hiroyuki-komatsu · May 10, 2026 · May 2, 2026
diff --git a/src/win32/base/tsf_registrar.cc b/src/win32/base/tsf_registrar.cc
@@ -56,6 +56,22 @@ constexpr wchar_t kTipInProcServer32[] = L"InProcServer32";
 constexpr wchar_t kTipThreadingModel[] = L"ThreadingModel";
 constexpr wchar_t kTipTextServiceModel[] = L"Apartment";
 
+constexpr REGSAM AdjustRegFlagBitness(REGSAM base_flags,
+                                      COMServerBitness bitness) {
+  REGSAM flags = base_flags;
+  switch (bitness) {
+    case COMServerBitness::k32bit:
+      flags |= KEY_WOW64_32KEY;
+      flags &= ~KEY_WOW64_64KEY;
+      break;
+    case COMServerBitness::k64bit:
+      flags |= KEY_WOW64_64KEY;
+      flags &= ~KEY_WOW64_32KEY;
+      break;
+  }
+  return flags;
+}
+
 // The categories this text service is registered under.
 // This needs to be const as the included constants are defined as const.
 const GUID kCategories[] = {
@@ -78,10 +94,12 @@ const GUID kCategories[] = {
 //   * The description of this module;
 //   * The path to this module, and;
 //   * The type of this module (threading moddel).
-HRESULT TsfRegistrar::RegisterCOMServer(const wchar_t* path, DWORD length) {
+HRESULT TsfRegistrar::RegisterCOMServer(const wchar_t* path, DWORD length,
+                                        COMServerBitness bitness) {
   if (length == 0) {
     return E_OUTOFMEMORY;
   }
+  const REGSAM reg_flags = AdjustRegFlagBitness(KEY_READ | KEY_WRITE, bitness);
   // Open the registry key "HKEY_CLASSES_ROOT\CLSID", which stores information
   // of all COM modules installed in this PC.
   // To register a COM module to Windows, we should create a key of its GUID
@@ -92,7 +110,7 @@ HRESULT TsfRegistrar::RegisterCOMServer(const wchar_t* path, DWORD length) {
   //  * The threading model of this module.
   ATL::CRegKey parent;
   LONG result = parent.Open(HKEY_CLASSES_ROOT, &kTipInfoKeyPrefix[0],
-                            KEY_READ | KEY_WRITE);
+                            reg_flags);
   if (result != ERROR_SUCCESS) {
     return HRESULT_FROM_WIN32(result);
   }
@@ -107,7 +125,7 @@ HRESULT TsfRegistrar::RegisterCOMServer(const wchar_t* path, DWORD length) {
 
   ATL::CRegKey key;
   result = key.Create(parent, &ime_key[0], REG_NONE, REG_OPTION_NON_VOLATILE,
-                      KEY_READ | KEY_WRITE, nullptr, nullptr);
+                      reg_flags, nullptr, nullptr);
   if (result != ERROR_SUCCESS) {
     return HRESULT_FROM_WIN32(result);
   }
@@ -138,7 +156,7 @@ HRESULT TsfRegistrar::RegisterCOMServer(const wchar_t* path, DWORD length) {
 // Unregisters this module from Windows.
 // This function just deletes the all registry keys under
 // "HKCR\CLSID\{xxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx}".
-void TsfRegistrar::UnregisterCOMServer() {
+void TsfRegistrar::UnregisterCOMServer(COMServerBitness bitness) {
   // Create the registry key for this COM server.
   // Only Administrators can create keys under HKEY_CLASSES_ROOT.
   wchar_t ime_key[64] = {};
@@ -147,9 +165,10 @@ void TsfRegistrar::UnregisterCOMServer() {
     return;
   }
 
+  const REGSAM reg_flags = AdjustRegFlagBitness(KEY_READ | KEY_WRITE, bitness);
   ATL::CRegKey key;
-  HRESULT result =
-      key.Open(HKEY_CLASSES_ROOT, &kTipInfoKeyPrefix[0], KEY_READ | KEY_WRITE);
+  HRESULT result = key.Open(HKEY_CLASSES_ROOT, &kTipInfoKeyPrefix[0],
+                            reg_flags);
   if (result != ERROR_SUCCESS) {
     return;
   }

diff --git a/src/win32/base/tsf_registrar.h b/src/win32/base/tsf_registrar.h
@@ -37,6 +37,11 @@
 namespace mozc {
 namespace win32 {
 
