diff --git a/keyserver/src/responders/website-responders.js b/keyserver/src/responders/website-responders.js
--- a/keyserver/src/responders/website-responders.js
+++ b/keyserver/src/responders/website-responders.js
@@ -245,6 +245,10 @@
   _persist: t.Nil,
   commServicesAccessToken: t.Nil,
   inviteLinksStore: inviteLinksStoreValidator,
+  lastCommunicatedPlatformDetails: t.irreducible(
+    'default lastCommunicatedPlatformDetails',
+    _isEqual({}),
+  ),
 });
 
 async function websiteResponder(
@@ -584,6 +588,7 @@
     _persist: null,
     commServicesAccessToken: null,
     inviteLinksStore: inviteLinksStorePromise,
+    lastCommunicatedPlatformDetails: {},
   });
   const validatedInitialReduxState = validateOutput(
     viewer.platformDetails,
diff --git a/lib/actions/device-actions.js b/lib/actions/device-actions.js
--- a/lib/actions/device-actions.js
+++ b/lib/actions/device-actions.js
@@ -35,9 +35,13 @@
     };
   };
 
+const updateLastCommunicatedPlatformDetailsActionType =
+  'UPDATE_LAST_COMMUNICATED_PLATFORM_DETAILS';
+
 export {
   setDeviceTokenActionTypes,
   setDeviceToken,
   getVersionActionTypes,
   getVersion,
+  updateLastCommunicatedPlatformDetailsActionType,
 };
diff --git a/lib/hooks/toggle-unread-status.js b/lib/hooks/toggle-unread-status.js
--- a/lib/hooks/toggle-unread-status.js
+++ b/lib/hooks/toggle-unread-status.js
@@ -38,10 +38,10 @@
       setThreadUnreadStatusActionTypes,
       boundSetThreadUnreadStatus(request),
       undefined,
-      {
+      ({
         threadID: threadInfo.id,
         unread: !currentUser.unread,
-      },
+      }: { +threadID: string, +unread: boolean }),
     );
     afterAction();
   }, [
diff --git a/lib/reducers/last-communicated-platform-details-reducer.js b/lib/reducers/last-communicated-platform-details-reducer.js
new file mode 100644
--- /dev/null
+++ b/lib/reducers/last-communicated-platform-details-reducer.js
@@ -0,0 +1,35 @@
+// @flow
+
+import { updateLastCommunicatedPlatformDetailsActionType } from '../actions/device-actions.js';
+import { siweAuthActionTypes } from '../actions/siwe-actions.js';
+import {
+  logInActionTypes,
+  registerActionTypes,
+} from '../actions/user-actions.js';
+import type { LastCommunicatedPlatformDetails } from '../types/device-types';
+import type { BaseAction } from '../types/redux-types';
+import { getConfig } from '../utils/config.js';
+
+export default function reduceLastCommunicatedPlatformDetails(
+  state: LastCommunicatedPlatformDetails,
+  action: BaseAction,
+  currentURLPrefix: string,
+): LastCommunicatedPlatformDetails {
+  if (
+    action.type === logInActionTypes.success ||
+    action.type === siweAuthActionTypes.success ||
+    action.type === registerActionTypes.success
+  ) {
+    return {
+      ...state,
+      [currentURLPrefix]: getConfig().platformDetails,
+    };
+  }
+  if (action.type === updateLastCommunicatedPlatformDetailsActionType) {
+    return {
+      ...state,
+      ...action.payload,
+    };
+  }
+  return state;
+}
diff --git a/lib/reducers/master-reducer.js b/lib/reducers/master-reducer.js
--- a/lib/reducers/master-reducer.js
+++ b/lib/reducers/master-reducer.js
@@ -8,6 +8,7 @@
 import reduceEnabledApps from './enabled-apps-reducer.js';
 import { reduceEntryInfos } from './entry-reducer.js';
 import reduceInviteLinks from './invite-links-reducer.js';
+import reduceLastCommunicatedPlatformDetails from './last-communicated-platform-details-reducer.js';
 import reduceLifecycleState from './lifecycle-state-reducer.js';
 import { reduceLoadingStatuses } from './loading-reducer.js';
 import reduceNextLocalID from './local-id-reducer.js';
@@ -127,6 +128,11 @@
         action,
       ),
       inviteLinksStore: reduceInviteLinks(state.inviteLinksStore, action),
+      lastCommunicatedPlatformDetails: reduceLastCommunicatedPlatformDetails(
+        state.lastCommunicatedPlatformDetails,
+        action,
+        state.urlPrefix,
+      ),
     },
     storeOperations: {
       draftStoreOperations,
diff --git a/lib/shared/edit-messages-utils.js b/lib/shared/edit-messages-utils.js
--- a/lib/shared/edit-messages-utils.js
+++ b/lib/shared/edit-messages-utils.js
@@ -11,6 +11,7 @@
   SendEditMessageResult,
   RobotextMessageInfo,
   ComposableMessageInfo,
+  RawMessageInfo,
 } from '../types/message-types';
 import { messageTypes } from '../types/message-types-enum.js';
 import { threadPermissions } from '../types/thread-permission-types.js';
@@ -35,9 +36,10 @@
           targetMessageID: messageID,
           text: newText,
         });
-        return {
+
+        return ({
           newMessageInfos: result.newMessageInfos,
-        };
+        }: { +newMessageInfos: $ReadOnlyArray<RawMessageInfo> });
       })();
 
