diff --git a/lib/reducers/message-reducer.js b/lib/reducers/message-reducer.js
index 97db0f881..7c5ccd3f5 100644
--- a/lib/reducers/message-reducer.js
+++ b/lib/reducers/message-reducer.js
@@ -1,1398 +1,1398 @@
 // @flow
 
 import invariant from 'invariant';
 import _difference from 'lodash/fp/difference';
 import _flow from 'lodash/fp/flow';
 import _isEqual from 'lodash/fp/isEqual';
 import _keyBy from 'lodash/fp/keyBy';
 import _map from 'lodash/fp/map';
 import _mapKeys from 'lodash/fp/mapKeys';
 import _mapValues from 'lodash/fp/mapValues';
 import _omit from 'lodash/fp/omit';
 import _omitBy from 'lodash/fp/omitBy';
 import _pick from 'lodash/fp/pick';
 import _pickBy from 'lodash/fp/pickBy';
 import _uniq from 'lodash/fp/uniq';
 
 import {
   createEntryActionTypes,
   saveEntryActionTypes,
   deleteEntryActionTypes,
   restoreEntryActionTypes,
 } from '../actions/entry-actions';
 import {
   fetchMessagesBeforeCursorActionTypes,
   fetchMostRecentMessagesActionTypes,
   sendTextMessageActionTypes,
   sendMultimediaMessageActionTypes,
   saveMessagesActionType,
   processMessagesActionType,
   messageStorePruneActionType,
   createLocalMessageActionType,
   fetchSingleMostRecentMessagesFromThreadsActionTypes,
   setMessageStoreMessages,
 } from '../actions/message-actions';
 import {
   changeThreadSettingsActionTypes,
   deleteThreadActionTypes,
   leaveThreadActionTypes,
   newThreadActionTypes,
   removeUsersFromThreadActionTypes,
   changeThreadMemberRolesActionTypes,
   joinThreadActionTypes,
 } from '../actions/thread-actions';
 import { updateMultimediaMessageMediaActionType } from '../actions/upload-actions';
 import {
   logOutActionTypes,
   deleteAccountActionTypes,
   logInActionTypes,
   registerActionTypes,
 } from '../actions/user-actions';
 import { locallyUniqueToRealizedThreadIDsSelector } from '../selectors/thread-selectors';
 import {
   messageID,
   combineTruncationStatuses,
   sortMessageInfoList,
   sortMessageIDs,
   mergeThreadMessageInfos,
 } from '../shared/message-utils';
 import {
   threadHasPermission,
   threadInChatList,
   threadIsPending,
 } from '../shared/thread-utils';
 import threadWatcher from '../shared/thread-watcher';
 import { unshimMessageInfos } from '../shared/unshim-utils';
 import type { Media, Image } from '../types/media-types';
 import {
   type RawMessageInfo,
   type LocalMessageInfo,
   type MessageStore,
   type ReplaceMessageOperation,
   type MessageStoreOperation,
   type MessageTruncationStatus,
   type ThreadMessageInfo,
   type MessageTruncationStatuses,
   messageTruncationStatus,
   messageTypes,
   defaultNumberPerThread,
 } from '../types/message-types';
 import type { RawImagesMessageInfo } from '../types/messages/images';
 import type { RawMediaMessageInfo } from '../types/messages/media';
 import { type BaseAction, rehydrateActionType } from '../types/redux-types';
 import { processServerRequestsActionType } from '../types/request-types';
 import {
   fullStateSyncActionType,
   incrementalStateSyncActionType,
 } from '../types/socket-types';
 import { type RawThreadInfo, threadPermissions } from '../types/thread-types';
 import {
   updateTypes,
   type ClientUpdateInfo,
   processUpdatesActionType,
 } from '../types/update-types';
 import { setNewSessionActionType } from '../utils/action-utils';
 import { translateClientDBMessageInfosToRawMessageInfos } from '../utils/message-ops-utils';
 
 const _mapValuesWithKeys = _mapValues.convert({ cap: false });
 
 // Input must already be ordered!
-function threadsToMessageIDsFromMessageInfos(
+function mapThreadsToMessageIDsFromOrderedMessageInfos(
   orderedMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 ): { [threadID: string]: string[] } {
-  const threads: { [threadID: string]: string[] } = {};
+  const threadsToMessageIDs: { [threadID: string]: string[] } = {};
   for (const messageInfo of orderedMessageInfos) {
     const key = messageID(messageInfo);
-    if (!threads[messageInfo.threadID]) {
-      threads[messageInfo.threadID] = [key];
+    if (!threadsToMessageIDs[messageInfo.threadID]) {
+      threadsToMessageIDs[messageInfo.threadID] = [key];
     } else {
-      threads[messageInfo.threadID].push(key);
+      threadsToMessageIDs[messageInfo.threadID].push(key);
     }
   }
-  return threads;
+  return threadsToMessageIDs;
 }
 
 function isThreadWatched(
   threadID: string,
   threadInfo: ?RawThreadInfo,
   watchedIDs: $ReadOnlyArray<string>,
 ) {
   return (
     threadIsPending(threadID) ||
     (threadInfo &&
       threadHasPermission(threadInfo, threadPermissions.VISIBLE) &&
       (threadInChatList(threadInfo) || watchedIDs.includes(threadID)))
   );
 }
 
 type FreshMessageStoreResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
 };
 function freshMessageStore(
   messageInfos: $ReadOnlyArray<RawMessageInfo>,
   truncationStatus: { [threadID: string]: MessageTruncationStatus },
   currentAsOf: number,
   threadInfos: { +[threadID: string]: RawThreadInfo },
 ): FreshMessageStoreResult {
   const unshimmed = unshimMessageInfos(messageInfos);
   const orderedMessageInfos = sortMessageInfoList(unshimmed);
   const messages = _keyBy(messageID)(orderedMessageInfos);
 
   const messageStoreOperations = orderedMessageInfos.map(messageInfo => ({
     type: 'replace',
     payload: { id: messageID(messageInfo), messageInfo },
   }));
 
