diff --git a/cpp/autobuilder/Semmle.Autobuild.Cpp.Tests/BuildScripts.cs b/cpp/autobuilder/Semmle.Autobuild.Cpp.Tests/BuildScripts.cs
index 4d3729a6aaa..963ef88d624 100644
--- a/cpp/autobuilder/Semmle.Autobuild.Cpp.Tests/BuildScripts.cs
+++ b/cpp/autobuilder/Semmle.Autobuild.Cpp.Tests/BuildScripts.cs
@@ -326,7 +326,7 @@ namespace Semmle.Autobuild.Cpp.Tests
         public void TestCppAutobuilderSuccess()
         {
             Actions.RunProcess[@"cmd.exe /C nuget restore C:\Project\test.sln -DisableParallelProcessing"] = 1;
-            Actions.RunProcess[@"cmd.exe /C C:\Project\.nuget\nuget.exe restore C:\Project\test.sln -DisableParallelProcessing"] = 0;
+            Actions.RunProcess[@"cmd.exe /C scratch\.nuget\nuget.exe restore C:\Project\test.sln -DisableParallelProcessing"] = 0;
             Actions.RunProcess[@"cmd.exe /C CALL ^""C:\Program^ Files^ ^(x86^)\Microsoft^ Visual^ Studio^ 14.0\VC\vcvarsall.bat^"" && set Platform=&& type NUL && msbuild C:\Project\test.sln /t:rebuild /p:Platform=""x86"" /p:Configuration=""Release"""] = 0;
             Actions.RunProcessOut[@"C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe -prerelease -legacy -property installationPath"] = "";
             Actions.RunProcess[@"C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe -prerelease -legacy -property installationPath"] = 1;
@@ -337,10 +337,11 @@ namespace Semmle.Autobuild.Cpp.Tests
             Actions.FileExists[@"C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\vcvarsall.bat"] = true;
             Actions.FileExists[@"C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"] = true;
             Actions.FileExists[@"C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe"] = true;
+            Actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CPP_SCRATCH_DIR"] = "scratch";
             Actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.slx";
             Actions.EnumerateDirectories[@"C:\Project"] = "";
-            Actions.CreateDirectories.Add(@"C:\Project\.nuget");
-            Actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", @"C:\Project\.nuget\nuget.exe"));
+            Actions.CreateDirectories.Add(@"scratch\.nuget");
+            Actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", @"scratch\.nuget\nuget.exe"));
 
             var autobuilder = CreateAutoBuilder(true);
             var solution = new TestSolution(@"C:\Project\test.sln");
diff --git a/csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs b/csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs
index a9cbcb3b189..7c08b68a5c8 100644
--- a/csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs
+++ b/csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs
@@ -447,6 +447,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists[@"C:\Project\test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\nbar.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
             var xml = new XmlDocument();
@@ -474,6 +475,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists[@"C:\Project/test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
             var xml = new XmlDocument();
@@ -496,6 +498,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = false;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.cs";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -561,6 +564,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -575,6 +579,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -589,6 +594,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -631,6 +637,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -647,6 +654,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.EnumerateDirectories[@"C:\Project"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.RunProcess[@"/bin/chmod u+x C:\Project/build/build.sh"] = 0;
             actions.RunProcess[@"C:\Project/build/build.sh"] = 0;
             actions.RunProcessWorkingDirectory[@"C:\Project/build/build.sh"] = @"C:\Project/build";
@@ -663,6 +671,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.EnumerateDirectories[@"C:\Project"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
 
             actions.RunProcess[@"/bin/chmod u+x C:\Project/build.sh"] = 0;
             actions.RunProcess[@"C:\Project/build.sh"] = 0;
@@ -680,6 +689,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.EnumerateDirectories[@"C:\Project"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
 
             actions.RunProcess[@"/bin/chmod u+x C:\Project/build.sh"] = 0;
             actions.RunProcess[@"C:\Project/build.sh"] = 5;
@@ -697,6 +707,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.EnumerateDirectories[@"C:\Project"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.RunProcess[@"cmd.exe /C C:\Project\build.bat"] = 0;
             actions.RunProcessWorkingDirectory[@"cmd.exe /C C:\Project\build.bat"] = @"C:\Project";
             actions.FileExists["csharp.log"] = true;
@@ -712,6 +723,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.EnumerateDirectories[@"C:\Project"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.RunProcess[@"cmd.exe /C C:\Project\build.bat"] = 1;
             actions.RunProcessWorkingDirectory[@"cmd.exe /C C:\Project\build.bat"] = @"C:\Project";
             actions.RunProcess[@"cmd.exe /C C:\codeql\tools\java\bin\java -jar C:\codeql\csharp\tools\extractor-asp.jar ."] = 0;
@@ -733,6 +745,7 @@ namespace Semmle.Autobuild.CSharp.Tests
 
