files, hooks, state, and tests.

The official getting-started guide shows how to build a first mod as a plugin, add a hooks module in JavaScript or TypeScript, validate it, and test it in Claude Code; its example module is a .mjs file. It also explains how plugins can be installed from a marketplace. (Claude Code mods getting-started guide)

Review the Security Boundary

Mods run with the same access to your machine as Claude Code itself; Anthropic says they are not sandboxed. A mod can interact with events and tool calls in the session, so read its source and install only from publishers you trust. (Anthropic's Claude Code mods announcement)

Plugin controls still matter for managed teams. Anthropic says administrators can allow or block plugin marketplaces. On Team and Enterprise plans, and on any machine with managed settings, the built-in sec-default mod loads ahead of every mod a person installs and blocks certain risky actions; administrators who load their own mods first should keep sec-default in the list if they want those restrictions. (Anthropic's Claude Code mods announcement) (Claude Code docs, "Mods reference")

Why the Release Matters

Mods give developers a way to tailor Claude Code's behavior and interface to a project or team workflow, while keeping distribution inside the existing plugin model. Before installing a third-party mod, review both what it changes and the access it inherits from Claude Code. (Anthropic's Claude Code mods announcement)

Corrections and Updates

• October 9, 2026: This page said the getting-started guide adds a TypeScript module; the guide's hooks module is JavaScript or TypeScript, and its example is a .mjs file. The summary, lede and FAQ now say JavaScript or TypeScript too.
• October 9, 2026: Added the minimum Claude Code versions for mods, where mods draw, and that a mod written by Claude stays in its session until you copy it out.
• October 3, 2026: Added activation details for the built-in You should know mod.

Sources

• Anthropic, "Customize Claude Code with mods" (October 1, 2026)
• Claude, "Getting started with Claude Code mods" (October 1, 2026)
• Claude Code docs, "Mods overview", "Create a mod", and "Mods reference" (fetched October 9, 2026)
• Anthropic, "Claude Code v2.1.287 release notes" (October 1, 2026)