       dispatchActionPromise(sendEditMessageActionTypes, editMessagePromise);
diff --git a/lib/types/device-types.js b/lib/types/device-types.js
--- a/lib/types/device-types.js
+++ b/lib/types/device-types.js
@@ -44,3 +44,7 @@
 export type VersionResponse = {
   +codeVersion: number,
 };
+
+export type LastCommunicatedPlatformDetails = {
+  +[urlPrefix: string]: PlatformDetails,
+};
diff --git a/lib/types/redux-types.js b/lib/types/redux-types.js
--- a/lib/types/redux-types.js
+++ b/lib/types/redux-types.js
@@ -17,7 +17,10 @@
   UpdateUserAvatarResponse,
 } from './avatar-types.js';
 import type { CryptoStore } from './crypto-types.js';
-import type { VersionResponse } from './device-types.js';
+import type {
+  VersionResponse,
+  LastCommunicatedPlatformDetails,
+} from './device-types.js';
 import type { ClientDBDraftInfo, DraftStore } from './draft-types.js';
 import type { EnabledApps, SupportedApps } from './enabled-apps.js';
 import type {
@@ -134,6 +137,7 @@
   deviceToken: ?string,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
+  +lastCommunicatedPlatformDetails: LastCommunicatedPlatformDetails,
   ...
 };
 
@@ -1159,6 +1163,10 @@
       +error: true,
       +payload: Error,
       +loadingInfo: LoadingInfo,
+    }
+  | {
+      +type: 'UPDATE_LAST_COMMUNICATED_PLATFORM_DETAILS',
+      +payload: LastCommunicatedPlatformDetails,
     };
 
 export type ActionPayload = ?(Object | Array<*> | $ReadOnlyArray<*> | string);
diff --git a/native/chat/toggle-pin-modal.react.js b/native/chat/toggle-pin-modal.react.js
--- a/native/chat/toggle-pin-modal.react.js
+++ b/native/chat/toggle-pin-modal.react.js
@@ -8,6 +8,7 @@
   toggleMessagePin,
   toggleMessagePinActionTypes,
 } from 'lib/actions/thread-actions.js';
+import type { RawMessageInfo } from 'lib/types/message-types.js';
 import { type ThreadInfo } from 'lib/types/thread-types.js';
 import {
   useServerCall,
@@ -71,10 +72,10 @@
       messageID: messageInfo.id,
       action: modalInfo.action,
     });
-    return {
+    return ({
       newMessageInfos: result.newMessageInfos,
       threadID: result.threadID,
-    };
+    }: { +newMessageInfos: $ReadOnlyArray<RawMessageInfo>, +threadID: string });
   }, [callToggleMessagePin, messageInfo.id, modalInfo.action]);
 
