diff --git a/Source/cmCxxModuleUsageEffects.cxx b/Source/cmCxxModuleUsageEffects.cxx
index 9684309193..1130c37fdf 100644
--- a/Source/cmCxxModuleUsageEffects.cxx
+++ b/Source/cmCxxModuleUsageEffects.cxx
@@ -4,15 +4,16 @@
 
 #include <algorithm>
 #include <set>
+#include <utility>
 #include <vector>
 
 #include <cm/string_view>
+#include <cmext/string_view>
 
 #include "cmCryptoHash.h"
 #include "cmGeneratorTarget.h"
 #include "cmListFileCache.h"
 #include "cmMakefile.h"
-#include "cmRange.h"
 #include "cmStringAlgorithms.h"
 #include "cmTarget.h"
 #include "cmValue.h"
@@ -70,34 +71,6 @@ bool IsGNUWarning(cm::string_view flag)
   return long_names.find(flag) != long_names.end();
 }
 
-bool UnknownFilter(cm::string_view)
-{
-  return false;
-}
-
-using FlagFilter = bool (*)(cm::string_view flag);
-
-FlagFilter GetFlagFilter(cmGeneratorTarget const* gt)
-{
-  static FlagFilter filter = nullptr;
-  if (filter) {
-    return filter;
-  }
-
-  cmValue frontendVariant =
-    gt->Makefile->GetDefinition("CMAKE_CXX_COMPILER_FRONTEND_VARIANT");
-
-  if (frontendVariant == "GNU") {
-    filter = IsGNUWarning;
-  } else if (frontendVariant == "MSVC") {
-    filter = IsMSVCWarning;
-  } else {
-    filter = UnknownFilter;
-  }
-
-  return filter;
-}
-
 void AppendUsage(std::string& usageHashInput, std::string const& entry)
 {
   usageHashInput += entry;
@@ -121,28 +94,216 @@ void AppendUsageEntries(std::string& usageHashInput, Range const& entries)
 
