diff --git a/main.h b/main.h
--- a/main.h
+++ b/main.h
@@ -238,7 +238,6 @@
     }
 
 protected:
-    QString m_originalSessionKey;
     static int crashes;
 
 private Q_SLOTS:
diff --git a/main.cpp b/main.cpp
--- a/main.cpp
+++ b/main.cpp
@@ -276,7 +276,7 @@
     // critical startup section where x errors cause kwin to abort.
 
     // create workspace.
-    (void) new Workspace(m_originalSessionKey);
+    (void) new Workspace();
     emit workspaceCreated();
 }
 
diff --git a/main_x11.cpp b/main_x11.cpp
--- a/main_x11.cpp
+++ b/main_x11.cpp
@@ -216,11 +216,6 @@
         Application::setX11ScreenNumber(QX11Info::appScreen());
     }
 
-    // QSessionManager for some reason triggers a very early commitDataRequest
-    // and updates the key - before we create the workspace and load the session
-    // data -> store and pass to the workspace constructor
-    m_originalSessionKey = sessionKey();
-
     owner.reset(new KWinSelectionOwner(Application::x11ScreenNumber()));
     connect(owner.data(), &KSelectionOwner::failedToClaimOwnership, []{
         fputs(i18n("kwin: unable to claim manager selection, another wm running? (try using --replace)\n").toLocal8Bit().constData(), stderr);
@@ -420,6 +415,8 @@
     qunsetenv("QT_DEVICE_PIXEL_RATIO");
     qunsetenv("QT_SCALE_FACTOR");
     QCoreApplication::setAttribute(Qt::AA_DisableHighDpiScaling);
+    // KSMServer talks to us directly on DBus.
+    QCoreApplication::setAttribute(Qt::AA_DisableSessionManager);
 
     KWin::ApplicationX11 a(argc, argv);
     a.setupTranslator();
diff --git a/org.kde.KWin.Session.xml b/org.kde.KWin.Session.xml
--- a/org.kde.KWin.Session.xml
+++ b/org.kde.KWin.Session.xml
@@ -10,6 +10,15 @@
             -->
          <arg name="state" type="u" direction="in" />
       </method>
+      <method name="loadSession">
+          <arg name="name" type="s" direction="in" />
+      </method>
+      <method name="aboutToSaveSession">
+          <arg name="name" type="s" direction="in" />
+      </method>
+      <method name="finishSaveSession">
+          <arg name="name" type="s" direction="in" />
+      </method>
    </interface>
 </node>
 
diff --git a/sm.h b/sm.h
--- a/sm.h
+++ b/sm.h
@@ -45,8 +45,15 @@
 Q_SIGNALS:
     void stateChanged();
 
+    void loadSessionRequested(const QString &name);
+    void prepareSessionSaveRequested(const QString &name);
+    void finishSessionSaveRequested(const QString &name);
+
 public Q_SLOTS: // DBus API
     void setState(uint state);
+    void loadSession(const QString &name);
+    void aboutToSaveSession(const QString &name);
+    void finishSaveSession(const QString &name);
 
 private:
     void setState(SessionState state);
diff --git a/sm.cpp b/sm.cpp
--- a/sm.cpp
+++ b/sm.cpp
@@ -81,46 +81,16 @@
     return static_cast< NET::WindowType >(-2);   // undefined
 }
 
-void Workspace::saveState(QSessionManager &sm)
-{
-    bool sessionManagerIsKSMServer = QDBusConnection::sessionBus().interface()->isServiceRegistered("org.kde.ksmserver").value();
-
-    // If the session manager is ksmserver, save stacking
-    // order, active window, active desktop etc. in phase 1,
-    // as ksmserver assures no interaction will be done
-    // before the WM finishes phase 1. Saving in phase 2 is
-    // too late, as possible user interaction may change some things.
-    // Phase2 is still needed though (ICCCM 5.2)
-    KConfig *config = sessionConfig(sm.sessionId(), sm.sessionKey());
-    if (!sm.isPhase2()) {
-        KConfigGroup cg(config, "Session");
-        cg.writeEntry("AllowsInteraction", sm.allowsInteraction());
-        if (sessionManagerIsKSMServer)   // save stacking order etc. before "save file?" etc. dialogs change it
-            storeSession(config, SMSavePhase0);
-        config->markAsClean(); // don't write Phase #1 data to disk
-        sm.release(); // Qt doesn't automatically release in this case (bug?)
-        sm.requestPhase2();
-        return;
-    }
-    storeSession(config, sessionManagerIsKSMServer ? SMSavePhase2 : SMSavePhase2Full);
-    config->sync();
-
-    // inform the smserver on how to clean-up after us
-    const QString localFilePath = QStandardPaths::writableLocation(QStandardPaths::GenericConfigLocation) + QLatin1Char('/') + config->name();
-    if (QFile::exists(localFilePath)) { // expectable for the sync
-        sm.setDiscardCommand(QStringList() << QStringLiteral("rm") << localFilePath);
-    }
-}
-
-// Workspace
-
 /**
  * Stores the current session in the config file
  *
  * @see loadSessionInfo
  */
-void Workspace::storeSession(KConfig* config, SMSavePhase phase)
+void Workspace::storeSession(const QString &sessionName, SMSavePhase phase)
 {
+    qCDebug(KWIN_CORE) << "storing session" << sessionName << "in phase" << phase;
+    KConfig *config = sessionConfig(sessionName, QString());
+
     KConfigGroup cg(config, "Session");
     int count =  0;
     int active_client = -1;
@@ -160,6 +130,7 @@
         cg.writeEntry("active", session_active_client);
         cg.writeEntry("desktop", VirtualDesktopManager::self()->current());
     }
+    config->sync(); // it previously did some "revert to defaults" stuff for phase1 I think
 }
 
