feat: improve Windows Toast actions support (#49786)

* feat: improve Windows Toast actions support

Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

* fix: ensure MSIX compatibility

Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

* test: add bad clsid format test

Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

---------

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

shell/browser/api/electron_api_app.cc

@@ -88,6 +88,7 @@
 
 #if BUILDFLAG(IS_WIN)
 #include "base/strings/utf_string_conversions.h"
+#include "shell/browser/notifications/win/windows_toast_activator.h"
 #include "shell/browser/ui/win/jump_list.h"
 #endif
 
@@ -1840,6 +1841,10 @@ gin::ObjectTemplateBuilder App::GetObjectTemplateBuilder(v8::Isolate* isolate) {
 #if BUILDFLAG(IS_WIN)
       .SetMethod("setAppUserModelId",
                  base::BindRepeating(&Browser::SetAppUserModelID, browser))
+      .SetMethod("setToastActivatorCLSID",
+                 base::BindRepeating(&App::SetToastActivatorCLSID,
+                                     base::Unretained(this)))
+      .SetProperty("toastActivatorCLSID", &App::GetToastActivatorCLSID)
 #endif
       .SetMethod(
           "isDefaultProtocolClient",
@@ -1967,6 +1972,34 @@ gin::ObjectTemplateBuilder App::GetObjectTemplateBuilder(v8::Isolate* isolate) {
       .SetMethod("resolveProxy", &App::ResolveProxy);
 }
 
+#if BUILDFLAG(IS_WIN)
+void App::SetToastActivatorCLSID(gin_helper::ErrorThrower thrower,
+                                 const std::string& id) {
+  std::wstring wide = base::UTF8ToWide(id);
+  CLSID parsed;
+  if (FAILED(::CLSIDFromString(wide.c_str(), &parsed))) {
+    if (!wide.empty() && wide.front() != L'{') {
+      std::wstring with_braces = L"{" + wide + L"}";
+      if (FAILED(::CLSIDFromString(with_braces.c_str(), &parsed))) {
+        thrower.ThrowError("Invalid CLSID format");
+        return;
+      }
+      wide = std::move(with_braces);
+    } else {
+      thrower.ThrowError("Invalid CLSID format");
+      return;
+    }
+  }
+
+  SetAppToastActivatorCLSID(wide);
+}
+
+v8::Local<v8::Value> App::GetToastActivatorCLSID(v8::Isolate* isolate) {
+  return gin::ConvertToV8(isolate,
+                          base::WideToUTF8(GetAppToastActivatorCLSID()));
+}
+#endif
+
 const char* App::GetHumanReadableName() const {
   return "Electron / App";
 }

shell/browser/api/electron_api_app.h

@@ -265,6 +265,12 @@ class App final : public gin::Wrappable<App>,
 
   // Set or remove a custom Jump List for the application.
   JumpListResult SetJumpList(v8::Isolate* isolate, v8::Local<v8::Value> val);
+
+  // Set the toast activator CLSID.
+  void SetToastActivatorCLSID(gin_helper::ErrorThrower thrower,
+                              const std::string& id);
+  // Get the toast activator CLSID.
+  v8::Local<v8::Value> GetToastActivatorCLSID(v8::Isolate* isolate);
 #endif  // BUILDFLAG(IS_WIN)
 
   std::unique_ptr<ProcessSingleton> process_singleton_;

shell/browser/api/electron_api_notification.cc

@@ -31,6 +31,9 @@ struct Converter<electron::NotificationAction> {
       return false;
     }
     dict.Get("text", &(out->text));
+    std::vector<std::u16string> items;
+    if (dict.Get("items", &items))
+      out->items = std::move(items);
     return true;
   }
 
@@ -39,6 +42,9 @@ struct Converter<electron::NotificationAction> {
     auto dict = gin::Dictionary::CreateEmpty(isolate);
     dict.Set("text", val.text);
     dict.Set("type", val.type);
+    if (!val.items.empty()) {
+      dict.Set("items", val.items);
+    }
     return ConvertToV8(isolate, dict);
   }
 };
@@ -138,8 +144,20 @@ void Notification::SetToastXml(const std::u16string& new_toast_xml) {
   toast_xml_ = new_toast_xml;
 }
 
-void Notification::NotificationAction(int index) {
-  Emit("action", index);
+void Notification::NotificationAction(int action_index, int selection_index) {
+  v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();
+  v8::HandleScope handle_scope(isolate);
+
+  gin_helper::internal::Event* event =
+      gin_helper::internal::Event::New(isolate);
+  v8::Local<v8::Object> event_object =
+      event->GetWrapper(isolate).ToLocalChecked();
+
+  gin_helper::Dictionary dict(isolate, event_object);
+  dict.Set("selectionIndex", selection_index);
+  dict.Set("actionIndex", action_index);
+
+  EmitWithoutEvent("action", event_object, action_index, selection_index);
 }
 
 void Notification::NotificationClick() {
@@ -147,7 +165,18 @@ void Notification::NotificationClick() {
 }
 
 void Notification::NotificationReplied(const std::string& reply) {
-  Emit("reply", reply);
+  v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();
+  v8::HandleScope handle_scope(isolate);
+
+  gin_helper::internal::Event* event =
+      gin_helper::internal::Event::New(isolate);
+  v8::Local<v8::Object> event_object =
+      event->GetWrapper(isolate).ToLocalChecked();
+
+  gin_helper::Dictionary dict(isolate, event_object);
+  dict.Set("reply", reply);
+
+  EmitWithoutEvent("reply", event_object, reply);
 }
 
 void Notification::NotificationDisplayed() {

shell/browser/api/electron_api_notification.h

@@ -45,7 +45,7 @@ class Notification final : public gin_helper::DeprecatedWrappable<Notification>,
   static const char* GetClassName() { return "Notification"; }
 
