diff --git a/lib/tunnelbroker/secondary-tunnelbroker-connection.js b/lib/tunnelbroker/secondary-tunnelbroker-connection.js
new file mode 100644
index 000000000..b4921685c
--- /dev/null
+++ b/lib/tunnelbroker/secondary-tunnelbroker-connection.js
@@ -0,0 +1,19 @@
+// @flow
+
+import type { MessageToDeviceRequest } from '../types/tunnelbroker/message-to-device-request-types.js';
+
+type RemoveCallback = () => void;
+
+export type SecondaryTunnelbrokerConnection = {
+  // Used by an inactive tab to send messages
+  sendMessage: MessageToDeviceRequest => mixed,
+  // Active tab receives messages from inactive tabs
+  onSendMessage: ((MessageToDeviceRequest) => mixed) => RemoveCallback,
+
+  // Active tab sets the message status of messages from inactive tabs
+  setMessageStatus: (messageID: string, error: ?string) => mixed,
+  // Inactive tabs receive message status and resolve or reject promises
+  onMessageStatus: (
+    ((messageID: string, error: ?string) => mixed),
+  ) => RemoveCallback,
+};
diff --git a/lib/tunnelbroker/tunnelbroker-context.js b/lib/tunnelbroker/tunnelbroker-context.js
index cc608211e..f758e646e 100644
--- a/lib/tunnelbroker/tunnelbroker-context.js
+++ b/lib/tunnelbroker/tunnelbroker-context.js
@@ -1,336 +1,395 @@
 // @flow
 
 import invariant from 'invariant';
 import * as React from 'react';
 import uuid from 'uuid';
 
+import type { SecondaryTunnelbrokerConnection } from './secondary-tunnelbroker-connection.js';
 import { tunnnelbrokerURL } from '../facts/tunnelbroker.js';
 import { peerToPeerMessageHandler } from '../handlers/peer-to-peer-message-handler.js';
 import { IdentityClientContext } from '../shared/identity-client-context.js';
 import { tunnelbrokerHeartbeatTimeout } from '../shared/timeouts.js';
 import type { MessageReceiveConfirmation } from '../types/tunnelbroker/message-receive-confirmation-types.js';
 import type { MessageSentStatus } from '../types/tunnelbroker/message-to-device-request-status-types.js';
 import type { MessageToDeviceRequest } from '../types/tunnelbroker/message-to-device-request-types.js';
 import {
   type TunnelbrokerMessage,
   tunnelbrokerMessageTypes,
   tunnelbrokerMessageValidator,
 } from '../types/tunnelbroker/messages.js';
 import {
   type PeerToPeerMessage,
   peerToPeerMessageValidator,
 } from '../types/tunnelbroker/peer-to-peer-message-types.js';
 import type {
   AnonymousInitializationMessage,
   TunnelbrokerInitializationMessage,
   ConnectionInitializationMessage,
 } from '../types/tunnelbroker/session-types.js';
 import type { Heartbeat } from '../types/websocket/heartbeat-types.js';
 
 export type ClientMessageToDevice = {
   +deviceID: string,
   +payload: string,
 };
 
 export type TunnelbrokerSocketListener = (
   message: TunnelbrokerMessage,
 ) => mixed;
 
 type PromiseCallbacks = {
   +resolve: () => void,
   +reject: (error: string) => void,
 };
 type Promises = { [clientMessageID: string]: PromiseCallbacks };
 
 type TunnelbrokerContextType = {
   +sendMessage: (message: ClientMessageToDevice) => Promise<void>,
   +addListener: (listener: TunnelbrokerSocketListener) => void,
   +removeListener: (listener: TunnelbrokerSocketListener) => void,
   +connected: boolean,
   +setUnauthorizedDeviceID: (unauthorizedDeviceID: ?string) => void,
 };
 
 const TunnelbrokerContext: React.Context<?TunnelbrokerContextType> =
   React.createContext<?TunnelbrokerContextType>();
 
 type Props = {
   +children: React.Node,
   +shouldBeClosed?: boolean,
   +onClose?: () => mixed,
   +initMessage: ?ConnectionInitializationMessage,
+  +secondaryTunnelbrokerConnection?: SecondaryTunnelbrokerConnection,
 };
 
 function createAnonymousInitMessage(
   deviceID: string,
 ): AnonymousInitializationMessage {
   return ({
     type: 'AnonymousInitializationMessage',
     deviceID,
     deviceType: 'mobile',
   }: AnonymousInitializationMessage);
 }
 
