PowerShell DSC Pullserver stops working with SQL database

Thank you for providing the additional details. Your troubleshooting is quite thorough, and the A/B comparison is especially compelling.

Since the issue is reproducible across multiple environments and replacing only Microsoft.PowerShell.DesiredStateConfiguration.Service.dll restores SQL connectivity, it appears unlikely that the problem is related to SQL Server, IIS, or the Pull Server configuration itself.

A few additional suggestions that may help narrow this down further:

• Verify that the SQL connection string is still being read correctly after installing KB5087051.
• Enable Failed Request Tracing (FREB) in IIS to capture any exceptions that may not be logged in the standard DSC or Application logs.
• Use Process Monitor (ProcMon) during a node registration attempt to determine whether the updated DLL is failing to load a dependency, access a configuration file, or read a required registry value before attempting the SQL connection.
• If possible, compare the loaded assemblies and configuration between the working (10.0.26100.1) and failing (10.0.26100.5074) versions.

Given that no SQL login attempts or sessions are observed, the failure likely occurs before the SQL client is initialized, which would also explain why no additional errors appear in the SQL Server logs.

At this point, I would recommend opening a Microsoft support case and including:

• Windows Server 2025 build number
• KB5087051
• The working and failing DLL versions
• ProcMon and FREB traces
• A minimal reproducible SQL-backed Pull Server configuration

Based on the evidence you've collected, this appears to be a strong candidate for a regression introduced by KB5087051. It will be interesting to see whether other administrators using SQL-backed DSC Pull Servers can reproduce the same behavior after installing this update.