diff --git a/__test__/features/user/HandleLogin.test.tsx b/__test__/features/user/HandleLogin.test.tsx
index 5e043de..b55e46b 100644
--- a/__test__/features/user/HandleLogin.test.tsx
+++ b/__test__/features/user/HandleLogin.test.tsx
@@ -1,10 +1,12 @@
 import * as appHooks from "@/app/hooks";
-import { AppDispatch } from "@/app/store";
+import { AppDispatch, setupStore } from "@/app/store";
 import HandleLogin from "@/features/User/HandleLogin";
 import * as oidcAuth from "@/features/User/oidcAuth";
 import { clientConfig } from "@/features/User/oidcAuth";
+import { useInitializeApp } from "@/features/User/useInitializeApp";
 import * as apiUtils from "@/utils/apiUtils";
-import { screen, waitFor } from "@testing-library/react";
+import { renderHook, screen, waitFor } from "@testing-library/react";
+import { Provider } from "react-redux";
 import { push } from "redux-first-history";
 import { renderWithProviders } from "../../utils/Renderwithproviders";
 
@@ -17,6 +19,17 @@ describe("HandleLogin", () => {
     const dispatch = jest.fn() as AppDispatch;
     jest.spyOn(appHooks, "useAppDispatch").mockReturnValue(dispatch);
     sessionStorage.clear();
+    Object.defineProperty(window, "matchMedia", {
+      writable: true,
+      value: jest.fn().mockImplementation((query) => ({
+        matches: false,
+        media: query,
+        onchange: null,
+        addEventListener: jest.fn(),
+        removeEventListener: jest.fn(),
+        dispatchEvent: jest.fn(),
+      })),
+    });
   });
 
   test("redirects and sets sessionStorage when no userData", async () => {
@@ -28,18 +41,23 @@ describe("HandleLogin", () => {
 
     jest.spyOn(oidcAuth, "Auth").mockResolvedValue(loginUrlMock);
 
-    renderWithProviders(<HandleLogin />, {
-      user: {
-        userData: null,
-        tokens: null,
-        loading: false,
-        error: null,
-      },
-      calendars: {
-        list: {},
-        pending: false,
-        error: null,
-      },
+    const { result } = renderHook(() => useInitializeApp(), {
+      wrapper: ({ children }) => (
+        <Provider
+          store={setupStore({
+            user: {
+              userData: null,
+              tokens: null,
+              loading: false,
+              error: null,
+              coreConfig: { language: "en" },
+            },
+            calendars: { list: {}, pending: false, error: null },
+          })}
+        >
+          {children}
+        </Provider>
+      ),
     });
 
     await waitFor(
diff --git a/src/App.tsx b/src/App.tsx
index e19b71f..b0ad299 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -13,6 +13,7 @@ import { Loading } from "./components/Loading/Loading";
 import { AVAILABLE_LANGUAGES } from "./features/Settings/constants";
 import HandleLogin from "./features/User/HandleLogin";
 import { CallbackResume } from "./features/User/LoginCallback";
+import { useInitializeApp } from "./features/User/useInitializeApp";
 import { ScreenTooSmall } from "./ScreenTooSmall";
 import { WebSocketGate } from "./websocket/WebSocketGate";
 
@@ -68,6 +69,8 @@ function App() {
     () => window.matchMedia(SMALL_SCREEN_QUERY).matches
   );
 
+  useInitializeApp();
+
   useEffect(() => {
     const mediaQuery = window.matchMedia(SMALL_SCREEN_QUERY);
     const onChange = (event: MediaQueryListEvent) =>
diff --git a/src/features/Calendars/CalendarSlice.ts b/src/features/Calendars/CalendarSlice.ts
index 27cd547..79cdcfe 100644
--- a/src/features/Calendars/CalendarSlice.ts
+++ b/src/features/Calendars/CalendarSlice.ts
@@ -126,10 +126,25 @@ const CalendarSlice = createSlice({
           }>
         ) => {
           state.pending = false;
-          state.list = action.payload.importedCalendars;
           state.error = action.payload.errors.length
             ? action.payload.errors
             : null;
+
+          Object.entries(action.payload.importedCalendars).forEach(
+            ([id, cal]) => {
+              state.list[id] = {
+                ...cal,
+                events: state.list[id]?.events || {},
+              };
+            }
+          );
+
+          // Remove calendars that no longer exist
+          Object.keys(state.list).forEach((id) => {
+            if (!action.payload.importedCalendars[id]) {
+              delete state.list[id];
+            }
+          });
         }
       )
       .addCase(
diff --git a/src/features/User/HandleLogin.tsx b/src/features/User/HandleLogin.tsx
index e24160e..b8675ec 100644
--- a/src/features/User/HandleLogin.tsx
+++ b/src/features/User/HandleLogin.tsx
@@ -1,60 +1,14 @@
 import { useAppDispatch, useAppSelector } from "@/app/hooks";
-import { redirectTo } from "@/utils/apiUtils";
 import { useEffect, useRef } from "react";
 import { push } from "redux-first-history";
-import { getCalendarsListAsync } from "../Calendars/services";
-import { Auth } from "./oidcAuth";
-import { getOpenPaasUserDataAsync, setTokens, setUserData } from "./userSlice";
 import { setAppLoading } from "@/app/loadingSlice";
 
