diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
index ed2d4583c..25a1287c5 100644
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -1,766 +1,801 @@
 // @flow
 
 import invariant from 'invariant';
 import _find from 'lodash/fp/find';
+import * as React from 'react';
 import tinycolor from 'tinycolor2';
 
+import {
+  fetchMostRecentMessagesActionTypes,
+  fetchMostRecentMessages,
+} from '../actions/message-actions';
 import {
   permissionLookup,
   getAllThreadPermissions,
   makePermissionsBlob,
 } from '../permissions/thread-permissions';
 import type { ChatThreadItem } from '../selectors/chat-selectors';
 import type {
   MultimediaMessageInfo,
   RobotextMessageInfo,
 } from '../types/message-types';
 import type { TextMessageInfo } from '../types/messages/text';
 import { userRelationshipStatus } from '../types/relationship-types';
 import {
   type RawThreadInfo,
   type ThreadInfo,
   type ThreadPermission,
   type MemberInfo,
   type ServerThreadInfo,
   type RelativeMemberInfo,
   type ThreadCurrentUserInfo,
   type RoleInfo,
   type ServerMemberInfo,
   type ThreadPermissionsInfo,
   type ThreadType,
   threadTypes,
   threadPermissions,
 } from '../types/thread-types';
 import { type UpdateInfo, updateTypes } from '../types/update-types';
 import type {
   GlobalAccountUserInfo,
   UserInfos,
   UserInfo,
 } from '../types/user-types';
+import { useDispatchActionPromise, useServerCall } from '../utils/action-utils';
 import { pluralize } from '../utils/text-utils';
 import { getMessageTitle } from './message-utils';
 import { relationshipBlockedInEitherDirection } from './relationship-utils';
+import threadWatcher from './thread-watcher';
 
 function colorIsDark(color: string) {
   return tinycolor(`#${color}`).isDark();
 }
 
 // Randomly distributed in RGB-space
 const hexNumerals = '0123456789abcdef';
 function generateRandomColor() {
   let color = '';
   for (let i = 0; i < 6; i++) {
     color += hexNumerals[Math.floor(Math.random() * 16)];
   }
   return color;
 }
 
 function generatePendingThreadColor(
   userIDs: $ReadOnlyArray<string>,
   viewerID: string,
 ) {
   const ids = [...userIDs, viewerID].sort().join('#');
 
   let hash = 0;
   for (let i = 0; i < ids.length; i++) {
     hash = 1009 * hash + ids.charCodeAt(i) * 83;
     hash %= 1000000007;
   }
   const hashString = hash.toString(16);
   return hashString.substring(hashString.length - 6).padStart(6, '8');
 }
 
 function threadHasPermission(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
   permission: ThreadPermission,
 ): boolean {
   invariant(
     !permissionsDisabledByBlock.has(permission) || threadInfo?.uiName,
     `${permission} can be disabled by a block, but threadHasPermission can't ` +
       'check for a block on RawThreadInfo. Please pass in ThreadInfo instead!',
   );
   if (!threadInfo || !threadInfo.currentUser.permissions[permission]) {
     return false;
   }
   return threadInfo.currentUser.permissions[permission].value;
 }
 
 function viewerIsMember(threadInfo: ?(ThreadInfo | RawThreadInfo)): boolean {
   return !!(
     threadInfo &&
     threadInfo.currentUser.role !== null &&
     threadInfo.currentUser.role !== undefined
   );
 }
 
 function threadIsInHome(threadInfo: ?(ThreadInfo | RawThreadInfo)): boolean {
   return !!(threadInfo && threadInfo.currentUser.subscription.home);
 }
 
 // Can have messages
 function threadInChatList(threadInfo: ?(ThreadInfo | RawThreadInfo)): boolean {
   return (
     viewerIsMember(threadInfo) &&
     threadHasPermission(threadInfo, threadPermissions.VISIBLE)
   );
 }
 
 function threadIsTopLevel(threadInfo: ?(ThreadInfo | RawThreadInfo)): boolean {
   return !!(
     threadInChatList(threadInfo) &&
     threadInfo &&
     threadInfo.type !== threadTypes.SIDEBAR
   );
 }
 
 function threadInBackgroundChatList(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
 ): boolean {
   return threadInChatList(threadInfo) && !threadIsInHome(threadInfo);
 }
 
 function threadInHomeChatList(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
 ): boolean {
   return threadInChatList(threadInfo) && threadIsInHome(threadInfo);
 }
 
