diff --git a/.github/workflows/studio-windows-inference-smoke.yml b/.github/workflows/studio-windows-inference-smoke.yml
index 3ebe442f52..b3badef02b 100644
--- a/.github/workflows/studio-windows-inference-smoke.yml
+++ b/.github/workflows/studio-windows-inference-smoke.yml
@@ -1888,8 +1888,11 @@ jobs:
           # (step/substep -> Write-StudioStdoutMirror / Get-StudioAnsi).
           $script:StudioVtOk = $false
           $script:UnslothVerbose = $false
+          # Get-HostMachineArch is reached only on the absent path, where
+          # Test-VCRedistInstalled consults it before trusting the System32 DLL, so
+          # part A passes without it and only the clean-box part fails.
           foreach ($fn in @('Get-StudioAnsi', 'Write-StudioStdoutMirror', 'step', 'substep',
-                            'Invoke-SetupCommand', 'Refresh-Environment',
+                            'Invoke-SetupCommand', 'Refresh-Environment', 'Get-HostMachineArch',
                             'Test-VCRedistInstalled', 'Ensure-VCRedist')) {
               $src = Get-FunctionSource -Path $setup -Name $fn
               if (-not $src) { throw "Function '$fn' not found in setup.ps1" }