# Shadow Comparison Plan

Run:

```bash
php artisan app:release-shadow-compare
```

Shadow mode compares legacy output to modular output without double-writing or double-sending. This matters because duplicating payments, attendance records, or family messages in the name of testing is the kind of innovation nobody asked for.

## Required Comparisons

- Finance: legacy balance vs modular BalanceCalculator/read model.
- Attendance: legacy scanner result vs modular ScannerService result.
- Students: legacy creation payload vs modular DTO/identifier strategy.
- Communication: legacy recipient query vs modular preview/dedupe/preferences.
- Reporting: legacy report output vs modular read-model-backed report.

Mismatch reports must include school, scenario, legacy value, modular value, severity, and owner.