-  const threadsToMessageIDs = threadsToMessageIDsFromMessageInfos(
+  const threadsToMessageIDs = mapThreadsToMessageIDsFromOrderedMessageInfos(
     orderedMessageInfos,
   );
   const lastPruned = Date.now();
   const threads = _mapValuesWithKeys(
     (messageIDs: string[], threadID: string) => ({
       messageIDs,
       startReached:
         truncationStatus[threadID] === messageTruncationStatus.EXHAUSTIVE,
       lastNavigatedTo: 0,
       lastPruned,
     }),
   )(threadsToMessageIDs);
   const watchedIDs = threadWatcher.getWatchedIDs();
   for (const threadID in threadInfos) {
     const threadInfo = threadInfos[threadID];
     if (
       threads[threadID] ||
       !isThreadWatched(threadID, threadInfo, watchedIDs)
     ) {
       continue;
     }
     threads[threadID] = {
       messageIDs: [],
       startReached: false,
       lastNavigatedTo: 0,
       lastPruned,
     };
   }
   return {
     messageStoreOperations,
     messageStore: { messages, threads, local: {}, currentAsOf },
   };
 }
 
 type ReassignmentResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
   +reassignedThreadIDs: $ReadOnlyArray<string>,
 };
 
 function reassignMessagesToRealizedThreads(
   messageStore: MessageStore,
   threadInfos: { +[threadID: string]: RawThreadInfo },
 ): ReassignmentResult {
   const locallyUniqueToRealizedThreadIDs = locallyUniqueToRealizedThreadIDsSelector(
     threadInfos,
   );
 
   const messageStoreOperations: MessageStoreOperation[] = [];
   const messages = {};
   for (const storeMessageID in messageStore.messages) {
     const message = messageStore.messages[storeMessageID];
     const newThreadID = locallyUniqueToRealizedThreadIDs.get(message.threadID);
 
     messages[storeMessageID] = newThreadID
       ? {
           ...message,
           threadID: newThreadID,
           time: threadInfos[newThreadID]?.creationTime ?? message.time,
         }
       : message;
 
     if (!newThreadID) {
       continue;
     }
 
     const updateMsgOperation: ReplaceMessageOperation = {
       type: 'replace',
       payload: { id: storeMessageID, messageInfo: messages[storeMessageID] },
     };
 
     messageStoreOperations.push(updateMsgOperation);
   }
 
   const threads = {};
   const reassignedThreadIDs = [];
   for (const threadID in messageStore.threads) {
     const threadMessageInfo = messageStore.threads[threadID];
     const newThreadID = locallyUniqueToRealizedThreadIDs.get(threadID);
     if (!newThreadID) {
       threads[threadID] = threadMessageInfo;
       continue;
     }
     const realizedThread = messageStore.threads[newThreadID];
     if (!realizedThread) {
       reassignedThreadIDs.push(newThreadID);
       threads[newThreadID] = threadMessageInfo;
       continue;
     }
     threads[newThreadID] = mergeThreadMessageInfos(
       threadMessageInfo,
       realizedThread,
       messages,
     );
   }
 
   return {
     messageStoreOperations,
     messageStore: {
       ...messageStore,
       threads,
       messages,
     },
     reassignedThreadIDs,
   };
 }
 
 type MergeNewMessagesResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
 };
 // oldMessageStore is from the old state
 // newMessageInfos, truncationStatus come from server
 function mergeNewMessages(
   oldMessageStore: MessageStore,
   newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   truncationStatus: { [threadID: string]: MessageTruncationStatus },
   threadInfos: { +[threadID: string]: RawThreadInfo },
 ): MergeNewMessagesResult {
   const {
     messageStoreOperations: updateWithLatestThreadInfosOps,
     messageStore: messageStoreUpdatedWithLatestThreadInfos,
     reassignedThreadIDs,
   } = updateMessageStoreWithLatestThreadInfos(oldMessageStore, threadInfos);
 
   const messageStoreAfterUpdateOps = processMessageStoreOperations(
     oldMessageStore,
     updateWithLatestThreadInfosOps,
   );
 
   const updatedMessageStore = {
     ...messageStoreUpdatedWithLatestThreadInfos,
     messages: messageStoreAfterUpdateOps.messages,
   };
 
   const localIDsToServerIDs: Map<string, string> = new Map();
 
