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5 Hooks Every Claude Code User Should Install Today

April 21, 2026 · 8 min read · by yurukusa

Claude Code hooks are shell scripts that run before (or after) every tool call. They can inspect the command about to execute and block it if it matches a dangerous pattern. The hook receives JSON on stdin and returns a decision on stdout.

These 5 hooks cover the incidents we see most often in anthropics/claude-code Issues. They're ordered from "prevents data loss" to "saves money."

#!/bin/bash
# prevent-rm-rf.sh
# Trigger: PreToolUse  Matcher: Bash

INPUT=$(cat)
CMD=$(echo "$INPUT" | jq -r '.tool_input.command // empty')
[ -z "$CMD" ] && exit 0

# Block rm -rf targeting protected paths
if echo "$CMD" | grep -qE 'rm\s+(-[a-zA-Z]*[rR][a-zA-Z]*\s+)*(\/|~|\$HOME|\.git|\.ssh|\.env|\.gnupg|node_modules\/\.\.)'; then
  echo '{"decision":"DENY","reason":"Blocked: rm -rf targeting protected path. Use specific file paths instead."}'
  exit 0
fi

# Block rm -rf with wildcard at root-like paths
if echo "$CMD" | grep -qE 'rm\s+(-[a-zA-Z]*[rR][a-zA-Z]*\s+)\.\./'; then
  echo '{"decision":"DENY","reason":"Blocked: rm -rf with parent directory traversal."}'
  exit 0
fi

#!/bin/bash
# prevent-force-push.sh
# Trigger: PreToolUse  Matcher: Bash

INPUT=$(cat)
CMD=$(echo "$INPUT" | jq -r '.tool_input.command // empty')
[ -z "$CMD" ] && exit 0

# Block force-push to main/master
if echo "$CMD" | grep -qE 'git\s+push\s+.*--force.*\s+(origin\s+)?(main|master)'; then
  echo '{"decision":"DENY","reason":"Blocked: force-push to main/master. Use a feature branch or --force-with-lease."}'
  exit 0
fi

# Also catch the short form
if echo "$CMD" | grep -qE 'git\s+push\s+-f\s+.*\s*(main|master)'; then
  echo '{"decision":"DENY","reason":"Blocked: force-push (-f) to main/master."}'
  exit 0
fi

#!/bin/bash
# prevent-secret-leak.sh
# Trigger: PreToolUse  Matcher: Write|Edit

INPUT=$(cat)
CONTENT=$(echo "$INPUT" | jq -r '
  .tool_input.content //
  .tool_input.new_string //
  empty')
[ -z "$CONTENT" ] && exit 0

# Check for common secret patterns
if echo "$CONTENT" | grep -qE '(sk-[a-zA-Z0-9]{20,}|AKIA[0-9A-Z]{16}|ghp_[a-zA-Z0-9]{36}|glpat-[a-zA-Z0-9\-]{20,}|xox[bpsa]-[a-zA-Z0-9\-]+)'; then
  echo '{"decision":"DENY","reason":"Blocked: detected what looks like an API key or token. Use environment variables instead."}'
  exit 0
fi

# Check for private key headers
if echo "$CONTENT" | grep -qE '-----BEGIN (RSA |EC |OPENSSH )?PRIVATE KEY-----'; then
  echo '{"decision":"DENY","reason":"Blocked: private key detected. Never write private keys into source files."}'
  exit 0
fi

# Check for .env-style secrets being written to non-.env files
FILE=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')
if [[ "$FILE" != *.env* ]] && echo "$CONTENT" | grep -qE '^[A-Z_]+=(sk-|AKIA|ghp_|password|secret)'; then
  echo '{"decision":"DENY","reason":"Blocked: secret-like values being written outside .env file."}'
  exit 0
fi

#!/bin/bash
# compact-circuit-breaker.sh
# Trigger: PreCompact  (no matcher needed)

MAX_PER_HOUR="${CC_COMPACT_MAX_PER_HOUR:-3}"
MIN_INTERVAL="${CC_COMPACT_MIN_INTERVAL:-120}"
STATE_DIR="/tmp/.cc-compact-breaker"
STATE_FILE="$STATE_DIR/log"

mkdir -p "$STATE_DIR"
touch "$STATE_FILE"

