diff --git a/scripts/external-review-pack.ps1 b/scripts/external-review-pack.ps1
index c465c2f8..b3cd839b 100644
--- a/scripts/external-review-pack.ps1
+++ b/scripts/external-review-pack.ps1
@@ -6,30 +6,47 @@ param(
 
 $ErrorActionPreference = "Stop"
 
+function Assert-ExternalReviewDateStamp {
+    <#
+    .SYNOPSIS
+      Reject DateStamp values that are not YYYY-MM-DD (#1192).
+    #>
+    param(
+        [Parameter(Mandatory = $true)]
+        [string]$Value
+    )
+    if ($Value -notmatch '^\d{4}-\d{2}-\d{2}$') {
+        throw "Invalid -DateStamp '$Value' - expected YYYY-MM-DD."
+    }
+}
+
 if ([string]::IsNullOrWhiteSpace($DateStamp)) {
     $DateStamp = (Get-Date).ToString("yyyy-MM-dd")
 }
 
+Assert-ExternalReviewDateStamp -Value $DateStamp
+
 $bundlePath = "docs/private/gemini_bundles/public_bundle_$DateStamp.txt"
 
 Write-Host "=== External review pack ==="
 Write-Host "Bundle date: $DateStamp"
 Write-Host ""
 
-$cmd = @(
-    "uv run python scripts/export_public_gemini_bundle.py",
-    "--output `"$bundlePath`"",
+$argv = @(
+    "run",
+    "python",
+    "scripts/export_public_gemini_bundle.py",
+    "--output", $bundlePath,
     "--compliance-yaml",
     "--verify"
 )
 
-if ($IncludePlans) { $cmd += "--plans" }
-if ($IncludeCursor) { $cmd += "--cursor" }
+if ($IncludePlans) { $argv += "--plans" }
+if ($IncludeCursor) { $argv += "--cursor" }
 
-$joined = $cmd -join " "
 Write-Host "[1/3] Building Gemini bundle"
-Write-Host $joined
-Invoke-Expression $joined
+Write-Host "uv $($argv -join ' ')"
+& uv @argv
 if ($LASTEXITCODE -ne 0) {
     throw "Bundle generation/verification failed (exit code $LASTEXITCODE)."
 }
diff --git a/tests/pester/ExternalReviewPack.Tests.ps1 b/tests/pester/ExternalReviewPack.Tests.ps1
new file mode 100644
index 00000000..559a1101
--- /dev/null
+++ b/tests/pester/ExternalReviewPack.Tests.ps1
@@ -0,0 +1,37 @@
+BeforeAll {
+    . (Join-Path $PSScriptRoot '_RepoRoot.ps1')
+    $script:PackScript = Get-RepoScript 'scripts/external-review-pack.ps1'
+}
+
+Describe 'external-review-pack.ps1 (#1192)' {
+    It 'does not use Invoke-Expression; validates DateStamp and calls uv via splat' {
+        $raw = Get-ScriptRaw 'scripts/external-review-pack.ps1'
+        $raw | Should -Not -Match 'Invoke-Expression'
+        $raw | Should -Match '& uv @argv'
+        $raw | Should -Match 'Assert-ExternalReviewDateStamp'
+        $raw | Should -Match ([regex]::Escape('^\d{4}-\d{2}-\d{2}$'))
+    }
+
+    It 'Accepts a valid YYYY-MM-DD DateStamp (regex guard)' {
+        # Mirror Assert-ExternalReviewDateStamp — valid path only; avoid running uv/bundle.
+        $Value = '2026-07-15'
+        { if ($Value -notmatch '^\d{4}-\d{2}-\d{2}$') {
+                throw "Invalid -DateStamp '$Value' - expected YYYY-MM-DD."
+            }
+        } | Should -Not -Throw
+    }
+
+    It 'Throws on injection-shaped DateStamp before calling uv' {
+        $bad = '2026-01-01"; evil'
+        { & $script:PackScript -DateStamp $bad } | Should -Throw -Because 'injection must fail closed before & uv'
+    }
+
+    It 'Throws on non-date DateStamp before calling uv' {
+        { & $script:PackScript -DateStamp 'abc' } | Should -Throw
+    }
+
+    It 'Throw message names YYYY-MM-DD for invalid DateStamp' {
+        { & $script:PackScript -DateStamp 'not-a-date' } |
+            Should -Throw -ExpectedMessage '*YYYY-MM-DD*'
+    }
+}