/hook-template

name: hook-template
description: Generate hook script from template. Use when adding a new hook, wiring a PreToolUse/PostToolUse/Stop/Notification hook, or scaffolding hook config for settings.json.
user-invocable: true

Hook Template Generator

Generate a hook script and configuration based on requirements.

**Usage**: `/hook-template [hook-event] [purpose]`

---

Hook Events

Claude Code defines **30 hook events**. The common ones, grouped:

| Group | Events | |-------|--------| | Lifecycle | `SessionStart`, `SessionEnd`, `Setup` | | Prompt | `UserPromptSubmit`, `UserPromptExpansion` | | Tool | `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PostToolBatch` | | Permission | `PermissionRequest`, `PermissionDenied` | | Subagent | `SubagentStart`, `SubagentStop` | | Stop | `Stop`, `StopFailure` | | Task | `TaskCreated`, `TaskCompleted` | | Compaction | `PreCompact`, `PostCompact` | | Notification | `Notification`, `MessageDisplay` | | MCP elicitation | `Elicitation`, `ElicitationResult` | | Environment | `ConfigChange`, `CwdChanged`, `FileChanged`, `InstructionsLoaded`, `WorktreeCreate`, `WorktreeRemove`, `TeammateIdle` |

That is all 30 events. See the official Claude Code hooks docs for the full list and each event's payload. The templates below cover the practical 90%.

---

Hook Config Fields

| Field | Type | Required | Default | Notes | |-------|------|----------|---------|-------| | `type` | String | No | `command` | `command`, `prompt`, `http`, `mcp_tool`, or `agent` | | `command` | String | If type=command | - | Shell command to execute | | `prompt` | String | If type=prompt | - | Natural language prompt evaluated by an LLM | | `matcher` | String | No | - | For tool events: tool name, regex, or `*` | | `timeout` | Integer | No | 60 | Seconds, per hook | | `once` | Boolean | No | false | Run hook only once per session | | `if` | String | No | - | Conditional guard for the hook | | `statusMessage` | String | No | - | Message shown while the hook runs |

`type: command` (default) and `type: prompt` (LLM-evaluated) cover most needs. The `http`, `mcp_tool`, and `agent` entry types also exist for calling an endpoint, invoking an MCP tool, or dispatching a subagent.

---

Hook Input (stdin JSON)

All hooks receive JSON on stdin. The event name is in `hook_event_name`:

{
  "session_id": "abc123",
  "transcript_path": "/path/to/transcript.txt",
  "cwd": "/current/working/dir",
  "permission_mode": "ask",
  "hook_event_name": "PreToolUse",
  "tool_name": "Write",
  "tool_input": { "file_path": "/path/to/file" }
}

Decision output cheatsheet

• **PreToolUse**: return `hookSpecificOutput.permissionDecision` of `allow`,

`deny`, or `ask`. Exit code 2 with a stderr message is the shorthand for `deny`. The legacy top-level `{"decision": "approve" | "block"}` is still accepted.

• **Stop / SubagentStop**: to continue the loop, return

`{"decision": "block", "reason": "<next prompt>"}` — the key is `reason`.

• Silent success is exit `0` with no output.

---

Process

1. **Gather Requirements**

• Hook event
• Purpose
• Matcher (for tool events: tool name, regex, or `*`)

2. **Generate Script** at `.claude/hooks/[name].sh`

3. **Update settings.json** with hook config

4. **Make Executable**: `chmod +x`

5. **Validate** with `/hooks-check`

---

Templates

PreToolUse (Blocker, exit-code shorthand)

#!/bin/bash
INPUT=$(cat)
TOOL=$(echo "$INPUT" | jq -r '.tool_name')
FILE=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')

# Block edits to specific files
if [[ "$FILE" == *"package-lock.json"* ]]; then
    echo "BLOCKED: Do not edit lockfiles directly" >&2
    exit 2   # exit 2 = deny for PreToolUse
fi
exit 0  # Allow (no output needed)

PreToolUse (Deny via JSON permissionDecision)

#!/bin/bash
INPUT=$(cat)
FILE=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')

if [[ "$FILE" == *"package-lock.json"* ]]; then
    jq -n '{
      "hookSpecificOutput": {
        "hookEventName": "PreToolUse",
        "permissionDecision": "deny",
        "permissionDecisionReason": "Do not edit lockfiles directly"
      }
    }'
    exit 0
fi
# permissionDecision may be "allow", "deny", or "ask"
exit 0

PreToolUse (Context Adding)

#!/bin/bash
cat > /dev/null  # Consume stdin
INFO="This file requires careful review"
jq -n --arg ctx "$INFO" '{
    "hookSpecificOutput": {
        "hookEventName": "PreToolUse",
        "additionalContext": $ctx
    }
}'
exit 0

PostToolUse (Logger)

#!/bin/bash
INPUT=$(cat)
# Process and log... (no stdout needed)
exit 0

Stop (Auto-Loop)

#!/bin/bash
CHECKPOINT=".auto-loop/checkpoint.json"
if [[ ! -f "$CHECKPOINT" ]]; then
    exit 0  # Allow stop
fi
# Block stop to continue loop — key is "reason", used as the next prompt
jq -n --arg reason "Continuing iteration" \
    '{"decision": "block", "reason": $reason}'
exit 0

SessionStart (Context Load)

#!/bin/bash
cat > /dev/null
echo "Loading project context..." >&2
exit 0

Prompt Hook (LLM-based)

Instead of a bash script, use `type: "prompt"` in settings.json:

{
  "hooks": {
    "Stop": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "prompt",
            "prompt": "Review the work done. Return 'approve' if complete, or 'block' with reason.",
            "timeout": 30
          }
        ]
      }
    ]
  }
}

---

Settings.json Format

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/validate.sh",
            "timeout": 60
          }
        ]
      }
    ],
    "SessionStart": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/load-context.sh",
            "once": true