 // Can have Calendar entries,
 // does appear as a top-level entity in the thread list
 function threadInFilterList(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
 ): boolean {
   return (
     threadInChatList(threadInfo) &&
     !!threadInfo &&
     threadInfo.type !== threadTypes.SIDEBAR
   );
 }
 
 function userIsMember(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
   userID: string,
 ): boolean {
   if (!threadInfo) {
     return false;
   }
   return threadInfo.members.some(
     (member) =>
       member.id === userID && member.role !== null && member.role !== undefined,
   );
 }
 
 function threadActualMembers(
   memberInfos: $ReadOnlyArray<MemberInfo>,
 ): $ReadOnlyArray<string> {
   return memberInfos
     .filter(
       (memberInfo) => memberInfo.role !== null && memberInfo.role !== undefined,
     )
     .map((memberInfo) => memberInfo.id);
 }
 
 function threadIsGroupChat(threadInfo: ThreadInfo | RawThreadInfo) {
   return (
     threadInfo.members.filter(
       (member) =>
         member.role || member.permissions[threadPermissions.VOICED]?.value,
     ).length > 2
   );
 }
 
 function threadOrParentThreadIsGroupChat(
   threadInfo: RawThreadInfo | ThreadInfo,
 ) {
   return threadInfo.members.length > 2;
 }
 
 function threadIsPending(threadID: ?string) {
   return threadID?.startsWith('pending');
 }
 
 function threadIsPersonalAndPending(threadInfo: ?(ThreadInfo | RawThreadInfo)) {
   return (
     threadInfo?.type === threadTypes.PERSONAL && threadIsPending(threadInfo?.id)
   );
 }
 
 function getPendingThreadOtherUsers(threadInfo: ThreadInfo | RawThreadInfo) {
   invariant(threadIsPending(threadInfo.id), 'Thread should be pending');
 
   const otherUserIDs = threadInfo.id.split('/')[1];
   invariant(
     otherUserIDs,
     'Pending thread should contain other members id in its id',
   );
   return otherUserIDs.split('+');
 }
 
 function getSingleOtherUser(
   threadInfo: ThreadInfo | RawThreadInfo,
   viewerID: ?string,
 ) {
   if (!viewerID) {
     return undefined;
   }
 
   const otherMemberIDs = threadInfo.members
     .map((member) => member.id)
     .filter((id) => id !== viewerID);
   if (otherMemberIDs.length !== 1) {
     return undefined;
   }
   return otherMemberIDs[0];
 }
 
 function getPendingThreadKey(memberIDs: $ReadOnlyArray<string>) {
   return [...memberIDs].sort().join('+');
 }
 
 type CreatePendingThreadArgs = {|
   +viewerID: string,
   +threadType: ThreadType,
   +members?: $ReadOnlyArray<GlobalAccountUserInfo | UserInfo>,
   +parentThreadID?: ?string,
   +threadColor?: ?string,
   +name?: ?string,
 |};
 
 function createPendingThread({
   viewerID,
   threadType,
   members,
   parentThreadID,
   threadColor,
   name,
 }: CreatePendingThreadArgs) {
   const now = Date.now();
   members = members ?? [];
   const memberIDs = members.map((member) => member.id);
   const threadID = `pending/${getPendingThreadKey(memberIDs)}`;
 
   const permissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
     [threadPermissions.VOICED]: true,
   };
 
   const membershipPermissions = getAllThreadPermissions(
     makePermissionsBlob(permissions, null, threadID, threadType),
     threadID,
   );
   const role = {
     id: `${threadID}/role`,
     name: 'Members',
     permissions,
     isDefault: true,
   };
 
   const rawThreadInfo = {
     id: threadID,
     type: threadType,
     name: name ?? null,
     description: null,
     color: threadColor ?? generatePendingThreadColor(memberIDs, viewerID),
     creationTime: now,
     parentThreadID: parentThreadID ?? null,
     members: [
       {
         id: viewerID,
         role: role.id,
         permissions: membershipPermissions,
         isSender: false,
       },
       ...members.map((member) => ({
         id: member.id,
         role: role.id,
         permissions: membershipPermissions,
         isSender: false,
       })),
     ],
     roles: {
       [role.id]: role,
     },
     currentUser: {
       role: role.id,
       permissions: membershipPermissions,
       subscription: {
         pushNotifs: false,
         home: false,
       },
       unread: false,
     },
     repliesCount: 0,
   };
 
   const userInfos = Object.fromEntries(
     members.map((member) => [member.id, member]),
   );
 
   return threadInfoFromRawThreadInfo(rawThreadInfo, viewerID, userInfos);
 }
 
 function createPendingThreadItem(
   viewerID: string,
   user: GlobalAccountUserInfo,
 ): ChatThreadItem {
   const threadInfo = createPendingThread({
     viewerID,
     threadType: threadTypes.PERSONAL,
     members: [user],
   });
 
   return {
     type: 'chatThreadItem',
     threadInfo,
     mostRecentMessageInfo: null,
     mostRecentNonLocalMessage: null,
     lastUpdatedTime: threadInfo.creationTime,
     lastUpdatedTimeIncludingSidebars: threadInfo.creationTime,
     sidebars: [],
     pendingPersonalThreadUserInfo: {
       id: user.id,
       username: user.username,
     },
   };
 }
 
