writing-rules

Original：🇺🇸 English
Translated

Create markdown-based behavioral rules preventing unwanted actions. create hookify rule, behavioral rule, prevent behavior, block command Use when: preventing dangerous commands, blocking debug commits, enforcing conventions DO NOT use when: hook scope (abstract:hook-scope-guide), SDK hooks (abstract:hook-authoring), evaluating hooks (abstract:hooks-eval).

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Sourceathola/claude-night-market
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NPX Install

npx skill4agent add athola/claude-night-market writing-rules

Tags

Translated version includes tags in frontmatter
hookify-rulescommand-blockingcode-qualityregex-patternsbehavioral-guidelines

SKILL.md Content

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Table of Contents

Hookify Rule Writing Guide

When To Use

  • Creating behavioral rules to prevent unwanted actions
  • Defining persistent guardrails for Claude Code sessions

When NOT To Use

  • Complex multi-step workflows - use agents instead
  • One-time operations that do not need persistent behavioral rules

Overview

Hookify rules are markdown files with YAML frontmatter that define patterns to watch for and messages to show when those patterns match. Rules are stored in 
.claude/hookify.{rule-name}.local.md
files.

Quick Start

Create 
.claude/hookify.dangerous-rm.local.md
:
yaml
---
name: dangerous-rm
enabled: true
event: bash
pattern: rm\s+-rf
action: block
---

🛑 **Dangerous rm command detected!**

This command could delete important files.
Verification: Run the command with 
--help
flag to verify availability.
The rule activates immediately - no restart needed!

Rule File Format

Frontmatter Fields

name (required): Unique identifier (kebab-case) enabled (required): 
true
or 
false
event (required): 
bash
, 
file
, 
stop
, 
prompt
, or 
all
action (optional): 
warn
(default) or 
block
pattern (simple): Regex pattern to match

Event Types

  • bash: Bash tool commands
  • file: Edit, Write, MultiEdit tools
  • stop: When agent wants to stop
  • prompt: User prompt submission
  • all: All events

Advanced Conditions

For multiple field checks:
yaml
---
name: warn-env-edits
enabled: true
event: file
action: warn
conditions:
  - field: file_path
    operator: regex_match
    pattern: \.env$
  - field: new_text
    operator: contains
    pattern: API_KEY
---

🔐 **API key in .env file!**
Ensure file is in .gitignore.

Operators

  • regex_match
    : Pattern matching
  • contains
    : Substring check
  • equals
    : Exact match
  • not_contains
    : Must NOT contain
  • starts_with
    : Prefix check
  • ends_with
    : Suffix check

Field Reference

bash events: 
command
file events: 
file_path
, 
new_text
, 
old_text
, 
content
prompt events: 
user_prompt
stop events: 
transcript

Pattern Writing

Regex Basics

  • \s
    - whitespace
  • \d
    - digit
  • \w
    - word character
  • .
    - any character (use 
    \.
    for literal dot)
  • +
    - one or more
  • *
    - zero or more
  • |
    - OR

Examples

rm\s+-rf          → rm -rf
console\.log\(    → console.log(
chmod\s+777       → chmod 777

Test Patterns

bash
python3 -c "import re; print(re.search(r'pattern', 'text'))"

Example Rules

Block Destructive Commands

yaml
---
name: block-destructive
enabled: true
event: bash
pattern: rm\s+-rf|dd\s+if=|mkfs
action: block
---

🛑 **Destructive operation blocked!**
Can cause data loss.

Warn About Debug Code

yaml
---
name: warn-debug
enabled: true
event: file
pattern: console\.log\(|debugger;
action: warn
---

🐛 **Debug code detected!**
Remove before committing.

Require Tests

yaml
---
name: require-tests
enabled: true
event: stop
action: warn
conditions:
  - field: transcript
    operator: not_contains
    pattern: pytest|npm test
---

⚠️ **Tests not run!**
Please verify changes.

Protect Production Files

yaml
---
name: protect-prod
enabled: true
event: file
action: block
conditions:
  - field: file_path
    operator: regex_match
    pattern: /production/|\.prod\.
---

🚨 **Production file!**
Requires review.

Management

Enable/Disable: Edit 
.local.md
file: 
enabled: false
Delete:
bash
rm .claude/hookify.my-rule.local.md
List:
bash
/hookify:list

Related Skills

  • abstract:hook-scope-guide - Hook placement decisions
  • abstract:hook-authoring - SDK hook development
  • abstract:hooks-eval - Hook evaluation

Best Practices

  1. Start with simple patterns
  2. Test regex thoroughly
  3. Use clear, helpful messages
  4. Prefer warnings over blocks initially
  5. Name rules descriptively
  6. Document intent in messages

Troubleshooting

Common Issues

If a rule doesn't trigger, verify that the 
event
type matches the tool being used (e.g., use 
bash
for command line tools). Check that the regex 
pattern
is valid and matches the target text by testing it with a short Python script. If you encounter permission errors when creating rule files in 
.claude/
, ensure that the directory is writable by your user.