diff --git a/client/src/actions/core.js b/client/src/actions/core.js
index 85182ffd..2ae879ba 100644
--- a/client/src/actions/core.js
+++ b/client/src/actions/core.js
@@ -98,10 +98,24 @@ logout.revokeAccessToken = () => ({
   payload: {},
 });
 
+const showAutoLogoutWarning = (expiresAt) => ({
+  type: ActionTypes.AUTO_LOGOUT_WARNING_SHOW,
+  payload: {
+    expiresAt,
+  },
+});
+
+const dismissAutoLogoutWarning = () => ({
+  type: ActionTypes.AUTO_LOGOUT_WARNING_DISMISS,
+  payload: {},
+});
+
 export default {
   initializeCore,
   toggleFavorites,
   toggleEditMode,
   updateHomeView,
   logout,
+  showAutoLogoutWarning,
+  dismissAutoLogoutWarning,
 };
diff --git a/client/src/components/common/AutoLogoutWarningModal/AutoLogoutWarningModal.jsx b/client/src/components/common/AutoLogoutWarningModal/AutoLogoutWarningModal.jsx
new file mode 100644
index 00000000..a9807cd7
--- /dev/null
+++ b/client/src/components/common/AutoLogoutWarningModal/AutoLogoutWarningModal.jsx
@@ -0,0 +1,71 @@
+/*!
+ * Copyright (c) 2024 PLANKA Software GmbH
+ * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
+ */
+
+import React, { useCallback, useEffect, useState } from 'react';
+import { useDispatch, useSelector } from 'react-redux';
+import { useTranslation } from 'react-i18next';
+import { Button, Modal } from 'semantic-ui-react';
+
+import selectors from '../../../selectors';
+import entryActions from '../../../entry-actions';
+
+const AutoLogoutWarningModal = React.memo(() => {
+  const warning = useSelector(selectors.selectAutoLogoutWarning);
+  const dispatch = useDispatch();
+  const [t] = useTranslation();
+
+  const computeRemaining = useCallback(
+    () => (warning ? Math.max(0, Math.ceil((warning.expiresAt - Date.now()) / 1000)) : 0),
+    [warning],
+  );
+
+  const [remainingSeconds, setRemainingSeconds] = useState(computeRemaining);
+
+  useEffect(() => {
+    if (!warning) {
+      return undefined;
+    }
+
+    setRemainingSeconds(computeRemaining());
+
+    const interval = setInterval(() => {
+      setRemainingSeconds(computeRemaining());
+    }, 500);
+
+    return () => clearInterval(interval);
+  }, [warning, computeRemaining]);
+
+  const handleStayClick = useCallback(() => {
+    dispatch(entryActions.dismissAutoLogoutWarning());
+  }, [dispatch]);
+
+  const handleLogoutClick = useCallback(() => {
+    dispatch(entryActions.logout());
+  }, [dispatch]);
+
+  if (!warning) {
+    return null;
+  }
+
+  return (
+    <Modal open size="tiny" centered closeOnDimmerClick={false} closeOnEscape={false}>
+      <Modal.Header>{t('common.autoLogoutWarning_title')}</Modal.Header>
+      <Modal.Content>
+        <p>{t('common.autoLogoutWarning_body', { seconds: remainingSeconds })}</p>
+      </Modal.Content>
+      <Modal.Actions>
+        <Button onClick={handleLogoutClick}>{t('action.logOutNow')}</Button>
+        <Button
+          positive
+          content={t('action.stayLoggedIn')}
+          icon="checkmark"
+          onClick={handleStayClick}
+        />
+      </Modal.Actions>
+    </Modal>
+  );
+});
+
+export default AutoLogoutWarningModal;
diff --git a/client/src/components/common/AutoLogoutWarningModal/index.js b/client/src/components/common/AutoLogoutWarningModal/index.js
new file mode 100644
index 00000000..3064789e
--- /dev/null
+++ b/client/src/components/common/AutoLogoutWarningModal/index.js
@@ -0,0 +1,8 @@
+/*!
+ * Copyright (c) 2024 PLANKA Software GmbH
+ * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
+ */
+
+import AutoLogoutWarningModal from './AutoLogoutWarningModal';
+
+export default AutoLogoutWarningModal;
diff --git a/client/src/components/common/Core/Core.jsx b/client/src/components/common/Core/Core.jsx
index 3bc81e7b..2cb7f7af 100644
--- a/client/src/components/common/Core/Core.jsx
+++ b/client/src/components/common/Core/Core.jsx
@@ -17,6 +17,7 @@ import Fixed from '../Fixed';
 import Static from '../Static';
 import AdministrationModal from '../AdministrationModal';
 import AboutModal from '../AboutModal';
+import AutoLogoutWarningModal from '../AutoLogoutWarningModal';
 import UserSettingsModal from '../../users/UserSettingsModal';
 import ProjectBackground from '../../projects/ProjectBackground';
 import AddProjectModal from '../../projects/AddProjectModal';
@@ -122,6 +123,7 @@ const Core = React.memo(() => {
           <Fixed />
           <Static />
           {modalNode}
+          <AutoLogoutWarningModal />
         </>
       )}
       {messageNode}
diff --git a/client/src/components/users/UserSettingsModal/PreferencesPane.jsx b/client/src/components/users/UserSettingsModal/PreferencesPane.jsx
index 984c831c..99492fce 100644
--- a/client/src/components/users/UserSettingsModal/PreferencesPane.jsx
+++ b/client/src/components/users/UserSettingsModal/PreferencesPane.jsx
@@ -3,16 +3,35 @@
  * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
  */
 
