diff --git a/lib/selectors/thread-selectors.js b/lib/selectors/thread-selectors.js
index 6b1f99615..c49270ca5 100644
--- a/lib/selectors/thread-selectors.js
+++ b/lib/selectors/thread-selectors.js
@@ -1,463 +1,485 @@
 // @flow
 
 import _compact from 'lodash/fp/compact.js';
 import _filter from 'lodash/fp/filter.js';
 import _flow from 'lodash/fp/flow.js';
 import _map from 'lodash/fp/map.js';
 import _mapValues from 'lodash/fp/mapValues.js';
 import _orderBy from 'lodash/fp/orderBy.js';
 import _some from 'lodash/fp/some.js';
 import _sortBy from 'lodash/fp/sortBy.js';
 import _memoize from 'lodash/memoize.js';
 import { createSelector } from 'reselect';
 import { createObjectSelector } from 'reselect-map';
 
 import {
   filteredThreadIDsSelector,
   includeDeletedSelector,
 } from './calendar-filter-selectors.js';
 import { relativeMemberInfoSelectorForMembersOfThread } from './user-selectors.js';
 import {
   getAvatarForThread,
   getRandomDefaultEmojiAvatar,
 } from '../shared/avatar-utils.js';
 import { createEntryInfo } from '../shared/entry-utils.js';
 import { getMostRecentNonLocalMessageID } from '../shared/message-utils.js';
 import {
   threadInHomeChatList,
   threadInBackgroundChatList,
   threadInFilterList,
   threadInfoFromRawThreadInfo,
   threadHasPermission,
   threadInChatList,
   threadHasAdminRole,
   roleIsAdminRole,
   threadIsPending,
   getPendingThreadID,
 } from '../shared/thread-utils.js';
 import type { ClientEmojiAvatar } from '../types/avatar-types';
 import type { EntryInfo } from '../types/entry-types.js';
 import type { MessageStore, RawMessageInfo } from '../types/message-types.js';
 import type { BaseAppState } from '../types/redux-types.js';
 import { threadPermissions } from '../types/thread-permission-types.js';
 import {
   threadTypes,
   threadTypeIsCommunityRoot,
 } from '../types/thread-types-enum.js';
 import {
   type ThreadInfo,
   type RawThreadInfo,
   type RelativeMemberInfo,
   type SidebarInfo,
 } from '../types/thread-types.js';
 import { dateString, dateFromString } from '../utils/date-utils.js';
 import { values } from '../utils/objects.js';
 
 const _mapValuesWithKeys = _mapValues.convert({ cap: false });
 
 type ThreadInfoSelectorType = (state: BaseAppState<>) => {
   +[id: string]: ThreadInfo,
 };
 const threadInfoSelector: ThreadInfoSelectorType = createObjectSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
   (state: BaseAppState<>) => state.currentUserInfo && state.currentUserInfo.id,
   (state: BaseAppState<>) => state.userStore.userInfos,
   threadInfoFromRawThreadInfo,
 );
 
 const communityThreadSelector: (
   state: BaseAppState<>,
 ) => $ReadOnlyArray<ThreadInfo> = createSelector(
   threadInfoSelector,
   (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result = [];
     for (const threadID in threadInfos) {
       const threadInfo = threadInfos[threadID];
       if (!threadTypeIsCommunityRoot(threadInfo.type)) {
         continue;
       }
       result.push(threadInfo);
     }
     return result;
   },
 );
 
 const canBeOnScreenThreadInfos: (
   state: BaseAppState<>,
 ) => $ReadOnlyArray<ThreadInfo> = createSelector(
   threadInfoSelector,
   (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result = [];
     for (const threadID in threadInfos) {
       const threadInfo = threadInfos[threadID];
       if (!threadInFilterList(threadInfo)) {
         continue;
       }
       result.push(threadInfo);
     }
     return result;
   },
 );
 
 const onScreenThreadInfos: (
   state: BaseAppState<>,
 ) => $ReadOnlyArray<ThreadInfo> = createSelector(
   filteredThreadIDsSelector,
   canBeOnScreenThreadInfos,
   (
     inputThreadIDs: ?$ReadOnlySet<string>,
     threadInfos: $ReadOnlyArray<ThreadInfo>,
   ) => {
     const threadIDs = inputThreadIDs;
     if (!threadIDs) {
       return threadInfos;
     }
     return threadInfos.filter(threadInfo => threadIDs.has(threadInfo.id));
   },
 );
 
