Code refactoring best practices based on Martin Fowler's catalog and Clean Code principles (formerly refactoring). This skill should be used when refactoring existing code, improving code structure, reducing complexity, eliminating code smells, or reviewing code for maintainability. Triggers on task

Fowler/Martin Code Refactoring Best Practices Comprehensive code refactoring guide based on Martin Fowler's catalog and Clean Code principles, designed for AI agents and LLMs. Contains 43 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation. When to Apply Reference these guidelines when: Refactoring existing code to improve maintainability Decomposing long methods or large classes Reducing coupling between components Simplifying complex conditional logic Reviewing code for code smells and anti patterns Rule Categories by Priority Priority Category Impact Prefix 1 Structure & Decomposition CRITICAL struct 2 Coupling & Dependencies CRITICAL couple 3 Naming & Clarity HIGH name 4 Conditional Logic HIGH cond 5 Abstraction & Patterns MEDIUM HIGH pattern 6 Data Organization MEDIUM data 7 Error Handling MEDIUM error 8 Micro Refactoring LOW micro Quick Reference 1. Structure & Decomposition (CRITICAL) struct extract method Extract Method for Long Functions struct single responsibility Apply Single Responsibility Principle struct extract class Extract Class from Large Class struct compose method Compose Method for Readable Flow struct function length Keep Functions Under 20 Lines struct replace method with object Replace Method with Method Object struct parameter object Introduce Parameter Object 2. Coupling & Dependencies (CRITICAL) couple dependency injection Use Dependency Injection couple hide delegate Hide Delegate to Reduce Coupling couple remove middle man Remove Middle Man When Excessive couple feature envy Fix Feature Envy by Moving Methods couple interface segregation Apply Interface Segregation Principle couple preserve whole object Preserve Whole Object Instead of Fields 3. Naming & Clarity (HIGH) name intention revealing Use Intention Revealing Names name avoid abbreviations Avoid Abbreviations and Acronyms name consistent vocabulary Use Consistent Vocabulary name searchable names Use Searchable Names name avoid encodings Avoid Type Encodings in Names 4. Conditional Logic (HIGH) cond guard clauses Replace Nested Conditionals with Guard Clauses cond polymorphism Replace Conditional with Polymorphism cond decompose Decompose Complex Conditionals cond consolidate Consolidate Duplicate Conditional Fragments cond special case Introduce Special Case Object cond lookup table Replace Conditional with Lookup Table 5. Abstraction & Patterns (MEDIUM HIGH) pattern strategy Extract Strategy for Algorithm Variants pattern template method Use Template Method for Shared Skeleton pattern factory Use Factory for Complex Object Creation pattern open closed Apply Open Closed Principle pattern composition over inheritance Prefer Composition Over Inheritance pattern extract superclass Extract Superclass for Common Behavior 6. Data Organization (MEDIUM) data encapsulate collection Encapsulate Collection data replace primitive Replace Primitive with Object data encapsulate record Encapsulate Record into Class data split variable Split Variable with Multiple Assignments data replace temp with query Replace Temp with Query 7. Error Handling (MEDIUM) error exceptions over codes Use Exceptions Instead of Error Codes error custom exceptions Create Domain Specific Exception Types error fail fast Fail Fast with Preconditions error separate concerns Separate Error Handling from Business Logic 8. Micro Refactoring (LOW) micro remove dead code Remove Dead Code micro inline variable Inline Trivial Variables micro simplify expressions Simplify Boolean Expressions micro rename for clarity Rename for Clarity How to Use Read individual reference files for detailed explanations and code examples: [Section definitions](references/ sections.md) Category structure and impact levels [Rule template](assets/templates/ template.md) Template for adding new rules Individual rules: references/{prefix} {slug}.md Full Compiled Document For the complete guide with all rules expanded: AGENTS.md