diff --git a/.github/BUILD.bazel b/.github/BUILD.bazel
index 45297fc11671a..7ce6f2c2b8052 100644
--- a/.github/BUILD.bazel
+++ b/.github/BUILD.bazel
@@ -1,5 +1,5 @@
 # This information is extracted from the MacOS runner specs located at:
-# https://github.com/actions/runner-images/blob/main/images/macos/macos-12-Readme.md
+# https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md
 #
 # When updating, also ensure the "xcode_destination" entries in
 # `.github/workflows/test_objectivec.yml` are supported for the given versions
diff --git a/.github/workflows/test_cpp.yml b/.github/workflows/test_cpp.yml
index 35ecae8633b6b..742848fdc568d 100644
--- a/.github/workflows/test_cpp.yml
+++ b/.github/workflows/test_cpp.yml
@@ -321,17 +321,17 @@ jobs:
       matrix:
         include:
           - name: MacOS Bazel
-            os: macos-12
-            cache_key: macos-12
+            os: macos-13
+            cache_key: macos-13
             bazel: test //src/... //third_party/utf8_range/...
           - name: MacOS Bazel 7
-            os: macos-12
-            cache_key: macos-12-bazel7
+            os: macos-13
+            cache_key: macos-13-bazel7
             bazel: test //src/... //third_party/utf8_range/...
             bazel_version: '7.1.2'
           - name: MacOS Apple Silicon (build only) Bazel
-            os: macos-12
-            cache_key: macos-12-arm
+            os: macos-13
+            cache_key: macos-13-arm
             # Current github runners are all Intel based, so just build/compile
             # for Apple Silicon to detect issues there.
             bazel: build --cpu=darwin_arm64 //src/... //third_party/utf8_range/...
@@ -366,7 +366,7 @@ jobs:
         include:
           # TODO: investigate and fix
           # - name: MacOS CMake
-          #   os: macos-12
+          #   os: macos-13
           #   flags: -DCMAKE_CXX_STANDARD=14
           #   cache-prefix: macos-cmake
           - name: Windows CMake
diff --git a/.github/workflows/test_objectivec.yml b/.github/workflows/test_objectivec.yml
index ab3a5af4b37ce..e4d7a205d2dec 100644
--- a/.github/workflows/test_objectivec.yml
+++ b/.github/workflows/test_objectivec.yml
@@ -25,11 +25,11 @@ jobs:
           destination: "platform=macOS"
           xc_project: "ProtocolBuffers_OSX.xcodeproj"
         - platform: "iOS"
-          destination: "platform=iOS Simulator,name=iPhone 13,OS=latest"
+          destination: "platform=iOS Simulator,name=iPhone 14,OS=latest"
           xc_project: "ProtocolBuffers_iOS.xcodeproj"
 
     name: Xcode ${{ matrix.platform}} ${{ matrix.xc_config }}
-    runs-on: macos-12
+    runs-on: macos-13
     env:
       DEVELOPER_DIR: /Applications/Xcode_14.1.app/Contents/Developer
     steps:
@@ -71,7 +71,7 @@ jobs:
         PLATFORM: ["ios", "macos", "tvos", "watchos", "visionos"]
         CONFIGURATION: ["Debug", "Release"]
         include:
-          - OS: macos-12
+          - OS: macos-13
             XCODE: "14.1"
           - OS: macos-14
             PLATFORM: "visionos"
@@ -123,7 +123,7 @@ jobs:
         - platform: "macOS"
           bazel_targets: //objectivec/...
     name: Bazel ${{ matrix.platform }} ${{ matrix.config.name }}
-    runs-on: macos-12
+    runs-on: macos-13
     steps:
       - name: Checkout pending changes
         uses: protocolbuffers/protobuf-ci/checkout@v3
diff --git a/.github/workflows/test_php.yml b/.github/workflows/test_php.yml
index 86d24954b2c81..d3e77b4b42fb3 100644
--- a/.github/workflows/test_php.yml
+++ b/.github/workflows/test_php.yml
@@ -158,7 +158,7 @@ jobs:
         version: ['8.2', '8.3']
 