 export function HandleLogin() {
   const userData = useAppSelector((state) => state.user);
   const calendars = useAppSelector((state) => state.calendars);
   const dispatch = useAppDispatch();
-  const hasInitiatedRef = useRef(false);
   const hasNavigatedRef = useRef(false);
 
-  // Initiate login or load saved data
-  useEffect(() => {
-    if (hasInitiatedRef.current) return;
-    if (userData.userData && !calendars.pending) return;
-
-    hasInitiatedRef.current = true;
-
-    const initiateLogin = async () => {
-      const savedToken = sessionStorage.getItem("tokenSet")
-        ? JSON.parse(sessionStorage.getItem("tokenSet")!)
-        : null;
-      const savedUser = sessionStorage.getItem("userData")
-        ? JSON.parse(sessionStorage.getItem("userData")!)
-        : null;
-
-      if (savedToken && savedUser) {
-        dispatch(setAppLoading(true));
-        dispatch(setTokens(savedToken));
-        dispatch(setUserData(savedUser));
-        await dispatch(getOpenPaasUserDataAsync());
-        await dispatch(getCalendarsListAsync());
-        return;
-      }
-
-      const loginurl = await Auth();
-
-      sessionStorage.setItem(
-        "redirectState",
-        JSON.stringify({
-          code_verifier: loginurl.code_verifier,
-          state: loginurl.state,
-        })
-      );
-
-      redirectTo(loginurl.redirectTo);
-    };
-
-    initiateLogin();
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [userData.userData, calendars.list, dispatch]);
-
   // Navigate to /calendar only when all data is ready
   useEffect(() => {
     if (hasNavigatedRef.current) return;
diff --git a/src/features/User/useInitializeApp.ts b/src/features/User/useInitializeApp.ts
new file mode 100644
index 0000000..2397624
--- /dev/null
+++ b/src/features/User/useInitializeApp.ts
@@ -0,0 +1,61 @@
+import { useAppDispatch, useAppSelector } from "@/app/hooks";
+import { setAppLoading } from "@/app/loadingSlice";
+import { getCalendarsListAsync } from "@/features/Calendars/services";
+import { Auth } from "@/features/User/oidcAuth";
+import {
+  getOpenPaasUserDataAsync,
+  setTokens,
+  setUserData,
+} from "@/features/User/userSlice";
+import { redirectTo } from "@/utils/apiUtils";
+import { useEffect, useRef } from "react";
+
+export function useInitializeApp() {
+  const userData = useAppSelector((state) => state.user);
+  const calendars = useAppSelector((state) => state.calendars);
+  const dispatch = useAppDispatch();
+  const hasInitiatedRef = useRef(false);
+
+  useEffect(() => {
+    if (hasInitiatedRef.current) return;
+    if (userData.userData && !calendars.pending) return;
+    if (window.location.pathname === "/callback") return;
+    hasInitiatedRef.current = true;
+
+    const initiateLogin = async () => {
+      const savedToken = sessionStorage.getItem("tokenSet")
+        ? JSON.parse(sessionStorage.getItem("tokenSet")!)
+        : null;
+      const savedUser = sessionStorage.getItem("userData")
+        ? JSON.parse(sessionStorage.getItem("userData")!)
+        : null;
+
+      if (savedToken && savedUser) {
+        dispatch(setAppLoading(true));
+        dispatch(setTokens(savedToken));
+        dispatch(setUserData(savedUser));
+        try {
+          await dispatch(getOpenPaasUserDataAsync());
+          await dispatch(getCalendarsListAsync());
+        } finally {
+          dispatch(setAppLoading(false));
+        }
+
+        return;
+      }
+
+      const loginurl = await Auth();
+      sessionStorage.setItem(
+        "redirectState",
+        JSON.stringify({
+          code_verifier: loginurl.code_verifier,
+          state: loginurl.state,
+        })
+      );
+      redirectTo(loginurl.redirectTo);
+    };
+
+    initiateLogin();
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [userData.userData]);
+}