 const onScreenEntryEditableThreadInfos: (
   state: BaseAppState<>,
 ) => $ReadOnlyArray<ThreadInfo> = createSelector(
   onScreenThreadInfos,
   (threadInfos: $ReadOnlyArray<ThreadInfo>) =>
     threadInfos.filter(threadInfo =>
       threadHasPermission(threadInfo, threadPermissions.EDIT_ENTRIES),
     ),
 );
 
 const entryInfoSelector: (state: BaseAppState<>) => {
   +[id: string]: EntryInfo,
 } = createObjectSelector(
   (state: BaseAppState<>) => state.entryStore.entryInfos,
   (state: BaseAppState<>) => state.currentUserInfo && state.currentUserInfo.id,
   (state: BaseAppState<>) => state.userStore.userInfos,
   createEntryInfo,
 );
 
 // "current" means within startDate/endDate range, not deleted, and in
 // onScreenThreadInfos
 const currentDaysToEntries: (state: BaseAppState<>) => {
   +[dayString: string]: EntryInfo[],
 } = createSelector(
   entryInfoSelector,
   (state: BaseAppState<>) => state.entryStore.daysToEntries,
   (state: BaseAppState<>) => state.navInfo.startDate,
   (state: BaseAppState<>) => state.navInfo.endDate,
   onScreenThreadInfos,
   includeDeletedSelector,
   (
     entryInfos: { +[id: string]: EntryInfo },
     daysToEntries: { +[day: string]: string[] },
     startDateString: string,
     endDateString: string,
     onScreen: $ReadOnlyArray<ThreadInfo>,
     includeDeleted: boolean,
   ) => {
     const allDaysWithinRange = {},
       startDate = dateFromString(startDateString),
       endDate = dateFromString(endDateString);
     for (
       const curDate = startDate;
       curDate <= endDate;
       curDate.setDate(curDate.getDate() + 1)
     ) {
       allDaysWithinRange[dateString(curDate)] = [];
     }
     return _mapValuesWithKeys((_: string[], dayString: string) =>
       _flow(
         _map((entryID: string) => entryInfos[entryID]),
         _compact,
         _filter(
           (entryInfo: EntryInfo) =>
             (includeDeleted || !entryInfo.deleted) &&
             _some(['id', entryInfo.threadID])(onScreen),
         ),
         _sortBy('creationTime'),
       )(daysToEntries[dayString] ? daysToEntries[dayString] : []),
     )(allDaysWithinRange);
   },
 );
 
 const childThreadInfos: (state: BaseAppState<>) => {
   +[id: string]: $ReadOnlyArray<ThreadInfo>,
 } = createSelector(
   threadInfoSelector,
   (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result = {};
     for (const id in threadInfos) {
       const threadInfo = threadInfos[id];
       const parentThreadID = threadInfo.parentThreadID;
       if (parentThreadID === null || parentThreadID === undefined) {
         continue;
       }
       if (result[parentThreadID] === undefined) {
         result[parentThreadID] = [];
       }
       result[parentThreadID].push(threadInfo);
     }
     return result;
   },
 );
 
+const containedThreadInfos: (state: BaseAppState<>) => {
+  +[id: string]: $ReadOnlyArray<ThreadInfo>,
+} = createSelector(
+  threadInfoSelector,
+  (threadInfos: { +[id: string]: ThreadInfo }) => {
+    const result = {};
+    for (const id in threadInfos) {
+      const threadInfo = threadInfos[id];
+      const { containingThreadID } = threadInfo;
+      if (containingThreadID === null || containingThreadID === undefined) {
+        continue;
+      }
+      if (result[containingThreadID] === undefined) {
+        result[containingThreadID] = [];
+      }
+      result[containingThreadID].push(threadInfo);
+    }
+    return result;
+  },
+);
+
 function getMostRecentRawMessageInfo(
   threadInfo: ThreadInfo,
   messageStore: MessageStore,
 ): ?RawMessageInfo {
   const thread = messageStore.threads[threadInfo.id];
   if (!thread) {
     return null;
   }
   for (const messageID of thread.messageIDs) {
     return messageStore.messages[messageID];
   }
   return null;
 }
 
