We Built Multi-Tenancy Into a Blazor App. Here's Every Layer Preventing Data Leaks.

After a data leak incident in a multi-tenant Blazor app caused by a missing query filter, the team rebuilt the entire multi-tenancy layer with four isolation layers: middleware-based tenant resolution, EF Core global query filters, SaveChanges tenant stamping, and JWT claim validation. The architecture ensures no single point of failure by using a priority chain (JWT claims, headers, domain) for tenant resolution and AsyncLocal-based TenantContext, all built into the BlazorBluePrint template.