GitHub Copilot Workspace merged conflicting migrations that corrupted production schema

Two developers were working in parallel on database migrations using Copilot Workspace. Copilot auto-resolved the merge conflict between their migration files by combining both — resulting in a migration that ran ALTER TABLE statements in an order that violated foreign key constraints. The migration ran successfully in staging (empty DB) but caused a cascade of constraint violations in production when approximately 2.3 million rows failed to migrate. Database restore from backup took 6 hours of downtime.