diff --git a/stl/inc/climits b/stl/inc/climits
index 20b85bdf25a..097693232ff 100644
--- a/stl/inc/climits
+++ b/stl/inc/climits
@@ -8,7 +8,10 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
+#pragma warning(push) // TRANSITION, VSO-1985428
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <limits.h>
+#pragma warning(pop)
 
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _CLIMITS_
diff --git a/tests/std/include/test_death.hpp b/tests/std/include/test_death.hpp
index d88f63e9dab..87a2c7080b1 100644
--- a/tests/std/include/test_death.hpp
+++ b/tests/std/include/test_death.hpp
@@ -9,7 +9,10 @@
 #include <string>
 #include <vector>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 namespace std_testing {
     constexpr int internal_failure = 103;
diff --git a/tests/std/include/test_thread_support.hpp b/tests/std/include/test_thread_support.hpp
index a2e44363468..1ff3ae02130 100644
--- a/tests/std/include/test_thread_support.hpp
+++ b/tests/std/include/test_thread_support.hpp
@@ -10,7 +10,10 @@
 #include <mutex>
 #include <thread>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 class one_shot {
     bool unblock = false;
diff --git a/tests/std/tests/Dev08_563686_ostream/test.cpp b/tests/std/tests/Dev08_563686_ostream/test.cpp
index 48935394f57..11d905320fd 100644
--- a/tests/std/tests/Dev08_563686_ostream/test.cpp
+++ b/tests/std/tests/Dev08_563686_ostream/test.cpp
@@ -29,7 +29,10 @@
 #include <cstdlib>
 #include <sstream>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 int main() {
     // Track CRT blocks
diff --git a/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp b/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
index c37f325f7da..1fecfd287e3 100644
--- a/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
+++ b/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
@@ -7,7 +7,10 @@
 #include <cstdio>
 #include <locale>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 using namespace std;
 
diff --git a/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp b/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
index b890a5b02ab..dd3ef599709 100644
--- a/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
+++ b/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
@@ -3,9 +3,6 @@
 
 #include <cassert>
 #include <locale>
-
-#include <Windows.h>
-
 using namespace std;
 
 // Tests for DLL
diff --git a/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp b/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
index 749b29b1908..f95c731abd3 100644
--- a/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
+++ b/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
@@ -20,7 +20,10 @@ InvalidFunctor make_error_condition{};
 #include <future>
 #endif // _M_CEE_PURE
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 using namespace std;
 
diff --git a/tests/std/tests/GH_002431_byte_range_find_with_unreachable_sentinel/test.cpp b/tests/std/tests/GH_002431_byte_range_find_with_unreachable_sentinel/test.cpp
index efb5a03368d..4bbf13a56db 100644
--- a/tests/std/tests/GH_002431_byte_range_find_with_unreachable_sentinel/test.cpp
+++ b/tests/std/tests/GH_002431_byte_range_find_with_unreachable_sentinel/test.cpp
@@ -7,7 +7,10 @@
 #include <isa_availability.h>
 #include <ranges>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 using namespace std;
 
diff --git a/tests/std/tests/P2093R14_formatted_output/test.cpp b/tests/std/tests/P2093R14_formatted_output/test.cpp
index 92eb0884942..7c27d02a2f3 100644
--- a/tests/std/tests/P2093R14_formatted_output/test.cpp
+++ b/tests/std/tests/P2093R14_formatted_output/test.cpp
@@ -18,7 +18,10 @@
 #include <string_view>
 #include <vector>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 #include "temp_file_name.hpp"
 
diff --git a/tests/std/tests/VSO_0000000_exception_ptr_rethrow_seh/test.cpp b/tests/std/tests/VSO_0000000_exception_ptr_rethrow_seh/test.cpp
index 6052ab4a493..60e6775aae8 100644
--- a/tests/std/tests/VSO_0000000_exception_ptr_rethrow_seh/test.cpp
+++ b/tests/std/tests/VSO_0000000_exception_ptr_rethrow_seh/test.cpp
@@ -8,7 +8,10 @@
 #include <exception>
 #include <excpt.h>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 ULONG_PTR data[] = {0xC0FFEE, 1729};
 
diff --git a/tests/std/tests/VSO_0104705_throwing_copy_in_current_exception_seh/test.cpp b/tests/std/tests/VSO_0104705_throwing_copy_in_current_exception_seh/test.cpp
index de2c60e1bd0..2c993e0752f 100644
--- a/tests/std/tests/VSO_0104705_throwing_copy_in_current_exception_seh/test.cpp
+++ b/tests/std/tests/VSO_0104705_throwing_copy_in_current_exception_seh/test.cpp
@@ -7,7 +7,10 @@
 #include <exception>
 #include <excpt.h>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 ULONG_PTR data[] = {0xC0FFEE, 1729};
 
diff --git a/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp b/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
index 77be49b3f52..f219b21a6d1 100644
--- a/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
+++ b/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
@@ -12,7 +12,10 @@
 #include <string>
 #include <system_error>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 using namespace std;
 namespace fs = std::experimental::filesystem;
diff --git a/tests/std/tests/VSO_0226079_mutex/test.cpp b/tests/std/tests/VSO_0226079_mutex/test.cpp
index 584b3e982ea..9029ea2a3a8 100644
--- a/tests/std/tests/VSO_0226079_mutex/test.cpp
+++ b/tests/std/tests/VSO_0226079_mutex/test.cpp
@@ -13,7 +13,10 @@
 #include <thread>
 #include <utility>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 using namespace std;
 using namespace std::chrono;
diff --git a/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp b/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
index d0050dba5c5..66f93fa472d 100644
--- a/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
+++ b/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
@@ -5,7 +5,10 @@
 #include <cassert>
 #include <cstdio>
 
