dotnet · Copilot · Nov 29, 2025 · Nov 29, 2025
diff --git a/.devcontainer/android/devcontainer.json b/.devcontainer/android/devcontainer.json
@@ -55,8 +55,7 @@
 	// This allows developers to just use 'dotnet build' on the command-line, and the local dotnet version will be used.
     // Add the Android SDK tooling and emulator to the path.
 	"remoteEnv": {
-		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:ANDROID_SDK_ROOT}/cmdline-tools/cmdline-tools/bin:${containerEnv:ANDROID_SDK_ROOT}/emulator:${containerEnv:ANDROID_SDK_ROOT}/platform-tools:${containerEnv:PATH}",
-		"DOTNET_MULTILEVEL_LOOKUP": "0"
+		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:ANDROID_SDK_ROOT}/cmdline-tools/cmdline-tools/bin:${containerEnv:ANDROID_SDK_ROOT}/emulator:${containerEnv:ANDROID_SDK_ROOT}/platform-tools:${containerEnv:PATH}"
 	},
 
 	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.

diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
@@ -40,8 +40,7 @@
 	// Add the locally installed dotnet to the path to ensure that it is activated
 	// This allows developers to just use 'dotnet build' on the command-line, and the local dotnet version will be used.
 	"remoteEnv": {
-		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:PATH}",
-		"DOTNET_MULTILEVEL_LOOKUP": "0"
+		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:PATH}"
 	},
 
 	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.

diff --git a/.devcontainer/libraries/devcontainer.json b/.devcontainer/libraries/devcontainer.json
@@ -46,8 +46,7 @@
 	// Add the locally installed dotnet to the path to ensure that it is activated
 	// This allows developers to just use 'dotnet build' on the command-line, and the local dotnet version will be used.
 	"remoteEnv": {
-		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:PATH}",
-		"DOTNET_MULTILEVEL_LOOKUP": "0"
+		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerEnv:PATH}"
 	},
 
 	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.

diff --git a/.devcontainer/wasm-multiThreaded/devcontainer.json b/.devcontainer/wasm-multiThreaded/devcontainer.json
@@ -47,8 +47,7 @@
 	// This allows developers to just use 'dotnet build' on the command-line, and the local dotnet version will be used.
 	// Add the global tools dir to the PATH so that globally installed tools will work
 	"remoteEnv": {
-		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerWorkspaceFolder}/.dotnet-tools-global:${containerEnv:PATH}",
-		"DOTNET_MULTILEVEL_LOOKUP": "0",
+		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerWorkspaceFolder}/.dotnet-tools-global:${containerEnv:PATH}"
 	},
 
 	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.

diff --git a/.devcontainer/wasm/devcontainer.json b/.devcontainer/wasm/devcontainer.json
@@ -47,8 +47,7 @@
 	// This allows developers to just use 'dotnet build' on the command-line, and the local dotnet version will be used.
 	// Add the global tools dir to the PATH so that globally installed tools will work
 	"remoteEnv": {
-		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerWorkspaceFolder}/.dotnet-tools-global:${containerEnv:PATH}",
-		"DOTNET_MULTILEVEL_LOOKUP": "0",
+		"PATH": "${containerWorkspaceFolder}/.dotnet:${containerWorkspaceFolder}/.dotnet-tools-global:${containerEnv:PATH}"
 	},
 
 	// Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.

diff --git a/dotnet.cmd b/dotnet.cmd
@@ -13,9 +13,6 @@ set /p dotnetPath=<%~dp0artifacts\toolset\sdk.txt
 :: misleading value (such as 'MCD' in HP PCs) may lead to build breakage (issue: #69).
 set Platform=
 
-:: Don't resolve runtime, shared framework, or SDK from other locations to ensure build determinism
-set DOTNET_MULTILEVEL_LOOKUP=0
-
 :: Suppress the .NET startup banner
 set DOTNET_NOLOGO=1
 

diff --git a/dotnet.sh b/dotnet.sh
@@ -12,9 +12,6 @@ while [[ -h $source ]]; do
 done
 scriptroot="$( cd -P "$( dirname "$source" )" && pwd )"
 
-# Don't resolve runtime, shared framework, or SDK from other locations to ensure build determinism
-export DOTNET_MULTILEVEL_LOOKUP=0
-
 # Suppress the .NET startup banner
 export DOTNET_NOLOGO=1
 

diff --git a/eng/build.ps1 b/eng/build.ps1
@@ -259,9 +259,6 @@ if ($vs) {
   # This tells MSBuild to load the SDK from the directory of the bootstrapped SDK
   $env:DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=$env:DOTNET_ROOT
 
