diff --git a/stl/inc/__msvc_all_public_headers.hpp b/stl/inc/__msvc_all_public_headers.hpp
index 912896ed2d9..b238fdb7602 100644
--- a/stl/inc/__msvc_all_public_headers.hpp
+++ b/stl/inc/__msvc_all_public_headers.hpp
@@ -37,18 +37,52 @@
 #define _SILENCE_EXPERIMENTAL_FILESYSTEM_DEPRECATION_WARNING
 #define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS
 
+// Core STL Headers
+#include <bit>
+#include <compare>
+#include <concepts>
+#include <coroutine>
+#include <initializer_list>
+#include <limits>
+#include <numbers>
+#include <ratio>
+#include <type_traits>
+#include <utility>
+#include <version>
+
+// Core C Wrapper Headers
+#include <cassert>
+#include <cctype>
+#include <cerrno>
+#include <cfenv>
+#include <cfloat>
+#include <cinttypes>
+#include <climits>
+#include <clocale>
+#include <csetjmp>
+#include <csignal>
+#include <cstdarg>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <cuchar>
+#include <cwchar>
+#include <cwctype>
+
+#ifndef _CORE_HEADERS_ONLY
+
+// Non-Core STL Headers
 #include <algorithm>
 #include <any>
 #include <array>
-#include <bit>
 #include <bitset>
 #include <charconv>
 #include <chrono>
 #include <codecvt>
-#include <compare>
 #include <complex>
-#include <concepts>
-#include <coroutine>
 #include <deque>
 #include <exception>
 #include <filesystem>
@@ -57,28 +91,24 @@
 #include <functional>
 #include <hash_map>
 #include <hash_set>
-#include <initializer_list>
 #include <iomanip>
 #include <ios>
 #include <iosfwd>
 #include <iostream>
 #include <istream>
 #include <iterator>
-#include <limits>
 #include <list>
 #include <locale>
 #include <map>
 #include <memory>
 #include <memory_resource>
 #include <new>
-#include <numbers>
 #include <numeric>
 #include <optional>
 #include <ostream>
 #include <queue>
 #include <random>
 #include <ranges>
-#include <ratio>
 #include <regex>
 #include <scoped_allocator>
 #include <set>
@@ -92,16 +122,13 @@
 #include <strstream>
 #include <system_error>
 #include <tuple>
-#include <type_traits>
 #include <typeindex>
 #include <typeinfo>
 #include <unordered_map>
 #include <unordered_set>
-#include <utility>
 #include <valarray>
 #include <variant>
 #include <vector>
-#include <version>
 
 #ifndef _M_CEE_PURE
 #include <atomic>
@@ -120,32 +147,15 @@
 #include <thread>
 #endif // _M_CEE
 
-#include <cassert>
+// Non-Core C Wrapper Headers
 #include <ccomplex>
-#include <cctype>
-#include <cerrno>
-#include <cfenv>
-#include <cfloat>
-#include <cinttypes>
 #include <ciso646>
-#include <climits>
-#include <clocale>
 #include <cmath>
-#include <csetjmp>
-#include <csignal>
 #include <cstdalign>
-#include <cstdarg>
 #include <cstdbool>
-#include <cstddef>
-#include <cstdint>
-#include <cstdio>
-#include <cstdlib>
-#include <cstring>
 #include <ctgmath>
-#include <ctime>
-#include <cuchar>
-#include <cwchar>
-#include <cwctype>
+
+// Non-Core Experimental Headers
 #include <experimental/deque>
 #include <experimental/filesystem>
 #include <experimental/forward_list>
@@ -157,9 +167,10 @@
 #include <experimental/unordered_set>
 #include <experimental/vector>
 
+#endif // _CORE_HEADERS_ONLY
+
 #ifndef _MSVC_TESTING_NVCC
 #include <assert.h>
-#include <complex.h>
 #include <conio.h>
 #include <crtdbg.h>
 #include <ctype.h>
@@ -181,7 +192,6 @@
 #include <mbstring.h>
 #include <memory.h>
 #include <minmax.h>
-#include <new.h>
 #include <process.h>
 #include <safeint.h>
 #include <sal.h>
@@ -207,6 +217,11 @@
 #include <wchar.h>
 #include <wctype.h>
 
