Skill Metadata

Field	Value
Version	1.0.0
Tier	Ops
Auto-load	When configuring hook system

What It Does

Hook system 설정 및 관리를 위한 전체 가이드를 제공합니다. PreToolUse, PostToolUse, SessionStart 등 다양한 hook type의 설계와 구현 방법을 다룹니다.

When to Use

• Safety check나 validation hook을 추가할 때
• Auto-formatting이나 linting을 자동화할 때
• Session lifecycle event에 응답하는 로직을 작성할 때
• 개발 이벤트 기반 workflow를 트리거할 때

Configuring Claude Code Hooks System

Hooks are lightweight (<100ms) automated scripts triggered by Claude Code lifecycle events. They enforce guardrails, run quality checks, and seed context without blocking user workflow.

Hook Types & Events

Hook Type	Trigger Event	Execution Time	Use Cases
PreToolUse	Before tool execution (Read, Edit, Bash, etc.)	<100ms	Command validation, permission checks, safety gates
PostToolUse	After tool execution succeeds	<100ms	Auto-formatting, linting, permission restoration
SessionStart	Session initialization	<500ms	Project summary, context seeding, status card
Notification	User notification event	N/A	macOS notifications, alerts, wait status
Stop	Session termination	N/A	Cleanup, final checks, task summary

Hook Configuration in settings.json

High-Freedom Approach: Events-Driven Hooks

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "node ~/.claude/hooks/pre-bash-validator.js"
          }
        ]
      },
      {
        "matcher": "Edit|Write",
        "hooks": [
          {
            "type": "command",
            "command": "bash ~/.claude/hooks/pre-edit-guard.sh"
          }
        ]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "Edit",
        "hooks": [
          {
            "type": "command",
            "command": "bash ~/.claude/hooks/post-edit-lint.sh"
          }
        ]
      }
    ],
    "SessionStart": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "node ~/.claude/hooks/session-status-card.js"
          }
        ]
      }
    ]
  }
}

Medium-Freedom: Hook Patterns

Pattern 1: Pre-Command Validation

#!/bin/bash
# pre-bash-validator.sh: Block dangerous patterns

FORBIDDEN_PATTERNS=(
  "rm -rf /"
  "sudo rm"
  "chmod 777 /"
  "eval \$(curl"
)

COMMAND="$1"
for pattern in "${FORBIDDEN_PATTERNS[@]}"; do
  if [[ "$COMMAND" =~ $pattern ]]; then
    echo "🔴 Blocked: $pattern detected" >&2
    exit 2  # Block execution
  fi
done

exit 0  # Allow execution

Pattern 2: Post-Edit Auto-Formatting

#!/bin/bash
# post-edit-format.sh: Auto-format after edits

FILE="$1"
EXT="${FILE##*.}"

case "$EXT" in
  js|ts)
    npx prettier --write "$FILE" 2>/dev/null
    ;;
  py)
    python3 -m black "$FILE" 2>/dev/null
    ;;
  go)
    gofmt -w "$FILE" 2>/dev/null
    ;;
esac

exit 0

Pattern 3: SessionStart Status Card

#!/bin/bash
# session-status-card.sh: Show project status

echo "🚀 Claude Code Session Started"
echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"

if [ -f ".moai/config.json" ]; then
  PROJECT=$(jq -r '.name' .moai/config.json 2>/dev/null || echo "Unknown")
  echo "📦 Project: $PROJECT"
  echo "🏗️  Framework: $(jq -r '.tech_stack' .moai/config.json 2>/dev/null || echo "Auto-detect")"
fi

echo "📋 Recent SPECS:"
ls .moai/specs/ 2>/dev/null | head -3 | sed 's/^/  ✓ /'

echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"

Low-Freedom: Security-Focused Hook Scripts

Permission Preservation Hook

#!/bin/bash
set -euo pipefail
# preserve-permissions.sh: Save/restore file permissions

HOOK_TYPE="${1:-pre}"  # 'pre' or 'post'
FILE="${2:-.}"

PERMS_FILE="/tmp/perms_${FILE//\//_}.txt"

if [[ "$HOOK_TYPE" == "pre" ]]; then
  stat -c "%a %u:%g" "$FILE" > "$PERMS_FILE" 2>/dev/null || true
  exit 0
elif [[ "$HOOK_TYPE" == "post" ]]; then
  if [[ -f "$PERMS_FILE" ]]; then
    SAVED_PERMS=$(cat "$PERMS_FILE")
    chmod ${SAVED_PERMS%% *} "$FILE" 2>/dev/null || true
    rm "$PERMS_FILE"
  fi
  exit 0
fi

Dangerous Command Blocker

#!/usr/bin/env python3
import json
import sys
import re

BLOCKED_PATTERNS = [
    (r"rm\s+-rf\s+/", "Blocking rm -rf /"),
    (r"sudo\s+rm", "Blocking sudo rm without confirmation"),
    (r">\s*/etc/\w+", "Blocking writes to system files"),
    (r"curl.*\|\s*bash", "Blocking curl | bash (code injection risk)"),
]

try:
    data = json.load(sys.stdin)
    command = data.get("tool_input", {}).get("command", "")

    for pattern, msg in BLOCKED_PATTERNS:
        if re.search(pattern, command):
            print(f"🔴 BLOCKED: {msg}", file=sys.stderr)
            sys.exit(2)  # Block

    sys.exit(0)  # Allow
except Exception as e:
    print(f"Hook error: {e}", file=sys.stderr)
    sys.exit(0)  # Allow on error (fail open)

Hook Exit Codes

Code	Meaning	Behavior
0	Success	Tool proceeds normally
1	Warning + Stderr	Warning logged, tool proceeds
2	Blocked + Error	Tool execution blocked

Best Practices

✅ DO:

• Keep hook scripts < 100ms execution time
• Use specific matchers (not wildcard * unless necessary)
• Log errors clearly to stderr
• Test hooks before deploying to team

❌ DON'T:

• Make network calls in PreToolUse hooks
• Block common operations (use warnings instead)
• Write to user files from hooks
• Create complex logic (delegate to sub-agents)

Hook Validation Checklist

• All scripts have proper shebang (#!/bin/bash or #!/usr/bin/env python3)
• Scripts are executable: chmod +x hook.sh
• Exit codes are correct (0, 1, or 2)
• Paths are absolute (not relative)
• Tested for < 100ms latency
• Error messages are user-friendly
• No hardcoded secrets or credentials

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Reference: Context7 Claude Code Hooks documentation Version: 1.0.0