.NET: Foundry.Hosting IT - eliminate MSBuild parallel-output races

.github/workflows/dotnet-build-and-test.yml

@@ -340,7 +340,6 @@ jobs:
     runs-on: ubuntu-latest
     environment: integration
     env:
-      targetFramework: net10.0
       configuration: Release
     steps:
       - uses: actions/checkout@v6
@@ -357,31 +356,15 @@ jobs:
         with:
           global-json-file: ${{ github.workspace }}/dotnet/global.json
 
-      - name: Generate test solution (no samples)
-        shell: pwsh
-        run: |
-          ./dotnet/eng/scripts/New-FilteredSolution.ps1 `
-            -Solution dotnet/agent-framework-dotnet.slnx `
-            -TargetFramework $env:targetFramework `
-            -Configuration $env:configuration `
-            -ExcludeSamples `
-            -OutputPath dotnet/filtered.slnx `
-            -Verbose
-
-      - name: Generate Foundry hosted IT filtered solution
-        shell: pwsh
-        run: |
-          ./dotnet/eng/scripts/New-FilteredSolution.ps1 `
-            -Solution dotnet/filtered.slnx `
-            -TargetFramework $env:targetFramework `
-            -Configuration $env:configuration `
-            -TestProjectNameFilter "Foundry.Hosting.IntegrationTests*" `
-            -OutputPath dotnet/filtered-foundry-hosted.slnx `
-            -Verbose
-
+      # Build the test csproj directly instead of a filtered slnx + -f override.
+      # The test project pins TargetFrameworks=net10.0 and its ProjectReference closure
+      # gives MSBuild a single-rooted graph, so each multi-targeted dependency is invoked
+      # exactly once for net10.0. This avoids the MSB3026/MSB3491/MSB4018/MSB3883 file-lock
+      # collisions caused by parallel inner-builds racing on shared bin/obj output paths
+      # under the previous slnx + global TFM override approach.
       - name: Build Foundry hosted IT (and its deps)
         shell: bash
-        run: dotnet build dotnet/filtered-foundry-hosted.slnx -c "$configuration" -f "$targetFramework" --warnaserror
+        run: dotnet build dotnet/tests/Foundry.Hosting.IntegrationTests/Foundry.Hosting.IntegrationTests.csproj -c "$configuration" --warnaserror
 
       - name: Azure CLI Login
         uses: azure/login@v2
@@ -394,13 +377,12 @@ jobs:
       # are picked up; the image tag is content-hashed across the test container source AND its
       # framework project references, so identical content is a no-op push.
       #
-      # `-UsePrebuiltProjectReferences` opts into the no-rebuild fast path: publish skips
-      # rebuilding ProjectReferences and consumes the DLLs the prior "Build Foundry hosted IT
-      # (and its deps)" step already produced. This avoids MSB3026 ("file is being used by
-      # another process") collisions caused by the previous build's shared-compilation server
-      # still holding file handles to those DLLs. Safe in CI because the prebuild step ran in
-      # the same job against the same source. Do not remove the prebuild step (the subsequent
-      # `dotnet test --no-build` step depends on it too).
+      # The script always passes --no-dependencies to dotnet publish so publish never re-touches
+      # the framework lib DLLs the prior "Build Foundry hosted IT (and its deps)" step produced.
+      # This structurally eliminates the MSB3026 collision that VBCSCompiler from the prebuild
+      # would otherwise cause by holding file handles to those DLLs. Do not remove the prebuild
+      # step: the subsequent `dotnet test --no-build` step and the publish's ProjectReference
+      # resolution both depend on the prebuilt outputs being present.
       - name: Build and push Foundry Hosted Agents test container
         id: build-foundry-hosted-image
         shell: pwsh
@@ -410,14 +392,13 @@ jobs:
           if ([string]::IsNullOrWhiteSpace($registry)) {
             throw "IT_HOSTED_AGENT_REGISTRY not set in the integration environment."
           }
-          & "${{ github.workspace }}/dotnet/tests/Foundry.Hosting.IntegrationTests/scripts/it-build-image.ps1" -Registry $registry -UsePrebuiltProjectReferences | Tee-Object -FilePath $env:GITHUB_ENV -Append
+          & "${{ github.workspace }}/dotnet/tests/Foundry.Hosting.IntegrationTests/scripts/it-build-image.ps1" -Registry $registry | Tee-Object -FilePath $env:GITHUB_ENV -Append
 
