Drift Baselines & Fitness Functions

Overview

Vibgrate uses baselines to track drift over time and fitness functions to enforce quality gates. Together, they enable drift governance at scale.

Storage Structure

Vibgrate stores scan state under .vibgrate/:

.vibgrate/
├── baseline.json          # Committed - reference snapshot
├── scan_result.json       # Ignored - latest scan output
└── config.ts              # Committed - configuration

Baseline Workflow

Step 1: Create Initial Baseline

# On main branch
vg baseline

Output:

✓ Scanning repository...
✓ DriftScore: 67/100
✓ Baseline saved to .vibgrate/baseline.json
→ Commit this file to version control

Step 2: Commit to Version Control

git add .vibgrate/baseline.json
git commit -m "chore: establish drift baseline"

Step 3: Enable CI Gates

vg scan \
  --baseline .vibgrate/baseline.json \
  --drift-budget 40 \
  --drift-worsening 5 \
  --fail-on error

Step 4: Refresh After Upgrades

# After completing upgrade work
vg baseline
git add .vibgrate/baseline.json
git commit -m "chore: refresh baseline after Q1 upgrades"

Fitness Functions

Fitness functions are automated quality gates that enforce drift policies:

Gate Combinations

Strict Policy Example

vg scan \
  --baseline .vibgrate/baseline.json \
  --drift-budget 30 \
  --drift-worsening 3 \
  --fail-on error

This fails if:

• 📊 Score exceeds 30 (budget gate)
• 📉 Drift increased > 3% vs baseline (regression gate)
• 🚨 Any error-level findings exist

Baseline Refresh Strategies

Gradual Tightening

Start with lenient gates and tighten over time:

# Month 1: Establish baseline only
vg baseline

# Month 2: Add budget gate
vg scan --drift-budget 60 --fail-on error

# Month 3: Add regression gate
vg scan --drift-budget 50 --drift-worsening 10 --fail-on error

# Month 6: Tighten thresholds
vg scan --drift-budget 40 --drift-worsening 5 --fail-on error

Best Practices

Related

• vg baseline — Create baselines
• DriftScore — Understanding the scoring
• CI Integration — Automated enforcement