-  # This tells .NET Core not to go looking for .NET Core in other places
-  $env:DOTNET_MULTILEVEL_LOOKUP=0;
-
   # Put our local dotnet.exe on PATH first so Visual Studio knows which one to use
   $env:PATH=($env:DOTNET_ROOT + ";" + $env:PATH);
 

diff --git a/eng/common/tools.ps1 b/eng/common/tools.ps1
@@ -157,9 +157,6 @@ function InitializeDotNetCli([bool]$install, [bool]$createSdkLocationFile) {
     return $global:_DotNetInstallDir
   }
 
-  # Don't resolve runtime, shared framework, or SDK from other locations to ensure build determinism
-  $env:DOTNET_MULTILEVEL_LOOKUP=0
-
   # Disable first run since we do not need all ASP.NET packages restored.
   $env:DOTNET_NOLOGO=1
 
@@ -225,7 +222,6 @@ function InitializeDotNetCli([bool]$install, [bool]$createSdkLocationFile) {
   # Make Sure that our bootstrapped dotnet cli is available in future steps of the Azure Pipelines build
   Write-PipelinePrependPath -Path $dotnetRoot
 
-  Write-PipelineSetVariable -Name 'DOTNET_MULTILEVEL_LOOKUP' -Value '0'
   Write-PipelineSetVariable -Name 'DOTNET_NOLOGO' -Value '1'
 
   return $global:_DotNetInstallDir = $dotnetRoot

diff --git a/eng/common/tools.sh b/eng/common/tools.sh
@@ -115,9 +115,6 @@ function InitializeDotNetCli {
 
   local install=$1
 
-  # Don't resolve runtime, shared framework, or SDK from other locations to ensure build determinism
-  export DOTNET_MULTILEVEL_LOOKUP=0
-
   # Disable first run since we want to control all package sources
   export DOTNET_NOLOGO=1
 
@@ -166,7 +163,6 @@ function InitializeDotNetCli {
   # build steps from using anything other than what we've downloaded.
   Write-PipelinePrependPath -path "$dotnet_root"
 
-  Write-PipelineSetVariable -name "DOTNET_MULTILEVEL_LOOKUP" -value "0"
   Write-PipelineSetVariable -name "DOTNET_NOLOGO" -value "1"
 
   # return value

diff --git a/eng/pipelines/common/macos-sign-with-entitlements.yml b/eng/pipelines/common/macos-sign-with-entitlements.yml
@@ -58,7 +58,6 @@ steps:
       MaxRetryAttempts: '5'
       PendingAnalysisWaitTimeoutMinutes: '5'
     env:
-      DOTNET_MULTILEVEL_LOOKUP: 0
       DOTNET_ROOT: '$(Agent.TempDirectory)/dotnet'
       DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR: '$(Agent.TempDirectory)/dotnet'
 

diff --git a/eng/testing/RunnerTemplate.cmd b/eng/testing/RunnerTemplate.cmd
@@ -41,9 +41,6 @@ set EXECUTION_DIR=%~dp0
 
 :argparser_end
 
-:: Don't use a globally installed SDK.
-set DOTNET_MULTILEVEL_LOOKUP=0
-
 :: Assume failure
 set HAS_TEST_RESULTS=0
 

diff --git a/eng/testing/RunnerTemplate.sh b/eng/testing/RunnerTemplate.sh
@@ -45,9 +45,6 @@ if [[ -z "$RUNTIME_PATH" ]]; then
   exit -1
 fi
 
-# Don't use a globally installed SDK.
-export DOTNET_MULTILEVEL_LOOKUP=0
-
 exitcode_list[0]="Exited Successfully"
 exitcode_list[130]="SIGINT  Ctrl-C occurred. Likely tests timed out."
 exitcode_list[131]="SIGQUIT Ctrl-\ occurred. Core dumped."

diff --git a/src/coreclr/scripts/superpmi_aspnet.py b/src/coreclr/scripts/superpmi_aspnet.py
@@ -137,7 +137,6 @@ def build_and_run(coreclr_args):
 