+#pragma warning(push) // TRANSITION, OS-23694920
+#pragma warning(disable : 4668) // 'MEOW' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
 #include <Windows.h>
+#pragma warning(pop)
 
 int main() {
     // A customer wanted to read a std::atomic from a read-only memory-mapped file.
diff --git a/tests/std/tests/prefix.lst b/tests/std/tests/prefix.lst
index a2606478982..ca509bbe8fc 100644
--- a/tests/std/tests/prefix.lst
+++ b/tests/std/tests/prefix.lst
@@ -3,4 +3,4 @@
 
 RUNALL_INCLUDE ..\..\universal_prefix.lst
 RUNALL_CROSSLIST
-*	PM_CL="/FIforce_include.hpp /w14365 /w15267 /D_ENFORCE_FACET_SPECIALIZATIONS=1 /D_STL_CALL_ABORT_INSTEAD_OF_INVALID_PARAMETER"
+*	PM_CL="/FIforce_include.hpp /w14365 /w14668 /w15267 /D_ENFORCE_FACET_SPECIALIZATIONS=1 /D_STL_CALL_ABORT_INSTEAD_OF_INVALID_PARAMETER"
diff --git a/tests/tr1/include/tdefs.h b/tests/tr1/include/tdefs.h
index f3431d4017b..30e03803e8f 100644
--- a/tests/tr1/include/tdefs.h
+++ b/tests/tr1/include/tdefs.h
@@ -369,7 +369,6 @@ int ulp = EPS_ULPL;
 #endif // value of FLOAT_TYPE
 
 int approx2(Float_type d1, Float_type d2, Float_type sensitivity) { // test for approximate equality
-#if 199901L <= __STDC_VERSION__
     if (isunordered(d1, d2)) { // at least one NaN
         if (!terse) { // report NaNs
             if (isnan(d1)) {
@@ -381,9 +380,7 @@ int approx2(Float_type d1, Float_type d2, Float_type sensitivity) { // test for
             }
         }
         return 0;
-    } else
-#endif // 199901L <= __STDC_VERSION__
-    { // compare finite values
+    } else { // compare finite values
         Float_type err;
 
         if (d2 != (Float_type) 0) {
diff --git a/tests/tr1/prefix.lst b/tests/tr1/prefix.lst
index 45b4447dc69..5d1ecb45c88 100644
--- a/tests/tr1/prefix.lst
+++ b/tests/tr1/prefix.lst
@@ -3,4 +3,4 @@
 
 RUNALL_INCLUDE ..\universal_prefix.lst
 RUNALL_CROSSLIST
-*	PM_CL="/FIforce_include.hpp /w15267 /D_ENFORCE_FACET_SPECIALIZATIONS=1 /D_CRT_SECURE_NO_WARNINGS /D_STL_CALL_ABORT_INSTEAD_OF_INVALID_PARAMETER"
+*	PM_CL="/FIforce_include.hpp /w14668 /w15267 /D_ENFORCE_FACET_SPECIALIZATIONS=1 /D_CRT_SECURE_NO_WARNINGS /D_STL_CALL_ABORT_INSTEAD_OF_INVALID_PARAMETER"
diff --git a/tests/tr1/tests/regex2/test.cpp b/tests/tr1/tests/regex2/test.cpp
index 146c8809c67..5d676d4fd8e 100644
--- a/tests/tr1/tests/regex2/test.cpp
+++ b/tests/tr1/tests/regex2/test.cpp
@@ -395,12 +395,12 @@ static const regex_test tests[] = {
 
     {__LINE__, T("\\x1b"), T("\x1b"), "1 0 1", ECMA},
 
-#if WIDE
+#ifdef WIDE
     {__LINE__, T("\\u12cd"), T("\u12cd"), "1 0 1", ECMA},
     {__LINE__, T("\\u12cd"), T(""), "-1", NOT_ECMA},
-#else
+#else // defined WIDE
     {__LINE__, T("\\u12cd"), T(""), "-1", ALL},
-#endif
+#endif // defined WIDE
 
     {__LINE__, T("\\07"), T("\07"), "1 0 1", AWK},
     {__LINE__, T("\\177"), T("\177"), "1 0 1", AWK},
@@ -495,11 +495,11 @@ static const regex_test tests[] = {
     {__LINE__, T("[\\x1b]"), T("x"), "1 0 1", NOT_ECMA},
     {__LINE__, T("[\\x1b]"), T("1"), "1 0 1", NOT_ECMA},
     {__LINE__, T("[\\x1b]"), T("b"), "1 0 1", NOT_ECMA},
-#if WIDE
+#ifdef WIDE
     {__LINE__, T("[\\u12cd]"), T("\u12cd"), "1 0 1", ECMA},
-#else
+#else // defined WIDE
     {__LINE__, T("[\\u12cd]"), T(""), "-1", ECMA},
-#endif
+#endif // defined WIDE
     {__LINE__, T("[\\u12cd]"), T("\\"), "1 0 1", NOT_ECMA},
     {__LINE__, T("[\\u12cd]"), T("u"), "1 0 1", NOT_ECMA},
     {__LINE__, T("[\\u12cd]"), T("1"), "1 0 1", NOT_ECMA},