 const sidebarInfoSelector: (state: BaseAppState<>) => {
   +[id: string]: $ReadOnlyArray<SidebarInfo>,
 } = createObjectSelector(
   childThreadInfos,
   (state: BaseAppState<>) => state.messageStore,
   (childThreads: $ReadOnlyArray<ThreadInfo>, messageStore: MessageStore) => {
     const sidebarInfos = [];
     for (const childThreadInfo of childThreads) {
       if (
         !threadInChatList(childThreadInfo) ||
         childThreadInfo.type !== threadTypes.SIDEBAR
       ) {
         continue;
       }
       const mostRecentRawMessageInfo = getMostRecentRawMessageInfo(
         childThreadInfo,
         messageStore,
       );
       const lastUpdatedTime =
         mostRecentRawMessageInfo?.time ?? childThreadInfo.creationTime;
       const mostRecentNonLocalMessage = getMostRecentNonLocalMessageID(
         childThreadInfo.id,
         messageStore,
       );
       sidebarInfos.push({
         threadInfo: childThreadInfo,
         lastUpdatedTime,
         mostRecentNonLocalMessage,
       });
     }
     return _orderBy('lastUpdatedTime')('desc')(sidebarInfos);
   },
 );
 
 const unreadCount: (state: BaseAppState<>) => number = createSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
   (threadInfos: { +[id: string]: RawThreadInfo }): number =>
     values(threadInfos).filter(
       threadInfo =>
         threadInHomeChatList(threadInfo) && threadInfo.currentUser.unread,
     ).length,
 );
 
 const unreadBackgroundCount: (state: BaseAppState<>) => number = createSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
   (threadInfos: { +[id: string]: RawThreadInfo }): number =>
     values(threadInfos).filter(
       threadInfo =>
         threadInBackgroundChatList(threadInfo) && threadInfo.currentUser.unread,
     ).length,
 );
 
 const baseAncestorThreadInfos = (threadID: string) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state),
     (threadInfos: {
       +[id: string]: ThreadInfo,
     }): $ReadOnlyArray<ThreadInfo> => {
       const pathComponents: ThreadInfo[] = [];
       let node: ?ThreadInfo = threadInfos[threadID];
       while (node) {
         pathComponents.push(node);
         node = node.parentThreadID ? threadInfos[node.parentThreadID] : null;
       }
       pathComponents.reverse();
       return pathComponents;
     },
   );
 
 const ancestorThreadInfos: (
   threadID: string,
 ) => (state: BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = _memoize(
   baseAncestorThreadInfos,
 );
 
 const baseOtherUsersButNoOtherAdmins = (threadID: string) =>
   createSelector(
     (state: BaseAppState<>) => state.threadStore.threadInfos[threadID],
     relativeMemberInfoSelectorForMembersOfThread(threadID),
     (
       threadInfo: ?RawThreadInfo,
       members: $ReadOnlyArray<RelativeMemberInfo>,
     ): boolean => {
       if (!threadInfo) {
         return false;
       }
       if (!threadHasAdminRole(threadInfo)) {
         return false;
       }
       let otherUsersExist = false;
       let otherAdminsExist = false;
       for (const member of members) {
         const role = member.role;
         if (role === undefined || role === null || member.isViewer) {
           continue;
         }
         otherUsersExist = true;
         if (roleIsAdminRole(threadInfo?.roles[role])) {
           otherAdminsExist = true;
           break;
         }
       }
       return otherUsersExist && !otherAdminsExist;
     },
   );
 
 const otherUsersButNoOtherAdmins: (
   threadID: string,
 ) => (state: BaseAppState<>) => boolean = _memoize(
   baseOtherUsersButNoOtherAdmins,
 );
 
 function mostRecentlyReadThread(
   messageStore: MessageStore,
   threadInfos: { +[id: string]: RawThreadInfo },
 ): ?string {
   let mostRecent = null;
   for (const threadID in threadInfos) {
     const threadInfo = threadInfos[threadID];
     if (threadInfo.currentUser.unread) {
       continue;
     }
     const threadMessageInfo = messageStore.threads[threadID];
     if (!threadMessageInfo) {
       continue;
     }
     const mostRecentMessageTime =
       threadMessageInfo.messageIDs.length === 0
         ? threadInfo.creationTime
         : messageStore.messages[threadMessageInfo.messageIDs[0]].time;
     if (mostRecent && mostRecent.time >= mostRecentMessageTime) {
       continue;
     }
 