       - name: Run Foundry Hosted Agents Integration Tests
         shell: pwsh
         working-directory: dotnet
         run: |
-          dotnet test --solution ./filtered-foundry-hosted.slnx `
-            -f $env:targetFramework `
+          dotnet test --project tests/Foundry.Hosting.IntegrationTests/Foundry.Hosting.IntegrationTests.csproj `
             -c $env:configuration `
             --no-build -v Normal `
             --report-xunit-trx `

dotnet/tests/Foundry.Hosting.IntegrationTests/scripts/it-build-image.ps1

@@ -41,14 +41,7 @@ param(
 
     [string] $Repository = "foundry-hosting-it",
 
-    [string] $TestContainerProject = "dotnet/tests/Foundry.Hosting.IntegrationTests.TestContainer",
-
-    # Explicit opt-in for the no-rebuild fast path. CI sets this after running the
-    # "Build Foundry hosted IT (and its deps)" step, which guarantees the prebuilt
-    # library DLLs match current source. Off by default so local invocations always
-    # let publish rebuild ProjectReferences and never produce an image whose tag is
-    # computed from current source while the contents come from a stale build.
-    [switch] $UsePrebuiltProjectReferences
+    [string] $TestContainerProject = "dotnet/tests/Foundry.Hosting.IntegrationTests.TestContainer"
 )
 
 $ErrorActionPreference = "Stop"
@@ -107,60 +100,35 @@ if (Test-Path $out) {
     Remove-Item -Recurse -Force $out
 }
 
