fix: use basic parsing for Windows installer downloads

.antigravity-plugin/scripts/ensure-monk-agent.ps1

@@ -162,7 +162,7 @@ try {
     $InstallerMutexOwned = $true
   }
 
-  Invoke-WebRequest -Uri $ChecksumUrl -OutFile $ChecksumTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $ChecksumUrl -OutFile $ChecksumTmp
 
   $Expected = ((Get-Content -Raw $ChecksumTmp).Trim() -split "\s+")[0].ToLowerInvariant()
 
@@ -176,7 +176,7 @@ try {
   }
 
   Write-Host "Installing monk-agent from $Url"
-  Invoke-WebRequest -Uri $Url -OutFile $ArchiveTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $Url -OutFile $ArchiveTmp
 
   $Actual = Get-FileSha256 $ArchiveTmp
   if ($Actual -ne $Expected) {

.github/workflows/install-e2e.yml

@@ -78,6 +78,10 @@ jobs:
         shell: pwsh
         run: .\tests\block-monk-windows.ps1
 
+      - name: Test Windows PowerShell 5.1 installer downloads
+        shell: pwsh
+        run: .\tests\ensure-monk-agent-basic-parsing.ps1
+
       - name: Check launcher readiness deadline
         shell: pwsh
         run: .\tests\start-monk-agent-readiness-timeout.ps1

plugins/monk/scripts/ensure-monk-agent.ps1

@@ -162,7 +162,7 @@ try {
     $InstallerMutexOwned = $true
   }
 
-  Invoke-WebRequest -Uri $ChecksumUrl -OutFile $ChecksumTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $ChecksumUrl -OutFile $ChecksumTmp
 
   $Expected = ((Get-Content -Raw $ChecksumTmp).Trim() -split "\s+")[0].ToLowerInvariant()
 
@@ -176,7 +176,7 @@ try {
   }
 
   Write-Host "Installing monk-agent from $Url"
-  Invoke-WebRequest -Uri $Url -OutFile $ArchiveTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $Url -OutFile $ArchiveTmp
 
   $Actual = Get-FileSha256 $ArchiveTmp
   if ($Actual -ne $Expected) {

scripts/ensure-monk-agent.ps1

@@ -162,7 +162,7 @@ try {
     $InstallerMutexOwned = $true
   }
 
-  Invoke-WebRequest -Uri $ChecksumUrl -OutFile $ChecksumTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $ChecksumUrl -OutFile $ChecksumTmp
 
   $Expected = ((Get-Content -Raw $ChecksumTmp).Trim() -split "\s+")[0].ToLowerInvariant()
 
@@ -176,7 +176,7 @@ try {
   }
 
   Write-Host "Installing monk-agent from $Url"
-  Invoke-WebRequest -Uri $Url -OutFile $ArchiveTmp
+  Invoke-WebRequest -UseBasicParsing -Uri $Url -OutFile $ArchiveTmp
 
