Remove unused dependencies and shrink installer size (#47233)

## Summary of the Pull Request

Two related installer changes to (1) eliminate genuinely-unused
dependencies and (2) deduplicate shared WinAppSDK files between
`<install>\` and `<install>\WinUI3Apps\` to shrink the installer
download.

### 1. Remove unused dependencies (~11 MB savings per output location)

- **System.Data.SqlClient**: Removed from MouseWithoutBorders projects
and the central `Directory.Packages.props` pin. It was a transitive
dependency of `Microsoft.Windows.Compatibility` but PowerToys has zero
SQL database usage.
- **Unused `using` import**: Removed `using
System.ServiceModel.Channels` from MouseWithoutBorders `Program.cs` (no
WCF usage).
- **MFC / C++ AMP / OpenMP DLLs**: Added `RemoveUnusedVCRuntimeDlls`
target in `Directory.Build.targets` to clean up `mfc140*`, `mfcm140*`,
`vcamp140*`, and `vcomp140*` DLLs that leak from the VC++
Redistributable tree but are not imported by any PowerToys binary
(verified with `dumpbin /dependents` across all installed binaries).
Also excluded MFC DLLs from installer file collection.

### 2. WinAppSDK file deduplication (build-time only; install-time uses
copy)

**Background**: The `WinUI3Apps` subfolder must remain a real directory
because MSIX sparse package registration applies DACL changes to the
`ExternalLocation` folder (PR #47177). Flattening is not viable.

**Build-time** (`generateAllFileComponents.ps1`): computes the SHA256
intersection of root and `WinUI3Apps` files, and for each file that is
also present in the BaseApplications WXS file list, removes the
duplicate from the WinUI3Apps WXS component list and writes its name to
a `hardlinks.txt` manifest. The BaseApplications cross-check ensures we
never deduplicate a file the MSI does not actually deploy at the install
root, which would otherwise leave both copies missing post-install. The
manifest is written as UTF-8 without BOM (via
`[System.IO.File]::WriteAllLines` with `UTF8Encoding($false)`) so its
encoding is identical regardless of the build host's PowerShell version.
This step produces the **MSI download-size win** (~97 MB smaller cab;
LZX:21 was already deduplicating most byte-identical content
automatically inside the cab).

**Install-time** (`CreateWinAppSDKHardlinksCA` custom action):
- Reads `hardlinks.txt` after `InstallFiles` as a raw byte stream and
converts each line to a `std::wstring` via `MultiByteToWideChar(CP_UTF8,
MB_ERR_INVALID_CHARS, ...)`. Avoids `std::wifstream`'s ANSI-codepage
codecvt so non-ASCII paths can never be silently mangled.
- For each entry, computes `(installDir / fileName).lexically_normal()`
and `(winui3Dir / fileName).lexically_normal()`, then verifies via
`std::mismatch` that each resolved path is still rooted at its
respective folder. Manifest entries containing `..`, absolute paths, or
alternate-stream syntax are logged and skipped.
- Materialises each validated entry from `<install>\<name>` into
`<install>\WinUI3Apps\<name>` via `fs::copy_file` (overwrite_existing).
- Reports the per-file copy / failure counts to the install log. If
every entry failed (`created == 0 && failed > 0`), the CA escalates to
`E_FAIL` so the install does not silently succeed with an unusable
WinUI3Apps tree.

`DeleteWinAppSDKHardlinksCA` removes the materialised copies before
`RemoveFiles` on uninstall, using the same UTF-8 reader and per-entry
containment check.

**WiX sequencing**: `CreateWinAppSDKHardlinks` runs
`After="InstallFiles"` with `Condition="NOT Installed OR
WIX_UPGRADE_DETECTED OR REINSTALL"` so a `msiexec /fa` repair refreshes
the deduplicated copies (otherwise `RemoveFiles` would orphan them).

#### Why copy and not hard-link

A hard-linked variant of this CA was originally proposed but caused a
Monaco preview-handler regression. Hard-links share an NTFS inode (and
therefore one DACL) between `<install>\<file>` and
`<install>\WinUI3Apps\<file>`. The MSIX sparse-package registrations for
PowerRename / ImageResizer / FileLocksmith / NewPlus run after the dedup
CA and propagate the `WinUI3Apps` parent's rich DACL (Capability SID, 5×
Package SIDs, 5× conditional SYSAPPID ACE, RC SID) onto the shared
inode. The root path then also exposes the rich DACL, which trips a
kernel "stricter access evaluation" path that blocks the LOW-IL
`prevhost.exe` from `LoadLibrary`-ing `hostfxr.dll` (and the rest of the
.NET runtime), turning the Monaco preview pane blank for `.json` / `.md`
/ `.cs` / `.xaml` / `.svg` / `.xml` files.

