diff --git a/lib/permissions/thread-permissions.js b/lib/permissions/thread-permissions.js
index c895a7177..f28f54991 100644
--- a/lib/permissions/thread-permissions.js
+++ b/lib/permissions/thread-permissions.js
@@ -1,508 +1,554 @@
 // @flow
 
 import invariant from 'invariant';
 
 import {
   parseThreadPermissionString,
   includeThreadPermissionForThreadType,
 } from './prefixes.js';
 import {
   configurableCommunityPermissions,
   threadPermissionFilterPrefixes,
   threadPermissionPropagationPrefixes,
   threadPermissions,
   userSurfacedPermissions,
 } from '../types/thread-permission-types.js';
 import type {
   ThreadPermission,
   ThreadPermissionInfo,
   ThreadPermissionsBlob,
   ThreadPermissionsInfo,
   ThreadRolePermissionsBlob,
   UserSurfacedPermission,
 } from '../types/thread-permission-types.js';
 import {
   type ThreadType,
+  type ThinThreadType,
+  type ThickThreadType,
   threadTypes,
   threadTypeIsAnnouncementThread,
+  threadTypeIsThick,
+  assertThickThreadType,
+  assertThinThreadType,
 } from '../types/thread-types-enum.js';
 
 function permissionLookup(
   permissions: ?ThreadPermissionsBlob | ?ThreadPermissionsInfo,
   permission: ThreadPermission,
 ): boolean {
   return !!(
     permissions &&
     permissions[permission] &&
     permissions[permission].value &&
     permissions[threadPermissions.KNOW_OF] &&
     permissions[threadPermissions.KNOW_OF].value
   );
 }
 
 function getAllThreadPermissions(
   permissions: ?ThreadPermissionsBlob,
   threadID: string,
 ): ThreadPermissionsInfo {
   const result: { [permission: ThreadPermission]: ThreadPermissionInfo } = {};
   for (const permissionName in threadPermissions) {
     const permissionKey = threadPermissions[permissionName];
     const permission = permissionLookup(permissions, permissionKey);
     let entry: ThreadPermissionInfo = { value: false, source: null };
     if (permission) {
       const blobEntry = permissions ? permissions[permissionKey] : null;
       if (blobEntry) {
         invariant(
           blobEntry.value,
           'permissionLookup returned true but blob had false permission!',
         );
         entry = { value: true, source: blobEntry.source };
       } else {
         entry = { value: true, source: threadID };
       }
     }
     result[permissionKey] = entry;
   }
   return result;
 }
 
 // - rolePermissions can be null if role <= 0, ie. not a member
 // - permissionsFromParent can be null if there are no permissions from the
 //   parent
 // - return can be null if no permissions exist
 function makePermissionsBlob(
   rolePermissions: ?ThreadRolePermissionsBlob,
   permissionsFromParent: ?ThreadPermissionsBlob,
   threadID: string,
   threadType: ThreadType,
 ): ?ThreadPermissionsBlob {
   let permissions: { [permission: string]: ThreadPermissionInfo } = {};
 
   if (permissionsFromParent) {
     for (const permissionKey in permissionsFromParent) {
       const permissionValue = permissionsFromParent[permissionKey];
       const parsed = parseThreadPermissionString(permissionKey);
       if (!includeThreadPermissionForThreadType(parsed, threadType)) {
         continue;
       }
       if (parsed.propagationPrefix) {
         permissions[permissionKey] = permissionValue;
       } else {
         permissions[parsed.permission] = permissionValue;
       }
     }
   }
 
   const combinedPermissions: {
     [permission: string]: ThreadPermissionInfo,
   } = { ...permissions };
   if (rolePermissions) {
     for (const permissionKey in rolePermissions) {
       const permissionValue = rolePermissions[permissionKey];
       const currentValue = combinedPermissions[permissionKey];
       if (permissionValue) {
         combinedPermissions[permissionKey] = {
           value: true,
           source: threadID,
         };
       } else if (!currentValue || !currentValue.value) {
         combinedPermissions[permissionKey] = {
           value: false,
           source: null,
         };
       }
     }
   }
   if (permissionLookup(combinedPermissions, threadPermissions.KNOW_OF)) {
     permissions = combinedPermissions;
   }
 
   const threadIsAnnouncementThread = threadTypeIsAnnouncementThread(threadType);
   const hasVoicedInAnnouncementChannelsPermission = permissionLookup(
     (permissions: ThreadPermissionsBlob),
     threadPermissions.VOICED_IN_ANNOUNCEMENT_CHANNELS,
   );
   const isMember = !!rolePermissions;
 