+enum class COMServerBitness {
+  k64bit,
+  k32bit,
+};
+
 // Registers Mozc as a text input processor or unregister.
 class TsfRegistrar {
  public:
@@ -45,10 +50,14 @@ class TsfRegistrar {
   TsfRegistrar& operator=(const TsfRegistrar&) = delete;
 
   // Registers the DLL specified with |path| as a COM server.
-  static HRESULT RegisterCOMServer(const wchar_t* path, DWORD length);
+  // |bitness| specifies which registry view to use: k64bit for the native
+  // 64-bit view, k32bit for the WOW6432Node (32-bit) view.
+  static HRESULT RegisterCOMServer(const wchar_t* path, DWORD length,
+                                   COMServerBitness bitness);
 
   // Unregisters the DLL from registry.
-  static void UnregisterCOMServer();
+  // |bitness| specifies which registry view to unregister from.
+  static void UnregisterCOMServer(COMServerBitness bitness);
 
   // Registers this COM server to the profile store for input processors.
   // The caller is responsible for initializing COM before call this function.

diff --git a/src/win32/custom_action/BUILD.bazel b/src/win32/custom_action/BUILD.bazel
@@ -41,10 +41,6 @@ mozc_win32_cc_prod_binary(
         "custom_action.h",
         "resource.h",
     ],
-    defines = select({
-        "//:enable_win_universal_installer": ["MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER"],
-        "//conditions:default": [],
-    }),
     executable_name_map = {
         "Mozc": "mozc_installer_helper.dll",
         "GoogleJapaneseInput": "GoogleIMEJaInstallerHelper.dll",

diff --git a/src/win32/custom_action/custom_action.cc b/src/win32/custom_action/custom_action.cc
@@ -33,11 +33,8 @@
 #include <windows.h>
 #include <atlbase.h>
 #include <msiquery.h>
-// clang-format on
-
-#if defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
 #include <wow64apiset.h>
-#endif  // defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
+// clang-format on
 
 #undef StrCat  // NOLINT: TODO: triggers clang-tidy, defined by windows.h.
 
@@ -457,44 +454,43 @@ UINT __stdcall RegisterTIP(MSIHANDLE msi_handle) {
   mozc::ScopedCOMInitializer com_initializer;
   HRESULT result = S_OK;
 
-#if defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
+  // Register 64-bit TIP COM server.
   // Unlike 32-bit TIP DLL, which is always x86, the expected 64-bit TIP DLL
-  // can be x64 or ARM64X depending on the target environment. This is why
-  // only 64-bit TIP DLL is dynamically registered here.
-
-  // |IsWow64Process2| is added in Windows 10 1709 / Windows Server 1709. Let's
-  // check if the API is available before calling it.
-  // TODO: Directly call |IsWow64Process2| after we stop supporting Windows 10.
+  // can be x64 or ARM64X depending on the target environment.
   USHORT process_machine = IMAGE_FILE_MACHINE_UNKNOWN;
   USHORT native_machine = IMAGE_FILE_MACHINE_UNKNOWN;
-  auto IsWow64Process2Func = reinterpret_cast<decltype(&::IsWow64Process2)>(
-      ::GetProcAddress(::GetModuleHandleA("kernel32.dll"), "IsWow64Process2"));
-  if (IsWow64Process2Func != nullptr) [[likely]] {
-    result = IsWow64Process2Func(::GetCurrentProcess(), &process_machine,
-                                 &native_machine);
-  } else {
-    // Fallback to x64.
-    result = E_NOTIMPL;
-  }
+  result = IsWow64Process2(::GetCurrentProcess(), &process_machine,
+                           &native_machine);
   const bool is_arm64_machine =
       SUCCEEDED(result) && native_machine == IMAGE_FILE_MACHINE_ARM64;
-  const std::wstring& tip64_path = GetMozcComponentPath(
+  const std::wstring tip64_path = GetMozcComponentPath(
       is_arm64_machine ? mozc::kMozcTIP64X : mozc::kMozcTIP64);
 
