diff --git a/.github/workflows/actions.yml b/.github/workflows/actions.yml
index 1bf492d20..67e5c3843 100644
--- a/.github/workflows/actions.yml
+++ b/.github/workflows/actions.yml
@@ -461,7 +461,7 @@ jobs:
         run: apk add --upgrade glibmm-dev gtkmm3-dev
       - name: Get Dependencies (Qt6)
         if: ${{ needs.what-to-make.outputs.make-qt == 'true' }}
-        run: apk add --upgrade qt6-qttools-dev qt6-qtsvg-dev
+        run: apk add --upgrade qt6-qtbase-dev qt6-qttools-dev qt6-qtsvg-dev xcb-util-cursor
       - name: Get Source
         uses: actions/checkout@v4
         with:
@@ -494,6 +494,7 @@ jobs:
         if: ${{ needs.what-to-make.outputs.make-tests == 'true' }}
         env:
           TMPDIR: /private/tmp
+          QT_QPA_PLATFORM: offscreen
         run: cmake -E chdir obj ctest -j $(nproc) --build-config RelWithDebInfo --output-on-failure
       - name: Install
         run: cmake --build obj --config RelWithDebInfo --target install/strip
@@ -765,6 +766,8 @@ jobs:
         run: cmake --build obj --config RelWithDebInfo
       - name: Test
         if: ${{ needs.what-to-make.outputs.make-tests == 'true' }}
+        env:
+          QT_QPA_PLATFORM: offscreen
         run: cmake -E chdir obj ctest -j $(nproc) --build-config RelWithDebInfo --output-on-failure
       - name: Install
         run: cmake --build obj --config RelWithDebInfo --target install/strip
@@ -814,7 +817,7 @@ jobs:
         run: dnf install -y glibmm2.68-devel gtkmm4.0-devel
       - name: Get Dependencies (Qt6)
         if: ${{ needs.what-to-make.outputs.make-qt == 'true' }}
-        run: dnf install -y qt6-qtbase-devel qt6-qtsvg-devel qt6-qttools-devel
+        run: dnf install -y qt6-qtbase-devel qt6-qtsvg-devel qt6-qttools-devel xcb-util-cursor
       - name: Get Source
         uses: actions/download-artifact@v4
         with:
@@ -845,6 +848,8 @@ jobs:
         run: cmake --build obj --config RelWithDebInfo
       - name: Test
         if: ${{ needs.what-to-make.outputs.make-tests == 'true' }}
+        env:
+          QT_QPA_PLATFORM: offscreen
         run: cmake -E chdir obj ctest -j $(nproc) --build-config RelWithDebInfo --output-on-failure
       - name: Install
         run: cmake --build obj --config RelWithDebInfo --target install/strip
@@ -1014,7 +1019,7 @@ jobs:
         run: sudo apt-get install -y --no-install-recommends libglibmm-2.4-dev libgtkmm-3.0-dev
       - name: Get Dependencies (Qt6)
         if: ${{ needs.what-to-make.outputs.make-qt == 'true' }}
-        run: sudo apt-get install -y --no-install-recommends qt6-svg-dev qt6-tools-dev
+        run: sudo apt-get install -y --no-install-recommends qt6-base-dev qt6-svg-dev qt6-tools-dev
       - name: Get Source
         uses: actions/checkout@v4
         with:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94e370def..1143d71b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -409,6 +409,9 @@ if(ENABLE_QT)
         Network
         Svg
         LinguistTools)
+    if(ENABLE_TESTS)
+        list(APPEND QT_REQUIRED_MODULES Test)
+    endif()
     set(QT_OPTIONAL_MODULES
         DBus
         AxContainer
@@ -429,7 +432,7 @@ if(ENABLE_QT)
         foreach(M ${QT_REQUIRED_MODULES})
             find_package(Qt${Qt_VERSION_MAJOR}${M} ${QT_MINIMUM} QUIET)
             if(Qt${Qt_VERSION_MAJOR}${M}_FOUND)
-                if(NOT M STREQUAL "LinguistTools")
+                if(NOT M STREQUAL "LinguistTools" AND NOT M STREQUAL "Test")
                     list(APPEND QT_TARGETS Qt${Qt_VERSION_MAJOR}::${M})
                 endif()
             else()
@@ -811,11 +814,6 @@ if(RUN_CLANG_TIDY)
     endif()
 endif()
 
-if(ENABLE_TESTS)
-    enable_testing()
-    add_subdirectory(tests)
-endif()
-
 function(tr_install_web DST_DIR)
     if(INSTALL_WEB)
         install(
@@ -844,6 +842,11 @@ foreach(P cli daemon gtk mac qt utils)
     endif()
 endforeach()
 
+if(ENABLE_TESTS)
+    enable_testing()
+    add_subdirectory(tests)
+endif()
+
 if(ENABLE_DAEMON OR ENABLE_GTK OR ENABLE_QT)
     tr_install_web(${CMAKE_INSTALL_DATAROOTDIR}/${TR_NAME})
 endif()
diff --git a/qt/Application.cc b/qt/Application.cc
index 939542970..d60e8dffa 100644
--- a/qt/Application.cc
+++ b/qt/Application.cc
@@ -128,14 +128,14 @@ QAccessibleInterface* accessibleFactory(QString const& className, QObject* objec
 } // namespace
 
 Application::Application(
-    std::unique_ptr<Prefs> prefs,
+    Prefs& prefs,
     bool minimized,
     QString const& config_dir,
     QStringList const& filenames,
     int& argc,
     char** argv)
     : QApplication{ argc, argv }
-    , prefs_(std::move(prefs))
+    , prefs_{ prefs }
 {
     setApplicationName(ConfigName);
     loadTranslations();
@@ -162,9 +162,9 @@ Application::Application(
     QAccessible::installFactory(&accessibleFactory);
 #endif
 
-    session_ = std::make_unique<Session>(config_dir, *prefs_);
-    model_ = std::make_unique<TorrentModel>(*prefs_);
-    window_ = std::make_unique<MainWindow>(*session_, *prefs_, *model_, minimized);
+    session_ = std::make_unique<Session>(config_dir, prefs_);
+    model_ = std::make_unique<TorrentModel>(prefs_);
+    window_ = std::make_unique<MainWindow>(*session_, prefs_, *model_, minimized);
     watch_dir_ = std::make_unique<WatchDir>(*model_);
 
     connect(this, &QCoreApplication::aboutToQuit, this, &Application::saveGeometry);
@@ -172,7 +172,7 @@ Application::Application(
     connect(model_.get(), &TorrentModel::torrentsCompleted, this, &Application::onTorrentsCompleted);
     connect(model_.get(), &TorrentModel::torrentsEdited, this, &Application::onTorrentsEdited);
     connect(model_.get(), &TorrentModel::torrentsNeedInfo, this, &Application::onTorrentsNeedInfo);
-    connect(prefs_.get(), &Prefs::changed, this, &Application::refreshPref);
+    connect(&prefs_, &Prefs::changed, this, &Application::refreshPref);
     connect(session_.get(), &Session::sourceChanged, this, &Application::onSessionSourceChanged);
     connect(session_.get(), &Session::torrentsRemoved, model_.get(), &TorrentModel::removeTorrents);
     connect(session_.get(), &Session::torrentsUpdated, model_.get(), &TorrentModel::updateTorrents);
@@ -295,7 +295,7 @@ QStringList Application::getNames(torrent_ids_t const& torrent_ids) const
 
 void Application::onTorrentsAdded(torrent_ids_t const& torrent_ids) const
 {
-    if (!prefs_->get<bool>(Prefs::SHOW_NOTIFICATION_ON_ADD))
+    if (!prefs_.get<bool>(Prefs::SHOW_NOTIFICATION_ON_ADD))
     {
         return;
     }
@@ -308,19 +308,19 @@ void Application::onTorrentsAdded(torrent_ids_t const& torrent_ids) const
 
 void Application::onTorrentsCompleted(torrent_ids_t const& torrent_ids) const
 {
-    if (prefs_->get<bool>(Prefs::SHOW_NOTIFICATION_ON_COMPLETE))
+    if (prefs_.get<bool>(Prefs::SHOW_NOTIFICATION_ON_COMPLETE))
     {
         auto const title = tr("Torrent(s) Completed", nullptr, static_cast<int>(std::size(torrent_ids)));
         auto const body = getNames(torrent_ids).join(QStringLiteral("\n"));
         notifyApp(title, body);
     }
 
