diff --git a/lib/hooks/thread-hooks.js b/lib/hooks/thread-hooks.js
index 6ad26c09a..a4226daf4 100644
--- a/lib/hooks/thread-hooks.js
+++ b/lib/hooks/thread-hooks.js
@@ -1,49 +1,126 @@
 // @flow
 
+import invariant from 'invariant';
 import * as React from 'react';
+import uuid from 'uuid';
 
 import { useChatMentionContext } from './chat-mention-hooks.js';
 import genesis from '../facts/genesis.js';
 import { childThreadInfos } from '../selectors/thread-selectors.js';
+import {
+  type OutboundDMOperationSpecification,
+  dmOperationSpecificationTypes,
+} from '../shared/dm-ops/dm-op-utils.js';
+import { useProcessAndSendDMOperation } from '../shared/dm-ops/process-dm-ops.js';
+import type {
+  DMCreateSidebarOperation,
+  DMCreateThreadOperation,
+} from '../types/dm-ops';
 import type { ResolvedThreadInfo } from '../types/minimally-encoded-thread-permissions-types.js';
+import { threadTypes } from '../types/thread-types-enum.js';
+import type { NewThickThreadRequest } from '../types/thread-types.js';
 import { useSelector } from '../utils/redux-utils.js';
 
 function useChildThreadInfosMap(): {
   +[id: string]: $ReadOnlyArray<ResolvedThreadInfo>,
 } {
   const childThreadInfosMap = useSelector(childThreadInfos);
 
   const { getCommunityThreadIDForGenesisThreads, chatMentionCandidatesObj } =
     useChatMentionContext();
 
   return React.useMemo(() => {
     const result: { [id: string]: $ReadOnlyArray<ResolvedThreadInfo> } = {};
     for (const parentThreadID in childThreadInfosMap) {
       result[parentThreadID] = childThreadInfosMap[parentThreadID]
         .map(rawThreadInfo => {
           const communityThreadIDForGenesisThreads =
             getCommunityThreadIDForGenesisThreads(rawThreadInfo);
           const community =
             rawThreadInfo.community === genesis().id
               ? communityThreadIDForGenesisThreads
               : rawThreadInfo.community ?? rawThreadInfo.id;
           if (!community) {
             return undefined;
           }
           const communityThreads = chatMentionCandidatesObj[community];
           if (!communityThreads) {
             return undefined;
           }
           return communityThreads[rawThreadInfo.id]?.threadInfo;
         })
         .filter(Boolean);
     }
     return result;
   }, [
     childThreadInfosMap,
     getCommunityThreadIDForGenesisThreads,
     chatMentionCandidatesObj,
   ]);
 }
 
-export { useChildThreadInfosMap };
+function useNewThickThread(): (
+  input: NewThickThreadRequest,
+) => Promise<string> {
+  const processAndSendDMOperation = useProcessAndSendDMOperation();
+  const viewerID = useSelector(
+    state => state.currentUserInfo && state.currentUserInfo.id,
+  );
+
+  return React.useCallback(
+    async (input: NewThickThreadRequest) => {
+      invariant(viewerID, 'viewerID must be defined');
+      const threadID = input.id ?? uuid.v4();
+
+      let op;
+      if (input.type === threadTypes.THICK_SIDEBAR) {
+        const { parentThreadID, sourceMessageID, initialMemberIDs } = input;
+        invariant(
+          parentThreadID,
+          'parentThreadID has to be defined for thick sidebar',
+        );
+        const sidebarOP: DMCreateSidebarOperation = {
+          creatorID: viewerID,
+          memberIDs: initialMemberIDs ?? [],
+          newCreateSidebarMessageID: uuid.v4(),
+          newSidebarSourceMessageID: uuid.v4(),
+          parentThreadID: parentThreadID,
+          roleID: uuid.v4(),
+          sourceMessageID: sourceMessageID,
+          threadID,
+          time: Date.now(),
+          type: 'create_sidebar',
+        };
+        op = sidebarOP;
+      } else {
+        const { type, initialMemberIDs } = input;
+
+        const threadOP: DMCreateThreadOperation = {
+          creatorID: viewerID,
+          memberIDs: initialMemberIDs ?? [],
+          newMessageID: uuid.v4(),
+          roleID: uuid.v4(),
+          threadID,
+          threadType: type,
+          time: Date.now(),
+          type: 'create_thread',
+        };
+        op = threadOP;
+      }
+      const userIDs = [...(input.initialMemberIDs ?? []), viewerID];
+      const opSpecification: OutboundDMOperationSpecification = {
+        type: dmOperationSpecificationTypes.OUTBOUND,
+        op,
+        recipients: {
+          type: 'some_users',
+          userIDs,
+        },
+      };
+      await processAndSendDMOperation(opSpecification);
+      return threadID;
+    },
+    [processAndSendDMOperation, viewerID],
+  );
+}
+
+export { useChildThreadInfosMap, useNewThickThread };
diff --git a/lib/types/thread-types.js b/lib/types/thread-types.js
index 5537a840b..cc828cfed 100644
--- a/lib/types/thread-types.js
+++ b/lib/types/thread-types.js
@@ -1,506 +1,518 @@
 // @flow
 
