diff --git a/server/src/creators/thread-creator.js b/server/src/creators/thread-creator.js
index 4f40ad0ce..da85458b0 100644
--- a/server/src/creators/thread-creator.js
+++ b/server/src/creators/thread-creator.js
@@ -1,510 +1,508 @@
 // @flow
 
 import invariant from 'invariant';
 
 import bots from 'lib/facts/bots';
 import { relationshipBlockedInEitherDirection } from 'lib/shared/relationship-utils';
 import {
   generatePendingThreadColor,
   generateRandomColor,
 } from 'lib/shared/thread-utils';
 import { hasMinCodeVersion } from 'lib/shared/version-utils';
 import type { Shape } from 'lib/types/core';
 import { messageTypes } from 'lib/types/message-types';
 import { userRelationshipStatus } from 'lib/types/relationship-types';
 import {
   type NewThreadRequest,
   type NewThreadResponse,
   threadTypes,
   threadPermissions,
 } from 'lib/types/thread-types';
 import { ServerError } from 'lib/utils/errors';
 import { promiseAll } from 'lib/utils/promises';
 import { firstLine } from 'lib/utils/string-utils';
 
 import { dbQuery, SQL } from '../database/database';
 import { fetchMessageInfoByID } from '../fetchers/message-fetchers';
 import { fetchThreadInfos } from '../fetchers/thread-fetchers';
 import { checkThreadPermission } from '../fetchers/thread-permission-fetchers';
 import { fetchKnownUserInfos } from '../fetchers/user-fetchers';
 import type { Viewer } from '../session/viewer';
 import {
   changeRole,
   recalculateThreadPermissions,
   commitMembershipChangeset,
   setJoinsToUnread,
   getRelationshipRowsForUsers,
   getParentThreadRelationshipRowsForNewUsers,
 } from '../updaters/thread-permission-updaters';
 import createIDs from './id-creator';
 import createMessages from './message-creator';
 import { createInitialRolesForNewThread } from './role-creator';
 import type { UpdatesForCurrentSession } from './update-creator';
 
 const { squadbot } = bots;
 
 const privateThreadDescription =
   'This is your private thread, ' +
   'where you can set reminders and jot notes in private!';
 
 type CreateThreadOptions = Shape<{|
   +forceAddMembers: boolean,
   +updatesForCurrentSession: UpdatesForCurrentSession,
   +silentlyFailMembers: boolean,
 |}>;
 
 // If forceAddMembers is set, we will allow the viewer to add random users who
 // they aren't friends with. We will only fail if the viewer is trying to add
 // somebody who they have blocked or has blocked them. On the other hand, if
 // forceAddMembers is not set, we will fail if the viewer tries to add somebody
 // who they aren't friends with and doesn't have a membership row with a
 // nonnegative role for the parent thread.
 async function createThread(
   viewer: Viewer,
   request: NewThreadRequest,
   options?: CreateThreadOptions,
 ): Promise<NewThreadResponse> {
   if (!viewer.loggedIn) {
     throw new ServerError('not_logged_in');
   }
 
   const forceAddMembers = options?.forceAddMembers ?? false;
   const updatesForCurrentSession =
     options?.updatesForCurrentSession ?? 'return';
   const silentlyFailMembers = options?.silentlyFailMembers ?? false;
 
   const threadType = request.type;
   const shouldCreateRelationships =
     forceAddMembers || threadType === threadTypes.PERSONAL;
   const parentThreadID = request.parentThreadID ? request.parentThreadID : null;
   const initialMemberIDsFromRequest =
     request.initialMemberIDs && request.initialMemberIDs.length > 0
       ? request.initialMemberIDs
       : null;
   const ghostMemberIDs =
     request.ghostMemberIDs && request.ghostMemberIDs.length > 0
       ? request.ghostMemberIDs
       : null;
 
   const sourceMessageID = request.sourceMessageID
     ? request.sourceMessageID
     : null;
   invariant(
     threadType !== threadTypes.SIDEBAR || sourceMessageID,
     'sourceMessageID should be set for sidebar',
   );
 
   if (
     threadType !== threadTypes.CHAT_SECRET &&
     threadType !== threadTypes.PERSONAL &&
     threadType !== threadTypes.PRIVATE &&
     !parentThreadID
   ) {
     throw new ServerError('invalid_parameters');
   }
 
   if (
     threadType === threadTypes.PERSONAL &&
     (request.initialMemberIDs?.length !== 1 || parentThreadID)
   ) {
     throw new ServerError('invalid_parameters');
   }
 