-    if (prefs_->get<bool>(Prefs::COMPLETE_SOUND_ENABLED))
+    if (prefs_.get<bool>(Prefs::COMPLETE_SOUND_ENABLED))
     {
 #if defined(Q_OS_WIN) || defined(Q_OS_MAC)
         beep();
 #else
-        auto args = prefs_->get<QStringList>(Prefs::COMPLETE_SOUND_COMMAND);
+        auto args = prefs_.get<QStringList>(Prefs::COMPLETE_SOUND_COMMAND);
         auto const command = args.takeFirst();
         QProcess::execute(command, args);
 #endif
@@ -346,13 +346,13 @@ void Application::notifyTorrentAdded(Torrent const* tor) const
 
 void Application::saveGeometry() const
 {
-    if (prefs_ != nullptr && window_ != nullptr)
+    if (window_ != nullptr)
     {
         auto const geometry = window_->geometry();
-        prefs_->set(Prefs::MAIN_WINDOW_HEIGHT, std::max(100, geometry.height()));
-        prefs_->set(Prefs::MAIN_WINDOW_WIDTH, std::max(100, geometry.width()));
-        prefs_->set(Prefs::MAIN_WINDOW_X, geometry.x());
-        prefs_->set(Prefs::MAIN_WINDOW_Y, geometry.y());
+        prefs_.set(Prefs::MAIN_WINDOW_HEIGHT, std::max(100, geometry.height()));
+        prefs_.set(Prefs::MAIN_WINDOW_WIDTH, std::max(100, geometry.width()));
+        prefs_.set(Prefs::MAIN_WINDOW_X, geometry.x());
+        prefs_.set(Prefs::MAIN_WINDOW_Y, geometry.y());
     }
 }
 
@@ -368,7 +368,7 @@ void Application::refreshPref(int key) const
 
     case Prefs::DIR_WATCH:
     case Prefs::DIR_WATCH_ENABLED:
-        watch_dir_->setPath(prefs_->get<QString>(Prefs::DIR_WATCH), prefs_->get<bool>(Prefs::DIR_WATCH_ENABLED));
+        watch_dir_->setPath(prefs_.get<QString>(Prefs::DIR_WATCH), prefs_.get<bool>(Prefs::DIR_WATCH_ENABLED));
         break;
 
     default:
@@ -378,19 +378,19 @@ void Application::refreshPref(int key) const
 
 void Application::maybeUpdateBlocklist() const
 {
-    if (!prefs_->get<bool>(Prefs::BLOCKLIST_UPDATES_ENABLED))
+    if (!prefs_.get<bool>(Prefs::BLOCKLIST_UPDATES_ENABLED))
     {
         return;
     }
 
-    QDateTime const last_updated_at = prefs_->get<QDateTime>(Prefs::BLOCKLIST_DATE);
-    QDateTime const next_update_at = last_updated_at.addDays(7);
-    QDateTime const now = QDateTime::currentDateTime();
+    auto const last_updated_at = prefs_.get<QDateTime>(Prefs::BLOCKLIST_DATE);
+    auto const next_update_at = last_updated_at.addDays(7);
+    auto const now = QDateTime::currentDateTime();
 
     if (now < next_update_at)
     {
         session_->updateBlocklist();
-        prefs_->set(Prefs::BLOCKLIST_DATE, now);
+        prefs_.set(Prefs::BLOCKLIST_DATE, now);
     }
 }
 
@@ -426,8 +426,8 @@ void Application::refreshTorrents()
 void Application::addWatchdirTorrent(QString const& filename) const
 {
     auto add_data = AddData{ filename };
-    auto const disposal = prefs_->get<bool>(Prefs::TRASH_ORIGINAL) ? AddData::FilenameDisposal::Delete :
-                                                                     AddData::FilenameDisposal::Rename;
+    auto const disposal = prefs_.get<bool>(Prefs::TRASH_ORIGINAL) ? AddData::FilenameDisposal::Delete :
+                                                                    AddData::FilenameDisposal::Rename;
     add_data.setFileDisposal(disposal);
     addTorrent(std::move(add_data));
 }
@@ -441,18 +441,18 @@ void Application::addTorrent(AddData addme) const
 
     // if there's not already a disposal action set,
     // then honor the `trash original` preference setting
-    if (!addme.fileDisposal() && prefs_->get<bool>(Prefs::TRASH_ORIGINAL))
+    if (!addme.fileDisposal() && prefs_.get<bool>(Prefs::TRASH_ORIGINAL))
     {
         addme.setFileDisposal(AddData::FilenameDisposal::Delete);
     }
 
-    if (!prefs_->get<bool>(Prefs::OPTIONS_PROMPT))
+    if (!prefs_.get<bool>(Prefs::OPTIONS_PROMPT))
     {
         session_->addTorrent(addme);
     }
     else
     {
-        auto* o = new OptionsDialog{ *session_, *prefs_, addme, window_.get() };
+        auto* o = new OptionsDialog{ *session_, prefs_, addme, window_.get() };
         o->show();
     }
 
diff --git a/qt/Application.h b/qt/Application.h
index 73ad19e71..2e9fee163 100644
--- a/qt/Application.h
+++ b/qt/Application.h
@@ -36,13 +36,7 @@ class Application : public QApplication
     Q_OBJECT
 
 public:
-    Application(
-        std::unique_ptr<Prefs> prefs,
-        bool minimized,
-        QString const& config_dir,
-        QStringList const& filenames,
-        int& argc,
-        char** argv);
+    Application(Prefs& prefs, bool minimized, QString const& config_dir, QStringList const& filenames, int& argc, char** argv);
     Application(Application&&) = delete;
     Application(Application const&) = delete;
     Application& operator=(Application&&) = delete;
@@ -107,7 +101,7 @@ private:
 
     std::unordered_set<QString> interned_strings_;
 
-    std::unique_ptr<Prefs> prefs_;
+    Prefs& prefs_;
     std::unique_ptr<Session> session_;
     std::unique_ptr<TorrentModel> model_;
     std::unique_ptr<MainWindow> window_;
diff --git a/qt/CMakeLists.txt b/qt/CMakeLists.txt
index 1a6f81ef2..3cdfe061a 100644
--- a/qt/CMakeLists.txt
+++ b/qt/CMakeLists.txt
@@ -3,9 +3,9 @@ set_property(GLOBAL PROPERTY AUTOGEN_SOURCE_GROUP "Generated Files")
 # https://doc.qt.io/qt-6/macos.html#supported-versions
 set(CMAKE_OSX_DEPLOYMENT_TARGET 11)
 
-add_executable(${TR_NAME}-qt WIN32)
+add_library(${TR_NAME}-qt-lib STATIC)
 
-target_sources(${TR_NAME}-qt
+target_sources(${TR_NAME}-qt-lib
     PRIVATE
         AboutDialog.cc
         AboutDialog.h
@@ -56,7 +56,6 @@ target_sources(${TR_NAME}-qt
         InteropObject.h
         LicenseDialog.cc
         LicenseDialog.h
-        main.cc
         MainWindow.cc
         MainWindow.h
         MakeDialog.cc
@@ -107,6 +106,8 @@ target_sources(${TR_NAME}-qt
         TrackerModel.h
         TrackerModelFilter.cc
         TrackerModelFilter.h
+        TrQtInit.cc
+        TrQtInit.h
         Typedefs.h
         Utils.cc
         Utils.h
@@ -121,7 +122,7 @@ tr_allow_compile_if(
     [=[[ENABLE_QT_DBUS_INTEROP]]=]
         DBusInteropHelper.cc)
 
-target_sources(${TR_NAME}-qt
+target_sources(${TR_NAME}-qt-lib
     PRIVATE
         AboutDialog.ui
         DetailsDialog.ui
@@ -139,7 +140,7 @@ target_sources(${TR_NAME}-qt
 source_group(Ui
     REGULAR_EXPRESSION [[.*\.ui$]])
 
-target_sources(${TR_NAME}-qt
+target_sources(${TR_NAME}-qt-lib
     PRIVATE
         application.qrc)
 
@@ -196,35 +197,49 @@ if(TS_FILES)
     tr_qt_add_translation(QM_FILES ${TS_FILES})
 endif()
 