 function TunnelbrokerProvider(props: Props): React.Node {
   const {
     children,
     shouldBeClosed,
     onClose,
     initMessage: initMessageProp,
+    secondaryTunnelbrokerConnection,
   } = props;
   const [connected, setConnected] = React.useState(false);
   const listeners = React.useRef<Set<TunnelbrokerSocketListener>>(new Set());
   const socket = React.useRef<?WebSocket>(null);
   const promises = React.useRef<Promises>({});
   const heartbeatTimeoutID = React.useRef<?TimeoutID>();
   const [unauthorizedDeviceID, setUnauthorizedDeviceID] =
     React.useState<?string>(null);
   const isAuthorized = !unauthorizedDeviceID;
 
   const identityContext = React.useContext(IdentityClientContext);
   invariant(identityContext, 'Identity context should be set');
   const { identityClient } = identityContext;
 
   const initMessage = React.useMemo(() => {
     if (shouldBeClosed) {
       return null;
     }
     if (!unauthorizedDeviceID) {
       return initMessageProp;
     }
     return createAnonymousInitMessage(unauthorizedDeviceID);
   }, [shouldBeClosed, unauthorizedDeviceID, initMessageProp]);
 
   const previousInitMessage =
     React.useRef<?TunnelbrokerInitializationMessage>(initMessage);
   const initMessageChanged = initMessage !== previousInitMessage.current;
   previousInitMessage.current = initMessage;
 
   const stopHeartbeatTimeout = React.useCallback(() => {
     if (heartbeatTimeoutID.current) {
       clearTimeout(heartbeatTimeoutID.current);
       heartbeatTimeoutID.current = null;
     }
   }, []);
 
   const resetHeartbeatTimeout = React.useCallback(() => {
     stopHeartbeatTimeout();
     heartbeatTimeoutID.current = setTimeout(() => {
       socket.current?.close();
       setConnected(false);
     }, tunnelbrokerHeartbeatTimeout);
   }, [stopHeartbeatTimeout]);
 
   // determine if the socket is active (not closed or closing)
   const isSocketActive =
     socket.current?.readyState === WebSocket.OPEN ||
     socket.current?.readyState === WebSocket.CONNECTING;
 
   // The Tunnelbroker connection can have 4 states:
   // - DISCONNECTED: isSocketActive = false, connected = false
   //   Should be in this state when initMessage is null
   // - CONNECTING: isSocketActive = true, connected = false
   //   This lasts until Tunnelbroker sends ConnectionInitializationResponse
   // - CONNECTED: isSocketActive = true, connected = true
   // - DISCONNECTING: isSocketActive = false, connected = true
   //   This lasts between socket.close() and socket.onclose()
   React.useEffect(() => {
     // when initMessage changes, we need to close the socket and open a new one
     if ((!initMessage || initMessageChanged) && isSocketActive) {
       socket.current?.close();
       return;
     }
 
     // when we're already connected (or pending disconnection),
     // or there's no init message to start with, we don't need to do anything
     if (connected || !initMessage) {
       return;
     }
 
     const tunnelbrokerSocket = new WebSocket(tunnnelbrokerURL);
 
     tunnelbrokerSocket.onopen = () => {
       tunnelbrokerSocket.send(JSON.stringify(initMessage));
     };
 
     tunnelbrokerSocket.onclose = () => {
       // this triggers the effect hook again and reconnect
       setConnected(false);
       onClose?.();
       console.log('Connection to Tunnelbroker closed');
     };
     tunnelbrokerSocket.onerror = e => {
       console.log('Tunnelbroker socket error:', e.message);
     };
     tunnelbrokerSocket.onmessage = (event: MessageEvent) => {
       if (typeof event.data !== 'string') {
         console.log('socket received a non-string message');
         return;
       }
       let rawMessage;
       try {
         rawMessage = JSON.parse(event.data);
       } catch (e) {
         console.log('error while parsing Tunnelbroker message:', e.message);
         return;
       }
 
       if (!tunnelbrokerMessageValidator.is(rawMessage)) {
         console.log('invalid TunnelbrokerMessage');
         return;
       }
       const message: TunnelbrokerMessage = rawMessage;
 
       resetHeartbeatTimeout();
 