   const onPress = React.useCallback(() => {
diff --git a/native/redux/redux-setup.js b/native/redux/redux-setup.js
--- a/native/redux/redux-setup.js
+++ b/native/redux/redux-setup.js
@@ -122,6 +122,7 @@
   inviteLinksStore: {
     links: {},
   },
+  lastCommunicatedPlatformDetails: {},
 }: AppState);
 
 function reducer(state: AppState = defaultState, action: Action) {
diff --git a/native/redux/state-types.js b/native/redux/state-types.js
--- a/native/redux/state-types.js
+++ b/native/redux/state-types.js
@@ -3,6 +3,7 @@
 import type { Orientations } from 'react-native-orientation-locker';
 import type { PersistState } from 'redux-persist/es/types.js';
 
+import type { LastCommunicatedPlatformDetails } from 'lib/types/device-types.js';
 import type { DraftStore } from 'lib/types/draft-types.js';
 import type { EnabledApps } from 'lib/types/enabled-apps.js';
 import type { EntryStore } from 'lib/types/entry-types.js';
@@ -59,4 +60,5 @@
   userPolicies: UserPolicies,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
+  +lastCommunicatedPlatformDetails: LastCommunicatedPlatformDetails,
 };
diff --git a/web/modals/chat/toggle-pin-modal.react.js b/web/modals/chat/toggle-pin-modal.react.js
--- a/web/modals/chat/toggle-pin-modal.react.js
+++ b/web/modals/chat/toggle-pin-modal.react.js
@@ -10,6 +10,7 @@
 import { useModalContext } from 'lib/components/modal-provider.react.js';
 import type { ChatMessageInfoItem } from 'lib/selectors/chat-selectors.js';
 import { modifyItemForResultScreen } from 'lib/shared/message-utils.js';
+import type { RawMessageInfo } from 'lib/types/message-types.js';
 import type { ThreadInfo } from 'lib/types/thread-types.js';
 import {
   useServerCall,
@@ -80,10 +81,13 @@
         messageID: messageInfo.id,
         action: modalInfo.action,
       });
-      return {
+      return ({
         newMessageInfos: result.newMessageInfos,
         threadID: result.threadID,
-      };
+      }: {
+        +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
+        +threadID: string,
+      });
     };
 
     dispatchActionPromise(
diff --git a/web/redux/persist.js b/web/redux/persist.js
--- a/web/redux/persist.js
+++ b/web/redux/persist.js
@@ -64,6 +64,7 @@
   'cryptoStore',
   'notifPermissionAlertInfo',
   'commServicesAccessToken',
+  'lastCommunicatedPlatformDetails',
 ];
 
 const persistConfig: PersistConfig = {
diff --git a/web/redux/redux-setup.js b/web/redux/redux-setup.js
--- a/web/redux/redux-setup.js
+++ b/web/redux/redux-setup.js
@@ -18,6 +18,7 @@
   OLMIdentityKeys,
   PickledOLMAccount,
 } from 'lib/types/crypto-types.js';
+import type { LastCommunicatedPlatformDetails } from 'lib/types/device-types.js';
 import type { DraftStore } from 'lib/types/draft-types.js';
 import type { EnabledApps } from 'lib/types/enabled-apps.js';
 import type { EntryStore } from 'lib/types/entry-types.js';
@@ -98,6 +99,7 @@
   _persist: ?PersistState,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
+  +lastCommunicatedPlatformDetails: LastCommunicatedPlatformDetails,
 };
 
 export type Action =