drift-analysis（漂移分析）

Drift Analysis

Knowledge and patterns for analyzing project state, detecting plan drift, and creating prioritized reconstruction plans.

Architecture Overview

/drift-detect
        │
        ├─→ collectors.js (pure JavaScript)
        │   ├─ scanGitHubState()
        │   ├─ analyzeDocumentation()
        │   └─ scanCodebase()
        │
        └─→ plan-synthesizer (Opus)
            └─ Deep semantic analysis with full context

Data collection: Pure JavaScript (no LLM overhead) Semantic analysis: Single Opus call with complete context

Drift Detection Patterns

Types of Drift

Plan Drift: When documented plans diverge from actual implementation

• PLAN.md items remain unchecked for extended periods
• Roadmap milestones slip without updates
• Sprint/phase goals not reflected in code changes

Documentation Drift: When documentation falls behind implementation

• New features exist without corresponding docs
• README describes features that don't exist
• API docs don't match actual endpoints

Issue Drift: When issue tracking diverges from reality

• Stale issues that no longer apply
• Completed work without closed issues
• High-priority items neglected

Scope Drift: When project scope expands beyond original plans

• More features documented than can be delivered
• Continuous addition without completion
• Ever-growing backlog with no pruning

Detection Signals

HIGH-CONFIDENCE DRIFT INDICATORS:
- Milestone 30+ days overdue with open issues
- PLAN.md < 30% completion after 90 days
- 5+ high-priority issues stale > 60 days
- README features not found in codebase

MEDIUM-CONFIDENCE INDICATORS:
- Documentation files unchanged for 180+ days
- Draft PRs open > 30 days
- Issue themes don't match code activity
- Large gap between documented and implemented features

LOW-CONFIDENCE INDICATORS:
- Many TODOs in codebase
- Stale dependencies
- Old git branches not merged

Prioritization Framework

Priority Calculation

function calculatePriority(item, weights) {
  let score = 0;

  // Severity base score
  const severityScores = {
    critical: 15,
    high: 10,
    medium: 5,
    low: 2
  };
  score += severityScores[item.severity] || 5;

  // Category multiplier
  const categoryWeights = {
    security: 2.0,    // Security issues get 2x
    bugs: 1.5,        // Bugs get 1.5x
    infrastructure: 1.3,
    features: 1.0,
    documentation: 0.8
  };
  score *= categoryWeights[item.category] || 1.0;

  // Recency boost
  if (item.createdRecently) score *= 1.2;

  // Stale penalty (old items slightly deprioritized)
  if (item.daysStale > 180) score *= 0.9;

  return Math.round(score);
}

Time Bucket Thresholds

Priority Weights (Default)

security: 10     # Security issues always top priority
bugs: 8          # Bugs affect users directly
features: 5      # New functionality
documentation: 3 # Important but not urgent
tech-debt: 4     # Keeps codebase healthy

Cross-Reference Patterns

Document-to-Code Matching

// Fuzzy matching for feature names
function featureMatch(docFeature, codeFeature) {
  const normalize = s => s
    .toLowerCase()
    .replace(/[-_\s]+/g, '')
    .replace(/s$/, ''); // Remove trailing 's'

  const docNorm = normalize(docFeature);
  const codeNorm = normalize(codeFeature);

  return docNorm.includes(codeNorm) ||
         codeNorm.includes(docNorm) ||
         levenshteinDistance(docNorm, codeNorm) < 3;
}

Common Mismatches

Output Templates

Drift Report Section

## Drift Analysis

### {drift_type}
**Severity**: {severity}
**Detected In**: {source}

{description}

**Evidence**:
{evidence_items}

**Recommendation**: {recommendation}

Gap Report Section

## Gap: {gap_title}

**Category**: {category}
**Severity**: {severity}

{description}

**Impact**: {impact_description}

**To Address**:
1. {action_item_1}
2. {action_item_2}

Reconstruction Plan Section

## Reconstruction Plan

### Immediate Actions (This Week)
{immediate_items_numbered}

### Short-Term (This Month)
{short_term_items_numbered}

### Medium-Term (This Quarter)
{medium_term_items_numbered}

### Backlog
{backlog_items_numbered}

Best Practices

When Analyzing Drift

1. Compare timestamps, not just content

- When was the doc last updated vs. last code change? - Are milestones dated realistically?

1. Look for patterns, not individual items

- One stale issue isn't drift; 10 stale issues is a pattern - One undocumented feature isn't drift; 5 undocumented features is

1. Consider context

- Active development naturally has some drift - Mature projects should have minimal drift - Post-launch projects often have documentation lag

1. Weight by impact

- User-facing drift matters more than internal - Public API drift matters more than implementation details

When Creating Plans

1. Be actionable, not exhaustive

- Top 5 immediate items, not top 50 - Each item should be completable in reasonable time

1. Group related items

- "Update authentication docs" not "Update login page docs" + "Update signup docs"

1. Include success criteria

- How do we know this drift item is resolved?

1. Balance categories

- All security first, but don't ignore everything else - Mix quick wins with important work

Data Collection (JavaScript)

The collectors.js module extracts data without LLM overhead:

GitHub Data

• Open issues categorized by labels
• Open PRs with draft status
• Milestones with due dates
• Stale items (> 90 days inactive)
• Theme analysis from titles

Documentation Data

• Parsed README, PLAN.md, CLAUDE.md, CHANGELOG.md
• Checkbox completion counts
• Section analysis
• Feature lists

Code Data

• Directory structure
• Framework detection
• Test framework presence
• Health indicators (CI, linting, tests)

Semantic Analysis (Opus)

The plan-synthesizer receives all collected data and performs:

1. Cross-referencing: Match documented features to implementation
2. Drift identification: Find divergence patterns
3. Gap analysis: Identify what's missing
4. Prioritization: Context-aware ranking
5. Report generation: Actionable recommendations

Example Input/Output

Collected Data (from collectors.js)

{
  "github": {
    "issues": [...],
    "categorized": { "bugs": [...], "features": [...] },
    "stale": [...]
  },
  "docs": {
    "files": { "README.md": {...}, "PLAN.md": {...} },
    "checkboxes": { "total": 15, "checked": 3 }
  },
  "code": {
    "frameworks": ["Express"],
    "health": { "hasTests": true, "hasCi": true }
  }
}

Analysis Output (from plan-synthesizer)

# Reality Check Report

## Executive Summary
Project has moderate drift: 8 stale priority issues and 20% plan completion.
Strong code health (tests + CI) but documentation lags implementation.

## Drift Analysis
### Priority Neglect
**Severity**: high
8 high-priority issues inactive for 60+ days...

## Prioritized Plan
### Immediate
1. Close #45 (already implemented)
2. Update README API section...