diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index 8cd715abe..49a658bf0 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -143,11 +143,19 @@ jobs:
           $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/install.ps1))
           $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/check-release-installer.ps1))
           $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/test-check-release-installer.ps1))
+          $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/run-windows-e2e.ps1))
+          $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/test-simulate-mouse-demo.ps1))
+          $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1))
+          $null = [scriptblock]::Create((Get-Content -Raw -Encoding UTF8 scripts/test-powershell51-native-argument-escaping.ps1))
 
       - name: Test release installer smoke helper
         shell: powershell
         run: .\scripts\test-check-release-installer.ps1
 
+      - name: Test Windows PowerShell native argument escaping
+        shell: powershell
+        run: .\scripts\test-powershell51-native-argument-escaping.ps1
+
   test-unity-package:
     runs-on: ubuntu-latest
     needs: build-cli
diff --git a/Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1 b/Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1
index 81f41b813..bba73ce11 100644
--- a/Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1
+++ b/Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1
@@ -63,6 +63,32 @@ function Get-UloopArguments {
     return @($CommandArguments + @("--project-path", $ResolvedProjectPath))
 }
 
+function ConvertTo-WindowsPowerShellNativeArgument {
+    param(
+        [string]$Argument
+    )
+
+    # Windows argv rules treat backslashes specially only before a quote or the closing quote.
+    # Do not double every backslash: ordinary paths such as C:\Users must stay unchanged.
+    [string]$escapedArgument = [regex]::Replace($Argument, '(\\*)"', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes + '\"'
+    })
+
+    if ($Argument -notmatch '\s') {
+        return $escapedArgument
+    }
+
+    return [regex]::Replace($escapedArgument, '(\\*)\z', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes
+    })
+}
+
 function Invoke-UloopCapture {
     param(
         [string[]]$CommandArguments
@@ -70,8 +96,7 @@ function Invoke-UloopCapture {
 
     [string[]]$arguments = Get-UloopArguments -CommandArguments $CommandArguments
     if ($PSVersionTable.PSVersion.Major -lt 6) {
-        # Windows PowerShell strips embedded quote characters from native arguments unless they are escaped.
-        $arguments = @($arguments | ForEach-Object { $_.Replace('"', '\"') })
+        $arguments = @($arguments | ForEach-Object { ConvertTo-WindowsPowerShellNativeArgument -Argument $_ })
     }
 
     [string]$previousErrorActionPreference = $ErrorActionPreference
diff --git a/scripts/run-windows-e2e.ps1 b/scripts/run-windows-e2e.ps1
index 5664c7ac5..4d91cbc0c 100644
--- a/scripts/run-windows-e2e.ps1
+++ b/scripts/run-windows-e2e.ps1
@@ -54,6 +54,32 @@ function Get-UloopArguments {
     return $arguments
 }
 
+function ConvertTo-WindowsPowerShellNativeArgument {
+    param(
+        [string]$Argument
+    )
+
+    # Windows argv rules treat backslashes specially only before a quote or the closing quote.
+    # Do not double every backslash: ordinary paths such as C:\Users must stay unchanged.
+    [string]$escapedArgument = [regex]::Replace($Argument, '(\\*)"', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes + '\"'
+    })
+
+    if ($Argument -notmatch '\s') {
+        return $escapedArgument
+    }
+
+    return [regex]::Replace($escapedArgument, '(\\*)\z', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes
+    })
+}
+
 function Invoke-UloopCapture {
     param(
         [string[]]$CommandArguments
@@ -61,8 +87,7 @@ function Invoke-UloopCapture {
 
     [string[]]$arguments = Get-UloopArguments -CommandArguments $CommandArguments
     if ($PSVersionTable.PSVersion.Major -lt 6) {
-        # Windows PowerShell strips embedded quotes before native processes see them.
-        $arguments = @($arguments | ForEach-Object { $_.Replace('"', '\"') })
+        $arguments = @($arguments | ForEach-Object { ConvertTo-WindowsPowerShellNativeArgument -Argument $_ })
     }
 
