diff --git a/server/src/creators/message-creator.js b/server/src/creators/message-creator.js
index 27fe74ff7..29428241a 100644
--- a/server/src/creators/message-creator.js
+++ b/server/src/creators/message-creator.js
@@ -1,599 +1,599 @@
 // @flow
 
 import invariant from 'invariant';
 
 import { permissionLookup } from 'lib/permissions/thread-permissions';
 import {
   rawMessageInfoFromMessageData,
   messageTypeGeneratesNotifs,
   shimUnsupportedRawMessageInfos,
   stripLocalIDs,
 } from 'lib/shared/message-utils';
 import { messageSpecs } from 'lib/shared/messages/message-specs';
 import {
   messageTypes,
   messageDataLocalID,
   type MessageData,
   type RawMessageInfo,
 } from 'lib/types/message-types';
 import { redisMessageTypes } from 'lib/types/redis-types';
-import { threadPermissions, threadTypes } from 'lib/types/thread-types';
+import { threadPermissions } from 'lib/types/thread-types';
 import { updateTypes } from 'lib/types/update-types';
 
 import {
   dbQuery,
   SQL,
   appendSQLArray,
   mergeOrConditions,
 } from '../database/database';
 import { fetchMessageInfoForLocalID } from '../fetchers/message-fetchers';
 import { fetchOtherSessionsForViewer } from '../fetchers/session-fetchers';
 import { fetchServerThreadInfos } from '../fetchers/thread-fetchers';
 import { sendPushNotifs } from '../push/send';
 import { handleAsyncPromise } from '../responders/handlers';
 import type { Viewer } from '../session/viewer';
 import { earliestFocusedTimeConsideredCurrent } from '../shared/focused-times';
 import { publisher } from '../socket/redis';
 import { creationString } from '../utils/idempotent';
 import createIDs from './id-creator';
 import type { UpdatesForCurrentSession } from './update-creator';
 import { createUpdates } from './update-creator';
 
 type UserThreadInfo = {|
   +devices: Map<
     string,
     {|
       +deviceType: string,
       +deviceToken: string,
       +codeVersion: ?string,
     |},
   >,
   +threadIDs: Set<string>,
   +notFocusedThreadIDs: Set<string>,
   +subthreadsCanNotify: Set<string>,
   +subthreadsCanSetToUnread: Set<string>,
 |};
 
 type LatestMessagesPerUser = Map<
   string,
   $ReadOnlyMap<
     string,
     {|
       +latestMessage: string,
       +latestReadMessage?: string,
     |},
   >,
 >;
 
 type LatestMessages = $ReadOnlyArray<{|
   +userID: string,
   +threadID: string,
   +latestMessage: string,
   +latestReadMessage: ?string,
 |}>;
 
 // Does not do permission checks! (checkThreadPermission)
 async function createMessages(
   viewer: Viewer,
   messageDatas: $ReadOnlyArray<MessageData>,
   updatesForCurrentSession?: UpdatesForCurrentSession = 'return',
 ): Promise<RawMessageInfo[]> {
   if (messageDatas.length === 0) {
     return [];
   }
 
   const messageInfos: RawMessageInfo[] = [];
   const newMessageDatas: MessageData[] = [];
   const existingMessages = await Promise.all(
     messageDatas.map((messageData) =>
       fetchMessageInfoForLocalID(viewer, messageDataLocalID(messageData)),
     ),
   );
   for (let i = 0; i < existingMessages.length; i++) {
     const existingMessage = existingMessages[i];
     if (existingMessage) {
       messageInfos.push(existingMessage);
     } else {
       newMessageDatas.push(messageDatas[i]);
     }
   }
   if (newMessageDatas.length === 0) {
     return shimUnsupportedRawMessageInfos(messageInfos, viewer.platformDetails);
   }
 
   const ids = await createIDs('messages', newMessageDatas.length);
 
   const subthreadPermissionsToCheck: Set<string> = new Set();
   const threadsToMessageIndices: Map<string, number[]> = new Map();
   const messageInsertRows = [];
   for (let i = 0; i < newMessageDatas.length; i++) {
     const messageData = newMessageDatas[i];
     const threadID = messageData.threadID;
     const creatorID = messageData.creatorID;
 
