diff --git a/keyserver/src/fetchers/message-fetchers.js b/keyserver/src/fetchers/message-fetchers.js
index d26083bd5..33076a612 100644
--- a/keyserver/src/fetchers/message-fetchers.js
+++ b/keyserver/src/fetchers/message-fetchers.js
@@ -1,784 +1,834 @@
 // @flow
 
 import invariant from 'invariant';
 
 import {
   sortMessageInfoList,
   shimUnsupportedRawMessageInfos,
 } from 'lib/shared/message-utils.js';
 import { messageSpecs } from 'lib/shared/messages/message-specs.js';
 import { getNotifCollapseKey } from 'lib/shared/notif-utils.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
 import {
   type RawMessageInfo,
   type RawComposableMessageInfo,
   type RawRobotextMessageInfo,
   messageTypes,
   type MessageType,
   type EditMessageContent,
   assertMessageType,
   type MessageSelectionCriteria,
   type MessageTruncationStatus,
   messageTruncationStatus,
   type FetchMessageInfosResult,
   defaultMaxMessageAge,
+  type FetchPinnedMessagesRequest,
+  type FetchPinnedMessagesResult,
 } from 'lib/types/message-types.js';
 import { threadPermissions } from 'lib/types/thread-types.js';
 import { ServerError } from 'lib/utils/errors.js';
 
 import {
   constructMediaFromMediaMessageContentsAndUploadRows,
   imagesFromRow,
 } from './upload-fetchers.js';
 import {
   dbQuery,
   SQL,
   mergeOrConditions,
   mergeAndConditions,
 } from '../database/database.js';
 import type { SQLStatementType } from '../database/types.js';
 import type { PushInfo } from '../push/send.js';
 import type { Viewer } from '../session/viewer.js';
 import {
   creationString,
   localIDFromCreationString,
 } from '../utils/idempotent.js';
 
 export type CollapsableNotifInfo = {
   collapseKey: ?string,
   existingMessageInfos: RawMessageInfo[],
   newMessageInfos: RawMessageInfo[],
 };
 export type FetchCollapsableNotifsResult = {
   [userID: string]: CollapsableNotifInfo[],
 };
 
 const visibleExtractString = `$.${threadPermissions.VISIBLE}.value`;
 
 // This function doesn't filter RawMessageInfos based on what messageTypes the
 // client supports, since each user can have multiple clients. The caller must
 // handle this filtering.
 async function fetchCollapsableNotifs(
   pushInfo: PushInfo,
 ): Promise<FetchCollapsableNotifsResult> {
   // First, we need to fetch any notifications that should be collapsed
   const usersToCollapseKeysToInfo = {};
   const usersToCollapsableNotifInfo = {};
   for (const userID in pushInfo) {
     usersToCollapseKeysToInfo[userID] = {};
     usersToCollapsableNotifInfo[userID] = [];
     for (let i = 0; i < pushInfo[userID].messageInfos.length; i++) {
       const rawMessageInfo = pushInfo[userID].messageInfos[i];
       const messageData = pushInfo[userID].messageDatas[i];
       const collapseKey = getNotifCollapseKey(rawMessageInfo, messageData);
       if (!collapseKey) {
         const collapsableNotifInfo = {
           collapseKey,
           existingMessageInfos: [],
           newMessageInfos: [rawMessageInfo],
         };
         usersToCollapsableNotifInfo[userID].push(collapsableNotifInfo);
         continue;
       }
       if (!usersToCollapseKeysToInfo[userID][collapseKey]) {
         usersToCollapseKeysToInfo[userID][collapseKey] = {
           collapseKey,
           existingMessageInfos: [],
           newMessageInfos: [],
         };
       }
       usersToCollapseKeysToInfo[userID][collapseKey].newMessageInfos.push(
         rawMessageInfo,
       );
     }
   }
 
   const sqlTuples = [];
   for (const userID in usersToCollapseKeysToInfo) {
     const collapseKeysToInfo = usersToCollapseKeysToInfo[userID];
     for (const collapseKey in collapseKeysToInfo) {
       sqlTuples.push(
         SQL`(n.user = ${userID} AND n.collapse_key = ${collapseKey})`,
       );
     }
   }
 
   if (sqlTuples.length === 0) {
     return usersToCollapsableNotifInfo;
   }
 
   const collapseQuery = SQL`
     SELECT m.id, m.thread AS threadID, m.content, m.time, m.type,
       m.user AS creatorID, m.target_message as targetMessageID,
       stm.permissions AS subthread_permissions, n.user,
       n.collapse_key, up.id AS uploadID, up.type AS uploadType,
       up.secret AS uploadSecret, up.extra AS uploadExtra
     FROM notifications n
     LEFT JOIN messages m ON m.id = n.message
     LEFT JOIN uploads up ON up.container = m.id
     LEFT JOIN memberships mm ON mm.thread = m.thread AND mm.user = n.user
     LEFT JOIN memberships stm
       ON m.type = ${messageTypes.CREATE_SUB_THREAD}
         AND stm.thread = m.content AND stm.user = n.user
     WHERE n.rescinded = 0 AND
       JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE AND
   `;
   collapseQuery.append(mergeOrConditions(sqlTuples));
   collapseQuery.append(SQL`ORDER BY m.time DESC, m.id DESC`);
   const [collapseResult] = await dbQuery(collapseQuery);
 
   const rowsByUser = new Map();
   for (const row of collapseResult) {
     const user = row.user.toString();
     const currentRowsForUser = rowsByUser.get(user);
     if (currentRowsForUser) {
       currentRowsForUser.push(row);
     } else {
       rowsByUser.set(user, [row]);
     }
   }
 
   const derivedMessages = await fetchDerivedMessages(collapseResult);
   for (const userRows of rowsByUser.values()) {
     const messages = parseMessageSQLResult(userRows, derivedMessages);
     for (const message of messages) {
       const { rawMessageInfo, rows } = message;
       const [row] = rows;
       const info = usersToCollapseKeysToInfo[row.user][row.collapse_key];
       info.existingMessageInfos.push(rawMessageInfo);
     }
   }
 
   for (const userID in usersToCollapseKeysToInfo) {
     const collapseKeysToInfo = usersToCollapseKeysToInfo[userID];
     for (const collapseKey in collapseKeysToInfo) {
       const info = collapseKeysToInfo[collapseKey];
       usersToCollapsableNotifInfo[userID].push({
         collapseKey: info.collapseKey,
         existingMessageInfos: sortMessageInfoList(info.existingMessageInfos),
         newMessageInfos: sortMessageInfoList(info.newMessageInfos),
       });
     }
   }
 
