**bleep**. Security Update (like KB5101650) breaking SmartCard Authentication for Office 2024 apps to O365

Web authentication succeeding, a new Windows profile working, and established profiles failing with AADSTS50058 isolate the problem to per-user desktop sign-in state. Microsoft defines 50058 as insufficient session information for single sign-on, while Microsoft 365 desktop apps use the per-user Web Account Manager broker. That does not by itself prove the cumulative update broke smart-card authentication. On an affected profile, first run the Microsoft 365 sign-in troubleshooter. Reproduce once and capture the Entra sign-in log’s correlation ID, timestamp, failure details, and the AppModel-State or AAD operational events. In PowerShell running as that user, check Get-AppxPackage Microsoft.AAD.BrokerPlugin. If it is missing or its Work or school account window will not open, use Microsoft’s documented Add-AppxPackage -Register repair for that system package, restart, and retest. Do not delete NTUSER.DAT or rebuild more profiles. If the failure returns after a specific KB, open a Microsoft support case with those logs and exact builds