<PackageReference Include="Microsoft.Identity.Client" Version="4.85.0" />

Microsoft.Identity.Client.OAuth2.OAuth2Error

static class OAuth2Error
OAuth2 errors that are only used internally. All error codes used when propagating exceptions should be made public.
namespace Microsoft.Identity.Client.OAuth2 { internal static class OAuth2Error { public const string LoginRequired = "login_required"; public const string AuthorizationPending = "authorization_pending"; } }