-target_sources(${TR_NAME}-qt
+target_sources(${TR_NAME}-qt-lib
     PRIVATE
         ${QM_FILES})
 
 if(ENABLE_QT_COM_INTEROP)
-    tr_target_idl_files(${TR_NAME}-qt
+    tr_target_idl_files(${TR_NAME}-qt-lib
         transmission-qt.idl)
 endif()
 
-target_include_directories(${TR_NAME}-qt
-    PRIVATE
+target_include_directories(${TR_NAME}-qt-lib
+    PUBLIC
         ${CMAKE_CURRENT_SOURCE_DIR})
 
-target_link_libraries(${TR_NAME}-qt
-    PRIVATE
+target_link_libraries(${TR_NAME}-qt-lib
+    PUBLIC
         ${TR_NAME}-app
         ${TR_NAME}
         transmission::qt_impl)
 
-target_compile_definitions(${TR_NAME}-qt
+target_compile_definitions(${TR_NAME}-qt-lib
     PRIVATE
         "TRANSLATIONS_DIR=\"${CMAKE_INSTALL_FULL_DATADIR}/${TR_NAME}/translations\""
         QT_NO_CAST_FROM_ASCII
         $<$<BOOL:${ENABLE_QT_COM_INTEROP}>:ENABLE_COM_INTEROP>
         $<$<BOOL:${ENABLE_QT_DBUS_INTEROP}>:ENABLE_DBUS_INTEROP>)
 
-if(MSVC)
-    tr_append_target_property(${TR_NAME}-qt LINK_FLAGS "/ENTRY:mainCRTStartup")
-endif()
+set_target_properties(
+    ${TR_NAME}-qt-lib
+    PROPERTIES
+        AUTOMOC ON
+        AUTORCC ON
+        AUTOUIC ON)
+
+add_executable(${TR_NAME}-qt WIN32)
+
+target_sources(${TR_NAME}-qt
+    PRIVATE
+        main.cc
+        application.qrc)
+
+target_link_libraries(${TR_NAME}-qt
+    PRIVATE
+        ${TR_NAME}-qt-lib)
 
 set_target_properties(
     ${TR_NAME}-qt
@@ -233,6 +248,10 @@ set_target_properties(
         AUTORCC ON
         AUTOUIC ON)
 
+if(MSVC)
+    tr_append_target_property(${TR_NAME}-qt LINK_FLAGS "/ENTRY:mainCRTStartup")
+endif()
+
 tr_win32_app_info(${TR_NAME}-qt
     "Transmission Qt Client"
     "${TR_NAME}-qt"
diff --git a/qt/Prefs.cc b/qt/Prefs.cc
index 068064d29..d7a730514 100644
--- a/qt/Prefs.cc
+++ b/qt/Prefs.cc
@@ -3,20 +3,14 @@
 // or any future license endorsed by Mnemosyne LLC.
 // License text can be found in the licenses/ folder.
 
-#include <algorithm>
 #include <array>
 #include <cassert>
+#include <optional>
 #include <string_view>
 #include <utility>
 
 #include <QDateTime>
 #include <QDir>
-#include <QFile>
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
-#include <QStringDecoder>
-#else
-#include <QTextCodec>
-#endif
 
 #include <libtransmission/transmission.h>
 
@@ -27,42 +21,108 @@
 #include "CustomVariantType.h"
 #include "Filters.h"
 #include "Prefs.h"
-#include "VariantHelpers.h"
 
 namespace api_compat = libtransmission::api_compat;
-using libtransmission::serializer::to_value;
-using libtransmission::serializer::to_variant;
-using ::trqt::variant_helpers::dictAdd;
-using ::trqt::variant_helpers::getValue;
+namespace ser = libtransmission::serializer;
 using namespace std::string_view_literals;
 
 // ---
 
 namespace
 {
-
-void ensureSoundCommandIsAList(tr_variant* dict)
+template<typename T>
+[[nodiscard]] QVariant qvarFromOptional(std::optional<T> const& val)
 {
-    tr_quark const key = TR_KEY_torrent_complete_sound_command;
-
-    if (tr_variant* list = nullptr; tr_variantDictFindList(dict, key, &list))
-    {
-        return;
-    }
-
-    tr_variantDictRemove(dict, key);
-    dictAdd(
-        dict,
-        key,
-        std::array<std::string_view, 5>{
-            "canberra-gtk-play",
-            "-i",
-            "complete-download",
-            "-d",
-            "transmission torrent downloaded",
-        });
+    return val ? QVariant::fromValue(*val) : QVariant{};
 }
 
+[[nodiscard]] QVariant qvarFromTVar(tr_variant const& var, int const qt_metatype)
+{
+    switch (qt_metatype)
+    {
+    case QMetaType::Int:
+        return qvarFromOptional(ser::to_value<int64_t>(var));
+
+    case CustomVariantType::EncryptionModeType:
+        return qvarFromOptional(ser::to_value<tr_encryption_mode>(var));
+
+    case CustomVariantType::SortModeType:
+        return qvarFromOptional(ser::to_value<SortMode>(var));
+
+    case CustomVariantType::ShowModeType:
+        return qvarFromOptional(ser::to_value<ShowMode>(var));
+
+    case QMetaType::QString:
+        return qvarFromOptional(ser::to_value<QString>(var));
+
+    case QMetaType::QStringList:
+        return qvarFromOptional(ser::to_value<QStringList>(var));
+
+    case QMetaType::Bool:
+        return qvarFromOptional(ser::to_value<bool>(var));
+
+    case QMetaType::Double:
+        return qvarFromOptional(ser::to_value<double>(var));
+
+    case QMetaType::QDateTime:
+        return qvarFromOptional(ser::to_value<QDateTime>(var));
+
+    default:
+        assert(false && "unhandled type");
+        return {};
+    }
+}
+
+[[nodiscard]] tr_variant trvarFromQVar(QVariant const& var, int const qt_metatype)
+{
+    switch (qt_metatype)
+    {
+    case QMetaType::Int:
+        return ser::to_variant(var.value<int>());
+
+    case CustomVariantType::EncryptionModeType:
+        return ser::to_variant(var.value<tr_encryption_mode>());
+
+    case CustomVariantType::SortModeType:
+        return ser::to_variant(var.value<SortMode>());
+
+    case CustomVariantType::ShowModeType:
+        return ser::to_variant(var.value<ShowMode>());
+
+    case QMetaType::QString:
+        return ser::to_variant(var.value<QString>());
+
+    case QMetaType::QStringList:
+        return ser::to_variant(var.value<QStringList>());
+
+    case QMetaType::Bool:
+        return ser::to_variant(var.value<bool>());
+
+    case QMetaType::Double:
+        return ser::to_variant(var.value<double>());
+
+    case QMetaType::QDateTime:
+        return ser::to_variant(var.value<QDateTime>());
+
+    default:
+        assert(false && "unhandled type");
+        return {};
+    }
+}
+
+void ensureSoundCommandIsAList(tr_variant::Map& map)
+{
+    auto constexpr Key = TR_KEY_torrent_complete_sound_command;
+    auto constexpr DefaultVal = std::array<std::string_view, 5U>{ "canberra-gtk-play",
+                                                                  "-i",
+                                                                  "complete-download",
+                                                                  "-d",
+                                                                  "transmission torrent downloaded" };
+    if (map.find_if<tr_variant::Vector>(Key) == nullptr)
+    {
+        map.insert_or_assign(Key, ser::to_variant(DefaultVal));
+    }
+}
 } // namespace
 
 std::array<Prefs::PrefItem, Prefs::PREFS_COUNT> const Prefs::Items{
@@ -182,224 +242,119 @@ namespace
 }
 } // namespace
 
-/***
-****
-***/
+// ---
 
-Prefs::Prefs(QString config_dir)
-    : config_dir_{ std::move(config_dir) }
+Prefs::Prefs()
 {
     static_assert(sizeof(Items) / sizeof(Items[0]) == PREFS_COUNT);
-
 #ifndef NDEBUG
     for (int i = 0; i < PREFS_COUNT; ++i)
     {
         assert(Items[i].id == i);
     }
-
 #endif
 
-    auto const app_defaults = get_default_app_settings();
-    auto settings = tr_sessionLoadSettings(config_dir_.toStdString(), &app_defaults);
-    ensureSoundCommandIsAList(&settings);
+    load(defaults());
+}
 
