> ## Documentation Index
> Fetch the complete documentation index at: https://exosphere-auto-translate-docs-20260624-1149.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Hook handler (internal)

> The subprocess Claude Code calls on each tool event

```bash theme={null}
failproofai --hook <EventType>
```

This is the command registered in Claude Code's `settings.json` by `failproofai policies --install`. You don't normally call this directly.

Reads a JSON payload from stdin, evaluates all enabled policies, and exits with a code indicating the decision:

| Exit code | Decision   | Effect                                           |
| --------- | ---------- | ------------------------------------------------ |
| `0`       | `allow`    | Permit the action                                |
| `1`       | `deny`     | Block the action - Claude sees the denial reason |
| `2`       | `instruct` | Inject guidance into Claude's context            |

### Supported event types

| Category              | Events                                                                                     |
| --------------------- | ------------------------------------------------------------------------------------------ |
| **Tool execution**    | `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest`, `PermissionDenied` |
| **Session lifecycle** | `SessionStart`, `SessionEnd`, `Stop`, `StopFailure`                                        |
| **User interaction**  | `UserPromptSubmit`, `Notification`, `Elicitation`, `ElicitationResult`                     |
| **Subagents & tasks** | `SubagentStart`, `SubagentStop`, `TaskCreated`, `TaskCompleted`, `TeammateIdle`            |
| **Configuration**     | `InstructionsLoaded`, `ConfigChange`, `CwdChanged`                                         |
| **File system**       | `FileChanged`, `WorktreeCreate`, `WorktreeRemove`                                          |
| **Context**           | `PreCompact`, `PostCompact`                                                                |