 function createPendingSidebar(
   messageInfo: TextMessageInfo | MultimediaMessageInfo | RobotextMessageInfo,
   threadInfo: ThreadInfo,
   viewerID: string,
 ) {
   const { id, username } = messageInfo.creator;
   const { id: parentThreadID, color } = threadInfo;
 
   invariant(username, 'username should be set in createPendingSidebar');
   const initialMemberUserInfo: GlobalAccountUserInfo = { id, username };
   return createPendingThread({
     viewerID,
     threadType: threadTypes.SIDEBAR,
     members: [initialMemberUserInfo],
     parentThreadID,
     threadColor: color,
     name: getMessageTitle(messageInfo, threadInfo),
   });
 }
 
 function pendingThreadType(numberOfOtherMembers: number) {
   return numberOfOtherMembers === 1
     ? threadTypes.PERSONAL
     : threadTypes.CHAT_SECRET;
 }
 
 type RawThreadInfoOptions = {|
   +includeVisibilityRules?: ?boolean,
   +filterMemberList?: ?boolean,
 |};
 function rawThreadInfoFromServerThreadInfo(
   serverThreadInfo: ServerThreadInfo,
   viewerID: string,
   options?: RawThreadInfoOptions,
 ): ?RawThreadInfo {
   const includeVisibilityRules = options?.includeVisibilityRules;
   const filterMemberList = options?.filterMemberList;
 
   const members = [];
   let currentUser;
   for (const serverMember of serverThreadInfo.members) {
     if (
       filterMemberList &&
       serverMember.id !== viewerID &&
       !serverMember.role &&
       !memberHasAdminPowers(serverMember)
     ) {
       continue;
     }
     members.push({
       id: serverMember.id,
       role: serverMember.role,
       permissions: serverMember.permissions,
       isSender: serverMember.isSender,
     });
     if (serverMember.id === viewerID) {
       currentUser = {
         role: serverMember.role,
         permissions: serverMember.permissions,
         subscription: serverMember.subscription,
         unread: serverMember.unread,
       };
     }
   }
 
   let currentUserPermissions;
   if (currentUser) {
     currentUserPermissions = currentUser.permissions;
   } else {
     currentUserPermissions = getAllThreadPermissions(null, serverThreadInfo.id);
     currentUser = {
       role: null,
       permissions: currentUserPermissions,
       subscription: {
         home: false,
         pushNotifs: false,
       },
       unread: null,
     };
   }
   if (!permissionLookup(currentUserPermissions, threadPermissions.KNOW_OF)) {
     return null;
   }
 
   const rawThreadInfo: RawThreadInfo = {
     id: serverThreadInfo.id,
     type: serverThreadInfo.type,
     name: serverThreadInfo.name,
     description: serverThreadInfo.description,
     color: serverThreadInfo.color,
     creationTime: serverThreadInfo.creationTime,
     parentThreadID: serverThreadInfo.parentThreadID,
     members,
     roles: serverThreadInfo.roles,
     currentUser,
     repliesCount: serverThreadInfo.repliesCount,
   };
   const sourceMessageID = serverThreadInfo.sourceMessageID;
   if (sourceMessageID) {
     rawThreadInfo.sourceMessageID = sourceMessageID;
   }
   if (!includeVisibilityRules) {
     return rawThreadInfo;
   }
   return ({
     ...rawThreadInfo,
     visibilityRules: rawThreadInfo.type,
   }: any);
 }
 
 function robotextName(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): string {
   const threadUsernames: string[] = threadInfo.members
     .filter(
       (threadMember) =>
         threadMember.id !== viewerID &&
         (threadMember.role || memberHasAdminPowers(threadMember)),
     )
     .map(
       (threadMember) =>
         userInfos[threadMember.id] && userInfos[threadMember.id].username,
     )
     .filter(Boolean);
   if (threadUsernames.length === 0) {
     return 'just you';
   }
   return pluralize(threadUsernames);
 }
 
 function threadUIName(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): string {
   if (threadInfo.name) {
     return threadInfo.name;
   }
   return robotextName(threadInfo, viewerID, userInfos);
 }
 
 function threadInfoFromRawThreadInfo(
   rawThreadInfo: RawThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): ThreadInfo {
   const threadInfo: ThreadInfo = {
     id: rawThreadInfo.id,
     type: rawThreadInfo.type,
     name: rawThreadInfo.name,
     uiName: threadUIName(rawThreadInfo, viewerID, userInfos),
     description: rawThreadInfo.description,
     color: rawThreadInfo.color,
     creationTime: rawThreadInfo.creationTime,
     parentThreadID: rawThreadInfo.parentThreadID,
     members: rawThreadInfo.members,
     roles: rawThreadInfo.roles,
     currentUser: getCurrentUser(rawThreadInfo, viewerID, userInfos),
     repliesCount: rawThreadInfo.repliesCount,
   };
   const { sourceMessageID } = rawThreadInfo;
   if (sourceMessageID) {
     threadInfo.sourceMessageID = sourceMessageID;
   }
   return threadInfo;
 }
 