       for (const listener of listeners.current) {
         listener(message);
       }
 
       if (
         message.type ===
         tunnelbrokerMessageTypes.CONNECTION_INITIALIZATION_RESPONSE
       ) {
         if (message.status.type === 'Success' && !connected) {
           setConnected(true);
           console.log(
             'session with Tunnelbroker created. isAuthorized:',
             isAuthorized,
           );
         } else if (message.status.type === 'Success' && connected) {
           console.log(
             'received ConnectionInitializationResponse with status: Success for already connected socket',
           );
         } else {
           setConnected(false);
           console.log(
             'creating session with Tunnelbroker error:',
             message.status.data,
           );
         }
       } else if (message.type === tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE) {
         const confirmation: MessageReceiveConfirmation = {
           type: tunnelbrokerMessageTypes.MESSAGE_RECEIVE_CONFIRMATION,
           messageIDs: [message.messageID],
         };
         socket.current?.send(JSON.stringify(confirmation));
 
         let rawPeerToPeerMessage;
         try {
           rawPeerToPeerMessage = JSON.parse(message.payload);
         } catch (e) {
           console.log(
             'error while parsing Tunnelbroker peer-to-peer message:',
             e.message,
           );
           return;
         }
 
         if (!peerToPeerMessageValidator.is(rawPeerToPeerMessage)) {
           console.log('invalid Tunnelbroker PeerToPeerMessage');
           return;
         }
         const peerToPeerMessage: PeerToPeerMessage = rawPeerToPeerMessage;
         void peerToPeerMessageHandler(peerToPeerMessage, identityClient);
       } else if (
         message.type ===
         tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE_REQUEST_STATUS
       ) {
         for (const status: MessageSentStatus of message.clientMessageIDs) {
           if (status.type === 'Success') {
             promises.current[status.data]?.resolve();
             delete promises.current[status.data];
           } else if (status.type === 'Error') {
             promises.current[status.data.id]?.reject(status.data.error);
             delete promises.current[status.data.id];
           } else if (status.type === 'SerializationError') {
             console.log('SerializationError for message: ', status.data);
           } else if (status.type === 'InvalidRequest') {
             console.log('Tunnelbroker recorded InvalidRequest');
           }
         }
       } else if (message.type === tunnelbrokerMessageTypes.HEARTBEAT) {
         const heartbeat: Heartbeat = {
           type: tunnelbrokerMessageTypes.HEARTBEAT,
         };
         socket.current?.send(JSON.stringify(heartbeat));
       }
     };
 
     socket.current = tunnelbrokerSocket;
   }, [
     connected,
     initMessage,
     initMessageChanged,
     isSocketActive,
     isAuthorized,
     resetHeartbeatTimeout,
     stopHeartbeatTimeout,
     identityClient,
     onClose,
   ]);
 
+  const sendMessageToDeviceRequest: (
+    request: MessageToDeviceRequest,
+  ) => Promise<void> = React.useCallback(
+    request => {
+      return new Promise((resolve, reject) => {
+        const socketActive = connected && socket.current;
+        if (!shouldBeClosed && !socketActive) {
+          throw new Error('Tunnelbroker not connected');
+        }
+        promises.current[request.clientMessageID] = {
+          resolve,
+          reject,
+        };
+        if (socketActive) {
+          socket.current?.send(JSON.stringify(request));
+        } else {
+          secondaryTunnelbrokerConnection?.sendMessage(request);
+        }
+      });
+    },
+    [connected, secondaryTunnelbrokerConnection, shouldBeClosed],
+  );
+
   const sendMessage: (message: ClientMessageToDevice) => Promise<void> =
     React.useCallback(
       (message: ClientMessageToDevice) => {
-        if (!connected || !socket.current) {
-          throw new Error('Tunnelbroker not connected');
-        }
         const clientMessageID = uuid.v4();
         const messageToDevice: MessageToDeviceRequest = {
           type: tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE_REQUEST,
           clientMessageID,
           deviceID: message.deviceID,
           payload: message.payload,
         };
 
-        return new Promise((resolve, reject) => {
-          promises.current[clientMessageID] = {
-            resolve,
-            reject,
-          };
-          socket.current?.send(JSON.stringify(messageToDevice));
-        });
+        return sendMessageToDeviceRequest(messageToDevice);
       },
-      [connected],
+      [sendMessageToDeviceRequest],
     );
 
