Switch to AnyCPU for libraries, migrate to slnx

.github/PULL_REQUEST_TEMPLATE.md

@@ -4,7 +4,7 @@ Thanks for contributing to Reactor! A few notes before you open this PR:
 - Link the issue or spec this PR addresses (Fixes #..., Implements docs/specs/0XX-...).
 - Keep the change focused. Smaller, well-scoped PRs land faster.
 - Include tests. See CONTRIBUTING.md for the unit / selftest / e2e split.
-- Run `dotnet build Reactor.sln -p:Platform=x64` and `dotnet test tests/Reactor.Tests` locally.
+- Run `dotnet build Reactor.slnx` and `dotnet test tests/Reactor.Tests` locally.
 - First-time contributors: the Microsoft CLA bot will comment automatically; sign once and you're set.
 -->
 
@@ -22,7 +22,7 @@ Thanks for contributing to Reactor! A few notes before you open this PR:
 - [ ] Added unit tests in tests/Reactor.Tests/...
 - [ ] Added selftest fixture in tests/Reactor.AppTests.Host/SelfTest/Fixtures/...
 - [ ] Ran `dotnet test tests/Reactor.Tests`
-- [ ] Manually ran `dotnet run --project samples/Reactor.TestApp -p:Platform=x64`
+- [ ] Manually ran `dotnet run --project samples/Reactor.TestApp`
 -->
 
 ## Risk / breaking changes

.github/workflows/ci.yml

@@ -68,10 +68,10 @@ jobs:
           dotnet-version: 10.0.x
 
       - name: Restore
-        run: dotnet restore tests/Reactor.Tests/Reactor.Tests.csproj
+        run: dotnet restore tests/Reactor.Tests/Reactor.Tests.csproj -p:Platform=x64
 
       - name: Test
-        run: dotnet test tests/Reactor.Tests/Reactor.Tests.csproj --no-restore --logger "console;verbosity=normal"
+        run: dotnet test tests/Reactor.Tests/Reactor.Tests.csproj --no-restore -p:Platform=x64 --logger "console;verbosity=normal"
 
   selftests:
     name: Selftests
@@ -87,10 +87,10 @@ jobs:
           dotnet-version: 10.0.x
 
       - name: Restore
-        run: dotnet restore tests/Reactor.SelfTests/Reactor.SelfTests.csproj
+        run: dotnet restore tests/Reactor.SelfTests/Reactor.SelfTests.csproj -p:Platform=x64
 
       - name: Test
-        run: dotnet test tests/Reactor.SelfTests/Reactor.SelfTests.csproj --no-restore --logger "console;verbosity=normal"
+        run: dotnet test tests/Reactor.SelfTests/Reactor.SelfTests.csproj --no-restore -p:Platform=x64 --logger "console;verbosity=normal"
 
   build-solution:
     name: Build solution
@@ -106,7 +106,7 @@ jobs:
           dotnet-version: 10.0.x
 
       - name: Restore
-        run: dotnet restore Reactor.sln
+        run: dotnet restore Reactor.slnx
 
       - name: Build
-        run: dotnet build Reactor.sln --no-restore --configuration Release
+        run: dotnet build Reactor.slnx --no-restore --configuration Release

.github/workflows/coverage.yml

@@ -66,30 +66,35 @@ jobs:
       - name: Build for instrumentation
         shell: pwsh
         run: |
-          dotnet build tests/Reactor.Tests           -c Debug -p:Optimize=false -p:DebugType=portable
+          dotnet build tests/Reactor.Tests           -c Debug -p:Platform=x64 -p:Optimize=false -p:DebugType=portable
           dotnet build src/Reactor                   -c Debug -p:Optimize=false -p:DebugType=portable --no-incremental
-          dotnet build tests/Reactor.AppTests.Host   -c Debug -p:Optimize=false -p:DebugType=portable --no-incremental
+          dotnet build tests/Reactor.AppTests.Host   -c Debug -p:Platform=x64 -p:Optimize=false -p:DebugType=portable --no-incremental
 
       - name: Collect unit coverage
         shell: pwsh
         run: |
           dotnet-coverage collect -s coverage.settings.xml `
             --output unit.cobertura.xml --output-format cobertura `
-            -- dotnet test tests/Reactor.Tests --no-build
+            -- dotnet test tests/Reactor.Tests --no-build -p:Platform=x64
 
       - name: Instrument Reactor.dll
         shell: pwsh
         run: |
+          $dll = Get-ChildItem -Path "tests/Reactor.AppTests.Host/bin" -Recurse -Filter "Reactor.dll" |
+                   Where-Object { $_.FullName -notmatch 'ref[\\/]' } |
+                   Select-Object -First 1
+          if (-not $dll) { throw "Reactor.dll not found under tests/Reactor.AppTests.Host/bin" }
+          Write-Host "Instrumenting: $($dll.FullName)"
           dotnet-coverage instrument `
-            "tests/Reactor.AppTests.Host/bin/x64/Debug/net10.0-windows10.0.22621.0/Reactor.dll" `
+            $dll.FullName `
             -s coverage.settings.xml
 
       - name: Collect selftest coverage
         shell: pwsh
         run: |
           dotnet-coverage collect -s coverage.settings.xml `
             --output selftest.cobertura.xml --output-format cobertura `
-            -- dotnet run --project tests/Reactor.AppTests.Host --no-build -- --self-test
+            -- dotnet run --project tests/Reactor.AppTests.Host --no-build -p:Platform=x64 -- --self-test
 