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -756,6 +769,7 @@ namespace Semmle.Autobuild.CSharp.Tests
 
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest1.cs\ntest2.cs";
             actions.EnumerateFiles[@"C:\Project\.nuget"] = "nuget.exe";
             actions.EnumerateDirectories[@"C:\Project"] = @".nuget";
@@ -789,6 +803,7 @@ namespace Semmle.Autobuild.CSharp.Tests
 
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "test1.csproj\ntest2.csproj\ntest1.cs\ntest2.cs";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -829,6 +844,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists[@"C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest1.cs\ntest2.cs";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -856,6 +872,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists[@"C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest1.cs\ntest2.cs";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -877,6 +894,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["csharp.log"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.sln";
             actions.EnumerateDirectories[@"C:\Project"] = "";
 
@@ -896,6 +914,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists[@"C:\Project/test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
             var xml = new XmlDocument();
@@ -918,16 +937,17 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.RunProcess["dotnet --list-sdks"] = 0;
             actions.RunProcessOut["dotnet --list-sdks"] = "2.1.2 [C:\\Program Files\\dotnet\\sdks]\n2.1.4 [C:\\Program Files\\dotnet\\sdks]";
             actions.RunProcess[@"chmod u+x dotnet-install.sh"] = 0;
-            actions.RunProcess[@"./dotnet-install.sh --channel release --version 2.1.3 --install-dir C:\Project/.dotnet"] = 0;
+            actions.RunProcess[@"./dotnet-install.sh --channel release --version 2.1.3 --install-dir scratch/.dotnet"] = 0;
             actions.RunProcess[@"rm dotnet-install.sh"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet --info"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet clean C:\Project/test.csproj"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet restore C:\Project/test.csproj"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet build --no-incremental C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet --info"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet clean C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet restore C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet build --no-incremental C:\Project/test.csproj"] = 0;
             actions.FileExists["csharp.log"] = true;
             actions.FileExists["test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.GetEnvironmentVariable["PATH"] = "/bin:/usr/bin";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
@@ -953,16 +973,17 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.RunProcessOut["dotnet --list-sdks"] = @"2.1.3 [C:\Program Files\dotnet\sdks]
 2.1.4 [C:\Program Files\dotnet\sdks]";
             actions.RunProcess[@"chmod u+x dotnet-install.sh"] = 0;
-            actions.RunProcess[@"./dotnet-install.sh --channel release --version 2.1.3 --install-dir C:\Project/.dotnet"] = 0;
+            actions.RunProcess[@"./dotnet-install.sh --channel release --version 2.1.3 --install-dir scratch/.dotnet"] = 0;
             actions.RunProcess[@"rm dotnet-install.sh"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet --info"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet clean C:\Project/test.csproj"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet restore C:\Project/test.csproj"] = 0;
-            actions.RunProcess[@"C:\Project/.dotnet/dotnet build --no-incremental C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet --info"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet clean C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet restore C:\Project/test.csproj"] = 0;
+            actions.RunProcess[@"scratch/.dotnet/dotnet build --no-incremental C:\Project/test.csproj"] = 0;
             actions.FileExists["csharp.log"] = true;
             actions.FileExists["test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.GetEnvironmentVariable["PATH"] = "/bin:/usr/bin";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\nbar.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
@@ -986,14 +1007,15 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.RunProcess["cmd.exe /C dotnet --list-sdks"] = 0;
             actions.RunProcessOut["cmd.exe /C dotnet --list-sdks"] = "2.1.3 [C:\\Program Files\\dotnet\\sdks]\n2.1.4 [C:\\Program Files\\dotnet\\sdks]";
             action();
-            actions.RunProcess[@"cmd.exe /C C:\Project\.dotnet\dotnet --info"] = 0;
-            actions.RunProcess[@"cmd.exe /C C:\Project\.dotnet\dotnet clean C:\Project\test.csproj"] = 0;
-            actions.RunProcess[@"cmd.exe /C C:\Project\.dotnet\dotnet restore C:\Project\test.csproj"] = 0;
-            actions.RunProcess[@"cmd.exe /C C:\Project\.dotnet\dotnet build --no-incremental C:\Project\test.csproj"] = 0;
+            actions.RunProcess[@"cmd.exe /C scratch\.dotnet\dotnet --info"] = 0;
+            actions.RunProcess[@"cmd.exe /C scratch\.dotnet\dotnet clean C:\Project\test.csproj"] = 0;
+            actions.RunProcess[@"cmd.exe /C scratch\.dotnet\dotnet restore C:\Project\test.csproj"] = 0;
+            actions.RunProcess[@"cmd.exe /C scratch\.dotnet\dotnet build --no-incremental C:\Project\test.csproj"] = 0;
             actions.FileExists["csharp.log"] = true;
             actions.FileExists[@"C:\Project\test.csproj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.GetEnvironmentVariable["PATH"] = "/bin:/usr/bin";
             actions.EnumerateFiles[@"C:\Project"] = "foo.cs\ntest.cs\ntest.csproj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
@@ -1016,7 +1038,7 @@ namespace Semmle.Autobuild.CSharp.Tests
         {
             TestDotnetVersionWindows(() =>
             {
-                actions.RunProcess[@"cmd.exe /C pwsh -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir C:\Project\.dotnet"""] = 0;
+                actions.RunProcess[@"cmd.exe /C pwsh -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir scratch\.dotnet"""] = 0;
             },
             6);
         }
@@ -1026,8 +1048,8 @@ namespace Semmle.Autobuild.CSharp.Tests
         {
             TestDotnetVersionWindows(() =>
             {
-                actions.RunProcess[@"cmd.exe /C pwsh -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir C:\Project\.dotnet"""] = 1;
-                actions.RunProcess[@"cmd.exe /C powershell -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir C:\Project\.dotnet"""] = 0;
+                actions.RunProcess[@"cmd.exe /C pwsh -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir scratch\.dotnet"""] = 1;
+                actions.RunProcess[@"cmd.exe /C powershell -NoProfile -ExecutionPolicy unrestricted -Command ""[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; &([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://dot.net/v1/dotnet-install.ps1'))) -Version 2.1.3 -InstallDir scratch\.dotnet"""] = 0;
             },
             7);
         }
@@ -1036,7 +1058,7 @@ namespace Semmle.Autobuild.CSharp.Tests
         public void TestDirsProjWindows()
         {
             actions.RunProcess[@"cmd.exe /C nuget restore C:\Project\dirs.proj -DisableParallelProcessing"] = 1;
-            actions.RunProcess[@"cmd.exe /C C:\Project\.nuget\nuget.exe restore C:\Project\dirs.proj -DisableParallelProcessing"] = 0;
+            actions.RunProcess[@"cmd.exe /C scratch\.nuget\nuget.exe restore C:\Project\dirs.proj -DisableParallelProcessing"] = 0;
             actions.RunProcess["cmd.exe /C CALL ^\"C:\\Program^ Files^ ^(x86^)\\Microsoft^ Visual^ Studio^ 12.0\\VC\\vcvarsall.bat^\" && set Platform=&& type NUL && msbuild C:\\Project\\dirs.proj /t:Windows /p:Platform=\"x86\" /p:Configuration=\"Debug\" /P:Fu=Bar"] = 0;
             actions.FileExists["csharp.log"] = true;
             actions.FileExists[@"C:\Project\a\test.csproj"] = true;
@@ -1049,10 +1071,11 @@ namespace Semmle.Autobuild.CSharp.Tests
 