   // NotificationDelegate:
-  void NotificationAction(int index) override;
+  void NotificationAction(int action_index, int selection_index) override;
   void NotificationClick() override;
   void NotificationReplied(const std::string& reply) override;
   void NotificationDisplayed() override;

shell/browser/notifications/mac/cocoa_notification.mm

@@ -139,7 +139,7 @@ void CocoaNotification::NotificationReplied(const std::string& reply) {
 
 void CocoaNotification::NotificationActivated() {
   if (delegate())
-    delegate()->NotificationAction(action_index_);
+    delegate()->NotificationAction(action_index_, -1);
 
   this->LogAction("button clicked");
 }
@@ -156,7 +156,7 @@ void CocoaNotification::NotificationActivated(
       }
     }
 
-    delegate()->NotificationAction(index);
+    delegate()->NotificationAction(index, -1);
   }
 
   this->LogAction("button clicked");

shell/browser/notifications/notification.cc

@@ -22,6 +22,15 @@ NotificationOptions& NotificationOptions::operator=(NotificationOptions&&) =
     default;
 NotificationOptions::~NotificationOptions() = default;
 
+NotificationAction::NotificationAction() = default;
+NotificationAction::~NotificationAction() = default;
+NotificationAction::NotificationAction(const NotificationAction&) = default;
+NotificationAction& NotificationAction::operator=(const NotificationAction&) =
+    default;
+NotificationAction::NotificationAction(NotificationAction&&) noexcept = default;
+NotificationAction& NotificationAction::operator=(
+    NotificationAction&&) noexcept = default;
+
 Notification::Notification(NotificationDelegate* delegate,
                            NotificationPresenter* presenter)
     : delegate_(delegate), presenter_(presenter) {}

shell/browser/notifications/notification.h

@@ -23,6 +23,14 @@ class NotificationPresenter;
 struct NotificationAction {
   std::u16string type;
   std::u16string text;
+  std::vector<std::u16string> items;
+
+  NotificationAction();
+  ~NotificationAction();
+  NotificationAction(const NotificationAction&);
+  NotificationAction& operator=(const NotificationAction&);
+  NotificationAction(NotificationAction&&) noexcept;
+  NotificationAction& operator=(NotificationAction&&) noexcept;
 };
 
 struct NotificationOptions {

shell/browser/notifications/notification_delegate.h

@@ -19,7 +19,9 @@ class NotificationDelegate {
 
   // Notification was replied to
   virtual void NotificationReplied(const std::string& reply) {}
-  virtual void NotificationAction(int index) {}
+  // |selection_index| is >= 0 only for selection actions (Windows), otherwise
+  // -1.
+  virtual void NotificationAction(int action_index, int selection_index = -1) {}
 
   virtual void NotificationClick() {}
   virtual void NotificationClosed() {}

shell/browser/notifications/win/notification_presenter_win.cc

@@ -16,6 +16,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
+#include "shell/browser/notifications/win/windows_toast_activator.h"
 #include "shell/browser/notifications/win/windows_toast_notification.h"
 #include "shell/common/thread_restrictions.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ -45,6 +46,9 @@ std::unique_ptr<NotificationPresenter> NotificationPresenter::Create() {
   if (!presenter->Init())
     return {};
 
+  // Ensure COM toast activator is registered once the presenter is ready.
+  NotificationActivator::RegisterActivator();
+
   if (electron::debug_notifications)
     LOG(INFO) << "Successfully created Windows notifications presenter";
 

