ln-623-duplication-overabstraction-auditor

name	ln-623-duplication-overabstraction-auditor
description	Checks evidence-backed duplication, over-abstraction, and unused extensibility. Use when auditing DRY/KISS/YAGNI risk.
allowed-tools	Read, Grep, Glob, Bash, mcp__hex-graph__audit_workspace, mcp__hex-graph__find_implementations, mcp__hex-line__read_file, mcp__hex-line__grep_search, mcp__hex-line__outline
license	MIT

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

Duplication & Over-Abstraction Auditor (L3 Worker)

Type: L3 Worker

Specialized worker auditing duplication, over-abstraction, and unused extensibility.

Purpose & Scope

• Audit duplication and over-abstraction (DRY/KISS/YAGNI)
• Return structured findings with severity, location, effort, pattern_signature, recommendations
• Emit MERGE_DUPLICATION, REMOVE_ABSTRACTION, or REMOVE_YAGNI
• Calculate compliance score (X/10) for Duplication & Over-Abstraction category

Inputs

MANDATORY READ: Load references/audit_worker_core_contract.md and references/mcp_tool_preferences.md. Tool policy: You may run as an isolated subagent where host AGENTS.md is not in scope, so default to hex-line MCP first for file reads, search, and edits. Load references/mcp_integration_patterns.md only when MCP behavior is unclear.

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).

Use hex-graph first when clone groups, implementations, or semantic relationships materially improve the audit. Use hex-line first for local code reads when available. If MCP is unavailable, unsupported, or not indexed, continue with built-in Read/Grep/Glob/Bash and state the fallback in the report.

Workflow

Detection policy: use two-layer detection (candidate scan, then context verification); load references/two_layer_detection.md only when the verification method is ambiguous.

1. Parse context -- extract fields, determine scan_path (domain-aware if specified), extract output_dir
2. Load detection patterns
   • MANDATORY READ: Load references/detection_patterns.md for language-specific Grep/Glob patterns
   • Select patterns matching project's tech_stack
3. Scan codebase for violations (Layer 1)
   • All Grep/Glob patterns use scan_path (not codebase_root)
   • Graph acceleration (if available): IF contextStore.graph_indexed OR .hex-skills/codegraph/index.db exists:
     • DRY (1.1-1.10): audit_workspace(path=scan_path, verbosity="minimal", limit=5, clone_member_limit=3) -- each returned clone group = DRY candidate. Raise limits only for deliberate drill-down. Use clone kind and hotspot context for severity triage. Fall back to grep patterns if unavailable.
     • KISS inheritance: find_implementations(symbol) for abstract classes -- count implementations (1 = KISS candidate). Trace inheritance depth via graph.
     • Complexity: audit_workspace(path=scan_path, verbosity="minimal", limit=5) -- use returned hotspots to pre-identify complex functions for KISS/quality analysis. Raise limit only for deliberate drill-down.
     • Outline-first read: outline(file_path) before reading large source files -- understand structure before analyzing principles.
   • Follow step-by-step detection from detection_patterns.md
   • Apply exclusions from detection_patterns.md#exclusions
4. 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
5. Generate recommendations
   • MANDATORY READ: Load references/refactoring_decision_tree.md for pattern selection
   • Match each finding to appropriate refactoring pattern via decision tree

Two-Layer Detection

Detection policy: use two-layer detection (candidate scan, then context verification); load references/two_layer_detection.md only when the verification method is ambiguous.

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

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

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 <T extends ... & ...>	LOW: acceptable tradeoff	Type safety for public API boundary -> skip	Simplify constraints	M
Wrapper-only classes	Read: all methods delegate to inner	MEDIUM: unnecessary indirection	Adapter pattern for external API isolation -> skip	Remove wrapper, use inner directly	M

3. YAGNI Violations (You Aren't Gonna Need It)

Violation	Detection	Severity	Exception (skip/downgrade)	Recommendation	Effort
Dead feature flags (always true/false)	Grep flags -> verify never toggled	LOW: cleanup needed	A/B testing flags -> skip. Ops-controlled toggles -> skip	Remove flag, keep active code path	M
Abstract methods never overridden	Grep abstract -> search implementations	MEDIUM: unused extensibility	Plugin/extension point in public library -> downgrade	Remove abstract, make concrete	M
Unused config options	Grep config key -> 0 references	LOW: dead config	Env-specific configs (staging/prod) -> verify before flagging	Remove option	S
Interface with 1 implementation	Grep interface -> count implementors	MEDIUM: premature abstraction	Interface for DI/testing mock -> skip	Remove interface, use class directly	M
Premature generics (used with 1 type)	Grep generic usage -> count type params	LOW: over-engineering	Public library API designed for consumers -> skip	Replace generic with concrete type	S

4. Evidence Gate

Do not report aesthetic preferences. A finding is valid only when the worker can show repeated code, an abstraction with no real variation point, or unused extensibility that adds maintenance cost.

Issue	Required Evidence	Action
Duplication	matching code blocks, repeated validation/query/mapping, or pattern_signature repeated across files	MERGE_DUPLICATION
Over-abstraction	abstraction layer with one real implementation and no framework/testing need	REMOVE_ABSTRACTION
YAGNI	feature flag, config option, generic, or extension point with no current use	REMOVE_YAGNI

Scoring Algorithm

MANDATORY READ: Load references/audit_scoring.md.

Output Format

MANDATORY READ: Load references/templates/audit_worker_report_template.md.

Write JSON summary per references/audit_summary_contract.md. In managed mode the caller passes both runId and summaryArtifactPath; in standalone mode the worker generates its own run-scoped artifact path per shared contract.

Write report to {output_dir}/ln-623--{domain}.md (or 623-principles.md in global mode) with category: "Duplication & Over-Abstraction".

FINDINGS-EXTENDED block (required for this worker): After the Findings table, include a <!-- FINDINGS-EXTENDED --> JSON block containing all DRY findings with pattern_signature for managed aggregation. Follow references/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 per references/audit_summary_contract.md.

When summaryArtifactPath is absent, write the standalone runtime summary under .hex-skills/runtime-artifacts/runs/{run_id}/evaluation-worker/{worker}--{identifier}.json and optionally echo the same summary in structured output.

Report written: .hex-skills/runtime-artifacts/runs/{run_id}/audit-report/ln-623--users.md
Score: X.X/10 | Issues: N (C:N H:N M:N L:N)

Critical Rules

Apply the already-loaded 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)
• Unique angle: Audit only duplication, over-abstraction, and unused extensibility. Do not audit delivery gates, security, package health, local complexity metrics, architecture boundaries, or runtime lifecycle.
• Action required: Every finding uses MERGE_DUPLICATION, REMOVE_ABSTRACTION, or REMOVE_YAGNI.

Definition of Done

Apply the already-loaded 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 3 checks completed (scoped to scan_path):
  • DRY (10 subcategories: 1.1-1.10), KISS, YAGNI
• Recommendations selected via references/refactoring_decision_tree.md
• Findings collected with severity, location, effort, action, pattern_id, pattern_signature, recommendation, domain
• Score calculated per references/audit_scoring.md
• Report written to {output_dir}/ln-623--{domain}.md with FINDINGS-EXTENDED block (atomic single Write call)
• Summary written per contract

Reference Files

• Detection patterns: references/detection_patterns.md
• Refactoring decision tree: references/refactoring_decision_tree.md

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Version: 5.0.0 Last Updated: 2026-02-08