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "a\\test.cs\na\\test.csproj\ndirs.proj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
-            actions.CreateDirectories.Add(@"C:\Project\.nuget");
-            actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", @"C:\Project\.nuget\nuget.exe"));
+            actions.CreateDirectories.Add(@"scratch\.nuget");
+            actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", @"scratch\.nuget\nuget.exe"));
 
             var csproj = new XmlDocument();
             csproj.LoadXml(@"<?xml version=""1.0"" encoding=""utf - 8""?>
@@ -1080,17 +1103,18 @@ namespace Semmle.Autobuild.CSharp.Tests
         public void TestDirsProjLinux()
         {
             actions.RunProcess[@"nuget restore C:\Project/dirs.proj -DisableParallelProcessing"] = 1;
-            actions.RunProcess[@"mono C:\Project/.nuget/nuget.exe restore C:\Project/dirs.proj -DisableParallelProcessing"] = 0;
+            actions.RunProcess[@"mono scratch/.nuget/nuget.exe restore C:\Project/dirs.proj -DisableParallelProcessing"] = 0;
             actions.RunProcess[@"msbuild C:\Project/dirs.proj /t:rebuild"] = 0;
             actions.FileExists["csharp.log"] = true;
             actions.FileExists[@"C:\Project/a/test.csproj"] = true;
             actions.FileExists[@"C:\Project/dirs.proj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.EnumerateFiles[@"C:\Project"] = "a/test.cs\na/test.csproj\ndirs.proj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
-            actions.CreateDirectories.Add(@"C:\Project/.nuget");
-            actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", @"C:\Project/.nuget/nuget.exe"));
+            actions.CreateDirectories.Add("scratch/.nuget");
+            actions.DownloadFiles.Add(("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", "scratch/.nuget/nuget.exe"));
 