   const watchedThreadIDs = [
     ...threadWatcher.getWatchedIDs(),
     ...reassignedThreadIDs,
   ];
   const unshimmedNewMessages = unshimMessageInfos(newMessageInfos);
   const unshimmedNewMessagesOfWatchedThreads = unshimmedNewMessages.filter(
     msg =>
       isThreadWatched(
         msg.threadID,
         threadInfos[msg.threadID],
         watchedThreadIDs,
       ),
   );
   const orderedNewMessageInfos = _flow(
     _map((messageInfo: RawMessageInfo) => {
       const { id: inputID } = messageInfo;
       invariant(inputID, 'new messageInfos should have serverID');
       invariant(
         !threadIsPending(messageInfo.threadID),
         'new messageInfos should have realized thread id',
       );
       const currentMessageInfo = updatedMessageStore.messages[inputID];
       if (
         messageInfo.type === messageTypes.TEXT ||
         messageInfo.type === messageTypes.IMAGES ||
         messageInfo.type === messageTypes.MULTIMEDIA
       ) {
         const { localID: inputLocalID } = messageInfo;
         const currentLocalMessageInfo = inputLocalID
           ? updatedMessageStore.messages[inputLocalID]
           : null;
         if (currentMessageInfo && currentMessageInfo.localID) {
           // If the client already has a RawMessageInfo with this serverID, keep
           // any localID associated with the existing one. This is because we
           // use localIDs as React keys and changing React keys leads to loss of
           // component state. (The conditional below is for Flow)
           if (messageInfo.type === messageTypes.TEXT) {
             messageInfo = {
               ...messageInfo,
               localID: currentMessageInfo.localID,
             };
           } else if (messageInfo.type === messageTypes.MULTIMEDIA) {
             messageInfo = ({
               ...messageInfo,
               localID: currentMessageInfo.localID,
             }: RawMediaMessageInfo);
           } else {
             messageInfo = ({
               ...messageInfo,
               localID: currentMessageInfo.localID,
             }: RawImagesMessageInfo);
           }
         } else if (currentLocalMessageInfo && currentLocalMessageInfo.localID) {
           // If the client has a RawMessageInfo with this localID, but not with
           // the serverID, that means the message creation succeeded but the
           // success action never got processed. We set a key in
           // localIDsToServerIDs here to fix the messageIDs for the rest of the
           // MessageStore too. (The conditional below is for Flow)
           invariant(inputLocalID, 'inputLocalID should be set');
           localIDsToServerIDs.set(inputLocalID, inputID);
           if (messageInfo.type === messageTypes.TEXT) {
             messageInfo = {
               ...messageInfo,
               localID: currentLocalMessageInfo.localID,
             };
           } else if (messageInfo.type === messageTypes.MULTIMEDIA) {
             messageInfo = ({
               ...messageInfo,
               localID: currentLocalMessageInfo.localID,
             }: RawMediaMessageInfo);
           } else {
             messageInfo = ({
               ...messageInfo,
               localID: currentLocalMessageInfo.localID,
             }: RawImagesMessageInfo);
           }
         } else {
           // If neither the serverID nor the localID from the delivered
           // RawMessageInfo exists in the client store, then this message is
           // brand new to us. Ignore any localID provided by the server.
           // (The conditional below is for Flow)
           const { localID, ...rest } = messageInfo;
           if (rest.type === messageTypes.TEXT) {
             messageInfo = { ...rest };
           } else if (rest.type === messageTypes.MULTIMEDIA) {
             messageInfo = ({ ...rest }: RawMediaMessageInfo);
           } else {
             messageInfo = ({ ...rest }: RawImagesMessageInfo);
           }
         }
       } else if (
         currentMessageInfo &&
         messageInfo.time > currentMessageInfo.time
       ) {
         // When thick threads will be introduced it will be possible for two
         // clients to create the same message (e.g. when they create the same
         // sidebar at the same time). We're going to use deterministic ids for
         // messages which should be unique within a thread and we have to find
         // a way for clients to agree which message to keep. We can't rely on
         // always choosing incoming messages nor messages from the store,
         // because a message that is in one user's store, will be send to
         // another user. One way to deal with it is to always choose a message
         // which is older, according to its timestamp. We can use this strategy
         // only for messages that can start a thread, because for other types
         // it might break the "contiguous" property of message ids (we can
         // consider selecting younger messages in that case, but for now we use
         // an invariant).
         invariant(
           messageInfo.type === messageTypes.CREATE_SIDEBAR ||
             messageInfo.type === messageTypes.CREATE_THREAD ||
             messageInfo.type === messageTypes.SIDEBAR_SOURCE,
           `Two different messages of type ${messageInfo.type} with the same ` +
             'id found',
         );
         return currentMessageInfo;
       }
       return _isEqual(messageInfo)(currentMessageInfo)
         ? currentMessageInfo
         : messageInfo;
     }),
     sortMessageInfoList,
   )(unshimmedNewMessagesOfWatchedThreads);
 