 function getCurrentUser(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): ThreadCurrentUserInfo {
   if (!threadFrozenDueToBlock(threadInfo, viewerID, userInfos)) {
     return threadInfo.currentUser;
   }
 
   return {
     ...threadInfo.currentUser,
     permissions: {
       ...threadInfo.currentUser.permissions,
       ...disabledPermissions,
     },
   };
 }
 
 function threadIsWithBlockedUserOnly(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
   checkOnlyViewerBlock?: boolean,
 ): boolean {
   if (
     threadOrParentThreadIsGroupChat(threadInfo) ||
     threadOrParentThreadHasAdminRole(threadInfo)
   ) {
     return false;
   }
 
   const otherUserID = getSingleOtherUser(threadInfo, viewerID);
   if (!otherUserID) {
     return false;
   }
   const otherUserRelationshipStatus =
     userInfos[otherUserID]?.relationshipStatus;
 
   if (checkOnlyViewerBlock) {
     return (
       otherUserRelationshipStatus === userRelationshipStatus.BLOCKED_BY_VIEWER
     );
   }
 
   return (
     !!otherUserRelationshipStatus &&
     relationshipBlockedInEitherDirection(otherUserRelationshipStatus)
   );
 }
 
 function threadFrozenDueToBlock(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): boolean {
   return threadIsWithBlockedUserOnly(threadInfo, viewerID, userInfos);
 }
 
 function threadFrozenDueToViewerBlock(
   threadInfo: RawThreadInfo | ThreadInfo,
   viewerID: ?string,
   userInfos: UserInfos,
 ): boolean {
   return threadIsWithBlockedUserOnly(threadInfo, viewerID, userInfos, true);
 }
 
 function rawThreadInfoFromThreadInfo(threadInfo: ThreadInfo): RawThreadInfo {
   const rawThreadInfo: RawThreadInfo = {
     id: threadInfo.id,
     type: threadInfo.type,
     name: threadInfo.name,
     description: threadInfo.description,
     color: threadInfo.color,
     creationTime: threadInfo.creationTime,
     parentThreadID: threadInfo.parentThreadID,
     members: threadInfo.members,
     roles: threadInfo.roles,
     currentUser: threadInfo.currentUser,
     repliesCount: threadInfo.repliesCount,
   };
   const { sourceMessageID } = threadInfo;
   if (sourceMessageID) {
     rawThreadInfo.sourceMessageID = sourceMessageID;
   }
   return rawThreadInfo;
 }
 
 const threadTypeDescriptions = {
   [threadTypes.CHAT_NESTED_OPEN]:
     'Anybody in the parent thread can see an open child thread.',
   [threadTypes.CHAT_SECRET]:
     'Only visible to its members and admins of ancestor threads.',
 };
 
 function usersInThreadInfo(threadInfo: RawThreadInfo | ThreadInfo): string[] {
   const userIDs = new Set();
   for (let member of threadInfo.members) {
     userIDs.add(member.id);
   }
   return [...userIDs];
 }
 
 function memberIsAdmin(
   memberInfo: RelativeMemberInfo | MemberInfo,
   threadInfo: ThreadInfo | RawThreadInfo,
 ) {
   return memberInfo.role && roleIsAdminRole(threadInfo.roles[memberInfo.role]);
 }
 
 // Since we don't have access to all of the ancestor ThreadInfos, we approximate
 // "parent admin" as anybody with CHANGE_ROLE permissions.
 function memberHasAdminPowers(
   memberInfo: RelativeMemberInfo | MemberInfo | ServerMemberInfo,
 ): boolean {
   return !!memberInfo.permissions[threadPermissions.CHANGE_ROLE]?.value;
 }
 
 function roleIsAdminRole(roleInfo: ?RoleInfo) {
   return roleInfo && !roleInfo.isDefault && roleInfo.name === 'Admins';
 }
 
 function threadHasAdminRole(
   threadInfo: ?(RawThreadInfo | ThreadInfo | ServerThreadInfo),
 ) {
   if (!threadInfo) {
     return false;
   }
   return _find({ name: 'Admins' })(threadInfo.roles);
 }
 
 function threadOrParentThreadHasAdminRole(
   threadInfo: RawThreadInfo | ThreadInfo,
 ) {
   return (
     threadInfo.members.filter((member) => memberHasAdminPowers(member)).length >
     0
   );
 }
 
 function identifyInvalidatedThreads(
   updateInfos: $ReadOnlyArray<UpdateInfo>,
 ): Set<string> {
   const invalidated = new Set();
   for (const updateInfo of updateInfos) {
     if (updateInfo.type === updateTypes.DELETE_THREAD) {
       invalidated.add(updateInfo.threadID);
     }
   }
   return invalidated;
 }
 
 const permissionsDisabledByBlockArray = [
   threadPermissions.VOICED,
   threadPermissions.EDIT_ENTRIES,
   threadPermissions.EDIT_THREAD,
   threadPermissions.CREATE_SUBTHREADS,
   threadPermissions.CREATE_SIDEBARS,
   threadPermissions.JOIN_THREAD,
   threadPermissions.EDIT_PERMISSIONS,
   threadPermissions.ADD_MEMBERS,
   threadPermissions.REMOVE_MEMBERS,
 ];
 
 const permissionsDisabledByBlock: Set<ThreadPermission> = new Set(
   permissionsDisabledByBlockArray,
 );
 
 const disabledPermissions: ThreadPermissionsInfo = permissionsDisabledByBlockArray.reduce(
   (permissions: ThreadPermissionsInfo, permission: string) => ({
     ...permissions,
     [permission]: { value: false, source: null },
   }),
   {},
 );
 