`fs::copy_file` creates a **fresh inode** for the WinUI3Apps copy. The
root inode keeps its simple DACL (`SY:F + BA:F + owner:F` + inherited
`BU:RX`) so LOW-IL `prevhost.exe` can still load it — Monaco preview
works. The WinUI3Apps copy inherits the WinUI3Apps parent's rich DACL
via normal NTFS inheritance (matches 0.99.1 behaviour exactly) — MSIX
context-menu shells continue to work.

#### Trade-off

| Metric | Hard-link variant (rejected) | This PR (file copy) | 0.99.1
(no dedup) |
|---|---|---|---|
| MSI size | ~296 MB | ~296 MB | ~393 MB |
| On-disk after install | ~2,475 MB | ~2,772 MB | ~2,772 MB |
| DACL contamination risk | YES (broke Monaco) | NO | NO |

The on-disk savings (~297 MB) are given up in exchange for eliminating
the DACL contamination risk; the **installer download savings (~97 MB)**
are preserved by the build-time WiX/cab dedup.

#### Edge cases handled

- Empty duplicate list: `hardlinks.txt` always written, CA handles
empty.
- All files duplicated: `Generate-FileComponents` returns early for
empty list.
- File stripped from BaseApplications by an earlier build step:
BaseApplications cross-check skips it during dedup so neither copy goes
missing.
- Manifest entry escapes install root (`..`, absolute path): rejected
per-entry, install continues.
- Manifest line is non-UTF-8: rejected per-entry, install continues.
- Source missing at install time: per-entry skip, install continues.
- All copies fail: install aborts loudly via `E_FAIL` (catastrophic-case
escalation).
- Upgrade or `msiexec /fa` repair: CA fires (`NOT Installed OR
WIX_UPGRADE_DETECTED OR REINSTALL`).

**MSI repair risk**: Burn bundle uses `SuppressRepair=yes` and
`MajorUpgrade` (full uninstall + reinstall) for all version upgrades, so
the standard upgrade path is unaffected. The `OR REINSTALL` clause
covers power users running `msiexec /fa` directly.

## PR Checklist

- [x] **Communication:** Discussed approach via PRs #46866, #47177,
#46745
- [ ] **Tests:** Installer infrastructure only — no runtime behaviour
changes
- [ ] **Localization:** N/A
- [ ] **Dev docs:** N/A
- [ ] **New binaries:** N/A

## Detailed Description of the Pull Request / Additional comments

Based on the approach from PR #46745 by @yeelam-gordon, rebased onto
latest main and switched from hard-links to file copies after the DACL
contamination root cause was identified. Hardening (UTF-8 read, path
containment, catastrophic-case escalation, REINSTALL repair,
BaseApplications-filtered dedup) added in response to review feedback.

These changes are purely build/installer infrastructure — no runtime
behaviour changes to any PowerToys module.

## Validation Steps Performed

Validated on a 0.99.4 / 0.99.5 local install (per-user
`%LocalAppData%\PowerToys`):

- ✅ `dumpbin /dependents` across the installed PowerToys tree confirmed
zero binaries import `mfc140*`, `mfcm140*`, `vcamp140*`, or `vcomp140*`
— the cleanup target removes ~11 MB of genuinely unused VC runtime DLLs.
- ✅ `System.Data.SqlClient` has zero call-sites in PowerToys source.
- ✅ Local installer build produces a 296 MB MSI (down from 393 MB
pre-dedup, ~97 MB cab savings purely from the build-time WiX dedup).
- ✅ MSI table inspection (`wix msi decompile`) confirms the deferred CAs
are present (`CreateWinAppSDKHardlinks`, `DeleteWinAppSDKHardlinks`) and
the `hardlinks.txt` File row is registered.
- ✅ MSI table inspection confirms .NET runtime DLLs (`hostfxr.dll`,
`coreclr.dll`, `hostpolicy.dll`, `clretwrc.dll`, `Accessibility.dll`,
`backup_restore_settings.json`) appear ONLY in
`BaseApplicationsFiles_File_*`, NOT in `WinUI3ApplicationsFiles_File_*`
— proving the build-time dedup worked.
- ✅ Post-install verification: deduplicated files materialised at both
root and WinUI3Apps with byte-identical SHA256 hashes, and `fsutil
hardlink list` returns link-count == 1 for each — proving the
install-time copy approach worked, not hard-link.
- ✅ DACL on root .NET runtime DLLs is clean: no Package SID, no
Capability SID, no SYSAPPID conditional ACE, no `ALL APPLICATION
PACKAGES` ACE — Monaco preview load path is safe.
- ✅ DACL on WinUI3Apps copies has the rich MSIX inheritance —
context-menu shells continue to work (matches 0.99.1).
- ✅ All four MSIX sparse packages (PowerRename, ImageResizer,
FileLocksmith, NewPlus) registered after install.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/actions/spell-check/expect.txt