   return usersToCollapsableNotifInfo;
 }
 
 type MessageSQLResult = $ReadOnlyArray<{
   rawMessageInfo: RawMessageInfo,
   rows: $ReadOnlyArray<Object>,
 }>;
 function parseMessageSQLResult(
   rows: $ReadOnlyArray<Object>,
   derivedMessages: $ReadOnlyMap<
     string,
     RawComposableMessageInfo | RawRobotextMessageInfo,
   >,
   viewer?: Viewer,
 ): MessageSQLResult {
   const rowsByID = new Map();
   for (const row of rows) {
     const id = row.id.toString();
     const currentRowsForID = rowsByID.get(id);
     if (currentRowsForID) {
       currentRowsForID.push(row);
     } else {
       rowsByID.set(id, [row]);
     }
   }
 
   const messages = [];
   for (const messageRows of rowsByID.values()) {
     const rawMessageInfo = rawMessageInfoFromRows(
       messageRows,
       viewer,
       derivedMessages,
     );
     if (rawMessageInfo) {
       messages.push({ rawMessageInfo, rows: messageRows });
     }
   }
 
   return messages;
 }
 
 function assertSingleRow(rows: $ReadOnlyArray<Object>): Object {
   if (rows.length === 0) {
     throw new Error('expected single row, but none present!');
   } else if (rows.length !== 1) {
     const messageIDs = rows.map(row => row.id.toString());
     console.warn(
       `expected single row, but there are multiple! ${messageIDs.join(', ')}`,
     );
   }
   return rows[0];
 }
 
 function mostRecentRowType(rows: $ReadOnlyArray<Object>): MessageType {
   if (rows.length === 0) {
     throw new Error('expected row, but none present!');
   }
   return assertMessageType(rows[0].type);
 }
 
 function rawMessageInfoFromRows(
   rawRows: $ReadOnlyArray<Object>,
   viewer?: Viewer,
   derivedMessages: $ReadOnlyMap<
     string,
     RawComposableMessageInfo | RawRobotextMessageInfo,
   >,
 ): ?RawMessageInfo {
   const rows = rawRows.map(row => ({
     ...row,
     subthread_permissions: JSON.parse(row.subthread_permissions),
   }));
 
   const type = mostRecentRowType(rows);
   const messageSpec = messageSpecs[type];
 
   if (type === messageTypes.IMAGES || type === messageTypes.MULTIMEDIA) {
     let media;
     if (type === messageTypes.MULTIMEDIA) {
       const mediaMessageContents = JSON.parse(rows[0].content);
       media = constructMediaFromMediaMessageContentsAndUploadRows(
         mediaMessageContents,
         rows,
       );
     } else {
       media = rows.filter(row => row.uploadID).map(imagesFromRow);
     }
     const [row] = rows;
     const localID = localIDFromCreationString(viewer, row.creation);
     invariant(
       messageSpec.rawMessageInfoFromServerDBRow,
       `multimedia message spec should have rawMessageInfoFromServerDBRow`,
     );
     return messageSpec.rawMessageInfoFromServerDBRow(row, {
       media,
       derivedMessages,
       localID,
     });
   }
 
   const row = assertSingleRow(rows);
   const localID = localIDFromCreationString(viewer, row.creation);
   invariant(
     messageSpec.rawMessageInfoFromServerDBRow,
     `message spec ${type} should have rawMessageInfoFromServerDBRow`,
   );
   return messageSpec.rawMessageInfoFromServerDBRow(row, {
     derivedMessages,
     localID,
   });
 }
 
 async function fetchMessageInfos(
   viewer: Viewer,
   criteria: MessageSelectionCriteria,
   numberPerThread: number,
 ): Promise<FetchMessageInfosResult> {
   const { sqlClause: selectionClause, timeFilterData } =
     parseMessageSelectionCriteria(viewer, criteria);
   const truncationStatuses = {};
 
   const viewerID = viewer.id;
   const query = SQL`
     WITH thread_window AS (
       SELECT m.id, m.thread AS threadID, m.user AS creatorID,
         m.target_message as targetMessageID, m.content, m.time, m.type,
         m.creation, stm.permissions AS subthread_permissions,
         ROW_NUMBER() OVER (
           PARTITION BY threadID ORDER BY m.time DESC, m.id DESC
         ) n
       FROM messages m
       LEFT JOIN memberships mm
         ON mm.thread = m.thread AND mm.user = ${viewerID}
       LEFT JOIN memberships stm ON m.type = ${messageTypes.CREATE_SUB_THREAD}
         AND stm.thread = m.content AND stm.user = ${viewerID}
       WHERE JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE AND
   `;
   query.append(selectionClause);
   query.append(SQL`
     )
     SELECT tw.*,
       up.id AS uploadID, up.type AS uploadType, up.secret AS uploadSecret,
       up.extra AS uploadExtra
     FROM thread_window tw
     LEFT JOIN uploads up ON up.container = tw.id
     WHERE tw.n <= ${numberPerThread}
     ORDER BY tw.threadID, tw.time DESC, tw.id DESC
   `);
 
   const [result] = await dbQuery(query);
   const derivedMessages = await fetchDerivedMessages(result, viewer);
   const messages = await parseMessageSQLResult(result, derivedMessages, viewer);
 
   const rawMessageInfos = [];
   const threadToMessageCount = new Map();
   for (const message of messages) {
     const { rawMessageInfo } = message;
     rawMessageInfos.push(rawMessageInfo);
     const { threadID } = rawMessageInfo;
     const currentCountValue = threadToMessageCount.get(threadID);
     const currentCount = currentCountValue ? currentCountValue : 0;
     threadToMessageCount.set(threadID, currentCount + 1);
   }
 
   for (const [threadID, messageCount] of threadToMessageCount) {
     // If we matched the exact amount we limited to, we're probably truncating
     // our result set. By setting TRUNCATED here, we tell the client that the
     // result set might not be continguous with what's already in their
     // MessageStore. More details about TRUNCATED can be found in
     // lib/types/message-types.js
     if (messageCount >= numberPerThread) {
       // We won't set TRUNCATED if a cursor was specified for a given thread,
       // since then the result is guaranteed to be contiguous with what the
       // client has
       if (criteria.threadCursors && criteria.threadCursors[threadID]) {
         truncationStatuses[threadID] = messageTruncationStatus.UNCHANGED;
       } else {
         truncationStatuses[threadID] = messageTruncationStatus.TRUNCATED;
       }
       continue;
     }
     const hasTimeFilter = hasTimeFilterForThread(timeFilterData, threadID);
     if (!hasTimeFilter) {
       // If there is no time filter for a given thread, and there are fewer
       // messages returned than the max we queried for a given thread, we can
       // conclude that our result set includes all messages for that thread
       truncationStatuses[threadID] = messageTruncationStatus.EXHAUSTIVE;
     }
   }
 