     name: MacOS PHP ${{ matrix.version }}
-    runs-on: macos-12
+    runs-on: macos-13
     steps:
       - name: Checkout pending changes
         uses: protocolbuffers/protobuf-ci/checkout@v3
diff --git a/.github/workflows/test_python.yml b/.github/workflows/test_python.yml
index b48da36aabf2b..db7074493f56b 100644
--- a/.github/workflows/test_python.yml
+++ b/.github/workflows/test_python.yml
@@ -65,7 +65,7 @@ jobs:
             flags: --define=use_fast_cpp_protos=true
 
     name: MacOS ${{ matrix.type }} ${{ matrix.version }}
-    runs-on: macos-12
+    runs-on: macos-13
     steps:
       - name: Checkout pending changes
         uses: protocolbuffers/protobuf-ci/checkout@v3
diff --git a/.github/workflows/test_ruby.yml b/.github/workflows/test_ruby.yml
index 8d754189ce916..22bee1e970cd6 100644
--- a/.github/workflows/test_ruby.yml
+++ b/.github/workflows/test_ruby.yml
@@ -128,7 +128,7 @@ jobs:
         - { version: "3.3", ffi: FFI }
 
     name: MacOS Ruby ${{ matrix.version }}${{ matrix.ffi == 'FFI' && ' FFI' || '' }}
-    runs-on: macos-12
+    runs-on: macos-13
     steps:
       - name: Checkout pending changes
         uses: protocolbuffers/protobuf-ci/checkout@v3
diff --git a/.github/workflows/test_upb.yml b/.github/workflows/test_upb.yml
index 7490e75f754d2..bef06d2da3452 100644
--- a/.github/workflows/test_upb.yml
+++ b/.github/workflows/test_upb.yml
@@ -95,7 +95,7 @@ jobs:
           - { name: "macOS", bazel-command: "test" }
           - { name: "macOS ARM (build only)", bazel-command: "build", flags: "--cpu=darwin_arm64" }
     name: ${{ matrix.config.name }}
-    runs-on: macos-12
+    runs-on: macos-13
     steps:
       - name: Checkout pending changes
         uses: protocolbuffers/protobuf-ci/checkout@v3
@@ -103,6 +103,7 @@ jobs:
           ref: ${{ inputs.safe-checkout }}
       - uses: actions/setup-python@61a6322f88396a6271a6ee3565807d608ecaddd1 # v4.7.0
         with:
+          python-version: 3.12
           cache: pip
           cache-dependency-path: 'python/requirements.txt'
       - name: Run tests
@@ -175,11 +176,11 @@ jobs:
           # supported Python versions and assume this gives us sufficient test
           # coverage.
           - { os: ubuntu-latest, python-version: "3.8", architecture: x64, type: 'binary' }
-          - { os: macos-12, python-version: "3.8", architecture: x64, type: 'binary' }
+          - { os: macos-13, python-version: "3.8", architecture: x64, type: 'binary' }
           - { os: ubuntu-latest, python-version: "3.12", architecture: x64, type: 'binary' }
           - { os: macos-13, python-version: "3.12", architecture: x64, type: 'binary' }
           - { os: ubuntu-latest, python-version: "3.8", architecture: x64, type: 'source' }
-          - { os: macos-12, python-version: "3.8", architecture: x64, type: 'source' }
+          - { os: macos-13, python-version: "3.8", architecture: x64, type: 'source' }
           - { os: ubuntu-latest, python-version: "3.12", architecture: x64, type: 'source' }
           - { os: macos-13, python-version: "3.12", architecture: x64, type: 'source' }
 