@@ -440,6 +440,7 @@ DString
 DSVG
 dto
 DUMMYUNIONNAME
+dumpbin
 dutil
 DVASPECT
 DVASPECTINFO
@@ -710,6 +711,7 @@ HOOKPROC
 HORZRES
 HORZSIZE
 Hostbackdropbrush
+hostfxr
 hostsfileeditor
 hotfixes
 hotkeycontrol
@@ -1022,6 +1024,7 @@ Metadatas
 metafile
 metapackage
 mfc
+mfcm
 Mgmt
 Microwaved
 middleclickaction

Directory.Build.targets

@@ -65,4 +65,20 @@
   <!-- Note: For C++ skipped test projects, build is effectively skipped by removing all compile items above.
        We don't define empty Build/Rebuild/Clean targets here because MSBuild Target definitions with Condition
        on the Target element still override the default targets even when condition is false. -->
+
+  <!-- Clean up unused VC++ runtime DLLs that CopyCppRuntimeToOutputDir copies from the full
+       VCRedist tree (MFC, C++ AMP, OpenMP). No PowerToys binary links against these — verified
+       with dumpbin /dependents across all installed binaries. -->
+  <Target Name="RemoveUnusedVCRuntimeDlls"
+          AfterTargets="Build"
+          Condition="'$(CopyCppRuntimeToOutputDir)' == 'true' and '$(MSBuildProjectExtension)' == '.vcxproj'">
+    <ItemGroup>
+      <_UnusedVCRuntimeDlls Include="$(OutDir)mfc140*.dll" />
+      <_UnusedVCRuntimeDlls Include="$(OutDir)mfcm140*.dll" />
+      <_UnusedVCRuntimeDlls Include="$(OutDir)vcamp140*.dll" />
+      <_UnusedVCRuntimeDlls Include="$(OutDir)vcomp140*.dll" />
+    </ItemGroup>
+    <Delete Files="@(_UnusedVCRuntimeDlls)" Condition="'@(_UnusedVCRuntimeDlls)' != ''" />
+    <Message Importance="normal" Text="Cleaned up unused VC runtime DLLs: @(_UnusedVCRuntimeDlls)" Condition="'@(_UnusedVCRuntimeDlls)' != ''" />
+  </Target>
 </Project>

Directory.Packages.props

@@ -110,8 +110,6 @@
     <PackageVersion Include="System.ComponentModel.Composition" Version="10.0.7" />
     <PackageVersion Include="System.Configuration.ConfigurationManager" Version="10.0.7" />
     <PackageVersion Include="System.Data.OleDb" Version="10.0.7" />
-    <!-- Package System.Data.SqlClient added to force it as a dependency of Microsoft.Windows.Compatibility to the latest version available at this time. -->
-    <PackageVersion Include="System.Data.SqlClient" Version="4.9.1" />
     <!-- Package System.Diagnostics.EventLog added as a hack for being able to exclude the runtime assets so they don't conflict with 8.0.1. This is a dependency of System.Data.OleDb but the 8.0.1 version wasn't published to nuget. -->
     <PackageVersion Include="System.Diagnostics.EventLog" Version="10.0.7" />
     <!-- Package System.Diagnostics.PerformanceCounter added as a hack for being able to exclude the runtime assets so they don't conflict with 8.0.11. -->

installer/PowerToysSetupCustomActionsVNext/CustomAction.cpp

@@ -4,6 +4,7 @@
 #include <ProjectTelemetry.h>
 #include <spdlog/sinks/base_sink.h>
 #include <filesystem>
+#include <fstream>
 #include <string_view>
 
 #include "../../src/common/logger/logger.h"
@@ -1807,6 +1808,223 @@ void initSystemLogger()
             } });
 }
 