     [string]$previousErrorActionPreference = $ErrorActionPreference
diff --git a/scripts/test-powershell51-native-argument-escaping.ps1 b/scripts/test-powershell51-native-argument-escaping.ps1
new file mode 100644
index 000000000..26965acea
--- /dev/null
+++ b/scripts/test-powershell51-native-argument-escaping.ps1
@@ -0,0 +1,104 @@
+<#
+Verifies that Windows PowerShell native argument escaping preserves backslashes
+while protecting embedded quotation marks for execute-dynamic-code requests.
+#>
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = "Stop"
+
+[string[]]$ScriptPaths = @(
+    "scripts/run-windows-e2e.ps1",
+    "scripts/test-simulate-mouse-demo.ps1",
+    "Assets/Tests/Demo/scripts/verify-replay-via-cli.ps1"
+)
+
+function Get-FunctionDefinition {
+    param(
+        [string]$ScriptPath,
+        [string]$FunctionName
+    )
+
+    [string]$source = Get-Content -LiteralPath $ScriptPath -Raw -Encoding UTF8
+    [string]$marker = "function $FunctionName"
+    [int]$start = $source.IndexOf($marker, [System.StringComparison]::Ordinal)
+    if ($start -lt 0) {
+        throw "${ScriptPath} does not define ${FunctionName}."
+    }
+
+    [int]$openBrace = $source.IndexOf("{", $start, [System.StringComparison]::Ordinal)
+    [int]$depth = 0
+    for ([int]$index = $openBrace; $index -lt $source.Length; $index++) {
+        if ($source[$index] -eq "{") {
+            $depth++
+        }
+        elseif ($source[$index] -eq "}") {
+            $depth--
+            if ($depth -eq 0) {
+                return $source.Substring($start, $index - $start + 1)
+            }
+        }
+    }
+
+    throw "${ScriptPath} has an unclosed ${FunctionName} definition."
+}
+
+function Assert-Equal {
+    param(
+        [string]$Actual,
+        [string]$Expected,
+        [string]$Context
+    )
+
+    if ($Actual -ne $Expected) {
+        throw "${Context}: expected [$Expected], actual [$Actual]."
+    }
+}
+
+function Invoke-WindowsPowerShellNativeArgumentRoundTrip {
+    param(
+        [string]$Argument
+    )
+
+    [string]$childScriptPath = Join-Path ([System.IO.Path]::GetTempPath()) ("uloop-native-argument-round-trip-" + [Guid]::NewGuid().ToString("N") + ".ps1")
+    Set-Content -LiteralPath $childScriptPath -Value '[Console]::Out.Write([Convert]::ToBase64String([Text.Encoding]::Unicode.GetBytes($args[0])))' -Encoding UTF8
+    [string[]]$childArguments = @("-NoProfile", "-File", $childScriptPath, $Argument)
+    [string[]]$escapedArguments = @($childArguments | ForEach-Object {
+        ConvertTo-WindowsPowerShellNativeArgument -Argument $_
+    })
+    [string]$encodedOutput = & powershell.exe @escapedArguments
+    if ($LASTEXITCODE -ne 0) {
+        Remove-Item -LiteralPath $childScriptPath
+        throw "Windows PowerShell native argument round trip failed."
+    }
+
+    Remove-Item -LiteralPath $childScriptPath
+    return [Text.Encoding]::Unicode.GetString([Convert]::FromBase64String($encodedOutput))
+}
+
+[string[]]$definitions = @($ScriptPaths | ForEach-Object {
+    Get-FunctionDefinition -ScriptPath $_ -FunctionName "ConvertTo-WindowsPowerShellNativeArgument"
+})
+
+foreach ($definition in @($definitions | Select-Object -Skip 1)) {
+    Assert-Equal -Actual $definition -Expected $definitions[0] -Context "All E2E scripts must use the same native argument escaping implementation"
+}
+
+[string]$temporaryFunctionPath = Join-Path ([System.IO.Path]::GetTempPath()) "uloop-native-argument-escaping.ps1"
+Set-Content -LiteralPath $temporaryFunctionPath -Value $definitions[0] -Encoding UTF8
+. $temporaryFunctionPath
+Remove-Item -LiteralPath $temporaryFunctionPath
+
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument '\"') -Expected '\\\"' -Context "Existing escaped quote"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument 'C:\Users\Example Name\') -Expected 'C:\Users\Example Name\\' -Context "Trailing backslash in quoted argument"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument '\\\"') -Expected '\\\\\\\"' -Context "Consecutive backslashes before quote"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument 'C:\Users\Example\Project') -Expected 'C:\Users\Example\Project' -Context "Ordinary Windows path"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument '日本語\パス"値') -Expected '日本語\パス\"値' -Context "Japanese text"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument 'C:\Users\Example\') -Expected 'C:\Users\Example\' -Context "Unquoted path with trailing backslash"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument '\') -Expected '\' -Context "Unquoted standalone backslash"
+Assert-Equal -Actual (ConvertTo-WindowsPowerShellNativeArgument -Argument "C:\Users\Example\`n") -Expected "C:\Users\Example\`n" -Context "Trailing backslash before line feed"
+if ($PSVersionTable.PSVersion.Major -lt 6) {
+    Assert-Equal -Actual (Invoke-WindowsPowerShellNativeArgumentRoundTrip -Argument 'C:\Users\Example\') -Expected 'C:\Users\Example\' -Context "Native process receives unquoted path with trailing backslash"
+    Assert-Equal -Actual (Invoke-WindowsPowerShellNativeArgumentRoundTrip -Argument 'C:\Users\Example Name\') -Expected 'C:\Users\Example Name\' -Context "Native process receives quoted path with trailing backslash"
+}
+
+Write-Host "PowerShell native argument escaping tests passed."
diff --git a/scripts/test-simulate-mouse-demo.ps1 b/scripts/test-simulate-mouse-demo.ps1
index c07c537b8..a4d80232d 100644
--- a/scripts/test-simulate-mouse-demo.ps1
+++ b/scripts/test-simulate-mouse-demo.ps1
@@ -34,6 +34,32 @@ function Get-UloopArguments {
     return @($CommandArguments + @("--project-path", $ProjectPath))
 }
 