diff --git a/php/ext/google/protobuf/php-upb.c b/php/ext/google/protobuf/php-upb.c
index 964f53ce57092..a3cf23a569eed 100644
--- a/php/ext/google/protobuf/php-upb.c
+++ b/php/ext/google/protobuf/php-upb.c
@@ -6161,7 +6161,7 @@ upb_Array* upb_Array_DeepClone(const upb_Array* array, upb_CType value_type,
   for (size_t i = 0; i < size; ++i) {
     upb_MessageValue val = upb_Array_Get(array, i);
     if (!upb_Clone_MessageValue(&val, value_type, sub, arena)) {
-      return false;
+      return NULL;
     }
     upb_Array_Set(cloned_array, i, val);
   }
@@ -12204,9 +12204,35 @@ upb_Extension* UPB_PRIVATE(_upb_Message_GetOrCreateExtension)(
 
 // Must be last.
 
-const float kUpb_FltInfinity = INFINITY;
-const double kUpb_Infinity = INFINITY;
-const double kUpb_NaN = NAN;
+// The latest win32 SDKs have an invalid definition of NAN.
+// https://developercommunity.visualstudio.com/t/NAN-is-no-longer-compile-time-constant-i/10688907
+//
+// Unfortunately, the `0.0 / 0.0` workaround doesn't work in Clang under C23, so
+// try __builtin_nan first, if that exists.
+#ifdef _WIN32
+#ifdef __has_builtin
+#if __has_builtin(__builtin_nan)
+#define UPB_NAN __builtin_nan("0")
+#endif
+#if __has_builtin(__builtin_inf)
+#define UPB_INFINITY __builtin_inf()
+#endif
+#endif
+#ifndef UPB_NAN
+#define UPB_NAN 0.0 / 0.0
+#endif
+#ifndef UPB_INFINITY
+#define UPB_INFINITY 1.0 / 0.0
+#endif
+#else
+// For !_WIN32, assume math.h works.
+#define UPB_NAN NAN
+#define UPB_INFINITY INFINITY
+#endif
+
+const float kUpb_FltInfinity = UPB_INFINITY;
+const double kUpb_Infinity = UPB_INFINITY;
+const double kUpb_NaN = UPB_NAN;
 
 bool UPB_PRIVATE(_upb_Message_Realloc)(struct upb_Message* msg, size_t need,
                                        upb_Arena* a) {
diff --git a/ruby/ext/google/protobuf_c/ruby-upb.c b/ruby/ext/google/protobuf_c/ruby-upb.c
index 98715cb8d2b8d..4787dcf984477 100644
--- a/ruby/ext/google/protobuf_c/ruby-upb.c
+++ b/ruby/ext/google/protobuf_c/ruby-upb.c
@@ -5649,7 +5649,7 @@ upb_Array* upb_Array_DeepClone(const upb_Array* array, upb_CType value_type,
   for (size_t i = 0; i < size; ++i) {
     upb_MessageValue val = upb_Array_Get(array, i);
     if (!upb_Clone_MessageValue(&val, value_type, sub, arena)) {
-      return false;
+      return NULL;
     }
     upb_Array_Set(cloned_array, i, val);
   }
@@ -11692,9 +11692,35 @@ upb_Extension* UPB_PRIVATE(_upb_Message_GetOrCreateExtension)(
 
 // Must be last.
 
-const float kUpb_FltInfinity = INFINITY;
-const double kUpb_Infinity = INFINITY;
-const double kUpb_NaN = NAN;
+// The latest win32 SDKs have an invalid definition of NAN.
+// https://developercommunity.visualstudio.com/t/NAN-is-no-longer-compile-time-constant-i/10688907
+//
+// Unfortunately, the `0.0 / 0.0` workaround doesn't work in Clang under C23, so
+// try __builtin_nan first, if that exists.
+#ifdef _WIN32
+#ifdef __has_builtin
+#if __has_builtin(__builtin_nan)
+#define UPB_NAN __builtin_nan("0")
+#endif
+#if __has_builtin(__builtin_inf)
+#define UPB_INFINITY __builtin_inf()
+#endif
+#endif
+#ifndef UPB_NAN
+#define UPB_NAN 0.0 / 0.0
+#endif
+#ifndef UPB_INFINITY
+#define UPB_INFINITY 1.0 / 0.0
+#endif
+#else
+// For !_WIN32, assume math.h works.
+#define UPB_NAN NAN
+#define UPB_INFINITY INFINITY
+#endif
+
+const float kUpb_FltInfinity = UPB_INFINITY;
+const double kUpb_Infinity = UPB_INFINITY;
+const double kUpb_NaN = UPB_NAN;
 