 // Consider updating itemHeight in native/chat/chat-thread-list.react.js
 // if you change this
 const emptyItemText =
   `Background threads are just like normal threads, except they don't ` +
   `contribute to your unread count.\n\n` +
   `To move a thread over here, switch the “Background” option in its settings.`;
 
 const threadSearchText = (
   threadInfo: RawThreadInfo | ThreadInfo,
   userInfos: UserInfos,
 ): string => {
   const searchTextArray = [];
   if (threadInfo.name) {
     searchTextArray.push(threadInfo.name);
   }
   if (threadInfo.description) {
     searchTextArray.push(threadInfo.description);
   }
   for (let member of threadInfo.members) {
     const isParentAdmin = memberHasAdminPowers(member);
     if (!member.role && !isParentAdmin) {
       continue;
     }
 
     const userInfo = userInfos[member.id];
     if (userInfo && userInfo.username) {
       searchTextArray.push(userInfo.username);
     }
   }
   return searchTextArray.join(' ');
 };
 
 function threadNoun(threadType: ThreadType) {
   return threadType === threadTypes.SIDEBAR ? 'sidebar' : 'thread';
 }
 
 function threadLabel(threadType: ThreadType) {
   if (threadType === threadTypes.CHAT_SECRET) {
     return 'Secret';
   } else if (threadType === threadTypes.PERSONAL) {
     return 'Personal';
   } else if (threadType === threadTypes.SIDEBAR) {
     return 'Sidebar';
   } else if (threadType === threadTypes.PRIVATE) {
     return 'Private';
   } else if (threadType === threadTypes.CHAT_NESTED_OPEN) {
     return 'Open';
   }
   invariant(false, `unexpected threadType ${threadType}`);
 }
 
+function useWatchThread(threadInfo: ?ThreadInfo) {
+  const dispatchActionPromise = useDispatchActionPromise();
+  const callFetchMostRecentMessages = useServerCall(fetchMostRecentMessages);
+
+  const threadID = threadInfo?.id;
+  const threadNotInChatList = !threadInChatList(threadInfo);
+  React.useEffect(() => {
+    if (threadID && threadNotInChatList) {
+      threadWatcher.watchID(threadID);
+      dispatchActionPromise(
+        fetchMostRecentMessagesActionTypes,
+        callFetchMostRecentMessages(threadID),
+      );
+    }
+    return () => {
+      if (threadID && threadNotInChatList) {
+        threadWatcher.removeID(threadID);
+      }
+    };
+  }, [
+    callFetchMostRecentMessages,
+    dispatchActionPromise,
+    threadNotInChatList,
+    threadID,
+  ]);
+}
+
 export {
   colorIsDark,
   generateRandomColor,
   generatePendingThreadColor,
   threadHasPermission,
   viewerIsMember,
   threadInChatList,
   threadIsTopLevel,
   threadInBackgroundChatList,
   threadInHomeChatList,
   threadIsInHome,
   threadInFilterList,
   userIsMember,
   threadActualMembers,
   threadIsGroupChat,
   threadIsPending,
   threadIsPersonalAndPending,
   getPendingThreadOtherUsers,
   getSingleOtherUser,
   getPendingThreadKey,
   createPendingThread,
   createPendingThreadItem,
   createPendingSidebar,
   pendingThreadType,
   getCurrentUser,
   threadFrozenDueToBlock,
   threadFrozenDueToViewerBlock,
   rawThreadInfoFromServerThreadInfo,
   robotextName,
   threadInfoFromRawThreadInfo,
   rawThreadInfoFromThreadInfo,
   threadTypeDescriptions,
   usersInThreadInfo,
   memberIsAdmin,
   memberHasAdminPowers,
   roleIsAdminRole,
   threadHasAdminRole,
   identifyInvalidatedThreads,
   permissionsDisabledByBlock,
   emptyItemText,
   threadSearchText,
   threadNoun,
   threadLabel,
+  useWatchThread,
 };
diff --git a/web/chat/chat-message-list.react.js b/web/chat/chat-message-list.react.js
index 2e7424b9d..2d7c9ffe9 100644
--- a/web/chat/chat-message-list.react.js
+++ b/web/chat/chat-message-list.react.js
@@ -1,452 +1,430 @@
 // @flow
 