+// Naming note: the *Hardlinks* names in this CA, the matching WiX CustomAction Ids
+// in Product.wxs, and the manifest filename "hardlinks.txt" are kept for continuity
+// with the original PR design. The implementation uses fs::copy_file -- not
+// CreateHardLinkW -- because hard-links share an inode (and DACL) between root and
+// WinUI3Apps, which lets MSIX sparse-package registration propagate a rich DACL onto
+// the root copy of files like hostfxr.dll and break LOW-IL prevhost.exe loads,
+// turning the Monaco preview pane blank. Copies create a fresh inode in WinUI3Apps so the root
+// copy keeps its simple DACL. See the in-body comment for the full RCA reference.
+UINT __stdcall CreateWinAppSDKHardlinksCA(MSIHANDLE hInstall)
+{
+    HRESULT hr = S_OK;
+    UINT er = ERROR_SUCCESS;
+    std::wstring installationFolder;
+
+    hr = WcaInitialize(hInstall, "CreateWinAppSDKHardlinks");
+    ExitOnFailure(hr, "Failed to initialize");
+    hr = getInstallFolder(hInstall, installationFolder);
+    ExitOnFailure(hr, "Failed to get installFolder.");
+
+    {
+        namespace fs = std::filesystem;
+        const fs::path installDir(installationFolder);
+        const fs::path winui3Dir = installDir / L"WinUI3Apps";
+        const fs::path manifestPath = winui3Dir / L"hardlinks.txt";
+
+        if (!fs::exists(manifestPath))
+        {
+            WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: No hardlinks.txt manifest found, skipping.");
+            goto LExit;
+        }
+
+        std::ifstream manifestFile(manifestPath);  // Read as bytes, then convert UTF-8 -> wide explicitly.
+        std::string narrowLine;
+        int created = 0;
+        int failed = 0;
+
+        // INSTALLFOLDER from MSI typically arrives with a trailing backslash. lexically_normal
+        // preserves that as an empty trailing path component, which would later make the
+        // per-component std::mismatch containment check below reject every legitimate entry.
+        // Strip any trailing separators before normalizing.
+        auto stripTrailingSep = [](fs::path p) {
+            auto s = p.native();
+            while (s.size() > 1 && (s.back() == L'\\' || s.back() == L'/')) s.pop_back();
+            return fs::path(s);
+        };
+
+        // Normalize once so the per-line containment check below is cheap.
+        const fs::path installDirNorm = stripTrailingSep(installDir).lexically_normal();
+        const fs::path winui3DirNorm  = stripTrailingSep(winui3Dir).lexically_normal();
+
+        while (std::getline(manifestFile, narrowLine))
+        {
+            if (narrowLine.empty())
+            {
+                continue;
+            }
+            // Strip CR if the manifest uses CRLF line endings.
+            if (narrowLine.back() == '\r')
+            {
+                narrowLine.pop_back();
+                if (narrowLine.empty()) continue;
+            }
+
+            // Manifest is written as UTF-8 (no BOM) -- convert to wide string explicitly
+            // rather than relying on the locale-default codecvt of std::wifstream, which is
+            // the ANSI code page on Windows and would silently mangle any non-ASCII path.
+            const int wideLen = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, narrowLine.c_str(), -1, nullptr, 0);
+            if (wideLen <= 0)
+            {
+                WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: Skipping non-UTF-8 entry: %hs", narrowLine.c_str());
+                failed++;
+                continue;
+            }
+            std::wstring fileName(static_cast<size_t>(wideLen) - 1, L'\0');
+            MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, narrowLine.c_str(), -1, fileName.data(), wideLen);
+
+            // Defense-in-depth: reject manifest entries that would escape the install root
+            // via "..", absolute paths, or alternate stream syntax. lexically_normal collapses
+            // any "." / ".." / repeated separators, then std::mismatch verifies the resolved
+            // path is still rooted at installDir / winui3Dir respectively.
+            const fs::path source = (installDir / fileName).lexically_normal();
+            const fs::path target = (winui3Dir  / fileName).lexically_normal();
+            const auto sourceIn = std::mismatch(installDirNorm.begin(), installDirNorm.end(), source.begin(), source.end());
+            const auto targetIn = std::mismatch(winui3DirNorm.begin(),  winui3DirNorm.end(),  target.begin(), target.end());
+            if (sourceIn.first != installDirNorm.end() || targetIn.first != winui3DirNorm.end())
+            {
+                WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: Rejecting entry outside install root: %ls", fileName.c_str());
+                failed++;
+                continue;
+            }
+
+            if (!fs::exists(source))
+            {
+                WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: Source not found: %ls", source.c_str());
+                failed++;
+                continue;
+            }
+
+            // Remove existing file if present (leftover from previous install)