NOW=$(date +%s)
ONE_HOUR_AGO=$((NOW - 3600))

# Clean entries older than 1 hour
awk -v cutoff="$ONE_HOUR_AGO" '$1 >= cutoff' "$STATE_FILE" > "$STATE_FILE.tmp"
mv "$STATE_FILE.tmp" "$STATE_FILE"

RECENT=$(wc -l < "$STATE_FILE" | tr -d ' ')

# Check last compaction time
LAST=0
[ -s "$STATE_FILE" ] && LAST=$(tail -1 "$STATE_FILE")
ELAPSED=$((NOW - LAST))

if [ "$RECENT" -ge "$MAX_PER_HOUR" ]; then
  echo "CIRCUIT BREAKER: $RECENT compactions in the last hour (max $MAX_PER_HOUR). Start a new session." >&2
  exit 2
fi

if [ "$ELAPSED" -lt "$MIN_INTERVAL" ] && [ "$LAST" -gt 0 ]; then
  echo "COOLDOWN: Last compaction was ${ELAPSED}s ago (min ${MIN_INTERVAL}s)." >&2
  exit 2
fi

echo "$NOW" >> "$STATE_FILE"
exit 0

#!/bin/bash
# read-once-guard.sh
# Trigger: PreToolUse  Matcher: Read

INPUT=$(cat)
FILE_PATH=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')
[ -z "$FILE_PATH" ] && exit 0

FILE_PATH=$(realpath "$FILE_PATH" 2>/dev/null || echo "$FILE_PATH")

STATE_DIR="/tmp/cc-read-once"
mkdir -p "$STATE_DIR"
STATE_FILE="$STATE_DIR/reads-$PPID.log"
MAX_READS="${CC_READ_ONCE_MAX:-3}"

# Get current file modification time
MTIME=$(stat -c %Y "$FILE_PATH" 2>/dev/null || echo "0")

# Look up previous reads
COUNT=0
PREV_MTIME="0"
if [ -f "$STATE_FILE" ]; then
  while IFS=$'\t' read -r path mtime count; do
    [ "$path" = "$FILE_PATH" ] && COUNT=$count && PREV_MTIME=$mtime && break
  done < "$STATE_FILE"
fi

# Reset if file was modified
[ "$MTIME" != "$PREV_MTIME" ] && [ "$PREV_MTIME" != "0" ] && COUNT=0

COUNT=$((COUNT + 1))

# Update state
grep -v "^${FILE_PATH}	" "$STATE_FILE" 2>/dev/null > "$STATE_FILE.tmp" || true
printf '%s\t%s\t%s\n' "$FILE_PATH" "$MTIME" "$COUNT" >> "$STATE_FILE.tmp"
mv "$STATE_FILE.tmp" "$STATE_FILE"

if [ "$COUNT" -gt "$MAX_READS" ]; then
  echo "Token waste: ${FILE_PATH} read ${COUNT} times without changes. Content is already in context." >&2
fi

exit 0

Install All 5 in One Command

npx cc-safe-setup

After installing, you can verify hooks are active:

cat ~/.claude/settings.json | jq '.hooks'

How Hooks Work (30-Second Primer)

Claude Code fires events at specific points during operation. A hook is a shell script registered to an event. The two most useful events:

• PreToolUse — fires before every tool call (Bash, Read, Write, Edit). You can inspect the command and return {"decision":"DENY","reason":"..."} to block it.
• PreCompact — fires before auto-compaction. Exit code 2 blocks the compaction.

Hooks go in ~/.claude/settings.json under the "hooks" key. Each hook specifies its trigger event, an optional matcher (which tool to intercept), and the command to run.

Going Further

These 5 hooks handle the most common problems. For deeper coverage:

• Token Checkup — analyze your settings.json for token waste patterns and get specific hook recommendations.
• Token Optimization Book — 8-chapter guide to understanding and reducing Claude Code token consumption.
• Hook Selector — browse 706 hook examples by category.