-import React, { useCallback } from 'react';
+import React, { useCallback, useMemo } from 'react';
 import { useDispatch, useSelector } from 'react-redux';
 import { useTranslation } from 'react-i18next';
-import { Radio, Tab } from 'semantic-ui-react';
+import { Dropdown, Radio, Tab } from 'semantic-ui-react';
 
 import selectors from '../../../selectors';
 import entryActions from '../../../entry-actions';
+import { AutoLogoutModes } from '../../../constants/Enums';
 
 import styles from './PreferencesPane.module.scss';
 
+const AUTO_LOGOUT_OPTION_ORDER = [
+  AutoLogoutModes.MINUTES_2,
+  AutoLogoutModes.MINUTES_5,
+  AutoLogoutModes.MINUTES_10,
+  AutoLogoutModes.MINUTES_30,
+  AutoLogoutModes.HOURS_12,
+  AutoLogoutModes.NEVER,
+];
+
+const AUTO_LOGOUT_TRANSLATION_KEYS = {
+  [AutoLogoutModes.NEVER]: 'common.autoLogout_never',
+  [AutoLogoutModes.MINUTES_2]: 'common.autoLogout_2m',
+  [AutoLogoutModes.MINUTES_5]: 'common.autoLogout_5m',
+  [AutoLogoutModes.MINUTES_10]: 'common.autoLogout_10m',
+  [AutoLogoutModes.MINUTES_30]: 'common.autoLogout_30m',
+  [AutoLogoutModes.HOURS_12]: 'common.autoLogout_12h',
+};
+
 const PreferencesPane = React.memo(() => {
   const user = useSelector(selectors.selectCurrentUser);
 
@@ -30,6 +49,29 @@ const PreferencesPane = React.memo(() => {
     [dispatch],
   );
 
+  const handleAutoLogoutChange = useCallback(
+    (_, { value }) => {
+      dispatch(
+        entryActions.updateCurrentUser({
+          autoLogoutMode: value,
+        }),
+      );
+    },
+    [dispatch],
+  );
+
+  const autoLogoutOptions = useMemo(
+    () =>
+      AUTO_LOGOUT_OPTION_ORDER.map((mode) => ({
+        key: mode,
+        value: mode,
+        text: t(AUTO_LOGOUT_TRANSLATION_KEYS[mode]),
+      })),
+    [t],
+  );
+
+  const autoLogoutValue = user.autoLogoutMode || AutoLogoutModes.MINUTES_30;
+
   return (
     <Tab.Pane attached={false} className={styles.wrapper}>
       <Radio
@@ -56,6 +98,17 @@ const PreferencesPane = React.memo(() => {
         className={styles.radio}
         onChange={handleChange}
       />
+      <div className={styles.field}>
+        <span className={styles.label}>{t('common.autoLogout')}</span>
+        <Dropdown
+          fluid
+          selection
+          className={styles.dropdown}
+          options={autoLogoutOptions}
+          value={autoLogoutValue}
+          onChange={handleAutoLogoutChange}
+        />
+      </div>
     </Tab.Pane>
   );
 });
diff --git a/client/src/components/users/UserSettingsModal/PreferencesPane.module.scss b/client/src/components/users/UserSettingsModal/PreferencesPane.module.scss
index 6822ea1d..25317926 100644
--- a/client/src/components/users/UserSettingsModal/PreferencesPane.module.scss
+++ b/client/src/components/users/UserSettingsModal/PreferencesPane.module.scss
@@ -13,6 +13,22 @@
     }
   }
 