shell/browser/notifications/win/windows_toast_activator.cc

@@ -0,0 +1,429 @@
+// Copyright (c) 2025 Microsoft, GmbH
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "shell/browser/notifications/win/windows_toast_activator.h"
+
+#include <propkey.h>
+#include <propvarutil.h>
+#include <shlobj.h>
+#include <shobjidl.h>
+#include <wrl/module.h>
+#ifdef StrCat
+// Undefine Windows shlwapi.h StrCat macro to avoid conflict with
+// base/strings/strcat.h which deliberately defines a StrCat macro sentinel.
+#undef StrCat
+#endif
+
+#include <string>
+#include <vector>
+
+#include <algorithm>
+#include <atomic>
+
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/hash/hash.h"
+#include "base/logging.h"
+#include "base/no_destructor.h"
+#include "base/strings/string_number_conversions_win.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/win/registry.h"
+#include "base/win/scoped_propvariant.h"
+#include "base/win/win_util.h"
+#include "content/public/browser/browser_task_traits.h"
+#include "content/public/browser/browser_thread.h"
+#include "shell/browser/api/electron_api_notification.h"  // nogncheck - for delegate events
+#include "shell/browser/electron_browser_client.h"
+#include "shell/browser/notifications/notification.h"
+#include "shell/browser/notifications/notification_delegate.h"
+#include "shell/browser/notifications/notification_presenter.h"
+#include "shell/browser/notifications/win/notification_presenter_win.h"
+#include "shell/common/application_info.h"
+
+namespace electron {
+
+namespace {
+
+class NotificationActivatorFactory final : public IClassFactory {
+ public:
+  NotificationActivatorFactory() : ref_count_(1) {}
+  ~NotificationActivatorFactory() = default;
+  IFACEMETHODIMP QueryInterface(REFIID riid, void** ppv) override {
+    if (!ppv)
+      return E_POINTER;
+    if (riid == IID_IUnknown || riid == IID_IClassFactory) {
+      *ppv = static_cast<IClassFactory*>(this);
+    } else {
+      *ppv = nullptr;
+      return E_NOINTERFACE;
+    }
+    AddRef();
+    return S_OK;
+  }
+  IFACEMETHODIMP_(ULONG) AddRef() override { return ++ref_count_; }
+  IFACEMETHODIMP_(ULONG) Release() override {
+    ULONG res = --ref_count_;
+    if (res == 0)
+      delete this;
+    return res;
+  }
+
+  IFACEMETHODIMP CreateInstance(IUnknown* outer,
+                                REFIID riid,
+                                void** ppv) override {
+    if (outer)
+      return CLASS_E_NOAGGREGATION;
+    auto activator = Microsoft::WRL::Make<NotificationActivator>();
+    return activator.CopyTo(riid, ppv);
+  }
+  IFACEMETHODIMP LockServer(BOOL) override { return S_OK; }
+
+ private:
+  std::atomic<ULONG> ref_count_;
+};
+
+NotificationActivatorFactory* g_factory_instance = nullptr;
+bool g_registration_in_progress = false;
+
+std::wstring GetExecutablePath() {
+  wchar_t path[MAX_PATH];
+  DWORD len = ::GetModuleFileNameW(nullptr, path, std::size(path));
+  if (len == 0 || len == std::size(path))
+    return L"";
+  return std::wstring(path, len);
+}
+
+void EnsureCLSIDRegistry() {
+  std::wstring exe = GetExecutablePath();
+  if (exe.empty())
+    return;
+  std::wstring clsid = GetAppToastActivatorCLSID();
+  std::wstring key_path = L"Software\\Classes\\CLSID\\" + clsid;
+  base::win::RegKey key(HKEY_CURRENT_USER, key_path.c_str(), KEY_SET_VALUE);
+  if (!key.Valid())
+    return;
+  key.WriteValue(nullptr, L"Electron Notification Activator");
+  key.WriteValue(L"CustomActivator", 1U);
+
+  std::wstring local_server = key_path + L"\\LocalServer32";
+  base::win::RegKey server_key(HKEY_CURRENT_USER, local_server.c_str(),
+                               KEY_SET_VALUE);
+  if (!server_key.Valid())
+    return;
+  server_key.WriteValue(nullptr, exe.c_str());
+}
+
+bool ExistingShortcutValid(const base::FilePath& lnk_path, PCWSTR aumid) {
+  if (!base::PathExists(lnk_path))
+    return false;
+  Microsoft::WRL::ComPtr<IShellLink> existing;
+  if (FAILED(CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                              IID_PPV_ARGS(&existing))))
+    return false;
+  Microsoft::WRL::ComPtr<IPersistFile> pf;
+  if (FAILED(existing.As(&pf)) ||
+      FAILED(pf->Load(lnk_path.value().c_str(), STGM_READ))) {
+    return false;
+  }
+  Microsoft::WRL::ComPtr<IPropertyStore> store;
+  if (FAILED(existing.As(&store)))
+    return false;
+  base::win::ScopedPropVariant pv_id;
+  base::win::ScopedPropVariant pv_clsid;
+  if (FAILED(store->GetValue(PKEY_AppUserModel_ID, pv_id.Receive())) ||
+      FAILED(store->GetValue(PKEY_AppUserModel_ToastActivatorCLSID,
+                             pv_clsid.Receive()))) {
+    return false;
+  }
+  if (pv_id.get().vt == VT_LPWSTR && pv_clsid.get().vt == VT_CLSID &&
+      pv_id.get().pwszVal && pv_clsid.get().puuid) {
+    CLSID desired;
+    if (SUCCEEDED(::CLSIDFromString(GetAppToastActivatorCLSID(), &desired))) {
+      return _wcsicmp(pv_id.get().pwszVal, aumid) == 0 &&
+             IsEqualGUID(*pv_clsid.get().puuid, desired);
+    }
+  }
+  return false;
+}
+
+void EnsureShortcut() {
+  PCWSTR aumid = GetRawAppUserModelID();
+  if (!aumid || !*aumid)
+    return;
+
+  std::wstring exe = GetExecutablePath();
+  if (exe.empty())
+    return;
+
+  PWSTR programs_path = nullptr;
+  if (FAILED(
+          SHGetKnownFolderPath(FOLDERID_Programs, 0, nullptr, &programs_path)))
+    return;
+  base::FilePath programs(programs_path);
+  CoTaskMemFree(programs_path);
+
+  std::wstring product_name = base::UTF8ToWide(GetApplicationName());
+  if (product_name.empty())
+    product_name = L"ElectronApp";
+  base::CreateDirectory(programs);
+  base::FilePath lnk_path = programs.Append(product_name + L".lnk");
+  if (base::PathExists(lnk_path)) {
+    Microsoft::WRL::ComPtr<IShellLink> existing;
+    if (SUCCEEDED(CoCreateInstance(CLSID_ShellLink, nullptr,
+                                   CLSCTX_INPROC_SERVER,
+                                   IID_PPV_ARGS(&existing)))) {
+      Microsoft::WRL::ComPtr<IPersistFile> pf;
+      if (SUCCEEDED(existing.As(&pf)) &&
+          SUCCEEDED(pf->Load(lnk_path.value().c_str(), STGM_READ))) {
+        Microsoft::WRL::ComPtr<IPropertyStore> store;
+        if (SUCCEEDED(existing.As(&store))) {
+          base::win::ScopedPropVariant pv_clsid;
+          if (SUCCEEDED(store->GetValue(PKEY_AppUserModel_ToastActivatorCLSID,
+                                        pv_clsid.Receive())) &&
+              pv_clsid.get().vt == VT_CLSID && pv_clsid.get().puuid) {
+            wchar_t buf[64] = {0};
+            if (StringFromGUID2(*pv_clsid.get().puuid, buf, std::size(buf)) >
+                0) {
+              SetAppToastActivatorCLSID(buf);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  if (ExistingShortcutValid(lnk_path, aumid))
+    return;
+
+  Microsoft::WRL::ComPtr<IShellLink> shell_link;
+  if (FAILED(CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                              IID_PPV_ARGS(&shell_link))))
+    return;
+  shell_link->SetPath(exe.c_str());
+  shell_link->SetArguments(L"");
+  shell_link->SetDescription(product_name.c_str());
+  shell_link->SetWorkingDirectory(
+      base::FilePath(exe).DirName().value().c_str());
+
+  Microsoft::WRL::ComPtr<IPropertyStore> prop_store;
+  if (SUCCEEDED(shell_link.As(&prop_store))) {
+    PROPVARIANT pv_id;
+    PropVariantInit(&pv_id);
+    if (SUCCEEDED(InitPropVariantFromString(aumid, &pv_id))) {
+      prop_store->SetValue(PKEY_AppUserModel_ID, pv_id);