+            std::error_code ec;
+            fs::remove(target, ec);
+
+            // Use a regular file copy (not a hard-link). Hard-links share an
+            // NTFS inode -- and therefore one DACL -- between root and
+            // WinUI3Apps, which lets MSIX sparse-package registration
+            // propagate the WinUI3Apps parent's rich (Capability/Package SID)
+            // DACL onto the root path. That trips a kernel "stricter access
+            // evaluation" path that blocks LOW-IL prevhost.exe from loading
+            // hostfxr.dll, so File Explorer Monaco preview goes blank on
+            // Windows 11 23H2. Copying creates a fresh inode in WinUI3Apps,
+            // so the root copy keeps its simple DACL while the WinUI3Apps
+            // copy inherits the rich DACL from its parent (matches 0.99.1
+            // behaviour). See Documents\PR-47233-Handoff.md for full RCA.
+            fs::copy_file(source, target, fs::copy_options::overwrite_existing, ec);
+            if (ec)
+            {
+                WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: Failed to copy: %ls (%hs)", fileName.c_str(), ec.message().c_str());
+                failed++;
+            }
+            else
+            {
+                created++;
+            }
+        }
+
+        WcaLog(LOGMSG_STANDARD, "CreateWinAppSDKHardlinks: Copied %d files, %d failures", created, failed);
+
+        // Catastrophic-case escalation: if every copy failed, the WinUI3Apps tree is
+        // unusable (Monaco preview / context-menu shells will break). Surface this rather
+        // than reporting install success. Per-file failures remain tolerated.
+        if (created == 0 && failed > 0)
+        {
+            hr = E_FAIL;
+            ExitOnFailure(hr, "All WinAppSDK file copies failed; aborting install.");
+        }
+    }
+
+LExit:
+    er = SUCCEEDED(hr) ? ERROR_SUCCESS : ERROR_INSTALL_FAILURE;
+    return WcaFinalize(er);
+}
+
+UINT __stdcall DeleteWinAppSDKHardlinksCA(MSIHANDLE hInstall)
+{
+    HRESULT hr = S_OK;
+    UINT er = ERROR_SUCCESS;
+    std::wstring installationFolder;
+
+    hr = WcaInitialize(hInstall, "DeleteWinAppSDKHardlinks");
+    ExitOnFailure(hr, "Failed to initialize");
+    hr = getInstallFolder(hInstall, installationFolder);
+    ExitOnFailure(hr, "Failed to get installFolder.");
+
+    {
+        namespace fs = std::filesystem;
+        const fs::path winui3Dir = fs::path(installationFolder) / L"WinUI3Apps";
+        const fs::path manifestPath = winui3Dir / L"hardlinks.txt";
+
+        if (!fs::exists(manifestPath))
+        {
+            goto LExit;
+        }
+
+        std::ifstream manifestFile(manifestPath);  // Read as bytes; convert UTF-8 -> wide explicitly.
+        std::string narrowLine;
+
+        // INSTALLFOLDER from MSI typically arrives with a trailing backslash; strip it before
+        // normalizing so the per-line containment check doesn't false-reject every entry.
+        auto stripTrailingSep = [](fs::path p) {
+            auto s = p.native();
+            while (s.size() > 1 && (s.back() == L'\\' || s.back() == L'/')) s.pop_back();
+            return fs::path(s);
+        };
+        const fs::path winui3DirNorm = stripTrailingSep(winui3Dir).lexically_normal();
+
+        while (std::getline(manifestFile, narrowLine))
+        {
+            if (narrowLine.empty())
+            {
+                continue;
+            }
+            if (narrowLine.back() == '\r')
+            {
+                narrowLine.pop_back();
+                if (narrowLine.empty()) continue;
+            }
+
+            const int wideLen = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, narrowLine.c_str(), -1, nullptr, 0);
+            if (wideLen <= 0)
+            {
+                WcaLog(LOGMSG_STANDARD, "DeleteWinAppSDKHardlinks: Skipping non-UTF-8 entry: %hs", narrowLine.c_str());
+                continue;
+            }
+            std::wstring fileName(static_cast<size_t>(wideLen) - 1, L'\0');
+            MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, narrowLine.c_str(), -1, fileName.data(), wideLen);
+
+            // Defense-in-depth: reject entries whose resolved target escapes WinUI3Apps.
+            const fs::path target = (winui3Dir / fileName).lexically_normal();
+            const auto inWinui3 = std::mismatch(winui3DirNorm.begin(), winui3DirNorm.end(), target.begin(), target.end());
+            if (inWinui3.first != winui3DirNorm.end())
+            {
+                WcaLog(LOGMSG_STANDARD, "DeleteWinAppSDKHardlinks: Rejecting entry outside WinUI3Apps: %ls", fileName.c_str());
+                continue;
+            }
+
+            std::error_code ec;
+            fs::remove(target, ec);
+        }
+
+        WcaLog(LOGMSG_STANDARD, "DeleteWinAppSDKHardlinks: Cleaned up deduplicated copy files");
+    }
+
+LExit:
+    er = SUCCEEDED(hr) ? ERROR_SUCCESS : ERROR_INSTALL_FAILURE;
+    return WcaFinalize(er);
+}
+
 // DllMain - Initialize and cleanup WiX custom action utils.
 extern "C" BOOL WINAPI DllMain(__in HINSTANCE hInst, __in ULONG ulReason, __in LPVOID)
 {