+  .field {
+    margin-top: 16px;
+  }
+
+  .label {
+    color: #444444;
+    display: block;
+    font-size: 13px;
+    font-weight: 600;
+    margin-bottom: 6px;
+  }
+
+  .dropdown {
+    width: 100%;
+  }
+
   .wrapper {
     border: none;
     box-shadow: none;
diff --git a/client/src/constants/ActionTypes.js b/client/src/constants/ActionTypes.js
index 7783d938..7d79589c 100644
--- a/client/src/constants/ActionTypes.js
+++ b/client/src/constants/ActionTypes.js
@@ -55,6 +55,8 @@ export default {
 
   /* Modals */
 
+  AUTO_LOGOUT_WARNING_SHOW: 'AUTO_LOGOUT_WARNING_SHOW',
+  AUTO_LOGOUT_WARNING_DISMISS: 'AUTO_LOGOUT_WARNING_DISMISS',
   MODAL_OPEN: 'MODAL_OPEN',
   MODAL_CLOSE: 'MODAL_CLOSE',
 
diff --git a/client/src/constants/EntryActionTypes.js b/client/src/constants/EntryActionTypes.js
index ad5c0d1d..78348de5 100755
--- a/client/src/constants/EntryActionTypes.js
+++ b/client/src/constants/EntryActionTypes.js
@@ -36,6 +36,7 @@ export default {
 
   /* Modals */
 
+  AUTO_LOGOUT_WARNING_DISMISS: `${PREFIX}/AUTO_LOGOUT_WARNING_DISMISS`,
   MODAL_OPEN: `${PREFIX}/MODAL_OPEN`,
   MODAL_CLOSE: `${PREFIX}/MODAL_CLOSE`,
 
diff --git a/client/src/constants/Enums.js b/client/src/constants/Enums.js
index 3de0090e..e0dc2713 100755
--- a/client/src/constants/Enums.js
+++ b/client/src/constants/Enums.js
@@ -13,6 +13,15 @@ export const EditorModes = {
   MARKUP: 'markup',
 };
 
+export const AutoLogoutModes = {
+  NEVER: 'never',
+  MINUTES_2: '2m',
+  MINUTES_5: '5m',
+  MINUTES_10: '10m',
+  MINUTES_30: '30m',
+  HOURS_12: '12h',
+};
+
 export const HomeViews = {
   GRID_PROJECTS: 'gridProjects',
   GROUPED_PROJECTS: 'groupedProjects',
diff --git a/client/src/entry-actions/core.js b/client/src/entry-actions/core.js
index 62b7de3c..076f7799 100644
--- a/client/src/entry-actions/core.js
+++ b/client/src/entry-actions/core.js
@@ -33,9 +33,15 @@ const logout = (revokeAccessToken = true) => ({
   },
 });
 