 import t, { type TInterface } from 'tcomb';
 
 import {
   type AvatarDBContent,
   type ClientAvatar,
   clientAvatarValidator,
   type UpdateUserAvatarRequest,
 } from './avatar-types.js';
 import type { CalendarQuery } from './entry-types.js';
 import type { Media } from './media-types.js';
 import type {
   MessageTruncationStatuses,
   RawMessageInfo,
 } from './message-types.js';
 import type {
   RawThreadInfo,
   ResolvedThreadInfo,
   ThreadInfo,
   ThickRawThreadInfo,
 } from './minimally-encoded-thread-permissions-types.js';
 import {
   type ThreadSubscription,
   threadSubscriptionValidator,
 } from './subscription-types.js';
 import {
   type ThreadPermissionsInfo,
   threadPermissionsInfoValidator,
   type ThreadRolePermissionsBlob,
   threadRolePermissionsBlobValidator,
   type UserSurfacedPermission,
 } from './thread-permission-types.js';
 import {
   type ThinThreadType,
   type ThickThreadType,
   threadTypeValidator,
 } from './thread-types-enum.js';
 import type { ClientUpdateInfo, ServerUpdateInfo } from './update-types.js';
 import type { UserInfo, UserInfos } from './user-types.js';
 import type { SpecialRole } from '../permissions/special-roles.js';
 import { type ThreadEntity } from '../utils/entity-text.js';
 import { tID, tShape, tUserID } from '../utils/validation-utils.js';
 
 export type LegacyMemberInfo = {
   +id: string,
   +role: ?string,
   +permissions: ThreadPermissionsInfo,
   +isSender: boolean,
 };
 export const legacyMemberInfoValidator: TInterface<LegacyMemberInfo> =
   tShape<LegacyMemberInfo>({
     id: tUserID,
     role: t.maybe(tID),
     permissions: threadPermissionsInfoValidator,
     isSender: t.Boolean,
   });
 
 export type ClientLegacyRoleInfo = {
   +id: string,
   +name: string,
   +permissions: ThreadRolePermissionsBlob,
   +isDefault: boolean,
 };
 export const clientLegacyRoleInfoValidator: TInterface<ClientLegacyRoleInfo> =
   tShape<ClientLegacyRoleInfo>({
     id: tID,
     name: t.String,
     permissions: threadRolePermissionsBlobValidator,
     isDefault: t.Boolean,
   });
 
 export type ServerLegacyRoleInfo = {
   +id: string,
   +name: string,
   +permissions: ThreadRolePermissionsBlob,
   +isDefault: boolean,
   +specialRole: ?SpecialRole,
 };
 
