[Bug] MsalUiRequiredException.Classification does not seem to report useful data

[zachcwillson]

Library version used

4.67.2, 4.69.1

.NET version

.Net Core 8.0.*

Scenario

PublicClient - desktop app

Is this a new or an existing app?

The app is in production, I haven't upgraded MSAL, but started seeing this issue

Issue description and reproduction steps

We observe that when we get MsalUiRequiredException, if we attempt to inspect .Classification, it always returns back as UiRequiredExceptionClassification.None.

As SubError is internal, we have no way to identify why we are hitting MsalUiRequiredException.

We see these error codes and error tags:

Error Code	Error Tag
3399614476	0x2142008D
3399614467	0x21447008
3399548929	0x1E50C30C
3399614467	0x1E50C30C
3399548929	0x1F6DD65E

But we have little understanding of why interactive auth was required.

Over the last 28 days, we have hit "None" for MsalUiRequiredException on 691 unique devices/customers

Relevant code snippets

try
{
    await publicClient.AcquireTokenSilent(scopes, PublicClientApplication.OperatingSystemAccount).ExecuteAsync(ct);
}
catch (MsalUiRequiredException e)
{
    Console.WriteLine(e.Classification);
}

Expected behavior

Either MsalUiRequiredException.Classification contains relevant data, or SubError is moved from internal to public

Identity provider

Microsoft Entra ID (Work and School accounts and Personal Microsoft accounts)

Regression

All

Solution and workarounds

None that we are aware of.

[zachcwillson]

One thing to note is we are using the Broker extension.

[bgavrilMS]

We never bridged the exception classification from interop to MSAL. So I recommend treating this as a bug.

For reference, this is the classification

microsoft-authentication-library-for-dotnet/src/client/Microsoft.Identity.Client/UiRequiredExceptionClassification.cs

Line 10 in d822a74

public enum UiRequiredExceptionClassification

and this is where it's computed if MSAL isn't using the runtime

microsoft-authentication-library-for-dotnet/src/client/Microsoft.Identity.Client/MsalUiRequiredException.cs

Line 70 in d822a74

public UiRequiredExceptionClassification Classification