+const dismissAutoLogoutWarning = () => ({
+  type: EntryActionTypes.AUTO_LOGOUT_WARNING_DISMISS,
+  payload: {},
+});
+
 export default {
   toggleFavorites,
   toggleEditMode,
   updateHomeView,
   logout,
+  dismissAutoLogoutWarning,
 };
diff --git a/client/src/locales/de-DE/core.js b/client/src/locales/de-DE/core.js
index 6cb4d1c4..34a57673 100644
--- a/client/src/locales/de-DE/core.js
+++ b/client/src/locales/de-DE/core.js
@@ -106,6 +106,15 @@ export default {
       attachment: 'Anhang',
       attachments: 'Anhänge',
       authentication: 'Authentifizierung',
+      autoLogout: 'Automatisches Ausloggen',
+      autoLogout_10m: 'Nach 10 Minuten',
+      autoLogout_12h: 'Nach 12 Stunden',
+      autoLogout_2m: 'Nach 2 Minuten',
+      autoLogout_30m: 'Nach 30 Minuten',
+      autoLogout_5m: 'Nach 5 Minuten',
+      autoLogout_never: 'Nie',
+      autoLogoutWarning_body: 'Sie werden in {{seconds}}s aufgrund von Inaktivität ausgeloggt.',
+      autoLogoutWarning_title: 'Sie werden bald ausgeloggt',
       background: 'Hintergrund',
       baseCustomFields_title: 'Feldgruppe',
       baseGroup: 'Feldgruppe',
@@ -540,6 +549,7 @@ export default {
       leaveBoard: 'Arbeitsbereich verlassen',
       leaveProject: 'Projekt verlassen',
       logOut_title: 'Ausloggen',
+      logOutNow: 'Jetzt abmelden',
       makeCover_title: 'Als Vorschau festlegen',
       makeProjectPrivate: 'Projekt privat machen',
       makeProjectPrivate_title: 'Projekt privat machen',
@@ -574,6 +584,7 @@ export default {
       showMore: 'Mehr anzeigen',
       sortList_title: 'Liste sortieren',
       start: 'Start',
+      stayLoggedIn: 'Angemeldet bleiben',
       stop: 'Stopp',
       subscribe: 'Abonnieren',
       unsubscribe: 'De-abonnieren',
diff --git a/client/src/locales/en-US/core.js b/client/src/locales/en-US/core.js
index 250ba4ab..1ac9a4ed 100644
--- a/client/src/locales/en-US/core.js
+++ b/client/src/locales/en-US/core.js
@@ -88,6 +88,15 @@ export default {
       attachment: 'Attachment',
       attachments: 'Attachments',
       authentication: 'Authentication',
+      autoLogout: 'Auto logout',
+      autoLogout_10m: 'After 10 minutes',
+      autoLogout_12h: 'After 12 hours',
+      autoLogout_2m: 'After 2 minutes',
+      autoLogout_30m: 'After 30 minutes',
+      autoLogout_5m: 'After 5 minutes',
+      autoLogout_never: 'Never',
+      autoLogoutWarning_body: 'You will be logged out in {{seconds}}s due to inactivity.',
+      autoLogoutWarning_title: 'You will be logged out soon',
       background: 'Background',
       baseCustomFields_title: 'Base Custom Fields',
       baseGroup: 'Base group',
@@ -514,6 +523,7 @@ export default {
       leaveBoard: 'Leave board',
       leaveProject: 'Leave project',
       logOut_title: 'Log Out',
+      logOutNow: 'Log out now',
       makeCover_title: 'Make Cover',
       makeProjectPrivate: 'Make project private',
       makeProjectPrivate_title: 'Make Project Private',
@@ -548,6 +558,7 @@ export default {
       showMore: 'Show more',
       sortList_title: 'Sort List',
       start: 'Start',
+      stayLoggedIn: 'Stay logged in',
       stop: 'Stop',
       subscribe: 'Subscribe',
       unsubscribe: 'Unsubscribe',
diff --git a/client/src/models/User.js b/client/src/models/User.js
index f4d4b913..4567d460 100755
--- a/client/src/models/User.js
+++ b/client/src/models/User.js
@@ -89,6 +89,7 @@ export default class extends BaseModel {
     subscribeToCardWhenCommenting: attr(),
     turnOffRecentCardHighlighting: attr(),
     isDefaultAdmin: attr(),
+    autoLogoutMode: attr(),
     isTotpEnabled: attr(),
     totpEnabledAt: attr(),
     totpRecoveryCodesRemaining: attr(),
diff --git a/client/src/reducers/core.js b/client/src/reducers/core.js
index 0a4e94a5..defa88ef 100755
--- a/client/src/reducers/core.js
+++ b/client/src/reducers/core.js
@@ -26,6 +26,7 @@ const initialState = {
   projectsSearch: '',
   projectsOrder: ProjectOrders.BY_DEFAULT,
   isHiddenProjectsVisible: false, // TODO: refactor?
+  autoLogoutWarning: null,
 };
 
 // eslint-disable-next-line default-param-last
@@ -117,6 +118,18 @@ export default (state = initialState, { type, payload }) => {
         ...state,
         isLogouting: true,
       };
+    case ActionTypes.AUTO_LOGOUT_WARNING_SHOW:
+      return {
+        ...state,
+        autoLogoutWarning: {
+          expiresAt: payload.expiresAt,
+        },
+      };
+    case ActionTypes.AUTO_LOGOUT_WARNING_DISMISS:
+      return {
+        ...state,
+        autoLogoutWarning: null,
+      };
     case ActionTypes.MODAL_OPEN:
       return {
         ...state,
diff --git a/client/src/sagas/core/index.js b/client/src/sagas/core/index.js
index ba536880..9c5a14d7 100755
--- a/client/src/sagas/core/index.js
+++ b/client/src/sagas/core/index.js
@@ -17,6 +17,7 @@ export default function* coreSaga() {
 
