diff --git a/build/WindowsSigning.Tests.ps1 b/build/WindowsSigning.Tests.ps1
index 8952864..9f46998 100644
--- a/build/WindowsSigning.Tests.ps1
+++ b/build/WindowsSigning.Tests.ps1
@@ -18,8 +18,8 @@ Describe 'Owned binary catalog' `
       New-Item -ItemType Directory -Path $script:Root | Out-Null
       $script:Catalog = Join-Path $script:Root 'catalog.txt'
       $script:Manifest = Join-Path $script:Root 'manifest.json'
-      Set-Content -LiteralPath (Join-Path $script:Root 'Owned.dll') -Value 'owned'
-      Set-Content -LiteralPath (Join-Path $script:Root 'Microsoft.dll') -Value 'third-party'
+      Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $script:Root 'Owned.dll')
+      Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $script:Root 'Microsoft.dll')
    }
 
    It 'includes only explicit owned names and inventories other binaries' `
@@ -51,6 +51,34 @@ Describe 'Owned binary catalog' `
       Test-Path -LiteralPath $script:Catalog | Should -BeFalse
       Test-Path -LiteralPath $script:Manifest | Should -BeFalse
    }
+
+   It 'rejects malformed owned PE input before writing a catalog' `
+   {
+      [IO.File]::WriteAllBytes((Join-Path $script:Root 'Owned.dll'), [byte[]]::new(128))
+      { New-WindowsSigningCatalog -Root $script:Root -Patterns @('Owned.dll') -CatalogPath $script:Catalog -ManifestPath $script:Manifest } | Should -Throw '*Invalid published PE binary: Owned.dll*'
+      Test-Path -LiteralPath $script:Catalog | Should -BeFalse
+   }
+
+   It 'rejects an already malformed preserved dependency' `
+   {
+      [IO.File]::WriteAllBytes((Join-Path $script:Root 'Microsoft.dll'), [byte[]]::new(128))
+      { New-WindowsSigningCatalog -Root $script:Root -Patterns @('Owned.dll') -CatalogPath $script:Catalog -ManifestPath $script:Manifest -PreserveOtherBinaries } | Should -Throw '*Invalid published PE binary: Microsoft.dll*'
+      Test-Path -LiteralPath $script:Manifest | Should -BeFalse
+   }
+
+   It 'does not treat package-format signing targets as PE images' `
+   {
+      Set-Content -LiteralPath (Join-Path $script:Root 'Setup.msi') -Value 'package fixture; signature validation is a later gate'
+      { New-WindowsSigningCatalog -Root $script:Root -Patterns @('Setup.msi') -CatalogPath $script:Catalog -ManifestPath $script:Manifest } | Should -Not -Throw
+      Get-Content -LiteralPath $script:Catalog | Should -Be 'Setup.msi'
+   }
+
+   It 'ignores excluded binaries when dependency preservation is disabled' `
+   {
+      [IO.File]::WriteAllBytes((Join-Path $script:Root 'Microsoft.dll'), [byte[]]::new(128))
+      { New-WindowsSigningCatalog -Root $script:Root -Patterns @('Owned.dll') -CatalogPath $script:Catalog -ManifestPath $script:Manifest } | Should -Not -Throw
+      @(Get-Content -LiteralPath $script:Manifest -Raw | ConvertFrom-Json) | Should -HaveCount 1
+   }
 }
 
 Describe 'Signature and distributed-byte gates' `
@@ -126,8 +154,8 @@ Describe 'Signature and distributed-byte gates' `
       {
          $root = Join-Path $TestDrive 'preserve'
          New-Item -ItemType Directory -Path $root | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'owned'
-         Set-Content -LiteralPath (Join-Path $root 'Microsoft.dll') -Value 'third-party'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Microsoft.dll')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest -PreserveOtherBinaries
          Set-Content -LiteralPath (Join-Path $root 'Microsoft.dll') -Value 'modified'
@@ -138,7 +166,7 @@ Describe 'Signature and distributed-byte gates' `
       {
          $root = Join-Path $TestDrive 'other-publisher'
          New-Item -ItemType Directory -Path $root | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'already signed'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
          $script:ProbeSignature.SignerCertificate.SubjectName.Name = 'CN=Other Publisher'
          { New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath (Join-Path $root 'manifest.json') -ExpectedSubject 'CN=Verified Publisher' } | Should -Throw '*another publisher*'
          Test-Path -LiteralPath (Join-Path $root 'catalog.txt') | Should -BeFalse
@@ -150,7 +178,7 @@ Describe 'Signature and distributed-byte gates' `
          $assets = Join-Path $root 'assets'
          $packed = Join-Path $root 'packed'
          New-Item -ItemType Directory -Path $root, $assets, $packed | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'signed bytes'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest
          Set-Content -LiteralPath (Join-Path $packed 'Owned.dll') -Value 'modified after signing'
@@ -164,7 +192,7 @@ Describe 'Signature and distributed-byte gates' `
          $assets = Join-Path $root 'assets'
          $packed = Join-Path $root 'packed'
          New-Item -ItemType Directory -Path $root, $assets, $packed | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'signed bytes'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest
          Set-Content -LiteralPath (Join-Path $packed 'README.txt') -Value 'no binary'
@@ -184,8 +212,8 @@ Describe 'Signature and distributed-byte gates' `
          $assets = Join-Path $root 'assets'
          $packed = Join-Path $root 'packed'
          New-Item -ItemType Directory -Path "$publish/$Head", $assets, $packed | Out-Null
-         Set-Content -LiteralPath "$publish/$Head/Owned.dll" -Value 'signed app'
-         Set-Content -LiteralPath "$publish/$Head/Microsoft.dll" -Value 'third-party'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/$Head/Owned.dll"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/$Head/Microsoft.dll"
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $publish -Patterns @("$Head/Owned.dll") -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest -PreserveOtherBinaries
          Copy-Item -LiteralPath "$publish/$Head/Owned.dll" -Destination $packed
@@ -200,10 +228,10 @@ Describe 'Signature and distributed-byte gates' `
          $assets = Join-Path $root 'assets'
          $packed = Join-Path $root 'packed'
          New-Item -ItemType Directory -Path "$publish/app", $assets, $packed | Out-Null
-         Set-Content -LiteralPath "$publish/app/Owned.dll" -Value 'signed app'
-         Set-Content -LiteralPath "$publish/app/Microsoft.dll" -Value 'third-party'
-         Set-Content -LiteralPath "$publish/app/createdump.exe" -Value 'excluded helper'
-         Set-Content -LiteralPath "$publish/app/Owned.vshost.exe" -Value 'excluded host'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Owned.dll"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Microsoft.dll"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/createdump.exe"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Owned.vshost.exe"
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $publish -Patterns @('app/Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest -PreserveOtherBinaries
          Copy-Item -LiteralPath "$publish/app/Owned.dll", "$publish/app/Microsoft.dll" -Destination $packed
@@ -218,8 +246,8 @@ Describe 'Signature and distributed-byte gates' `
          $assets = Join-Path $root 'assets'
          $packed = Join-Path $root 'packed'
          New-Item -ItemType Directory -Path "$publish/app", $assets, $packed | Out-Null
-         Set-Content -LiteralPath "$publish/app/Owned.dll" -Value 'signed app'
-         Set-Content -LiteralPath "$publish/app/Microsoft.dll" -Value 'third-party'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Owned.dll"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Microsoft.dll"
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $publish -Patterns @('app/Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest -PreserveOtherBinaries
          Copy-Item -LiteralPath "$publish/app/Owned.dll" -Destination $packed
@@ -233,7 +261,7 @@ Describe 'Signature and distributed-byte gates' `
          $root = Join-Path $TestDrive 'valid'
          $assets = Join-Path $root 'assets'
          New-Item -ItemType Directory -Path $root, $assets | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'signed bytes'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest
          $packed = Join-Path $root 'packed'
@@ -248,8 +276,8 @@ Describe 'Signature and distributed-byte gates' `
          $root = Join-Path $TestDrive 'prefix'
          $assets = Join-Path $root 'assets'
          New-Item -ItemType Directory -Path $root, $assets | Out-Null
-         Set-Content -LiteralPath (Join-Path $root 'Owned.dll') -Value 'signed core'
-         Set-Content -LiteralPath (Join-Path $root 'Owned.Adapter.dll') -Value 'signed adapter'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.dll')
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination (Join-Path $root 'Owned.Adapter.dll')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $root -Patterns @('Owned.dll', 'Owned.Adapter.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest
          foreach($name in @('Owned', 'Owned.Adapter'))
@@ -268,9 +296,11 @@ Describe 'Signature and distributed-byte gates' `