     const topLevelThreadID =
       threadInfo.type === threadTypes.SIDEBAR
         ? threadInfo.parentThreadID
         : threadID;
     mostRecent = { threadID: topLevelThreadID, time: mostRecentMessageTime };
   }
   return mostRecent ? mostRecent.threadID : null;
 }
 
 const mostRecentlyReadThreadSelector: (state: BaseAppState<>) => ?string =
   createSelector(
     (state: BaseAppState<>) => state.messageStore,
     (state: BaseAppState<>) => state.threadStore.threadInfos,
     mostRecentlyReadThread,
   );
 
 const threadInfoFromSourceMessageIDSelector: (state: BaseAppState<>) => {
   +[id: string]: ThreadInfo,
 } = createSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
   threadInfoSelector,
   (
     rawThreadInfos: { +[id: string]: RawThreadInfo },
     threadInfos: { +[id: string]: ThreadInfo },
   ) => {
     const pendingToRealizedThreadIDs =
       pendingToRealizedThreadIDsSelector(rawThreadInfos);
     const result = {};
     for (const realizedID of pendingToRealizedThreadIDs.values()) {
       const threadInfo = threadInfos[realizedID];
       if (threadInfo && threadInfo.sourceMessageID) {
         result[threadInfo.sourceMessageID] = threadInfo;
       }
     }
     return result;
   },
 );
 const pendingToRealizedThreadIDsSelector: (rawThreadInfos: {
   +[id: string]: RawThreadInfo,
 }) => $ReadOnlyMap<string, string> = createSelector(
   (rawThreadInfos: { +[id: string]: RawThreadInfo }) => rawThreadInfos,
   (rawThreadInfos: { +[id: string]: RawThreadInfo }) => {
     const result = new Map();
     for (const threadID in rawThreadInfos) {
       const rawThreadInfo = rawThreadInfos[threadID];
       if (threadIsPending(threadID)) {
         continue;
       }
       const actualMemberIDs = rawThreadInfo.members
         .filter(member => member.role)
         .map(member => member.id);
       const pendingThreadID = getPendingThreadID(
         rawThreadInfo.type,
         actualMemberIDs,
         rawThreadInfo.sourceMessageID,
       );
       const existingResult = result.get(pendingThreadID);
       if (
         !existingResult ||
         rawThreadInfos[existingResult].creationTime > rawThreadInfo.creationTime
       ) {
         result.set(pendingThreadID, threadID);
       }
     }
     return result;
   },
 );
 
 const baseSavedEmojiAvatarSelectorForThread = (
   threadID: string,
   containingThreadID: ?string,
 ) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state)[threadID],
     (state: BaseAppState<>) =>
       containingThreadID ? threadInfoSelector(state)[containingThreadID] : null,
     (threadInfo: ThreadInfo, containingThreadInfo: ?ThreadInfo) => {
       return () => {
         let threadAvatar = getAvatarForThread(threadInfo, containingThreadInfo);
         if (threadAvatar.type !== 'emoji') {
           threadAvatar = getRandomDefaultEmojiAvatar();
         }
         return threadAvatar;
       };
     },
   );
 
 const savedEmojiAvatarSelectorForThread: (
   threadID: string,
   containingThreadID: ?string,
 ) => (state: BaseAppState<>) => () => ClientEmojiAvatar = _memoize(
   baseSavedEmojiAvatarSelectorForThread,
 );
 
 export {
   ancestorThreadInfos,
   threadInfoSelector,
   communityThreadSelector,
   onScreenThreadInfos,
   onScreenEntryEditableThreadInfos,
   entryInfoSelector,
   currentDaysToEntries,
   childThreadInfos,
+  containedThreadInfos,
   unreadCount,
   unreadBackgroundCount,
   otherUsersButNoOtherAdmins,
   mostRecentlyReadThread,
   mostRecentlyReadThreadSelector,
   sidebarInfoSelector,
   threadInfoFromSourceMessageIDSelector,
   pendingToRealizedThreadIDsSelector,
   savedEmojiAvatarSelectorForThread,
 };