diff --git a/eng/Version.Details.props b/eng/Version.Details.props
index 5d373d67395..654db42b289 100644
--- a/eng/Version.Details.props
+++ b/eng/Version.Details.props
@@ -24,8 +24,8 @@ This file should be imported by eng/Versions.props
     <SystemThreadingChannelsPackageVersion>9.0.11</SystemThreadingChannelsPackageVersion>
     <SystemThreadingTasksDataflowPackageVersion>9.0.11</SystemThreadingTasksDataflowPackageVersion>
     <!-- dotnet/arcade dependencies -->
-    <MicrosoftDotNetArcadeSdkPackageVersion>10.0.0-beta.26080.4</MicrosoftDotNetArcadeSdkPackageVersion>
-    <MicrosoftDotNetXUnitExtensionsPackageVersion>10.0.0-beta.26080.4</MicrosoftDotNetXUnitExtensionsPackageVersion>
+    <MicrosoftDotNetArcadeSdkPackageVersion>10.0.0-beta.26123.2</MicrosoftDotNetArcadeSdkPackageVersion>
+    <MicrosoftDotNetXUnitExtensionsPackageVersion>10.0.0-beta.26123.2</MicrosoftDotNetXUnitExtensionsPackageVersion>
     <!-- nuget/nuget.client dependencies -->
     <NuGetBuildTasksPackageVersion>7.3.0-preview.1.50</NuGetBuildTasksPackageVersion>
     <!-- dotnet/roslyn dependencies -->
diff --git a/eng/Version.Details.xml b/eng/Version.Details.xml
index 65187b99cf2..ab32998019a 100644
--- a/eng/Version.Details.xml
+++ b/eng/Version.Details.xml
@@ -106,9 +106,9 @@
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>
-    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="10.0.0-beta.26080.4">
+    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="10.0.0-beta.26123.2">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>b0f891cf7c1febc0ebbae7dd787f8a0b4c0cbc95</Sha>
+      <Sha>4d898652733deb7dd274237ac06d27ee2ad85b36</Sha>
     </Dependency>
     <Dependency Name="NuGet.Build.Tasks" Version="7.3.0-preview.1.50">
       <Uri>https://github.com/nuget/nuget.client</Uri>
@@ -118,9 +118,9 @@
       <Uri>https://github.com/dotnet/roslyn</Uri>
       <Sha>df7b5aaff073486376dad5d30b6d0ba45595d97d</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.XUnitExtensions" Version="10.0.0-beta.26080.4">
+    <Dependency Name="Microsoft.DotNet.XUnitExtensions" Version="10.0.0-beta.26123.2">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>b0f891cf7c1febc0ebbae7dd787f8a0b4c0cbc95</Sha>
+      <Sha>4d898652733deb7dd274237ac06d27ee2ad85b36</Sha>
     </Dependency>
   </ToolsetDependencies>
 </Dependencies>
diff --git a/eng/Versions.props b/eng/Versions.props
index 98d34e9be7f..98bac6d94f6 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -3,7 +3,7 @@
   <Import Project="Version.Details.props" />
 