 import classNames from 'classnames';
 import { detect as detectBrowser } from 'detect-browser';
 import invariant from 'invariant';
 import * as React from 'react';
 import { useDrop } from 'react-dnd';
 import { NativeTypes } from 'react-dnd-html5-backend';
 
 import {
   fetchMessagesBeforeCursorActionTypes,
   fetchMessagesBeforeCursor,
   fetchMostRecentMessagesActionTypes,
-  fetchMostRecentMessages,
 } from 'lib/actions/message-actions';
 import { registerFetchKey } from 'lib/reducers/loading-reducer';
 import { type ChatMessageItem } from 'lib/selectors/chat-selectors';
 import { threadInfoSelector } from 'lib/selectors/thread-selectors';
 import { messageKey } from 'lib/shared/message-utils';
-import { threadInChatList } from 'lib/shared/thread-utils';
-import threadWatcher from 'lib/shared/thread-watcher';
+import { useWatchThread } from 'lib/shared/thread-utils';
 import type { FetchMessageInfosPayload } from 'lib/types/message-types';
 import { type ThreadInfo } from 'lib/types/thread-types';
 import {
   type DispatchActionPromise,
   useServerCall,
   useDispatchActionPromise,
 } from 'lib/utils/action-utils';
 
 import { type InputState, InputStateContext } from '../input/input-state';
 import LoadingIndicator from '../loading-indicator.react';
 import { useTextMessageRulesFunc } from '../markdown/rules.react';
 import { useSelector } from '../redux/redux-utils';
 import { webMessageListData } from '../selectors/chat-selectors';
 import ChatInputBar from './chat-input-bar.react';
 import css from './chat-message-list.css';
 import { MessageListContext } from './message-list-types';
 import type {
   OnMessagePositionInfo,
   MessagePositionInfo,
 } from './message-position-types';
 import MessageTimestampTooltip from './message-timestamp-tooltip.react';
 import Message from './message.react';
 
 type BaseProps = {|
   +setModal: (modal: ?React.Node) => void,
 |};
 type PassedProps = {|
   ...BaseProps,
   // Redux state
   +activeChatThreadID: ?string,
   +threadInfo: ?ThreadInfo,
   +messageListData: ?$ReadOnlyArray<ChatMessageItem>,
   +startReached: boolean,
   +timeZone: ?string,
   +supportsReverseFlex: boolean,
   // Redux dispatch functions
   +dispatchActionPromise: DispatchActionPromise,
   // async functions that hit server APIs
   +fetchMessagesBeforeCursor: (
     threadID: string,
     beforeMessageID: string,
   ) => Promise<FetchMessageInfosPayload>,
-  +fetchMostRecentMessages: (
-    threadID: string,
-  ) => Promise<FetchMessageInfosPayload>,
   // withInputState
   +inputState: ?InputState,
 |};
 type ReactDnDProps = {|
   isActive: boolean,
   connectDropTarget: (node: React.Node) => React.Node,
 |};
 type Props = {|
   ...PassedProps,
   ...ReactDnDProps,
 |};
 type State = {|
   +mouseOverMessagePosition: ?OnMessagePositionInfo,
 |};
 type Snapshot = {|
   +scrollTop: number,
   +scrollHeight: number,
 |};
 class ChatMessageList extends React.PureComponent<Props, State> {
   state: State = {
     mouseOverMessagePosition: null,
   };
   container: ?HTMLDivElement;
   messageContainer: ?HTMLDivElement;
   loadingFromScroll = false;
 
   componentDidMount() {
-    const { threadInfo } = this.props;
-    if (!threadInfo || threadInChatList(threadInfo)) {
-      return;
-    }
-    threadWatcher.watchID(threadInfo.id);
-    this.props.dispatchActionPromise(
-      fetchMostRecentMessagesActionTypes,
-      this.props.fetchMostRecentMessages(threadInfo.id),
-    );
     this.scrollToBottom();
   }
 
-  componentWillUnmount() {
-    const { threadInfo } = this.props;
-    if (!threadInfo || threadInChatList(threadInfo)) {
-      return;
-    }
-    threadWatcher.removeID(threadInfo.id);
-  }
-
   getSnapshotBeforeUpdate(prevProps: Props) {
     if (
       ChatMessageList.hasNewMessage(this.props, prevProps) &&
       this.messageContainer
     ) {
       const { scrollTop, scrollHeight } = this.messageContainer;
       return { scrollTop, scrollHeight };
     }
     return null;
   }
 
   static hasNewMessage(props: Props, prevProps: Props) {
     const { messageListData } = props;
     if (!messageListData || messageListData.length === 0) {
       return false;
     }
     const prevMessageListData = prevProps.messageListData;
     if (!prevMessageListData || prevMessageListData.length === 0) {
       return true;
     }
     return (
       ChatMessageList.keyExtractor(prevMessageListData[0]) !==
       ChatMessageList.keyExtractor(messageListData[0])
     );
   }
 
   componentDidUpdate(prevProps: Props, prevState: State, snapshot: ?Snapshot) {
     const { messageListData } = this.props;
     const prevMessageListData = prevProps.messageListData;
 
     if (
       this.loadingFromScroll &&
       messageListData &&
       (!prevMessageListData ||
         messageListData.length > prevMessageListData.length ||
         this.props.startReached)
     ) {
       this.loadingFromScroll = false;
     }
 
     const { messageContainer } = this;
     if (messageContainer && prevMessageListData !== messageListData) {
       this.onScroll();
     }
 
