[v11][maui] Editor errors shown in platform specific .cs files (Android, iOS) in a MAUI app

[mauroa]

Describe the issue

When opening .cs files from the "Platforms/iOS" or "Platforms/Android" sub-folders, editor errors are shown everywhere (see screenshots below). Notice that this doesn't prevent the project to restore or the app to build.

Collect logs

csdevkit-logs-2026-08-31T12-36-04.zip

Steps to reproduce

1. Install a C# DevKit v2 extension with MAUI support: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=15073180&view=results
2. Install a .NET MAUI v2 extension (VSIX artifact): https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=15076165&view=results
3. Create or open a .NET MAUI project
4. Wait for C# DevKit and .NET MAUI extension to load
5. Open any .cs file under "Platforms/iOS" or "Platforms/Android"

Expected behavior

No errors or warnings should be shown in the .cs file

Environment information

• VSCode: 1.136.0-insider (Universal)
• .NET SDK: 11.0.100-preview.7.26381.103
• MAUI: 11.0.0-preview.7.26403.4

Extension:

• NET MAUI: 1.17.228-g7a01fb0c71
• C# Dev Kit: 9.9.462-gf055a7
• C#: 2.151.17

[LittleLittleCloud]

Root cause

ProjectData cache v2 compresses SDK reference-pack assemblies into [frameworkPacks] entries. When reading the cache, C# Dev Kit requires the installed pack's major version to match the target framework major.

This works for shared-framework packs such as Microsoft.NETCore.App.Ref, but not for MAUI workload packs. For example, a net10.0-maccatalyst project can use a 26.x Mac Catalyst pack, while Android packs use a 36.x version. These packs were therefore not resolved from the cache, causing platform assemblies such as Microsoft.MacCatalyst.dll, Microsoft.iOS.dll, and Mono.Android.dll to be omitted from the Roslyn workspace.

Restore and build were unaffected because MSBuild uses the original resolved references directly. Only editor diagnostics were affected.

The fix restricts framework-pack compression to packs whose names end in .App.Ref. MAUI workload-pack assemblies remain as explicit metadata references and no longer depend on version inference.

[emaf]

Xiaoyun Zhang (@LittleLittleCloud) did we fix this already?