 export type LegacyThreadCurrentUserInfo = {
   +role: ?string,
   +permissions: ThreadPermissionsInfo,
   +subscription: ThreadSubscription,
   +unread: ?boolean,
 };
 export const legacyThreadCurrentUserInfoValidator: TInterface<LegacyThreadCurrentUserInfo> =
   tShape<LegacyThreadCurrentUserInfo>({
     role: t.maybe(tID),
     permissions: threadPermissionsInfoValidator,
     subscription: threadSubscriptionValidator,
     unread: t.maybe(t.Boolean),
   });
 
 export type LegacyThinRawThreadInfo = {
   +id: string,
   +type: ThinThreadType,
   +name?: ?string,
   +avatar?: ?ClientAvatar,
   +description?: ?string,
   +color: string, // hex, without "#" or "0x"
   +creationTime: number, // millisecond timestamp
   +parentThreadID: ?string,
   +containingThreadID?: ?string,
   +community: ?string,
   +members: $ReadOnlyArray<LegacyMemberInfo>,
   +roles: { +[id: string]: ClientLegacyRoleInfo },
   +currentUser: LegacyThreadCurrentUserInfo,
   +sourceMessageID?: string,
   +repliesCount: number,
   +pinnedCount?: number,
 };
 
 export type ThickMemberInfo = {
   +id: string,
   +role: ?string,
   +permissions: ThreadPermissionsInfo,
   +subscription: ThreadSubscription,
   +isSender: boolean,
 };
 
 export type ThreadTimestamps = {
   +name: number,
   +avatar: number,
   +description: number,
   +color: number,
   +members: {
     +[id: string]: {
       +isMember: number,
       +subscription: number,
     },
   },
   +currentUser: {
     +unread: number,
   },
 };
 
 export const threadTimestampsValidator: TInterface<ThreadTimestamps> =
   tShape<ThreadTimestamps>({
     name: t.Number,
     avatar: t.Number,
     description: t.Number,
     color: t.Number,
     members: t.dict(
       tUserID,
       tShape({
         isMember: t.Number,
         subscription: t.Number,
       }),
     ),
     currentUser: tShape({
       unread: t.Number,
     }),
   });
 
 export type LegacyThickRawThreadInfo = {
   +thick: true,
   +id: string,
   +type: ThickThreadType,
   +name?: ?string,
   +avatar?: ?ClientAvatar,
   +description?: ?string,
   +color: string, // hex, without "#" or "0x"
   +creationTime: number, // millisecond timestamp
   +parentThreadID?: ?string,
   +containingThreadID?: ?string,
   +members: $ReadOnlyArray<ThickMemberInfo>,
   +roles: { +[id: string]: ClientLegacyRoleInfo },
   +currentUser: LegacyThreadCurrentUserInfo,
   +sourceMessageID?: string,
   +repliesCount: number,
   +pinnedCount?: number,
   +timestamps: ThreadTimestamps,
 };
 
 export type LegacyRawThreadInfo =
   | LegacyThinRawThreadInfo
   | LegacyThickRawThreadInfo;
 
 export type LegacyRawThreadInfos = {
   +[id: string]: LegacyRawThreadInfo,
 };
 export const legacyRawThreadInfoValidator: TInterface<LegacyRawThreadInfo> =
   tShape<LegacyRawThreadInfo>({
     id: tID,
     type: threadTypeValidator,
     name: t.maybe(t.String),
     avatar: t.maybe(clientAvatarValidator),
     description: t.maybe(t.String),
     color: t.String,
     creationTime: t.Number,
     parentThreadID: t.maybe(tID),
     containingThreadID: t.maybe(tID),
     community: t.maybe(tID),
     members: t.list(legacyMemberInfoValidator),
     roles: t.dict(tID, clientLegacyRoleInfoValidator),
     currentUser: legacyThreadCurrentUserInfoValidator,
     sourceMessageID: t.maybe(tID),
     repliesCount: t.Number,
     pinnedCount: t.maybe(t.Number),
   });
 