   for (const rawMessageInfo of rawMessageInfos) {
     if (messageSpecs[rawMessageInfo.type].startsThread) {
       truncationStatuses[rawMessageInfo.threadID] =
         messageTruncationStatus.EXHAUSTIVE;
     }
   }
 
   for (const threadID in criteria.threadCursors) {
     const truncationStatus = truncationStatuses[threadID];
     if (truncationStatus !== null && truncationStatus !== undefined) {
       continue;
     }
     const hasTimeFilter = hasTimeFilterForThread(timeFilterData, threadID);
     if (!hasTimeFilter) {
       // If there is no time filter for a given thread, and zero messages were
       // returned, we can conclude that this thread has zero messages. This is
       // a case of database corruption that should not be possible, but likely
       // we have some threads like this on prod (either due to some transient
       // issues or due to old buggy code)
       truncationStatuses[threadID] = messageTruncationStatus.EXHAUSTIVE;
     } else {
       // If this thread was explicitly queried for, and we got no results, but
       // we can't conclude that it's EXHAUSTIVE, then we'll set to UNCHANGED.
       truncationStatuses[threadID] = messageTruncationStatus.UNCHANGED;
     }
   }
 
   const shimmedRawMessageInfos = shimUnsupportedRawMessageInfos(
     rawMessageInfos,
     viewer.platformDetails,
   );
 
   return {
     rawMessageInfos: shimmedRawMessageInfos,
     truncationStatuses,
   };
 }
 
 function hasTimeFilterForThread(
   timeFilterData: TimeFilterData,
   threadID: string,
 ) {
   if (timeFilterData.timeFilter === 'ALL') {
     return true;
   } else if (timeFilterData.timeFilter === 'NONE') {
     return false;
   } else if (timeFilterData.timeFilter === 'ALL_EXCEPT_EXCLUDED') {
     return !timeFilterData.excludedFromTimeFilter.has(threadID);
   } else {
     invariant(
       false,
       `unrecognized timeFilter type ${timeFilterData.timeFilter}`,
     );
   }
 }
 
 type TimeFilterData =
   | { +timeFilter: 'ALL' | 'NONE' }
   | {
       +timeFilter: 'ALL_EXCEPT_EXCLUDED',
       +excludedFromTimeFilter: $ReadOnlySet<string>,
     };
 type ParsedMessageSelectionCriteria = {
   +sqlClause: SQLStatementType,
   +timeFilterData: TimeFilterData,
 };
 function parseMessageSelectionCriteria(
   viewer: Viewer,
   criteria: MessageSelectionCriteria,
 ): ParsedMessageSelectionCriteria {
   const minMessageTime = Date.now() - defaultMaxMessageAge;
   const shouldApplyTimeFilter = hasMinCodeVersion(viewer.platformDetails, 130);
 
   let globalTimeFilter;
   if (criteria.newerThan) {
     globalTimeFilter = SQL`m.time > ${criteria.newerThan}`;
   } else if (!criteria.threadCursors && shouldApplyTimeFilter) {
     globalTimeFilter = SQL`m.time > ${minMessageTime}`;
   }
 
   const threadConditions = [];
   if (
     criteria.joinedThreads === true &&
     shouldApplyTimeFilter &&
     !globalTimeFilter
   ) {
     threadConditions.push(SQL`(mm.role > 0 AND m.time > ${minMessageTime})`);
   } else if (criteria.joinedThreads === true) {
     threadConditions.push(SQL`mm.role > 0`);
   }
   if (criteria.threadCursors) {
     for (const threadID in criteria.threadCursors) {
       const cursor = criteria.threadCursors[threadID];
       if (cursor) {
         threadConditions.push(
           SQL`(m.thread = ${threadID} AND m.id < ${cursor})`,
         );
       } else {
         threadConditions.push(SQL`m.thread = ${threadID}`);
       }
     }
   }
   if (threadConditions.length === 0) {
     throw new ServerError('internal_error');
   }
   const threadClause = mergeOrConditions(threadConditions);
 
   let timeFilterData;
   if (globalTimeFilter) {
     timeFilterData = { timeFilter: 'ALL' };
   } else if (!shouldApplyTimeFilter) {
     timeFilterData = { timeFilter: 'NONE' };
   } else {
     invariant(
       criteria.threadCursors,
       'ALL_EXCEPT_EXCLUDED should correspond to threadCursors being set',
     );
     const excludedFromTimeFilter = new Set(Object.keys(criteria.threadCursors));
     timeFilterData = {
       timeFilter: 'ALL_EXCEPT_EXCLUDED',
       excludedFromTimeFilter,
     };
   }
 
   const conditions = [globalTimeFilter, threadClause].filter(Boolean);
   const sqlClause = mergeAndConditions(conditions);
 
   return { sqlClause, timeFilterData };
 }
 
 function messageSelectionCriteriaToInitialTruncationStatuses(
   criteria: MessageSelectionCriteria,
   defaultTruncationStatus: MessageTruncationStatus,
 ) {
   const truncationStatuses = {};
   if (criteria.threadCursors) {
     for (const threadID in criteria.threadCursors) {
       truncationStatuses[threadID] = defaultTruncationStatus;
     }
   }
   return truncationStatuses;
 }
 
 async function fetchMessageInfosSince(
   viewer: Viewer,
   criteria: MessageSelectionCriteria,
   maxNumberPerThread: number,
 ): Promise<FetchMessageInfosResult> {
   const { sqlClause: selectionClause } = parseMessageSelectionCriteria(
     viewer,
     criteria,
   );
   const truncationStatuses =
     messageSelectionCriteriaToInitialTruncationStatuses(
       criteria,
       messageTruncationStatus.UNCHANGED,
     );
 