+#ifndef _CORE_HEADERS_ONLY
+#include <complex.h>
+#include <new.h>
+#endif // _CORE_HEADERS_ONLY
+
 #ifndef _M_CEE_PURE
 #include <fpieee.h>
 #endif // _M_CEE_PURE
diff --git a/stl/inc/__msvc_system_error_abi.hpp b/stl/inc/__msvc_system_error_abi.hpp
index d6744adf1f2..d95b458cf55 100644
--- a/stl/inc/__msvc_system_error_abi.hpp
+++ b/stl/inc/__msvc_system_error_abi.hpp
@@ -8,7 +8,7 @@
 #define __MSVC_SYSTEM_ERROR_ABI_HPP
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
-#include <stddef.h>
+#include <cstddef>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/inc/atomic b/stl/inc/atomic
index 349bcc92615..8dfadf62917 100644
--- a/stl/inc/atomic
+++ b/stl/inc/atomic
@@ -13,9 +13,9 @@
 #error <atomic> is not supported when compiling with /clr:pure.
 #endif // _M_CEE_PURE
 
-#include <stddef.h> // for size_t
-#include <stdint.h>
-#include <string.h>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
 #include <xatomic.h>
 #if _HAS_CXX20
 #include <xatomic_wait.h>
diff --git a/stl/inc/barrier b/stl/inc/barrier
index 2258cfe26de..fc0eb1df2cd 100644
--- a/stl/inc/barrier
+++ b/stl/inc/barrier
@@ -18,7 +18,7 @@
 #else // ^^^ !_HAS_CXX20 / _HAS_CXX20 vvv
 
 #include <atomic>
-#include <limits.h>
+#include <climits>
 #include <type_traits>
 #include <xmemory>
 
diff --git a/stl/inc/cassert b/stl/inc/cassert
index 18b2f2b7778..cf8f3cef253 100644
--- a/stl/inc/cassert
+++ b/stl/inc/cassert
@@ -1,9 +1,9 @@
-// cassert standard header
+// cassert standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 // NOTE: no include guard
-#include <yvals.h>
+#include <yvals_core.h>
 
 #include <assert.h>
diff --git a/stl/inc/cctype b/stl/inc/cctype
index d9980f4f33d..cc6c49fe7b3 100644
--- a/stl/inc/cctype
+++ b/stl/inc/cctype
@@ -1,4 +1,4 @@
-// cctype standard header
+// cctype standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CCTYPE_
 #define _CCTYPE_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <ctype.h>
diff --git a/stl/inc/cerrno b/stl/inc/cerrno
index efc14b66727..1b5a470c32c 100644
--- a/stl/inc/cerrno
+++ b/stl/inc/cerrno
@@ -1,4 +1,4 @@
-// cerrno standard header
+// cerrno standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CERRNO_
 #define _CERRNO_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <errno.h>
diff --git a/stl/inc/cfenv b/stl/inc/cfenv
index 778dd014a82..c78b9837248 100644
--- a/stl/inc/cfenv
+++ b/stl/inc/cfenv
@@ -1,4 +1,4 @@
-// cfenv standard header
+// cfenv standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CFENV_
 #define _CFENV_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <fenv.h>
diff --git a/stl/inc/charconv b/stl/inc/charconv
index dd3e91acb91..9994d42f528 100644
--- a/stl/inc/charconv
+++ b/stl/inc/charconv
@@ -12,8 +12,8 @@
 #if !_HAS_CXX17
 #pragma message("The contents of <charconv> are available only with C++17 or later.")
 #else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
+#include <cstring>
 #include <intrin0.h>
-#include <string.h>
 #include <xbit_ops.h>
 #include <xcharconv.h>
 #include <xcharconv_ryu.h>
diff --git a/stl/inc/chrono b/stl/inc/chrono
index b19aa83f7cd..d53e2873cb6 100644
--- a/stl/inc/chrono
+++ b/stl/inc/chrono
@@ -8,10 +8,10 @@
 #define _CHRONO_
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
+#include <ctime>
 #include <limits>
 #include <ratio>
 #include <sstream>
-#include <time.h>
 #include <utility>
 #include <xtimec.h>
 