       - name: Merge cobertura reports
         shell: pwsh

.github/workflows/release.yml

@@ -91,17 +91,16 @@ jobs:
           Write-Host "Version: $version  (event=$eventName, isTag=$isTag)"
 
       - name: Restore
-        run: dotnet restore Reactor.sln
+        run: dotnet restore Reactor.slnx
 
       - name: Build framework + analyzers
-        run: dotnet build Reactor.sln --no-restore --configuration Release -p:Platform=x64
+        run: dotnet build Reactor.slnx --no-restore --configuration Release
 
       - name: Pack framework NuGet
         run: >
           dotnet pack src/Reactor/Reactor.csproj
           --no-build --configuration Release
           -p:Version=${{ steps.version.outputs.version }}
-          -p:Platform=x64
           -o artifacts/nupkg
 
       - name: Pack Templates
@@ -121,7 +120,6 @@ jobs:
           --configuration Release
           --runtime win-x64
           --self-contained false
-          -p:Platform=x64
           -p:Version=${{ steps.version.outputs.version }}
           -o artifacts/mur/x64
 
@@ -131,7 +129,6 @@ jobs:
           --configuration Release
           --runtime win-arm64
           --self-contained false
-          -p:Platform=ARM64
           -p:Version=${{ steps.version.outputs.version }}
           -o artifacts/mur/arm64
 

AGENTS.md

@@ -5,8 +5,8 @@ Reactor is a declarative, component-based C# framework for building WinUI 3 desk
 ## Build, Test, Lint
 
 ```bash
-# Build (platform defaults to machine arch; force with -p:Platform=x64 or ARM64)
-dotnet build Reactor.sln
+# Build (platform defaults to machine arch for apps; libraries are AnyCPU)
+dotnet build Reactor.slnx
 
 # Unit tests — xUnit, headless, fast (~2200 tests incl. 590 Yoga fixtures)
 dotnet test tests/Reactor.Tests

CONTRIBUTING.md

@@ -36,26 +36,33 @@ This project has adopted the [Microsoft Open Source Code of Conduct](https://ope
 
 ```bash
 # Restore packages (pulls experimental WinUI 3 from NuGet)
-dotnet restore Reactor.sln
+dotnet restore Reactor.slnx
 
 # Build the entire solution (framework, tests, test app, samples)
-dotnet build Reactor.sln -p:Platform=x64
+dotnet build Reactor.slnx
 
 # Build just the framework
-dotnet build src/Reactor/Reactor.csproj -p:Platform=x64
+dotnet build src/Reactor/Reactor.csproj
 ```
 
 ### From Visual Studio
 
-1. Open `Reactor.sln` in Visual Studio 2022 (17.8+)
-2. Select the **x64** or **ARM64** platform from the toolbar (not "Any CPU")
+1. Open `Reactor.slnx` in Visual Studio 2022 (17.8+)
+2. Select the **x64** or **ARM64** platform from the toolbar
 3. Build the solution (Ctrl+Shift+B)
 
 Visual Studio will restore NuGet packages on first load, pulling the experimental Windows App SDK.
 
 ### Platforms
 
-The solution targets `x64` and `ARM64`. Omit `-p:Platform=...` to use the default (ARM64 on ARM machines, x64 on Intel). Add `-p:Platform=ARM64` or `-p:Platform=x64` to force one.
+Library projects (`Reactor`, `Reactor.Interop.WinForms`) are architecture-neutral (`AnyCPU`). Application projects (samples, tests, CLI) target `x64` and `ARM64`.
+
+When building via the solution (`dotnet build Reactor.slnx`), the platform is selected automatically. When building a single app project directly, pass `-p:Platform=x64` (or `ARM64`):
+
+```bash
+dotnet build tests/Reactor.Tests -p:Platform=x64
+dotnet test  tests/Reactor.Tests -p:Platform=x64
+```
 
 ---
 
@@ -201,7 +208,7 @@ Replace `$(RuntimeIdentifier)` with `ARM64` or `x64`, or omit the platform segme
 The interactive demo app exercises every built-in control:
 
 ```bash
-dotnet run --project samples/Reactor.TestApp -p:Platform=x64
+dotnet run --project samples/Reactor.TestApp
 ```
 
 ---

Directory.Build.props

@@ -10,11 +10,4 @@
     <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
   </PropertyGroup>
 
-  <!-- Default Platform to the current machine architecture so that
-       dotnet build / dotnet watch work without -p:Platform=ARM64. -->
-  <PropertyGroup Condition="'$(Platform)' == '' or '$(Platform)' == 'AnyCPU'">
-    <Platform Condition="'$(PROCESSOR_ARCHITECTURE)' == 'ARM64'">ARM64</Platform>
-    <Platform Condition="'$(PROCESSOR_ARCHITECTURE)' != 'ARM64'">x64</Platform>
-  </PropertyGroup>
-
 </Project>

README.md

@@ -190,11 +190,11 @@ class App : Component
 
 ```bash
 # Restore and build
-dotnet restore Reactor.sln
-dotnet build Reactor.sln -p:Platform=x64
+dotnet restore Reactor.slnx
+dotnet build Reactor.slnx
 
 # Run the interactive demo app
-dotnet run --project samples/Reactor.TestApp -p:Platform=x64
+dotnet run --project samples/Reactor.TestApp
 
 # Unit tests (xUnit, headless)
 dotnet test tests/Reactor.Tests