   const viewerID = viewer.id;
   const query = SQL`
     SELECT m.id, m.thread AS threadID, m.content, m.time, m.type,
       m.creation, m.user AS creatorID, m.target_message as targetMessageID,
       stm.permissions AS subthread_permissions, up.id AS uploadID,
       up.type AS uploadType, up.secret AS uploadSecret, up.extra AS uploadExtra
     FROM messages m
     LEFT JOIN uploads up ON up.container = m.id
     LEFT JOIN memberships mm ON mm.thread = m.thread AND mm.user = ${viewerID}
     LEFT JOIN memberships stm ON m.type = ${messageTypes.CREATE_SUB_THREAD}
       AND stm.thread = m.content AND stm.user = ${viewerID}
     WHERE JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE AND
   `;
   query.append(selectionClause);
   query.append(SQL`
     ORDER BY m.thread, m.time DESC, m.id DESC
   `);
   const [result] = await dbQuery(query);
   const derivedMessages = await fetchDerivedMessages(result, viewer);
   const messages = await parseMessageSQLResult(result, derivedMessages, viewer);
 
   const rawMessageInfos = [];
   let currentThreadID = null;
   let numMessagesForCurrentThreadID = 0;
   for (const message of messages) {
     const { rawMessageInfo } = message;
     const { threadID } = rawMessageInfo;
     if (threadID !== currentThreadID) {
       currentThreadID = threadID;
       numMessagesForCurrentThreadID = 1;
       truncationStatuses[threadID] = messageTruncationStatus.UNCHANGED;
     } else {
       numMessagesForCurrentThreadID++;
     }
     if (numMessagesForCurrentThreadID <= maxNumberPerThread) {
       if (messageSpecs[rawMessageInfo.type].startsThread) {
         truncationStatuses[threadID] = messageTruncationStatus.EXHAUSTIVE;
       }
       rawMessageInfos.push(rawMessageInfo);
     } else if (numMessagesForCurrentThreadID === maxNumberPerThread + 1) {
       truncationStatuses[threadID] = messageTruncationStatus.TRUNCATED;
     }
   }
 
   const shimmedRawMessageInfos = shimUnsupportedRawMessageInfos(
     rawMessageInfos,
     viewer.platformDetails,
   );
 
   return {
     rawMessageInfos: shimmedRawMessageInfos,
     truncationStatuses,
   };
 }
 
 function getMessageFetchResultFromRedisMessages(
   viewer: Viewer,
   rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 ): FetchMessageInfosResult {
   const truncationStatuses = {};
   for (const rawMessageInfo of rawMessageInfos) {
     truncationStatuses[rawMessageInfo.threadID] =
       messageTruncationStatus.UNCHANGED;
   }
   const shimmedRawMessageInfos = shimUnsupportedRawMessageInfos(
     rawMessageInfos,
     viewer.platformDetails,
   );
   return {
     rawMessageInfos: shimmedRawMessageInfos,
     truncationStatuses,
   };
 }
 
 async function fetchMessageInfoForLocalID(
   viewer: Viewer,
   localID: ?string,
 ): Promise<?RawMessageInfo> {
   if (!localID || !viewer.hasSessionInfo) {
     return null;
   }
   const creation = creationString(viewer, localID);
   const viewerID = viewer.id;
   const query = SQL`
     SELECT m.id, m.thread AS threadID, m.content, m.time, m.type, m.creation,
       m.user AS creatorID, m.target_message as targetMessageID,
       stm.permissions AS subthread_permissions, up.id AS uploadID,
       up.type AS uploadType, up.secret AS uploadSecret, up.extra AS uploadExtra
     FROM messages m
     LEFT JOIN uploads up ON up.container = m.id
     LEFT JOIN memberships mm ON mm.thread = m.thread AND mm.user = ${viewerID}
     LEFT JOIN memberships stm ON m.type = ${messageTypes.CREATE_SUB_THREAD}
       AND stm.thread = m.content AND stm.user = ${viewerID}
     WHERE m.user = ${viewerID} AND m.creation = ${creation} AND
       JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE
   `;
 
   const [result] = await dbQuery(query);
   if (result.length === 0) {
     return null;
   }
   const derivedMessages = await fetchDerivedMessages(result, viewer);
   return rawMessageInfoFromRows(result, viewer, derivedMessages);
 }
 
 const entryIDExtractString = '$.entryID';
 async function fetchMessageInfoForEntryAction(
   viewer: Viewer,
   messageType: MessageType,
   entryID: string,
   threadID: string,
 ): Promise<?RawMessageInfo> {
   const viewerID = viewer.id;
   const query = SQL`
     SELECT m.id, m.thread AS threadID, m.content, m.time, m.type, m.creation,
       m.user AS creatorID, m.target_message as targetMessageID,
       up.id AS uploadID, up.type AS uploadType, up.secret AS uploadSecret,
       up.extra AS uploadExtra
     FROM messages m
     LEFT JOIN uploads up ON up.container = m.id
     LEFT JOIN memberships mm ON mm.thread = m.thread AND mm.user = ${viewerID}
     WHERE m.user = ${viewerID} AND m.thread = ${threadID} AND
       m.type = ${messageType} AND
       JSON_EXTRACT(m.content, ${entryIDExtractString}) = ${entryID} AND
       JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE
   `;
 
   const [result] = await dbQuery(query);
   if (result.length === 0) {
     return null;
   }
   const derivedMessages = await fetchDerivedMessages(result, viewer);
   return rawMessageInfoFromRows(result, viewer, derivedMessages);
 }
 
 async function fetchMessageRowsByIDs(messageIDs: $ReadOnlyArray<string>) {
   const query = SQL`
     SELECT m.id, m.thread AS threadID, m.content, m.time, m.type, m.creation,
       m.user AS creatorID, m.target_message as targetMessageID,
       stm.permissions AS subthread_permissions, up.id AS uploadID,
       up.type AS uploadType, up.secret AS uploadSecret, up.extra AS uploadExtra
     FROM messages m
     LEFT JOIN uploads up ON up.container = m.id
     LEFT JOIN memberships stm ON m.type = ${messageTypes.CREATE_SUB_THREAD}
       AND stm.thread = m.content AND stm.user = m.user
     WHERE m.id IN (${messageIDs})
   `;
   const [result] = await dbQuery(query);
   return result;
 }
 