diff --git a/stl/inc/cinttypes b/stl/inc/cinttypes
index 2b130570796..d1f07e10a51 100644
--- a/stl/inc/cinttypes
+++ b/stl/inc/cinttypes
@@ -1,4 +1,4 @@
-// cinttypes standard header
+// cinttypes standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CINTTYPES_
 #define _CINTTYPES_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <cstdint>
diff --git a/stl/inc/clocale b/stl/inc/clocale
index f725ad9df67..bfc5a0aacff 100644
--- a/stl/inc/clocale
+++ b/stl/inc/clocale
@@ -1,4 +1,4 @@
-// clocale standard header
+// clocale standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CLOCALE_
 #define _CLOCALE_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <locale.h>
diff --git a/stl/inc/csetjmp b/stl/inc/csetjmp
index 3c25d009937..802ff156e63 100644
--- a/stl/inc/csetjmp
+++ b/stl/inc/csetjmp
@@ -1,4 +1,4 @@
-// csetjmp standard header
+// csetjmp standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CSETJMP_
 #define _CSETJMP_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <setjmp.h>
diff --git a/stl/inc/csignal b/stl/inc/csignal
index 077056161ee..fc88191d7dc 100644
--- a/stl/inc/csignal
+++ b/stl/inc/csignal
@@ -1,4 +1,4 @@
-// csignal standard header
+// csignal standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CSIGNAL_
 #define _CSIGNAL_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <signal.h>
diff --git a/stl/inc/cstdarg b/stl/inc/cstdarg
index af09a4fa7d2..f9897bcb17a 100644
--- a/stl/inc/cstdarg
+++ b/stl/inc/cstdarg
@@ -1,4 +1,4 @@
-// cstdarg standard header
+// cstdarg standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CSTDARG_
 #define _CSTDARG_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <stdarg.h>
diff --git a/stl/inc/cstring b/stl/inc/cstring
index 8c714e9db08..a0140aa307c 100644
--- a/stl/inc/cstring
+++ b/stl/inc/cstring
@@ -1,4 +1,4 @@
-// cstring standard header
+// cstring standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CSTRING_
 #define _CSTRING_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <string.h>
diff --git a/stl/inc/ctime b/stl/inc/ctime
index a6f3ddc01a9..94ed91c49c8 100644
--- a/stl/inc/ctime
+++ b/stl/inc/ctime
@@ -1,4 +1,4 @@
-// ctime standard header
+// ctime standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CTIME_
 #define _CTIME_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <time.h>
diff --git a/stl/inc/cuchar b/stl/inc/cuchar
index 86119e20f87..fc8feb0be82 100644
--- a/stl/inc/cuchar
+++ b/stl/inc/cuchar
@@ -1,4 +1,4 @@
-// cuchar standard header
+// cuchar standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CUCHAR_
 #define _CUCHAR_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <uchar.h>
diff --git a/stl/inc/cwctype b/stl/inc/cwctype
index 567d6642ae7..cfcbe9040ef 100644
--- a/stl/inc/cwctype
+++ b/stl/inc/cwctype
@@ -1,4 +1,4 @@
-// cwctype standard header
+// cwctype standard header (core)
 
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -6,7 +6,7 @@
 #pragma once
 #ifndef _CWCTYPE_
 #define _CWCTYPE_
-#include <yvals.h>
+#include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
 #include <wctype.h>
diff --git a/stl/inc/experimental/coroutine b/stl/inc/experimental/coroutine
index c6ed2a2a292..062973090ba 100644
--- a/stl/inc/experimental/coroutine
+++ b/stl/inc/experimental/coroutine
@@ -16,7 +16,7 @@
 #if _HAS_EXCEPTIONS
 #include <exception>
 #endif
-#include <stdint.h>
+#include <cstdint>
 #include <type_traits>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/experimental/resumable b/stl/inc/experimental/resumable
index 7f308dd3ecf..0991c7c20d4 100644
--- a/stl/inc/experimental/resumable
+++ b/stl/inc/experimental/resumable
@@ -15,8 +15,8 @@
 #if _HAS_EXCEPTIONS
 #include <exception>
 #endif
+#include <cstdint>
 #include <experimental/coroutine>
-#include <stdint.h>
 #include <type_traits>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/latch b/stl/inc/latch
index 3743af76484..16eea8b0fed 100644
--- a/stl/inc/latch
+++ b/stl/inc/latch
@@ -18,7 +18,7 @@
 #else // ^^^ !_HAS_CXX20 / _HAS_CXX20 vvv
 
 #include <atomic>
-#include <limits.h>
+#include <climits>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/inc/mutex b/stl/inc/mutex
index 501fa02c01f..5d781ceff82 100644
--- a/stl/inc/mutex
+++ b/stl/inc/mutex
@@ -14,7 +14,7 @@
 #endif // _M_CEE_PURE
 
 #include <chrono>
-#include <stdlib.h>
+#include <cstdlib>
 #include <system_error>
 #include <thread>
 #include <utility>
diff --git a/stl/inc/random b/stl/inc/random
index 1854b1f234d..af9a36b5a68 100644
--- a/stl/inc/random
+++ b/stl/inc/random
@@ -11,8 +11,8 @@
 #if _STL_COMPILER_PREPROCESSOR
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
 #include <iosfwd>
-#include <stdint.h>
 #include <vector>
 #include <xbit_ops.h>
 #include <xstring>
diff --git a/stl/inc/ratio b/stl/inc/ratio
index d290147f24a..0a1b09f7619 100644
--- a/stl/inc/ratio
+++ b/stl/inc/ratio
@@ -8,7 +8,7 @@
 #define _RATIO_
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
-#include <stdint.h>
+#include <cstdint>
 #include <type_traits>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/semaphore b/stl/inc/semaphore
index 0845bdf00f3..79d2760603b 100644
--- a/stl/inc/semaphore
+++ b/stl/inc/semaphore
@@ -19,7 +19,7 @@
 
