name: claude-code-hooks description: Create event-driven hooks for Claude Code automation. Configure PreToolUse, PostToolUse, Stop, and other hook events with bash scripts, environment variables, matchers, and exit codes.

Claude Code Hooks — Meta Reference

This skill provides the definitive reference for creating Claude Code hooks. Use this when building automation that triggers on Claude Code events.

When to Use This Skill

Building event-driven automation for Claude Code
Creating PreToolUse guards to block dangerous commands
Implementing PostToolUse formatters, linters, or auditors
Adding Stop hooks for testing or notifications
Setting up SessionStart/SessionEnd for environment management
Integrating Claude Code with CI/CD pipelines (headless mode)

Quick Reference

Event	Trigger	Use Case
`PreToolUse`	Before tool execution	Validate, block dangerous commands
`PostToolUse`	After tool execution	Format, audit, notify
`Stop`	When Claude finishes	Run tests, summarize
`Notification`	On notifications	Alert integrations
`SessionStart`	Session begins	Initialize environment
`SessionEnd`	Session ends	Cleanup, save state
`UserPromptSubmit`	User sends message	Preprocessing

Hook Structure

.claude/hooks/
├── pre-tool-validate.sh
├── post-tool-format.sh
├── post-tool-audit.sh
├── stop-run-tests.sh
└── session-start-init.sh

Configuration

settings.json

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/post-tool-format.sh"
          }
        ]
      }
    ],
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/pre-tool-validate.sh"
          }
        ]
      }
    ],
    "Stop": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/stop-run-tests.sh"
          }
        ]
      }
    ]
  }
}

Environment Variables

Variable	Description	Available In
`CLAUDE_PROJECT_DIR`	Project root path	All hooks
`CLAUDE_TOOL_NAME`	Current tool name	Pre/PostToolUse
`CLAUDE_TOOL_INPUT`	Tool input (JSON)	PreToolUse
`CLAUDE_TOOL_OUTPUT`	Tool output	PostToolUse
`CLAUDE_FILE_PATHS`	Affected files	PostToolUse
`CLAUDE_SESSION_ID`	Session identifier	All hooks

Exit Codes

Code	Meaning	Effect
`0`	Success	Continue execution
`1`	Error	Report error, continue
`2`	Block	Block tool execution (PreToolUse only)

Hook Templates

Pre-Tool Validation

#!/bin/bash
set -euo pipefail

# Block dangerous commands
if [[ "$CLAUDE_TOOL_NAME" == "Bash" ]]; then
  INPUT="$CLAUDE_TOOL_INPUT"

  # Block rm -rf /
  if echo "$INPUT" | grep -qE 'rm\s+-rf\s+/'; then
    echo "BLOCKED: Dangerous rm command detected"
    exit 2
  fi

  # Block force push to main
  if echo "$INPUT" | grep -qE 'git\s+push.*--force.*(main|master)'; then
    echo "BLOCKED: Force push to main/master not allowed"
    exit 2
  fi

  # Block credential exposure
  if echo "$INPUT" | grep -qE '(password|secret|api_key)\s*='; then
    echo "WARNING: Possible credential exposure"
  fi
fi

exit 0

Post-Tool Formatting

#!/bin/bash
set -euo pipefail

# Auto-format modified files
if [[ "$CLAUDE_TOOL_NAME" =~ ^(Edit|Write)$ ]]; then
  FILES="$CLAUDE_FILE_PATHS"

  for file in $FILES; do
    if [[ -f "$file" ]]; then
      case "$file" in
        *.js|*.ts|*.jsx|*.tsx|*.json|*.md)
          npx prettier --write "$file" 2>/dev/null || true
          ;;
        *.py)
          ruff format "$file" 2>/dev/null || true
          ;;
        *.go)
          gofmt -w "$file" 2>/dev/null || true
          ;;
        *.rs)
          rustfmt "$file" 2>/dev/null || true
          ;;
      esac
    fi
  done
fi

exit 0

Post-Tool Security Audit

#!/bin/bash
set -euo pipefail

# Audit file changes for security issues
if [[ "$CLAUDE_TOOL_NAME" =~ ^(Edit|Write)$ ]]; then
  FILES="$CLAUDE_FILE_PATHS"

  for file in $FILES; do
    if [[ -f "$file" ]]; then
      # Check for hardcoded secrets
      if grep -qE '(password|secret|api_key|token)\s*[:=]\s*["\x27][^"\x27]+["\x27]' "$file"; then
        echo "WARNING: Possible hardcoded secret in $file"
      fi

      # Check for console.log in production code
      if [[ "$file" =~ \.(ts|js|tsx|jsx)$ ]] && grep -q 'console.log' "$file"; then
        echo "NOTE: console.log found in $file"
      fi
    fi
  done
fi

exit 0

Stop Hook (Run Tests)

#!/bin/bash
set -euo pipefail

# Run tests after Claude finishes
cd "$CLAUDE_PROJECT_DIR"

# Detect test framework
if [[ -f "package.json" ]]; then
  if grep -q '"vitest"' package.json; then
    npm run test 2>&1 | head -50
  elif grep -q '"jest"' package.json; then
    npm test 2>&1 | head -50
  fi
elif [[ -f "pytest.ini" ]] || [[ -f "pyproject.toml" ]]; then
  pytest --tb=short 2>&1 | head -50
fi

exit 0

Session Start

#!/bin/bash
set -euo pipefail

cd "$CLAUDE_PROJECT_DIR"

# Check git status
echo "=== Git Status ==="
git status --short

# Check for uncommitted changes
if ! git diff --quiet; then
  echo "WARNING: Uncommitted changes detected"
fi

# Verify dependencies
if [[ -f "package.json" ]]; then
  if [[ ! -d "node_modules" ]]; then
    echo "NOTE: node_modules missing, run npm install"
  fi
fi

exit 0

Matchers

Matchers filter which tool triggers the hook:

Matcher	Matches
`""` (empty)	All tools
`"Bash"`	Bash tool only
`"Edit\|Write"`	Edit OR Write
`"Edit.*"`	Edit and variants (regex)

Security Best Practices

HOOK SECURITY CHECKLIST

[ ] Validate all inputs with regex
[ ] Quote all variables: "$VAR" not $VAR
[ ] Use absolute paths
[ ] No eval with untrusted input
[ ] Set -euo pipefail at top
[ ] Keep hooks fast (<1 second)
[ ] Log actions for audit
[ ] Test manually before deploying

Hook Composition

Multiple Hooks on Same Event

{
  "PostToolUse": [
    {
      "matcher": "Edit|Write",
      "hooks": [
        { "type": "command", "command": ".claude/hooks/format.sh" },
        { "type": "command", "command": ".claude/hooks/audit.sh" },
        { "type": "command", "command": ".claude/hooks/notify.sh" }
      ]
    }
  ]
}

Hooks execute in order. If one fails, subsequent hooks may not run.

Debugging Hooks

# Test hook manually
CLAUDE_TOOL_NAME="Edit" \
CLAUDE_FILE_PATHS="src/app.ts" \
CLAUDE_PROJECT_DIR="$(pwd)" \
bash .claude/hooks/post-tool-format.sh

# Check exit code
echo $?

claude-code-hooks

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