   const checkPromises = {};
   if (parentThreadID) {
     checkPromises.parentThreadFetch = fetchThreadInfos(
       viewer,
       SQL`t.id = ${parentThreadID}`,
     );
     checkPromises.hasParentPermission = checkThreadPermission(
       viewer,
       parentThreadID,
       threadType === threadTypes.SIDEBAR
         ? threadPermissions.CREATE_SIDEBARS
         : threadPermissions.CREATE_SUBTHREADS,
     );
   }
 
   const memberIDs = [];
   if (initialMemberIDsFromRequest) {
     memberIDs.push(...initialMemberIDsFromRequest);
   }
   if (ghostMemberIDs) {
     memberIDs.push(...ghostMemberIDs);
   }
 
   if (initialMemberIDsFromRequest || ghostMemberIDs) {
     checkPromises.fetchMemberIDs = fetchKnownUserInfos(viewer, memberIDs);
   }
 
   if (sourceMessageID) {
     checkPromises.sourceMessage = fetchMessageInfoByID(viewer, sourceMessageID);
   }
 
   const {
     parentThreadFetch,
     hasParentPermission,
     fetchMemberIDs,
     sourceMessage,
   } = await promiseAll(checkPromises);
 
   let parentThreadMembers;
   if (parentThreadID) {
     invariant(parentThreadFetch, 'parentThreadFetch should be set');
     const parentThreadInfo = parentThreadFetch.threadInfos[parentThreadID];
     if (!hasParentPermission) {
       throw new ServerError('invalid_credentials');
     }
     parentThreadMembers = parentThreadInfo.members.map(
       (userInfo) => userInfo.id,
     );
   }
 
   const viewerNeedsRelationshipsWith = [];
   const silencedMemberIDs = new Set();
   if (fetchMemberIDs) {
     invariant(initialMemberIDsFromRequest || ghostMemberIDs, 'should be set');
     for (const memberID of memberIDs) {
       const member = fetchMemberIDs[memberID];
       if (
         !member &&
         shouldCreateRelationships &&
         (threadType !== threadTypes.SIDEBAR ||
           parentThreadMembers?.includes(memberID))
       ) {
         viewerNeedsRelationshipsWith.push(memberID);
         continue;
       } else if (!member && silentlyFailMembers) {
         silencedMemberIDs.add(memberID);
         continue;
       } else if (!member) {
         throw new ServerError('invalid_credentials');
       }
 
       const { relationshipStatus } = member;
       const memberRelationshipHasBlock = !!(
         relationshipStatus &&
         relationshipBlockedInEitherDirection(relationshipStatus)
       );
       if (
         relationshipStatus === userRelationshipStatus.FRIEND &&
         threadType !== threadTypes.SIDEBAR
       ) {
         continue;
       } else if (memberRelationshipHasBlock && silentlyFailMembers) {
         silencedMemberIDs.add(memberID);
       } else if (memberRelationshipHasBlock) {
         throw new ServerError('invalid_credentials');
       } else if (
         parentThreadMembers &&
         parentThreadMembers.includes(memberID)
       ) {
         continue;
       } else if (!shouldCreateRelationships && silentlyFailMembers) {
         silencedMemberIDs.add(memberID);
       } else if (!shouldCreateRelationships) {
         throw new ServerError('invalid_credentials');
       }
     }
   }
 
   const filteredInitialMemberIDs: ?$ReadOnlyArray<string> = initialMemberIDsFromRequest?.filter(
     (id) => !silencedMemberIDs.has(id),
   );
   const initialMemberIDs =
     filteredInitialMemberIDs && filteredInitialMemberIDs.length > 0
       ? filteredInitialMemberIDs
       : null;
 
   const [id] = await createIDs('threads', 1);
   const newRoles = await createInitialRolesForNewThread(id, threadType);
 
   const name = request.name ? firstLine(request.name) : null;
   const description = request.description ? request.description : null;
   let color = request.color
     ? request.color.toLowerCase()
     : generateRandomColor();
   if (threadType === threadTypes.PERSONAL) {
     color = generatePendingThreadColor(
       request.initialMemberIDs ?? [],
       viewer.id,
     );
   }
 
   const time = Date.now();
 