 #include <atomic>
 #include <chrono>
-#include <limits.h>
+#include <climits>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/inc/tuple b/stl/inc/tuple
index ee6f40fb1e2..7060e6968bd 100644
--- a/stl/inc/tuple
+++ b/stl/inc/tuple
@@ -8,7 +8,6 @@
 #define _TUPLE_
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
-#include <new>
 #include <type_traits>
 #include <xutility>
 
diff --git a/stl/inc/xatomic.h b/stl/inc/xatomic.h
index 3298d828ae8..af41c5af67a 100644
--- a/stl/inc/xatomic.h
+++ b/stl/inc/xatomic.h
@@ -11,9 +11,6 @@
 
 #include <intrin0.h>
 #include <type_traits>
-#if defined(_WIN64) && (_MSC_FULL_VER <= 192829213) // TRANSITION
-#include <intrin.h> // Visual Studio 2019 to define 128-bit CAS in <intrin0.h>
-#endif // defined(_WIN64) && (_MSC_FULL_VER <= 192829213), TRANSITION
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/inc/xatomic_wait.h b/stl/inc/xatomic_wait.h
index caeb3fdaf9d..42378ea39d3 100644
--- a/stl/inc/xatomic_wait.h
+++ b/stl/inc/xatomic_wait.h
@@ -9,7 +9,7 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <stdlib.h>
+#include <cstdlib>
 #include <xatomic.h>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/xcharconv.h b/stl/inc/xcharconv.h
index 9305de5505d..ecd69b6d02e 100644
--- a/stl/inc/xcharconv.h
+++ b/stl/inc/xcharconv.h
@@ -9,7 +9,7 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <stdint.h>
+#include <cstdint>
 #include <type_traits>
 #include <xerrc.h>
 
diff --git a/stl/inc/xcharconv_ryu.h b/stl/inc/xcharconv_ryu.h
index def634d2273..1b2b95a8e05 100644
--- a/stl/inc/xcharconv_ryu.h
+++ b/stl/inc/xcharconv_ryu.h
@@ -38,7 +38,7 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <string.h>
+#include <cstring>
 #include <xcharconv.h>
 #include <xcharconv_ryu_tables.h>
 
diff --git a/stl/inc/xcharconv_ryu_tables.h b/stl/inc/xcharconv_ryu_tables.h
index cea6fd2b5a8..508d3479fdf 100644
--- a/stl/inc/xcharconv_ryu_tables.h
+++ b/stl/inc/xcharconv_ryu_tables.h
@@ -38,7 +38,7 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <stdint.h>
+#include <cstdint>
 
 #if !_HAS_CXX17
 #error The contents of <charconv> are only available with C++17. (Also, you should not include this internal header.)
diff --git a/stl/inc/xfilesystem_abi.h b/stl/inc/xfilesystem_abi.h
index 7991c1d522e..52f8c8f7404 100644
--- a/stl/inc/xfilesystem_abi.h
+++ b/stl/inc/xfilesystem_abi.h
@@ -9,7 +9,7 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <stdint.h>
+#include <cstdint>
 #include <type_traits>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/xlocinfo.h b/stl/inc/xlocinfo.h
index 9891775d16a..f3e36738c9c 100644
--- a/stl/inc/xlocinfo.h
+++ b/stl/inc/xlocinfo.h
@@ -9,10 +9,10 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <ctype.h>
-#include <locale.h>
-#include <stdio.h> // TRANSITION, VSO-661721
-#include <wchar.h>
+#include <cctype>
+#include <clocale>
+#include <cstdio> // TRANSITION, VSO-661721
+#include <cwchar>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/inc/xthreads.h b/stl/inc/xthreads.h
index f2d95ff63d4..c8c88800575 100644
--- a/stl/inc/xthreads.h
+++ b/stl/inc/xthreads.h
@@ -8,7 +8,7 @@
 #define _THR_XTHREADS_H
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
-#include <limits.h>
+#include <climits>
 #include <xtimec.h>
 