   const newMessageOps: MessageStoreOperation[] = [];
-  const threadsToMessageIDs = threadsToMessageIDsFromMessageInfos(
+  const threadsToMessageIDs = mapThreadsToMessageIDsFromOrderedMessageInfos(
     orderedNewMessageInfos,
   );
   const oldMessageInfosToCombine = [];
   const threadsThatNeedMessageIDsResorted = [];
   const lastPruned = Date.now();
   const local = {};
   const threads = _flow(
     _mapValuesWithKeys((messageIDs: string[], threadID: string) => {
       const oldThread = updatedMessageStore.threads[threadID];
       const truncate = truncationStatus[threadID];
       if (!oldThread) {
         return {
           messageIDs,
           startReached: truncate === messageTruncationStatus.EXHAUSTIVE,
           lastNavigatedTo: 0,
           lastPruned,
         };
       }
       let oldMessageIDsUnchanged = true;
       const oldMessageIDs = oldThread.messageIDs.map(oldID => {
         const newID = localIDsToServerIDs.get(oldID);
         if (newID !== null && newID !== undefined) {
           oldMessageIDsUnchanged = false;
           return newID;
         }
         return oldID;
       });
       if (truncate === messageTruncationStatus.TRUNCATED) {
         // If the result set in the payload isn't contiguous with what we have
         // now, that means we need to dump what we have in the state and replace
         // it with the result set. We do this to achieve our two goals for the
         // messageStore: currentness and contiguousness.
         newMessageOps.push({
           type: 'remove_messages_for_threads',
           payload: { threadIDs: [threadID] },
         });
         return {
           messageIDs,
           startReached: false,
           lastNavigatedTo: oldThread.lastNavigatedTo,
           lastPruned: oldThread.lastPruned,
         };
       }
       const oldNotInNew = _difference(oldMessageIDs)(messageIDs);
       for (const id of oldNotInNew) {
         const oldMessageInfo = updatedMessageStore.messages[id];
         invariant(oldMessageInfo, `could not find ${id} in messageStore`);
         oldMessageInfosToCombine.push(oldMessageInfo);
         const localInfo = updatedMessageStore.local[id];
         if (localInfo) {
           local[id] = localInfo;
         }
       }
       const startReached =
         oldThread.startReached ||
         truncate === messageTruncationStatus.EXHAUSTIVE;
       if (_difference(messageIDs)(oldMessageIDs).length === 0) {
         if (startReached === oldThread.startReached && oldMessageIDsUnchanged) {
           return oldThread;
         }
         return {
           messageIDs: oldMessageIDs,
           startReached,
           lastNavigatedTo: oldThread.lastNavigatedTo,
           lastPruned: oldThread.lastPruned,
         };
       }
       const mergedMessageIDs = [...messageIDs, ...oldNotInNew];
       threadsThatNeedMessageIDsResorted.push(threadID);
       return {
         messageIDs: mergedMessageIDs,
         startReached,
         lastNavigatedTo: oldThread.lastNavigatedTo,
         lastPruned: oldThread.lastPruned,
       };
     }),
     _pickBy(thread => !!thread),
   )(threadsToMessageIDs);
 
   for (const threadID in updatedMessageStore.threads) {
     if (threads[threadID]) {
       continue;
     }
     let thread = updatedMessageStore.threads[threadID];
     const truncate = truncationStatus[threadID];
     if (truncate === messageTruncationStatus.EXHAUSTIVE) {
       thread = {
         ...thread,
         startReached: true,
       };
     }
     threads[threadID] = thread;
     for (const id of thread.messageIDs) {
       const messageInfo = updatedMessageStore.messages[id];
       if (messageInfo) {
         oldMessageInfosToCombine.push(messageInfo);
       }
       const localInfo = updatedMessageStore.local[id];
       if (localInfo) {
         local[id] = localInfo;
       }
     }
   }
 
   const messages = _flow(
     sortMessageInfoList,
     _keyBy(messageID),
   )([...orderedNewMessageInfos, ...oldMessageInfosToCombine]);
 
   const newMessages = _keyBy(messageID)(orderedNewMessageInfos);
   for (const id in newMessages) {
     newMessageOps.push({
       type: 'replace',
       payload: { id, messageInfo: newMessages[id] },
     });
   }
 
   if (localIDsToServerIDs.size > 0) {
     newMessageOps.push({
       type: 'remove',
       payload: { ids: [...localIDsToServerIDs.keys()] },
     });
   }
 
   for (const threadID of threadsThatNeedMessageIDsResorted) {
     threads[threadID].messageIDs = sortMessageIDs(messages)(
       threads[threadID].messageIDs,
     );
   }
 
   const currentAsOf = Math.max(
     orderedNewMessageInfos.length > 0 ? orderedNewMessageInfos[0].time : 0,
     updatedMessageStore.currentAsOf,
   );
 
   const processedMessageStore = processMessageStoreOperations(
     updatedMessageStore,
     newMessageOps,
   );
 
   return {
     messageStoreOperations: [
       ...updateWithLatestThreadInfosOps,
       ...newMessageOps,
     ],
     messageStore: {
       messages: processedMessageStore.messages,
       threads,
       local,
       currentAsOf,
     },
   };
 }
 
 type UpdateMessageStoreWithLatestThreadInfosResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
   +reassignedThreadIDs: $ReadOnlyArray<string>,
 };
 function updateMessageStoreWithLatestThreadInfos(
   messageStore: MessageStore,
   threadInfos: { +[id: string]: RawThreadInfo },
 ): UpdateMessageStoreWithLatestThreadInfosResult {
   const messageStoreOperations: MessageStoreOperation[] = [];
   const {
     messageStore: reassignedMessageStore,
     messageStoreOperations: reassignMessagesOps,
     reassignedThreadIDs,
   } = reassignMessagesToRealizedThreads(messageStore, threadInfos);
   messageStoreOperations.push(...reassignMessagesOps);
   const watchedIDs = [...threadWatcher.getWatchedIDs(), ...reassignedThreadIDs];
   const watchedThreadInfos = _pickBy((threadInfo: RawThreadInfo) =>
     isThreadWatched(threadInfo.id, threadInfo, watchedIDs),
   )(threadInfos);
 
   const filteredThreads = _pick(Object.keys(watchedThreadInfos))(
     reassignedMessageStore.threads,
   );
 
   const messageIDsToRemove = [];
   const threadsToRemoveMessagesFrom = [];
   for (const threadID in reassignedMessageStore.threads) {
     if (watchedThreadInfos[threadID]) {
       continue;
     }
     threadsToRemoveMessagesFrom.push(threadID);
     for (const id of reassignedMessageStore.threads[threadID].messageIDs) {
       messageIDsToRemove.push(id);
     }
   }
 