         # install dotnet 8.0
         run_command([dotnet_install_script_path, "-Version", "8.0.0"], temp_location, _exit_on_fail=True)
-        os.environ['DOTNET_MULTILEVEL_LOOKUP'] = '0'
         os.environ['DOTNET_NOLOGO'] = '1'
         dotnet_path = path.join(source_directory, ".dotnet")
         dotnet_exe = path.join(dotnet_path, "dotnet.exe") if is_windows else path.join(dotnet_path, "dotnet")

diff --git a/src/coreclr/scripts/superpmi_aspnet2.py b/src/coreclr/scripts/superpmi_aspnet2.py
@@ -150,7 +150,6 @@ def setup_and_run_crank_agent(workdir: Path):
     dotnet_root_dir = dotnethome_dir
     os.environ['DOTNET_ROOT'] = str(dotnet_root_dir)
     os.environ['DOTNET_CLI_TELEMETRY_OPTOUT'] = '1'
-    os.environ['DOTNET_MULTILEVEL_LOOKUP'] = '0'
     os.environ['UseSharedCompilation'] = 'false'
 
     print("Installing tools ...")

diff --git a/src/libraries/Common/tests/System/Net/StressTests/build-local.ps1 b/src/libraries/Common/tests/System/Net/StressTests/build-local.ps1
@@ -57,7 +57,6 @@ if (-not (Test-Path -Path $DailyDotnetRoot)) {
 
 $env:DOTNET_ROOT=$DailyDotnetRoot
 $env:PATH="$DailyDotnetRoot;$env:PATH"
-$env:DOTNET_MULTILEVEL_LOOKUP=0
 
 if (-not (Test-Path -Path "$TestHostRoot/shared/Microsoft.AspNetCore.App")) {
     Write-Host "Copying Microsoft.AspNetCore.App bits from daily SDK to testhost: $TestHostRoot"

diff --git a/src/libraries/Common/tests/System/Net/StressTests/build-local.sh b/src/libraries/Common/tests/System/Net/StressTests/build-local.sh
@@ -56,7 +56,6 @@ fi
 
 export DOTNET_ROOT=$daily_dotnet_root
 export PATH=$DOTNET_ROOT:$PATH
-export DOTNET_MULTILEVEL_LOOKUP=0
 
 if [[ ! -d "$testhost_root/shared/Microsoft.AspNetCore.App" ]]; then
     echo "Copying Microsoft.AspNetCore.App bits from daily SDK to testhost: $testhost_root"

diff --git a/src/libraries/System.Net.Http/tests/StressTests/HttpStress/load-corefx-testhost.ps1 b/src/libraries/System.Net.Http/tests/StressTests/HttpStress/load-corefx-testhost.ps1
@@ -138,11 +138,10 @@ function Set-Sdk-Environment()
     }
 
     $pathSeparator=if($os -eq "windows") { ";" } else { ":" }
-    
+
     $env:DOTNET_ROOT=$candidate_path
     $env:DOTNET_CLI_HOME=$candidate_path
     $env:PATH=($candidate_path + $pathSeparator + $env:PATH)
-    $env:DOTNET_MULTILEVEL_LOOKUP=0
     $env:DOTNET_ROLL_FORWARD_ON_NO_CANDIDATE_FX=2
 }
 

@@ -123,7 +123,6 @@ public BuildEnvironment()
             // dotnet
             EnvVars["DOTNET_ROOT"] = sdkForWorkloadPath;
             EnvVars["DOTNET_INSTALL_DIR"] = sdkForWorkloadPath;
-            EnvVars["DOTNET_MULTILEVEL_LOOKUP"] = "0";
             EnvVars["DOTNET_NOLOGO"] = "1";
             EnvVars["PATH"] = $"{sdkForWorkloadPath}{Path.PathSeparator}{Environment.GetEnvironmentVariable("PATH")}";
             EnvVars["EM_WORKAROUND_PYTHON_BUG_34780"] = "1";

@@ -13,7 +13,6 @@ public RunCommand(BuildEnvironment buildEnv, ITestOutputHelper _testOutput, stri
         WithEnvironmentVariables(buildEnv.EnvVars);
         WithEnvironmentVariable("DOTNET_ROOT", Path.GetDirectoryName(buildEnv.DotNet)!);
         WithEnvironmentVariable("DOTNET_INSTALL_DIR", Path.GetDirectoryName(buildEnv.DotNet)!);
-        WithEnvironmentVariable("DOTNET_MULTILEVEL_LOOKUP", "0");
         WithEnvironmentVariable("DOTNET_NOLOGO", "1");
     }
 }
@@ -164,7 +164,6 @@ private Process CreateProcess(string executable, string args)
                 UseShellExecute = false
             };
 
-            psi.Environment["DOTNET_MULTILEVEL_LOOKUP"] = "0";
             psi.Environment["DOTNET_NOLOGO"] = "1";
 
             // runtime repo sets this, which interferes with the tests