+  React.useEffect(
+    () =>
+      secondaryTunnelbrokerConnection?.onSendMessage(message => {
+        if (shouldBeClosed) {
+          // We aren't supposed to be handling it
+          return;
+        }
+
+        void (async () => {
+          try {
+            await sendMessageToDeviceRequest(message);
+            secondaryTunnelbrokerConnection.setMessageStatus(
+              message.clientMessageID,
+            );
+          } catch (error) {
+            secondaryTunnelbrokerConnection.setMessageStatus(
+              message.clientMessageID,
+              error,
+            );
+          }
+        })();
+      }),
+    [
+      secondaryTunnelbrokerConnection,
+      sendMessageToDeviceRequest,
+      shouldBeClosed,
+    ],
+  );
+
+  React.useEffect(
+    () =>
+      secondaryTunnelbrokerConnection?.onMessageStatus((messageID, error) => {
+        if (error) {
+          promises.current[messageID].reject(error);
+        } else {
+          promises.current[messageID].resolve();
+        }
+        delete promises.current[messageID];
+      }),
+    [secondaryTunnelbrokerConnection],
+  );
+
   const addListener = React.useCallback(
     (listener: TunnelbrokerSocketListener) => {
       listeners.current.add(listener);
     },
     [],
   );
 
   const removeListener = React.useCallback(
     (listener: TunnelbrokerSocketListener) => {
       listeners.current.delete(listener);
     },
     [],
   );
 
   const value: TunnelbrokerContextType = React.useMemo(
     () => ({
       sendMessage,
       connected,
       addListener,
       removeListener,
       setUnauthorizedDeviceID,
     }),
     [addListener, connected, removeListener, sendMessage],
   );
 
   return (
     <TunnelbrokerContext.Provider value={value}>
       {children}
     </TunnelbrokerContext.Provider>
   );
 }
 
 function useTunnelbroker(): TunnelbrokerContextType {
   const context = React.useContext(TunnelbrokerContext);
   invariant(context, 'TunnelbrokerContext not found');
 
   return context;
 }
 
 export { TunnelbrokerProvider, useTunnelbroker };
diff --git a/web/app.react.js b/web/app.react.js
index 754936f69..6af05a21d 100644
--- a/web/app.react.js
+++ b/web/app.react.js
@@ -1,446 +1,565 @@
 // @flow
 
 import 'basscss/css/basscss.min.css';
 import './theme.css';
 import { config as faConfig } from '@fortawesome/fontawesome-svg-core';
 import classnames from 'classnames';
 import _isEqual from 'lodash/fp/isEqual.js';
 import * as React from 'react';
 import { DndProvider } from 'react-dnd';
 import { HTML5Backend } from 'react-dnd-html5-backend';
 import { WagmiConfig } from 'wagmi';
 
 import {
   fetchEntriesActionTypes,
   updateCalendarQueryActionTypes,
 } from 'lib/actions/entry-actions.js';
 import { ChatMentionContextProvider } from 'lib/components/chat-mention-provider.react.js';
 import { EditUserAvatarProvider } from 'lib/components/edit-user-avatar-provider.react.js';
 import {
   ModalProvider,
   useModalContext,
 } from 'lib/components/modal-provider.react.js';
 import { StaffContextProvider } from 'lib/components/staff-provider.react.js';
 import { IdentitySearchProvider } from 'lib/identity-search/identity-search-context.js';
 import {
   createLoadingStatusSelector,
   combineLoadingStatuses,
 } from 'lib/selectors/loading-selectors.js';
 import { isLoggedIn } from 'lib/selectors/user-selectors.js';
 import { extractMajorDesktopVersion } from 'lib/shared/version-utils.js';
+import type { SecondaryTunnelbrokerConnection } from 'lib/tunnelbroker/secondary-tunnelbroker-connection.js';
 import { TunnelbrokerProvider } from 'lib/tunnelbroker/tunnelbroker-context.js';
 import type { LoadingStatus } from 'lib/types/loading-types.js';
 import type { WebNavInfo } from 'lib/types/nav-types.js';
 import type { Dispatch } from 'lib/types/redux-types.js';
+import type { MessageToDeviceRequest } from 'lib/types/tunnelbroker/message-to-device-request-types.js';
 import { getConfig, registerConfig } from 'lib/utils/config.js';
 import { useDispatch } from 'lib/utils/redux-utils.js';
 import { infoFromURL } from 'lib/utils/url-utils.js';
 import { AlchemyENSCacheProvider, wagmiConfig } from 'lib/utils/wagmi-utils.js';
 