   for (const threadID in threadInfos) {
     const threadInfo = threadInfos[threadID];
     if (
       isThreadWatched(threadID, threadInfo, watchedIDs) &&
       !filteredThreads[threadID]
     ) {
       filteredThreads[threadID] = {
         messageIDs: [],
         // We can conclude that startReached, since no messages were returned.
         startReached: true,
         lastNavigatedTo: 0,
         lastPruned: Date.now(),
       };
     }
   }
 
   messageStoreOperations.push({
     type: 'remove_messages_for_threads',
     payload: { threadIDs: threadsToRemoveMessagesFrom },
   });
 
   return {
     messageStoreOperations,
     messageStore: {
       messages: _omit(messageIDsToRemove)(reassignedMessageStore.messages),
       threads: filteredThreads,
       local: _omit(messageIDsToRemove)(reassignedMessageStore.local),
       currentAsOf: reassignedMessageStore.currentAsOf,
     },
     reassignedThreadIDs,
   };
 }
 
 function ensureRealizedThreadIDIsUsedWhenPossible<T: RawMessageInfo>(
   payload: T,
   threadInfos: { +[id: string]: RawThreadInfo },
 ): T {
   const locallyUniqueToRealizedThreadIDs = locallyUniqueToRealizedThreadIDsSelector(
     threadInfos,
   );
   const realizedThreadID = locallyUniqueToRealizedThreadIDs.get(
     payload.threadID,
   );
   return realizedThreadID
     ? { ...payload, threadID: realizedThreadID }
     : payload;
 }
 
 function processMessageStoreOperations(
   messageStore: MessageStore,
   messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
 ): MessageStore {
   if (messageStoreOperations.length === 0) {
     return messageStore;
   }
   let processedMessages = { ...messageStore.messages };
   for (const operation of messageStoreOperations) {
     if (operation.type === 'replace') {
       processedMessages[operation.payload.id] = operation.payload.messageInfo;
     } else if (operation.type === 'remove') {
       for (const id of operation.payload.ids) {
         delete processedMessages[id];
       }
     } else if (operation.type === 'remove_messages_for_threads') {
       for (const msgID in processedMessages) {
         if (
           operation.payload.threadIDs.includes(
             processedMessages[msgID].threadID,
           )
         ) {
           delete processedMessages[msgID];
         }
       }
     } else if (operation.type === 'rekey') {
       processedMessages[operation.payload.to] =
         processedMessages[operation.payload.from];
       delete processedMessages[operation.payload.from];
     } else if (operation.type === 'remove_all') {
       processedMessages = {};
     }
   }
   return { ...messageStore, messages: processedMessages };
 }
 
 type ReduceMessageStoreResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
 };
 function reduceMessageStore(
   messageStore: MessageStore,
   action: BaseAction,
   newThreadInfos: { +[id: string]: RawThreadInfo },
 ): ReduceMessageStoreResult {
   if (action.type === logInActionTypes.success) {
     const messagesResult = action.payload.messagesResult;
     const {
       messageStoreOperations,
       messageStore: freshStore,
     } = freshMessageStore(
       messagesResult.messageInfos,
       messagesResult.truncationStatus,
       messagesResult.currentAsOf,
       newThreadInfos,
     );
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: { ...freshStore, messages: processedMessageStore.messages },
     };
   } else if (action.type === incrementalStateSyncActionType) {
     if (
       action.payload.messagesResult.rawMessageInfos.length === 0 &&
       action.payload.updatesResult.newUpdates.length === 0
     ) {
       return { messageStoreOperations: [], messageStore };
     }
 
     const messagesResult = mergeUpdatesWithMessageInfos(
       action.payload.messagesResult.rawMessageInfos,
       action.payload.updatesResult.newUpdates,
       action.payload.messagesResult.truncationStatuses,
     );
 
     return mergeNewMessages(
       messageStore,
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
     );
   } else if (action.type === processUpdatesActionType) {
     if (action.payload.updatesResult.newUpdates.length === 0) {
       return { messageStoreOperations: [], messageStore };
     }
 
     const messagesResult = mergeUpdatesWithMessageInfos(
       [],
       action.payload.updatesResult.newUpdates,
     );
 
