Ln 640 Pattern Evolution Auditor

---
name: ln-640-pattern-evolution-auditor
description: "Audits architectural patterns against best practices. Maintains patterns catalog, calculates 4 scores per pattern. Output: patterns_catalog.md."
license: MIT
---

> **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.

# Pattern Evolution Auditor

L2 Coordinator that analyzes implemented architectural patterns against current best practices and tracks evolution over time.

## Purpose & Scope

- Maintain `docs/project/patterns_catalog.md` with implemented patterns
- Research best practices via MCP Ref, Context7, WebSearch
- Audit layer boundaries via ln-642 (detect violations, check coverage)
- Calculate 4 scores per pattern via ln-641
- Track quality trends over time (improving/stable/declining)
- Output: `docs/project/patterns_catalog.md` (file-based)

## 4-Score Model

| Score | What it measures | Threshold |
|-------|------------------|-----------|
| **Compliance** | Industry standards, naming, tech stack conventions, layer boundaries | 70% |
| **Completeness** | All components, error handling, observability, tests | 70% |
| **Quality** | Readability, maintainability, no smells, SOLID, no duplication | 70% |
| **Implementation** | Code exists, production use, integrated, monitored | 70% |

## Worker Invocation

**MANDATORY READ:** Load `shared/references/task_delegation_pattern.md`.

| Worker | Purpose | Phase |
|--------|---------|-------|
| ln-641-pattern-analyzer | Calculate 4 scores per pattern | Phase 5 |
| ln-642-layer-boundary-auditor | Detect layer violations | Phase 4 |
| ln-643-api-contract-auditor | Audit API contracts, DTOs, layer leakage | Phase 4 |
| ln-644-dependency-graph-auditor | Build dependency graph, detect cycles, validate boundaries, calculate metrics | Phase 4 |
| ln-645-open-source-replacer | Search OSS replacements for custom modules via MCP Research | Phase 4 |
| ln-646-project-structure-auditor | Audit physical structure, hygiene, naming conventions | Phase 4 |

All delegations use Agent with `subagent_type: "general-purpose"`. Keep Phase 4 workers parallel where inputs are independent; keep ln-641 in Phase 5 because pattern scoring depends on earlier boundary and graph evidence.

## Workflow

**MANDATORY READ:** Load `shared/references/two_layer_detection.md` for detection methodology.

### Phase 1a: Baseline Detection

```
1. Load docs/project/patterns_catalog.md
   IF missing → create from shared/templates/patterns_template.md
   IF exists → verify template conformance:
     required_sections = ["Score Legend", "Pattern Inventory", "Discovered Patterns",
       "Layer Boundary Status", "API Contract Status", "Quick Wins",
       "Patterns Requiring Attention", "Pattern Recommendations",
       "Excluded Patterns", "Summary"]
     FOR EACH section IN required_sections:
       IF section NOT found in catalog:
         → Append section from shared/templates/patterns_template.md
     Verify table columns match template (e.g., Recommendation in Quick Wins)
     IF columns mismatch → update table headers, preserve existing data rows

2. Load docs/reference/adrs/*.md → link patterns to ADRs
   Load docs/reference/guides/*.md → link patterns to Guides

3. Auto-detect baseline patterns
   FOR EACH pattern IN pattern_library.md "Pattern Detection" table:
     Grep(detection_keywords) on codebase
     IF found but not in catalog → add as "Undocumented (Baseline)"
```

### Phase 1b: Adaptive Discovery

**MANDATORY READ:** Load `references/pattern_library.md` — use "Discovery Heuristics" section.

Predefined patterns are a **seed, not a ceiling**. Discover project-specific patterns beyond the baseline.

```
# Structural heuristics (from pattern_library.md)
1. Class naming: Grep GoF suffixes (Factory|Builder|Strategy|Adapter|Observer|...)
2. Abstract hierarchy: ABC/Protocol with 2+ implementations → Template Method/Strategy
3. Fluent interface: return self chains → Builder
4. Registration dict: _registry + register() → Registry
5. Middleware chain: app.use/add_middleware → Chain of Responsibility
6. Event listeners: @on_event/@receiver/signal → Observer
7. Decorator wrappers: @wraps/functools.wraps → Decorator

# Document-based heuristics
8. ADR/Guide filenames + H1 headers → extract pattern names not in library
9. Architecture.md → grep pattern terminology
10. Code comments → "pattern:|@pattern|design pattern"

# Output per discovered pattern:
  {name, evidence: [files], confidence: HIGH|MEDIUM|LOW, status: "Discovered"}
  → Add to catalog "Discovered Patterns (Adaptive)" section
```