   <PropertyGroup>
-    <VersionPrefix>18.3.3</VersionPrefix><DotNetFinalVersionKind>release</DotNetFinalVersionKind> <!-- Keep next to VersionPrefix to create a conflict in forward-flow -->
+    <VersionPrefix>18.3.4</VersionPrefix><DotNetFinalVersionKind>release</DotNetFinalVersionKind> <!-- Keep next to VersionPrefix to create a conflict in forward-flow -->
     <PreReleaseVersionLabel>servicing</PreReleaseVersionLabel>
     <PackageValidationBaselineVersion>18.0.2</PackageValidationBaselineVersion>
     <AssemblyVersion>15.1.0.0</AssemblyVersion>
diff --git a/eng/common/core-templates/job/source-build.yml b/eng/common/core-templates/job/source-build.yml
index 4cb769473f7..1997c2ae00d 100644
--- a/eng/common/core-templates/job/source-build.yml
+++ b/eng/common/core-templates/job/source-build.yml
@@ -60,19 +60,19 @@ jobs:
       pool:
         ${{ if eq(variables['System.TeamProject'], 'public') }}:
           name: $[replace(replace(eq(contains(coalesce(variables['System.PullRequest.TargetBranch'], variables['Build.SourceBranch'], 'refs/heads/main'), 'release'), 'true'), True, 'NetCore-Svc-Public' ), False, 'NetCore-Public')]
-          demands: ImageOverride -equals Azure-Linux-3-Amd64-Public
+          demands: ImageOverride -equals build.azurelinux.3.amd64.open
         ${{ if eq(variables['System.TeamProject'], 'internal') }}:
           name: $[replace(replace(eq(contains(coalesce(variables['System.PullRequest.TargetBranch'], variables['Build.SourceBranch'], 'refs/heads/main'), 'release'), 'true'), True, 'NetCore1ESPool-Svc-Internal'), False, 'NetCore1ESPool-Internal')]
-          image: Azure-Linux-3-Amd64
+          image: build.azurelinux.3.amd64
           os: linux
     ${{ else }}:
       pool:
         ${{ if eq(variables['System.TeamProject'], 'public') }}:
           name: $[replace(replace(eq(contains(coalesce(variables['System.PullRequest.TargetBranch'], variables['Build.SourceBranch'], 'refs/heads/main'), 'release'), 'true'), True, 'NetCore-Svc-Public' ), False, 'NetCore-Public')]
-          demands: ImageOverride -equals Azure-Linux-3-Amd64-Public
+          demands: ImageOverride -equals build.azurelinux.3.amd64.open
         ${{ if eq(variables['System.TeamProject'], 'internal') }}:
           name: $[replace(replace(eq(contains(coalesce(variables['System.PullRequest.TargetBranch'], variables['Build.SourceBranch'], 'refs/heads/main'), 'release'), 'true'), True, 'NetCore1ESPool-Svc-Internal'), False, 'NetCore1ESPool-Internal')]
-          demands: ImageOverride -equals Azure-Linux-3-Amd64
+          demands: ImageOverride -equals build.azurelinux.3.amd64
   ${{ if ne(parameters.platform.pool, '') }}:
     pool: ${{ parameters.platform.pool }}
 
diff --git a/eng/common/templates/steps/vmr-sync.yml b/eng/common/templates/steps/vmr-sync.yml
index 599afb6186b..eb619c50268 100644
--- a/eng/common/templates/steps/vmr-sync.yml
+++ b/eng/common/templates/steps/vmr-sync.yml
@@ -38,27 +38,6 @@ steps:
   displayName: Label PR commit
   workingDirectory: $(Agent.BuildDirectory)/repo
 
-- script: |
-    vmr_sha=$(grep -oP '(?<=Sha=")[^"]*' $(Agent.BuildDirectory)/repo/eng/Version.Details.xml)
-    echo "##vso[task.setvariable variable=vmr_sha]$vmr_sha"
-  displayName: Obtain the vmr sha from Version.Details.xml (Unix)
-  condition: ne(variables['Agent.OS'], 'Windows_NT')
-  workingDirectory: $(Agent.BuildDirectory)/repo
-
-- powershell: |
-    [xml]$xml = Get-Content -Path $(Agent.BuildDirectory)/repo/eng/Version.Details.xml
-    $vmr_sha = $xml.SelectSingleNode("//Source").Sha
-    Write-Output "##vso[task.setvariable variable=vmr_sha]$vmr_sha"
-  displayName: Obtain the vmr sha from Version.Details.xml (Windows)
-  condition: eq(variables['Agent.OS'], 'Windows_NT')
-  workingDirectory: $(Agent.BuildDirectory)/repo
-
-- script: |
-    git fetch --all
-    git checkout $(vmr_sha)
-  displayName: Checkout VMR at correct sha for repo flow
-  workingDirectory: ${{ parameters.vmrPath }}
-
 - script: |
     git config --global user.name "dotnet-maestro[bot]"
     git config --global user.email "dotnet-maestro[bot]@users.noreply.github.com"
diff --git a/eng/common/templates/vmr-build-pr.yml b/eng/common/templates/vmr-build-pr.yml
index ce3c29a62fa..2f3694fa132 100644
--- a/eng/common/templates/vmr-build-pr.yml
+++ b/eng/common/templates/vmr-build-pr.yml
@@ -34,6 +34,7 @@ resources:
     type: github
     name: dotnet/dotnet
     endpoint: dotnet
+    ref: refs/heads/main # Set to whatever VMR branch the PR build should insert into
 
