Is cc-hooks safe to install?

SaferSkills independently audited cc-hooks (Agent Skill) and scored it 100/100 (green). The audit ran 55 deterministic rules across Security, Supply Chain, Maintenance, Transparency, and Community; it found 0 high-severity and 0 lower-severity findings. The full rule-by-rule trace and per-finding evidence are below. Free, methodology-open.

CategoryWeightCategory scoreContribution

Securityprompt, exec, net, exfil, eval

35%

100

35.0 pts

Supply chainhash, typosquat, maintainer, lockfile

20%

100

20.0 pts

Maintenancestaleness, pinning, CI

15%

100

15.0 pts

TransparencySKILL.md, perms, README

15%

100

15.0 pts

Communityinstalls, verify, response

15%

100

15.0 pts

Findings & checks · 0 flagged

Securityscore 100 · 0 findings

✓—All security checks passedNo findings in this category for the latest scan.pass

Supply chainscore 100 · 0 findings

✓—All supply chain checks passedNo findings in this category for the latest scan.pass

Maintenancescore 100 · 0 findings

✓—All maintenance checks passedNo findings in this category for the latest scan.pass

Transparencyscore 100 · 0 findings

✓—All transparency checks passedNo findings in this category for the latest scan.pass

Communityscore 100 · 0 findings

✓—All community checks passedNo findings in this category for the latest scan.pass

The primary manifest — the file an agent reads to learn what this artifact does.

.agy-plugin/skills/cc-hooks/SKILL.md · 1 file

.agy-plugin/skills/cc-hooks/SKILL.md4.0 KB · Markdown

name: cc-hooks

user-invocable: false

skill_api_version: 1

hexagonal_role: supporting

metadata:

tier: execution

description: >-

Configure Claude Code hooks for PreToolUse, PostToolUse, Stop, Notification.

Use when blocking commands, auto-formatting, custom permissions, or writing hooks.

practices:

- pragmatic-programmer

Claude Code Hooks

Shell commands that fire at specific points in Claude Code's lifecycle.

Quick Start

Add to ~/.claude/settings.json (user) or .claude/settings.json (project):

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          { "type": "command", "command": "my-validator.sh" }
        ]
      }
    ]
  }
}

Hook Events

Event	When	Blocks?	Common Use
`PreToolUse`	Before tool runs	Yes	Block/modify commands
`PostToolUse`	After tool succeeds	Feedback	Auto-format, lint
`PermissionRequest`	Permission dialog	Yes	Auto-approve/deny
`UserPromptSubmit`	Prompt submitted	Yes	Add context, validate
`Stop`	Claude finishes	Yes	Force continue
`SessionStart`	Session begins	No	Load context, set env
`Notification`	Notifications	No	Desktop alerts

Full schemas: HOOK-EVENTS.md

Matchers

"Bash"              → exact match
"Edit|Write"        → regex OR
"mcp__.*__write"    → MCP tools
"*" or ""           → all tools

Tools: Bash, Read, Write, Edit, Glob, Grep, Task, WebFetch, WebSearch

Exit Codes

Code	Effect
0	Success - JSON parsed from stdout
2	Block - stderr fed to Claude
Other	Non-blocking error

Blocking a Tool

Simple (exit 2):

echo "Blocked: reason" >&2 && exit 2

JSON (exit 0):

{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"Blocked"}}

Decisions: "allow" (auto-approve), "deny" (block), "ask" (show dialog)

Modifying Input

{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"allow",
  "updatedInput":{"command":"modified-command"}}}

Real-World: DCG + RCH

{"hooks":{"PreToolUse":[{"matcher":"Bash","hooks":[
  {"type":"command","command":"dcg"},
  {"type":"command","command":"rch"}
]}]}}

DCG: Blocks git reset --hard, rm -rf, git push --force
RCH: Routes builds to remote workers

Details: DCG-RCH.md

Writing Your Own Hook

Minimal Python:

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

data = json.load(sys.stdin)
cmd = data.get('tool_input', {}).get('command', '')

if 'dangerous' in cmd:
    print("Blocked: dangerous", file=sys.stderr)
    sys.exit(2)

sys.exit(0)  # Allow

Hook input (stdin):

{"tool_name":"Bash","tool_input":{"command":"npm test"},"session_id":"...","cwd":"..."}

Environment Variables

Variable	Scope	Purpose
`CLAUDE_PROJECT_DIR`	All	Project root
`CLAUDE_ENV_FILE`	SessionStart/Setup	Persist env vars

Stop Hook (Force Continue)

{"decision":"block","reason":"Tests failing. Fix before stopping."}

Critical: Check stop_hook_active to prevent infinite loops.

Anti-Patterns

Don't	Do
Old object format	Array format with `matcher`
Unquoted `$VAR`	`"$VAR"`
Exit 2 with JSON	Exit 2 uses stderr only
Skip `stop_hook_active` check	Always check in Stop hooks

Debugging

claude --debug  # Hook execution details
/hooks          # View/edit in REPL

References

HOOK-EVENTS.md - All events with full schemas
DCG-RCH.md - Production examples (dcg, rch)
PATTERNS.md - Auto-format, logging, notifications
JSON-OUTPUT.md - Response schemas

cc-hooks— agent skill

Is cc-hooks safe to install?

Claude Code Hooks

Quick Start

Hook Events

Matchers

Exit Codes

Blocking a Tool

Modifying Input

Real-World: DCG + RCH

Writing Your Own Hook

Environment Variables

Stop Hook (Force Continue)

Anti-Patterns

Debugging

References

Audit the pieces. Scan the whole. Decide.