Certificate conflict when installing multi-architecture MSIX bundle

Describe the bug

I created a packaged WinUI application and generated the app package with the following settings:

• Always generate app bundle: Enabled
• Target architectures: x64 and ARM64

After the package is generated, the output folder structure looks like this:

When I run Install.ps1 on an x64 system, the installation fails with the following error:

Found bundle: C:\Users\peter\Desktop\main_ui_1.0.141.0_Test - Copy\main_ui_1.0.141.0_x64_arm64.msixbundle
Error: More than one certificate found in the script directory. Please make sure only the certificate used to sign the > package or bundle you are installing is placed in the same directory as this script.
Press Enter to continue...:

It appears that multiple certificate files are generated in the package directory, causing Install.ps1 to fail when trying to determine which certificate should be used.

This issue seems to occur only with Visual Studio 2026. I did not encounter the same behavior with previous versions of Visual Studio.

Expected behavior

Install.ps1 should be able to identify the correct certificate and install the MSIX bundle successfully, even when the bundle contains multiple target architectures.

Actual behavior

The installation script stops with the "More than one certificate found" error.

Steps to reproduce the bug

1. Create a WinUI3 Packaged project with VS2026
2. Create a package with:

• Always generate app bundle: Enabled
• Target architectures: x64 and ARM64

3. Run Install.ps1 in the generated package

Expected behavior

No response

Screenshots

No response

NuGet package version

WindowsAppSDK 2.4.0

Packaging type

Packaged (MSIX)

Windows version

Windows 11 version 24H2 (26100, June 2025 Update)

IDE

Other

Additional context

No response

Reproduce the packaged WinUI3 project with Visual Studio 2026, x64 and ARM64 targets, then start by inspecting the generated Install.ps1 and the certificate files in its package directory. Run the script on an x64 Windows 11 system and verify that the multi-architecture MSIX bundle installs without the "More than one certificate found" error.