     if (messageData.type === messageTypes.CREATE_SUB_THREAD) {
       subthreadPermissionsToCheck.add(messageData.childThreadID);
     }
 
     let messageIndices = threadsToMessageIndices.get(threadID);
     if (!messageIndices) {
       messageIndices = [];
       threadsToMessageIndices.set(threadID, messageIndices);
     }
     messageIndices.push(i);
 
     const content = messageSpecs[messageData.type].messageContent?.(
       messageData,
     );
 
     const creation =
       messageData.localID && viewer.hasSessionInfo
         ? creationString(viewer, messageData.localID)
         : null;
 
     messageInsertRows.push([
       ids[i],
       threadID,
       creatorID,
       messageData.type,
       content,
       messageData.time,
       creation,
     ]);
     messageInfos.push(rawMessageInfoFromMessageData(messageData, ids[i]));
   }
 
   if (viewer.isScriptViewer) {
     await postMessageSend(
       viewer,
       threadsToMessageIndices,
       subthreadPermissionsToCheck,
       stripLocalIDs(messageInfos),
       updatesForCurrentSession,
     );
   } else {
     // We aren't awaiting because this function calls external services and we
     // don't want to delay the response
     handleAsyncPromise(
       postMessageSend(
         viewer,
         threadsToMessageIndices,
         subthreadPermissionsToCheck,
         stripLocalIDs(messageInfos),
         updatesForCurrentSession,
       ),
     );
   }
 
   const messageInsertQuery = SQL`
     INSERT INTO messages(id, thread, user, type, content, time, creation)
     VALUES ${messageInsertRows}
   `;
   await Promise.all([
     dbQuery(messageInsertQuery),
     updateRepliesCount(threadsToMessageIndices, newMessageDatas),
   ]);
 
   if (updatesForCurrentSession !== 'return') {
     return [];
   }
 
   return shimUnsupportedRawMessageInfos(messageInfos, viewer.platformDetails);
 }
 
 async function updateRepliesCount(
   threadsToMessageIndices: Map<string, number[]>,
   newMessageDatas: MessageData[],
 ) {
   const updatedThreads = [];
 
   const updateThreads = SQL`
     UPDATE threads
     SET replies_count = replies_count + (CASE `;
 
   const membershipConditions = [];
   for (const [threadID, messages] of threadsToMessageIndices.entries()) {
     const newRepliesIncrease = messages
       .map((i) => newMessageDatas[i].type)
       .filter((type) => messageSpecs[type].includedInRepliesCount).length;
     if (newRepliesIncrease === 0) {
       continue;
     }
 
     updateThreads.append(SQL`
       WHEN id = ${threadID} THEN ${newRepliesIncrease}
     `);
     updatedThreads.push(threadID);
 
     const senders = messages.map((i) => newMessageDatas[i].creatorID);
     membershipConditions.push(
       SQL`thread = ${threadID} AND user IN (${senders})`,
     );
   }
   updateThreads.append(SQL`
       ELSE 0
       END)
     WHERE id IN (${updatedThreads})
-      AND type = ${threadTypes.SIDEBAR}
+      AND source_message IS NOT NULL
   `);
 
   const updateMemberships = SQL`
     UPDATE memberships
     SET sender = 1
     WHERE sender = 0 
       AND (
   `;
   updateMemberships.append(mergeOrConditions(membershipConditions));
   updateMemberships.append(SQL`
       )
   `);
 
   if (updatedThreads.length > 0) {
     const [{ threadInfos: serverThreadInfos }] = await Promise.all([
       fetchServerThreadInfos(SQL`t.id IN (${updatedThreads})`),
       dbQuery(updateThreads),
       dbQuery(updateMemberships),
     ]);
 
     const time = Date.now();
     const updates = [];
     for (const threadID in serverThreadInfos) {
       for (const member of serverThreadInfos[threadID].members) {
         updates.push({
           userID: member.id,
           time,
           threadID,
           type: updateTypes.UPDATE_THREAD,
         });
       }
     }
     await createUpdates(updates);
   }
 }
 
