/file-watcher

---
name: file-watcher
description: Configure file watching hooks to auto-react to config changes, env file updates, and dependency modifications. Use to set up reactive workflows.
user-invocable: true
---

# File Watcher

Use Claude Code's `FileChanged` and `CwdChanged` hooks to create reactive workflows that respond to file system changes.

## Trigger

Use when:
- Setting up auto-reload for config changes
- Watching for dependency updates
- Monitoring build output
- Creating reactive development workflows

## How File Watching Works

Claude Code's `SessionStart` and `CwdChanged` hooks support returning `watchPaths` to register file watchers. The current `cwd-changed.js` script focuses on env injection; to add watch registration, your hook script must output this JSON structure:

```json
{
  "hookSpecificOutput": {
    "hookEventName": "SessionStart",
    "watchPaths": [
      "/absolute/path/to/.env",
      "/absolute/path/to/package.json"
    ]
  }
}
```

When watched files change, the `FileChanged` hook fires with:
```json
{
  "hook_event_name": "FileChanged",