 #pragma pack(push, _CRT_PACKING)
diff --git a/stl/inc/xtimec.h b/stl/inc/xtimec.h
index 67b75522d16..64741469db9 100644
--- a/stl/inc/xtimec.h
+++ b/stl/inc/xtimec.h
@@ -9,7 +9,7 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#include <time.h>
+#include <ctime>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
diff --git a/stl/src/xstol.cpp b/stl/src/xstol.cpp
index 3cd73becd64..0e5f94ba008 100644
--- a/stl/src/xstol.cpp
+++ b/stl/src/xstol.cpp
@@ -10,8 +10,6 @@
 #include <climits>
 #include <cstdlib>
 
-#include "xmath.hpp"
-
 _EXTERN_C_UNLESS_PURE
 
 _CRTIMP2_PURE unsigned long __CLRCALL_PURE_OR_CDECL _Stoulx(const char*, char**, int, int*);
diff --git a/stl/src/xstoll.cpp b/stl/src/xstoll.cpp
index 63ad80e1493..4bddd4e19c9 100644
--- a/stl/src/xstoll.cpp
+++ b/stl/src/xstoll.cpp
@@ -3,13 +3,13 @@
 
 // _Stoll function
 
+#include <yvals.h>
+
 #include <cctype>
 #include <cerrno>
 #include <climits>
 #include <cstdlib>
 
-#include "xmath.hpp"
-
 _EXTERN_C_UNLESS_PURE
 
 _CRTIMP2_PURE unsigned long long __CLRCALL_PURE_OR_CDECL _Stoullx(const char*, char**, int, int*);
diff --git a/stl/src/xstoul.cpp b/stl/src/xstoul.cpp
index 48f48489b22..9dd8385b8d5 100644
--- a/stl/src/xstoul.cpp
+++ b/stl/src/xstoul.cpp
@@ -3,6 +3,8 @@
 
 // _Stoul function
 
+#include <yvals.h>
+
 #include <cctype>
 #include <cerrno>
 #include <climits>
@@ -10,15 +12,12 @@
 #include <cstdlib>
 #include <cstring>
 
-
 _EXTERN_C_UNLESS_PURE
 
-// macros
 constexpr int _Base_max = 36; // largest valid base
 
 // static data
-static const char digits[] = // valid digits
-    "0123456789abcdefghijklmnopqrstuvwxyz";
+static const char digits[] = "0123456789abcdefghijklmnopqrstuvwxyz"; // valid digits
 
 // 32-bits!
 static const char ndigs[_Base_max + 1] = {0, 0, 33, 21, 17, 14, 13, 12, 11, 11, 10, 10, 9, 9, 9, 9, 9, 8, 8, 8, 8, 8, 8,
diff --git a/stl/src/xstoull.cpp b/stl/src/xstoull.cpp
index 8a29d7ab260..3deaf903e6e 100644
--- a/stl/src/xstoull.cpp
+++ b/stl/src/xstoull.cpp
@@ -3,6 +3,8 @@
 
 // _Stoull function
 
+#include <yvals.h>
+
 #include <cctype>
 #include <cerrno>
 #include <climits>
diff --git a/tests/std/test.lst b/tests/std/test.lst
index 4140f5fd7cb..33118a0aecc 100644
--- a/tests/std/test.lst
+++ b/tests/std/test.lst
@@ -169,6 +169,7 @@ tests\GH_001059_hyperbolic_truncation
 tests\GH_001086_partial_sort_copy
 tests\GH_001103_countl_zero_correctness
 tests\GH_001123_random_cast_out_of_range
+tests\GH_001411_core_headers
 tests\LWG2597_complex_branch_cut
 tests\LWG3018_shared_ptr_function
 tests\P0019R8_atomic_ref
diff --git a/tests/std/tests/GH_001411_core_headers/env.lst b/tests/std/tests/GH_001411_core_headers/env.lst
new file mode 100644
index 00000000000..19f025bd0e6
--- /dev/null
+++ b/tests/std/tests/GH_001411_core_headers/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst
diff --git a/tests/std/tests/GH_001411_core_headers/test.cpp b/tests/std/tests/GH_001411_core_headers/test.cpp
new file mode 100644
index 00000000000..5a45bd65689
--- /dev/null
+++ b/tests/std/tests/GH_001411_core_headers/test.cpp
@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#define _CORE_HEADERS_ONLY
+
+#include <__msvc_all_public_headers.hpp>
+
+#ifdef _YVALS
+#error Core headers should not include <yvals.h>.
+#endif
+
+#include <chrono>
+
+#ifndef _YVALS
+#error Non-core headers like <chrono> should include <yvals.h>.
+#endif
+
+int main() {} // COMPILE-ONLY