-    for (int i = 0; i < PREFS_COUNT; ++i)
+void Prefs::loadFromConfigDir(QString const dir)
+{
+    auto settings = tr_sessionLoadSettings(dir.toStdString());
+    if (auto* const map = settings.get_if<tr_variant::Map>())
     {
-        tr_variant const* b = tr_variantDictFind(&settings, getKey(i));
+        ensureSoundCommandIsAList(*map);
+        load(*map);
+    }
+}
 
-        switch (Items[i].type)
+void Prefs::load(tr_variant::Map const& settings)
+{
+    for (int idx = 0; idx < PREFS_COUNT; ++idx)
+    {
+        if (auto const iter = settings.find(getKey(idx)); iter != settings.end())
         {
-        case QMetaType::Int:
-            if (auto const value = getValue<int64_t>(b); value)
-            {
-                values_[i].setValue(*value);
-            }
-            break;
-
-        case CustomVariantType::EncryptionModeType:
-            if (auto const val = to_value<tr_encryption_mode>(*b))
-            {
-                values_[i] = QVariant::fromValue(*val);
-            }
-            break;
-
-        case CustomVariantType::SortModeType:
-            if (auto const val = to_value<SortMode>(*b))
-            {
-                values_[i] = QVariant::fromValue(*val);
-            }
-            break;
-
-        case CustomVariantType::ShowModeType:
-            if (auto const val = to_value<ShowMode>(*b))
-            {
-                values_[i] = QVariant::fromValue(*val);
-            }
-            break;
-
-        case QMetaType::QString:
-            if (auto const value = getValue<QString>(b); value)
-            {
-                values_[i].setValue(*value);
-            }
-            break;
-
-        case QMetaType::QStringList:
-            if (auto const value = getValue<QStringList>(b); value)
-            {
-                values_[i].setValue(*value);
-            }
-            break;
-
-        case QMetaType::Bool:
-            if (auto const value = getValue<bool>(b); value)
-            {
-                values_[i].setValue(*value);
-            }
-            break;
-
-        case QMetaType::Double:
-            if (auto const value = getValue<double>(b); value)
-            {
-                values_[i].setValue(*value);
-            }
-            break;
-
-        case QMetaType::QDateTime:
-            if (auto const value = getValue<time_t>(b); value)
-            {
-                values_[i].setValue(QDateTime::fromSecsSinceEpoch(*value));
-            }
-            break;
-
-        default:
-            assert(false && "unhandled type");
-            break;
+            values_[idx] = qvarFromTVar(iter->second, Items[idx].type);
         }
     }
 }
 
-Prefs::~Prefs()
+tr_variant::Map Prefs::current_settings() const
 {
-    // make a dict from settings.json
-    tr_variant current_settings;
-    tr_variantInitDict(&current_settings, PREFS_COUNT);
+    auto map = tr_variant::Map{ PREFS_COUNT };
 
-    for (int i = 0; i < PREFS_COUNT; ++i)
+    for (int idx = 0; idx < PREFS_COUNT; ++idx)
     {
-        if (!prefIsSavable(i))
+        if (prefIsSavable(idx))
         {
-            continue;
-        }
-
-        auto const key = getKey(i);
-        auto const& val = values_[i];
-
-        switch (Items[i].type)
-        {
-        case QMetaType::Int:
-            dictAdd(&current_settings, key, val.toInt());
-            break;
-
-        case CustomVariantType::EncryptionModeType:
-            *tr_variantDictAdd(&current_settings, key) = to_variant(val.value<tr_encryption_mode>());
-            break;
-
-        case CustomVariantType::SortModeType:
-            *tr_variantDictAdd(&current_settings, key) = to_variant(val.value<SortMode>());
-            break;
-
-        case CustomVariantType::ShowModeType:
-            *tr_variantDictAdd(&current_settings, key) = to_variant(val.value<ShowMode>());
-            break;
-
-        case QMetaType::QString:
-            dictAdd(&current_settings, key, val.toString());
-            break;
-
-        case QMetaType::QStringList:
-            dictAdd(&current_settings, key, val.toStringList());
-            break;
-
-        case QMetaType::Bool:
-            dictAdd(&current_settings, key, val.toBool());
-            break;
-
-        case QMetaType::Double:
-            dictAdd(&current_settings, key, val.toDouble());
-            break;
-
-        case QMetaType::QDateTime:
-            dictAdd(&current_settings, key, int64_t{ val.toDateTime().toSecsSinceEpoch() });
-            break;
-
-        default:
-            assert(false && "unhandled type");
-            break;
+            map.try_emplace(Items[idx].key, trvarFromQVar(values_[idx], Items[idx].type));
         }
     }
 
-    // update settings.json with our settings
+    return map;
+}
+
+void Prefs::save(QString const& filename) const
+{
+    auto const filename_str = filename.toStdString();
     auto serde = tr_variant_serde::json();
-    auto const file = QFile{ QDir{ config_dir_ }.absoluteFilePath(QStringLiteral("settings.json")) };
-    auto const filename = file.fileName().toStdString();
-    auto settings = tr_variant::make_map(PREFS_COUNT);
-    if (auto const file_settings = serde.parse_file(filename); file_settings)
-    {
-        settings.merge(*file_settings);
-    }
 
-    settings.merge(current_settings);
+    auto settings = tr_variant::make_map(PREFS_COUNT);
+    if (auto const var = serde.parse_file(filename_str))
+    {
+        settings.merge(*var);
+    }
+    settings.merge(tr_variant{ current_settings() });
     api_compat::convert_outgoing_data(settings);
-    serde.to_file(settings, filename);
+    serde.to_file(settings, filename_str);
 }
 
 /**
  * This is where we initialize the preferences file with the default values.
  * If you add a new preferences key, you /must/ add a default value here.
  */
-tr_variant Prefs::get_default_app_settings()
+// static
+tr_variant::Map Prefs::defaults()
 {
     auto const download_dir = tr_getDefaultDownloadDir();
 