 stages:
 - template: /eng/pipelines/templates/stages/vmr-build.yml@vmr
diff --git a/eng/common/tools.ps1 b/eng/common/tools.ps1
index 049fe6db994..977a2d4b103 100644
--- a/eng/common/tools.ps1
+++ b/eng/common/tools.ps1
@@ -824,6 +824,11 @@ function MSBuild-Core() {
 
   $cmdArgs = "$($buildTool.Command) /m /nologo /clp:Summary /v:$verbosity /nr:$nodeReuse /p:ContinuousIntegrationBuild=$ci"
 
+  # Add -mt flag for MSBuild multithreaded mode if enabled via environment variable
+  if ($env:MSBUILD_MT_ENABLED -eq "1") {
+    $cmdArgs += ' -mt'
+  }
+
   if ($warnAsError) {
     $cmdArgs += ' /warnaserror /p:TreatWarningsAsErrors=true'
   }
diff --git a/eng/common/tools.sh b/eng/common/tools.sh
index c1841c9dfd0..1b296f646c2 100755
--- a/eng/common/tools.sh
+++ b/eng/common/tools.sh
@@ -526,7 +526,13 @@ function MSBuild-Core {
     }
   }
 
-  RunBuildTool "$_InitializeBuildToolCommand" /m /nologo /clp:Summary /v:$verbosity /nr:$node_reuse $warnaserror_switch /p:TreatWarningsAsErrors=$warn_as_error /p:ContinuousIntegrationBuild=$ci "$@"
+  # Add -mt flag for MSBuild multithreaded mode if enabled via environment variable
+  local mt_switch=""
+  if [[ "${MSBUILD_MT_ENABLED:-}" == "1" ]]; then
+    mt_switch="-mt"
+  fi
+
+  RunBuildTool "$_InitializeBuildToolCommand" /m /nologo /clp:Summary /v:$verbosity /nr:$node_reuse $warnaserror_switch $mt_switch /p:TreatWarningsAsErrors=$warn_as_error /p:ContinuousIntegrationBuild=$ci "$@"
 }
 
 function GetDarc {
diff --git a/eng/common/vmr-sync.ps1 b/eng/common/vmr-sync.ps1
index 97302f3205b..b37992d91cf 100644
--- a/eng/common/vmr-sync.ps1
+++ b/eng/common/vmr-sync.ps1
@@ -103,12 +103,20 @@ Set-StrictMode -Version Latest
 Highlight 'Installing .NET, preparing the tooling..'
 . .\eng\common\tools.ps1
 $dotnetRoot = InitializeDotNetCli -install:$true
+$env:DOTNET_ROOT = $dotnetRoot
 $darc = Get-Darc
-$dotnet = "$dotnetRoot\dotnet.exe"
 
 Highlight "Starting the synchronization of VMR.."
 