### Phase 1c: Pattern Recommendations

Suggest patterns that COULD improve architecture (advisory, NOT scored).

```
# Check conditions from pattern_library.md "Pattern Recommendations" table
# E.g., external API calls without retry → recommend Resilience
# E.g., 5+ constructor params → recommend Builder/Parameter Object
# E.g., direct DB access from API layer → recommend Repository

→ Add to catalog "Pattern Recommendations" section
```

### Phase 1d: Applicability Verification

Verify each detected pattern is actually implemented, not just a keyword false positive.

**MANDATORY READ:** Load `references/scoring_rules.md` — use "Required components by pattern" table.

```
FOR EACH detected_pattern IN (baseline_detected + adaptive_discovered):
  IF pattern.source == "adaptive":
    # Adaptive patterns: check confidence + evidence volume
    IF pattern.confidence == "LOW" AND len(pattern.evidence.files) < 3:
      pattern.status = "EXCLUDED"
      pattern.exclusion_reason = "Low confidence, insufficient evidence"
      → Add to catalog "Excluded Patterns" section
      CONTINUE
  ELSE:
    # Baseline patterns: check minimum 2 structural components
    components = get_required_components(pattern, scoring_rules.md)
    found_count = 0
    FOR EACH component IN components:
      IF Grep(component.detection_grep, codebase) has matches:
        found_count += 1
    IF found_count < 2:
      pattern.status = "EXCLUDED"
      pattern.exclusion_reason = "Found {found_count}/{len(components)} components"
      → Add to catalog "Excluded Patterns" section
      CONTINUE

  pattern.status = "VERIFIED"

# Step 2: Semantic applicability via MCP Ref (after structural check passes)
FOR EACH pattern WHERE pattern.status == "VERIFIED":
  ref_search_documentation("{pattern.name} {tech_stack.language} idiom vs architectural pattern")
  WebSearch("{pattern.name} {tech_stack.language} — language feature or design pattern?")

  IF evidence shows pattern is language idiom / stdlib feature / framework built-in:
    pattern.status = "EXCLUDED"
    pattern.exclusion_reason = "Language idiom / built-in feature, not architectural pattern"
    → Add to catalog "Excluded Patterns" section

# Cleanup: remove stale patterns from previous audits
FOR EACH pattern IN existing_catalog WHERE NOT detected in current scan:
  → REMOVE from Pattern Inventory
  → Add to "Excluded Patterns" with reason "No longer detected in codebase"
```

### Phase 2: Best Practices Research

```
FOR EACH pattern WHERE last_audit > 30 days OR never:

  # MCP Ref + Context7 + WebSearch
  ref_search_documentation("{pattern} best practices {tech_stack}")
  IF pattern.library: query-docs(library_id, "{pattern}")
  WebSearch("{pattern} implementation best practices 2026")

  → Store: contextStore.bestPractices[pattern]
```

### Phase 3: Domain Discovery + Output Setup

**MANDATORY READ:** Load `shared/references/audit_coordinator_domain_mode.md`.

Use the shared domain discovery pattern to set `domain_mode` and `all_domains`. Then create `docs/project/.audit/ln-640/{YYYY-MM-DD}/`. Worker files are cleaned up after consolidation (see Phase 11).