-# Conditionally tell publish to skip rebuilding ProjectReferences and consume the
-# prebuilt library DLLs in place. This avoids two failure modes that arise when
-# the CI workflow runs a `dotnet build` of the same library projects immediately
-# before this script:
-#   1) MSB3026 "file is being used by another process" when publish's MSBuild
-#      tries to overwrite src/<lib>/bin/Release/net10.0/<lib>.dll while the
-#      previous build's shared-compilation server still holds a file handle.
-#   2) Publish needlessly rebuilding identical managed (RID-agnostic) library
-#      DLLs that prebuild already produced.
-# Gated on -UsePrebuiltProjectReferences (a strict opt-in) instead of marker
-# detection, because a developer machine may have a stale Release build of the
-# libraries from days ago; using those would silently produce an image whose
-# content is older than the source the tag is computed from.
-$publishExtraArgs = @()
-if ($UsePrebuiltProjectReferences) {
-    Write-Host "-UsePrebuiltProjectReferences: skipping ProjectReference rebuild." -ForegroundColor DarkGray
-    $publishExtraArgs += "-p:BuildProjectReferences=false"
-} else {
-    # Preflight: in default (rebuild) mode, publish propagates RuntimeIdentifier=linux-musl-x64
-    # to library ProjectReferences and writes their intermediates to a RID-suffixed obj path
-    # (e.g. obj/Release/net10.0/linux-musl-x64/). DefaultItemExcludes follows the new
-    # IntermediateOutputPath, so any *.AssemblyInfo.cs left in obj/Release/net10.0/ from a
-    # prior `dotnet build` is no longer excluded and gets picked up by the **/*.cs Compile
-    # glob, producing CS0579 "duplicate attribute" errors. Detect that state up front and
-    # tell the user exactly how to recover.
-    $staleObjProbes = @(
-        "dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/obj/Release/net10.0",
-        "dotnet/src/Microsoft.Agents.AI.Foundry/obj/Release/net10.0",
-        "dotnet/src/Microsoft.Agents.AI/obj/Release/net10.0",
-        "dotnet/src/Microsoft.Agents.AI.Abstractions/obj/Release/net10.0"
-    )
-    $stale = @($staleObjProbes | Where-Object { Test-Path (Join-Path $_ "*.AssemblyInfo.cs") })
-    if ($stale.Count -gt 0) {
-        $msg = @(
-            "Detected prior Release/net10.0 build outputs in:"
-            ($stale | ForEach-Object { "  - $_" })
-            ""
-            "Publish would propagate -r linux-musl-x64 to those ProjectReferences and the"
-            "leftover obj/Release/net10.0/*.AssemblyInfo.cs files would cause CS0579 duplicate"
-            "attribute errors. Pick one:"
-            "  (a) Pass -UsePrebuiltProjectReferences (skips ProjectReference rebuild and"
-            "      uses the existing src/<lib>/bin/Release/net10.0/*.dll outputs in place)."
-            "      Only safe when you know those DLLs match current source - this is the path"
-            "      CI uses immediately after its 'Build Foundry hosted IT (and its deps)' step."
-            "  (b) Remove the stale obj/Release trees, e.g.:"
-            "        Remove-Item -Recurse -Force dotnet/src/Microsoft.Agents.AI*/obj/Release"
-            "      and re-run."
-        ) -join "`n"
-        throw $msg
-    }
-    Write-Host "Letting publish build ProjectReferences (pass -UsePrebuiltProjectReferences in CI to skip)." -ForegroundColor DarkGray
+# Always tell publish to skip ProjectReference rebuilds via --no-dependencies. Publish
+# resolves TestContainer's framework lib references (Foundry, Foundry.Hosting and their
+# transitive deps) by reading the prebuilt DLLs at src/<lib>/bin/Release/net10.0/*.dll.
+# This:
+#   1) Structurally avoids the MSB3026 "file is being used by another process" race that
+#      occurs when publish overwrites the same DLL paths a prior `dotnet build` produced
+#      while VBCSCompiler from that build still holds file handles.
+#   2) Avoids needlessly rebuilding identical managed (RID-agnostic) library DLLs.
+# Callers MUST run `dotnet build dotnet/tests/Foundry.Hosting.IntegrationTests/Foundry.Hosting.IntegrationTests.csproj -c Release`
+# (or equivalent) first so those prebuilt DLLs exist. The CI workflow does this in the
+# preceding "Build Foundry hosted IT (and its deps)" step.
+$prebuildProbes = @(
+    "dotnet/src/Microsoft.Agents.AI.Foundry/bin/Release/net10.0/Microsoft.Agents.AI.Foundry.dll",
+    "dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/bin/Release/net10.0/Microsoft.Agents.AI.Foundry.Hosting.dll"
+)
+$missingPrebuilds = @($prebuildProbes | Where-Object { -not (Test-Path $_) })
+if ($missingPrebuilds.Count -gt 0) {
+    $msg = @(
+        "Required prebuilt outputs not found:"
+        ($missingPrebuilds | ForEach-Object { "  - $_" })
+        ""
+        "Publish runs with --no-dependencies and consumes prebuilt DLLs in place. Build the"
+        "test project first so its ProjectReference closure populates src/<lib>/bin/Release/net10.0/:"
+        "  dotnet build dotnet/tests/Foundry.Hosting.IntegrationTests/Foundry.Hosting.IntegrationTests.csproj -c Release"
+    ) -join "`n"
+    throw $msg
 }
 
-dotnet publish $TestContainerProject -c Release -f net10.0 -r linux-musl-x64 --self-contained false -o $out @publishExtraArgs --tl:off | Out-Host
+dotnet publish $TestContainerProject -c Release -f net10.0 -r linux-musl-x64 --self-contained false --no-dependencies -o $out --tl:off | Out-Host
 if ($LASTEXITCODE -ne 0) {
     throw "dotnet publish failed with exit code $LASTEXITCODE."
 }