 // Handles:
 // (1) Sending push notifs
 // (2) Setting threads to unread and generating corresponding UpdateInfos
 // (3) Publishing to Redis so that active sockets pass on new messages
 async function postMessageSend(
   viewer: Viewer,
   threadsToMessageIndices: Map<string, number[]>,
   subthreadPermissionsToCheck: Set<string>,
   messageInfos: RawMessageInfo[],
   updatesForCurrentSession: UpdatesForCurrentSession,
 ) {
   let joinIndex = 0;
   let subthreadSelects = '';
   const subthreadJoins = [];
   for (const subthread of subthreadPermissionsToCheck) {
     const index = joinIndex++;
     subthreadSelects += `
       ,
       stm${index}.permissions AS subthread${subthread}_permissions,
       stm${index}.role AS subthread${subthread}_role
     `;
     const join = SQL`LEFT JOIN memberships `;
     join.append(`stm${index} ON stm${index}.`);
     join.append(SQL`thread = ${subthread} AND `);
     join.append(`stm${index}.user = m.user`);
     subthreadJoins.push(join);
   }
 
   const time = earliestFocusedTimeConsideredCurrent();
   const visibleExtractString = `$.${threadPermissions.VISIBLE}.value`;
   const query = SQL`
     SELECT m.user, m.thread, c.platform, c.device_token, c.versions,
       f.user AS focused_user
   `;
   query.append(subthreadSelects);
   query.append(SQL`
     FROM memberships m
     LEFT JOIN cookies c ON c.user = m.user AND c.device_token IS NOT NULL
     LEFT JOIN focused f ON f.user = m.user AND f.thread = m.thread
       AND f.time > ${time}
   `);
   appendSQLArray(query, subthreadJoins, SQL` `);
   query.append(SQL`
     WHERE (m.role > 0 OR f.user IS NOT NULL) AND
       JSON_EXTRACT(m.permissions, ${visibleExtractString}) IS TRUE AND
       m.thread IN (${[...threadsToMessageIndices.keys()]})
   `);
 
   const perUserInfo = new Map<string, UserThreadInfo>();
   const [result] = await dbQuery(query);
   for (const row of result) {
     const userID = row.user.toString();
     const threadID = row.thread.toString();
     const deviceToken = row.device_token;
     const focusedUser = !!row.focused_user;
     const { platform, versions } = row;
     let thisUserInfo = perUserInfo.get(userID);
     if (!thisUserInfo) {
       thisUserInfo = {
         devices: new Map(),
         threadIDs: new Set(),
         notFocusedThreadIDs: new Set(),
         subthreadsCanNotify: new Set(),
         subthreadsCanSetToUnread: new Set(),
       };
       perUserInfo.set(userID, thisUserInfo);
       // Subthread info will be the same for each subthread, so we only parse
       // it once
       for (const subthread of subthreadPermissionsToCheck) {
         const isSubthreadMember = row[`subthread${subthread}_role`] > 0;
         const permissions = row[`subthread${subthread}_permissions`];
         const canSeeSubthread = permissionLookup(
           permissions,
           threadPermissions.KNOW_OF,
         );
         if (!canSeeSubthread) {
           continue;
         }
         thisUserInfo.subthreadsCanSetToUnread.add(subthread);
         // Only include the notification from the superthread if there is no
         // notification from the subthread
         if (
           !isSubthreadMember ||
           !permissionLookup(permissions, threadPermissions.VISIBLE)
         ) {
           thisUserInfo.subthreadsCanNotify.add(subthread);
         }
       }
     }
     if (deviceToken) {
       thisUserInfo.devices.set(deviceToken, {
         deviceType: platform,
         deviceToken,
         codeVersion: versions ? versions.codeVersion : null,
       });
     }
     thisUserInfo.threadIDs.add(threadID);
     if (!focusedUser) {
       thisUserInfo.notFocusedThreadIDs.add(threadID);
     }
   }
 