+      PropVariantClear(&pv_id);
+    }
+    PROPVARIANT pv_clsid;
+    PropVariantInit(&pv_clsid);
+    GUID clsid;
+    if (SUCCEEDED(::CLSIDFromString(GetAppToastActivatorCLSID(), &clsid)) &&
+        SUCCEEDED(InitPropVariantFromCLSID(clsid, &pv_clsid))) {
+      prop_store->SetValue(PKEY_AppUserModel_ToastActivatorCLSID, pv_clsid);
+      PropVariantClear(&pv_clsid);
+    }
+    prop_store->Commit();
+  }
+
+  Microsoft::WRL::ComPtr<IPersistFile> persist_file;
+  if (SUCCEEDED(shell_link.As(&persist_file))) {
+    persist_file->Save(lnk_path.value().c_str(), TRUE);
+  }
+}
+
+}  // namespace
+
+DWORD NotificationActivator::g_cookie_ = 0;
+bool NotificationActivator::g_registered_ = false;
+
+NotificationActivator::NotificationActivator() = default;
+NotificationActivator::~NotificationActivator() = default;
+
+// static
+
+// static
+void NotificationActivator::RegisterActivator() {
+  if (g_registered_ || g_registration_in_progress)
+    return;
+  g_registration_in_progress = true;
+
+  // For packaged (MSIX) apps, COM server registration is handled via the app
+  // manifest (com:Extension and desktop:ToastNotificationActivation), so we
+  // skip the registry and shortcut creation. We still need to call
+  // CoRegisterClassObject to handle activations at runtime.
+  //
+  // For unpackaged apps, we need to create the Start Menu shortcut with
+  // AUMID/CLSID properties and register the COM server in the registry.
+  bool is_packaged = IsRunningInDesktopBridge();
+
+  // Perform all blocking filesystem / registry work off the UI thread.
+  base::ThreadPool::PostTask(
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::BEST_EFFORT},
+      base::BindOnce(
+          [](bool is_packaged) {
+            // Skip shortcut and registry setup for packaged apps - these are
+            // declared in the app manifest instead.
+            if (!is_packaged) {
+              EnsureShortcut();
+              EnsureCLSIDRegistry();
+            }
+            content::GetUIThreadTaskRunner({})->PostTask(
+                FROM_HERE, base::BindOnce([]() {
+                  g_registration_in_progress = false;
+                  if (g_registered_)
+                    return;
+                  CLSID clsid;
+                  if (FAILED(::CLSIDFromString(GetAppToastActivatorCLSID(),
+                                               &clsid))) {
+                    LOG(ERROR) << "Invalid toast activator CLSID";
+                    return;
+                  }
+                  if (!g_factory_instance)
+                    g_factory_instance =
+                        new (std::nothrow) NotificationActivatorFactory();
+                  if (!g_factory_instance)
+                    return;
+                  DWORD cookie = 0;
+                  HRESULT hr = ::CoRegisterClassObject(
+                      clsid, static_cast<IClassFactory*>(g_factory_instance),
+                      CLSCTX_LOCAL_SERVER,
+                      REGCLS_MULTIPLEUSE | REGCLS_SUSPENDED, &cookie);
+                  if (FAILED(hr))
+                    return;
+                  hr = ::CoResumeClassObjects();
+                  if (FAILED(hr)) {
+                    ::CoRevokeClassObject(cookie);
+                    return;
+                  }
+                  g_cookie_ = cookie;
+                  g_registered_ = true;
+                }));
+          },
+          is_packaged));
+}
+
+// static
+void NotificationActivator::UnregisterActivator() {
+  if (!g_registered_)
+    return;
+  ::CoRevokeClassObject(g_cookie_);
+  g_cookie_ = 0;
+  g_registered_ = false;
+  // Factory instance lifetime intentionally leaked after revoke to avoid
+  // race; could be deleted here if ensured no pending COM calls.
+}
+
+IFACEMETHODIMP NotificationActivator::Activate(
+    LPCWSTR app_user_model_id,
+    LPCWSTR invoked_args,
+    const NOTIFICATION_USER_INPUT_DATA* data,
+    ULONG data_count) {
+  std::wstring args = invoked_args ? invoked_args : L"";
+  std::wstring aumid = app_user_model_id ? app_user_model_id : L"";
+
+  std::vector<ActivationUserInput> copied_inputs;
+  if (data && data_count) {
+    std::vector<NOTIFICATION_USER_INPUT_DATA> temp;
+    temp.resize(static_cast<size_t>(data_count));
+    std::copy_n(data, static_cast<size_t>(data_count), temp.begin());
+    copied_inputs.reserve(temp.size());
+    for (const auto& entry : temp) {
+      ActivationUserInput ui;
+      if (entry.Key)
+        ui.key = entry.Key;
+      if (entry.Value)
+        ui.value = entry.Value;
+      copied_inputs.push_back(std::move(ui));
+    }
+  }
+
+  content::GetUIThreadTaskRunner({})->PostTask(
+      FROM_HERE, base::BindOnce(&HandleToastActivation, std::move(args),
+                                std::move(copied_inputs)));
+  return S_OK;
+}
+
+void HandleToastActivation(const std::wstring& invoked_args,
+                           std::vector<ActivationUserInput> inputs) {
+  // Expected invoked_args format:
+  // type=<click|action|reply>&action=<index>&tag=<hash> Parse simple key=value
+  // pairs separated by '&'.
+  std::wstring args = invoked_args;
+  std::wstring type;
+  std::wstring action_index_str;
+  std::wstring tag_str;
+
+  for (const auto& token : base::SplitString(args, L"&", base::KEEP_WHITESPACE,
+                                             base::SPLIT_WANT_NONEMPTY)) {
+    auto kv = base::SplitString(token, L"=", base::KEEP_WHITESPACE,
+                                base::SPLIT_WANT_NONEMPTY);
+    if (kv.size() != 2)
+      continue;
+    if (kv[0] == L"type")
+      type = kv[1];
+    else if (kv[0] == L"action")
+      action_index_str = kv[1];
+    else if (kv[0] == L"tag")
+      tag_str = kv[1];
+  }
+
+  int action_index = -1;
+  if (!action_index_str.empty()) {
+    action_index = std::stoi(action_index_str);
+  }
+
+  std::string reply_text;
+  for (const auto& entry : inputs) {
+    std::wstring_view key_view(entry.key);
+    if (key_view == L"reply") {
+      reply_text = base::WideToUTF8(entry.value);
+    }
+  }
+
+  auto* browser_client =
+      static_cast<ElectronBrowserClient*>(ElectronBrowserClient::Get());
+  if (!browser_client)
+    return;
+
+  NotificationPresenter* presenter = browser_client->GetNotificationPresenter();
+  if (!presenter)
+    return;
+
+  Notification* target = nullptr;
+  for (auto* n : presenter->notifications()) {
+    std::wstring tag_hash =
+        base::NumberToWString(base::FastHash(n->notification_id()));
+    if (tag_hash == tag_str) {
+      target = n;
+      break;
+    }
+  }
+
+  if (!target)
+    return;
+
+  if (type == L"action" && target->delegate()) {
+    int selection_index = -1;
+    for (const auto& entry : inputs) {
+      std::wstring_view key_view(entry.key);
+      if (base::StartsWith(key_view, L"selection",
+                           base::CompareCase::SENSITIVE)) {
+        int parsed = -1;
+        if (base::StringToInt(entry.value, &parsed) && parsed >= 0)
+          selection_index = parsed;
+        break;
+      }
+    }
+    if (action_index >= 0)
+      target->delegate()->NotificationAction(action_index, selection_index);
+  } else if ((type == L"reply" || (!reply_text.empty() && type.empty())) &&
+             target->delegate()) {
+    target->delegate()->NotificationReplied(reply_text);
+  } else if ((type == L"click" || type.empty()) && target->delegate()) {
+    target->NotificationClicked();
+  }
+}
+
+}  // namespace electron