 export type MixedRawThreadInfos = {
   +[id: string]: LegacyRawThreadInfo | RawThreadInfo,
 };
 export type ThickRawThreadInfos = {
   +[id: string]: ThickRawThreadInfo,
 };
 export type RawThreadInfos = {
   +[id: string]: RawThreadInfo,
 };
 
 export type ServerMemberInfo = {
   +id: string,
   +role: ?string,
   +permissions: ThreadPermissionsInfo,
   +subscription: ThreadSubscription,
   +unread: ?boolean,
   +isSender: boolean,
 };
 
 export type ServerThreadInfo = {
   +id: string,
   +type: ThinThreadType,
   +name: ?string,
   +avatar?: AvatarDBContent,
   +description: ?string,
   +color: string, // hex, without "#" or "0x"
   +creationTime: number, // millisecond timestamp
   +parentThreadID: ?string,
   +containingThreadID: ?string,
   +community: ?string,
   +depth: number,
   +members: $ReadOnlyArray<ServerMemberInfo>,
   +roles: { +[id: string]: ServerLegacyRoleInfo },
   +sourceMessageID?: string,
   +repliesCount: number,
   +pinnedCount: number,
 };
 
 export type LegacyThreadStore = {
   +threadInfos: MixedRawThreadInfos,
 };
 
 export type ThreadStore = {
   +threadInfos: RawThreadInfos,
 };
 
 export type ClientDBThreadInfo = {
   +id: string,
   +type: number,
   +name: ?string,
   +avatar?: ?string,
   +description: ?string,
   +color: string,
   +creationTime: string,
   +parentThreadID: ?string,
   +containingThreadID: ?string,
   +community: ?string,
   +members: string,
   +roles: string,
   +currentUser: string,
   +sourceMessageID?: string,
   +repliesCount: number,
   +pinnedCount?: number,
   +timestamps?: ?string,
 };
 
 export type ThreadDeletionRequest = {
   +threadID: string,
   +accountPassword?: empty,
 };
 
 export type RemoveMembersRequest = {
   +threadID: string,
   +memberIDs: $ReadOnlyArray<string>,
 };
 
 export type RoleChangeRequest = {
   +threadID: string,
   +memberIDs: $ReadOnlyArray<string>,
   +role: string,
 };
 
 export type ChangeThreadSettingsResult = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 };
 
 export type ChangeThreadSettingsPayload = {
   +threadID: string,
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 };
 
 export type LeaveThreadRequest = {
   +threadID: string,
 };
 export type LeaveThreadResult = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
 };
 
 export type LeaveThreadPayload = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
 };
 
 export type ThreadChanges = Partial<{
   +type: ThinThreadType,
   +name: string,
   +description: string,
   +color: string,
   +parentThreadID: ?string,
   +newMemberIDs: $ReadOnlyArray<string>,
   +avatar: UpdateUserAvatarRequest,
 }>;
 
 export type UpdateThreadRequest = {
   +threadID: string,
   +changes: ThreadChanges,
   +accountPassword?: empty,
 };
 
 export type BaseNewThreadRequest = {
   +id?: ?string,
   +name?: ?string,
   +description?: ?string,
   +color?: ?string,
   +parentThreadID?: ?string,
   +initialMemberIDs?: ?$ReadOnlyArray<string>,
   +ghostMemberIDs?: ?$ReadOnlyArray<string>,
 };
 type NewThinThreadRequest =
   | $ReadOnly<{
       +type: 3 | 4 | 6 | 7 | 8 | 9 | 10 | 11 | 12,
       ...BaseNewThreadRequest,
     }>
   | $ReadOnly<{
       +type: 5,
       +sourceMessageID: string,
       ...BaseNewThreadRequest,
     }>;
 
 export type ClientNewThinThreadRequest = $ReadOnly<{
   ...NewThinThreadRequest,
   +calendarQuery: CalendarQuery,
 }>;
 export type ServerNewThinThreadRequest = $ReadOnly<{
   ...NewThinThreadRequest,
   +calendarQuery?: ?CalendarQuery,
 }>;
 