     // We'll scroll to the bottom if the user was already scrolled to the bottom
     // before the new message, or if the new message was composed locally
     const hasNewMessage = ChatMessageList.hasNewMessage(this.props, prevProps);
     if (
       this.props.activeChatThreadID !== prevProps.activeChatThreadID ||
       (hasNewMessage &&
         messageListData &&
         messageListData[0].itemType === 'message' &&
         messageListData[0].messageInfo.localID) ||
       (hasNewMessage && snapshot && Math.abs(snapshot.scrollTop) <= 1)
     ) {
       this.scrollToBottom();
     } else if (hasNewMessage && messageContainer && snapshot) {
       const { scrollTop, scrollHeight } = messageContainer;
       if (
         scrollHeight > snapshot.scrollHeight &&
         scrollTop === snapshot.scrollTop
       ) {
         const newHeight = scrollHeight - snapshot.scrollHeight;
         const newScrollTop = Math.abs(scrollTop) + newHeight;
         if (this.props.supportsReverseFlex) {
           messageContainer.scrollTop = -1 * newScrollTop;
         } else {
           messageContainer.scrollTop = newScrollTop;
         }
       }
     }
   }
 
   scrollToBottom() {
     if (this.messageContainer) {
       this.messageContainer.scrollTop = 0;
     }
   }
 
   static keyExtractor(item: ChatMessageItem) {
     if (item.itemType === 'loader') {
       return 'loader';
     }
     return messageKey(item.messageInfo);
   }
 
   renderItem = (item) => {
     if (item.itemType === 'loader') {
       return (
         <div key="loader" className={css.loading}>
           <LoadingIndicator status="loading" size="large" color="black" />
         </div>
       );
     }
     const { threadInfo, setModal } = this.props;
     invariant(threadInfo, 'ThreadInfo should be set if messageListData is');
     return (
       <Message
         item={item}
         threadInfo={threadInfo}
         setMouseOverMessagePosition={this.setMouseOverMessagePosition}
         mouseOverMessagePosition={this.state.mouseOverMessagePosition}
         setModal={setModal}
         timeZone={this.props.timeZone}
         key={ChatMessageList.keyExtractor(item)}
       />
     );
   };
 
   setMouseOverMessagePosition = (messagePositionInfo: MessagePositionInfo) => {
     if (!this.messageContainer) {
       return;
     }
     if (messagePositionInfo.type === 'off') {
       this.setState({ mouseOverMessagePosition: null });
       return;
     }
     const containerTop = this.messageContainer.getBoundingClientRect().top;
     const mouseOverMessagePosition = {
       ...messagePositionInfo,
       messagePosition: {
         ...messagePositionInfo.messagePosition,
         top: messagePositionInfo.messagePosition.top - containerTop,
         bottom: messagePositionInfo.messagePosition.bottom - containerTop,
       },
     };
     this.setState({ mouseOverMessagePosition });
   };
 
   render() {
     const {
       messageListData,
       threadInfo,
       inputState,
       connectDropTarget,
       isActive,
     } = this.props;
     if (!messageListData) {
       return <div className={css.container} />;
     }
     invariant(threadInfo, 'ThreadInfo should be set if messageListData is');
     invariant(inputState, 'InputState should be set');
     const messages = messageListData.map(this.renderItem);
     const containerStyle = classNames({
       [css.container]: true,
       [css.activeContainer]: isActive,
     });
 
     const tooltip = (
       <MessageTimestampTooltip
         messagePositionInfo={this.state.mouseOverMessagePosition}
         timeZone={this.props.timeZone}
       />
     );
 
     const messageContainerStyle = classNames({
       [css.messageContainer]: true,
       [css.mirroredMessageContainer]: !this.props.supportsReverseFlex,
     });
     return connectDropTarget(
       <div className={containerStyle} ref={this.containerRef}>
         <div className={messageContainerStyle} ref={this.messageContainerRef}>
           {messages}
           {tooltip}
         </div>
         <ChatInputBar threadInfo={threadInfo} inputState={inputState} />
       </div>,
     );
   }
 
   containerRef = (container: ?HTMLDivElement) => {
     if (container) {
       container.addEventListener('paste', this.onPaste);
     }
     this.container = container;
   };
 
