Here's a failure I've now watched happen on three different teams.

Two people branch off main. Alice adds 0007_add_index.up.sql. Bob adds

0007_add_orders_fk.up.sql. Both PRs pass CI in isolation — of course they do,

each migration is fine on its own. Both merge. Now main has two migrations

claiming version 0007, and depending on which migration tool you use, the