Claude Code launches Mods: developers can reshape its interface and tool calls from the inside with JavaScript/TypeScript, but mods are not sandboxed
Anthropic has launched Mods for Claude Code, a plugin mechanism that runs directly inside the tool: developers can hook JavaScript or TypeScript functions into events such as tool calls, user prompts and interface rendering to add custom panels, intercept tool calls or add new commands. Mods run with the user’s own permissions and are not sandboxed, and Anthropic warns users to install them only from trusted sources.
According to the Claude Code docs, a mod can do things settings hooks, skills and MCP servers cannot: draw panes with tabs, buttons and text fields beside the transcript, redraw parts of Claude Code’s own interface, step into a tool call or request midway (for example asking the user first, answering without running the tool, or sending a request to a different model), and add commands that run immediately without a Claude turn. Some built-in features such as /diff are themselves mods.
Mods install as plugins from a marketplace and work in the Claude Code CLI and the Code tab of the Claude Desktop app, and only partly in other environments such as the VS Code extension; they require Claude Code v2.1.287 or later and are on by default. Anthropic shares sample mods in its claude-code-playground repository on GitHub, as-is and without support.
On permissions, the docs say a mod runs inside Claude Code with the user’s permissions: it can read and write any file the user account can, start programs and make network requests, read API keys in environment variables and settings files, see and rewrite every prompt and tool call, approve tool calls without asking, and call models on the user’s plan or API key. Turning on sandboxing only isolates the Bash commands Claude runs, not processes a mod starts; a mod cannot alter the permission prompt. Organization administrators can limit which mods load through managed settings.
According to The Decoder, the first official Mod plugin, “You Should Know,” spins up a separate agent that watches Claude’s output and sends a heads-up when it spots important information users might have missed; it can be turned on with /plugin enable cc-plugin-you-should-know@builtin.
Sources
- Claude Code's new Mods system lets developers rewrite the AI coding tool from the inside — The Decoder
- Mods overview — code.claude.com