   yield apply(socket, socket.connect);
   yield fork(services.initializeCore);
+  yield fork(services.autoLogout);
 
   yield take(ActionTypes.LOGOUT);
 
diff --git a/client/src/sagas/core/services/auto-logout.js b/client/src/sagas/core/services/auto-logout.js
new file mode 100644
index 00000000..bf3346a4
--- /dev/null
+++ b/client/src/sagas/core/services/auto-logout.js
@@ -0,0 +1,240 @@
+/*!
+ * Copyright (c) 2024 PLANKA Software GmbH
+ * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
+ */
+
+import { buffers, eventChannel } from 'redux-saga';
+import { call, cancelled, delay, put, race, select, take } from 'redux-saga/effects';
+
+import { logout as logoutService } from './core';
+import selectors from '../../../selectors';
+import actions from '../../../actions';
+import {
+  postActivity as broadcastActivity,
+  postLogout as broadcastLogout,
+  postStayLoggedIn as broadcastStayLoggedIn,
+  subscribe as subscribeToChannel,
+} from '../../../utils/auto-logout-channel';
+import { AutoLogoutModes } from '../../../constants/Enums';
+import ActionTypes from '../../../constants/ActionTypes';
+import EntryActionTypes from '../../../constants/EntryActionTypes';
+
+const WARNING_LEAD_MS = 30 * 1000;
+const ACTIVITY_THROTTLE_MS = 1000;
+const BROADCAST_THROTTLE_MS = 2000;
+
+const MODE_DURATIONS_MS = {
+  [AutoLogoutModes.MINUTES_2]: 2 * 60 * 1000,
+  [AutoLogoutModes.MINUTES_5]: 5 * 60 * 1000,
+  [AutoLogoutModes.MINUTES_10]: 10 * 60 * 1000,
+  [AutoLogoutModes.MINUTES_30]: 30 * 60 * 1000,
+  [AutoLogoutModes.HOURS_12]: 12 * 60 * 60 * 1000,
+};
+
+const ACTIVITY_EVENTS = ['mousedown', 'keydown', 'wheel', 'touchstart', 'mousemove'];
+
+const EventTypes = {
+  LOCAL_ACTIVITY: 'localActivity',
+  REMOTE_ACTIVITY: 'remoteActivity',
+  REMOTE_LOGOUT: 'remoteLogout',
+  REMOTE_STAY_LOGGED_IN: 'remoteStayLoggedIn',
+};
+
+const MODE_CHANGE_TRIGGER_TYPES = [
+  ActionTypes.CORE_INITIALIZE,
+  ActionTypes.USER_UPDATE__SUCCESS,
+  ActionTypes.USER_UPDATE_HANDLE,
+];
+
+const selectCurrentUserAutoLogoutMode = (state) => {
+  const user = selectors.selectCurrentUser(state);
+  return user ? user.autoLogoutMode : null;
+};
+
+const createEventChannel = () =>
+  eventChannel((emit) => {
+    let lastActivityEmit = 0;
+
+    const handleActivity = () => {
+      const now = Date.now();
+      if (now - lastActivityEmit < ACTIVITY_THROTTLE_MS) {
+        return;
+      }
+      lastActivityEmit = now;
+      emit({ type: EventTypes.LOCAL_ACTIVITY });
+    };
+
+    ACTIVITY_EVENTS.forEach((event) => {
+      window.addEventListener(event, handleActivity, { passive: true });
+    });
+
+    const unsubscribe = subscribeToChannel((message) => {
+      if (!message || !message.type) {
+        return;
+      }
+      if (message.type === 'activity') {
+        emit({ type: EventTypes.REMOTE_ACTIVITY });
+      } else if (message.type === 'logout') {
+        emit({ type: EventTypes.REMOTE_LOGOUT });
+      } else if (message.type === 'stay-logged-in') {
+        emit({ type: EventTypes.REMOTE_STAY_LOGGED_IN });
+      }
+    });
+
+    return () => {
+      ACTIVITY_EVENTS.forEach((event) => {
+        window.removeEventListener(event, handleActivity);
+      });
+      unsubscribe();
+    };
+  }, buffers.sliding(8));
+
+let lastBroadcastAt = 0;
+
+function* maybeBroadcastActivity() {
+  const now = Date.now();
+  if (now - lastBroadcastAt < BROADCAST_THROTTLE_MS) {
+    return;
+  }
+  lastBroadcastAt = now;
+  yield call(broadcastActivity);
+}
+
+function* triggerLogout({ broadcast = true } = {}) {
+  if (broadcast) {
+    yield call(broadcastLogout);
+  }
+  yield put(actions.dismissAutoLogoutWarning());
+  yield call(logoutService, true);
+}
+
+function* waitForRelevantEvent(channel, predicate) {
+  while (true) {
+    const event = yield take(channel);
+    if (predicate(event)) {
+      return event;
+    }
+  }
+}
+
+function* runIdleMode(channel) {
+  // For NEVER mode: only react to remote logout broadcasts so a logout in another tab
+  // also signs out this tab.
+  yield call(waitForRelevantEvent, channel, (e) => e.type === EventTypes.REMOTE_LOGOUT);
+  yield call(triggerLogout, { broadcast: false });
+}
+
+function* runTimerMode(channel, mode) {