-    auto settings = tr_variant::Map{ 64U };
-    settings.try_emplace(TR_KEY_blocklist_date, 0);
-    settings.try_emplace(TR_KEY_blocklist_updates_enabled, true);
-    settings.try_emplace(TR_KEY_compact_view, false);
-    settings.try_emplace(TR_KEY_download_dir, download_dir);
-    settings.try_emplace(TR_KEY_filter_mode, to_variant(DefaultShowMode));
-    settings.try_emplace(TR_KEY_inhibit_desktop_hibernation, false);
-    settings.try_emplace(TR_KEY_main_window_height, 500);
-    settings.try_emplace(TR_KEY_main_window_layout_order, tr_variant::unmanaged_string("menu,toolbar,filter,list,statusbar"sv));
-    settings.try_emplace(TR_KEY_main_window_width, 600);
-    settings.try_emplace(TR_KEY_main_window_x, 50);
-    settings.try_emplace(TR_KEY_main_window_y, 50);
-    settings.try_emplace(TR_KEY_open_dialog_dir, QDir::home().absolutePath().toStdString());
-    settings.try_emplace(TR_KEY_prompt_before_exit, true);
-    settings.try_emplace(TR_KEY_read_clipboard, false);
-    settings.try_emplace(TR_KEY_remote_session_enabled, false);
-    settings.try_emplace(TR_KEY_remote_session_host, tr_variant::unmanaged_string("localhost"sv));
-    settings.try_emplace(TR_KEY_remote_session_https, false);
-    settings.try_emplace(TR_KEY_remote_session_password, tr_variant::unmanaged_string(""sv));
-    settings.try_emplace(TR_KEY_remote_session_port, TrDefaultRpcPort);
-    settings.try_emplace(TR_KEY_remote_session_requires_authentication, false);
-    settings.try_emplace(TR_KEY_remote_session_url_base_path, tr_variant::unmanaged_string(TrHttpServerDefaultBasePath));
-    settings.try_emplace(TR_KEY_remote_session_username, tr_variant::unmanaged_string(""sv));
-    settings.try_emplace(TR_KEY_show_backup_trackers, false);
-    settings.try_emplace(TR_KEY_show_filterbar, true);
-    settings.try_emplace(TR_KEY_show_notification_area_icon, false);
-    settings.try_emplace(TR_KEY_show_options_window, true);
-    settings.try_emplace(TR_KEY_show_statusbar, true);
-    settings.try_emplace(TR_KEY_show_toolbar, true);
-    settings.try_emplace(TR_KEY_show_tracker_scrapes, false);
-    settings.try_emplace(TR_KEY_sort_mode, to_variant(DefaultSortMode));
-    settings.try_emplace(TR_KEY_sort_reversed, false);
-    settings.try_emplace(TR_KEY_start_minimized, false);
-    settings.try_emplace(TR_KEY_statusbar_stats, tr_variant::unmanaged_string("total-ratio"));
-    settings.try_emplace(TR_KEY_torrent_added_notification_enabled, true);
-    settings.try_emplace(TR_KEY_torrent_complete_notification_enabled, true);
-    settings.try_emplace(TR_KEY_torrent_complete_sound_enabled, true);
-    settings.try_emplace(TR_KEY_watch_dir, download_dir);
-    settings.try_emplace(TR_KEY_watch_dir_enabled, false);
-    return tr_variant{ std::move(settings) };
+    auto map = tr_variant::Map{ 64U };
+    map.try_emplace(TR_KEY_blocklist_date, 0);
+    map.try_emplace(TR_KEY_blocklist_updates_enabled, true);
+    map.try_emplace(TR_KEY_compact_view, false);
+    map.try_emplace(TR_KEY_download_dir, download_dir);
+    map.try_emplace(TR_KEY_filter_mode, ser::to_variant(DefaultShowMode));
+    map.try_emplace(TR_KEY_inhibit_desktop_hibernation, false);
+    map.try_emplace(TR_KEY_main_window_height, 500);
+    map.try_emplace(TR_KEY_main_window_layout_order, tr_variant::unmanaged_string("menu,toolbar,filter,list,statusbar"sv));
+    map.try_emplace(TR_KEY_main_window_width, 600);
+    map.try_emplace(TR_KEY_main_window_x, 50);
+    map.try_emplace(TR_KEY_main_window_y, 50);
+    map.try_emplace(TR_KEY_open_dialog_dir, QDir::home().absolutePath().toStdString());
+    map.try_emplace(TR_KEY_prompt_before_exit, true);
+    map.try_emplace(TR_KEY_read_clipboard, false);
+    map.try_emplace(TR_KEY_remote_session_enabled, false);
+    map.try_emplace(TR_KEY_remote_session_host, tr_variant::unmanaged_string("localhost"sv));
+    map.try_emplace(TR_KEY_remote_session_https, false);
+    map.try_emplace(TR_KEY_remote_session_password, tr_variant::unmanaged_string(""sv));
+    map.try_emplace(TR_KEY_remote_session_port, TrDefaultRpcPort);
+    map.try_emplace(TR_KEY_remote_session_requires_authentication, false);
+    map.try_emplace(TR_KEY_remote_session_url_base_path, tr_variant::unmanaged_string(TrHttpServerDefaultBasePath));
+    map.try_emplace(TR_KEY_remote_session_username, tr_variant::unmanaged_string(""sv));
+    map.try_emplace(TR_KEY_show_backup_trackers, false);
+    map.try_emplace(TR_KEY_show_filterbar, true);
+    map.try_emplace(TR_KEY_show_notification_area_icon, false);
+    map.try_emplace(TR_KEY_show_options_window, true);
+    map.try_emplace(TR_KEY_show_statusbar, true);
+    map.try_emplace(TR_KEY_show_toolbar, true);
+    map.try_emplace(TR_KEY_show_tracker_scrapes, false);
+    map.try_emplace(TR_KEY_sort_mode, ser::to_variant(DefaultSortMode));
+    map.try_emplace(TR_KEY_sort_reversed, false);
+    map.try_emplace(TR_KEY_start_minimized, false);
+    map.try_emplace(TR_KEY_statusbar_stats, tr_variant::unmanaged_string("total-ratio"));
+    map.try_emplace(TR_KEY_torrent_added_notification_enabled, true);
+    map.try_emplace(TR_KEY_torrent_complete_notification_enabled, true);
+    map.try_emplace(TR_KEY_torrent_complete_sound_enabled, true);
+    map.try_emplace(TR_KEY_watch_dir, download_dir);
+    map.try_emplace(TR_KEY_watch_dir_enabled, false);
+    return map;
 }
diff --git a/qt/Prefs.h b/qt/Prefs.h
index d91ed7610..c6210f642 100644
--- a/qt/Prefs.h
+++ b/qt/Prefs.h
@@ -12,16 +12,10 @@
 #include <QVariant>
 
 #include <libtransmission/quark.h>
+#include <libtransmission/variant.h>
 
 #include <libtransmission-app/display-modes.h>
 
-class QDateTime;
-
-extern "C"
-{
-    struct tr_variant;
-}
-
 class Prefs : public QObject
 {
     Q_OBJECT
@@ -131,37 +125,36 @@ public:
         PREFS_COUNT
     };
 
-    explicit Prefs(QString config_dir);
+    Prefs();
     Prefs(Prefs&&) = delete;
     Prefs(Prefs const&) = delete;
     Prefs& operator=(Prefs&&) = delete;
     Prefs& operator=(Prefs const&) = delete;
-    ~Prefs() override;
+    ~Prefs() override = default;
 
-    [[nodiscard]] constexpr auto isCore(int key) const noexcept
+    [[nodiscard]] static auto constexpr isCore(int const idx)
     {
-        return FIRST_CORE_PREF <= key && key <= LAST_CORE_PREF;
+        return FIRST_CORE_PREF <= idx && idx <= LAST_CORE_PREF;
     }
 
-    [[nodiscard]] constexpr auto getKey(int i) const noexcept
+    [[nodiscard]] static auto constexpr getKey(int const idx)
     {
-        return Items[i].key;
+        return Items[idx].key;
     }
 
-    [[nodiscard]] constexpr auto type(int i) const noexcept
+    [[nodiscard]] static auto constexpr type(int const idx)
     {
-        return Items[i].type;
+        return Items[idx].type;
     }
 
-    [[nodiscard]] constexpr auto const& variant(int i) const noexcept
-    {
-        return values_[i];
-    }
+    void loadFromConfigDir(QString dir);
 
-    template<typename T>
-    [[nodiscard]] T get(int const key) const
+    void load(tr_variant::Map const& settings);
+
+    // DEPRECATED
+    [[nodiscard]] constexpr auto const& variant(int const idx) const noexcept
     {
-        return values_[key].value<T>();
+        return values_[idx];
     }
 
     template<typename T>
@@ -177,8 +170,18 @@ public:
         }
     }
 
+    template<typename T>
+    [[nodiscard]] T get(int const idx) const
+    {
+        return values_[idx].value<T>();
+    }
+
+    [[nodiscard]] tr_variant::Map current_settings() const;
+
+    void save(QString const& filename) const;
+
 signals:
-    void changed(int key);
+    void changed(int idx);
 
 private:
     struct PrefItem
@@ -188,13 +191,11 @@ private:
         int type;
     };
 
-    [[nodiscard]] static tr_variant get_default_app_settings();
+    static std::array<PrefItem, PREFS_COUNT> const Items;
+
+    [[nodiscard]] static tr_variant::Map defaults();
 
     void set(int key, char const* value) = delete;
 
