diff --git a/scripts/bootstrap.ps1 b/scripts/bootstrap.ps1
index 42ece2abb7..311b32c37c 100755
--- a/scripts/bootstrap.ps1
+++ b/scripts/bootstrap.ps1
@@ -20,8 +20,9 @@ param (
 $ErrorActionPreference = "Stop"
 Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force
 
-$script:IsARM64 = $env:PROCESSOR_ARCHITECTURE -eq "ARM64"
-Write-Output "PROCESSOR_ARCHITECTURE=$env:PROCESSOR_ARCHITECTURE IsARM64=$script:IsARM64"
+# Use registry for ARM64 detection — $env:PROCESSOR_ARCHITECTURE reports AMD64
+# under x64 emulation (Azure Run Command uses x64 PowerShell on ARM64 VMs)
+$script:IsARM64 = (Get-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\Environment').PROCESSOR_ARCHITECTURE -eq "ARM64"
 
 # ============================================================================
 # Utility functions
@@ -234,7 +235,6 @@ function Install-7zip {
     return
   }
 
-  Write-Output "DEBUG: PROCESSOR_ARCHITECTURE=$env:PROCESSOR_ARCHITECTURE IsARM64=$script:IsARM64"
   if ($script:IsARM64) {
     # Scoop's 7zip ARM64 post_install has a Remove-Item error that kills bootstrap.
     # Install manually instead.