 import QrCodeLogin from './account/qr-code-login.react.js';
 import AppThemeWrapper from './app-theme-wrapper.react.js';
 import { authoritativeKeyserverID } from './authoritative-keyserver.js';
 import WebEditThreadAvatarProvider from './avatars/web-edit-thread-avatar-provider.react.js';
 import Calendar from './calendar/calendar.react.js';
 import Chat from './chat/chat.react.js';
 import { EditModalProvider } from './chat/edit-message-provider.js';
 import { MemberListSidebarProvider } from './chat/member-list-sidebar/member-list-sidebar-provider.react.js';
 import NavigationArrows from './components/navigation-arrows.react.js';
 import { olmAPI } from './crypto/olm-api.js';
 import { initOpaque } from './crypto/opaque-utils.js';
 import { getDatabaseModule } from './database/database-module-provider.js';
 import electron from './electron.js';
 import InputStateContainer from './input/input-state-container.react.js';
 import InviteLinkHandler from './invite-links/invite-link-handler.react.js';
 import InviteLinksRefresher from './invite-links/invite-links-refresher.react.js';
 import LoadingIndicator from './loading-indicator.react.js';
 import { MenuProvider } from './menu-provider.react.js';
 import UpdateModalHandler from './modals/update-modal.react.js';
 import SettingsSwitcher from './navigation-panels/settings-switcher.react.js';
 import Topbar from './navigation-panels/topbar.react.js';
 import useBadgeHandler from './push-notif/badge-handler.react.js';
 import { PushNotificationsHandler } from './push-notif/push-notifs-handler.js';
 import { updateNavInfoActionType } from './redux/action-types.js';
 import DisconnectedBar from './redux/disconnected-bar.js';
 import FocusHandler from './redux/focus-handler.react.js';
 import { KeyserverReachabilityHandler } from './redux/keyserver-reachability-handler.js';
 import { persistConfig } from './redux/persist.js';
 import PolicyAcknowledgmentHandler from './redux/policy-acknowledgment-handler.js';
 import { useSelector } from './redux/redux-utils.js';
 import VisibilityHandler from './redux/visibility-handler.react.js';
 import history from './router-history.js';
 import { MessageSearchStateProvider } from './search/message-search-state-provider.react.js';
 import { createTunnelbrokerInitMessage } from './selectors/tunnelbroker-selectors.js';
 import AccountSettings from './settings/account-settings.react.js';
 import DangerZone from './settings/danger-zone.react.js';
 import KeyserverSelectionList from './settings/keyserver-selection-list.react.js';
 import CommunityPicker from './sidebar/community-picker.react.js';
 import Splash from './splash/splash.react.js';
 import './typography.css';
 import css from './style.css';
 import { TooltipProvider } from './tooltips/tooltip-provider.js';
 import { canonicalURLFromReduxState, navInfoFromURL } from './url-utils.js';
 import { useWebLock, TUNNELBROKER_LOCK_NAME } from './web-lock.js';
 
 void initOpaque();
 
 // We want Webpack's css-loader and style-loader to handle the Fontawesome CSS,
 // so we disable the autoAddCss logic and import the CSS file. Otherwise every
 // icon flashes huge for a second before the CSS is loaded.
 import '@fortawesome/fontawesome-svg-core/styles.css';
 
 faConfig.autoAddCss = false;
 const desktopDetails = electron?.version
   ? { majorDesktopVersion: extractMajorDesktopVersion(electron?.version) }
   : null;
 
 registerConfig({
   // We can't securely cache credentials on web
   resolveKeyserverSessionInvalidationUsingNativeCredentials: null,
   setSessionIDOnRequest: true,
   // Never reset the calendar range
   calendarRangeInactivityLimit: null,
   platformDetails: {
     platform: electron?.platform ?? 'web',
     codeVersion: 73,
     stateVersion: persistConfig.version,
     ...desktopDetails,
   },
   authoritativeKeyserverID,
   olmAPI,
 });
 
 const versionBroadcast = new BroadcastChannel('comm_version');
 versionBroadcast.postMessage(getConfig().platformDetails.codeVersion);
 versionBroadcast.onmessage = (event: MessageEvent) => {
   if (event.data && event.data !== getConfig().platformDetails.codeVersion) {
     location.reload();
   }
 };
 