     const {
       messageStoreOperations,
       messageStore: newMessageStore,
     } = mergeNewMessages(
       messageStore,
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
     );
     return {
       messageStoreOperations,
       messageStore: {
         messages: newMessageStore.messages,
         threads: newMessageStore.threads,
         local: newMessageStore.local,
         currentAsOf: messageStore.currentAsOf,
       },
     };
   } else if (
     action.type === fullStateSyncActionType ||
     action.type === processMessagesActionType
   ) {
     const { messagesResult } = action.payload;
     return mergeNewMessages(
       messageStore,
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
     );
   } else if (
     action.type === fetchSingleMostRecentMessagesFromThreadsActionTypes.success
   ) {
     return mergeNewMessages(
       messageStore,
       action.payload.rawMessageInfos,
       action.payload.truncationStatuses,
       newThreadInfos,
     );
   } else if (
     action.type === fetchMessagesBeforeCursorActionTypes.success ||
     action.type === fetchMostRecentMessagesActionTypes.success
   ) {
     return mergeNewMessages(
       messageStore,
       action.payload.rawMessageInfos,
       { [action.payload.threadID]: action.payload.truncationStatus },
       newThreadInfos,
     );
   } else if (
     action.type === logOutActionTypes.success ||
     action.type === deleteAccountActionTypes.success ||
     action.type === deleteThreadActionTypes.success ||
     action.type === leaveThreadActionTypes.success ||
     action.type === setNewSessionActionType
   ) {
     const {
       messageStoreOperations,
       messageStore: filteredMessageStore,
     } = updateMessageStoreWithLatestThreadInfos(messageStore, newThreadInfos);
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         ...filteredMessageStore,
         messages: processedMessageStore.messages,
       },
     };
   } else if (action.type === newThreadActionTypes.success) {
     const messagesResult = mergeUpdatesWithMessageInfos(
       action.payload.newMessageInfos,
       action.payload.updatesResult.newUpdates,
     );
     return mergeNewMessages(
       messageStore,
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
     );
   } else if (action.type === registerActionTypes.success) {
     const truncationStatuses = {};
     for (const messageInfo of action.payload.rawMessageInfos) {
       truncationStatuses[messageInfo.threadID] =
         messageTruncationStatus.EXHAUSTIVE;
     }
     return mergeNewMessages(
       messageStore,
       action.payload.rawMessageInfos,
       truncationStatuses,
       newThreadInfos,
     );
   } else if (
     action.type === changeThreadSettingsActionTypes.success ||
     action.type === removeUsersFromThreadActionTypes.success ||
     action.type === changeThreadMemberRolesActionTypes.success ||
     action.type === createEntryActionTypes.success ||
     action.type === saveEntryActionTypes.success ||
     action.type === restoreEntryActionTypes.success
   ) {
     return mergeNewMessages(
       messageStore,
       action.payload.newMessageInfos,
       { [action.payload.threadID]: messageTruncationStatus.UNCHANGED },
       newThreadInfos,
     );
   } else if (action.type === deleteEntryActionTypes.success) {
     const payload = action.payload;
     if (payload) {
       return mergeNewMessages(
         messageStore,
         payload.newMessageInfos,
         { [payload.threadID]: messageTruncationStatus.UNCHANGED },
         newThreadInfos,
       );
     }
   } else if (action.type === joinThreadActionTypes.success) {
     const messagesResult = mergeUpdatesWithMessageInfos(
       action.payload.rawMessageInfos,
       action.payload.updatesResult.newUpdates,
     );
     return mergeNewMessages(
       messageStore,
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
     );
   } else if (
     action.type === sendTextMessageActionTypes.started ||
     action.type === sendMultimediaMessageActionTypes.started
   ) {
     const payload = ensureRealizedThreadIDIsUsedWhenPossible(
       action.payload,
       newThreadInfos,
     );
     const { localID, threadID } = payload;
     invariant(localID, `localID should be set on ${action.type}`);
 
     const messageStoreOperations = [
       {
         type: 'replace',
         payload: { id: localID, messageInfo: payload },
       },
     ];
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     const now = Date.now();
     const messageIDs = messageStore.threads[threadID]?.messageIDs ?? [];
     if (messageStore.messages[localID]) {
       const messages = { ...messageStore.messages, [localID]: payload };
       const local = _pickBy(
         (localInfo: LocalMessageInfo, key: string) => key !== localID,
       )(messageStore.local);
       const thread = messageStore.threads[threadID];
       const threads = {
         ...messageStore.threads,
         [threadID]: {
           messageIDs: sortMessageIDs(messages)(messageIDs),
           startReached: thread?.startReached ?? true,
           lastNavigatedTo: thread?.lastNavigatedTo ?? now,
           lastPruned: thread?.lastPruned ?? now,
         },
       };
       return {
         messageStoreOperations,
         messageStore: {
           ...messageStore,
           messages: processedMessageStore.messages,
           threads,
           local,
         },
       };
     }
 
     for (const existingMessageID of messageIDs) {
       const existingMessageInfo = messageStore.messages[existingMessageID];
       if (existingMessageInfo && existingMessageInfo.localID === localID) {
         return { messageStoreOperations: [], messageStore };
       }
     }
 
     const threadState: ThreadMessageInfo = messageStore.threads[threadID]
       ? {
           ...messageStore.threads[threadID],
           messageIDs: [localID, ...messageIDs],
         }
       : {
           messageIDs: [localID],
           startReached: true,
           lastNavigatedTo: now,
           lastPruned: now,
         };
 
     return {
       messageStoreOperations,
       messageStore: {
         messages: processedMessageStore.messages,
         threads: {
           ...messageStore.threads,
           [threadID]: threadState,
         },
         local: messageStore.local,
         currentAsOf: messageStore.currentAsOf,
       },
     };
   } else if (
     action.type === sendTextMessageActionTypes.failed ||
     action.type === sendMultimediaMessageActionTypes.failed
   ) {
     const { localID } = action.payload;
     return {
       messageStoreOperations: [],
       messageStore: {
         messages: messageStore.messages,
         threads: messageStore.threads,
         local: {
           ...messageStore.local,
           [localID]: { sendFailed: true },
         },
         currentAsOf: messageStore.currentAsOf,
       },
     };
   } else if (
     action.type === sendTextMessageActionTypes.success ||
     action.type === sendMultimediaMessageActionTypes.success
   ) {
     const { payload } = action;
     invariant(
       !threadIsPending(payload.threadID),
       'Successful message action should have realized thread id',
     );
     const replaceMessageKey = (messageKey: string) =>
       messageKey === payload.localID ? payload.serverID : messageKey;
     let newMessages;
     const messageStoreOperations = [];
     if (messageStore.messages[payload.serverID]) {
       // If somehow the serverID got in there already, we'll just update the
       // serverID message and scrub the localID one
       newMessages = _omitBy(
         (messageInfo: RawMessageInfo) =>
           messageInfo.type === messageTypes.TEXT &&
           !messageInfo.id &&
           messageInfo.localID === payload.localID,
       )(messageStore.messages);
       messageStoreOperations.push({
         type: 'remove',
         payload: { ids: [payload.localID] },
       });
     } else if (messageStore.messages[payload.localID]) {
       // The normal case, the localID message gets replaced by the serverID one
       newMessages = _mapKeys(replaceMessageKey)(messageStore.messages);
       messageStoreOperations.push({
         type: 'rekey',
         payload: { from: payload.localID, to: payload.serverID },
       });
     } else {
       // Well this is weird, we probably got deauthorized between when the
       // action was dispatched and when we ran this reducer...
       return { messageStoreOperations, messageStore };
     }
 