+  // Fall back to the safest known timer if the persisted mode is no longer recognized
+  // (e.g. partially-applied migration, hand-edited DB) — better than silently disabling.
+  const totalMs = MODE_DURATIONS_MS[mode] || MODE_DURATIONS_MS[AutoLogoutModes.MINUTES_30];
+
+  while (true) {
+    const phaseDuration = totalMs - WARNING_LEAD_MS;
+    const idleResult = yield race({
+      event: take(channel),
+      timeout: delay(phaseDuration > 0 ? phaseDuration : 0),
+    });
+
+    if (idleResult.event) {
+      const { type } = idleResult.event;
+      if (type === EventTypes.REMOTE_LOGOUT) {
+        yield call(triggerLogout, { broadcast: false });
+        return;
+      }
+      if (type === EventTypes.LOCAL_ACTIVITY) {
+        yield call(maybeBroadcastActivity);
+      }
+      // Any local/remote activity (or other events) just restarts the loop
+      // eslint-disable-next-line no-continue
+      continue;
+    }
+
+    // Timeout reached → show warning
+    const expiresAt = Date.now() + WARNING_LEAD_MS;
+    yield put(actions.showAutoLogoutWarning(expiresAt));
+
+    const warningResult = yield race({
+      dismiss: take(EntryActionTypes.AUTO_LOGOUT_WARNING_DISMISS),
+      channel: call(waitForRelevantEvent, channel, (e) =>
+        [
+          EventTypes.REMOTE_LOGOUT,
+          EventTypes.REMOTE_STAY_LOGGED_IN,
+          EventTypes.REMOTE_ACTIVITY,
+        ].includes(e.type),
+      ),
+      timeout: delay(WARNING_LEAD_MS),
+    });
+
+    if (warningResult.channel && warningResult.channel.type === EventTypes.REMOTE_LOGOUT) {
+      yield call(triggerLogout, { broadcast: false });
+      return;
+    }
+
+    yield put(actions.dismissAutoLogoutWarning());
+
+    if (warningResult.timeout) {
+      yield call(triggerLogout);
+      return;
+    }
+
+    if (warningResult.dismiss) {
+      yield call(broadcastStayLoggedIn);
+    }
+    // Loop continues — timer restarts (also resets when remote activity / stay-logged-in arrives)
+  }
+}
+
+function* runMode(channel, mode) {
+  if (!mode || mode === AutoLogoutModes.NEVER) {
+    yield call(runIdleMode, channel);
+    return;
+  }
+
+  yield call(runTimerMode, channel, mode);
+}
+
+function* waitForModeChange(currentMode) {
+  while (true) {
+    yield take(MODE_CHANGE_TRIGGER_TYPES);
+    const nextMode = yield select(selectCurrentUserAutoLogoutMode);
+    if (nextMode !== currentMode) {
+      return nextMode;
+    }
+  }
+}
+
+function* autoLogout() {
+  if (typeof window === 'undefined') {
+    return;
+  }
+
+  const channel = yield call(createEventChannel);
+
+  try {
+    while (true) {
+      const mode = yield select(selectCurrentUserAutoLogoutMode);
+
+      const result = yield race({
+        run: call(runMode, channel, mode),
+        modeChanged: call(waitForModeChange, mode),
+      });
+
+      if (!('modeChanged' in result)) {
+        // runMode completed without a mode change → logout already happened
+        return;
+      }
+      // Mode changed mid-run: clear any visible warning before re-entering with new mode
+      yield put(actions.dismissAutoLogoutWarning());
+    }
+  } finally {
+    channel.close();
+    if (yield cancelled()) {
+      yield put(actions.dismissAutoLogoutWarning());
+    }
+  }
+}
+
+export default {
+  autoLogout,
+};
diff --git a/client/src/sagas/core/services/index.js b/client/src/sagas/core/services/index.js
index 7479ab8d..0cc2f2ac 100644
--- a/client/src/sagas/core/services/index.js
+++ b/client/src/sagas/core/services/index.js
@@ -7,6 +7,7 @@ import router from './router';
 import socket from './socket';
 import bootstrap from './bootstrap';
 import core from './core';
+import autoLogout from './auto-logout';
 import modals from './modals';
 import config from './config';
 import webhooks from './webhooks';
@@ -36,6 +37,7 @@ export default {
   ...socket,
   ...bootstrap,
   ...core,
+  ...autoLogout,
   ...modals,
   ...config,
   ...webhooks,
diff --git a/client/src/selectors/core.js b/client/src/selectors/core.js
index 53b5e03d..b35edb88 100644
--- a/client/src/selectors/core.js
+++ b/client/src/selectors/core.js
@@ -15,6 +15,8 @@ export const selectClipboard = ({ core: { clipboard } }) => clipboard;
 