   usageHashInput.push_back('\0');
 }
+
+enum class CompileOptionUsage
+{
+  Hash,
+  Ignore,
+  SavePreprocessor,
+};
+
+struct CompileOptionClassification
+{
+  CompileOptionClassification(
+    CompileOptionUsage usage = CompileOptionUsage::Hash,
+    bool saveFollowingArgument = false)
+    : Usage(usage)
+    , SaveFollowingArgument(saveFollowingArgument)
+  {
+  }
+
+  CompileOptionUsage Usage = CompileOptionUsage::Hash;
+  bool SaveFollowingArgument = false;
+};
+
+CompileOptionClassification SaveIfStartsWith(cm::string_view flag,
+                                             cm::string_view prefix)
+{
+  if (flag.rfind(prefix, 0) == 0) {
+    return { CompileOptionUsage::SavePreprocessor,
+             flag.size() == prefix.size() };
+  }
+
+  return {};
+}
+
+CompileOptionClassification ClassifyGNUCompileOption(cm::string_view flag)
+{
+  if (IsGNUWarning(flag)) {
+    return { CompileOptionUsage::Ignore, false };
+  }
+
+  if (flag.size() < 2 || flag.front() != '-') {
+    return {};
+  }
+
+  flag.remove_prefix(1);
+  switch (flag.front()) {
+    case 'D':
+    case 'I':
+    case 'U':
+      return { CompileOptionUsage::SavePreprocessor, flag.size() == 1 };
+    case 'i': {
+      CompileOptionClassification classification =
+        SaveIfStartsWith(flag, "isystem"_s);
+      if (classification.Usage != CompileOptionUsage::Hash) {
+        return classification;
+      }
+    }
+      {
+        CompileOptionClassification classification =
+          SaveIfStartsWith(flag, "iquote"_s);
+        if (classification.Usage != CompileOptionUsage::Hash) {
+          return classification;
+        }
+      }
+      {
+        CompileOptionClassification classification =
+          SaveIfStartsWith(flag, "idirafter"_s);
+        if (classification.Usage != CompileOptionUsage::Hash) {
+          return classification;
+        }
+      }
+      {
+        CompileOptionClassification classification =
+          SaveIfStartsWith(flag, "include"_s);
+        if (classification.Usage != CompileOptionUsage::Hash) {
+          return classification;
+        }
+      }
+      {
+        CompileOptionClassification classification =
+          SaveIfStartsWith(flag, "imacros"_s);
+        if (classification.Usage != CompileOptionUsage::Hash) {
+          return classification;
+        }
+      }
+      break;
+    case '-':
+      flag.remove_prefix(1);
+      return SaveIfStartsWith(flag, "embed-dir"_s);
+    default:
+      break;
+  }
+
+  return {};
+}
+
+CompileOptionClassification ClassifyMSVCCompileOption(cm::string_view flag)
+{
+  if (IsMSVCWarning(flag)) {
+    return { CompileOptionUsage::Ignore, false };
+  }
+
+  if (flag.size() < 2 || (flag.front() != '/' && flag.front() != '-')) {
+    return {};
+  }
+
+  flag.remove_prefix(1);
+  switch (flag.front()) {
+    case 'D':
+    case 'I':
+    case 'U':
+      return { CompileOptionUsage::SavePreprocessor, flag.size() == 1 };
+    default:
+      break;
+  }
+
+  return {};
+}
+
+CompileOptionClassification ClassifyUnknownCompileOption(cm::string_view flag)
+{
+  static_cast<void>(flag);
+  return {};
+}
+
+using CompileOptionClassifier =
+  CompileOptionClassification (*)(cm::string_view flag);
+
+CompileOptionClassifier GetCompileOptionClassifier(cmGeneratorTarget const* gt)
+{
+  static CompileOptionClassifier classifier = nullptr;
+  if (classifier) {
+    return classifier;
+  }
+
+  cmValue frontendVariant =
+    gt->Makefile->GetDefinition("CMAKE_CXX_COMPILER_FRONTEND_VARIANT");
+
+  if (frontendVariant == "GNU") {
+    classifier = ClassifyGNUCompileOption;
+  } else if (frontendVariant == "MSVC") {
+    classifier = ClassifyMSVCCompileOption;
+  } else {
+    classifier = ClassifyUnknownCompileOption;
+  }
+
+  return classifier;
+}
+
+struct SplitCompileOptionsResult
+{
+  std::vector<BT<std::string>> HashEntries;
+  std::vector<BT<std::string>> PreprocessorEntries;
+};
+
+template <typename Range>
+SplitCompileOptionsResult SplitCompileOptions(Range const& entries,
+                                              CompileOptionClassifier classify)
+{
+  SplitCompileOptionsResult result;
+
+  for (auto it = entries.begin(); it != entries.end(); ++it) {
+    BT<std::string> const& option = *it;
+    auto const classification = classify(option.Value);
+
+    switch (classification.Usage) {
+      case CompileOptionUsage::Ignore:
+        continue;
+      case CompileOptionUsage::SavePreprocessor:
+        result.PreprocessorEntries.push_back(option);
+        if (classification.SaveFollowingArgument) {
+          auto next = it;
+          ++next;
+          if (next != entries.end()) {
+            result.PreprocessorEntries.push_back(*next);
+            it = next;
+          }
+        }
+        continue;
+      case CompileOptionUsage::Hash:
+        break;
+    }
+
+    result.HashEntries.push_back(option);
+  }
+
+  return result;
+}
 }
 
 cmCxxModuleUsageEffects::cmCxxModuleUsageEffects(cmGeneratorTarget const* gt,
                                                  std::string const& config)
 {
   auto const* tgt = gt->Target;
-  auto const filter = GetFlagFilter(gt);
+  auto const classify = GetCompileOptionClassifier(gt);
 
   std::string usageHashInput;
   if (tgt->IsImported()) {
     AppendUsageEntries(usageHashInput,
                        tgt->GetImportedCxxModulesCompileFeaturesEntries());
-    AppendUsageEntries(
-      usageHashInput,
-      tgt->GetImportedCxxModulesCompileOptionsEntries().filter(
-        [&](const BT<std::string>& flag) { return !filter(flag.Value); }));
+    auto compileOptions = SplitCompileOptions(
+      tgt->GetImportedCxxModulesCompileOptionsEntries(), classify);
+    this->PreprocessorCompileOptions =
+      std::move(compileOptions.PreprocessorEntries);
+    AppendUsageEntries(usageHashInput, compileOptions.HashEntries);
   } else {
-    AppendUsageEntries(usageHashInput,
-                       cmMakeRange(gt->GetCompileOptions(config, "CXX"))
-                         .filter([&](const BT<std::string>& flag) {
-                           return !filter(flag.Value);
-                         }));
+    auto compileOptions =
+      SplitCompileOptions(gt->GetCompileOptions(config, "CXX"), classify);
+    this->PreprocessorCompileOptions =
+      std::move(compileOptions.PreprocessorEntries);
+    AppendUsageEntries(usageHashInput, compileOptions.HashEntries);
 