     const newMessage = {
       ...newMessages[payload.serverID],
       id: payload.serverID,
       localID: payload.localID,
       time: payload.time,
     };
     newMessages[payload.serverID] = newMessage;
     messageStoreOperations.push({
       type: 'replace',
       payload: { id: payload.serverID, messageInfo: newMessage },
     });
     const threadID = payload.threadID;
     const newMessageIDs = _flow(
       _uniq,
       sortMessageIDs(newMessages),
     )(messageStore.threads[threadID].messageIDs.map(replaceMessageKey));
     const currentAsOf =
       payload.interface === 'socket'
         ? Math.max(payload.time, messageStore.currentAsOf)
         : messageStore.currentAsOf;
     const local = _pickBy(
       (localInfo: LocalMessageInfo, key: string) => key !== payload.localID,
     )(messageStore.local);
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         messages: processedMessageStore.messages,
         threads: {
           ...messageStore.threads,
           [threadID]: {
             ...messageStore.threads[threadID],
             messageIDs: newMessageIDs,
           },
         },
         local,
         currentAsOf,
       },
     };
   } else if (action.type === saveMessagesActionType) {
     const truncationStatuses = {};
     for (const messageInfo of action.payload.rawMessageInfos) {
       truncationStatuses[messageInfo.threadID] =
         messageTruncationStatus.UNCHANGED;
     }
     const {
       messageStoreOperations,
       messageStore: newMessageStore,
     } = mergeNewMessages(
       messageStore,
       action.payload.rawMessageInfos,
       truncationStatuses,
       newThreadInfos,
     );
     return {
       messageStoreOperations,
       messageStore: {
         messages: newMessageStore.messages,
         threads: newMessageStore.threads,
         local: newMessageStore.local,
         // We avoid bumping currentAsOf because notifs may include a contracted
         // RawMessageInfo, so we want to make sure we still fetch it
         currentAsOf: messageStore.currentAsOf,
       },
     };
   } else if (action.type === messageStorePruneActionType) {
     const now = Date.now();
     const messageIDsToPrune = [];
 
     const newThreads = { ...messageStore.threads };
     for (const threadID of action.payload.threadIDs) {
       let thread = newThreads[threadID];
       if (!thread) {
         continue;
       }
       thread = { ...thread, lastPruned: now };
 
       const newMessageIDs = [...thread.messageIDs];
       const removed = newMessageIDs.splice(defaultNumberPerThread);
       if (removed.length > 0) {
         thread = {
           ...thread,
           messageIDs: newMessageIDs,
           startReached: false,
         };
       }
       for (const id of removed) {
         messageIDsToPrune.push(id);
       }
 
       newThreads[threadID] = thread;
     }
 
     const messageStoreOperations = [
       {
         type: 'remove',
         payload: { ids: messageIDsToPrune },
       },
     ];
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         messages: processedMessageStore.messages,
         threads: newThreads,
         local: _omit(messageIDsToPrune)(messageStore.local),
         currentAsOf: messageStore.currentAsOf,
       },
     };
   } else if (action.type === updateMultimediaMessageMediaActionType) {
     const { messageID: id, currentMediaID, mediaUpdate } = action.payload;
     const message = messageStore.messages[id];
     invariant(message, `message with ID ${id} could not be found`);
     invariant(
       message.type === messageTypes.IMAGES ||
         message.type === messageTypes.MULTIMEDIA,
       `message with ID ${id} is not multimedia`,
     );
 
     let updatedMessage;
     let replaced = false;
     if (message.type === messageTypes.IMAGES) {
       const media: Image[] = [];
       for (const singleMedia of message.media) {
         if (singleMedia.id !== currentMediaID) {
           media.push(singleMedia);
         } else {
           let updatedMedia: Image = {
             id: mediaUpdate.id ?? singleMedia.id,
             type: 'photo',
             uri: mediaUpdate.uri ?? singleMedia.uri,
             dimensions: mediaUpdate.dimensions ?? singleMedia.dimensions,
           };
 
           if (
             'localMediaSelection' in singleMedia &&
             !('localMediaSelection' in mediaUpdate)
           ) {
             updatedMedia = {
               ...updatedMedia,
               localMediaSelection: singleMedia.localMediaSelection,
             };
           } else if (mediaUpdate.localMediaSelection) {
             updatedMedia = {
               ...updatedMedia,
               localMediaSelection: mediaUpdate.localMediaSelection,
             };
           }
 