 # Synchronize the VMR
+$versionDetailsPath = Resolve-Path (Join-Path $PSScriptRoot '..\Version.Details.xml') | Select-Object -ExpandProperty Path
+[xml]$versionDetails = Get-Content -Path $versionDetailsPath
+$repoName = $versionDetails.SelectSingleNode('//Source').Mapping
+if (-not $repoName) {
+  Fail "Failed to resolve repo mapping from $versionDetailsPath"
+  exit 1
+}
+
 $darcArgs = (
   "vmr", "forwardflow",
   "--tmp", $tmpDir,
@@ -130,9 +138,27 @@ if ($LASTEXITCODE -eq 0) {
   Highlight "Synchronization succeeded"
 }
 else {
-  Fail "Synchronization of repo to VMR failed!"
-  Fail "'$vmrDir' is left in its last state (re-run of this script will reset it)."
-  Fail "Please inspect the logs which contain path to the failing patch file (use -debugOutput to get all the details)."
-  Fail "Once you make changes to the conflicting VMR patch, commit it locally and re-run this script."
-  exit 1
+  Highlight "Failed to flow code into the local VMR. Falling back to resetting the VMR to match repo contents..."
+  git -C $vmrDir reset --hard
+
+  $resetArgs = (
+    "vmr", "reset",
+    "${repoName}:HEAD",
+    "--vmr", $vmrDir,
+    "--tmp", $tmpDir,
+    "--additional-remotes", "${repoName}:${repoRoot}"
+  )
+
+  & "$darc" $resetArgs
+
+  if ($LASTEXITCODE -eq 0) {
+    Highlight "Successfully reset the VMR using 'darc vmr reset'"
+  }
+  else {
+    Fail "Synchronization of repo to VMR failed!"
+    Fail "'$vmrDir' is left in its last state (re-run of this script will reset it)."
+    Fail "Please inspect the logs which contain path to the failing patch file (use -debugOutput to get all the details)."
+    Fail "Once you make changes to the conflicting VMR patch, commit it locally and re-run this script."
+    exit 1
+  }
 }
diff --git a/eng/common/vmr-sync.sh b/eng/common/vmr-sync.sh
index 44239e331c0..198caec59bd 100644
--- a/eng/common/vmr-sync.sh
+++ b/eng/common/vmr-sync.sh
@@ -186,6 +186,13 @@ fi
 
 # Synchronize the VMR
 
+version_details_path=$(cd "$scriptroot/.."; pwd -P)/Version.Details.xml
+repo_name=$(grep -m 1 '<Source ' "$version_details_path" | sed -n 's/.*Mapping="\([^"]*\)".*/\1/p')
+if [[ -z "$repo_name" ]]; then
+  fail "Failed to resolve repo mapping from $version_details_path"
+  exit 1
+fi
+
 export DOTNET_ROOT="$dotnetDir"
 
 "$darc_tool" vmr forwardflow \
@@ -199,9 +206,22 @@ export DOTNET_ROOT="$dotnetDir"
 if [[ $? == 0 ]]; then
   highlight "Synchronization succeeded"
 else
-  fail "Synchronization of repo to VMR failed!"
-  fail "'$vmr_dir' is left in its last state (re-run of this script will reset it)."
-  fail "Please inspect the logs which contain path to the failing patch file (use --debug to get all the details)."
-  fail "Once you make changes to the conflicting VMR patch, commit it locally and re-run this script."
-  exit 1
+  highlight "Failed to flow code into the local VMR. Falling back to resetting the VMR to match repo contents..."
+  git -C "$vmr_dir" reset --hard
+
+  "$darc_tool" vmr reset \
+    "$repo_name:HEAD"                              \
+    --vmr "$vmr_dir"                               \
+    --tmp "$tmp_dir"                               \
+    --additional-remotes "$repo_name:$repo_root"
+
+  if [[ $? == 0 ]]; then
+    highlight "Successfully reset the VMR using 'darc vmr reset'"
+  else
+    fail "Synchronization of repo to VMR failed!"
+    fail "'$vmr_dir' is left in its last state (re-run of this script will reset it)."
+    fail "Please inspect the logs which contain path to the failing patch file (use --debug to get all the details)."
+    fail "Once you make changes to the conflicting VMR patch, commit it locally and re-run this script."
+    exit 1
+  fi
 fi
diff --git a/global.json b/global.json
index fcc32e90e26..6ec5cbd44b6 100644
--- a/global.json
+++ b/global.json
@@ -14,6 +14,6 @@
     "xcopy-msbuild": "18.0.0"
   },
   "msbuild-sdks": {
-    "Microsoft.DotNet.Arcade.Sdk": "10.0.0-beta.26080.4"
+    "Microsoft.DotNet.Arcade.Sdk": "10.0.0-beta.26123.2"
   }
 }