+async function fetchPinnedMessageInfos(
+  viewer: Viewer,
+  request: FetchPinnedMessagesRequest,
+): Promise<FetchPinnedMessagesResult> {
+  // The only message types that can be pinned are 0, 14, and 15
+  // (text, images, and multimedia), so we don't need to worry about
+  // an admin pinning a message about creating a secret subchannel. This is
+  // why we don't check subthread permissions (as opposed to other queries).
+  const messageRowsQuery = SQL`
+    SELECT m.id, m.thread AS threadID, m.content, m.time, m.type, m.creation,
+      m.user AS creatorID, m.target_message as targetMessageID,
+      NULL AS subthread_permissions, u.id AS uploadID,
+      u.type AS uploadType, u.secret AS uploadSecret, u.extra AS uploadExtra
+    FROM messages m
+    LEFT JOIN uploads u ON u.container = m.id
+    LEFT JOIN memberships mm ON mm.thread = m.thread AND mm.user = ${viewer.id}
+    WHERE m.thread = ${request.threadID} 
+      AND m.pinned = 1
+      AND JSON_EXTRACT(mm.permissions, ${visibleExtractString}) IS TRUE
+    ORDER BY m.pin_time DESC
+  `;
+  const [messageRows] = await dbQuery(messageRowsQuery);
+  if (messageRows.length === 0) {
+    return { pinnedMessages: [] };
+  }
+  const derivedMessages = await fetchDerivedMessages(messageRows, viewer);
+
+  const parsedPinnedMessages = await parseMessageSQLResult(
+    messageRows,
+    derivedMessages,
+    viewer,
+  );
+
+  const pinnedRawMessageInfos = parsedPinnedMessages.map(
+    message => message.rawMessageInfo,
+  );
+
+  const shimmedPinnedRawMessageInfos = shimUnsupportedRawMessageInfos(
+    pinnedRawMessageInfos,
+    viewer.platformDetails,
+  );
+
+  return {
+    pinnedMessages: shimmedPinnedRawMessageInfos,
+  };
+}
+
 async function fetchDerivedMessages(
   rows: $ReadOnlyArray<Object>,
   viewer?: Viewer,
 ): Promise<
   $ReadOnlyMap<string, RawComposableMessageInfo | RawRobotextMessageInfo>,
 > {
   const requiredIDs = new Set<string>();
   for (const row of rows) {
     if (row.type === messageTypes.SIDEBAR_SOURCE) {
       const content = JSON.parse(row.content);
       requiredIDs.add(content.sourceMessageID);
     }
   }
 
   const messagesByID = new Map<
     string,
     RawComposableMessageInfo | RawRobotextMessageInfo,
   >();
   if (requiredIDs.size === 0) {
     return messagesByID;
   }
 
   const [result, edits] = await Promise.all([
     fetchMessageRowsByIDs([...requiredIDs]),
     fetchLatestEditMessageContentByIDs([...requiredIDs]),
   ]);
   const messages = await parseMessageSQLResult(result, new Map(), viewer);
 
   for (const message of messages) {
     let { rawMessageInfo } = message;
     if (rawMessageInfo.id) {
       invariant(
         rawMessageInfo.type !== messageTypes.SIDEBAR_SOURCE &&
           rawMessageInfo.type !== messageTypes.REACTION &&
           rawMessageInfo.type !== messageTypes.EDIT_MESSAGE,
         'SIDEBAR_SOURCE should not point to a SIDEBAR_SOURCE, REACTION or EDIT_MESSAGE',
       );
       const editedContent = edits.get(rawMessageInfo.id);
       if (editedContent && rawMessageInfo.type === messageTypes.TEXT) {
         rawMessageInfo = {
           ...rawMessageInfo,
           text: editedContent.text,
         };
       }
       invariant(rawMessageInfo.id, 'rawMessageInfo.id should not be null');
       messagesByID.set(rawMessageInfo.id, rawMessageInfo);
     }
   }
   return messagesByID;
 }
 
 async function fetchMessageInfoByID(
   viewer?: Viewer,
   messageID: string,
 ): Promise<?RawMessageInfo> {
   const result = await fetchMessageRowsByIDs([messageID]);
   if (result.length === 0) {
     return null;
   }
   const derivedMessages = await fetchDerivedMessages(result, viewer);
   return rawMessageInfoFromRows(result, viewer, derivedMessages);
 }
 
 async function fetchThreadMessagesCount(threadID: string): Promise<number> {
   const query = SQL`
     SELECT COUNT(*) AS count
     FROM messages
     WHERE thread = ${threadID}
   `;
   const [result] = await dbQuery(query);
   return result[0].count;
 }
 
 async function fetchLatestEditMessageContentByIDs(
   messageIDs: $ReadOnlyArray<string>,
 ): Promise<$ReadOnlyMap<string, EditMessageContent>> {
   const latestEditedMessageQuery = SQL`
     SELECT m.id, (
       SELECT m2.content
       FROM messages m2
       WHERE m.id = m2.target_message
         AND m.thread = m2.thread
         AND m2.type = ${messageTypes.EDIT_MESSAGE}
       ORDER BY time DESC, id DESC
       LIMIT 1
     ) content
     FROM messages m
     WHERE m.id IN(${messageIDs})
   `;
 
   const [result] = await dbQuery(latestEditedMessageQuery);
   const latestContentByID = new Map();
   for (const row of result) {
     if (!row.content) {
       continue;
     }
     const content = JSON.parse(row.content);
     latestContentByID.set(row.id.toString(), content);
   }
 
   return latestContentByID;
 }
 
 async function fetchLatestEditMessageContentByID(
   messageID: string,
 ): Promise<?EditMessageContent> {
   const result = await fetchLatestEditMessageContentByIDs([messageID]);
   const content = result.get(messageID);
   return content;
 }
 
 export {
   fetchCollapsableNotifs,
   fetchMessageInfos,
   fetchMessageInfosSince,
   getMessageFetchResultFromRedisMessages,
   fetchMessageInfoForLocalID,
   fetchMessageInfoForEntryAction,
   fetchMessageInfoByID,
   fetchThreadMessagesCount,
   fetchLatestEditMessageContentByID,
+  fetchPinnedMessageInfos,
 };
diff --git a/lib/types/message-types.js b/lib/types/message-types.js
index 376f62fcb..6493ee13b 100644
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -1,602 +1,610 @@
 // @flow
 
 import invariant from 'invariant';
 