     cmValue langStd = gt->GetLanguageStandard("CXX", config);
     if (!langStd) {
@@ -167,3 +328,9 @@ std::string const& cmCxxModuleUsageEffects::GetHash() const
 {
   return this->Hash;
 }
+
+std::vector<BT<std::string>> const&
+cmCxxModuleUsageEffects::GetPreprocessorCompileOptions() const
+{
+  return this->PreprocessorCompileOptions;
+}
diff --git a/Source/cmCxxModuleUsageEffects.h b/Source/cmCxxModuleUsageEffects.h
index 1fd190f22f..8b8c50f610 100644
--- a/Source/cmCxxModuleUsageEffects.h
+++ b/Source/cmCxxModuleUsageEffects.h
@@ -5,6 +5,9 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <string>
+#include <vector>
+
+#include "cmListFileCache.h"
 
 class cmGeneratorTarget;
 
@@ -14,7 +17,9 @@ public:
   cmCxxModuleUsageEffects(cmGeneratorTarget const* gt,
                           std::string const& config);
   std::string const& GetHash() const;
+  std::vector<BT<std::string>> const& GetPreprocessorCompileOptions() const;
 
 private:
   std::string Hash;
+  std::vector<BT<std::string>> PreprocessorCompileOptions;
 };
diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 62af48f8a3..0af9983971 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -5565,6 +5565,13 @@ cmGeneratorTarget const* cmGeneratorTarget::GetCxxSyntheticTarget(
   // compile features and options.
   tgt->CopyUsageEffects(&bmiConsumer, config);
 
+  auto const& preprocessorCompileOptions =
+    this->GetCxxModuleUsageEffects(config).GetPreprocessorCompileOptions();
+  for (auto it = preprocessorCompileOptions.rbegin();
+       it != preprocessorCompileOptions.rend(); ++it) {
+    tgt->InsertCompileOption(*it, true);
+  }
+
   // Copy properties which don't effect consumer compatibility
   tgt->CopyCxxModulesEntries(model);
 