installer/PowerToysSetupCustomActionsVNext/CustomAction.def

@@ -36,3 +36,5 @@ EXPORTS
 	SetBundleInstallLocationCA
 	InstallPackageIdentityMSIXCA
 	UninstallPackageIdentityMSIXCA
+	CreateWinAppSDKHardlinksCA
+	DeleteWinAppSDKHardlinksCA

installer/PowerToysSetupVNext/Product.wxs

@@ -112,6 +112,8 @@
       <Custom Action="SetInstallCmdPalPackageParam" Before="InstallCmdPalPackage" />
       <Custom Action="SetUninstallCommandNotFoundParam" Before="UninstallCommandNotFound" />
       <Custom Action="SetUpgradeCommandNotFoundParam" Before="UpgradeCommandNotFound" />
+      <Custom Action="SetCreateWinAppSDKHardlinksParam" Before="CreateWinAppSDKHardlinks" />
+      <Custom Action="SetDeleteWinAppSDKHardlinksParam" Before="DeleteWinAppSDKHardlinks" />
       <Custom Action="SetApplyModulesRegistryChangeSetsParam" Before="ApplyModulesRegistryChangeSets" />
       <Custom Action="SetInstallPackageIdentityMSIXParam" Before="InstallPackageIdentityMSIX" />
 
@@ -124,6 +126,7 @@
       <Custom Action="SetBundleInstallLocationData" Before="SetBundleInstallLocation" Condition="NOT Installed OR WIX_UPGRADE_DETECTED" />
       <Custom Action="SetBundleInstallLocation" After="InstallFiles" Condition="NOT Installed OR WIX_UPGRADE_DETECTED" />
       <Custom Action="ApplyModulesRegistryChangeSets" After="InstallFiles" Condition="NOT Installed" />
+      <Custom Action="CreateWinAppSDKHardlinks" After="InstallFiles" Condition="NOT Installed OR WIX_UPGRADE_DETECTED OR REINSTALL" />
       <Custom Action="InstallCmdPalPackage" After="InstallFiles" Condition="NOT Installed" />
       <Custom Action="InstallPackageIdentityMSIX" After="InstallFiles" Condition="NOT Installed AND WINDOWSBUILDNUMBER &gt;= 22000" />
       <Custom Action="override Wix4CloseApplications_$(sys.BUILDARCHSHORT)" Before="RemoveFiles" />
@@ -137,6 +140,7 @@
         <?endif?>
         <Custom Action="TelemetryLogInstallSuccess" After="InstallFinalize" Condition="NOT Installed" />
       <Custom Action="TelemetryLogUninstallSuccess" After="InstallFinalize" Condition="Installed and (NOT UPGRADINGPRODUCTCODE) AND (REMOVE=&quot;ALL&quot;)" />
+      <Custom Action="DeleteWinAppSDKHardlinks" Before="RemoveFiles" Condition="Installed AND (REMOVE=&quot;ALL&quot;)" />
       <Custom Action="UnApplyModulesRegistryChangeSets" Before="RemoveFiles" Condition="Installed AND (REMOVE=&quot;ALL&quot;)" />
       <Custom Action="UnRegisterContextMenuPackages" Before="RemoveFiles" Condition="Installed AND (REMOVE=&quot;ALL&quot;)" />
       <Custom Action="CleanImageResizerRuntimeRegistry" Before="RemoveFiles" Condition="Installed AND (REMOVE=&quot;ALL&quot;)" />
@@ -189,8 +193,10 @@
     <CustomAction Id="SetUpgradeCommandNotFoundParam" Property="UpgradeCommandNotFound" Value="[INSTALLFOLDER]" />
 
     <CustomAction Id="SetCreateWinAppSDKHardlinksParam" Property="CreateWinAppSDKHardlinks" Value="[INSTALLFOLDER]" />
+    <CustomAction Id="CreateWinAppSDKHardlinks" Return="check" Impersonate="yes" Execute="deferred" DllEntry="CreateWinAppSDKHardlinksCA" BinaryRef="PTCustomActions" />
 
     <CustomAction Id="SetDeleteWinAppSDKHardlinksParam" Property="DeleteWinAppSDKHardlinks" Value="[INSTALLFOLDER]" />
+    <CustomAction Id="DeleteWinAppSDKHardlinks" Return="ignore" Impersonate="yes" Execute="deferred" DllEntry="DeleteWinAppSDKHardlinksCA" BinaryRef="PTCustomActions" />
 