 bool UPB_PRIVATE(_upb_Message_Realloc)(struct upb_Message* msg, size_t need,
                                        upb_Arena* a) {
diff --git a/upb/message/copy.c b/upb/message/copy.c
index 67e1b5b5030d0..94f41056355e5 100644
--- a/upb/message/copy.c
+++ b/upb/message/copy.c
@@ -150,7 +150,7 @@ upb_Array* upb_Array_DeepClone(const upb_Array* array, upb_CType value_type,
   for (size_t i = 0; i < size; ++i) {
     upb_MessageValue val = upb_Array_Get(array, i);
     if (!upb_Clone_MessageValue(&val, value_type, sub, arena)) {
-      return false;
+      return NULL;
     }
     upb_Array_Set(cloned_array, i, val);
   }
diff --git a/upb/message/internal/message.c b/upb/message/internal/message.c
index 57ab2d7371cdb..45b1067db1c95 100644
--- a/upb/message/internal/message.c
+++ b/upb/message/internal/message.c
@@ -17,9 +17,35 @@
 // Must be last.
 #include "upb/port/def.inc"
 
-const float kUpb_FltInfinity = INFINITY;
-const double kUpb_Infinity = INFINITY;
-const double kUpb_NaN = NAN;
+// The latest win32 SDKs have an invalid definition of NAN.
+// https://developercommunity.visualstudio.com/t/NAN-is-no-longer-compile-time-constant-i/10688907
+//
+// Unfortunately, the `0.0 / 0.0` workaround doesn't work in Clang under C23, so
+// try __builtin_nan first, if that exists.
+#ifdef _WIN32
+#ifdef __has_builtin
+#if __has_builtin(__builtin_nan)
+#define UPB_NAN __builtin_nan("0")
+#endif
+#if __has_builtin(__builtin_inf)
+#define UPB_INFINITY __builtin_inf()
+#endif
+#endif
+#ifndef UPB_NAN
+#define UPB_NAN 0.0 / 0.0
+#endif
+#ifndef UPB_INFINITY
+#define UPB_INFINITY 1.0 / 0.0
+#endif
+#else
+// For !_WIN32, assume math.h works.
+#define UPB_NAN NAN
+#define UPB_INFINITY INFINITY
+#endif
+
+const float kUpb_FltInfinity = UPB_INFINITY;
+const double kUpb_Infinity = UPB_INFINITY;
+const double kUpb_NaN = UPB_NAN;
 
 bool UPB_PRIVATE(_upb_Message_Realloc)(struct upb_Message* msg, size_t need,
                                        upb_Arena* a) {
diff --git a/upb/text/internal/encode.c b/upb/text/internal/encode.c
index fc9cc6fd27373..403da037e4f3a 100644
--- a/upb/text/internal/encode.c
+++ b/upb/text/internal/encode.c
@@ -22,11 +22,11 @@
 // Must be last.
 #include "upb/port/def.inc"
 
-#define CHK(x)      \
-  do {              \
-    if (!(x)) {     \
-      return false; \
-    }               \
+#define CHK(x)     \
+  do {             \
+    if (!(x)) {    \
+      return NULL; \
+    }              \
   } while (0)
 
 /*
@@ -177,4 +177,4 @@ void UPB_PRIVATE(_upb_TextEncode_Scalar)(txtenc* e, upb_MessageValue val,
     default:
       UPB_UNREACHABLE();
   }
-}
\ No newline at end of file
+}