             var csproj = new XmlDocument();
             csproj.LoadXml(@"<?xml version=""1.0"" encoding=""utf - 8""?>
@@ -1119,6 +1143,7 @@ namespace Semmle.Autobuild.CSharp.Tests
             actions.FileExists["dirs.proj"] = true;
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_TRAP_DIR"] = "";
             actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SOURCE_ARCHIVE_DIR"] = "";
+            actions.GetEnvironmentVariable["CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR"] = "scratch";
             actions.FileExists["csharp.log"] = false;
             actions.EnumerateFiles[@"C:\Project"] = "dirs.proj";
             actions.EnumerateDirectories[@"C:\Project"] = "";
diff --git a/csharp/autobuilder/Semmle.Autobuild.CSharp/DotNetRule.cs b/csharp/autobuilder/Semmle.Autobuild.CSharp/DotNetRule.cs
index f7112ada31e..9dd441c5481 100644
--- a/csharp/autobuilder/Semmle.Autobuild.CSharp/DotNetRule.cs
+++ b/csharp/autobuilder/Semmle.Autobuild.CSharp/DotNetRule.cs
@@ -81,7 +81,7 @@ namespace Semmle.Autobuild.CSharp
         /// </summary>
         public static BuildScript WithDotNet(IAutobuilder<AutobuildOptionsShared> builder, Func<string?, IDictionary<string, string>?, BuildScript> f)
         {
-            var installDir = builder.Actions.PathCombine(builder.Options.RootDirectory, ".dotnet");
+            var installDir = builder.Actions.PathCombine(FileUtils.GetTemporaryWorkingDirectory(builder.Actions.GetEnvironmentVariable, builder.Options.Language.UpperCaseName, out var _), ".dotnet");
             var installScript = DownloadDotNet(builder, installDir);
             return BuildScript.Bind(installScript, installed =>
             {
diff --git a/csharp/autobuilder/Semmle.Autobuild.Shared/MsBuildRule.cs b/csharp/autobuilder/Semmle.Autobuild.Shared/MsBuildRule.cs
index 40a48cf54c4..3099449a1fb 100644
--- a/csharp/autobuilder/Semmle.Autobuild.Shared/MsBuildRule.cs
+++ b/csharp/autobuilder/Semmle.Autobuild.Shared/MsBuildRule.cs
@@ -60,7 +60,7 @@ namespace Semmle.Autobuild.Shared
             // Use `nuget.exe` from source code repo, if present, otherwise first attempt with global
             // `nuget` command, and if that fails, attempt to download `nuget.exe` from nuget.org
             var nuget = builder.GetFilename("nuget.exe").Select(t => t.Item1).FirstOrDefault() ?? "nuget";
-            var nugetDownload = builder.Actions.PathCombine(builder.Options.RootDirectory, ".nuget", "nuget.exe");
+            var nugetDownloadPath = builder.Actions.PathCombine(FileUtils.GetTemporaryWorkingDirectory(builder.Actions.GetEnvironmentVariable, builder.Options.Language.UpperCaseName, out var _), ".nuget", "nuget.exe");
             var nugetDownloaded = false;
 
             var ret = BuildScript.Success;
@@ -96,13 +96,13 @@ namespace Semmle.Autobuild.Shared
                         // If `nuget restore` fails, and we have not already attempted to download `nuget.exe`,
                         // download it and reattempt `nuget restore`.
                         var nugetDownloadAndRestore =
-                            BuildScript.Bind(DownloadNugetExe(builder, nugetDownload), exitCode =>
+                            BuildScript.Bind(DownloadNugetExe(builder, nugetDownloadPath), exitCode =>
                             {
                                 nugetDownloaded = true;
                                 if (exitCode != 0)
                                     return BuildScript.Failure;
 
-                                nuget = nugetDownload;
+                                nuget = nugetDownloadPath;
                                 return GetNugetRestoreScript();
                             });
                         ret &= BuildScript.Try(nugetRestore | nugetDownloadAndRestore | msbuildRestoreCommand.Script);
diff --git a/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyManager.cs b/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyManager.cs
index b351d25b5ec..a4320f9610c 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyManager.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyManager.cs
@@ -479,7 +479,7 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
             foreach (var b in sha.Take(8))
                 sb.AppendFormat("{0:x2}", b);
 