 // Start initializing the database immediately
 void getDatabaseModule();
 
 type BaseProps = {
   +location: {
     +pathname: string,
     ...
   },
 };
 type Props = {
   ...BaseProps,
   // Redux state
   +navInfo: WebNavInfo,
   +entriesLoadingStatus: LoadingStatus,
   +loggedIn: boolean,
   +activeThreadCurrentlyUnread: boolean,
   // Redux dispatch functions
   +dispatch: Dispatch,
   +modals: $ReadOnlyArray<React.Node>,
 };
 
 class App extends React.PureComponent<Props> {
   componentDidMount() {
     const {
       navInfo,
       location: { pathname },
       loggedIn,
     } = this.props;
     const newURL = canonicalURLFromReduxState(navInfo, pathname, loggedIn);
     if (pathname !== newURL) {
       history.replace(newURL);
     }
   }
 
   componentDidUpdate(prevProps: Props) {
     const {
       navInfo,
       location: { pathname },
       loggedIn,
     } = this.props;
     if (!_isEqual(navInfo)(prevProps.navInfo)) {
       const newURL = canonicalURLFromReduxState(navInfo, pathname, loggedIn);
       if (newURL !== pathname) {
         history.push(newURL);
       }
     } else if (pathname !== prevProps.location.pathname) {
       const urlInfo = infoFromURL(pathname);
       const newNavInfo = navInfoFromURL(urlInfo, { navInfo });
       if (!_isEqual(newNavInfo)(navInfo)) {
         this.props.dispatch({
           type: updateNavInfoActionType,
           payload: newNavInfo,
         });
       }
     } else if (loggedIn !== prevProps.loggedIn) {
       const newURL = canonicalURLFromReduxState(navInfo, pathname, loggedIn);
       if (newURL !== pathname) {
         history.replace(newURL);
       }
     }
     if (loggedIn !== prevProps.loggedIn) {
       electron?.clearHistory();
     }
   }
 
   onWordmarkClicked = () => {
     this.props.dispatch({
       type: updateNavInfoActionType,
       payload: { tab: 'chat' },
     });
   };
 
   render(): React.Node {
     let content;
     if (this.props.loggedIn) {
       content = (
         <>
           <WebEditThreadAvatarProvider>
             <EditUserAvatarProvider>
               <StaffContextProvider>
                 <MemberListSidebarProvider>
                   {this.renderMainContent()}
                   {this.props.modals}
                 </MemberListSidebarProvider>
               </StaffContextProvider>
             </EditUserAvatarProvider>
           </WebEditThreadAvatarProvider>
         </>
       );
     } else {
       content = (
         <>
           {this.renderLoginPage()}
           {this.props.modals}
         </>
       );
     }
     return (
       <DndProvider backend={HTML5Backend}>
         <EditModalProvider>
           <MenuProvider>
             <WagmiConfig config={wagmiConfig}>
               <AlchemyENSCacheProvider>
                 <TooltipProvider>
                   <MessageSearchStateProvider>
                     <ChatMentionContextProvider>
                       <FocusHandler />
                       <VisibilityHandler />
                       <PolicyAcknowledgmentHandler />
                       <PushNotificationsHandler />
                       <InviteLinkHandler />
                       <InviteLinksRefresher />
                       {content}
                     </ChatMentionContextProvider>
                   </MessageSearchStateProvider>
                 </TooltipProvider>
               </AlchemyENSCacheProvider>
             </WagmiConfig>
           </MenuProvider>
         </EditModalProvider>
       </DndProvider>
     );
   }
 
   onHeaderDoubleClick = (): void => electron?.doubleClickTopBar();
   stopDoubleClickPropagation: ?(SyntheticEvent<HTMLAnchorElement>) => void =
     electron ? e => e.stopPropagation() : null;
 
   renderLoginPage(): React.Node {
     const { loginMethod } = this.props.navInfo;
 
     if (loginMethod === 'qr-code') {
       return <QrCodeLogin />;
     }
 
     return <Splash />;
   }
 
   renderMainContent(): React.Node {
     const mainContent = this.getMainContentWithSwitcher();
 
     let navigationArrows = null;
     if (electron) {
       navigationArrows = <NavigationArrows />;
     }
 
     const headerClasses = classnames({
       [css.header]: true,
       [css['electron-draggable']]: electron,
     });
 
     const wordmarkClasses = classnames({
       [css.wordmark]: true,
       [css['electron-non-draggable']]: electron,
       [css['wordmark-macos']]: electron?.platform === 'macos',
     });
 