          $publish = Join-Path $root 'publish'
          $assets = Join-Path $root 'assets'
          New-Item -ItemType Directory -Path $assets, "$publish/app/en", "$publish/app/fr" | Out-Null
-         Set-Content -LiteralPath "$publish/app/Owned.dll" -Value 'signed app'
-         Set-Content -LiteralPath "$publish/app/en/Library.resources.dll" -Value 'English'
-         Set-Content -LiteralPath "$publish/app/fr/Library.resources.dll" -Value 'French'
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/Owned.dll"
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/en/Library.resources.dll"
+         [IO.File]::AppendAllText("$publish/app/en/Library.resources.dll", 'English')
+         Copy-Item -LiteralPath ([Reflection.PortableExecutable.PEReader].Assembly.Location) -Destination "$publish/app/fr/Library.resources.dll"
+         [IO.File]::AppendAllText("$publish/app/fr/Library.resources.dll", 'French')
          $manifest = Join-Path $root 'manifest.json'
          New-WindowsSigningCatalog -Root $publish -Patterns @('app/Owned.dll') -CatalogPath (Join-Path $root 'catalog.txt') -ManifestPath $manifest -PreserveOtherBinaries
          [IO.Compression.ZipFile]::CreateFromDirectory("$publish/app", (Join-Path $assets 'Owned-Portable.zip'))
diff --git a/build/WindowsSigning.psm1 b/build/WindowsSigning.psm1
index fcb69a5..4f070b5 100644
--- a/build/WindowsSigning.psm1
+++ b/build/WindowsSigning.psm1
@@ -70,6 +70,21 @@ function New-WindowsSigningCatalog
          $null = $owned.Add($file.FullName)
       }
    }
+   foreach($file in $binaries | Where-Object { ($PreserveOtherBinaries -or $owned.Contains($_.FullName)) -and $_.Extension -in '.exe', '.dll' })
+   {
+      $stream = [IO.File]::OpenRead($file.FullName)
+      try
+      {
+         $reader = [Reflection.PortableExecutable.PEReader]::new($stream)
+         try
+         {
+            if($null -eq $reader.PEHeaders.PEHeader) { throw 'Missing executable header.' }
+         }
+         finally { $reader.Dispose() }
+      }
+      catch { throw "Invalid published PE binary: $($file.Name). $($_.Exception.Message)" }
+      finally { $stream.Dispose() }
+   }
    $entries = @($binaries | Where-Object { $PreserveOtherBinaries -or $owned.Contains($_.FullName) } | ForEach-Object {
          [ordered]@{
             path         = $_.FullName
diff --git a/docs/release-signing.md b/docs/release-signing.md
index 284883a..f7df6c4 100644
--- a/docs/release-signing.md
+++ b/docs/release-signing.md
@@ -154,7 +154,10 @@ The Velopack builder accepts required owned names or publish-relative patterns.
 For the starter's CLI variant, the catalog includes `app/Kof22App.exe`,
 `app/Kof22App.dll`, `app/Kof22App.Core.dll`, the three consumed AppKit DLLs and
 `cli/kof22-app.exe`; adapt these to the generated names. The no-CLI variant omits
-the last entry. Preserve all other binary bytes and signatures. The packaging hook
+the last entry. Preserve all other binary bytes and signatures. The catalog gate
+rejects malformed owned or preserved `.exe`/`.dll` inputs before catalog creation;
+unchanged hashes alone cannot prove that the source was executable. MSI/MSIX follow
+their format-specific package/signature checks. The packaging hook
 signs branded Squirrel/execution stubs and the final installer after bundling; final
 verification covers portable/CLI ZIPs, full update packages, installer signatures and
 the installer's embedded full-package hash. Manifests, checksums and attestations
diff --git a/docs/security/threat-model.md b/docs/security/threat-model.md
index 06b0771..a08e5c1 100644
--- a/docs/security/threat-model.md
+++ b/docs/security/threat-model.md
@@ -99,6 +99,13 @@ and provenance. The prepared app builder additionally preserves dependency bytes
 verifies Velopack helpers and the installer's embedded full-package payload. These
 controls are prepared locally; Azure and live CI proof are still required.
 
+Owned and preserved `.exe`/`.dll` headers are parsed before creating signing
+catalogs. An already corrupt source could otherwise retain its hash through every
+archive comparison. Regression tests reject malformed owned/dependency inputs,
+retain distinct culture-specific payloads and leave excluded/non-PE package
+formats to their applicable checks. This gate does not establish corruption's
+cause or replace final signature and payload verification.
+
 ## 8. Review log
 
 Generated-input regression coverage for T5 and T6 lives in