 import { type ClientDBMediaInfo } from './media-types.js';
 import type {
   AddMembersMessageData,
   AddMembersMessageInfo,
   RawAddMembersMessageInfo,
 } from './messages/add-members.js';
 import type {
   ChangeRoleMessageData,
   ChangeRoleMessageInfo,
   RawChangeRoleMessageInfo,
 } from './messages/change-role.js';
 import type {
   ChangeSettingsMessageData,
   ChangeSettingsMessageInfo,
   RawChangeSettingsMessageInfo,
 } from './messages/change-settings.js';
 import type {
   CreateEntryMessageData,
   CreateEntryMessageInfo,
   RawCreateEntryMessageInfo,
 } from './messages/create-entry.js';
 import type {
   CreateSidebarMessageData,
   CreateSidebarMessageInfo,
   RawCreateSidebarMessageInfo,
 } from './messages/create-sidebar.js';
 import type {
   CreateSubthreadMessageData,
   CreateSubthreadMessageInfo,
   RawCreateSubthreadMessageInfo,
 } from './messages/create-subthread.js';
 import type {
   CreateThreadMessageData,
   CreateThreadMessageInfo,
   RawCreateThreadMessageInfo,
 } from './messages/create-thread.js';
 import type {
   DeleteEntryMessageData,
   DeleteEntryMessageInfo,
   RawDeleteEntryMessageInfo,
 } from './messages/delete-entry.js';
 import type {
   EditEntryMessageData,
   EditEntryMessageInfo,
   RawEditEntryMessageInfo,
 } from './messages/edit-entry.js';
 import type {
   RawEditMessageInfo,
   EditMessageData,
   EditMessageInfo,
 } from './messages/edit.js';
 import type {
   ImagesMessageData,
   ImagesMessageInfo,
   RawImagesMessageInfo,
 } from './messages/images.js';
 import type {
   JoinThreadMessageData,
   JoinThreadMessageInfo,
   RawJoinThreadMessageInfo,
 } from './messages/join-thread.js';
 import type {
   LeaveThreadMessageData,
   LeaveThreadMessageInfo,
   RawLeaveThreadMessageInfo,
 } from './messages/leave-thread.js';
 import type {
   MediaMessageData,
   MediaMessageInfo,
   MediaMessageServerDBContent,
   RawMediaMessageInfo,
 } from './messages/media.js';
 import type {
   ReactionMessageData,
   RawReactionMessageInfo,
   ReactionMessageInfo,
 } from './messages/reaction.js';
 import type {
   RawRemoveMembersMessageInfo,
   RemoveMembersMessageData,
   RemoveMembersMessageInfo,
 } from './messages/remove-members.js';
 import type {
   RawRestoreEntryMessageInfo,
   RestoreEntryMessageData,
   RestoreEntryMessageInfo,
 } from './messages/restore-entry.js';
 import type {
   RawTextMessageInfo,
   TextMessageData,
   TextMessageInfo,
 } from './messages/text.js';
 import type {
   RawUnsupportedMessageInfo,
   UnsupportedMessageInfo,
 } from './messages/unsupported.js';
 import type {
   RawUpdateRelationshipMessageInfo,
   UpdateRelationshipMessageData,
   UpdateRelationshipMessageInfo,
 } from './messages/update-relationship.js';
 import { type RelativeUserInfo, type UserInfos } from './user-types.js';
 import type { CallServerEndpointResultInfoInterface } from '../utils/call-server-endpoint.js';
 
 export const messageTypes = Object.freeze({
   TEXT: 0,
   // Appears in the newly created thread
   CREATE_THREAD: 1,
   ADD_MEMBERS: 2,
   // Appears in the parent when a child thread is created
   // (historically also when a sidebar was created)
   CREATE_SUB_THREAD: 3,
   CHANGE_SETTINGS: 4,
   REMOVE_MEMBERS: 5,
   CHANGE_ROLE: 6,
   LEAVE_THREAD: 7,
   JOIN_THREAD: 8,
   CREATE_ENTRY: 9,
   EDIT_ENTRY: 10,
   DELETE_ENTRY: 11,
   RESTORE_ENTRY: 12,
   // When the server has a message to deliver that the client can't properly
   // render because the client is too old, the server will send this message
   // type instead. Consequently, there is no MessageData for UNSUPPORTED - just
   // a RawMessageInfo and a MessageInfo. Note that native/persist.js handles
   // converting these MessageInfos when the client is upgraded.
   UNSUPPORTED: 13,
   IMAGES: 14,
   MULTIMEDIA: 15,
   UPDATE_RELATIONSHIP: 16,
   SIDEBAR_SOURCE: 17,
   // Appears in the newly created sidebar
   CREATE_SIDEBAR: 18,
   REACTION: 19,
   EDIT_MESSAGE: 20,
 });
 export type MessageType = $Values<typeof messageTypes>;
 export function assertMessageType(ourMessageType: number): MessageType {
   invariant(
     ourMessageType === 0 ||
       ourMessageType === 1 ||
       ourMessageType === 2 ||
       ourMessageType === 3 ||
       ourMessageType === 4 ||
       ourMessageType === 5 ||
       ourMessageType === 6 ||
       ourMessageType === 7 ||
       ourMessageType === 8 ||
       ourMessageType === 9 ||
       ourMessageType === 10 ||
       ourMessageType === 11 ||
       ourMessageType === 12 ||
       ourMessageType === 13 ||
       ourMessageType === 14 ||
       ourMessageType === 15 ||
       ourMessageType === 16 ||
       ourMessageType === 17 ||
       ourMessageType === 18 ||
       ourMessageType === 19 ||
       ourMessageType === 20,
     'number is not MessageType enum',
   );
   return ourMessageType;
 }
 
 const composableMessageTypes = new Set([
   messageTypes.TEXT,
   messageTypes.IMAGES,
   messageTypes.MULTIMEDIA,
 ]);
 export function isComposableMessageType(ourMessageType: MessageType): boolean {
   return composableMessageTypes.has(ourMessageType);
 }
 export function assertComposableMessageType(
   ourMessageType: MessageType,
 ): MessageType {
   invariant(
     isComposableMessageType(ourMessageType),
     'MessageType is not composed',
   );
   return ourMessageType;
 }
 export function assertComposableRawMessage(
   message: RawMessageInfo,
 ): RawComposableMessageInfo {
   invariant(
     message.type === messageTypes.TEXT ||
       message.type === messageTypes.IMAGES ||
       message.type === messageTypes.MULTIMEDIA,
     'Message is not composable',
   );
   return message;
 }
 export function messageDataLocalID(messageData: MessageData): ?string {
   if (
     messageData.type !== messageTypes.TEXT &&
     messageData.type !== messageTypes.IMAGES &&
     messageData.type !== messageTypes.MULTIMEDIA &&
     messageData.type !== messageTypes.REACTION
   ) {
     return null;
   }
   return messageData.localID;
 }
 
 const mediaMessageTypes = new Set([
   messageTypes.IMAGES,
   messageTypes.MULTIMEDIA,
 ]);
 export function isMediaMessageType(ourMessageType: MessageType): boolean {
   return mediaMessageTypes.has(ourMessageType);
 }
 export function assertMediaMessageType(
   ourMessageType: MessageType,
 ): MessageType {
   invariant(isMediaMessageType(ourMessageType), 'MessageType is not media');
   return ourMessageType;
 }
 