### Phase 4: Layer Boundary + API Contract + Dependency Graph Audit

```javascript
IF domain_mode == "domain-aware":
  FOR EACH domain IN all_domains:
    domain_context = {
      ...contextStore,
      domain_mode: "domain-aware",
      current_domain: { name: domain.name, path: domain.path }
    }
    FOR EACH worker IN [ln-642, ln-643, ln-644, ln-645, ln-646]:
      Agent(description: "Audit " + domain.name + " via " + worker,
           prompt: "Execute audit worker.

Step 1: Invoke worker:
  Skill(skill: \"" + worker + "\")

CONTEXT:
" + JSON.stringify(domain_context),
           subagent_type: "general-purpose")
ELSE:
  FOR EACH worker IN [ln-642, ln-643, ln-644, ln-645, ln-646]:
    Agent(description: "Pattern evolution audit via " + worker,
         prompt: "Execute audit worker.

Step 1: Invoke worker:
  Skill(skill: \"" + worker + "\")

CONTEXT:
" + JSON.stringify(contextStore),
         subagent_type: "general-purpose")

# Apply layer deductions from ln-642 return values (score + issue counts)
# Detailed violations read from files in Phase 6
```

### Phase 5: Pattern Analysis Loop

```javascript
# ln-641 stays GLOBAL (patterns are cross-cutting, not per-domain)
# Only VERIFIED patterns from Phase 1d (skip EXCLUDED)
FOR EACH pattern IN catalog WHERE pattern.status == "VERIFIED":
  Agent(description: "Analyze " + pattern.name + " via ln-641",
       prompt: "Execute audit worker.

Step 1: Invoke worker:
  Skill(skill: \"ln-641-pattern-analyzer\")

CONTEXT:
" + JSON.stringify({...contextStore, pattern: pattern}),
       subagent_type: "general-purpose")
```

**Worker Output Contract (file-based):**

**MANDATORY READ:** Load `shared/references/audit_worker_core_contract.md` and `shared/templates/audit_worker_report_template.md`.

All workers write reports to `{output_dir}/` and return minimal summary:

| Worker | Return Format | File |
|--------|--------------|------|
| ln-641 | `Score: X.X/10 (C:N K:N Q:N I:N) \| Issues: N` | `641-pattern-{slug}.md` |
| ln-642 | `Score: X.X/10 \| Issues: N (C:N H:N M:N L:N)` | `642-layer-boundary[-{domain}].md` |
| ln-643 | `Score: X.X/10 (C:N K:N Q:N I:N) \| Issues: N` | `643-api-contract[-{domain}].md` |
| ln-644 | `Score: X.X/10 \| Issues: N (C:N H:N M:N L:N)` | `644-dep-graph[-{domain}].md` |
| ln-645 | `Score: X.X/10 \| Issues: N (C:N H:N M:N L:N)` | `645-open-source-replacer[-{domain}].md` |
| ln-646 | `Score: X.X/10 \| Issues: N (C:N H:N M:N L:N)` | `646-structure[-{domain}].md` |

Coordinator parses scores/counts from return values (0 file reads for aggregation tables). Reads files only for cross-domain aggregation (Phase 6) and report assembly (Phase 8).