shell/browser/notifications/win/windows_toast_activator.h

@@ -0,0 +1,49 @@
+// Copyright (c) 2025 Microsoft, GmbH
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ELECTRON_SHELL_BROWSER_NOTIFICATIONS_WIN_WINDOWS_TOAST_ACTIVATOR_H_
+#define ELECTRON_SHELL_BROWSER_NOTIFICATIONS_WIN_WINDOWS_TOAST_ACTIVATOR_H_
+
+#include <NotificationActivationCallback.h>
+#include <windows.h>
+#include <wrl/implements.h>
+#include <string>
+#include <vector>
+
+namespace electron {
+
+class NotificationPresenterWin;
+
+class NotificationActivator
+    : public Microsoft::WRL::RuntimeClass<
+          Microsoft::WRL::RuntimeClassFlags<Microsoft::WRL::ClassicCom>,
+          INotificationActivationCallback> {
+ public:
+  NotificationActivator();
+  ~NotificationActivator() override;
+
+  IFACEMETHODIMP Activate(LPCWSTR app_user_model_id,
+                          LPCWSTR invoked_args,
+                          const NOTIFICATION_USER_INPUT_DATA* data,
+                          ULONG data_count) override;
+
+  static void RegisterActivator();
+  static void UnregisterActivator();
+
+ private:
+  static DWORD g_cookie_;
+  static bool g_registered_;
+};
+
+struct ActivationUserInput {
+  std::wstring key;
+  std::wstring value;
+};
+
+void HandleToastActivation(const std::wstring& invoked_args,
+                           std::vector<ActivationUserInput> inputs);
+
+}  // namespace electron
+
+#endif  // ELECTRON_SHELL_BROWSER_NOTIFICATIONS_WIN_WINDOWS_TOAST_ACTIVATOR_H_

shell/browser/notifications/win/windows_toast_notification.cc

@@ -111,43 +111,41 @@ const std::string FailureResultToString(HRESULT failure_reason) {
   return hresult_str;
 }
 
+constexpr char kPlaceholderContent[] = "placeHolderContent";
+constexpr char kContent[] = "content";
 constexpr char kToast[] = "toast";
 constexpr char kVisual[] = "visual";
 constexpr char kBinding[] = "binding";
 constexpr char kTemplate[] = "template";
-constexpr char kToastText01[] = "ToastText01";
-constexpr char kToastText02[] = "ToastText02";
-constexpr char kToastImageAndText01[] = "ToastImageAndText01";
-constexpr char kToastImageAndText02[] = "ToastImageAndText02";
+constexpr char kToastTemplate[] = "ToastGeneric";
 constexpr char kText[] = "text";
 constexpr char kImage[] = "image";
 constexpr char kPlacement[] = "placement";
 constexpr char kAppLogoOverride[] = "appLogoOverride";
 constexpr char kHintCrop[] = "hint-crop";
+constexpr char kHintInputId[] = "hint-inputId";
 constexpr char kHintCropNone[] = "none";
 constexpr char kSrc[] = "src";
 constexpr char kAudio[] = "audio";
 constexpr char kSilent[] = "silent";
+constexpr char kReply[] = "reply";
 constexpr char kTrue[] = "true";
 constexpr char kID[] = "id";
+constexpr char kInput[] = "input";
+constexpr char kType[] = "type";
+constexpr char kSelection[] = "selection";
 constexpr char kScenario[] = "scenario";
 constexpr char kReminder[] = "reminder";
 constexpr char kActions[] = "actions";
 constexpr char kAction[] = "action";
 constexpr char kActivationType[] = "activationType";
-constexpr char kSystem[] = "system";
+constexpr char kActivationTypeForeground[] = "foreground";
+constexpr char kActivationTypeSystem[] = "system";
 constexpr char kArguments[] = "arguments";
 constexpr char kDismiss[] = "dismiss";
 // The XML version header that has to be stripped from the output.
 constexpr char kXmlVersionHeader[] = "<?xml version=\"1.0\"?>\n";
 