   const pushInfo = {};
   const messageInfosPerUser = {};
   const latestMessagesPerUser: LatestMessagesPerUser = new Map();
   for (const pair of perUserInfo) {
     const [userID, preUserPushInfo] = pair;
     const { subthreadsCanNotify } = preUserPushInfo;
     const userPushInfo = {
       devices: [...preUserPushInfo.devices.values()],
       messageInfos: [],
     };
 
     for (const threadID of preUserPushInfo.notFocusedThreadIDs) {
       const messageIndices = threadsToMessageIndices.get(threadID);
       invariant(messageIndices, `indices should exist for thread ${threadID}`);
       for (const messageIndex of messageIndices) {
         const messageInfo = messageInfos[messageIndex];
         if (
           (messageInfo.type !== messageTypes.CREATE_SUB_THREAD ||
             subthreadsCanNotify.has(messageInfo.childThreadID)) &&
           messageTypeGeneratesNotifs(messageInfo.type) &&
           messageInfo.creatorID !== userID
         ) {
           userPushInfo.messageInfos.push(messageInfo);
         }
       }
     }
     if (
       userPushInfo.devices.length > 0 &&
       userPushInfo.messageInfos.length > 0
     ) {
       pushInfo[userID] = userPushInfo;
     }
     const userMessageInfos = [];
     for (const threadID of preUserPushInfo.threadIDs) {
       const messageIndices = threadsToMessageIndices.get(threadID);
       invariant(messageIndices, `indices should exist for thread ${threadID}`);
       for (const messageIndex of messageIndices) {
         const messageInfo = messageInfos[messageIndex];
         userMessageInfos.push(messageInfo);
       }
     }
     if (userMessageInfos.length > 0) {
       messageInfosPerUser[userID] = userMessageInfos;
     }
 
     latestMessagesPerUser.set(
       userID,
       determineLatestMessagesPerThread(
         preUserPushInfo,
         userID,
         threadsToMessageIndices,
         messageInfos,
       ),
     );
   }
 
   const latestMessages = flattenLatestMessagesPerUser(latestMessagesPerUser);
 
   await Promise.all([
     createReadStatusUpdates(latestMessages),
     redisPublish(viewer, messageInfosPerUser, updatesForCurrentSession),
     updateLatestMessages(latestMessages),
   ]);
 
   await sendPushNotifs(pushInfo);
 }
 
 async function redisPublish(
   viewer: Viewer,
   messageInfosPerUser: { [userID: string]: $ReadOnlyArray<RawMessageInfo> },
   updatesForCurrentSession: UpdatesForCurrentSession,
 ) {
   const avoidBroadcastingToCurrentSession =
     viewer.hasSessionInfo && updatesForCurrentSession !== 'broadcast';
   for (const userID in messageInfosPerUser) {
     if (userID === viewer.userID && avoidBroadcastingToCurrentSession) {
       continue;
     }
     const messageInfos = messageInfosPerUser[userID];
     publisher.sendMessage(
       { userID },
       {
         type: redisMessageTypes.NEW_MESSAGES,
         messages: messageInfos,
       },
     );
   }
   const viewerMessageInfos = messageInfosPerUser[viewer.userID];
   if (!viewerMessageInfos || !avoidBroadcastingToCurrentSession) {
     return;
   }
   const sessionIDs = await fetchOtherSessionsForViewer(viewer);
   for (const sessionID of sessionIDs) {
     publisher.sendMessage(
       { userID: viewer.userID, sessionID },
       {
         type: redisMessageTypes.NEW_MESSAGES,
         messages: viewerMessageInfos,
       },
     );
   }
 }
 