     return (
       <div className={css.layout}>
         <KeyserverReachabilityHandler />
         <DisconnectedBar />
         <UpdateModalHandler />
         <header
           className={headerClasses}
           onDoubleClick={this.onHeaderDoubleClick}
         >
           <div className={css['main-header']}>
             <h1 className={wordmarkClasses}>
               <a
                 title="Comm Home"
                 aria-label="Go to Comm Home"
                 onClick={this.onWordmarkClicked}
                 onDoubleClick={this.stopDoubleClickPropagation}
               >
                 Comm
               </a>
             </h1>
             {navigationArrows}
             <div className={css['upper-right']}>
               <LoadingIndicator
                 status={this.props.entriesLoadingStatus}
                 size="medium"
                 loadingClassName={css['page-loading']}
                 errorClassName={css['page-error']}
               />
             </div>
           </div>
         </header>
         <InputStateContainer>{mainContent}</InputStateContainer>
         <div className={css.sidebar}>
           <CommunityPicker />
         </div>
       </div>
     );
   }
 
   getMainContentWithSwitcher(): React.Node {
     const { tab, settingsSection } = this.props.navInfo;
     let mainContent: React.Node;
 
     if (tab === 'settings') {
       if (settingsSection === 'account') {
         mainContent = <AccountSettings />;
       } else if (settingsSection === 'friend-list') {
         mainContent = null;
       } else if (settingsSection === 'block-list') {
         mainContent = null;
       } else if (settingsSection === 'keyservers') {
         mainContent = <KeyserverSelectionList />;
       } else if (settingsSection === 'build-info') {
         mainContent = null;
       } else if (settingsSection === 'danger-zone') {
         mainContent = <DangerZone />;
       }
       return (
         <div className={css['main-content-container']}>
           <div className={css.switcher}>
             <SettingsSwitcher />
           </div>
           <div className={css['main-content']}>{mainContent}</div>
         </div>
       );
     }
 
     if (tab === 'calendar') {
       mainContent = <Calendar url={this.props.location.pathname} />;
     } else if (tab === 'chat') {
       mainContent = <Chat />;
     }
 
     const mainContentClass = classnames(
       css['main-content-container'],
       css['main-content-container-column'],
     );
     return (
       <div className={mainContentClass}>
         <Topbar />
         <div className={css['main-content']}>{mainContent}</div>
       </div>
     );
   }
 }
 
+const WEB_TUNNELBROKER_CHANNEL = new BroadcastChannel('shared-tunnelbroker');
+const WEB_TUNNELBROKER_MESSAGE_TYPES = Object.freeze({
+  SEND_MESSAGE: 'send-message',
+  MESSAGE_STATUS: 'message-status',
+});
+
+function useOtherTabsTunnelbrokerConnection(): SecondaryTunnelbrokerConnection {
+  const onSendMessageCallbacks = React.useRef<
+    Set<(MessageToDeviceRequest) => mixed>,
+  >(new Set());
+
+  const onMessageStatusCallbacks = React.useRef<
+    Set<(messageID: string, error: ?string) => mixed>,
+  >(new Set());
+
+  React.useEffect(() => {
+    const messageHandler = (event: MessageEvent) => {
+      if (typeof event.data !== 'object' || !event.data) {
+        console.log(
+          'Invalid message received from shared ' +
+            'tunnelbroker broadcast channel',
+          event.data,
+        );
+        return;
+      }
+      const data = event.data;
+      if (data.type === WEB_TUNNELBROKER_MESSAGE_TYPES.SEND_MESSAGE) {
+        if (typeof data.message !== 'object' || !data.message) {
+          console.log(
+            'Invalid tunnelbroker message request received ' +
+              'from shared tunnelbroker broadcast channel',
+            event.data,
+          );
+          return;
+        }
+        // We know that the input was already validated
+        const message: MessageToDeviceRequest = (data.message: any);
+
+        for (const callback of onSendMessageCallbacks.current) {
+          callback(message);
+        }
+      } else if (data.type === WEB_TUNNELBROKER_MESSAGE_TYPES.MESSAGE_STATUS) {
+        if (typeof data.messageID !== 'string') {
+          console.log(
+            'Missing message id in message status message ' +
+              'from shared tunnelbroker broadcast channel',
+          );
+          return;
+        }
+        const messageID = data.messageID;
+
+        if (
+          typeof data.error !== 'string' &&
+          data.error !== null &&
+          data.error !== undefined
+        ) {
+          console.log(
+            'Invalid error in message status message ' +
+              'from shared tunnelbroker broadcast channel',
+            data.error,
+          );
+          return;
+        }
+        const error = data.error;
+
+        for (const callback of onMessageStatusCallbacks.current) {
+          callback(messageID, error);
+        }
+      } else {
+        console.log(
+          'Invalid message type ' +
+            'from shared tunnelbroker broadcast channel',
+          data,
+        );
+      }
+    };
+
+    WEB_TUNNELBROKER_CHANNEL.addEventListener('message', messageHandler);
+    return () =>
+      WEB_TUNNELBROKER_CHANNEL.removeEventListener('message', messageHandler);
+  }, [onMessageStatusCallbacks, onSendMessageCallbacks]);
+
+  return React.useMemo(
+    () => ({
+      sendMessage: message =>
+        WEB_TUNNELBROKER_CHANNEL.postMessage({
+          type: WEB_TUNNELBROKER_MESSAGE_TYPES.SEND_MESSAGE,
+          message,
+        }),
+      onSendMessage: callback => {
+        onSendMessageCallbacks.current.add(callback);
+        return () => {
+          onSendMessageCallbacks.current.delete(callback);
+        };
+      },
+      setMessageStatus: (messageID, error) => {
+        WEB_TUNNELBROKER_CHANNEL.postMessage({
+          type: WEB_TUNNELBROKER_MESSAGE_TYPES.MESSAGE_STATUS,
+          messageID,
+          error,
+        });
+      },
+      onMessageStatus: callback => {
+        onMessageStatusCallbacks.current.add(callback);
+        return () => {
+          onMessageStatusCallbacks.current.delete(callback);
+        };
+      },
+    }),
+    [onMessageStatusCallbacks, onSendMessageCallbacks],
+  );
+}
+
 const fetchEntriesLoadingStatusSelector = createLoadingStatusSelector(
   fetchEntriesActionTypes,
 );
 const updateCalendarQueryLoadingStatusSelector = createLoadingStatusSelector(
   updateCalendarQueryActionTypes,
 );
 
