ln-511-code-quality-checker

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

Code Quality Checker

Type: L3 Worker Category: 5XX Quality

Analyzes Done implementation tasks with quantitative Code Quality Score based on metrics, MCP Ref validation, and issue penalties.

Inputs

| Input | Required | Source | Description | |-------|----------|--------|-------------| | storyId | Yes | args, git branch, kanban, user | Story to process |

Resolution: Story Resolution Chain. Status filter: In Progress, To Review

Tool policy: follow host AGENTS.md MCP preferences; load references/mcp_tool_preferences.md and references/mcp_integration_patterns.md only when host policy is absent or MCP behavior is unclear. - use hex-graph as the primary path for clone, architecture, and semantic quality evidence when the project is indexed. Fall back to Grep/Read only when graph is unavailable or unsupported.

Purpose & Scope

• Load Story and Done implementation tasks (exclude test tasks)
• Calculate Code Quality Score using metrics and issue penalties
• MCP Ref validation: Verify optimality, best practices, and performance via external sources
• Check for DRY/KISS/YAGNI violations, architecture boundary breaks, security issues
• Produce quantitative verdict with structured issue list; never edits Linear or kanban

Code Metrics

| Metric | Threshold | Penalty | |--------|-----------|---------| | Cyclomatic Complexity | ≤10 OK, 11-20 warning, >20 fail | -5 (warning), -10 (fail) per function | | Function size | ≤50 lines OK, >50 warning | -3 per function | | File size | ≤500 lines OK, >500 warning | -5 per file | | Nesting depth | ≤3 OK, >3 warning | -3 per instance | | Parameter count | ≤4 OK, >4 warning | -2 per function |

Code Quality Score

Formula: Code Quality Score = 100 - metric_penalties - issue_penalties

Issue penalties by severity:

| Severity | Penalty | Examples | |----------|---------|----------| | high | -20 | Security vulnerability, O(n²)+ algorithm, N+1 query | | medium | -10 | DRY violation, suboptimal approach, missing config | | low | -3 | Naming convention, minor code smell |

Score interpretation:

| Score | Status | Verdict | |-------|--------|---------| | 90-100 | Excellent | PASS | | 70-89 | Acceptable | CONCERNS | | <70 | Below threshold | ISSUES_FOUND |

Issue Prefixes

| Prefix | Category | Default Severity | MCP Ref | |--------|----------|------------------|---------| | SEC- | Security (auth, validation, secrets) | high | — | | SEC-DESTR- | Destructive ops (guards: DB, FS, MIG, ENV, FORCE) | high/medium | — | | PERF- | Performance (algorithms, configs, bottlenecks) | medium/high | ✓ Required | | MNT- | Maintainability (DRY, SOLID, complexity, dead code) | medium | — | | ARCH- | Architecture (layers, boundaries, patterns, contracts) | medium | — | | BP- | Best Practices (implementation differs from recommended) | medium | ✓ Required | | OPT- | Optimality (better approach exists for this goal) | medium | ✓ Required |

OPT- subcategories:

| Prefix | Category | Severity | |--------|----------|----------| | OPT-OSS- | Open-source replacement available | medium (high if >200 LOC) |

ARCH- subcategories:

