CompatTelRunner

Microsoft says the August 2026 security update may trigger 0xc0000409 errors on Windows Server 2016 systems where the Compatibility Appraiser diagnostic service is enabled. On affected systems, users will see the CompatTelRunner.exe (Compatibility Appraiser Telemetry Runner) process crashing. Microsoft Compatibility Appraiser, which controls CompatTelRunner and is a Windows Compatibility Telemetry component, is a background system […]