### Phase 6: Cross-Domain Aggregation (File-Based)

```
IF domain_mode == "domain-aware":
  # Step 1: Read DATA-EXTENDED from ln-642 files
  FOR EACH file IN Glob("{output_dir}/642-layer-boundary-*.md"):
    Read file → extract <!-- DATA-EXTENDED ... --> JSON + Findings table
  # Group findings by issue type across domains
  FOR EACH issue_type IN unique(ln642_findings.issue):
    domains_with_issue = ln642_findings.filter(f => f.issue == issue_type).map(f => f.domain)
    IF len(domains_with_issue) >= 2:
      systemic_findings.append({
        severity: "CRITICAL",
        issue: f"Systemic layer violation: {issue_type} in {len(domains_with_issue)} domains",
        domains: domains_with_issue,
        recommendation: "Address at architecture level, not per-domain"
      })

  # Step 2: Read DATA-EXTENDED from ln-643 files
  FOR EACH file IN Glob("{output_dir}/643-api-contract-*.md"):
    Read file → extract <!-- DATA-EXTENDED ... --> JSON (issues with principle + domain)
  # Group findings by rule across domains
  FOR EACH rule IN unique(ln643_issues.principle):
    domains_with_issue = ln643_issues.filter(i => i.principle == rule).map(i => i.domain)
    IF len(domains_with_issue) >= 2:
      systemic_findings.append({
        severity: "HIGH",
        issue: f"Systemic API contract issue: {rule} in {len(domains_with_issue)} domains",
        domains: domains_with_issue,
        recommendation: "Create cross-cutting architectural fix"
      })

  # Step 3: Read DATA-EXTENDED from ln-644 files
  FOR EACH file IN Glob("{output_dir}/644-dep-graph-*.md"):
    Read file → extract <!-- DATA-EXTENDED ... --> JSON (cycles, sdp_violations)
  # Cross-domain cycles
  FOR EACH cycle IN ln644_cycles:
    domains_in_cycle = unique(cycle.path.map(m => m.domain))
    IF len(domains_in_cycle) >= 2:
      systemic_findings.append({
        severity: "CRITICAL",
        issue: f"Cross-domain dependency cycle: {cycle.path} spans {len(domains_in_cycle)} domains",
        domains: domains_in_cycle,
        recommendation: "Decouple via domain events or extract shared module"
      })

  # Step 4: Read DATA-EXTENDED from ln-645 files
  FOR EACH file IN Glob("{output_dir}/645-open-source-replacer-*.md"):
    Read file → extract <!-- DATA-EXTENDED ... --> JSON (replacements array)
  # Group findings by goal/alternative across domains
  FOR EACH goal IN unique(ln645_replacements.goal):
    domains_with_same = ln645_replacements.filter(r => r.goal == goal).map(r => r.domain)
    IF len(domains_with_same) >= 2:
      systemic_findings.append({
        severity: "HIGH",
        issue: f"Systemic custom implementation: {goal} duplicated in {len(domains_with_same)} domains",
        domains: domains_with_same,
        recommendation: "Single migration across all domains using recommended OSS package"
      })

  # Step 5: Read DATA-EXTENDED from ln-646 files
  FOR EACH file IN Glob("{output_dir}/646-structure-*.md"):
    Read file -> extract <!-- DATA-EXTENDED ... --> JSON
  # Group findings by dimension across domains
  FOR EACH dimension IN ["junk_drawers", "naming_violations"]:
    domains_with_issue = ln646_data.filter(d => d.dimensions[dimension].issues > 0).map(d => d.domain)
    IF len(domains_with_issue) >= 2:
      systemic_findings.append({
        severity: "MEDIUM",
        issue: f"Systemic structure issue: {dimension} in {len(domains_with_issue)} domains",
        domains: domains_with_issue,
        recommendation: "Standardize project structure conventions across domains"
      })

  # Cross-domain SDP violations
  FOR EACH sdp IN ln644_sdp_violations:
    IF sdp.from.domain != sdp.to.domain:
      systemic_findings.append({
        severity: "HIGH",
        issue: f"Cross-domain stability violation: {sdp.from} (I={sdp.I_from}) depends on {sdp.to} (I={sdp.I_to})",
        domains: [sdp.from.domain, sdp.to.domain],
        recommendation: "Apply DIP: extract interface at domain boundary"
      })
```

### Phase 7: Gap Analysis

```
gaps = {
  undocumentedPatterns: found in code but not in catalog,
  missingComponents: required components not found per scoring_rules.md,
  layerViolations: code in wrong architectural layers,
  consistencyIssues: conflicting patterns,
  systemicIssues: systemic_findings from Phase 6
}
```