-const char* GetTemplateType(bool two_lines, bool has_icon) {
-  if (has_icon) {
-    return two_lines ? kToastImageAndText02 : kToastImageAndText01;
-  }
-  return two_lines ? kToastText02 : kToastText01;
-}
-
 }  // namespace
 
 // static
@@ -171,8 +169,9 @@ WindowsToastNotification::GetToastTaskRunner() {
 }
 
 bool WindowsToastNotification::Initialize() {
-  // Just initialize, don't care if it fails or already initialized.
-  Windows::Foundation::Initialize(RO_INIT_MULTITHREADED);
+  HRESULT hr = Windows::Foundation::Initialize(RO_INIT_SINGLETHREADED);
+  if (FAILED(hr))
+    Windows::Foundation::Initialize(RO_INIT_MULTITHREADED);
 
   ScopedHString toast_manager_str(
       RuntimeClass_Windows_UI_Notifications_ToastNotificationManager);
@@ -273,8 +272,8 @@ void WindowsToastNotification::CreateToastNotificationOnBackgroundThread(
   DebugLog("CreateToastXmlOnBackgroundThread called");
   ComPtr<IXmlDocument> toast_xml;
 
-  if (!CreateToastXmlDocument(options, presenter, weak_notification,
-                              ui_task_runner, &toast_xml)) {
+  if (!CreateToastXmlDocument(options, presenter, notification_id,
+                              weak_notification, ui_task_runner, &toast_xml)) {
     return;  // Error already posted to UI thread
   }
 
@@ -300,13 +299,14 @@ void WindowsToastNotification::CreateToastNotificationOnBackgroundThread(
 bool WindowsToastNotification::CreateToastXmlDocument(
     const NotificationOptions& options,
     NotificationPresenter* presenter,
+    const std::string& notification_id,
     base::WeakPtr<Notification> weak_notification,
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
     ComPtr<IXmlDocument>* toast_xml) {
   // The custom xml takes priority over the preset template.
   if (!options.toast_xml.empty()) {
-    DebugLog(base::StrCat({"Processing custom toast_xml, length: ",
-                           base::NumberToString(options.toast_xml.length())}));
+    DebugLog("Toast XML (custom) id=" + notification_id + ": " +
+             base::UTF16ToUTF8(options.toast_xml));
     HRESULT hr = XmlDocumentFromString(base::as_wcstr(options.toast_xml),
                                        toast_xml->GetAddressOf());
     DebugLog(base::StrCat({"XmlDocumentFromString returned HRESULT: ",
@@ -316,7 +316,6 @@ bool WindowsToastNotification::CreateToastXmlDocument(
           base::StrCat({"XML: Invalid XML, ERROR ", FailureResultToString(hr)});
       DebugLog(base::StrCat({"XML parsing failed, posting error: ", err}));
       PostNotificationFailedToUIThread(weak_notification, err, ui_task_runner);
-      DebugLog("PostNotificationFailedToUIThread called");
       return false;
     }
     DebugLog("XML parsing succeeded");
@@ -325,8 +324,13 @@ bool WindowsToastNotification::CreateToastXmlDocument(
     std::wstring icon_path =
         presenter_win->SaveIconToFilesystem(options.icon, options.icon_url);
     std::u16string toast_xml_str =
-        GetToastXml(options.title, options.msg, icon_path, options.timeout_type,
-                    options.silent);
+        GetToastXml(notification_id, options.title, options.msg, icon_path,
+                    options.timeout_type, options.silent, options.actions,
+                    options.has_reply, options.reply_placeholder);
+
+    DebugLog("Toast XML (generated) id=" + notification_id + ": " +
+             base::UTF16ToUTF8(toast_xml_str));
+
     HRESULT hr = XmlDocumentFromString(base::as_wcstr(toast_xml_str),
                                        toast_xml->GetAddressOf());
     if (FAILED(hr)) {
@@ -523,11 +527,15 @@ void WindowsToastNotification::Dismiss() {
 }
 
 std::u16string WindowsToastNotification::GetToastXml(
+    const std::string& notification_id,
     const std::u16string& title,
     const std::u16string& msg,
     const std::wstring& icon_path,
     const std::u16string& timeout_type,
-    bool silent) {
+    bool silent,
+    const std::vector<NotificationAction>& actions,
+    bool has_reply,
+    const std::u16string& reply_placeholder) {
   XmlWriter xml_writer;
   xml_writer.StartWriting();
 
@@ -543,36 +551,33 @@ std::u16string WindowsToastNotification::GetToastXml(
   xml_writer.StartElement(kVisual);
   // <binding template="<template>">
   xml_writer.StartElement(kBinding);
-  const bool two_lines = (!title.empty() && !msg.empty());
-  xml_writer.AddAttribute(kTemplate,
-                          GetTemplateType(two_lines, !icon_path.empty()));
+  xml_writer.AddAttribute(kTemplate, kToastTemplate);
 
