September 14, 2026
Claude Code Can Now Be Extended With Mods: A Tetris Mod Is Already Built
On 14 September 2026, Claude Mods began rolling out, and a Tetris mod has already been built for Claude. Each mod is a plugin with function hooks for extending Claude Code. The preview runs with `CLAUDE_CODE_ENABLE_FUNCTION_HOOKS=1 claude`.
Boris Cherny
@bcherny
Claude Mods are already starting to ship. Someone has already built a Tetris mod for Claude 🤯 See the latest community updates, technical details, and more great demos in the issue: https://github.com/anthropics/claude-code/issues/91870#issuecomment-5666255143
· 566.8K views
On 9 September 2026, Anthropic said it would release function hooks within a few weeks. By 14 September, Claude Mods had already begun rolling out, and a Tetris mod had been built for Claude.
### How mods work
Architecture. Anthropic calls a mod a plugin that uses function hooks. The term function hook will remain in the documentation. Each mod consists of `.claude-plugin/plugin.json`, `hooks/hooks.json`, and a TypeScript module. API types are generated with `/plugin-types`.
Function hooks support TypeScript functions, type definitions, and LSP support. They can modify component props and wrap render nodes. A hook for the `ui.press` event sees the same button press in the terminal and desktop app.
### What's already open
A working example. On 9 September, Anthropic open-sourced three built-in mods: `sec-default`, `diff`, and `telemetry`. The `diff` mod can be run from source with `claude --plugin-dir mods/diff`.
Within Claude Code, `diff` is launched with `/diff` in a Git repository containing a modified file. It shows a list of uncommitted files and hunks alongside the transcript. The panel updates after files are edited and shell commands are run.
The built-in mods API is early access and may change between releases without notice.
Source