### Aggregation Algorithm

**MANDATORY READ:** Load `shared/references/audit_coordinator_aggregation.md` and `shared/references/context_validation.md`.

```
# Step 1: Parse scores from worker return values (already in-context)
# ln-641: "Score: 7.9/10 (C:72 K:85 Q:68 I:90) | Issues: 3 (H:1 M:2 L:0)"
# ln-642: "Score: 4.5/10 | Issues: 8 (C:1 H:3 M:4 L:0)"
# ln-643: "Score: 6.75/10 (C:65 K:70 Q:55 I:80) | Issues: 4 (H:2 M:1 L:1)"
# ln-644: "Score: 6.5/10 | Issues: 8 (C:1 H:3 M:3 L:1)"
pattern_scores = [parse_score(r) for r in ln641_returns]  # Each 0-10
layer_score = parse_score(ln642_return)                     # 0-10
api_score = parse_score(ln643_return)                       # 0-10
graph_score = parse_score(ln644_return)                     # 0-10
structure_score = parse_score(ln646_return)                   # 0-10

# Step 2: Calculate architecture_health_score (ln-645 NOT included — separate metric)
all_scores = pattern_scores + [layer_score, api_score, graph_score, structure_score]
architecture_health_score = round(average(all_scores) * 10)  # 0-100 scale

# Step 2b: Separate reuse opportunity score (informational, no SLA enforcement)
reuse_opportunity_score = parse_score(ln645_return)  # 0-10, NOT in architecture_health_score

# Status mapping:
# >= 80: "healthy"
# 70-79: "warning"
# < 70: "critical"

# Step 3: Context Validation (Post-Filter)
# Apply Rules 1, 3 to ln-641 anti-pattern findings:
#   Rule 1: Match god_class/large_file findings against ADR list
#   Rule 3: For god_class deductions (-5 compliance):
#     Read flagged file ONCE, check 4 cohesion indicators
#     (public_func_count <= 2, subdirs, shared_state > 60%, CC=1)
#     IF cohesion >= 3: restore deducted -5 points
#     Note in patterns_catalog.md: "[Advisory: high cohesion module]"
# Recalculate architecture_health_score with restored points
```

### Phase 8: Report + Trend Analysis
```
1. Update patterns_catalog.md:
   - Pattern scores, dates
   - Layer Boundary Status section
   - Quick Wins section
   - Patterns Requiring Attention section
2. Calculate trend: compare current vs previous scores
3. Output summary (see Return Result below)
```

### Phase 9: Return Result

```json
{
  "audit_date": "2026-02-04",
  "architecture_health_score": 78,
  "trend": "improving",
  "patterns_analyzed": 5,
  "layer_audit": {
    "architecture_type": "Layered",
    "violations_total": 5,
    "violations_by_severity": {"high": 2, "medium": 3, "low": 0},
    "coverage": {"http_abstraction": 85, "error_centralization": true}
  },
  "patterns": [
    {
      "name": "Job Processing",
      "scores": {"compliance": 72, "completeness": 85, "quality": 68, "implementation": 90},
      "avg_score": 79,
      "status": "warning",
      "issues_count": 3
    }
  ],
  "quick_wins": [
    {"pattern": "Caching", "issue": "Add TTL config", "effort": "2h", "impact": "+10 completeness"}
  ],
  "requires_attention": [
    {"pattern": "Event-Driven", "avg_score": 58, "critical_issues": ["No DLQ", "No schema versioning"]}
  ],
  "project_structure": {
    "structure_score": 7.5,
    "tech_stack_detected": "react",
    "dimensions": {
      "file_hygiene": {"checks": 6, "issues": 1},
      "ignore_files": {"checks": 4, "issues": 0},
      "framework_conventions": {"checks": 3, "issues": 1},
      "domain_organization": {"checks": 3, "issues": 1},
      "naming_conventions": {"checks": 3, "issues": 0}
    },
    "junk_drawers": 1,
    "naming_violations_pct": 3
  },
  "reuse_opportunities": {
    "reuse_opportunity_score": 6.5,
    "modules_scanned": 15,
    "high_confidence_replacements": 3,
    "medium_confidence_replacements": 5,
    "systemic_custom_implementations": 1
  },
  "dependency_graph": {
    "architecture_detected": "hybrid",
    "architecture_confidence": "MEDIUM",
    "modules_analyzed": 12,
    "cycles_detected": 2,
    "boundary_violations": 3,
    "sdp_violations": 1,
    "nccd": 1.3,
    "score": 6.5
  },
  "cross_domain_issues": [
    {
      "severity": "CRITICAL",
      "issue": "Systemic layer violation: HTTP client in domain layer in 3 domains",
      "domains": ["users", "billing", "orders"],
      "recommendation": "Address at architecture level"
    }
  ]
}
```