diff --git a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all-multi.json b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all-multi.json
index 113680635e..e835f6afe4 100644
--- a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all-multi.json
+++ b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all-multi.json
@@ -185,7 +185,7 @@
         }
       ],
       "visible-sets": [
-        "CXXModules__export_build_database@synth_1@<CONFIG>"
+        "CXXModules__export_build_database@synth_0@<CONFIG>"
       ]
     },
     {
@@ -251,7 +251,7 @@
         }
       ],
       "visible-sets": [
-        "CXXModules__export_build_database@synth_1@<CONFIG_OTHER>"
+        "CXXModules__export_build_database@synth_0@<CONFIG_OTHER>"
       ]
     },
     {
@@ -275,8 +275,10 @@
             "-Dfrom_cmake_cxx_flags",
             "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
             "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
+            "-Dfrom_compile_options",
+            "-Dtarget_private_option",
             "-Dtarget_public_option",
+            "-Dtarget_interface_option",
             "-Ddep_interface_option",
             "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/.d\"",
             "REGEX:<BMI_ONLY_FLAG>",
@@ -299,8 +301,10 @@
             "-Dfrom_cmake_cxx_flags",
             "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
             "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
+            "-Dfrom_compile_options",
+            "-Dtarget_private_option",
             "-Dtarget_public_option",
+            "-Dtarget_interface_option",
             "-Ddep_interface_option"
           ],
           "local-arguments": [
@@ -318,8 +322,10 @@
             "-Dfrom_cmake_cxx_flags",
             "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
             "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
+            "-Dfrom_compile_options",
+            "-Dtarget_private_option",
             "-Dtarget_public_option",
+            "-Dtarget_interface_option",
             "-Ddep_interface_option"
           ],
           "private": false,
@@ -354,8 +360,10 @@
             "-Dfrom_cmake_cxx_flags",
             "-Dfrom_cmake_cxx_<CONFIG_OTHER_LOWER>_flags",
             "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
+            "-Dfrom_compile_options",
+            "-Dtarget_private_option",
             "-Dtarget_public_option",
+            "-Dtarget_interface_option",
             "-Ddep_interface_option",
             "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_OTHER_DIR>/.d\"",
             "REGEX:<BMI_ONLY_FLAG>",
@@ -363,172 +371,6 @@
             "REGEX:-[cv]",
             "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
           ],
-          "baseline-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_OTHER_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option"
-          ],
-          "local-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_OTHER_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option"
-          ],
-          "private": false,
-          "provides": {
-            "importable": "<IGNORE>"
-          },
-          "requires": [],
-          "source": "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx",
-          "work-directory": "<BINARY_DIR>"
-        }
-      ],
-      "visible-sets": []
-    },
-    {
-      "family-name": "REGEX:CXXModules::export_build_database@<HEX>",
-      "name": "CXXModules__export_build_database@synth_1@<CONFIG>",
-      "translation-units": [
-        {
-          "arguments": [
-            "<IGNORE>",
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dfrom_compile_options",
-            "-Dtarget_private_option",
-            "-Dtarget_public_option",
-            "-Dtarget_interface_option",
-            "-Ddep_interface_option",
-            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_DIR>/.d\"",
-            "REGEX:<BMI_ONLY_FLAG>",
-            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_DIR>/",
-            "REGEX:-[cv]",
-            "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
-          ],
-          "baseline-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dfrom_compile_options",
-            "-Dtarget_private_option",
-            "-Dtarget_public_option",
-            "-Dtarget_interface_option",
-            "-Ddep_interface_option"
-          ],
-          "local-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dfrom_compile_options",
-            "-Dtarget_private_option",
-            "-Dtarget_public_option",
-            "-Dtarget_interface_option",
-            "-Ddep_interface_option"
-          ],
-          "private": false,
-          "provides": {
-            "importable": "<IGNORE>"
-          },
-          "requires": [],
-          "source": "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx",
-          "work-directory": "<BINARY_DIR>"
-        }
-      ],
-      "visible-sets": []
-    },
-    {
-      "family-name": "REGEX:CXXModules::export_build_database@<HEX>",
-      "name": "CXXModules__export_build_database@synth_1@<CONFIG_OTHER>",
-      "translation-units": [
-        {
-          "arguments": [
-            "<IGNORE>",
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_OTHER_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dfrom_compile_options",
-            "-Dtarget_private_option",
-            "-Dtarget_public_option",
-            "-Dtarget_interface_option",
-            "-Ddep_interface_option",
-            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_OTHER_DIR>/.d\"",