-  // Add text nodes.
   std::u16string line1;
   std::u16string line2;
   if (title.empty() || msg.empty()) {
     line1 = title.empty() ? msg : title;
     if (line1.empty())
       line1 = u"[no message]";
+    // <text>
     xml_writer.StartElement(kText);
-    xml_writer.AddAttribute(kID, "1");
     xml_writer.AppendElementContent(base::UTF16ToUTF8(line1));
     xml_writer.EndElement();  // </text>
   } else {
     line1 = title;
     line2 = msg;
+    // <text>
     xml_writer.StartElement(kText);
-    xml_writer.AddAttribute(kID, "1");
     xml_writer.AppendElementContent(base::UTF16ToUTF8(line1));
-    xml_writer.EndElement();
+    xml_writer.EndElement();  // </text>
+    // <text>
     xml_writer.StartElement(kText);
-    xml_writer.AddAttribute(kID, "2");
     xml_writer.AppendElementContent(base::UTF16ToUTF8(line2));
-    xml_writer.EndElement();
+    xml_writer.EndElement();  // </text>
   }
 
-  // Optional icon as app logo override (small icon).
   if (!icon_path.empty()) {
+    // <image>
     xml_writer.StartElement(kImage);
     xml_writer.AddAttribute(kID, "1");
     xml_writer.AddAttribute(kPlacement, kAppLogoOverride);
@@ -584,15 +589,85 @@ std::u16string WindowsToastNotification::GetToastXml(
   xml_writer.EndElement();  // </binding>
   xml_writer.EndElement();  // </visual>
 
-  // <actions> (only to ensure reminder has a dismiss button).
-  if (is_reminder) {
+  if (is_reminder || has_reply || !actions.empty()) {
+    // <actions>
     xml_writer.StartElement(kActions);
-    xml_writer.StartElement(kAction);
-    xml_writer.AddAttribute(kActivationType, kSystem);
-    xml_writer.AddAttribute(kArguments, kDismiss);
-    xml_writer.AddAttribute(
-        "content", base::WideToUTF8(l10n_util::GetWideString(IDS_APP_CLOSE)));
-    xml_writer.EndElement();  // </action>
+    if (is_reminder) {
+      xml_writer.StartElement(kAction);
+      xml_writer.AddAttribute(kActivationType, kActivationTypeSystem);
+      xml_writer.AddAttribute(kArguments, kDismiss);
+      xml_writer.AddAttribute(
+          kContent, base::WideToUTF8(l10n_util::GetWideString(IDS_APP_CLOSE)));
+      xml_writer.EndElement();  // </action>
+    }
+
+    if (has_reply) {
+      // <input>
+      xml_writer.StartElement(kInput);
+      xml_writer.AddAttribute(kID, kReply);
+      xml_writer.AddAttribute(kType, kText);
+      if (!reply_placeholder.empty()) {
+        xml_writer.AddAttribute(kPlaceholderContent,
+                                base::UTF16ToUTF8(reply_placeholder));
+      }
+      xml_writer.EndElement();  // </input>
+    }
+
+    for (size_t i = 0; i < actions.size(); ++i) {
+      const auto& act = actions[i];
+      if (act.type == u"button" || act.type.empty()) {
+        // <action>
+        xml_writer.StartElement(kAction);
+        xml_writer.AddAttribute(kActivationType, kActivationTypeForeground);
+        std::string args = base::StrCat(
+            {"type=action&action=", base::NumberToString(i),
+             "&tag=", base::NumberToString(base::FastHash(notification_id))});
+        xml_writer.AddAttribute(kArguments, args.c_str());
+        xml_writer.AddAttribute(kContent, base::UTF16ToUTF8(act.text));
+        xml_writer.EndElement();  // <action>
+      } else if (act.type == u"selection") {
+        std::string input_id =
+            base::StrCat({kSelection, base::NumberToString(i)});
+        xml_writer.StartElement(kInput);  // <input>
+        xml_writer.AddAttribute(kID, input_id.c_str());
+        xml_writer.AddAttribute(kType, kSelection);
+        for (size_t opt_i = 0; opt_i < act.items.size(); ++opt_i) {
+          xml_writer.StartElement(kSelection);  // <selection>
+          xml_writer.AddAttribute(kID, base::NumberToString(opt_i).c_str());
+          xml_writer.AddAttribute(kContent,
+                                  base::UTF16ToUTF8(act.items[opt_i]));
+          xml_writer.EndElement();  // </selection>
+        }
+        xml_writer.EndElement();  // </input>
+
+        // The button that submits the selection.
+        xml_writer.StartElement(kAction);
+        xml_writer.AddAttribute(kActivationType, kActivationTypeForeground);
+        std::string args = base::StrCat(
+            {"type=action&action=", base::NumberToString(i),
+             "&tag=", base::NumberToString(base::FastHash(notification_id))});
+        xml_writer.AddAttribute(kArguments, args.c_str());
+        xml_writer.AddAttribute(
+            kContent,
+            base::UTF16ToUTF8(act.text.empty() ? u"Select" : act.text));
+        xml_writer.AddAttribute(kHintInputId, input_id.c_str());
+        xml_writer.EndElement();  // </action>
+      }
+    }
+
+    if (has_reply) {
+      // <action>
+      xml_writer.StartElement(kAction);
+      xml_writer.AddAttribute(kActivationType, kActivationTypeForeground);
+      std::string args =
+          base::StrCat({"type=reply&tag=",
+                        base::NumberToString(base::FastHash(notification_id))});
+      xml_writer.AddAttribute(kArguments, args.c_str());
+      // TODO(codebytere): we should localize this.
+      xml_writer.AddAttribute(kContent, "Reply");
+      xml_writer.AddAttribute(kHintInputId, kReply);
+      xml_writer.EndElement();  // <action>
+    }
     xml_writer.EndElement();  // </actions>
   }
 