 function determineLatestMessagesPerThread(
   preUserPushInfo: UserThreadInfo,
   userID: string,
   threadsToMessageIndices: $ReadOnlyMap<string, $ReadOnlyArray<number>>,
   messageInfos: $ReadOnlyArray<RawMessageInfo>,
 ) {
   const {
     threadIDs,
     notFocusedThreadIDs,
     subthreadsCanSetToUnread,
   } = preUserPushInfo;
   const latestMessagesPerThread = new Map();
   for (const threadID of threadIDs) {
     const messageIndices = threadsToMessageIndices.get(threadID);
     invariant(messageIndices, `indices should exist for thread ${threadID}`);
     for (const messageIndex of messageIndices) {
       const messageInfo = messageInfos[messageIndex];
       if (
         messageInfo.type === messageTypes.CREATE_SUB_THREAD &&
         !subthreadsCanSetToUnread.has(messageInfo.childThreadID)
       ) {
         continue;
       }
 
       const messageID = messageInfo.id;
       invariant(
         messageID,
         'message ID should exist in determineLatestMessagesPerThread',
       );
 
       if (
         notFocusedThreadIDs.has(threadID) &&
         messageInfo.creatorID !== userID
       ) {
         latestMessagesPerThread.set(threadID, {
           latestMessage: messageID,
         });
       } else {
         latestMessagesPerThread.set(threadID, {
           latestMessage: messageID,
           latestReadMessage: messageID,
         });
       }
     }
   }
   return latestMessagesPerThread;
 }
 
 function flattenLatestMessagesPerUser(
   latestMessagesPerUser: LatestMessagesPerUser,
 ): LatestMessages {
   const result = [];
   for (const [userID, latestMessagesPerThread] of latestMessagesPerUser) {
     for (const [threadID, latestMessages] of latestMessagesPerThread) {
       result.push({
         userID,
         threadID,
         latestMessage: latestMessages.latestMessage,
         latestReadMessage: latestMessages.latestReadMessage,
       });
     }
   }
   return result;
 }
 
 async function createReadStatusUpdates(latestMessages: LatestMessages) {
   const now = Date.now();
   const readStatusUpdates = latestMessages
     .filter((message) => !message.latestReadMessage)
     .map(({ userID, threadID }) => ({
       type: updateTypes.UPDATE_THREAD_READ_STATUS,
       userID,
       time: now,
       threadID,
       unread: true,
     }));
 
   if (readStatusUpdates.length === 0) {
     return;
   }
 
   return await createUpdates(readStatusUpdates);
 }
 
 function updateLatestMessages(latestMessages: LatestMessages) {
   if (latestMessages.length === 0) {
     return;
   }
 
   const query = SQL`
     UPDATE memberships
     SET 
   `;
 
   const lastMessageExpression = SQL`
     last_message = GREATEST(last_message, CASE 
   `;
   const lastReadMessageExpression = SQL`
     , last_read_message = GREATEST(last_read_message, CASE 
   `;
   let shouldUpdateLastReadMessage = false;
   for (const {
     userID,
     threadID,
     latestMessage,
     latestReadMessage,
   } of latestMessages) {
     lastMessageExpression.append(SQL`
       WHEN user = ${userID} AND thread = ${threadID} THEN ${latestMessage}
     `);
     if (latestReadMessage) {
       shouldUpdateLastReadMessage = true;
       lastReadMessageExpression.append(SQL`
         WHEN user = ${userID} AND thread = ${threadID} THEN ${latestReadMessage}
       `);
     }
   }
   lastMessageExpression.append(SQL`
     ELSE last_message
     END)
   `);
   lastReadMessageExpression.append(SQL`
     ELSE last_read_message
     END)
   `);
 
   const conditions = latestMessages.map(
     ({ userID, threadID }) => SQL`(user = ${userID} AND thread = ${threadID})`,
   );
 
   query.append(lastMessageExpression);
   if (shouldUpdateLastReadMessage) {
     query.append(lastReadMessageExpression);
   }
   query.append(SQL`WHERE `);
   query.append(mergeOrConditions(conditions));
 
   return dbQuery(query);
 }
 
 export default createMessages;
diff --git a/server/src/scripts/setup-sidebars.js b/server/src/scripts/setup-sidebars.js
index 5faf71ca5..da5c28383 100644
--- a/server/src/scripts/setup-sidebars.js
+++ b/server/src/scripts/setup-sidebars.js
@@ -1,126 +1,125 @@
 // @flow
 