 export const selectConfig = ({ core: { config } }) => config;
 
+export const selectAutoLogoutWarning = ({ core: { autoLogoutWarning } }) => autoLogoutWarning;
+
 export const selectRecentCardId = ({ core: { recentCardId } }) => recentCardId;
 
 export const selectPrevCardId = ({ core: { prevCardIds } }) => prevCardIds.at(-1);
@@ -35,6 +37,7 @@ export default {
   selectIsEditModeEnabled,
   selectClipboard,
   selectConfig,
+  selectAutoLogoutWarning,
   selectRecentCardId,
   selectPrevCardId,
   selectHomeView,
diff --git a/client/src/utils/auto-logout-channel.js b/client/src/utils/auto-logout-channel.js
new file mode 100644
index 00000000..14589557
--- /dev/null
+++ b/client/src/utils/auto-logout-channel.js
@@ -0,0 +1,90 @@
+/*!
+ * Copyright (c) 2024 PLANKA Software GmbH
+ * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
+ */
+
+const CHANNEL_NAME = 'planka-auto-logout';
+const STORAGE_KEY = 'planka:auto-logout-message';
+
+const TAB_ID = `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
+
+const supportsBroadcastChannel = typeof window !== 'undefined' && 'BroadcastChannel' in window;
+
+let channel = null;
+const listeners = new Set();
+
+const dispatch = (message) => {
+  listeners.forEach((listener) => {
+    try {
+      listener(message);
+    } catch {
+      /* empty */
+    }
+  });
+};
+
+const handleStorageEvent = (event) => {
+  if (event.key !== STORAGE_KEY || !event.newValue) {
+    return;
+  }
+  try {
+    const message = JSON.parse(event.newValue);
+    if (message && message.tabId !== TAB_ID) {
+      dispatch(message);
+    }
+  } catch {
+    /* empty */
+  }
+};
+
+const ensureChannel = () => {
+  if (channel || typeof window === 'undefined') {
+    return;
+  }
+
+  if (supportsBroadcastChannel) {
+    channel = new BroadcastChannel(CHANNEL_NAME);
+    channel.addEventListener('message', (event) => {
+      if (event.data && event.data.tabId !== TAB_ID) {
+        dispatch(event.data);
+      }
+    });
+  } else {
+    window.addEventListener('storage', handleStorageEvent);
+    channel = { fallback: true };
+  }
+};
+
+const post = (message) => {
+  ensureChannel();
+  if (!channel) {
+    return;
+  }
+
+  const payload = { ...message, tabId: TAB_ID };
+
+  if (channel.fallback) {
+    try {
+      window.localStorage.setItem(STORAGE_KEY, JSON.stringify({ ...payload, _ts: Date.now() }));
+      window.localStorage.removeItem(STORAGE_KEY);
+    } catch {
+      /* empty */
+    }
+  } else {
+    channel.postMessage(payload);
+  }
+};
+
+export const postActivity = () => post({ type: 'activity' });
+
+export const postLogout = () => post({ type: 'logout' });
+
+export const postStayLoggedIn = () => post({ type: 'stay-logged-in' });
+
+export const subscribe = (handler) => {
+  ensureChannel();
+  listeners.add(handler);
+  return () => {
+    listeners.delete(handler);
+  };
+};
diff --git a/server/api/controllers/users/update.js b/server/api/controllers/users/update.js
index 88a05900..4be94eb2 100755
--- a/server/api/controllers/users/update.js
+++ b/server/api/controllers/users/update.js
@@ -95,6 +95,11 @@
  *                 enum: [byDefault, alphabetically, byCreationTime]
  *                 description: Default sort order for projects display
  *                 example: byDefault
+ *               autoLogoutMode:
+ *                 type: string
+ *                 enum: [never, 2m, 5m, 10m, 30m, 12h]
+ *                 description: Auto-logout behavior on inactivity
+ *                 example: 30m
  *               isDeactivated:
  *                 type: boolean
  *                 description: Whether the user account is deactivated and cannot log in (for admins)
@@ -200,6 +205,10 @@ module.exports = {
       type: 'string',
       isIn: Object.values(User.ProjectOrders),
     },
+    autoLogoutMode: {
+      type: 'string',
+      isIn: Object.values(User.AutoLogoutModes),
+    },
     isDeactivated: {
       type: 'boolean',
     },
@@ -266,6 +275,7 @@ module.exports = {
         'defaultEditorMode',
         'defaultHomeView',
         'defaultProjectsOrder',
+        'autoLogoutMode',
         'isDeactivated',
       ]),
     };
diff --git a/server/api/models/User.js b/server/api/models/User.js
index 964760f9..8ff3b78d 100755
--- a/server/api/models/User.js
+++ b/server/api/models/User.js
@@ -142,6 +142,12 @@
  *           default: byDefault
  *           description: Default sort order for projects display (personal field)
  *           example: byDefault
+ *         autoLogoutMode:
+ *           type: string
+ *           enum: [never, 2m, 5m, 10m, 30m, 12h]
+ *           default: 30m
+ *           description: Auto-logout behavior on inactivity (personal field)
+ *           example: 30m
  *         isTotpEnabled:
  *           type: boolean
  *           default: false
@@ -248,6 +254,15 @@ const LANGUAGES = [
 ];
 