   $Actual = Get-FileSha256 $ArchiveTmp
   if ($Actual -ne $Expected) {

tests/ensure-monk-agent-basic-parsing.ps1

@@ -0,0 +1,112 @@
+$ErrorActionPreference = "Stop"
+
+# Windows PowerShell 5.1 falls back to the Internet Explorer parser unless
+# Invoke-WebRequest receives -UseBasicParsing. Exercise the real installer with
+# deterministic local archive/checksum fixtures and a cmdlet shim that models
+# the documented headless-host failure.
+
+$Repo = Split-Path -Parent (Split-Path -Parent $MyInvocation.MyCommand.Path)
+$Root = Join-Path ([IO.Path]::GetTempPath()) ("monk-basic-parsing-" + [guid]::NewGuid().ToString("N"))
+$PayloadDir = Join-Path $Root "payload"
+$ArchivePath = Join-Path $Root "monk-agent.zip"
+$ChecksumPath = Join-Path $Root "monk-agent.zip.sha256"
+$InstallDir = Join-Path $Root "install"
+$MonkHome = Join-Path $Root "home"
+$ShimPath = Join-Path $Root "invoke-installer.ps1"
+$DownloadLog = Join-Path $Root "downloads.log"
+$InstallerPath = Join-Path $Repo "scripts\ensure-monk-agent.ps1"
+$WindowsPowerShell = Join-Path $env:SystemRoot "System32\WindowsPowerShell\v1.0\powershell.exe"
+
+$EnvironmentNames = @(
+  "MONK_AGENT_INSTALL_DIR",
+  "MONK_AGENT_HOME",
+  "MONK_AGENT_DOWNLOAD_BASE",
+  "MONK_AGENT_AUTO_UPDATE",
+  "MONK_TEST_ARCHIVE",
+  "MONK_TEST_CHECKSUM",
+  "MONK_TEST_DOWNLOAD_LOG",
+  "MONK_TEST_INSTALLER"
+)
+$OriginalEnvironment = @{}
+foreach ($Name in $EnvironmentNames) {
+  $OriginalEnvironment[$Name] = [Environment]::GetEnvironmentVariable($Name, "Process")
+}
+
+try {
+  New-Item -ItemType Directory -Force -Path $PayloadDir | Out-Null
+  "fixture-agent" | Set-Content -NoNewline (Join-Path $PayloadDir "monk-agent.exe")
+  Compress-Archive -Path (Join-Path $PayloadDir "monk-agent.exe") -DestinationPath $ArchivePath
+  $Hash = (Get-FileHash -Algorithm SHA256 $ArchivePath).Hash.ToLowerInvariant()
+  "$Hash  monk-agent-windows-latest.zip" | Set-Content -NoNewline $ChecksumPath
+
+  @'
+$ErrorActionPreference = "Stop"
+function Invoke-WebRequest {
+  [CmdletBinding()]
+  param(
+    [string]$Uri,
+    [string]$OutFile,
+    [switch]$UseBasicParsing
+  )
+
+  if (-not $UseBasicParsing) {
+    throw "The response content cannot be parsed because the Internet Explorer engine is not available."
+  }
+
+  if ($Uri.EndsWith(".sha256")) {
+    Copy-Item -Force $env:MONK_TEST_CHECKSUM $OutFile
+  } else {
+    Copy-Item -Force $env:MONK_TEST_ARCHIVE $OutFile
+  }
+  "basic=$($UseBasicParsing.IsPresent) uri=$Uri" | Add-Content $env:MONK_TEST_DOWNLOAD_LOG
+}
+
+. $env:MONK_TEST_INSTALLER
+'@ | Set-Content -NoNewline $ShimPath
+
+  $env:MONK_AGENT_INSTALL_DIR = $InstallDir
+  $env:MONK_AGENT_HOME = $MonkHome
+  $env:MONK_AGENT_DOWNLOAD_BASE = "https://fixture.invalid"
+  $env:MONK_AGENT_AUTO_UPDATE = "1"
+  $env:MONK_TEST_ARCHIVE = $ArchivePath
+  $env:MONK_TEST_CHECKSUM = $ChecksumPath
+  $env:MONK_TEST_DOWNLOAD_LOG = $DownloadLog
+  $env:MONK_TEST_INSTALLER = $InstallerPath
+
+  $Output = & $WindowsPowerShell -NoLogo -NoProfile -ExecutionPolicy Bypass -File $ShimPath 2>&1
+  if ($LASTEXITCODE -ne 0) {
+    throw "installer exited $LASTEXITCODE`: $Output"
+  }
+
+  $InstalledAgent = Join-Path $InstallDir "monk-agent.exe"
+  if (-not (Test-Path $InstalledAgent)) {
+    throw "installer did not extract monk-agent.exe"
+  }
+  if ((Get-Content -Raw $InstalledAgent) -ne "fixture-agent") {
+    throw "installed fixture content changed"
+  }
+
+  $Downloads = @(Get-Content $DownloadLog)
+  if ($Downloads.Count -ne 2 -or @($Downloads | Where-Object { $_ -notmatch "^basic=True " }).Count -ne 0) {
+    throw "expected two basic-parsing downloads, got: $($Downloads -join '; ')"
+  }
+
+  $ShippedCopies = @(
+    ".antigravity-plugin\scripts\ensure-monk-agent.ps1",
+    "plugins\monk\scripts\ensure-monk-agent.ps1"
+  )
+  $ExpectedHash = (Get-FileHash -Algorithm SHA256 $InstallerPath).Hash
+  foreach ($RelativePath in $ShippedCopies) {
+    $CopyHash = (Get-FileHash -Algorithm SHA256 (Join-Path $Repo $RelativePath)).Hash
+    if ($CopyHash -ne $ExpectedHash) {
+      throw "generated PowerShell installer differs: $RelativePath"
+    }
+  }
+
+  Write-Host "ensure_basic_parsing_status=pass downloads=$($Downloads.Count)"
+} finally {
+  foreach ($Name in $EnvironmentNames) {
+    [Environment]::SetEnvironmentVariable($Name, $OriginalEnvironment[$Name], "Process")
+  }
+  Remove-Item -LiteralPath $Root -Recurse -Force -ErrorAction SilentlyContinue
+}