Packaging project caches stale NuGet assembly references across builds

[riverar]

Also filed in VSdevcom.

Describe the bug

When using the Packaging project to produce MSIX bundles for WinUI apps, downgrading a NuGet package reference and rebuilding results in the previously-built (higher-versioned) DLL being included in the bundle instead of the correct one. Neither Clean Solution or restarting Visual Studio resolves the issue.

(Note: Customer hit this in the field while upgrading a NuGet package reference but I kept the description consistent with my steps to reproduce.)

Steps to reproduce the bug

1. git clone https://github.com/riverar/repro-9db5e09ea4b6
2. Open App1.slnx in Visual Studio 2026
3. Double-click App1 in Solution Explorer
4. Observe CommunityToolkit.Mvvm is referencing version 8.3.2
5. Single-click the App1 (Package) in Solution Explorer
6. Select Project > Publish > Create app packages...
7. In the wizard, use the following publishing options:
   • Distribution method: Sideloading (without automatic updates)
   • Signing method: No, skip package signing
   • Architectures: x86, x64
8. After creating a package, navigate to App1 (Package)\AppPackages\App1 (Package)_1.0.14.0_Debug_Test
9. Open App1 (Package)_1.0.14.0_x86_x64_Debug.msixbundle in your favorite compression tool (e.g., 7-Zip)
10. Extract App1%20%28Package%29_1.0.14.0_x64_Debug.msix\App1\CommunityToolkit.Mvvm.dll
11. View the properties of the extracted library.
12. Observe the library is versioned 8.3.2.1.
13. In Visual Studio, double-click App1 in Solution Explorer
14. In the text editor, change CommunityToolkit.Mvvm to reference version 8.4.0 and save.
15. Select Build > Clean Solution
16. Repeat steps 5-11, changing the MSIX filenames as needed (if package version auto-increment is enabled)
17. Observe the library is versioned 8.4.0.1.
18. Repeat steps 13-16, but with version 8.3.2 again.
19. Observe the library is still versioned 8.4.0.1. ⚠️

Expected behavior

Bundled output to always match what is referenced in the project

Screenshots

No response

NuGet package version

None

Packaging type

Packaged (MSIX)

Windows version

Insider Build (xxxxx)

IDE

Visual Studio Enterprise 2026 (11519.219)

Additional context

No response

[riverar]

If this is external, who owns it? Do I need to file a bug on Visual Studio @lauren-ciha?

[lauren-ciha]

Hi @riverar, that's right. Here's the link to Developer Community.

[riverar]

Closing in favor of Developer Community bug https://developercommunity.visualstudio.com/t/Packaging-project-caches-stale-NuGet-ass/11051295?port=1026&fsid=8ce9f58f-c791-4ce1-abdd-c54e0b4f7596&refTime=1772139988779&refUserId=056e31d5-191c-418f-ab7c-f75e1f7f8727