 const ConnectedApp: React.ComponentType<BaseProps> = React.memo<BaseProps>(
   function ConnectedApp(props) {
     const activeChatThreadID = useSelector(
       state => state.navInfo.activeChatThreadID,
     );
     const navInfo = useSelector(state => state.navInfo);
 
     const fetchEntriesLoadingStatus = useSelector(
       fetchEntriesLoadingStatusSelector,
     );
     const updateCalendarQueryLoadingStatus = useSelector(
       updateCalendarQueryLoadingStatusSelector,
     );
     const entriesLoadingStatus = combineLoadingStatuses(
       fetchEntriesLoadingStatus,
       updateCalendarQueryLoadingStatus,
     );
 
     const loggedIn = useSelector(isLoggedIn);
     const activeThreadCurrentlyUnread = useSelector(
       state =>
         !activeChatThreadID ||
         !!state.threadStore.threadInfos[activeChatThreadID]?.currentUser.unread,
     );
 
     useBadgeHandler();
 
     const dispatch = useDispatch();
     const modalContext = useModalContext();
     const modals = React.useMemo(
       () =>
         modalContext.modals.map(([modal, key]) => (
           <React.Fragment key={key}>{modal}</React.Fragment>
         )),
       [modalContext.modals],
     );
 
     const tunnelbrokerInitMessage = useSelector(createTunnelbrokerInitMessage);
 
     const { lockStatus, releaseLockOrAbortRequest } = useWebLock(
       TUNNELBROKER_LOCK_NAME,
     );
 
+    const secondaryTunnelbrokerConnection: SecondaryTunnelbrokerConnection =
+      useOtherTabsTunnelbrokerConnection();
+
     return (
       <AppThemeWrapper>
         <TunnelbrokerProvider
           initMessage={tunnelbrokerInitMessage}
           shouldBeClosed={lockStatus !== 'acquired'}
           onClose={releaseLockOrAbortRequest}
+          secondaryTunnelbrokerConnection={secondaryTunnelbrokerConnection}
         >
           <IdentitySearchProvider>
             <App
               {...props}
               navInfo={navInfo}
               entriesLoadingStatus={entriesLoadingStatus}
               loggedIn={loggedIn}
               activeThreadCurrentlyUnread={activeThreadCurrentlyUnread}
               dispatch={dispatch}
               modals={modals}
             />
           </IdentitySearchProvider>
         </TunnelbrokerProvider>
       </AppThemeWrapper>
     );
   },
 );
 
 function AppWithProvider(props: BaseProps): React.Node {
   return (
     <ModalProvider>
       <ConnectedApp {...props} />
     </ModalProvider>
   );
 }
 
 export default AppWithProvider;