diff --git a/prepare_3rdParty.bat b/prepare_3rdParty.bat
index 43dfc84e0..f6f31a2b6 100644
--- a/prepare_3rdParty.bat
+++ b/prepare_3rdParty.bat
@@ -29,11 +29,11 @@ IF EXIST ".\3rdParty\gc\x64\%BUILD%\lib\gc.lib" (
 ) ELSE (
   cd %p%
   echo "Downloading BDWGC"
-  curl -o gc-%GC_VER%.tar.gz https://github.com/bdwgc/bdwgc/releases/download/v%GC_VER%/gc-%GC_VER%.tar.gz
+  curl -o gc-%GC_VER%.tar.gz -L https://github.com/bdwgc/bdwgc/releases/download/v%GC_VER%/gc-%GC_VER%.tar.gz
   echo "Opening TAR.GZ BDWGC"  
   tar -xvzf gc-%GC_VER%.tar.gz -C ./3rdParty/
   echo "Downloading Libatomic_ops"
-  curl -o libatomic_ops-%LIBATOMIC_OPS_VER%.tar.gz https://github.com/bdwgc/libatomic_ops/releases/download/v%LIBATOMIC_OPS_VER%/libatomic_ops-%LIBATOMIC_OPS_VER%.tar.gz
+  curl -o libatomic_ops-%LIBATOMIC_OPS_VER%.tar.gz -L https://github.com/bdwgc/libatomic_ops/releases/download/v%LIBATOMIC_OPS_VER%/libatomic_ops-%LIBATOMIC_OPS_VER%.tar.gz
   echo "Opening TAR.GZ Libatomic_ops"  
   tar -xvzf libatomic_ops-%LIBATOMIC_OPS_VER%.tar.gz -C ./3rdParty/
   echo "Copy to gc-%GC_VER%/libatomic_ops"  
diff --git a/scripts/build_gc_debug.sh b/scripts/build_gc_debug.sh
index 190633be4..1d0fec1aa 100755
--- a/scripts/build_gc_debug.sh
+++ b/scripts/build_gc_debug.sh
@@ -2,6 +2,6 @@
 mkdir -p __build/gc/ninja/debug
 mkdir -p 3rdParty/gc/debug
 cd __build/gc/ninja/debug
-cmake ../../../../3rdParty/gc-8.2.8 -G "Ninja" -DCMAKE_BUILD_TYPE=Debug -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/debug -Denable_threads=ON -Denable_cplusplus=OFF
+cmake ../../../../3rdParty/gc-8.2.12 -G "Ninja" -DCMAKE_BUILD_TYPE=Debug -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/debug -Denable_threads=ON -Denable_cplusplus=OFF
 cmake --build . --config Debug -j 16
 cmake --install . --config Debug
diff --git a/scripts/build_gc_debug_ninja.bat b/scripts/build_gc_debug_ninja.bat
index f97fc87b2..6302d4353 100644
--- a/scripts/build_gc_debug_ninja.bat
+++ b/scripts/build_gc_debug_ninja.bat
@@ -1,7 +1,7 @@
 pushd
 mkdir __build\gc\ninja\debug
 cd __build\gc\ninja\debug
-cmake ../../../../3rdParty/gc-8.2.8 -G "Ninja" -DCMAKE_BUILD_TYPE=Debug -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/debug -Denable_threads=ON -Denable_cplusplus=OFF
+cmake ../../../../3rdParty/gc-8.2.12 -G "Ninja" -DCMAKE_BUILD_TYPE=Debug -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/debug -Denable_threads=ON -Denable_cplusplus=OFF
 cmake --build . --config Debug -j 8
 cmake --install . --config Debug
 popd
\ No newline at end of file
diff --git a/scripts/build_gc_debug_vs.bat b/scripts/build_gc_debug_vs.bat
index 494c6bfbc..faeb45d26 100644
--- a/scripts/build_gc_debug_vs.bat
+++ b/scripts/build_gc_debug_vs.bat
@@ -1,7 +1,7 @@
 pushd
 mkdir __build\gc\msbuild\x64\debug
 cd __build\gc\msbuild\x64\debug
-cmake ../../../../../3rdParty/gc-8.2.8 -G "Visual Studio 18 2026" -A x64 %EXTRA_PARAM% -DCMAKE_BUILD_TYPE=Debug -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_INSTALL_PREFIX=../../../../../3rdParty/gc/x64/debug -Denable_threads=ON -Denable_cplusplus=OFF -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreadedDebug
+cmake ../../../../../3rdParty/gc-8.2.12 -G "Visual Studio 18 2026" -A x64 %EXTRA_PARAM% -DCMAKE_BUILD_TYPE=Debug -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_INSTALL_PREFIX=../../../../../3rdParty/gc/x64/debug -Denable_threads=ON -Denable_cplusplus=OFF -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreadedDebug
 cmake --build . --config Debug -j 20
 cmake --install . --config Debug
 popd
\ No newline at end of file
diff --git a/scripts/build_gc_release.sh b/scripts/build_gc_release.sh
index 450fe04c6..44eb9416d 100755
--- a/scripts/build_gc_release.sh
+++ b/scripts/build_gc_release.sh
@@ -2,6 +2,6 @@
 mkdir -p __build/gc/ninja/release
 mkdir -p 3rdParty/gc/release
 cd __build/gc/ninja/release
-cmake ../../../../3rdParty/gc-8.2.8 -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/release -Denable_threads=ON -Denable_cplusplus=OFF
+cmake ../../../../3rdParty/gc-8.2.12 -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/release -Denable_threads=ON -Denable_cplusplus=OFF
 cmake --build . --config Release -j 16
 cmake --install . --config Release
diff --git a/scripts/build_gc_release_ninja.bat b/scripts/build_gc_release_ninja.bat
index 5dabb840d..2543751c6 100644
--- a/scripts/build_gc_release_ninja.bat
+++ b/scripts/build_gc_release_ninja.bat
@@ -1,7 +1,7 @@
 pushd
 mkdir __build\gc\ninja\release
 cd __build\gc\ninja\release
-cmake ../../../../3rdParty/gc-8.2.8 -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/release -Denable_threads=ON -Denable_cplusplus=OFF
+cmake ../../../../3rdParty/gc-8.2.12 -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_INSTALL_PREFIX=../../../../3rdParty/gc/release -Denable_threads=ON -Denable_cplusplus=OFF
 cmake --build . --config Release -j 8
 cmake --install . --config Release
 popd
\ No newline at end of file
diff --git a/scripts/build_gc_release_vs.bat b/scripts/build_gc_release_vs.bat
index ba57a2fb4..fb3545916 100644
--- a/scripts/build_gc_release_vs.bat
+++ b/scripts/build_gc_release_vs.bat
@@ -1,7 +1,7 @@
 pushd
 mkdir __build\gc\msbuild\x64\release
 cd __build\gc\msbuild\x64\release
-cmake ../../../../../3rdParty/gc-8.2.8 -G "Visual Studio 18 2026" -A x64 %EXTRA_PARAM% -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_INSTALL_PREFIX=../../../../../3rdParty/gc/x64/release -Denable_threads=ON -Denable_cplusplus=OFF -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded
+cmake ../../../../../3rdParty/gc-8.2.12 -G "Visual Studio 18 2026" -A x64 %EXTRA_PARAM% -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF -Wno-dev -DCMAKE_INSTALL_PREFIX=../../../../../3rdParty/gc/x64/release -Denable_threads=ON -Denable_cplusplus=OFF -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded
 cmake --build . --config Release -j 8
 cmake --install . --config Release
 popd
\ No newline at end of file
diff --git a/tsc/test/tester/test-runner.cpp b/tsc/test/tester/test-runner.cpp
index 7e4739ec5..530aab430 100644
--- a/tsc/test/tester/test-runner.cpp
+++ b/tsc/test/tester/test-runner.cpp
@@ -428,6 +428,16 @@ void createSharedMultiBatchFile(std::string tempOutputFileNameNoExt, std::vector
     batFile << "set TSC_LIB_PATH=" << TEST_TSC_LIBPATH << std::endl;
     batFile << "set GC_LIB_PATH=" << TEST_GCPATH << std::endl;
 