 import { messageSpecs } from 'lib/shared/messages/message-specs';
 import { messageTypes } from 'lib/types/message-types';
-import { threadTypes } from 'lib/types/thread-types';
 import { updateTypes } from 'lib/types/update-types';
 
 import { createUpdates } from '../creators/update-creator';
 import { dbQuery, mergeOrConditions, SQL } from '../database/database';
 import { main } from './utils';
 
 async function addRepliesCountColumn() {
   const update = SQL`
     ALTER TABLE threads
     ADD replies_count INT UNSIGNED NOT NULL DEFAULT 0
   `;
 
   try {
     await dbQuery(update);
   } catch (e) {
     console.log(e, 'replies-count column already exists');
   }
 }
 
 async function addSenderColumn() {
   const update = SQL`
     ALTER TABLE memberships
     ADD sender TINYINT(1) UNSIGNED NOT NULL DEFAULT 0
   `;
 
   try {
     await dbQuery(update);
   } catch (e) {
     console.log(e, 'sender column already exists');
   }
 }
 
 async function computeRepliesCount() {
   const includedMessageTypes = Object.keys(messageTypes)
     .map((key) => messageTypes[key])
     .filter((type) => messageSpecs[type].includedInRepliesCount);
 
   const sidebarMembersQuery = SQL`
     SELECT t.id AS threadID, m.user AS userID
     FROM threads t
     INNER JOIN memberships m ON t.id = m.thread
-    WHERE t.type = ${threadTypes.SIDEBAR}
+    WHERE t.source_message IS NOT NULL
       AND m.role >= 0
   `;
   const readCountUpdate = SQL`
     UPDATE threads t
     INNER JOIN (
       SELECT thread AS threadID, COUNT(*) AS count
       FROM messages
       WHERE type IN (${includedMessageTypes})
       GROUP BY thread
     ) c ON c.threadID = t.id
     SET t.replies_count = c.count 
-    WHERE t.type = ${threadTypes.SIDEBAR}
+    WHERE t.source_message IS NOT NULL
   `;
   const [[sidebarMembers]] = await Promise.all([
     dbQuery(sidebarMembersQuery),
     dbQuery(readCountUpdate),
   ]);
 
   const time = Date.now();
   const updates = sidebarMembers.map(({ threadID, userID }) => ({
     userID,
     time,
     threadID,
     type: updateTypes.UPDATE_THREAD,
   }));
   await createUpdates(updates);
 }
 
 export async function determineSenderStatus() {
   const includedMessageTypes = Object.keys(messageTypes)
     .map((key) => messageTypes[key])
     .filter((type) => messageSpecs[type].includedInRepliesCount);
 
   const sendersQuery = SQL`
     SELECT DISTINCT m.thread AS threadID, m.user AS userID
     FROM messages m 
     WHERE m.type IN (${includedMessageTypes})  
   `;
   const [senders] = await dbQuery(sendersQuery);
 
   const conditions = senders.map(
     ({ threadID, userID }) => SQL`thread = ${threadID} AND user = ${userID}`,
   );
   const setSenders = SQL`
     UPDATE memberships m
     SET m.sender = 1
     WHERE 
   `;
   setSenders.append(mergeOrConditions(conditions));
 
   const updatedThreads = new Set(senders.map(({ threadID }) => threadID));
   const affectedMembersQuery = SQL`
     SELECT thread AS threadID, user AS userID
     FROM memberships
     WHERE thread IN (${[...updatedThreads]})
       AND role >= 0
   `;
 
   const [[affectedMembers]] = await Promise.all([
     dbQuery(affectedMembersQuery),
     dbQuery(setSenders),
   ]);
 
   const time = Date.now();
   const updates = affectedMembers.map(({ threadID, userID }) => ({
     userID,
     time,
     threadID,
     type: updateTypes.UPDATE_THREAD,
   }));
   await createUpdates(updates);
 }
 
 main([
   addRepliesCountColumn,
   addSenderColumn,
   computeRepliesCount,
   determineSenderStatus,
 ]);