-            "REGEX:<BMI_ONLY_FLAG>",
-            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_OTHER_DIR>/",
-            "REGEX:-[cv]",
-            "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
-          ],
           "baseline-arguments": [
             "-D_MBCS",
             "-Ddep_interface_define",
diff --git a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all.json b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all.json
index 83cef7942a..1f50bfaf59 100644
--- a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all.json
+++ b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-all.json
@@ -125,91 +125,12 @@
         }
       ],
       "visible-sets": [
-        "CXXModules__export_build_database@synth_1@<CONFIG>"
+        "CXXModules__export_build_database@synth_0@<CONFIG>"
       ]
     },
     {
       "family-name": "REGEX:CXXModules::export_build_database@<HEX>",
       "name": "CXXModules__export_build_database@synth_0@<CONFIG>",
-      "translation-units": [
-        {
-          "arguments": [
-            "<IGNORE>",
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option",
-            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/.d\"",
-            "REGEX:<BMI_ONLY_FLAG>",
-            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/",
-            "REGEX:-[cv]",
-            "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
-          ],
-          "baseline-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option"
-          ],
-          "local-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
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-            "-Dtarget_public_option",
-            "-Ddep_interface_option",
-            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/.d\"",
-            "REGEX:<BMI_ONLY_FLAG>",
-            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/",
-            "REGEX:-[cv]",
-            "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
-          ],
-          "baseline-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option"
-          ],
-          "local-arguments": [
-            "-D_MBCS",
-            "-Ddep_interface_define",
-            "-Dfrom_compile_definitions",
-            "-Dtarget_interface_define",
-            "-Dtarget_private_define",
-            "-Dtarget_public_define",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/from_include_directories",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_private_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_public_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/dep_interface_include",
-            "PATH:-I<SOURCE_DIR>/exp-builddb/target_interface_include",
-            "-Dfrom_cmake_cxx_flags",
-            "-Dfrom_cmake_cxx_<CONFIG_LOWER>_flags",
-            "<CXX20_OPTION>",
-            "-Dtarget_interface_option",
-            "-Dtarget_public_option",
-            "-Ddep_interface_option"
-          ],
-          "private": false,
-          "provides": {
-            "importable": "<IGNORE>"
-          },
-          "requires": [],
-          "source": "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx",
-          "work-directory": "<BINARY_DIR>"
-        }
-      ],
-      "visible-sets": []
-    },
-    {
-      "family-name": "REGEX:CXXModules::export_build_database@<HEX>",
-      "name": "CXXModules__export_build_database@synth_1@<CONFIG>",
       "translation-units": [
         {
           "arguments": [
@@ -233,9 +154,9 @@
             "-Dtarget_public_option",
             "-Dtarget_interface_option",
             "-Ddep_interface_option",
-            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_DIR>/.d\"",
+            "PATH:-Ddepflag=\"CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/.d\"",
             "REGEX:<BMI_ONLY_FLAG>",
-            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_1.dir<CONFIG_DIR>/",
+            "PATH:<OUTPUT_FLAG>CMakeFiles/CXXModules__export_build_database@synth_0.dir<CONFIG_DIR>/",
             "REGEX:-[cv]",
             "PATH:<SOURCE_DIR>/exp-builddb/importable.cxx"
           ],
diff --git a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-matching-target.json b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-matching-target.json
index 6154715b57..e6d2629b58 100644
--- a/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-matching-target.json
+++ b/Tests/RunCMake/CXXModulesCompile/expect/exp-builddb-imped-matching-target.json
@@ -65,7 +65,7 @@
         }
       ],
       "visible-sets": [
-        "CXXModules__export_build_database@synth_1@<CONFIG>"
+        "CXXModules__export_build_database@synth_0@<CONFIG>"
       ]
     }
   ]
diff --git a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility-build-check.cmake b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility-build-check.cmake
index 810364da78..8728c7a2cc 100644
--- a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility-build-check.cmake
+++ b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility-build-check.cmake
@@ -1,8 +1,8 @@
-# Verify the build system reused the owning target BMI when compatible and
-# generated a synthetic target BMI only for the incompatible importer.
-set(expected_consumers consumer20 consumer23)
-set(linked_dir_keys "")
-set(linked_dir_names "")
+# Verify the build system reused the owning target BMI when compatible,
+# generated a shared synthetic target BMI for the incompatible importers,
+# and ignored preprocessor-only compile options in the BMI compatibility hash.
+set(expected_consumers consumer20 consumer23 consumer23flag)
+set(shared_synth_target_name "")
 