+    // run everything inside a unique per-test working directory: the shared lib must keep its
+    // real name (<stem>.dll) for `import './<stem>'` to resolve, but that name is not unique
+    // across tests reusing the same source file (e.g. decl_class.ts feeds the compile/compile-time/jit
+    // variants) - isolating the cwd avoids parallel collisions under `ctest -j`. The .txt/.err output
+    // is written to the parent dir where the runner reads it from.
+    batFile << "set WORKDIR=" << tempOutputFileNameNoExt << "_wd" << std::endl;
+    batFile << "if exist %WORKDIR% rmdir /s /q %WORKDIR%" << std::endl;
+    batFile << "mkdir %WORKDIR%" << std::endl;
+    batFile << "cd %WORKDIR%" << std::endl;
+
     auto first = true;
     std::stringstream shared_objs;
     std::stringstream shared_libs;
@@ -472,7 +482,7 @@ void createSharedMultiBatchFile(std::string tempOutputFileNameNoExt, std::vector
 
     if (jitRun)
     {
-        batFile << "%TSCEXEPATH%\\tsc.exe --emit=jit " << tsc_opt << " --shared-libs=%TSCEXEPATH%/TypeScriptRuntime.dll " << *files.begin() << " 1> %FILENAME%.txt 2> %FILENAME%.err"
+        batFile << "%TSCEXEPATH%\\tsc.exe --emit=jit " << tsc_opt << " --shared-libs=%TSCEXEPATH%/TypeScriptRuntime.dll " << *files.begin() << " 1> ..\\%FILENAME%.txt 2> ..\\%FILENAME%.err"
                 << std::endl;
 
         batFile << "del " << shared_libs.str() << std::endl;
@@ -494,7 +504,7 @@ void createSharedMultiBatchFile(std::string tempOutputFileNameNoExt, std::vector
 
         batFile << "del " << exec_objs.str() << std::endl;
 
-        batFile << "call " RUN_CMD "%FILENAME%.exe 1> %FILENAME%.txt 2> %FILENAME%.err" << std::endl;
+        batFile << "call " RUN_CMD "%FILENAME%.exe 1> ..\\%FILENAME%.txt 2> ..\\%FILENAME%.err" << std::endl;
 
         batFile << "echo off" << std::endl;
         batFile << "del " << shared_libs.str() << std::endl;
@@ -506,6 +516,12 @@ void createSharedMultiBatchFile(std::string tempOutputFileNameNoExt, std::vector
         batFile << "echo on" << std::endl;
     }
 
+    // leave and remove the per-test working directory (with the shared lib, exe, objs, etc.)
+    batFile << "echo off" << std::endl;
+    batFile << "cd .." << std::endl;
+    batFile << "rmdir /s /q %WORKDIR%" << std::endl;
+    batFile << "echo on" << std::endl;
+
     batFile.close();
 #else
     std::ofstream batFile(tempOutputFileNameNoExt + BAT_NAME);
diff --git a/tsc/tsc/exe.cpp b/tsc/tsc/exe.cpp
index 135d62125..8c3be973b 100644
--- a/tsc/tsc/exe.cpp
+++ b/tsc/tsc/exe.cpp
@@ -437,29 +437,27 @@ int buildExe(int argc, char **argv, std::string objFileName, std::string additio
     // system
     if (win)
     {
-        args.push_back("-luser32");    
+        args.push_back("-luser32");
+
+        // Link the static CRT (/MT[d]) to match the prebuilt static LLVM/MLIR libs,
+        // the TypeScript runtime libs and gc.lib. Mixing the static and dynamic CRT
+        // gives the generated program a separate heap/stdout buffer from those libs
+        // and crashes at startup/teardown (0xC0000005). The release config uses the
+        // non-debug import-name suffix; debug uses the 'd' suffix.
         if (enableOpt)
         {
-            args.push_back("-lucrt");    
+            args.push_back("-llibucrt");
+            args.push_back("-llibcmt");
+            args.push_back("-llibvcruntime");
         }
         else
         {
-            args.push_back("-lucrtd");    
+            args.push_back("-llibucrtd");
+            args.push_back("-llibcmtd");
+            args.push_back("-llibvcruntimed");
         }
 
         args.push_back("-lntdll");
-        if (shared || !disableGC)
-        {
-            // needed to resolve DLL ref
-            if (enableOpt)
-            {
-                args.push_back("-lmsvcrt");
-            }
-            else
-            {
-                args.push_back("-lmsvcrtd");
-            }
-        }
     }
 
     // tsc libs