DbContext.Entry().Reference().Load() falsely tracks existing reference entity as Added

[Ben555555]

Bug description

When I execute the following code, there will be an exception when saving the changes, because EF tries to save an entity that already exists:

Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
 ---> Microsoft.Data.SqlClient.SqlException (0x80131904): Violation of PRIMARY KEY constraint 'PK_Municipalities'. Cannot insert duplicate key in object 'dbo.Municipalities'. The duplicate key value is (1).

Your code

var childResidenceEntity = new
{
MunicipalityId = 1
};

await dbContext.Entry(childResidenceEntity)
    .Reference(childResidence => childResidence.Municipality)
    .LoadAsync(cancellationToken);

await dbContext.SaveChangesAsync(cancellationToken);

The only workaround is to change the state before saving:

dbContext.Entry(childResidenceEntity.Municipality!).State = EntityState.Unchanged;

Is this behaviour by the design (which I would not understand why)?

Stack traces

Verbose output

EF Core version

8.1.5

Database provider

SqlServer

Target framework

.NE 8

Operating system

Windows 11

IDE

Visual Studio 2022