@@ -663,6 +738,57 @@ ToastEventHandler::~ToastEventHandler() = default;
 IFACEMETHODIMP ToastEventHandler::Invoke(
     winui::Notifications::IToastNotification* sender,
     IInspectable* args) {
+  std::wstring arguments_w;
+  std::wstring tag_w;
+  std::wstring group_w;
+
+  if (args) {
+    Microsoft::WRL::ComPtr<winui::Notifications::IToastActivatedEventArgs>
+        activated_args;
+    if (SUCCEEDED(args->QueryInterface(IID_PPV_ARGS(&activated_args)))) {
+      HSTRING args_hs = nullptr;
+      if (SUCCEEDED(activated_args->get_Arguments(&args_hs)) && args_hs) {
+        UINT32 len = 0;
+        const wchar_t* raw = WindowsGetStringRawBuffer(args_hs, &len);
+        if (raw && len)
+          arguments_w.assign(raw, len);
+      }
+    }
+  }
+
+  if (sender) {
+    Microsoft::WRL::ComPtr<winui::Notifications::IToastNotification2> toast2;
+    if (SUCCEEDED(sender->QueryInterface(IID_PPV_ARGS(&toast2)))) {
+      HSTRING tag_hs = nullptr;
+      if (SUCCEEDED(toast2->get_Tag(&tag_hs)) && tag_hs) {
+        UINT32 len = 0;
+        const wchar_t* raw = WindowsGetStringRawBuffer(tag_hs, &len);
+        if (raw && len)
+          tag_w.assign(raw, len);
+      }
+      HSTRING group_hs = nullptr;
+      if (SUCCEEDED(toast2->get_Group(&group_hs)) && group_hs) {
+        UINT32 len = 0;
+        const wchar_t* raw = WindowsGetStringRawBuffer(group_hs, &len);
+        if (raw && len)
+          group_w.assign(raw, len);
+      }
+    }
+  }
+
+  std::string notif_id;
+  std::string notif_hash;
+  if (notification_) {
+    notif_id = notification_->notification_id();
+    notif_hash = base::NumberToString(base::FastHash(notif_id));
+  }
+
+  bool structured = arguments_w.find(L"&tag=") != std::wstring::npos ||
+                    arguments_w.find(L"type=action") != std::wstring::npos ||
+                    arguments_w.find(L"type=reply") != std::wstring::npos;
+  if (structured)
+    return S_OK;
+
   content::GetUIThreadTaskRunner({})->PostTask(
       FROM_HERE,
       base::BindOnce(&Notification::NotificationClicked, notification_));

shell/browser/notifications/win/windows_toast_notification.h

@@ -60,11 +60,16 @@ class WindowsToastNotification : public Notification {
   friend class ToastEventHandler;
 
   HRESULT ShowInternal(const NotificationOptions& options);
-  static std::u16string GetToastXml(const std::u16string& title,
-                                    const std::u16string& msg,
-                                    const std::wstring& icon_path,
-                                    const std::u16string& timeout_type,
-                                    const bool silent);
+  static std::u16string GetToastXml(
+      const std::string& notification_id,
+      const std::u16string& title,
+      const std::u16string& msg,
+      const std::wstring& icon_path,
+      const std::u16string& timeout_type,
+      const bool silent,
+      const std::vector<NotificationAction>& actions,
+      bool has_reply,
+      const std::u16string& reply_placeholder);
   static HRESULT XmlDocumentFromString(
       const wchar_t* xmlString,
       ABI::Windows::Data::Xml::Dom::IXmlDocument** doc);
@@ -77,6 +82,7 @@ class WindowsToastNotification : public Notification {
   static bool CreateToastXmlDocument(
       const NotificationOptions& options,
       NotificationPresenter* presenter,
+      const std::string& notification_id,
       base::WeakPtr<Notification> weak_notification,
       scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
       ComPtr<ABI::Windows::Data::Xml::Dom::IXmlDocument>* toast_xml);

shell/common/application_info.h

@@ -32,6 +32,8 @@ PCWSTR GetRawAppUserModelID();
 bool GetAppUserModelID(ScopedHString* app_id);
 void SetAppUserModelID(const std::wstring& name);
 bool IsRunningInDesktopBridge();
+PCWSTR GetAppToastActivatorCLSID();
+void SetAppToastActivatorCLSID(const std::wstring& clsid);
 #endif
 
 }  // namespace electron

shell/common/application_info_win.cc

@@ -28,6 +28,11 @@ std::wstring& GetAppUserModelId() {
   return *g_app_user_model_id;
 }
 
+std::wstring& GetToastActivatorCLSID() {
+  static base::NoDestructor<std::wstring> g_toast_activator_clsid;
+  return *g_toast_activator_clsid;
+}
+
 std::string GetApplicationName() {
   auto* module = GetModuleHandle(nullptr);
   std::unique_ptr<FileVersionInfo> info(
@@ -82,4 +87,37 @@ bool IsRunningInDesktopBridge() {
   return result;
 }
 
+PCWSTR GetAppToastActivatorCLSID() {
+  if (GetToastActivatorCLSID().empty()) {
+    GUID guid;
+    if (SUCCEEDED(::CoCreateGuid(&guid))) {
+      wchar_t buf[64] = {0};
+      if (StringFromGUID2(guid, buf, std::size(buf)) > 0)
+        GetToastActivatorCLSID() = buf;
+    }
+  }
+
+  return GetToastActivatorCLSID().c_str();
+}
+
+void SetAppToastActivatorCLSID(const std::wstring& clsid) {
+  CLSID parsed;
+  if (SUCCEEDED(::CLSIDFromString(clsid.c_str(), &parsed))) {
+    // Normalize formatting.
+    wchar_t buf[64] = {0};
+    if (StringFromGUID2(parsed, buf, std::size(buf)) > 0)
+      GetToastActivatorCLSID() = buf;
+  } else {
+    // Try adding braces if user omitted them.
+    if (!clsid.empty() && clsid.front() != L'{') {
+      std::wstring with_braces = L"{" + clsid + L"}";
+      if (SUCCEEDED(::CLSIDFromString(with_braces.c_str(), &parsed))) {
+        wchar_t buf[64] = {0};
+        if (StringFromGUID2(parsed, buf, std::size(buf)) > 0)
+          GetToastActivatorCLSID() = buf;
+      }
+    }
+  }
+}
+
 }  // namespace electron