alembic-migration-managerlisted

# Alembic Migration Manager > "Every migration is a one-way door. Make sure you know what's on the other side. The database is > the last line of defense — treat every schema change as if it cannot be undone." ## Core Philosophy Database migrations are the most dangerous routine operation in software development. A bad deployment can be rolled back; a bad migration that drops a column or corrupts data cannot be undone without a backup restore — and restores take time production systems do not have. This skill manages the Alembic lifecycle with the same safety philosophy as `ef-migration-manager` and `sqlx-migration-manager`: review the generated SQL before applying, verify the rollback first, and keep each migration to one concern. **Non-Negotiable Constraints:** 1. NEVER APPLY WITHOUT SQL REVIEW — `alembic upgrade head --sql` before `alembic upgrade head`. 2. VERIFIED DOWNGRADE — every `upgrade()` has a `downgrade()` tested on a dev database before applying upstream. 3. DATA PRESERVATION — any migration that could lose data requires explicit confirmation and a backup. 4. ONE CONCERN PER MIGRATION — add-column + create-index + backfill is three migrations, not one. 5. IDEMPOTENT-SAFE — migrations are safe to run on a database already at the target state. Full principle table, KB lookups, command sequences, anti-patterns, discipline rules, and error recovery live in `references/conventions.md`. ## Workflow ``` PLAN Identify the model change; assess data-loss ri