     <CustomAction Id="SetCreatePTInteropHardlinksParam" Property="CreatePTInteropHardlinks" Value="[INSTALLFOLDER]" />
 

installer/PowerToysSetupVNext/WinUI3Applications.wxs

@@ -7,11 +7,18 @@
 
   <Fragment>
     <DirectoryRef Id="WinUI3AppsInstallFolder">
+      <Component Id="WinUI3Apps_Hardlinks_Manifest" Guid="F7A2C3D1-8E4B-4F6A-9D2E-1B3C5A7F8E90" Bitness="always64">
+        <RegistryKey Root="$(var.RegistryScope)" Key="Software\Classes\powertoys\components">
+          <RegistryValue Type="string" Name="WinUI3Apps_Hardlinks_Manifest" Value="" KeyPath="yes" />
+        </RegistryKey>
+        <File Id="WinUI3Apps_hardlinks_txt" Source="$(var.BinDir)\WinUI3Apps\hardlinks.txt" />
+      </Component>
     <!-- Generated by generateFileComponents.ps1 -->
     <!--WinUI3ApplicationsFiles_Component_Def-->
     </DirectoryRef>
 
     <ComponentGroup Id="WinUI3ApplicationsComponentGroup">
+      <ComponentRef Id="WinUI3Apps_Hardlinks_Manifest" />
     </ComponentGroup>
 
   </Fragment>

installer/PowerToysSetupVNext/generateAllFileComponents.ps1

@@ -30,6 +30,10 @@ Function Generate-FileList() {
 
     $fileInclusionList = @("*.dll", "*.exe", "*.json", "*.msix", "*.png", "*.gif", "*.ico", "*.cur", "*.svg", "index.html", "reg.js", "gitignore.js", "srt.js", "monacoSpecialLanguages.js", "customTokenThemeRules.js", "*.pri")
 
+    # MFC DLLs leak into the output via WindowsAppSDKSelfContained but no PowerToys binary imports them.
+    # Verified with dumpbin /dependents across all 2176 binaries — zero consumers.
+    $fileExclusionList += @("mfc140.dll", "mfc140u.dll", "mfcm140.dll", "mfcm140u.dll")
+
     $dllsToIgnore = @("System.CodeDom.dll", "WindowsBase.dll")
 
     if ($fileDepsJson -eq [string]::Empty) {
@@ -85,11 +89,16 @@ Function Generate-FileComponents() {
             [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseDeclaredVarsMoreThanAssignments', 'fileList',
             Justification = 'variable is used in another scope')]
 
-            $fileList = $matches[2] -split ';'
+            $fileList = $matches[2] -split ';' | Where-Object { $_ -ne '' }
             return
         }
     }
 
+    if ($null -eq $fileList -or $fileList.Count -eq 0) {
+        # No files to generate components for — leave placeholder intact
+        return
+    }
+
     $componentId = "$($fileListName)_Component"
 
     $componentDefs = "`r`n"
@@ -154,6 +163,67 @@ Generate-FileComponents -fileListName "BaseApplicationsFiles" -wxsFilePath $PSSc
 
