Fix Hosting-1 Windows runner crash by disabling test parallelization

.github/workflows/run-tests.yml

@@ -257,6 +257,8 @@ jobs:
       # Workaround for bug in Azure Functions Worker SDK. See https://github.com/Azure/azure-functions-dotnet-worker/issues/2969.
       - name: Rebuild for Azure Functions project
         if: inputs.testShortName == 'Playground'
+        env:
+          UseSharedCompilation: ${{ runner.os == 'Windows' && 'false' || '' }}
         run: |
           ${{ env.DOTNET_SCRIPT }} build ${{ github.workspace }}/playground/AzureFunctionsEndToEnd/AzureFunctionsEndToEnd.Functions/AzureFunctionsEndToEnd.Functions.csproj /p:SkipUnstableEmulators=true
 
@@ -301,6 +303,15 @@ jobs:
         if: runner.os == 'macOS'
         uses: ./.github/actions/unlock-macos-keychain
 
+      # Shut down the Roslyn compiler server before running tests. On resource-constrained
+      # runners (e.g. 2-core windows-latest), VBCSCompiler stays resident and consumes
+      # ~150% CPU / 700MB RAM, starving the runner agent and causing "lost communication"
+      # crashes. This is fast and idempotent (no-op if no server is running).
+      # See https://github.com/microsoft/aspire/issues/15832
+      - name: Shutdown build server
+        if: runner.os == 'Windows'
+        run: ${{ env.DOTNET_SCRIPT }} build-server shutdown
+
       - name: Run nuget dependent tests (Linux/macOS)
         if: ${{ inputs.requiresNugets && runner.os != 'Windows' }}
         working-directory: ${{ github.workspace }}/run-tests/
@@ -354,14 +365,17 @@ jobs:
           TEST_LOG_PATH: ${{ github.workspace }}/artifacts/log/test-logs
           TestsRunningOutsideOfRepo: true
           TESTCONTAINERS_HUB_IMAGE_NAME_PREFIX: 'netaspireci.azurecr.io'
+          # Prevent VBCSCompiler from starting during tests. See #15832
+          UseSharedCompilation: false
           # PR metadata and token for CLI E2E tests that download artifacts from a PR
           GITHUB_PR_NUMBER: ${{ inputs.requiresCliArchive && github.event.pull_request.number || '' }}
           GITHUB_PR_HEAD_SHA: ${{ inputs.requiresCliArchive && github.event.pull_request.head.sha || '' }}
           GH_TOKEN: ${{ inputs.requiresCliArchive && github.token || '' }}
         run: |
           # Start heartbeat monitor in background (output goes to console directly)
+          # Use 60s interval on Windows to reduce overhead on constrained 2-core runners
           $heartbeatProcess = Start-Process -FilePath "dotnet" `
-            -ArgumentList "${{ github.workspace }}\tools\scripts\Heartbeat.cs" `
+            -ArgumentList "${{ github.workspace }}\tools\scripts\Heartbeat.cs 60" `
             -NoNewWindow -PassThru
 
           try {
@@ -442,14 +456,21 @@ jobs:
           NUGET_PACKAGES: ${{ github.workspace }}/.packages
           PLAYWRIGHT_INSTALLED: ${{ !inputs.enablePlaywrightInstall && 'false' || 'true' }}
           TESTCONTAINERS_HUB_IMAGE_NAME_PREFIX: 'netaspireci.azurecr.io'
+          # Prevent the Roslyn compiler server (VBCSCompiler) from starting during tests.
+          # On 2-core runners, VBCSCompiler consumes ~150% CPU / 700MB RAM and starves the
+          # runner agent, causing "lost communication" crashes. Projects are already pre-built,
+          # so any rebuild triggered by DCP's "dotnet run" should be minimal.
+          # See https://github.com/microsoft/aspire/issues/15832
+          UseSharedCompilation: false
           # PR metadata and token for CLI E2E tests that download artifacts from a PR
           GITHUB_PR_NUMBER: ${{ inputs.requiresCliArchive && github.event.pull_request.number || '' }}
           GITHUB_PR_HEAD_SHA: ${{ inputs.requiresCliArchive && github.event.pull_request.head.sha || '' }}
           GH_TOKEN: ${{ inputs.requiresCliArchive && github.token || '' }}
         run: |
           # Start heartbeat monitor in background (output goes to console directly)
+          # Use 60s interval on Windows to reduce overhead on constrained 2-core runners
           $heartbeatProcess = Start-Process -FilePath "${{ env.DOTNET_SCRIPT }}" `
-            -ArgumentList "${{ github.workspace }}\tools\scripts\Heartbeat.cs" `
+            -ArgumentList "${{ github.workspace }}\tools\scripts\Heartbeat.cs 60" `
             -NoNewWindow -PassThru
 
           try {