 if (DEFINED RunCMake_TEST_CONFIG)
   set(config_dir "${RunCMake_TEST_CONFIG}")
@@ -36,9 +36,10 @@ foreach (consumer IN LISTS expected_consumers)
     set(expected_linked_tgt_regex "^importable\.dir$")
     set(expected_linked_tgt_desc "owning target dir for 'importable'")
     set(expected_linked_tgt_has_bmi 0)
-  elseif (consumer STREQUAL "consumer23")
+  elseif (consumer STREQUAL "consumer23" OR
+          consumer STREQUAL "consumer23flag")
     set(expected_linked_tgt_regex "^importable@synth_[A-Za-z0-9_]+\.dir$")
-    set(expected_linked_tgt_desc "synthetic target dir for 'importable'")
+    set(expected_linked_tgt_desc "shared synthetic target dir for 'importable'")
     set(expected_linked_tgt_has_bmi 1)
   else ()
     list(APPEND RunCMake_TEST_FAILED
@@ -97,33 +98,15 @@ foreach (consumer IN LISTS expected_consumers)
     endif ()
   endif ()
 
-  if (linked_tgt_name MATCHES "^importable@synth_[A-Za-z0-9_]+\.dir$")
-    # Record the consumers of each synthetic dir to verify uniqueness.
-    string(REGEX REPLACE "[^A-Za-z0-9_]" "_" linked_dir_key "${linked_tgt_name}")
-    set(linked_dir_consumers_var "linked_dir_consumers_${linked_dir_key}")
-    if (NOT DEFINED ${linked_dir_consumers_var})
-      list(APPEND linked_dir_keys "${linked_dir_key}")
-      list(APPEND linked_dir_names "${linked_tgt_name}")
+  if (consumer STREQUAL "consumer23" OR consumer STREQUAL "consumer23flag")
+    if (shared_synth_target_name STREQUAL "")
+      set(shared_synth_target_name "${linked_tgt_name}")
+    elseif (NOT linked_tgt_name STREQUAL shared_synth_target_name)
+      list(APPEND RunCMake_TEST_FAILED
+        "Expected consumer23 and consumer23flag to share one synthetic target dir, but found '${shared_synth_target_name}' and '${linked_tgt_name}'")
     endif ()
-
-    list(APPEND ${linked_dir_consumers_var} ${consumer})
   endif ()
 
 endforeach ()
 
-# Verify each synthetic target is consumed exactly once.
-foreach (linked_dir_key IN LISTS linked_dir_keys)
-  set(consumers "${linked_dir_consumers_${linked_dir_key}}")
-  list(LENGTH consumers linked_dir_consumer_count)
-
-  if (linked_dir_consumer_count GREATER 1)
-    list(FIND linked_dir_keys ${linked_dir_key} linked_dir_index)
-    list(GET linked_dir_names ${linked_dir_index} linked_tgt_name)
-
-    string(JOIN ", " linked_dir_consumers_joined ${consumers})
-    list(APPEND RunCMake_TEST_FAILED
-      "Expected per-compatibility synthetic BMI generation, but '${linked_tgt_name}' is linked to by multiple targets: ${linked_dir_consumers_joined}")
-  endif ()
-endforeach ()
-
 string(REPLACE ";" "\n  " RunCMake_TEST_FAILED "${RunCMake_TEST_FAILED}")
diff --git a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/CMakeLists.txt b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/CMakeLists.txt
index 4af50c8459..794c0de4b6 100644
--- a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/CMakeLists.txt
@@ -8,6 +8,7 @@ target_sources(importable
   PUBLIC FILE_SET CXX_MODULES FILES importable.cxx)
 
 target_compile_features(importable PUBLIC cxx_std_20)
+target_compile_options(importable PRIVATE "-DIMPORTABLE_PRIVATE_DEFINE=1")
 
 add_executable(consumer20 consumer20.cxx)
 target_compile_features(consumer20 PRIVATE cxx_std_20)
@@ -17,5 +18,11 @@ add_executable(consumer23 consumer23.cxx)
 target_compile_features(consumer23 PRIVATE cxx_std_23)
 target_link_libraries(consumer23 PRIVATE importable)
 
+add_executable(consumer23flag consumer23.cxx)
+target_compile_features(consumer23flag PRIVATE cxx_std_23)
+target_compile_options(consumer23flag PRIVATE "-DCONSUMER23FLAG_ONLY=1")
+target_link_libraries(consumer23flag PRIVATE importable)
+
 add_test(NAME consumer20 COMMAND consumer20)
 add_test(NAME consumer23 COMMAND consumer23)
+add_test(NAME consumer23flag COMMAND consumer23flag)
diff --git a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/importable.cxx b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/importable.cxx
index 607680a07c..f2a7908901 100644
--- a/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/importable.cxx
+++ b/Tests/RunCMake/CXXModulesCompile/mixed-bmi-compatibility/importable.cxx
@@ -1,5 +1,9 @@
 export module importable;
 
+#ifndef IMPORTABLE_PRIVATE_DEFINE
+#  error "missing private compile option required for BMI generation"
+#endif
+
 export int from_import()
 {
   return 0;