-  result = mozc::win32::TsfRegistrar::RegisterCOMServer(tip64_path.c_str(),
-                                                        tip64_path.length());
+  result = mozc::win32::TsfRegistrar::RegisterCOMServer(
+      tip64_path.c_str(), tip64_path.length(),
+      mozc::win32::COMServerBitness::k64bit);
   if (FAILED(result)) {
     LOG_ERROR_FOR_OMAHA();
     UnregisterTIP(msi_handle);
     return ERROR_INSTALL_FAILURE;
   }
-#endif  // defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
 
+  // Register 32-bit TIP COM server.
+  const std::wstring tip32_path = GetMozcComponentPath(mozc::kMozcTIP32);
+  result = mozc::win32::TsfRegistrar::RegisterCOMServer(
+      tip32_path.c_str(), tip32_path.length(),
+      mozc::win32::COMServerBitness::k32bit);
+  if (FAILED(result)) {
+    LOG_ERROR_FOR_OMAHA();
+    UnregisterTIP(msi_handle);
+    return ERROR_INSTALL_FAILURE;
+  }
+
+  // Register profiles and categories.
   // The path here is to retrieve Win32 resources such as icon and product name,
   // which does not need to match the native CPU architecture. Here we use
   // 32-bit TIP DLL as it is always installed even on an ARM64 target.
-  const std::wstring resource_dll_path = GetMozcComponentPath(mozc::kMozcTIP32);
-  result = mozc::win32::TsfRegistrar::RegisterProfiles(resource_dll_path);
+  result = mozc::win32::TsfRegistrar::RegisterProfiles(tip32_path);
   if (FAILED(result)) {
     LOG_ERROR_FOR_OMAHA();
     UnregisterTIP(msi_handle);
@@ -523,13 +519,10 @@ UINT __stdcall UnregisterTIP(MSIHANDLE msi_handle) {
 
   mozc::win32::TsfRegistrar::UnregisterCategories();
   mozc::win32::TsfRegistrar::UnregisterProfiles();
-
-#if defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
-  // Unlike 32-bit TIP DLL, which is always x86, the expected 64-bit TIP DLL
-  // can be x64 or ARM64X depending on the target environment. This is why
-  // only 64-bit TIP DLL is dynamically unregistered here.
-  mozc::win32::TsfRegistrar::UnregisterCOMServer();
-#endif  // defined(MOZC_ENABLE_WIN_UNIVERSAL_INSTALLER)
+  mozc::win32::TsfRegistrar::UnregisterCOMServer(
+      mozc::win32::COMServerBitness::k64bit);
+  mozc::win32::TsfRegistrar::UnregisterCOMServer(
+      mozc::win32::COMServerBitness::k32bit);
 