+export type NewThickThreadRequest =
+  | $ReadOnly<{
+      +type: 13 | 14 | 15,
+      ...BaseNewThreadRequest,
+    }>
+  | $ReadOnly<{
+      +type: 16,
+      +sourceMessageID: string,
+      ...BaseNewThreadRequest,
+      +parentThreadID: string,
+    }>;
+
 export type NewThreadResponse = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +userInfos: UserInfos,
   +newThreadID: string,
 };
 export type NewThreadResult = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +userInfos: UserInfos,
   +newThreadID: string,
 };
 
 export type ServerThreadJoinRequest = {
   +threadID: string,
   +calendarQuery?: ?CalendarQuery,
   +inviteLinkSecret?: string,
   +defaultSubscription?: ThreadSubscription,
 };
 export type ClientThreadJoinRequest = {
   +threadID: string,
   +calendarQuery: CalendarQuery,
   +inviteLinkSecret?: string,
   +defaultSubscription?: ThreadSubscription,
 };
 export type ThreadJoinResult = {
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +userInfos: UserInfos,
 };
 export type ThreadJoinPayload = {
   +updatesResult: {
     newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +userInfos: $ReadOnlyArray<UserInfo>,
   +keyserverID: string,
 };
 
 export type ThreadFetchMediaResult = {
   +media: $ReadOnlyArray<Media>,
 };
 export type ThreadFetchMediaRequest = {
   +threadID: string,
   +limit: number,
   +offset: number,
 };
 
 export type SidebarInfo = {
   +threadInfo: ThreadInfo,
   +lastUpdatedTime: number,
   +mostRecentNonLocalMessage: ?string,
 };
 
 export type ToggleMessagePinRequest = {
   +messageID: string,
   +action: 'pin' | 'unpin',
 };
 
 export type ToggleMessagePinResult = {
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +threadID: string,
 };
 
 type CreateRoleAction = {
   +community: string,
   +name: string,
   +permissions: $ReadOnlyArray<UserSurfacedPermission>,
   +action: 'create_role',
 };
 
 type EditRoleAction = {
   +community: string,
   +existingRoleID: string,
   +name: string,
   +permissions: $ReadOnlyArray<UserSurfacedPermission>,
   +action: 'edit_role',
 };
 
 export type RoleModificationRequest = CreateRoleAction | EditRoleAction;
 
 export type RoleModificationResult = {
   +threadInfo: LegacyRawThreadInfo | RawThreadInfo,
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
 };
 
 export type RoleModificationPayload = {
   +threadInfo: LegacyRawThreadInfo | RawThreadInfo,
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
 };
 
 export type RoleDeletionRequest = {
   +community: string,
   +roleID: string,
 };
 
 export type RoleDeletionResult = {
   +threadInfo: LegacyRawThreadInfo | RawThreadInfo,
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ServerUpdateInfo>,
   },
 };
 
 export type RoleDeletionPayload = {
   +threadInfo: LegacyRawThreadInfo | RawThreadInfo,
   +updatesResult: {
     +newUpdates: $ReadOnlyArray<ClientUpdateInfo>,
   },
 };
 
 // We can show a max of 3 sidebars inline underneath their parent in the chat
 // tab. If there are more, we show a button that opens a modal to see the rest
 export const maxReadSidebars = 3;
 
 // We can show a max of 5 sidebars inline underneath their parent
 // in the chat tab if every one of the displayed sidebars is unread
 export const maxUnreadSidebars = 5;
 
 export type ThreadStoreThreadInfos = LegacyRawThreadInfos;
 
 export type ChatMentionCandidate = {
   +threadInfo: ResolvedThreadInfo,
   +rawChatName: string | ThreadEntity,
 };
 export type ChatMentionCandidates = {
   +[id: string]: ChatMentionCandidate,
 };
 export type ChatMentionCandidatesObj = {
   +[id: string]: ChatMentionCandidates,
 };
 
 export type UserProfileThreadInfo = {
   +threadInfo: ThreadInfo,
   +pendingPersonalThreadUserInfo?: UserInfo,
 };