Paths: File paths ( shared/ , references/ , ../ln-* ) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root. Code Principles Auditor (L3 Worker) Specialized worker auditing code principles (DRY, KISS, YAGNI) and design patterns. Purpose & Scope Worker in ln-620 coordinator pipeline - invoked by ln-620-codebase-auditor Audit code principles (DRY/KISS/YAGNI, error handling, DI) Return structured findings with severity, location, effort, pattern_signature, recommendations Calculate compliance score (X/10) for Code Principles category Inputs (from Coordinator) MANDATORY READ: Load shared/references/audit_worker_core_contract.md . Receives contextStore with: tech_stack , best_practices , principles , codebase_root , output_dir . Domain-aware: Supports domain_mode + current_domain (see audit_output_schema.md#domain-aware-worker-output ). Workflow MANDATORY READ: Load shared/references/two_layer_detection.md for detection methodology. Parse context — extract fields, determine scan_path (domain-aware if specified), extract output_dir Load detection patterns MANDATORY READ: Load references/detection_patterns.md for language-specific Grep/Glob patterns Select patterns matching project's tech_stack Scan codebase for violations (Layer 1) All Grep/Glob patterns use scan_path (not codebase_root) Follow step-by-step detection from detection_patterns.md Apply exclusions from detection_patterns.md#exclusions Analyze context per candidate (Layer 2) DRY: read both code blocks to confirm true duplication (not just similar naming or shared interface) KISS: check if abstraction serves DI pattern (valid single-impl interface) or is premature YAGNI: check if feature flag was recently added (intentional) or dormant for months Generate recommendations MANDATORY READ: Load references/refactoring_decision_tree.md for pattern selection Match each finding to appropriate refactoring pattern via decision tree Collect findings with severity, location, effort, pattern_id, pattern_signature, recommendation Tag each finding with domain: domain_name (if domain-aware) Assign pattern_signature for cross-domain matching by ln-620 Calculate score using penalty algorithm Write Report: Build full markdown report in memory per shared/templates/audit_worker_report_template.md , write to {output_dir}/623-principles-{domain}.md (or 623-principles.md in global mode) in single Write call. Include
JSON block
with pattern_signature fields for cross-domain DRY analysis
Return Summary:
Return minimal summary to coordinator (see Output Format)
Two-Layer Detection (MANDATORY)
MANDATORY READ:
shared/references/two_layer_detection.md
All findings require Layer 2 context analysis. Layer 1 finding without Layer 2 = NOT a valid finding. Before reporting, ask: "Is this violation intentional or justified by design?"
Finding Type
Layer 2 Downgrade Examples
DRY
Modules with different lifecycle/ownership → skip. Intentional duplication for decoupling → skip
KISS
Framework-required abstraction (e.g., DI in Spring) → downgrade. Single implementation today but interface for testing → skip
YAGNI
Feature flag used in A/B testing → skip. Config option used by ops team → skip
Error Handling
Centralized handler absent in 50-line script → downgrade to LOW
DI
Dependencies replaceable via params/closures → skip ARCH-DI
Audit Rules
1. DRY Violations (Don't Repeat Yourself)
MANDATORY READ:
Load
references/detection_patterns.md
for detection steps per type.