 // *MessageData = passed to createMessages function to insert into database
 // Raw*MessageInfo = used by server, and contained in client's local store
 // *MessageInfo = used by client in UI code
 
 export type SidebarSourceMessageData = {
   +type: 17,
   +threadID: string,
   +creatorID: string,
   +time: number,
   +sourceMessage?: RawComposableMessageInfo | RawRobotextMessageInfo,
 };
 
 export type MessageData =
   | TextMessageData
   | CreateThreadMessageData
   | AddMembersMessageData
   | CreateSubthreadMessageData
   | ChangeSettingsMessageData
   | RemoveMembersMessageData
   | ChangeRoleMessageData
   | LeaveThreadMessageData
   | JoinThreadMessageData
   | CreateEntryMessageData
   | EditEntryMessageData
   | DeleteEntryMessageData
   | RestoreEntryMessageData
   | ImagesMessageData
   | MediaMessageData
   | UpdateRelationshipMessageData
   | SidebarSourceMessageData
   | CreateSidebarMessageData
   | ReactionMessageData
   | EditMessageData;
 
 export type MultimediaMessageData = ImagesMessageData | MediaMessageData;
 
 export type RawMultimediaMessageInfo =
   | RawImagesMessageInfo
   | RawMediaMessageInfo;
 export type RawComposableMessageInfo =
   | RawTextMessageInfo
   | RawMultimediaMessageInfo;
 
 export type RawRobotextMessageInfo =
   | RawCreateThreadMessageInfo
   | RawAddMembersMessageInfo
   | RawCreateSubthreadMessageInfo
   | RawChangeSettingsMessageInfo
   | RawRemoveMembersMessageInfo
   | RawChangeRoleMessageInfo
   | RawLeaveThreadMessageInfo
   | RawJoinThreadMessageInfo
   | RawCreateEntryMessageInfo
   | RawEditEntryMessageInfo
   | RawDeleteEntryMessageInfo
   | RawRestoreEntryMessageInfo
   | RawUpdateRelationshipMessageInfo
   | RawCreateSidebarMessageInfo
   | RawUnsupportedMessageInfo;
 export type RawSidebarSourceMessageInfo = {
   ...SidebarSourceMessageData,
   id: string,
 };
 
 export type RawMessageInfo =
   | RawComposableMessageInfo
   | RawRobotextMessageInfo
   | RawSidebarSourceMessageInfo
   | RawReactionMessageInfo
   | RawEditMessageInfo;
 
 export type LocallyComposedMessageInfo =
   | ({
       ...RawImagesMessageInfo,
       +localID: string,
     } & RawImagesMessageInfo)
   | ({
       ...RawMediaMessageInfo,
       +localID: string,
     } & RawMediaMessageInfo)
   | ({
       ...RawTextMessageInfo,
       +localID: string,
     } & RawTextMessageInfo)
   | ({
       ...RawReactionMessageInfo,
       +localID: string,
     } & RawReactionMessageInfo);
 
 export type MultimediaMessageInfo = ImagesMessageInfo | MediaMessageInfo;
 export type ComposableMessageInfo = TextMessageInfo | MultimediaMessageInfo;
 
 export type RobotextMessageInfo =
   | CreateThreadMessageInfo
   | AddMembersMessageInfo
   | CreateSubthreadMessageInfo
   | ChangeSettingsMessageInfo
   | RemoveMembersMessageInfo
   | ChangeRoleMessageInfo
   | LeaveThreadMessageInfo
   | JoinThreadMessageInfo
   | CreateEntryMessageInfo
   | EditEntryMessageInfo
   | DeleteEntryMessageInfo
   | RestoreEntryMessageInfo
   | UnsupportedMessageInfo
   | UpdateRelationshipMessageInfo
   | CreateSidebarMessageInfo;
 export type PreviewableMessageInfo =
   | RobotextMessageInfo
   | MultimediaMessageInfo
   | ReactionMessageInfo;
 
 export type SidebarSourceMessageInfo = {
   +type: 17,
   +id: string,
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number,
   +sourceMessage: ComposableMessageInfo | RobotextMessageInfo,
 };
 
 export type MessageInfo =
   | ComposableMessageInfo
   | RobotextMessageInfo
   | SidebarSourceMessageInfo
   | ReactionMessageInfo
   | EditMessageInfo;
 
 export type ThreadMessageInfo = {
   messageIDs: string[],
   startReached: boolean,
   lastNavigatedTo: number, // millisecond timestamp
   lastPruned: number, // millisecond timestamp
 };
 
 // Tracks client-local information about a message that hasn't been assigned an
 // ID by the server yet. As soon as the client gets an ack from the server for
 // this message, it will clear the LocalMessageInfo.
 export type LocalMessageInfo = {
   +sendFailed?: boolean,
 };
 
 export type MessageStore = {
   +messages: { +[id: string]: RawMessageInfo },
   +threads: { +[threadID: string]: ThreadMessageInfo },
   +local: { +[id: string]: LocalMessageInfo },
   +currentAsOf: number,
 };
 
 export type RemoveMessageOperation = {
   +type: 'remove',
   +payload: { +ids: $ReadOnlyArray<string> },
 };
 
 export type RemoveMessagesForThreadsOperation = {
   +type: 'remove_messages_for_threads',
   +payload: { +threadIDs: $ReadOnlyArray<string> },
 };
 
 export type ReplaceMessageOperation = {
   +type: 'replace',
   +payload: { +id: string, +messageInfo: RawMessageInfo },
 };
 
 export type RekeyMessageOperation = {
   +type: 'rekey',
   +payload: { +from: string, +to: string },
 };
 
 export type RemoveAllMessagesOperation = {
   +type: 'remove_all',
 };
 