   const row = [
     id,
     threadType,
     name,
     description,
     viewer.userID,
     time,
     color,
     parentThreadID,
     newRoles.default.id,
     sourceMessageID,
   ];
+
+  let existingThreadQuery = null;
   if (threadType === threadTypes.PERSONAL) {
     const otherMemberID = initialMemberIDs?.[0];
     invariant(
       otherMemberID,
       'Other member id should be set for a PERSONAL thread',
     );
+    existingThreadQuery = SQL`
+      SELECT t.id 
+      FROM threads t
+      INNER JOIN memberships m1 
+        ON m1.thread = t.id AND m1.user = ${viewer.userID}
+      INNER JOIN memberships m2
+        ON m2.thread = t.id AND m2.user = ${otherMemberID}
+      WHERE t.type = ${threadTypes.PERSONAL}
+        AND m1.role != -1
+        AND m2.role != -1
+    `;
+  } else if (sourceMessageID) {
+    existingThreadQuery = SQL`
+      SELECT t.id
+      FROM threads t
+      WHERE t.source_message = ${sourceMessageID}
+    `;
+  }
+
+  if (existingThreadQuery) {
     const query = SQL`
       INSERT INTO threads(id, type, name, description, creator,
         creation_time, color, parent_thread_id, default_role, source_message)
       SELECT ${row}
-      WHERE NOT EXISTS (
-        SELECT * 
-        FROM threads t
-        INNER JOIN memberships m1 
-          ON m1.thread = t.id AND m1.user = ${viewer.userID}
-        INNER JOIN memberships m2
-          ON m2.thread = t.id AND m2.user = ${otherMemberID}
-        WHERE t.type = ${threadTypes.PERSONAL}
-          AND m1.role != -1
-          AND m2.role != -1
-      )
-    `;
+      WHERE NOT EXISTS (`;
+    query.append(existingThreadQuery).append(SQL`)`);
     const [result] = await dbQuery(query);
 
     if (result.affectedRows === 0) {
-      const personalThreadQuery = SQL`
-        SELECT t.id 
-        FROM threads t
-        INNER JOIN memberships m1 
-          ON m1.thread = t.id AND m1.user = ${viewer.userID}
-        INNER JOIN memberships m2
-          ON m2.thread = t.id AND m2.user = ${otherMemberID}
-        WHERE t.type = ${threadTypes.PERSONAL}
-          AND m1.role != -1
-          AND m2.role != -1
-      `;
       const deleteRoles = SQL`
         DELETE FROM roles
         WHERE id IN (${newRoles.default.id}, ${newRoles.creator.id})
       `;
       const deleteIDs = SQL`
         DELETE FROM ids
         WHERE id IN (${id}, ${newRoles.default.id}, ${newRoles.creator.id})
       `;
-      const [[personalThreadResult]] = await Promise.all([
-        dbQuery(personalThreadQuery),
+      const [[existingThreadResult]] = await Promise.all([
+        dbQuery(existingThreadQuery),
         dbQuery(deleteRoles),
         dbQuery(deleteIDs),
       ]);
-      invariant(
-        personalThreadResult.length > 0,
-        'PERSONAL thread should exist',
-      );
-      const personalThreadID = personalThreadResult[0].id.toString();
+      invariant(existingThreadResult.length > 0, 'thread should exist');
+      const existingThreadID = existingThreadResult[0].id.toString();
 
       return {
-        newThreadID: personalThreadID,
+        newThreadID: existingThreadID,
         updatesResult: {
           newUpdates: [],
         },
         userInfos: {},
         newMessageInfos: [],
       };
     }
   } else {
     const query = SQL`
       INSERT INTO threads(id, type, name, description, creator,
         creation_time, color, parent_thread_id, default_role, source_message)
       VALUES ${[row]}
     `;
     await dbQuery(query);
   }
 
   const [
     creatorChangeset,
     initialMembersChangeset,
     ghostMembersChangeset,
     recalculatePermissionsChangeset,
   ] = await Promise.all([
     changeRole(id, [viewer.userID], newRoles.creator.id),
     initialMemberIDs ? changeRole(id, initialMemberIDs, null) : undefined,
     ghostMemberIDs ? changeRole(id, ghostMemberIDs, -1) : undefined,
     recalculateThreadPermissions(id, threadType),
   ]);
 
   if (!creatorChangeset) {
     throw new ServerError('unknown_error');
   }
   const {
     membershipRows: creatorMembershipRows,
     relationshipRows: creatorRelationshipRows,
   } = creatorChangeset;
 
   const {
     membershipRows: recalculateMembershipRows,
     relationshipRows: recalculateRelationshipRows,
   } = recalculatePermissionsChangeset;
 