           media.push(updatedMedia);
           replaced = true;
         }
       }
       updatedMessage = { ...message, media };
     } else {
       const media: Media[] = [];
       for (const singleMedia of message.media) {
         if (singleMedia.id !== currentMediaID) {
           media.push(singleMedia);
         } else if (
           singleMedia.type === 'photo' &&
           mediaUpdate.type === 'photo'
         ) {
           media.push({ ...singleMedia, ...mediaUpdate });
           replaced = true;
         } else if (
           singleMedia.type === 'video' &&
           mediaUpdate.type === 'video'
         ) {
           media.push({ ...singleMedia, ...mediaUpdate });
           replaced = true;
         }
       }
       updatedMessage = { ...message, media };
     }
 
     invariant(
       replaced,
       `message ${id} did not contain media with ID ${currentMediaID}`,
     );
 
     const messageStoreOperations = [
       {
         type: 'replace',
         payload: {
           id,
           messageInfo: updatedMessage,
         },
       },
     ];
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         ...messageStore,
         messages: processedMessageStore.messages,
       },
     };
   } else if (action.type === createLocalMessageActionType) {
     const messageInfo = ensureRealizedThreadIDIsUsedWhenPossible(
       action.payload,
       newThreadInfos,
     );
     const { localID, threadID } = messageInfo;
 
     const messageIDs =
       messageStore.threads[messageInfo.threadID]?.messageIDs ?? [];
     const now = Date.now();
     const threadState: ThreadMessageInfo = messageStore.threads[threadID]
       ? {
           ...messageStore.threads[threadID],
           messageIDs: [localID, ...messageIDs],
         }
       : {
           messageIDs: [localID],
           startReached: true,
           lastNavigatedTo: now,
           lastPruned: now,
         };
 
     const messageStoreOperations = [
       {
         type: 'replace',
         payload: { id: localID, messageInfo },
       },
     ];
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         ...messageStore,
         threads: {
           ...messageStore.threads,
           [threadID]: threadState,
         },
         messages: processedMessageStore.messages,
       },
     };
   } else if (action.type === rehydrateActionType) {
     // When starting the app on native, we filter out any local-only multimedia
     // messages because the relevant context is no longer available
     const { messages, threads, local } = messageStore;
 
     const newMessages = {};
     let newThreads = threads,
       newLocal = local;
     const messageIDsToBeRemoved = [];
     for (const id in messages) {
       const message = messages[id];
       if (
         (message.type !== messageTypes.IMAGES &&
           message.type !== messageTypes.MULTIMEDIA) ||
         message.id
       ) {
         newMessages[id] = message;
         continue;
       }
       messageIDsToBeRemoved.push(id);
       const { threadID } = message;
       newThreads = {
         ...newThreads,
         [threadID]: {
           ...newThreads[threadID],
           messageIDs: newThreads[threadID].messageIDs.filter(
             curMessageID => curMessageID !== id,
           ),
         },
       };
       newLocal = _pickBy(
         (localInfo: LocalMessageInfo, key: string) => key !== id,
       )(newLocal);
     }
 
     if (newThreads === threads) {
       return { messageStoreOperations: [], messageStore };
     }
 
     const messageStoreOperations: MessageStoreOperation[] = [
       {
         type: 'remove',
         payload: { ids: messageIDsToBeRemoved },
       },
     ];
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         ...messageStore,
         messages: processedMessageStore.messages,
         threads: newThreads,
         local: newLocal,
       },
     };
   } else if (action.type === processServerRequestsActionType) {
     const {
       messageStoreOperations,
       messageStore: messageStoreAfterReassignment,
     } = reassignMessagesToRealizedThreads(messageStore, newThreadInfos);
 
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
     return {
       messageStoreOperations,
       messageStore: {
         ...messageStoreAfterReassignment,
         messages: processedMessageStore.messages,
       },
     };
   } else if (action.type === setMessageStoreMessages) {
     return {
       messageStoreOperations: [],
       messageStore: {
         ...messageStore,
         messages: translateClientDBMessageInfosToRawMessageInfos(
           action.payload,
         ),
       },
     };
   }
   return { messageStoreOperations: [], messageStore };
 }
 
 type MergedUpdatesWithMessages = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
 };
 function mergeUpdatesWithMessageInfos(
   messageInfos: $ReadOnlyArray<RawMessageInfo>,
   newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   truncationStatuses?: MessageTruncationStatuses,
 ): MergedUpdatesWithMessages {
   const messageIDs = new Set(messageInfos.map(messageInfo => messageInfo.id));
   const mergedMessageInfos = [...messageInfos];
   const mergedTruncationStatuses = { ...truncationStatuses };
 
   for (const updateInfo of newUpdates) {
     if (updateInfo.type !== updateTypes.JOIN_THREAD) {
       continue;
     }
     for (const messageInfo of updateInfo.rawMessageInfos) {
       if (messageIDs.has(messageInfo.id)) {
         continue;
       }
       mergedMessageInfos.push(messageInfo);
       messageIDs.add(messageInfo.id);
     }
 
     mergedTruncationStatuses[
       updateInfo.threadInfo.id
     ] = combineTruncationStatuses(
       updateInfo.truncationStatus,
       mergedTruncationStatuses[updateInfo.threadInfo.id],
     );
   }
   return {
     rawMessageInfos: mergedMessageInfos,
     truncationStatuses: mergedTruncationStatuses,
   };
 }
 
 export { freshMessageStore, reduceMessageStore };