 // We were initially using `number`s` for `thread`, `type`, `future_type`, etc.
 // However, we ended up changing `thread` to `string` to account for thread IDs
 // including information about the keyserver (eg 'GENESIS|123') in the future.
 //
 // At that point we discussed whether we should switch the remaining `number`
 // fields to `string`s for consistency and flexibility. We researched whether
 // there was any performance cost to using `string`s instead of `number`s and
 // found the differences to be negligible. We also concluded using `string`s
 // may be safer after considering `jsi::Number` and the various C++ number
 // representations on the CommCoreModule side.
 export type ClientDBMessageInfo = {
   +id: string,
   +local_id: ?string,
   +thread: string,
   +user: string,
   +type: string,
   +future_type: ?string,
   +content: ?string,
   +time: string,
   +media_infos: ?$ReadOnlyArray<ClientDBMediaInfo>,
 };
 
 export type ClientDBReplaceMessageOperation = {
   +type: 'replace',
   +payload: ClientDBMessageInfo,
 };
 
 export type MessageStoreOperation =
   | RemoveMessageOperation
   | ReplaceMessageOperation
   | RekeyMessageOperation
   | RemoveMessagesForThreadsOperation
   | RemoveAllMessagesOperation;
 
 export type ClientDBMessageStoreOperation =
   | RemoveMessageOperation
   | ClientDBReplaceMessageOperation
   | RekeyMessageOperation
   | RemoveMessagesForThreadsOperation
   | RemoveAllMessagesOperation;
 
 export const messageTruncationStatus = Object.freeze({
   // EXHAUSTIVE means we've reached the start of the thread. Either the result
   // set includes the very first message for that thread, or there is nothing
   // behind the cursor you queried for. Given that the client only ever issues
   // ranged queries whose range, when unioned with what is in state, represent
   // the set of all messages for a given thread, we can guarantee that getting
   // EXHAUSTIVE means the start has been reached.
   EXHAUSTIVE: 'exhaustive',
   // TRUNCATED is rare, and means that the server can't guarantee that the
   // result set for a given thread is contiguous with what the client has in its
   // state. If the client can't verify the contiguousness itself, it needs to
   // replace its Redux store's contents with what it is in this payload.
   //  1) getMessageInfosSince: Result set for thread is equal to max, and the
   //     truncation status isn't EXHAUSTIVE (ie. doesn't include the very first
   //     message).
   //  2) getMessageInfos: MessageSelectionCriteria does not specify cursors, the
   //     result set for thread is equal to max, and the truncation status isn't
   //     EXHAUSTIVE. If cursors are specified, we never return truncated, since
   //     the cursor given us guarantees the contiguousness of the result set.
   // Note that in the reducer, we can guarantee contiguousness if there is any
   // intersection between messageIDs in the result set and the set currently in
   // the Redux store.
   TRUNCATED: 'truncated',
   // UNCHANGED means the result set is guaranteed to be contiguous with what the
   // client has in its state, but is not EXHAUSTIVE. Basically, it's anything
   // that isn't either EXHAUSTIVE or TRUNCATED.
   UNCHANGED: 'unchanged',
 });
 export type MessageTruncationStatus = $Values<typeof messageTruncationStatus>;
 export function assertMessageTruncationStatus(
   ourMessageTruncationStatus: string,
 ): MessageTruncationStatus {
   invariant(
     ourMessageTruncationStatus === 'truncated' ||
       ourMessageTruncationStatus === 'unchanged' ||
       ourMessageTruncationStatus === 'exhaustive',
     'string is not ourMessageTruncationStatus enum',
   );
   return ourMessageTruncationStatus;
 }
 export type MessageTruncationStatuses = {
   [threadID: string]: MessageTruncationStatus,
 };
 
 export type ThreadCursors = { +[threadID: string]: ?string };
 
 export type MessageSelectionCriteria = {
   +threadCursors?: ?ThreadCursors,
   +joinedThreads?: ?boolean,
   +newerThan?: ?number,
 };
 
 export type FetchMessageInfosRequest = {
   +cursors: ThreadCursors,
   +numberPerThread?: ?number,
 };
 export type FetchMessageInfosResponse = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +userInfos: UserInfos,
 };
 export type FetchMessageInfosResult = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
 };
 export type FetchMessageInfosPayload = {
   +threadID: string,
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatus: MessageTruncationStatus,
 };
 export type MessagesResponse = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +currentAsOf: number,
 };
 export type SimpleMessagesPayload = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
 };
 export const defaultNumberPerThread = 20;
 export const defaultMaxMessageAge = 14 * 24 * 60 * 60 * 1000; // 2 weeks
 
 export type SendMessageResponse = {
   +newMessageInfo: RawMessageInfo,
 };
 export type SendMessageResult = {
   +id: string,
   +time: number,
   +interface: CallServerEndpointResultInfoInterface,
 };
 
 export type SendMessagePayload = {
   +localID: string,
   +serverID: string,
   +threadID: string,
   +time: number,
   +interface: CallServerEndpointResultInfoInterface,
 };
 
 export type SendTextMessageRequest = {
   +threadID: string,
   +localID?: string,
   +text: string,
   +sidebarCreation?: boolean,
 };
 export type SendMultimediaMessageRequest =
   // This option is only used for messageTypes.IMAGES
   | {
       +threadID: string,
       +localID: string,
       +sidebarCreation?: boolean,
       +mediaIDs: $ReadOnlyArray<string>,
     }
   | {
       +threadID: string,
       +localID: string,
       +sidebarCreation?: boolean,
       +mediaMessageContents: $ReadOnlyArray<MediaMessageServerDBContent>,
     };
 
 export type SendReactionMessageRequest = {
   +threadID: string,
   +localID?: string,
   +targetMessageID: string,
   +reaction: string,
   +action: 'add_reaction' | 'remove_reaction',
 };
 
 export type SendEditMessageRequest = {
   +targetMessageID: string,
   +text: string,
 };
 
 export type SendEditMessageResponse = {
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 };
 
 export type EditMessagePayload = SendEditMessageResponse;
 export type SendEditMessageResult = SendEditMessageResponse;
 
 export type EditMessageContent = {
   +text: string,
 };
 
 // Used for the message info included in log-in type actions
 export type GenericMessagesResult = {
   +messageInfos: RawMessageInfo[],
   +truncationStatus: MessageTruncationStatuses,
   +watchedIDsAtRequestTime: $ReadOnlyArray<string>,
   +currentAsOf: number,
 };
 
 export type SaveMessagesPayload = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +updatesCurrentAsOf: number,
 };
 
 export type NewMessagesPayload = {
   +messagesResult: MessagesResponse,
 };
 
 export type MessageStorePrunePayload = {
   +threadIDs: $ReadOnlyArray<string>,
 };
+
+export type FetchPinnedMessagesRequest = {
+  +threadID: string,
+};
+
+export type FetchPinnedMessagesResult = {
+  +pinnedMessages: $ReadOnlyArray<RawMessageInfo>,
+};