-            return Path.Combine(Path.GetTempPath(), "GitHub", packages, sb.ToString());
+            return Path.Combine(FileUtils.GetTemporaryWorkingDirectory(out var _), "GitHub", packages, sb.ToString());
         }
 
         /// <summary>
diff --git a/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/Razor.cs b/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/Razor.cs
index a9c8268d94b..9d910835f90 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/Razor.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/Razor.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Text;
 using System.Linq;
+using Semmle.Util;
 
 namespace Semmle.Extraction.CSharp.DependencyFetching
 {
@@ -51,7 +52,7 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
         public IEnumerable<string> GenerateFiles(IEnumerable<string> cshtmls, IEnumerable<string> references, string workingDirectory)
         {
             var name = Guid.NewGuid().ToString("N").ToUpper();
-            var tempPath = Path.GetTempPath();
+            var tempPath = FileUtils.GetTemporaryWorkingDirectory(out var _);
             var analyzerConfig = Path.Combine(tempPath, $"{name}.txt");
             var dllPath = Path.Combine(tempPath, $"{name}.dll");
             var cscArgsPath = Path.Combine(tempPath, $"{name}.rsp");
diff --git a/csharp/extractor/Semmle.Extraction/TrapWriter.cs b/csharp/extractor/Semmle.Extraction/TrapWriter.cs
index 58d71ccaf38..7f2c38466c0 100644
--- a/csharp/extractor/Semmle.Extraction/TrapWriter.cs
+++ b/csharp/extractor/Semmle.Extraction/TrapWriter.cs
@@ -48,7 +48,7 @@ namespace Semmle.Extraction
 
             writerLazy = new Lazy<StreamWriter>(() =>
             {
-                var tempPath = trap ?? Path.GetTempPath();
+                var tempPath = trap ?? FileUtils.GetTemporaryWorkingDirectory(out var _);
 
                 do
                 {
diff --git a/csharp/extractor/Semmle.Util/EnvironmentVariables.cs b/csharp/extractor/Semmle.Util/EnvironmentVariables.cs
index e6735e8741a..9dcccf6d878 100644
--- a/csharp/extractor/Semmle.Util/EnvironmentVariables.cs
+++ b/csharp/extractor/Semmle.Util/EnvironmentVariables.cs
@@ -7,8 +7,6 @@ namespace Semmle.Util
         public static string? GetExtractorOption(string name) =>
             Environment.GetEnvironmentVariable($"CODEQL_EXTRACTOR_CSHARP_OPTION_{name.ToUpper()}");
 
-        public static string? GetScratchDirectory() => Environment.GetEnvironmentVariable("CODEQL_EXTRACTOR_CSHARP_SCRATCH_DIR");
-
         public static int GetDefaultNumberOfThreads()
         {
             if (!int.TryParse(Environment.GetEnvironmentVariable("CODEQL_THREADS"), out var threads) || threads == -1)
diff --git a/csharp/extractor/Semmle.Util/FileUtils.cs b/csharp/extractor/Semmle.Util/FileUtils.cs
index 4d21bf3fde8..5cf38e6b48e 100644
--- a/csharp/extractor/Semmle.Util/FileUtils.cs
+++ b/csharp/extractor/Semmle.Util/FileUtils.cs
@@ -144,10 +144,10 @@ namespace Semmle.Util
             return nested;
         }
 
-        public static string GetTemporaryWorkingDirectory(out bool shouldCleanUp)
+        public static string GetTemporaryWorkingDirectory(Func<string, string?> getEnvironmentVariable, string lang, out bool shouldCleanUp)
         {
             shouldCleanUp = false;
-            var tempFolder = EnvironmentVariables.GetScratchDirectory();
+            var tempFolder = getEnvironmentVariable($"CODEQL_EXTRACTOR_{lang}_SCRATCH_DIR");
 
             if (string.IsNullOrEmpty(tempFolder))
             {
@@ -160,6 +160,9 @@ namespace Semmle.Util
             return tempFolder;
         }
 
+        public static string GetTemporaryWorkingDirectory(out bool shouldCleanUp) =>
+            GetTemporaryWorkingDirectory(Environment.GetEnvironmentVariable, "CSHARP", out shouldCleanUp);
+
         public static FileInfo CreateTemporaryFile(string extension, out bool shouldCleanUpContainingFolder)
         {
             var tempFolder = GetTemporaryWorkingDirectory(out shouldCleanUpContainingFolder);