   return ERROR_SUCCESS;
 }

diff --git a/src/win32/installer/installer_64bit.wxs b/src/win32/installer/installer_64bit.wxs
@@ -296,27 +296,17 @@
             <ServiceControl Id="StopGoogleIMEJaCacheService" Name="GoogleIMEJaCacheService" Stop="both" Remove="uninstall" Wait="yes" />
           </Component>
           <Component Id="GIMEJaTIP32" Permanent="no" Bitness="always32">
-            <File Id="GoogleIMEJaTIP32.dll" Name="GoogleIMEJaTIP32.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP32Path)" Vital="yes">
-              <Class Context="InprocServer32" ThreadingModel="apartment" Description="Google Japanese Input" Id="D5A86FD5-5308-47EA-AD16-9C4EB160EC3C" />
-            </File>
+            <File Id="GoogleIMEJaTIP32.dll" Name="GoogleIMEJaTIP32.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP32Path)" Vital="yes" />
           </Component>
           <Component Id="GIMEJaTIP64" Permanent="no" Bitness="always64">
-            <File Id="GoogleIMEJaTIP64.dll" Name="GoogleIMEJaTIP64.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64Path)" Vital="yes">
-              <?if $(var.MozcTIP64ArmPath) == "" and $(var.MozcTIP64XPath) == "" and $(var.MozcUniversalInstaller) == "" ?>
-                <Class Context="InprocServer32" ThreadingModel="apartment" Description="Google Japanese Input" Id="D5A86FD5-5308-47EA-AD16-9C4EB160EC3C" />
-              <?endif?>
-            </File>
+            <File Id="GoogleIMEJaTIP64.dll" Name="GoogleIMEJaTIP64.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64Path)" Vital="yes" />
           </Component>
           <?if $(var.MozcTIP64ArmPath) != "" and $(var.MozcTIP64XPath) != "" ?>
             <Component Id="GIMEJaTIP64Arm" Permanent="no" Bitness="always64">
               <File Id="GoogleIMEJaTIP64Arm.dll" Name="GoogleIMEJaTIP64Arm.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64ArmPath)" Vital="yes" />
             </Component>
             <Component Id="GIMEJaTIP64X" Permanent="no" Bitness="always64">
-              <File Id="GoogleIMEJaTIP64X.dll" Name="GoogleIMEJaTIP64X.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64XPath)" Vital="yes">
-                <?if $(var.MozcUniversalInstaller) == "" ?>
-                  <Class Context="InprocServer32" ThreadingModel="apartment" Description="Google Japanese Input" Id="D5A86FD5-5308-47EA-AD16-9C4EB160EC3C" />
-                <?endif?>
-              </File>
+              <File Id="GoogleIMEJaTIP64X.dll" Name="GoogleIMEJaTIP64X.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64XPath)" Vital="yes" />
             </Component>
           <?endif?>
           <Component Id="GIMEJaBroker" Permanent="no">

diff --git a/src/win32/installer/installer_oss_64bit.wxs b/src/win32/installer/installer_oss_64bit.wxs
@@ -271,27 +271,17 @@
           <ServiceControl Id="StopMozcCacheService" Name="MozcCacheService" Stop="both" Remove="uninstall" Wait="yes" />
         </Component>
         <Component Id="MozcTIP32" Permanent="no" Bitness="always32">
-          <File Id="mozc_tip32.dll" Name="mozc_tip32.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP32Path)" Vital="yes">
-            <Class Context="InprocServer32" ThreadingModel="apartment" Description="Mozc" Id="10A67BC8-22FA-4A59-90DC-2546652C56BF" />
-          </File>
+          <File Id="mozc_tip32.dll" Name="mozc_tip32.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP32Path)" Vital="yes" />
         </Component>
         <Component Id="MozcTIP64" Permanent="no" Bitness="always64">
-          <File Id="mozc_tip64.dll" Name="mozc_tip64.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64Path)" Vital="yes">
-            <?if $(var.MozcTIP64ArmPath) == "" and $(var.MozcTIP64XPath) == "" and $(var.MozcUniversalInstaller) == "" ?>
-              <Class Context="InprocServer32" ThreadingModel="apartment" Description="Mozc" Id="10A67BC8-22FA-4A59-90DC-2546652C56BF" />
-            <?endif?>
-          </File>
+          <File Id="mozc_tip64.dll" Name="mozc_tip64.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64Path)" Vital="yes" />
         </Component>
         <?if $(var.MozcTIP64ArmPath) != "" and $(var.MozcTIP64XPath) != "" ?>
           <Component Id="MozcTIP64Arm" Permanent="no" Bitness="always64">
             <File Id="mozc_tip64arm.dll" Name="mozc_tip64arm.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64ArmPath)" Vital="yes" />
           </Component>
           <Component Id="MozcTIP64X" Permanent="no" Bitness="always64">
-            <File Id="mozc_tip64x.dll" Name="mozc_tip64x.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64XPath)" Vital="yes">
-              <?if $(var.MozcUniversalInstaller) == "" ?>
-                <Class Context="InprocServer32" ThreadingModel="apartment" Description="Mozc" Id="10A67BC8-22FA-4A59-90DC-2546652C56BF" />
-              <?endif?>
-            </File>
+            <File Id="mozc_tip64x.dll" Name="mozc_tip64x.dll" DiskId="1" Checksum="yes" Source="$(var.MozcTIP64XPath)" Vital="yes" />
           </Component>
         <?endif?>
         <Component Id="MozcBroker" Permanent="no">