## Phase 10: Append Results Log

**MANDATORY READ:** Load `shared/references/results_log_pattern.md`

Append one row to `docs/project/.audit/results_log.md` with: Skill=`ln-640`, Metric=`architecture_health_score`, Scale=`0-100`, Score from Phase 9 output. Calculate Delta vs previous `ln-640` row. Create file with header if missing. Rolling window: max 50 entries.

## Critical Rules

- **MCP Ref first:** Always research best practices before analysis
- **Layer audit first:** Run ln-642 before ln-641 pattern analysis
- **4 scores mandatory:** Never skip any score calculation
- **Layer deductions:** Apply scoring_rules.md deductions for violations
- **File output only:** Write results to patterns_catalog.md; no side-effect task/issue creation

## Phase 11: Cleanup Worker Files

```bash
rm -rf {output_dir}
```

Delete the dated output directory (`docs/project/.audit/ln-640/{YYYY-MM-DD}/`). The consolidated report and results log already preserve all audit data.

## Definition of Done

- Pattern catalog loaded or created
- Applicability verified for all detected patterns (Phase 1d); excluded patterns documented
- Best practices researched for all VERIFIED patterns needing audit
- Domain discovery completed (global or domain-aware mode selected)
- Output directory `docs/project/.audit/ln-640/{YYYY-MM-DD}/` created for worker reports
- Worker output directory cleaned up after consolidation
- Layer boundaries audited via ln-642 (reports written to `{output_dir}/`)
- API contracts audited via ln-643 (reports written to `{output_dir}/`)
- Dependency graph audited via ln-644 (reports written to `{output_dir}/`)
- All patterns analyzed via ln-641 (reports written to `{output_dir}/`)
- Open-source replacement opportunities audited via ln-645 (reports written to `{output_dir}/`)
- Project structure audited via ln-646 (reports written to `{output_dir}/`)
- If domain-aware: cross-domain aggregation completed via DATA-EXTENDED from files
- Gaps identified (undocumented, missing components, layer violations, inconsistent, systemic)
- Catalog updated with scores, dates, Layer Boundary Status
- Trend analysis completed (current vs previous scores compared)
- Summary report output

## Phase 12: Meta-Analysis

**MANDATORY READ:** Load `shared/references/meta_analysis_protocol.md`

Skill type: `review-coordinator` (workers only). Run after all phases complete. Output to chat using the `review-coordinator — workers only` format.

## Reference Files

- **Task delegation pattern:** `shared/references/task_delegation_pattern.md`
- **Domain mode pattern:** `shared/references/audit_coordinator_domain_mode.md`
- **Aggregation pattern:** `shared/references/audit_coordinator_aggregation.md`
- Pattern catalog template: `shared/templates/patterns_template.md`
- Pattern library (detection + best practices + discovery): `references/pattern_library.md`
- Layer boundary rules (for ln-642): `references/layer_rules.md`
- Scoring rules: `references/scoring_rules.md`
- Pattern analysis: `../ln-641-pattern-analyzer/SKILL.md`
- Layer boundary audit: `../ln-642-layer-boundary-auditor/SKILL.md`
- API contract audit: `../ln-643-api-contract-auditor/SKILL.md`
- Dependency graph audit: `../ln-644-dependency-graph-auditor/SKILL.md`
- Open-source replacement audit: `../ln-645-open-source-replacer/SKILL.md`
- Project structure audit: `../ln-646-project-structure-auditor/SKILL.md`
- **MANDATORY READ:** `shared/references/research_tool_fallback.md`
- **MANDATORY READ:** `shared/references/tools_config_guide.md`
- **MANDATORY READ:** `shared/references/storage_mode_detection.md`

---
**Version:** 2.0.0
**Last Updated:** 2026-02-08