# AGENTS.md (Data / Schema)

## Data Integrity Rules

- Use explicit primary keys and foreign keys
- Enforce referential integrity at the database level
- Ensure migrations are reversible when possible

## Domain Logic Constraints

- **Currency**: Use fixed-precision decimals (no floats)
- **Time**: Store timestamps in UTC, convert at the edge
- **Identifiers**: Use stable, non-recycled IDs

## No-Delete Policy

- Prefer soft deletes for domain entities
- Require audit trail for destructive operations
- Disallow hard deletes except for ephemeral or test data

## Schema Change Workflow

1. Write a spec for the change
2. Add migration with forward + backward steps
3. Update data documentation and examples
4. Validate with integration tests

## Validation Checklist

- [ ] Foreign keys defined
- [ ] Indexes match query patterns
- [ ] Defaults and nullability are explicit
- [ ] Backfill plan documented