   const membershipRows = [
     ...creatorMembershipRows,
     ...recalculateMembershipRows,
   ];
   const relationshipRows = [
     ...creatorRelationshipRows,
     ...recalculateRelationshipRows,
   ];
   if (initialMemberIDs || ghostMemberIDs) {
     if (!initialMembersChangeset && !ghostMembersChangeset) {
       throw new ServerError('unknown_error');
     }
     relationshipRows.push(
       ...getRelationshipRowsForUsers(
         viewer.userID,
         viewerNeedsRelationshipsWith,
       ),
     );
     const membersMembershipRows = [];
     const membersRelationshipRows = [];
     if (initialMembersChangeset) {
       const {
         membershipRows: initialMembersMembershipRows,
         relationshipRows: initialMembersRelationshipRows,
       } = initialMembersChangeset;
       membersMembershipRows.push(...initialMembersMembershipRows);
       membersRelationshipRows.push(...initialMembersRelationshipRows);
     }
 
     if (ghostMembersChangeset) {
       const {
         membershipRows: ghostMembersMembershipRows,
         relationshipRows: ghostMembersRelationshipRows,
       } = ghostMembersChangeset;
       membersMembershipRows.push(...ghostMembersMembershipRows);
       membersRelationshipRows.push(...ghostMembersRelationshipRows);
     }
 
     const memberAndCreatorIDs = [...memberIDs, viewer.userID];
     const parentRelationshipRows = getParentThreadRelationshipRowsForNewUsers(
       id,
       recalculateMembershipRows,
       memberAndCreatorIDs,
     );
     membershipRows.push(...membersMembershipRows);
     relationshipRows.push(
       ...membersRelationshipRows,
       ...parentRelationshipRows,
     );
   }
 
   setJoinsToUnread(membershipRows, viewer.userID, id);
 
   const changeset = { membershipRows, relationshipRows };
   const {
     threadInfos,
     viewerUpdates,
     userInfos,
   } = await commitMembershipChangeset(viewer, changeset, {
     updatesForCurrentSession,
   });
 
   const initialMemberAndCreatorIDs = initialMemberIDs
     ? [...initialMemberIDs, viewer.userID]
     : [viewer.userID];
   const messageDatas = [];
   if (threadType !== threadTypes.SIDEBAR) {
     messageDatas.push({
       type: messageTypes.CREATE_THREAD,
       threadID: id,
       creatorID: viewer.userID,
       time,
       initialThreadState: {
         type: threadType,
         name,
         parentThreadID,
         color,
         memberIDs: initialMemberAndCreatorIDs,
       },
     });
   } else {
     invariant(parentThreadID, 'parentThreadID should be set for sidebar');
     if (!sourceMessage || sourceMessage.type === messageTypes.SIDEBAR_SOURCE) {
       throw new ServerError('invalid_parameters');
     }
 
     messageDatas.push(
       {
         type: messageTypes.SIDEBAR_SOURCE,
         threadID: id,
         creatorID: viewer.userID,
         time,
         sourceMessage,
       },
       {
         type: messageTypes.CREATE_SIDEBAR,
         threadID: id,
         creatorID: viewer.userID,
         time,
         sourceMessageAuthorID: sourceMessage.creatorID,
         initialThreadState: {
           name,
           parentThreadID,
           color,
           memberIDs: initialMemberAndCreatorIDs,
         },
       },
     );
   }
 
   if (parentThreadID && threadType !== threadTypes.SIDEBAR) {
     messageDatas.push({
       type: messageTypes.CREATE_SUB_THREAD,
       threadID: parentThreadID,
       creatorID: viewer.userID,
       time,
       childThreadID: id,
     });
   }
   const newMessageInfos = await createMessages(
     viewer,
     messageDatas,
     updatesForCurrentSession,
   );
 
   if (hasMinCodeVersion(viewer.platformDetails, 62)) {
     return {
       newThreadID: id,
       updatesResult: {
         newUpdates: viewerUpdates,
       },
       userInfos,
       newMessageInfos,
     };
   }
 
   return {
     newThreadInfo: threadInfos[id],
     updatesResult: {
       newUpdates: viewerUpdates,
     },
     userInfos,
     newMessageInfos,
   };
 }
 
 function createPrivateThread(
   viewer: Viewer,
   username: string,
 ): Promise<NewThreadResponse> {
   return createThread(
     viewer,
     {
       type: threadTypes.PRIVATE,
       name: username,
       description: privateThreadDescription,
       ghostMemberIDs: [squadbot.userID],
     },
     {
       forceAddMembers: true,
     },
   );
 }
 
 export { createThread, createPrivateThread, privateThreadDescription };