 #WinUI3Applications
 Generate-FileList -fileDepsJson "" -fileListName WinUI3ApplicationsFiles -wxsFilePath $PSScriptRoot\WinUI3Applications.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps"
+
+# Deduplicate: Remove files from WinUI3Apps that are identical to root (same name + same hash).
+# These will be re-created as plain file copies at install time by CreateWinAppSDKHardlinksCA.
+# (The CA's name is historical: it now uses fs::copy_file rather than CreateHardLinkW to avoid
+# DACL contamination across the shared inode -- see CustomAction.cpp for details.)
+$rootPath = "$PSScriptRoot..\..\..\$platform\Release"
+$winui3Path = "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps"
+$winui3WxsPath = "$PSScriptRoot\WinUI3Applications.wxs"
+$winui3Wxs = Get-Content $winui3WxsPath -Raw
+$manifestPath = Join-Path $winui3Path "hardlinks.txt"
+
+if ($winui3Wxs -match "\<\?define WinUI3ApplicationsFiles=([^?]*)\?\>") {
+    $winui3FileList = $matches[1] -split ';' | Where-Object { $_ -ne '' }
+    $hardlinkFiles = @()
+
+    # Read the BaseApplications WXS file list so we only deduplicate files that the MSI
+    # is actually deploying to the install root. If a file was stripped from BaseApplications
+    # by an earlier step (e.g., the ImageResizer leaked-apphost workaround above), the
+    # install-time CA's source would be missing and both copies would disappear.
+    $baseAppsWxs = Get-Content $baseAppWxsPath -Raw
+    $baseAppsFileList = @()
+    if ($baseAppsWxs -match "\<\?define BaseApplicationsFiles=([^?]*)\?\>") {
+        $baseAppsFileList = $matches[1] -split ';' | Where-Object { $_ -ne '' }
+    }
+
+    foreach ($file in $winui3FileList) {
+        # Skip files that were intentionally not deployed to root by the build
+        if ($baseAppsFileList -notcontains $file) { continue }
+
+        $rootFile = Join-Path $rootPath $file
+        $winui3File = Join-Path $winui3Path $file
+        if ((Test-Path $rootFile) -and (Test-Path $winui3File)) {
+            $rootHash = (Get-FileHash $rootFile -Algorithm SHA256).Hash
+            $winui3Hash = (Get-FileHash $winui3File -Algorithm SHA256).Hash
+            if ($rootHash -eq $winui3Hash) {
+                $hardlinkFiles += $file
+            }
+        }
+    }
+
+    if ($hardlinkFiles.Count -gt 0) {
+        # Remove deduplicated files from WinUI3Apps file list
+        $remainingFiles = $winui3FileList | Where-Object { $_ -notin $hardlinkFiles }
+        if ($remainingFiles.Count -eq 0) {
+            # All files are duplicates — keep at least a dummy entry won't be emitted
+            # Generate-FileComponents handles empty defines by producing no <File> entries
+            $winui3Wxs = $winui3Wxs -replace "\<\?define WinUI3ApplicationsFiles=[^?]*\?\>", "<?define WinUI3ApplicationsFiles=?>"
+        } else {
+            $winui3Wxs = $winui3Wxs -replace "\<\?define WinUI3ApplicationsFiles=[^?]*\?\>", "<?define WinUI3ApplicationsFiles=$($remainingFiles -join ';')?>"
+        }
+        Set-Content -Path $winui3WxsPath -Value $winui3Wxs
+        Write-Host "Deduplicated $($hardlinkFiles.Count) files from WinUI3Apps (will be copied at install time)"
+    }
+
+    # Always write hardlinks.txt (may be empty — CA handles that gracefully)
+    # Write as UTF-8 without BOM so the install-time CA can read it via std::ifstream
+    # + MultiByteToWideChar(CP_UTF8) without dealing with PS-version-dependent default
+    # encodings or a leading BOM.
+    [System.IO.File]::WriteAllLines($manifestPath, [string[]]$hardlinkFiles, (New-Object System.Text.UTF8Encoding($false)))
+}
+
 Generate-FileComponents -fileListName "WinUI3ApplicationsFiles" -wxsFilePath $PSScriptRoot\WinUI3Applications.wxs
 
 #AdvancedPaste

src/modules/MouseWithoutBorders/App/Class/Program.cs

@@ -21,7 +21,6 @@ using System.IO.Pipes;
 using System.Linq;
 using System.Security.Authentication.ExtendedProtection;
 using System.Security.Principal;
-using System.ServiceModel.Channels;
 using System.ServiceProcess;
 using System.Threading;
 using System.Threading.Tasks;

src/modules/MouseWithoutBorders/App/Helper/MouseWithoutBordersHelper.csproj

@@ -66,7 +66,6 @@
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" />
     <PackageReference Include="Microsoft.Windows.Compatibility" />
     <PackageReference Include="StreamJsonRpc" />
-    <PackageReference Include="System.Data.SqlClient" /> <!-- It's a dependency of Microsoft.Windows.Compatibility. We're adding it here to force it to the version specified in Directory.Packages.props -->
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\common\GPOWrapper\GPOWrapper.vcxproj" />

src/modules/MouseWithoutBorders/App/MouseWithoutBorders.csproj

@@ -214,7 +214,6 @@
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" />
     <PackageReference Include="Microsoft.Windows.Compatibility" />
     <PackageReference Include="StreamJsonRpc" />
-    <PackageReference Include="System.Data.SqlClient" /> <!-- It's a dependency of Microsoft.Windows.Compatibility. We're adding it here to force it to the version specified in Directory.Packages.props -->
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\common\GPOWrapper\GPOWrapper.vcxproj" />

src/modules/MouseWithoutBorders/App/Service/MouseWithoutBordersService.csproj

@@ -71,7 +71,6 @@
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Microsoft.Extensions.Hosting.WindowsServices" />
     <PackageReference Include="StreamJsonRpc" />
-    <PackageReference Include="System.Data.SqlClient" /> <!-- It's a dependency of Microsoft.Windows.Compatibility. We're adding it here to force it to the version specified in Directory.Packages.props -->
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\common\GPOWrapper\GPOWrapper.vcxproj" />