A deep dive into using EF Core's `ExcludeFromMigrations()` to build plugin-based systems where each plugin owns its own database schema and migration timeline. Covers the three-layer architecture: host context excludes plugin tables while retaining query capability, plugin context owns its schema with isolated migration history tables, and the application layer handles cross-context data loading. Key gotchas include the FK navigation property bug (GitHub issue #23639) that causes spurious DROP/ADD FK operations, the need for `IDesignTimeDbContextFactory` per plugin, `MigrationsHistoryTable` isolation to prevent collision, and correct startup migration ordering. Also covers integration testing patterns and when to choose this pattern versus a unified context.