-    QString const config_dir_;
-
     std::array<QVariant, PREFS_COUNT> mutable values_;
-
-    static std::array<PrefItem, PREFS_COUNT> const Items;
 };
diff --git a/qt/Session.cc b/qt/Session.cc
index 0c5c7f970..0cd54d497 100644
--- a/qt/Session.cc
+++ b/qt/Session.cc
@@ -63,7 +63,7 @@ void Session::sessionSet(tr_quark const key, QVariant const& value)
 #if QT_VERSION >= QT_VERSION_CHECK(6, 2, 0)
     switch (value.typeId())
 #else
-    switch (static_cast<QMetaType::Type>(value.type()))
+    switch (value.userType())
 #endif
     {
     case QMetaType::Bool:
@@ -166,7 +166,7 @@ void Session::copyMagnetLinkToClipboard(int torrent_id)
 
 void Session::updatePref(int key)
 {
-    if (prefs_.isCore(key))
+    if (Prefs::isCore(key))
     {
         switch (key)
         {
@@ -209,11 +209,11 @@ void Session::updatePref(int key)
         case Prefs::USPEED:
         case Prefs::USPEED_ENABLED:
         case Prefs::UTP_ENABLED:
-            sessionSet(prefs_.getKey(key), prefs_.variant(key));
+            sessionSet(Prefs::getKey(key), prefs_.variant(key));
             break;
 
         case Prefs::DOWNLOAD_DIR:
-            sessionSet(prefs_.getKey(key), prefs_.variant(key));
+            sessionSet(Prefs::getKey(key), prefs_.variant(key));
             /* this will change the 'freespace' argument, so refresh */
             refreshSessionInfo();
             break;
@@ -890,14 +890,14 @@ void Session::updateInfo(tr_variant* args_dict)
 
     for (int i = Prefs::FIRST_CORE_PREF; i <= Prefs::LAST_CORE_PREF; ++i)
     {
-        tr_variant const* b(tr_variantDictFind(args_dict, prefs_.getKey(i)));
+        tr_variant const* b(tr_variantDictFind(args_dict, Prefs::getKey(i)));
 
         if (b == nullptr)
         {
             continue;
         }
 
-        switch (prefs_.type(i))
+        switch (Prefs::type(i))
         {
         case QMetaType::Int:
             if (auto const value = getValue<int>(b); value)
diff --git a/qt/TrQtInit.cc b/qt/TrQtInit.cc
new file mode 100644
index 000000000..c5d37fbd1
--- /dev/null
+++ b/qt/TrQtInit.cc
@@ -0,0 +1,21 @@
+// This file Copyright © Mnemosyne LLC.
+// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
+// or any future license endorsed by Mnemosyne LLC.
+// License text can be found in the licenses/ folder.
+
+#include "TrQtInit.h"
+
+#include <libtransmission-app/app.h>
+
+#include "VariantHelpers.h"
+
+namespace trqt
+{
+
+void trqt_init()
+{
+    transmission::app::init();
+    trqt::variant_helpers::register_qt_converters();
+}
+
+} // namespace trqt
diff --git a/qt/TrQtInit.h b/qt/TrQtInit.h
new file mode 100644
index 000000000..d45e8bdb1
--- /dev/null
+++ b/qt/TrQtInit.h
@@ -0,0 +1,13 @@
+// This file Copyright © Mnemosyne LLC.
+// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
+// or any future license endorsed by Mnemosyne LLC.
+// License text can be found in the licenses/ folder.
+
+#pragma once
+
+namespace trqt
+{
+
+void trqt_init();
+
+} // namespace trqt
diff --git a/qt/Utils.cc b/qt/Utils.cc
index 78d1c1a85..1c0cdde39 100644
--- a/qt/Utils.cc
+++ b/qt/Utils.cc
@@ -43,7 +43,7 @@ QIcon Utils::getIconFromIndex(QModelIndex const& index)
 #if QT_VERSION >= QT_VERSION_CHECK(6, 2, 0)
     switch (variant.typeId())
 #else
-    switch (static_cast<QMetaType::Type>(variant.type()))
+    switch (variant.userType())
 #endif
     {
     case QMetaType::QIcon:
diff --git a/qt/VariantHelpers.cc b/qt/VariantHelpers.cc
index e71ee7d8b..f96bd9a5e 100644
--- a/qt/VariantHelpers.cc
+++ b/qt/VariantHelpers.cc
@@ -11,6 +11,7 @@
 #include <mutex>
 #include <string_view>
 
+#include <QDateTime>
 #include <QUrl>
 
 #include <libtransmission/serializer.h>
@@ -19,6 +20,8 @@
 #include "Speed.h"
 #include "Torrent.h"
 
+namespace ser = libtransmission::serializer;
+
 namespace trqt::variant_helpers
 {
 
@@ -253,6 +256,42 @@ tr_variant fromInt(int const& val)
 {
     return static_cast<int64_t>(val);
 }
+
+// ---
+
+bool toQDateTime(tr_variant const& src, QDateTime* tgt)
+{
+    if (auto const val = ser::to_value<int64_t>(src))
+    {
+        *tgt = QDateTime::fromSecsSinceEpoch(*val);
+        return true;
+    }
+
+    return false;
+}
+
+tr_variant fromQDateTime(QDateTime const& src)
+{
+    return ser::to_variant(int64_t{ src.toSecsSinceEpoch() });
+}
+
+// ---
+
+bool toQString(tr_variant const& src, QString* tgt)
+{
+    if (auto const val = src.value_if<std::string_view>())
+    {
+        *tgt = QString::fromUtf8(std::data(*val), std::size(*val));
+        return true;
+    }
+
+    return false;
+}
+
+tr_variant fromQString(QString const& val)
+{
+    return val.toStdString();
+}
 } // namespace
 
 void register_qt_converters()
@@ -264,6 +303,8 @@ void register_qt_converters()
         {
             using namespace libtransmission::serializer;
             Converters::add(toInt, fromInt);
+            Converters::add(toQDateTime, fromQDateTime);
+            Converters::add(toQString, fromQString);
         });
 }
 
diff --git a/qt/main.cc b/qt/main.cc
index 05c56ed74..6dada0cdb 100644
--- a/qt/main.cc
+++ b/qt/main.cc
@@ -7,6 +7,8 @@
 #include <memory>
 #include <string_view>
 
+#include <QDir>
+
 #include <fmt/format.h>
 
 #include <libtransmission/transmission.h>
@@ -203,40 +205,41 @@ int tr_main(int argc, char** argv)
     }
 
     // initialize the prefs
-    auto prefs = std::make_unique<Prefs>(config_dir);
+    auto prefs = Prefs{};
+    prefs.loadFromConfigDir(config_dir);
 
     if (!host.isNull())
     {
-        prefs->set(Prefs::SESSION_REMOTE_HOST, host);
+        prefs.set(Prefs::SESSION_REMOTE_HOST, host);
     }
 
     if (!port.isNull())
     {
-        prefs->set(Prefs::SESSION_REMOTE_PORT, port.toUInt());
+        prefs.set(Prefs::SESSION_REMOTE_PORT, port.toUInt());
     }
 
     if (!username.isNull())
     {
-        prefs->set(Prefs::SESSION_REMOTE_USERNAME, username);
+        prefs.set(Prefs::SESSION_REMOTE_USERNAME, username);
     }
 
     if (!password.isNull())
     {
-        prefs->set(Prefs::SESSION_REMOTE_PASSWORD, password);
+        prefs.set(Prefs::SESSION_REMOTE_PASSWORD, password);
     }
 
     if (!host.isNull() || !port.isNull() || !username.isNull() || !password.isNull())
     {
-        prefs->set(Prefs::SESSION_IS_REMOTE, true);
+        prefs.set(Prefs::SESSION_IS_REMOTE, true);
     }
 
-    if (prefs->get<bool>(Prefs::START_MINIMIZED))
+    if (prefs.get<bool>(Prefs::START_MINIMIZED))
     {
         minimized = true;
     }
 
     // start as minimized only if the system tray present
-    if (!prefs->get<bool>(Prefs::SHOW_TRAY_ICON))
+    if (!prefs.get<bool>(Prefs::SHOW_TRAY_ICON))
     {
         minimized = false;
     }
@@ -247,8 +250,14 @@ int tr_main(int argc, char** argv)
         qt_argv.insert(qt_argv.end(), &argv[qt_args_start_idx], &argv[argc]);
     }
 
+    // run the app
     auto qt_argc = static_cast<int>(std::size(qt_argv));
+    auto const app = Application{ prefs, minimized, config_dir, filenames, qt_argc, std::data(qt_argv) };
+    auto const ret = QApplication::exec();
 
