diff --git a/.github/scripts/setup-dev-drive.ps1 b/.github/scripts/setup-dev-drive.ps1
index 26ca58b837..48eb78f952 100644
--- a/.github/scripts/setup-dev-drive.ps1
+++ b/.github/scripts/setup-dev-drive.ps1
@@ -1,14 +1,19 @@
-# Configure a fast drive for Windows CI jobs.
+# Configure a Dev Drive for Windows CI jobs.
 #
-# GitHub-hosted Windows runners do not always expose a secondary D: volume. When
-# they do not, try to create a Dev Drive VHD and fall back to C: if the runner
-# image does not allow that provisioning path.
+# Try to create a Dev Drive VHD explicitly so Windows temp-heavy paths can use a
+# trusted ReFS Dev Drive. Fall back to the runner-provided D: drive, then C:, if
+# the runner image does not allow that provisioning path.
 
-function Use-FallbackDrive {
+function Select-FallbackDrive {
     param([string]$Reason)
 
-    Write-Warning "$Reason Falling back to C:"
-    return "C:"
+    if (Test-Path "D:\") {
+        Write-Warning "$Reason Falling back to existing drive at D:"
+        return "D:"
+    } else {
+        Write-Warning "$Reason Falling back to C:"
+        return "C:"
+    }
 }
 
 function Invoke-BestEffort {
@@ -21,44 +26,40 @@ function Invoke-BestEffort {
     }
 }
 
-if (Test-Path "D:\") {
-    Write-Output "Using existing drive at D:"
-    $Drive = "D:"
-} else {
-    try {
-        $VhdPath = Join-Path $env:RUNNER_TEMP "codex-dev-drive.vhdx"
-        $SizeBytes = 64GB
+try {
+    $VhdPath = Join-Path $env:RUNNER_TEMP "codex-dev-drive.vhdx"
+    $SizeBytes = 64GB
 
-        if (Test-Path $VhdPath) {
-            Remove-Item -Path $VhdPath -Force
-        }
-
-        New-VHD -Path $VhdPath -SizeBytes $SizeBytes -Dynamic -ErrorAction Stop | Out-Null
-        $Mounted = Mount-VHD -Path $VhdPath -Passthru -ErrorAction Stop
-        $Disk = $Mounted | Get-Disk -ErrorAction Stop
-        $Disk | Initialize-Disk -PartitionStyle GPT -ErrorAction Stop
-        $Partition = $Disk | New-Partition -AssignDriveLetter -UseMaximumSize -ErrorAction Stop
-        $Volume = $Partition | Format-Volume -FileSystem ReFS -NewFileSystemLabel "CodexDevDrive" -DevDrive -Confirm:$false -Force -ErrorAction Stop
-
-        $Drive = "$($Volume.DriveLetter):"
-
-        Invoke-BestEffort { fsutil devdrv trust $Drive } "Trusting Dev Drive $Drive"
-        Invoke-BestEffort { fsutil devdrv enable /disallowAv } "Disabling AV filter attachment for Dev Drives"
-        try {
-            Dismount-VHD -Path $VhdPath
-            Mount-VHD -Path $VhdPath | Out-Null
-        } catch {
-            Write-Warning "Remounting Dev Drive $Drive failed: $($_.Exception.Message)"
-            if (-not (Test-Path "$Drive\")) {
-                throw
-            }
-        }
-        Invoke-BestEffort { fsutil devdrv query $Drive } "Querying Dev Drive $Drive"
-
-        Write-Output "Using Dev Drive at $Drive"
-    } catch {
-        $Drive = Use-FallbackDrive "Failed to create Dev Drive: $($_.Exception.Message)"
+    if (Test-Path $VhdPath) {
+        Remove-Item -Path $VhdPath -Force
     }
+
+    New-VHD -Path $VhdPath -SizeBytes $SizeBytes -Dynamic -ErrorAction Stop | Out-Null
+    $Mounted = Mount-VHD -Path $VhdPath -Passthru -ErrorAction Stop
+    $Disk = $Mounted | Get-Disk -ErrorAction Stop
+    $Disk | Initialize-Disk -PartitionStyle GPT -ErrorAction Stop
+    $Partition = $Disk | New-Partition -AssignDriveLetter -UseMaximumSize -ErrorAction Stop
+    $Volume = $Partition | Format-Volume -FileSystem ReFS -NewFileSystemLabel "CodexDevDrive" -DevDrive -Confirm:$false -Force -ErrorAction Stop
+
+    $Drive = "$($Volume.DriveLetter):"
+
+    Invoke-BestEffort { fsutil devdrv trust $Drive } "Trusting Dev Drive $Drive"
+    Invoke-BestEffort { fsutil devdrv enable /disallowAv } "Disabling AV filter attachment for Dev Drives"
+    try {
+        Dismount-VHD -Path $VhdPath
+        Mount-VHD -Path $VhdPath | Out-Null
+    } catch {
+        Write-Warning "Remounting Dev Drive $Drive failed: $($_.Exception.Message)"
+        if (-not (Test-Path "$Drive\")) {
+            throw
+        }
+    }
+    Invoke-BestEffort { fsutil devdrv query $Drive } "Querying Dev Drive $Drive"
+
+    Write-Output "Using Dev Drive at $Drive"
+} catch {
+    $Drive = Select-FallbackDrive "Failed to create Dev Drive: $($_.Exception.Message)"
+    Invoke-BestEffort { fsutil devdrv query $Drive } "Querying fallback drive $Drive"
 }
 
 $Tmp = "$Drive\codex-tmp"