Type
What
Severity
Exception (skip/downgrade)
Default Recommendation
Effort
1.1
Identical Code
Same functions/constants/blocks (>10 lines) in multiple files
HIGH: business-critical (auth, payment). MEDIUM: utilities. LOW: simple constants <5x
Different lifecycle/ownership modules → skip. Intentional decoupling → skip
Extract function → decide location by duplication scope
M
1.2
Duplicated Validation
Same validation patterns (email, password, phone, URL) across files
HIGH: auth/payment. MEDIUM: user input 3+x. LOW: format checks <3x
Different security contexts (auth vs public) → skip
Extract to shared validators module
M
1.3
Repeated Error Messages
Hardcoded error strings instead of centralized catalog
MEDIUM: critical messages hardcoded or no error catalog. LOW: <3 places
User-facing strings requiring per-context wording → downgrade
Create constants/error-messages file
M
1.4
Similar Patterns
Functions with same call sequence/control flow but different names/entities
MEDIUM: business logic in critical paths. LOW: utilities <3x
Modules with divergent evolution expected → skip
Extract common logic (see decision tree for pattern)
M
1.5
Duplicated SQL/ORM
Same queries in different services
HIGH: payment/auth queries. MEDIUM: common 3+x. LOW: simple <3x
Different bounded contexts; shared DB is worse than duplication → skip
Extract to Repository layer
M
1.6
Copy-Pasted Tests
Identical setup/teardown/fixtures across test files
MEDIUM: setup in 5+ files. LOW: <5 files
Tests intentionally isolated for clarity/independence → downgrade
Extract to test helpers
M
1.7
Repeated API Responses
Same response object shapes without DTOs
MEDIUM: in 5+ endpoints. LOW: <5 endpoints
Responses with different versioning lifecycle → skip
Create DTO/Response classes
M
1.8
Duplicated Middleware Chains
Identical middleware/decorator stacks on multiple routes
MEDIUM: same chain on 5+ routes. LOW: <5 routes
Routes with different auth/rate-limit requirements → skip
Create named middleware group, apply at router level
M
1.9
Duplicated Type Definitions
Interfaces/structs/types with 80%+ same fields
MEDIUM: in 5+ files. LOW: 2-4 files
Types with different ownership/evolution paths → skip
Create shared base type, extend where needed
M
1.10
Duplicated Mapping Logic
Same entity→DTO / DTO→entity transformations in multiple locations
MEDIUM: in 3+ locations. LOW: 2 locations
Mappings with different validation/enrichment rules → skip
Create dedicated Mapper class/function
M
Recommendation selection:
Use
references/refactoring_decision_tree.md
to choose the right refactoring pattern based on duplication location (Level 1) and logic type (Level 2).
2. KISS Violations (Keep It Simple, Stupid)
Violation
Detection
Severity
Exception (skip/downgrade)
Recommendation
Effort
Abstract class with 1 implementation
Grep
abstract class
→ count subclasses
HIGH: prevents understanding core logic
Interface for DI/testing → skip. Framework-required (Spring, ASP.NET) → skip
Remove abstraction, inline
L
Factory for <3 types
Grep factory patterns → count branches
MEDIUM: unnecessary pattern
Factory used for DI/testing swap → downgrade
Replace with direct construction
M
Deep inheritance >3 levels
Trace extends chain
HIGH: fragile hierarchy
Framework-mandated hierarchy (UI widgets, ORM models) → downgrade
Flatten with composition
L
Excessive generic constraints
Grep
JSON block containing all DRY findings with pattern_signature for cross-domain matching by ln-620 coordinator. Follow shared/templates/audit_worker_report_template.md . pattern_id: DRY type identifier ( dry_1.1 through dry_1.10 ). Omit for non-DRY findings. pattern_signature: Normalized key for the detected pattern (e.g., validation_email , sql_users_findByEmail , middleware_auth_validate_ratelimit ). Same signature in multiple domains triggers cross-domain DRY finding. Format is defined in references/detection_patterns.md . Return summary to coordinator: Report written: docs/project/.audit/ln-620/{YYYY-MM-DD}/623-principles-users.md Score: X.X/10 | Issues: N (C:N H:N M:N L:N) Critical Rules MANDATORY READ: Load shared/references/audit_worker_core_contract.md . Do not auto-fix: Report only Domain-aware scanning: If domain_mode="domain-aware" , scan ONLY scan_path Tag findings: Include domain field in each finding when domain-aware Pattern signatures: Include pattern_id + pattern_signature for every DRY finding Context-aware: Use project's principles.md to define what's acceptable Effort realism: S = <1h, M = 1-4h, L = >4h Exclusions: Skip generated code, vendor, migrations (see detection_patterns.md#exclusions ) Definition of Done MANDATORY READ: Load shared/references/audit_worker_core_contract.md . contextStore parsed (including domain_mode, current_domain, output_dir) scan_path determined (domain path or codebase root) Detection patterns loaded from references/detection_patterns.md All 7 checks completed (scoped to scan_path): DRY (10 subcategories: 1.1-1.10), KISS, YAGNI, Error Handling, Centralized Errors, DI/Init, Best Practices Guide Recommendations selected via references/refactoring_decision_tree.md Findings collected with severity, location, effort, pattern_id, pattern_signature, recommendation, domain Score calculated per shared/references/audit_scoring.md Report written to {output_dir}/623-principles-{domain}.md with FINDINGS-EXTENDED block (atomic single Write call) Summary returned to coordinator Reference Files Detection patterns: references/detection_patterns.md Refactoring decision tree: references/refactoring_decision_tree.md Version: 5.0.0 Last Updated: 2026-02-08