-    Application const app(std::move(prefs), minimized, config_dir, filenames, qt_argc, std::data(qt_argv));
-    return QApplication::exec();
+    // save prefs before exiting
+    auto const filename = QDir{ config_dir }.absoluteFilePath(QStringLiteral("settings.json"));
+    prefs.save(filename);
+
+    return ret;
 }
diff --git a/release/windows/build-qt5.ps1 b/release/windows/build-qt5.ps1
index 5901b3525..4630261b1 100644
--- a/release/windows/build-qt5.ps1
+++ b/release/windows/build-qt5.ps1
@@ -58,8 +58,6 @@ function global:Build-Qt5([string] $PrefixDir, [string] $Arch, [string] $DepsPre
         '-no-sql-sqlite2'
         '-no-sql-tds'
         '-nomake'; 'examples'
-        '-nomake'; 'tests'
-        '-nomake'; 'tools'
         '-I'; (Join-Path $DepsPrefixDir include)
         '-L'; (Join-Path $DepsPrefixDir lib)
     )
diff --git a/release/windows/build-qt6.ps1 b/release/windows/build-qt6.ps1
index 7a852b8d9..80b1c15e0 100644
--- a/release/windows/build-qt6.ps1
+++ b/release/windows/build-qt6.ps1
@@ -89,7 +89,6 @@ function global:Build-Qt6([string] $PrefixDir, [string] $Arch, [string] $DepsPre
         '-no-feature-syntaxhighlighter'
         '-no-feature-systemsemaphore'
         '-no-feature-tablewidget'
-        '-no-feature-testlib'
         '-no-feature-textmarkdownreader'
         '-no-feature-textmarkdownwriter'
         '-no-feature-textodfwriter'
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 8e6c70384..4aa971546 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -3,3 +3,25 @@ add_subdirectory(libtransmission)
 if(ENABLE_UTILS)
     add_subdirectory(utils)
 endif()
+
+if(ENABLE_QT)
+    add_subdirectory(qt)
+endif()
+
+add_custom_target(all-tests)
+
+set_property(
+    TARGET all-tests
+    PROPERTY FOLDER "tests")
+
+if(TARGET libtransmission-test)
+    add_dependencies(all-tests libtransmission-test)
+endif()
+
+if(TARGET qt-tests)
+    add_dependencies(all-tests qt-tests)
+endif()
+
+if(TARGET transmission-show)
+    add_dependencies(all-tests transmission-show)
+endif()
diff --git a/tests/qt/.clang-tidy b/tests/qt/.clang-tidy
new file mode 100644
index 000000000..7f202edc2
--- /dev/null
+++ b/tests/qt/.clang-tidy
@@ -0,0 +1,60 @@
+---
+HeaderFilterRegex: .*/libtransmission/.*
+
+# TODO: Enable `portability-template-virtual-member-function` after https://github.com/llvm/llvm-project/issues/139031 is fixed
+# TODO: Enable `cppcoreguidelines-pro-bounds-pointer-arithmetic` after converting all pointers to std::span
+# PRs welcome to fix & re-enable any of these explicitly-disabled checks
+Checks: >
+  bugprone-*,
+  -bugprone-branch-clone,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-implicit-widening-of-multiplication-result,
+  -bugprone-narrowing-conversions,
+  cert-*,
+  -cert-err58-cpp,
+  -cert-int09-c,
+  clang-analyzer-*,
+  cppcoreguidelines-*,
+  -cppcoreguidelines-avoid-c-arrays,
+  -cppcoreguidelines-avoid-const-or-ref-data-members,
+  -cppcoreguidelines-avoid-magic-numbers,
+  -cppcoreguidelines-avoid-non-const-global-variables,
+  -cppcoreguidelines-macro-usage,
+  -cppcoreguidelines-narrowing-conversions,
+  -cppcoreguidelines-non-private-member-variables-in-classes,
+  -cppcoreguidelines-owning-memory,
+  -cppcoreguidelines-pro-bounds-array-to-pointer-decay,
+  -cppcoreguidelines-pro-bounds-constant-array-index,
+  -cppcoreguidelines-pro-bounds-pointer-arithmetic,
+  -cppcoreguidelines-pro-type-const-cast,
+  -cppcoreguidelines-pro-type-reinterpret-cast,
+  -cppcoreguidelines-pro-type-union-access,
+  -cppcoreguidelines-pro-type-vararg,
+  google-explicit-constructor,
+  misc-*,
+  -misc-include-cleaner,
+  -misc-no-recursion,
+  -misc-non-private-member-variables-in-classes,
+  modernize-*,
+  -modernize-use-trailing-return-type,
+  performance-*,
+  -performance-move-const-arg,
+  portability-*,
+  -portability-template-virtual-member-function,
+  readability-*,
+  -readability-enum-initial-value,
+  -readability-function-cognitive-complexity,
+  -readability-identifier-length,
+  -readability-magic-numbers,
+  -readability-qualified-auto,
+
+CheckOptions:
+  - { key: cppcoreguidelines-avoid-do-while.IgnoreMacros,                           value: true       }
+  - { key: cppcoreguidelines-rvalue-reference-param-not-moved.IgnoreUnnamedParams,  value: true       }
+  - { key: cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor,         value: true       }
+  - { key: readability-identifier-naming.ConstexprVariableCase,                     value: CamelCase  }
+  - { key: readability-identifier-naming.ParameterCase,                             value: lower_case }
+  - { key: readability-identifier-naming.PrivateMemberSuffix,                       value: _          }
+  - { key: readability-identifier-naming.ProtectedMemberSuffix,                     value: _          }
+  - { key: readability-identifier-naming.VariableCase,                              value: lower_case }
+  - { key: readability-implicit-bool-conversion.UseUpperCaseLiteralSuffix,          value: true       }
diff --git a/tests/qt/CMakeLists.txt b/tests/qt/CMakeLists.txt
new file mode 100644
index 000000000..b1bff2b4a
--- /dev/null
+++ b/tests/qt/CMakeLists.txt
@@ -0,0 +1,27 @@
+find_package(Qt${Qt_VERSION_MAJOR}Test ${QT_MINIMUM} REQUIRED)
+
+set_property(DIRECTORY PROPERTY INCLUDE_DIRECTORIES
+    ${CMAKE_BINARY_DIR}/qt/${TR_NAME}-qt-lib_autogen/include)
+set_property(DIRECTORY PROPERTY LINK_LIBRARIES
+    ${TR_NAME}-qt-lib
+    Qt${Qt_VERSION_MAJOR}::Test)
+
+function(add_trqt_test source)
+    get_filename_component(name_no_ext ${source} NAME_WE)
+    string(REGEX REPLACE "-test$" "" test_name ${name_no_ext})
+    set(target qt-test-${test_name})
+    add_executable(${target} ${source} ${CMAKE_CURRENT_SOURCE_DIR}/../../qt/application.qrc)
+    set_property(TARGET ${target} PROPERTY AUTOMOC ON)
+    set_property(TARGET ${target} PROPERTY AUTORCC ON)
+    add_test(NAME QT.${test_name} COMMAND ${target})
+endfunction()
+
+add_trqt_test(prefs-test.cc)
+
+add_custom_target(qt-tests
+    DEPENDS
+        qt-test-prefs)
+
+set_property(
+    TARGET qt-tests
+    PROPERTY FOLDER "tests")
diff --git a/tests/qt/prefs-test.cc b/tests/qt/prefs-test.cc
new file mode 100644
index 000000000..5b4268f33
--- /dev/null
+++ b/tests/qt/prefs-test.cc
@@ -0,0 +1,262 @@
+// This file Copyright © Mnemosyne LLC.
+// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
+// or any future license endorsed by Mnemosyne LLC.
+// License text can be found in the licenses/ folder.
+
+#include <string_view>
+
+#include <QApplication>
+#include <QDateTime>
+#include <QSignalSpy>
+#include <QString>
+#include <QStringList>
+#include <QTest>
+
+#include <fmt/format.h>
+
+#include <libtransmission/quark.h>
+#include <libtransmission/utils.h>
+#include <libtransmission/variant.h>
+
+#include "CustomVariantType.h"
+#include "Filters.h"
+#include "Prefs.h"
+#include "TrQtInit.h"
+
+#if QT_VERSION < QT_VERSION_CHECK(6, 3, 0)
+#define QCOMPARE_EQ(actual, expected) QCOMPARE(actual, expected)
+#define QCOMPARE_NE(actual, expected) QVERIFY((actual) != (expected))
+#endif
+
+using namespace std::literals;
+
+class PrefsTest : public QObject
+{
+    Q_OBJECT
+
+    [[nodiscard]] static std::string get_json_member_str(int const idx, std::string_view const valstr)
+    {
+        auto const json_key = tr_quark_get_string_view(Prefs::getKey(idx));
+        return fmt::format(R"("{:s}":{:s})", json_key, valstr);
+    }
+
+    static void verify_json_contains(tr_variant const& var, std::string_view const substr)