 // TODO: find better way to handle apiKeyHash and apiKeyCreatedAt
+const AutoLogoutModes = {
+  NEVER: 'never',
+  MINUTES_2: '2m',
+  MINUTES_5: '5m',
+  MINUTES_10: '10m',
+  MINUTES_30: '30m',
+  HOURS_12: '12h',
+};
+
 const PRIVATE_FIELD_NAMES = [
   'email',
   'apiKeyPrefix',
@@ -272,6 +287,7 @@ const PERSONAL_FIELD_NAMES = [
   'defaultEditorMode',
   'defaultHomeView',
   'defaultProjectsOrder',
+  'autoLogoutMode',
 ];
 
 const INTERNAL = {
@@ -284,6 +300,7 @@ module.exports = {
   EditorModes,
   HomeViews,
   ProjectOrders,
+  AutoLogoutModes,
   LANGUAGES,
   PRIVATE_FIELD_NAMES,
   PERSONAL_FIELD_NAMES,
@@ -413,6 +430,12 @@ module.exports = {
       type: 'ref',
       columnName: 'terms_accepted_at',
     },
+    autoLogoutMode: {
+      type: 'string',
+      isIn: Object.values(AutoLogoutModes),
+      defaultsTo: AutoLogoutModes.MINUTES_30,
+      columnName: 'auto_logout_mode',
+    },
     totpSecret: {
       type: 'string',
       isNotEmptyString: true,
diff --git a/server/db/migrations/20260808120000_add_auto_logout_preference.js b/server/db/migrations/20260808120000_add_auto_logout_preference.js
new file mode 100644
index 00000000..72073e3e
--- /dev/null
+++ b/server/db/migrations/20260808120000_add_auto_logout_preference.js
@@ -0,0 +1,14 @@
+/*!
+ * Copyright (c) 2024 PLANKA Software GmbH
+ * Licensed under the Fair Use License: https://github.com/plankanban/planka/blob/master/LICENSE.md
+ */
+
+module.exports.up = (knex) =>
+  knex.schema.alterTable('user_account', (table) => {
+    table.string('auto_logout_mode').notNullable().defaultTo('30m');
+  });
+
+module.exports.down = (knex) =>
+  knex.schema.alterTable('user_account', (table) => {
+    table.dropColumn('auto_logout_mode');
+  });