   onPaste = (e: ClipboardEvent) => {
     const { inputState } = this.props;
     if (!inputState) {
       return;
     }
     const { clipboardData } = e;
     if (!clipboardData) {
       return;
     }
     const { files } = clipboardData;
     if (files.length === 0) {
       return;
     }
     e.preventDefault();
     inputState.appendFiles([...files]);
   };
 
   messageContainerRef = (messageContainer: ?HTMLDivElement) => {
     this.messageContainer = messageContainer;
     // In case we already have all the most recent messages,
     // but they're not enough
     this.possiblyLoadMoreMessages();
     if (messageContainer) {
       messageContainer.addEventListener('scroll', this.onScroll);
     }
   };
 
   onScroll = () => {
     if (!this.messageContainer) {
       return;
     }
     if (this.state.mouseOverMessagePosition) {
       this.setState({ mouseOverMessagePosition: null });
     }
     this.possiblyLoadMoreMessages();
   };
 
   possiblyLoadMoreMessages() {
     if (!this.messageContainer) {
       return;
     }
     const { scrollTop, scrollHeight, clientHeight } = this.messageContainer;
     if (
       this.props.startReached ||
       Math.abs(scrollTop) + clientHeight + 55 < scrollHeight
     ) {
       return;
     }
     const oldestMessageServerID = this.oldestMessageServerID();
     if (!oldestMessageServerID) {
       return;
     }
     const threadID = this.props.activeChatThreadID;
     invariant(threadID, 'should be set');
     this.loadingFromScroll = true;
     this.props.dispatchActionPromise(
       fetchMessagesBeforeCursorActionTypes,
       this.props.fetchMessagesBeforeCursor(threadID, oldestMessageServerID),
     );
   }
 
   oldestMessageServerID(): ?string {
     const data = this.props.messageListData;
     invariant(data, 'should be set');
     for (let i = data.length - 1; i >= 0; i--) {
       if (data[i].itemType === 'message' && data[i].messageInfo.id) {
         return data[i].messageInfo.id;
       }
     }
     return null;
   }
 }
 
 registerFetchKey(fetchMessagesBeforeCursorActionTypes);
 registerFetchKey(fetchMostRecentMessagesActionTypes);
 
 export default React.memo<BaseProps>(function ConnectedChatMessageList(
   props: BaseProps,
 ) {
   const userAgent = useSelector((state) => state.userAgent);
   const supportsReverseFlex = React.useMemo(() => {
     const browser = detectBrowser(userAgent);
     return (
       !browser || browser.name !== 'firefox' || parseInt(browser.version) >= 81
     );
   }, [userAgent]);
 
   const messageListData = useSelector(webMessageListData);
   const timeZone = useSelector((state) => state.timeZone);
 
   const activeChatThreadID = useSelector(
     (state) => state.navInfo.activeChatThreadID,
   );
   const threadInfo = useSelector((state) => {
     const activeID = state.navInfo.activeChatThreadID;
     if (!activeID) {
       return null;
     }
     return threadInfoSelector(state)[activeID];
   });
   const startReached = useSelector((state) => {
     const activeID = state.navInfo.activeChatThreadID;
     if (!activeID) {
       return null;
     }
 
     const threadMessageInfo = state.messageStore.threads[activeID];
     if (!threadMessageInfo) {
       return null;
     }
     return threadMessageInfo.startReached;
   });
 
   const dispatchActionPromise = useDispatchActionPromise();
   const callFetchMessagesBeforeCursor = useServerCall(
     fetchMessagesBeforeCursor,
   );
-  const callFetchMostRecentMessages = useServerCall(fetchMostRecentMessages);
 
   const inputState = React.useContext(InputStateContext);
   const [dndProps, connectDropTarget] = useDrop({
     accept: NativeTypes.FILE,
     drop: (item) => {
       const { files } = item;
       if (inputState && files.length > 0) {
         inputState.appendFiles(files);
       }
     },
     collect: (monitor) => ({
       isActive: monitor.isOver() && monitor.canDrop(),
     }),
   });
 
   const getTextMessageMarkdownRules = useTextMessageRulesFunc(threadInfo?.id);
   const messageListContext = React.useMemo(() => {
     if (!getTextMessageMarkdownRules) {
       return undefined;
     }
     return { getTextMessageMarkdownRules };
   }, [getTextMessageMarkdownRules]);
 
+  useWatchThread(threadInfo);
+
   return (
     <MessageListContext.Provider value={messageListContext}>
       <ChatMessageList
         {...props}
         activeChatThreadID={activeChatThreadID}
         threadInfo={threadInfo}
         messageListData={messageListData}
         startReached={startReached}
         timeZone={timeZone}
         supportsReverseFlex={supportsReverseFlex}
         inputState={inputState}
         dispatchActionPromise={dispatchActionPromise}
         fetchMessagesBeforeCursor={callFetchMessagesBeforeCursor}
-        fetchMostRecentMessages={callFetchMostRecentMessages}
         {...dndProps}
         connectDropTarget={connectDropTarget}
       />
     </MessageListContext.Provider>
   );
 });