+    {
+        auto serde = tr_variant_serde::json();
+        serde.compact();
+        auto const str = serde.to_string(var);
+        QVERIFY2(tr_strv_contains(str, substr), str.c_str());
+    }
+
+    static void verify_json_contains(tr_variant const& var, int const idx, std::string_view const val)
+    {
+        auto serde = tr_variant_serde::json();
+        serde.compact();
+        auto const str = serde.to_string(var);
+        auto const substr = get_json_member_str(idx, val);
+        QVERIFY2(tr_strv_contains(str, substr), str.c_str());
+    }
+
+    template<typename T>
+    void verify_get_set_by_property(Prefs& prefs, int const idx, T const& val1, T const& val2)
+    {
+        QCOMPARE_NE(val1, val2);
+
+        prefs.set(idx, val1);
+        QCOMPARE_EQ(prefs.get<T>(idx), val1);
+        QCOMPARE_NE(prefs.get<T>(idx), val2);
+
+        prefs.set(idx, val2);
+        QCOMPARE_NE(prefs.get<T>(idx), val1);
+        QCOMPARE_EQ(prefs.get<T>(idx), val2);
+    }
+
+    template<typename T>
+    void verify_get_by_json(Prefs& prefs, int const idx, T const& val, std::string_view const valstr)
+    {
+        prefs.set(idx, val);
+        QCOMPARE_EQ(prefs.get<T>(idx), val);
+        verify_json_contains(prefs.current_settings(), idx, valstr);
+    }
+
+    template<typename T>
+    void verify_set_by_json(Prefs& prefs, int const idx, T const& val, std::string_view const valstr)
+    {
+        auto const json_object_str = fmt::format(R"({{{:s}}})", get_json_member_str(idx, valstr));
+        auto serde = tr_variant_serde::json();
+        auto const var = serde.parse(json_object_str);
+        QVERIFY(var.has_value());
+        // IDK why clang-tidy doesn't see the QVERIFY check above?
+        // NOLINTNEXTLINE(bugprone-unchecked-optional-access)
+        auto const* const map = var->get_if<tr_variant::Map>();
+        QVERIFY(map != nullptr);
+        prefs.load(*map);
+        QCOMPARE_EQ(prefs.get<T>(idx), val);
+    }
+
+private slots:
+    void handles_bool()
+    {
+        auto constexpr Idx = Prefs::SORT_REVERSED;
+        auto constexpr ValA = false;
+        auto constexpr ValAStr = "false"sv;
+        auto constexpr ValB = true;
+        auto constexpr ValBStr = "true"sv;
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, ValAStr);
+        verify_get_by_json(prefs, Idx, ValB, ValBStr);
+    }
+
+    void handles_int()
+    {
+        auto constexpr Idx = Prefs::MAIN_WINDOW_HEIGHT;
+        auto constexpr ValA = 4242;
+        auto constexpr ValAStr = "4242"sv;
+        auto constexpr ValB = 2323;
+        auto constexpr ValBStr = "2323"sv;
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, ValAStr);
+        verify_get_by_json(prefs, Idx, ValB, ValBStr);
+    }
+
+    void handles_double()
+    {
+        auto constexpr Idx = Prefs::RATIO;
+        auto constexpr ValA = 1.234;
+        auto constexpr ValB = 5.678;
+        auto const val_a_str = fmt::format("{}", ValA);
+        auto const val_b_str = fmt::format("{}", ValB);
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, val_a_str);
+        verify_get_by_json(prefs, Idx, ValB, val_b_str);
+    }
+
+    void handles_qstring()
+    {
+        auto constexpr Idx = Prefs::DOWNLOAD_DIR;
+        auto constexpr ValAStr = R"("/tmp/transmission-test-download-dir")"sv;
+        auto constexpr ValBStr = R"("/tmp/transmission-test-download-dir-b")"sv;
+        auto const val_a = QStringLiteral("/tmp/transmission-test-download-dir");
+        auto const val_b = QStringLiteral("/tmp/transmission-test-download-dir-b");
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, val_a, val_b);
+        verify_set_by_json(prefs, Idx, val_a, ValAStr);
+        verify_get_by_json(prefs, Idx, val_b, ValBStr);
+    }
+
+    void handles_qstringlist()
+    {
+        auto constexpr Idx = Prefs::COMPLETE_SOUND_COMMAND;
+        auto constexpr ValAStr = R"(["one","two","three"])"sv;
+        auto constexpr ValBStr = R"(["alpha","beta"])"sv;
+        auto const val_a = QStringList{ QStringLiteral("one"), QStringLiteral("two"), QStringLiteral("three") };
+        auto const val_b = QStringList{ QStringLiteral("alpha"), QStringLiteral("beta") };
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, val_a, val_b);
+        verify_set_by_json(prefs, Idx, val_a, ValAStr);
+        verify_get_by_json(prefs, Idx, val_b, ValBStr);
+    }
+
+    void handles_qdatetime()
+    {
+        auto constexpr Idx = Prefs::BLOCKLIST_DATE;
+        auto const val_a = QDateTime::fromMSecsSinceEpoch(1700000000000LL).toUTC();
+        auto const val_a_str = fmt::format("{}", val_a.toSecsSinceEpoch());
+        auto const val_b = QDateTime::fromMSecsSinceEpoch(1700000000000LL + 123000LL).toUTC();
+        auto const val_b_str = fmt::format("{}", val_b.toSecsSinceEpoch());
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, val_a, val_b);
+        verify_set_by_json(prefs, Idx, val_a, val_a_str);
+        verify_get_by_json(prefs, Idx, val_b, val_b_str);
+    }
+
+    void handles_sortmode()
+    {
+        auto constexpr Idx = Prefs::SORT_MODE;
+        auto constexpr ValA = SortMode::SortBySize;
+        auto constexpr ValAStr = R"("sort_by_size")"sv;
+        auto constexpr ValB = SortMode::SortByName;
+        auto constexpr ValBStr = R"("sort_by_name")"sv;
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, ValAStr);
+        verify_get_by_json(prefs, Idx, ValB, ValBStr);
+    }
+
+    void handles_showmode()
+    {
+        auto constexpr Idx = Prefs::FILTER_MODE;
+        auto constexpr ValA = ShowMode::ShowAll;
+        auto constexpr ValAStr = R"("show_all")"sv;
+        auto constexpr ValB = ShowMode::ShowActive;
+        auto constexpr ValBStr = R"("show_active")"sv;
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, ValAStr);
+        verify_get_by_json(prefs, Idx, ValB, ValBStr);
+    }
+
+    void handles_encryptionmode()
+    {
+        auto constexpr Idx = Prefs::ENCRYPTION;
+        auto constexpr ValA = TR_ENCRYPTION_REQUIRED;
+        auto constexpr ValAStr = R"("required")"sv;
+        auto constexpr ValB = TR_ENCRYPTION_PREFERRED;
+        auto constexpr ValBStr = R"("preferred")"sv;
+
+        auto prefs = Prefs{};
+        verify_get_set_by_property(prefs, Idx, ValA, ValB);
+        verify_set_by_json(prefs, Idx, ValA, ValAStr);
+        verify_get_by_json(prefs, Idx, ValB, ValBStr);
+    }
+
+    // ---
+
+    static void changed_signal_emits_when_change()
+    {
+        static auto constexpr Idx = Prefs::SORT_REVERSED;
+
+        auto prefs = Prefs{};
+        auto const spy = QSignalSpy{ &prefs, &Prefs::changed };
+
+        auto const old_value = prefs.get<bool>(Idx);
+        auto const new_value = !old_value;
+        prefs.set(Idx, new_value);
+        QCOMPARE(spy.count(), 1);
+        auto const& signal_args = spy.first();
+        QCOMPARE(signal_args.at(0).toInt(), Idx);
+    }
+
+    static void changed_signal_does_not_emit_when_unchanged()
+    {
+        static auto constexpr Idx = Prefs::SORT_REVERSED;
+
+        auto prefs = Prefs{};
+        auto const spy = QSignalSpy{ &prefs, &Prefs::changed };
+
+        auto const current_value = prefs.get<bool>(Idx);
+        prefs.set(Idx, current_value);
+        QCOMPARE(spy.count(), 0);
+    }
+};
+
+int main(int argc, char** argv)
+{
+    trqt::trqt_init();
+    auto const app = QApplication{ argc, argv };
+    auto test = PrefsTest{};
+    return QTest::qExec(&test, argc, argv);
+}
+
+#include "prefs-test.moc"