Code Quality Checker

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

Code Quality Score

Code Quality Score = 100 - metric_penalties - issue_penalties

Issue Prefixes

When to Use

• Invoked by ln-500-story-quality-gate Pass 1 (first gate)
• All implementation tasks in Story status = Done
• Before regression testing (ln-502) and test planning (ln-510)

Workflow (concise)

1. Load Story (full) and Done implementation tasks (full descriptions) via Linear; skip tasks with label "tests".
2. Collect affected files from tasks (Affected Components/Existing Code Impact) and recent commits/diffs if noted.
3. Calculate code metrics:
   • Cyclomatic Complexity per function (target ≤10)
   • Function size (target ≤50 lines)
   • File size (target ≤500 lines)
   • Nesting depth (target ≤3)
   • Parameter count (target ≤4)

• 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 approach vs alternatives for project context
• Flag suboptimal choices as OPT- issues

• Research:

  ref_search_documentation("{chosen_approach} best practices {tech_stack} 2026")

• For libraries:

  query-docs(library_id, "best practices implementation patterns")

• Flag deviations from recommended patterns as BP- issues

• PERF-ALG: Analyze algorithm complexity (detect O(n²)+, research optimal via MCP Ref)
• PERF-CFG: Check library configs (connection pooling, batch sizes, timeouts) via

  query-docs

• PERF-PTN: Research pattern pitfalls:

  ref_search_documentation("{pattern} performance bottlenecks")

• PERF-DB: Check for N+1, missing indexes via

  query-docs(orm_library_id, "query optimization")

• New dependency added (package.json/requirements.txt changed)
• New pattern/library used
• API/database changes
• Loops/recursion in critical paths
• ORM queries added

1. Analyze code for static issues (assign prefixes):
   • SEC-: hardcoded creds, unvalidated input, SQL injection, race conditions
   • MNT-: DRY violations, dead code, complex conditionals, poor naming
   • ARCH-: layer violations, circular dependencies, guide non-compliance
2. Calculate Code Quality Score:
   • Start with 100
   • Subtract metric penalties (see Code Metrics table)
   • Subtract issue penalties (see Issue penalties table)
3. Output verdict with score and structured issues. Add Linear comment with findings.

Critical Rules

• Read guides mentioned in Story/Tasks before judging compliance.
• MCP Ref validation: For ANY architectural change, MUST verify via ref_search_documentation before judging.
• Context7 for libraries: When reviewing library usage, query-docs to verify correct patterns.
• Language preservation in comments (EN/RU).
• Do not create tasks or change statuses; caller decides next actions.

Definition of Done

• Story and Done implementation tasks loaded (test tasks excluded).
• Code metrics calculated (Cyclomatic Complexity, function/file sizes).
• MCP Ref validation completed:
  • OPT-: Optimality checked (is chosen approach the best for the goal?)
  • BP-: Best practices verified (correct implementation of chosen approach?)
  • PERF-: Performance analyzed (algorithms, configs, patterns, DB)
• Issues identified with prefixes and severity, sources from MCP Ref/Context7.
• Code Quality Score calculated.
• Output format:
  yaml

  verdict: PASS | CONCERNS | ISSUES_FOUND
  code_quality_score: {0-100}
  metrics:
    avg_cyclomatic_complexity: {value}
    functions_over_50_lines: {count}
    files_over_500_lines: {count}
  issues:
    # OPTIMALITY
    - id: "OPT-001"
      severity: medium
      file: "src/auth/index.ts"
      goal: "User session management"
      finding: "Suboptimal approach for session management"
      chosen: "Custom JWT with localStorage"
      recommended: "httpOnly cookies + refresh token rotation"
      reason: "httpOnly cookies prevent XSS token theft"
      source: "ref://owasp-session-management"
  
    # BEST PRACTICES
    - id: "BP-001"
      severity: medium
      file: "src/api/routes.ts"
      finding: "POST for idempotent operation"
      best_practice: "Use PUT for idempotent updates (RFC 7231)"
      source: "ref://api-design-guide#idempotency"
  
    # PERFORMANCE - Algorithm
    - id: "PERF-ALG-001"
      severity: high
      file: "src/utils/search.ts:42"
      finding: "Nested loops cause O(n²) complexity"
      current: "O(n²) - nested filter().find()"
      optimal: "O(n) - use Map/Set for lookup"
      source: "ref://javascript-performance#data-structures"
  
    # PERFORMANCE - Config
    - id: "PERF-CFG-001"
      severity: medium
      file: "src/db/connection.ts"
      finding: "Missing connection pool config"
      current_config: "default (pool: undefined)"
      recommended: "pool: { min: 2, max: 10 }"
      source: "context7://pg#connection-pooling"
  
    # PERFORMANCE - Database
    - id: "PERF-DB-001"
      severity: high
      file: "src/repositories/user.ts:89"
      finding: "N+1 query pattern detected"
      issue: "users.map(u => u.posts) triggers N queries"
      solution: "Use eager loading: include: { posts: true }"
      source: "context7://prisma#eager-loading"
  
    # MAINTAINABILITY
    - id: "MNT-001"
      severity: medium
      file: "src/service.ts:42"
      finding: "DRY violation: duplicate validation logic"
      suggested_action: "Extract to shared validator"

• Linear comment posted with findings.

Reference Files

• Code metrics:

  references/code_metrics.md

  (thresholds and penalties)
• Guides:

  docs/guides/

• Templates for context:

  shared/templates/task_template_implementation.md