 void Workspace::storeClient(KConfigGroup &cg, int num, X11Client *c)
@@ -235,12 +206,10 @@
  *
  * @see storeSession
  */
-void Workspace::loadSessionInfo(const QString &key)
+void Workspace::loadSessionInfo(const QString &sessionName)
 {
-    // NOTICE: qApp->sessionKey() is outdated when this gets invoked
-    // the key parameter is cached from the application constructor.
     session.clear();
-    KConfigGroup cg(sessionConfig(qApp->sessionId(), key), "Session");
+    KConfigGroup cg(sessionConfig(sessionName, QString()), "Session");
     addSessionInfo(cg);
 }
 
@@ -385,6 +354,7 @@
     }
 }
 
+// TODO should we rethink this now that we have dedicated start end end save methods?
 void SessionManager::setState(SessionState state)
 {
     if (state == m_sessionState) {
@@ -405,5 +375,20 @@
     emit stateChanged();
 }
 
+void SessionManager::loadSession(const QString &name)
+{
+    emit loadSessionRequested(name);
+}
+
+void SessionManager::aboutToSaveSession(const QString &name)
+{
+    emit prepareSessionSaveRequested(name);
+}
+
+void SessionManager::finishSaveSession(const QString &name)
+{
+    emit finishSessionSaveRequested(name);
+}
+
 } // namespace
 
diff --git a/workspace.h b/workspace.h
--- a/workspace.h
+++ b/workspace.h
@@ -69,7 +69,7 @@
 {
     Q_OBJECT
 public:
-    explicit Workspace(const QString &sessionKey = QString());
+    explicit Workspace();
     ~Workspace() override;
 
     static Workspace* self() {
@@ -309,7 +309,7 @@
     void updateOnAllDesktopsOfTransients(AbstractClient*);
     void checkTransients(xcb_window_t w);
 
-    void storeSession(KConfig* config, SMSavePhase phase);
+    void storeSession(const QString &sessionName, SMSavePhase phase);
     void storeClient(KConfigGroup &cg, int num, X11Client *c);
     void storeSubSession(const QString &name, QSet<QByteArray> sessionIds);
     void loadSubSessionInfo(const QString &name);
@@ -494,9 +494,6 @@
     void slotDesktopCountChanged(uint previousCount, uint newCount);
     void slotCurrentDesktopChanged(uint oldDesktop, uint newDesktop);
 
-    // session management
-    void saveState(QSessionManager &sm);
-
 Q_SIGNALS:
     /**
      * Emitted after the Workspace has setup the complete initialization process.
@@ -581,7 +578,7 @@
     AbstractClient* active_popup_client;
 
     int m_initialDesktop;
-    void loadSessionInfo(const QString &key);
+    void loadSessionInfo(const QString &sessionName);
     void addSessionInfo(KConfigGroup &cg);
 
     QList<SessionInfo*> session;
diff --git a/workspace.cpp b/workspace.cpp
--- a/workspace.cpp
+++ b/workspace.cpp
@@ -102,7 +102,7 @@
 
 Workspace* Workspace::_self = nullptr;
 
-Workspace::Workspace(const QString &sessionKey)
+Workspace::Workspace()
     : QObject(nullptr)
     , m_compositor(nullptr)
     // Unsorted
@@ -153,10 +153,6 @@
 
     delayFocusTimer = nullptr;
 
-    if (!sessionKey.isEmpty())
-        loadSessionInfo(sessionKey);
-    connect(qApp, &QGuiApplication::saveStateRequest, this, &Workspace::saveState);
-
     RuleBook::create(this)->load();
 
     kwinApp()->createScreens();
@@ -187,6 +183,15 @@
     decorationBridge->init();
     connect(this, &Workspace::configChanged, decorationBridge, &Decoration::DecorationBridge::reconfigure);
 
+    connect(m_sessionManager, &SessionManager::loadSessionRequested, this, &Workspace::loadSessionInfo);
+
+    connect(m_sessionManager, &SessionManager::prepareSessionSaveRequested, this, [this](const QString &name) {
+        storeSession(name, SMSavePhase0);
+    });
+    connect(m_sessionManager, &SessionManager::finishSessionSaveRequested, this, [this](const QString &name) {
+        storeSession(name, SMSavePhase2);
+    });
+
     new DBusInterface(this);
 
     Outline::create(this);