+function ConvertTo-WindowsPowerShellNativeArgument {
+    param(
+        [string]$Argument
+    )
+
+    # Windows argv rules treat backslashes specially only before a quote or the closing quote.
+    # Do not double every backslash: ordinary paths such as C:\Users must stay unchanged.
+    [string]$escapedArgument = [regex]::Replace($Argument, '(\\*)"', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes + '\"'
+    })
+
+    if ($Argument -notmatch '\s') {
+        return $escapedArgument
+    }
+
+    return [regex]::Replace($escapedArgument, '(\\*)\z', {
+        param($match)
+
+        [string]$backslashes = $match.Groups[1].Value
+        return $backslashes + $backslashes
+    })
+}
+
 function Invoke-UloopCapture {
     param(
         [string[]]$CommandArguments
@@ -41,8 +67,7 @@ function Invoke-UloopCapture {
 
     [string[]]$arguments = Get-UloopArguments -CommandArguments $CommandArguments
     if ($PSVersionTable.PSVersion.Major -lt 6) {
-        # Windows PowerShell strips embedded quote characters from native arguments unless they are escaped.
-        $arguments = @($arguments | ForEach-Object { $_.Replace('"', '\"') })
+        $arguments = @($arguments | ForEach-Object { ConvertTo-WindowsPowerShellNativeArgument -Argument $_ })
     }
 
     [string]$previousErrorActionPreference = $ErrorActionPreference