| Prefix | Category | Severity | |--------|----------|----------| | ARCH-LB- | Layer Boundary: I/O outside infra, HTTP in domain | high | | ARCH-TX- | Transaction Boundaries: commit() in 3+ layers, mixed UoW ownership | high (CRITICAL if auth/payment) | | ARCH-DTO- | Missing DTO (4+ params without DTO), Entity Leakage (ORM entity in API response) | medium (high if auth/payment) | | ARCH-DI- | Dependency Injection: dependencies not replaceable for testing (direct instantiation, no injection mechanism). Exception: small scripts/CLIs where params/closures suffice → skip | medium | | ARCH-CEH- | Centralized Error Handling: errors silently swallowed, stack traces leak to prod, no consistent error logging. Exception: 50-line scripts → downgrade to LOW | medium (high if no handler at all) | | ARCH-SES- | Session Ownership: DI session + local session in same module | medium | | ARCH-AI-SEB | Side-Effect Breadth: 3+ side-effect categories in one leaf function. Conflict Resolution: orchestrator/coordinator functions (imports 3+ services AND delegates sequentially) are EXPECTED to have multiple categories — do NOT flag SEB | medium | | ARCH-AI-AH | Architectural Honesty: read-named function with write side-effects | medium | | ARCH-AI-FO | Flat Orchestration: leaf service imports 3+ other services. Orchestrator imports are expected — do NOT flag | medium | | ARCH-EVENT- | Event Channel Consistency: publisher/subscriber name mismatch (MISMATCH), orphaned channel with no counterpart (ORPHAN) | high (mismatch), medium (orphan) |

PERF- subcategories:

| Prefix | Category | Severity | |--------|----------|----------| | PERF-ALG- | Algorithm complexity (Big O) | high if O(n²)+ | | PERF-CFG- | Package/library configuration | medium | | PERF-PTN- | Architectural pattern performance | high | | PERF-DB- | Database queries, indexes | high |

MNT- subcategories:

| Prefix | Category | Severity | |--------|----------|----------| | MNT-DC- | Dead code: replaced implementations, unused exports/re-exports, backward-compat wrappers, unsupported aliases | medium (high if public API) | | MNT-DRY- | DRY violations: duplicate logic across files | medium | | MNT-GOD- | God Classes: class with >15 methods or >500 lines (not just file size) | medium (high if >1000 lines) | | MNT-SIG- | Method Signature Quality: boolean flag params, unclear return types, inconsistent naming, >5 optional params | low | | MNT-ERR- | Error Contract inconsistency: mixed raise + return None in same service | medium |

When to Use

• All implementation tasks in Story status = Done
• Before tech debt cleanup and inline agent review

Workflow (concise)

MANDATORY READ: Load references/input_resolution_pattern.md

1) Resolve storyId: Run Story Resolution Chain per guide (status filter: [In Progress, To Review]). 2) Load Story (full) and Done implementation tasks (full descriptions) via Linear; skip tasks with label "tests". 3) Collect changed files (changed_files[]): MANDATORY READ: Load references/git_scope_detection.md

• IF invoked by ln-510: use changed_files[] from coordinator context → proceed to Enrich step in guide
• IF invoked standalone: run full algorithm from guide

4) Two-Layer Detection (MANDATORY): MANDATORY READ: Load references/two_layer_detection.md All threshold-based findings require Layer 2 context analysis. Layer 1 finding without Layer 2 = NOT a valid finding. Before reporting any metric violation, ask: "Is this violation intentional or justified by design?" See Exception column in metrics below.

5) Calculate code metrics:

• Cyclomatic Complexity per function (target ≤10; Exception: enum/switch dispatch, state machines, parser grammars → downgrade to LOW)
• Function size (target ≤50 lines; Exception: orchestrator functions with sequential delegation)
• File size (target ≤500 lines; Exception: config/schema/migration files, generated code)
• Nesting depth (target ≤3)
• Parameter count (target ≤4; Exception: builder/options patterns)

6) MCP Ref Validation (MANDATORY for code changes — SKIP if --skip-mcp-ref flag passed): MANDATORY READ: Load references/research_tool_fallback.md

> Fast-track mode: When invoked with --skip-mcp-ref, skip this entire step (no OPT-, BP-, PERF- checks). Proceed directly to step 6 (static analysis). This reduces cost from ~5000 to ~800 tokens while preserving metrics + static analysis coverage.

Level 1 — OPTIMALITY (OPT-):

• Extract goal from task (e.g., "user authentication", "caching", "API rate limiting")
• Research alternatives: ref_search_documentation("{goal} approaches comparison {tech_stack} 2026")
• Compare chosen