   if (
     threadIsAnnouncementThread &&
     hasVoicedInAnnouncementChannelsPermission &&
     isMember
   ) {
     permissions[threadPermissions.VOICED] = {
       value: true,
       source: threadID,
     };
   }
 
   if (Object.keys(permissions).length === 0) {
     return null;
   }
 
   return permissions;
 }
 
 function makePermissionsForChildrenBlob(
   permissions: ?ThreadPermissionsBlob,
 ): ?ThreadPermissionsBlob {
   if (!permissions) {
     return null;
   }
   const permissionsForChildren: { [permission: string]: ThreadPermissionInfo } =
     {};
   for (const permissionKey in permissions) {
     const permissionValue = permissions[permissionKey];
     const parsed = parseThreadPermissionString(permissionKey);
     if (!parsed.propagationPrefix) {
       continue;
     }
     if (
       parsed.propagationPrefix ===
       threadPermissionPropagationPrefixes.DESCENDANT
     ) {
       permissionsForChildren[permissionKey] = permissionValue;
     }
     const permissionWithFilterPrefix = parsed.filterPrefix
       ? `${parsed.filterPrefix}${parsed.permission}`
       : parsed.permission;
     permissionsForChildren[permissionWithFilterPrefix] = permissionValue;
   }
   if (Object.keys(permissionsForChildren).length === 0) {
     return null;
   }
   return permissionsForChildren;
 }
 
 function getRoleForPermissions(
   inputRole: string,
   permissions: ?ThreadPermissionsBlob,
 ): string {
   if (!permissionLookup(permissions, threadPermissions.KNOW_OF)) {
     return '-1';
   } else if (Number(inputRole) <= 0) {
     return '0';
   } else {
     return inputRole;
   }
 }
 
 function getThreadPermissionBlobFromUserSurfacedPermissions(
   communityUserSurfacedPermissions: $ReadOnlyArray<UserSurfacedPermission>,
-  threadType: ThreadType,
+  threadType: ThinThreadType,
 ): ThreadRolePermissionsBlob {
   const mappedUserSurfacedPermissions = communityUserSurfacedPermissions
     .map(permission => [...configurableCommunityPermissions[permission]])
     .flat();
 
   const userSurfacedPermissionsObj = Object.fromEntries(
     mappedUserSurfacedPermissions.map(p => [p, true]),
   );
 
   const universalCommunityPermissions =
     getUniversalCommunityRootPermissionsBlob(threadType);
 
   return {
     ...universalCommunityPermissions,
     ...userSurfacedPermissionsObj,
   };
 }
 
 export type RolePermissionBlobs = {
   +Members: ThreadRolePermissionsBlob,
   +Admins?: ThreadRolePermissionsBlob,
 };
 
 const { CHILD, DESCENDANT } = threadPermissionPropagationPrefixes;
 const { OPEN, TOP_LEVEL, OPEN_TOP_LEVEL } = threadPermissionFilterPrefixes;
 const OPEN_CHILD = CHILD + OPEN;
 const OPEN_DESCENDANT = DESCENDANT + OPEN;
 const TOP_LEVEL_DESCENDANT = DESCENDANT + TOP_LEVEL;
 const OPEN_TOP_LEVEL_DESCENDANT = DESCENDANT + OPEN_TOP_LEVEL;
 
 const baseMemberUserSurfacedPermissions = [
   userSurfacedPermissions.REACT_TO_MESSAGES,
   userSurfacedPermissions.EDIT_MESSAGES,
   userSurfacedPermissions.ADD_MEMBERS,
 ];
 const baseVoicedUserSurfacedPermissions = [
   userSurfacedPermissions.EDIT_CALENDAR,
   userSurfacedPermissions.CREATE_AND_EDIT_CHANNELS,
 ];
 
 function getRolePermissionBlobsForCommunityRoot(
-  threadType: ThreadType,
+  threadType: ThinThreadType,
 ): RolePermissionBlobs {
   let memberUserSurfacedPermissions;
   if (threadType === threadTypes.GENESIS) {
     memberUserSurfacedPermissions = [];
   } else if (threadType === threadTypes.COMMUNITY_ANNOUNCEMENT_ROOT) {
     memberUserSurfacedPermissions = baseMemberUserSurfacedPermissions;
   } else {
     memberUserSurfacedPermissions = [
       ...baseMemberUserSurfacedPermissions,
       ...baseVoicedUserSurfacedPermissions,
     ];
   }
 
   const memberPermissions = getThreadPermissionBlobFromUserSurfacedPermissions(
     memberUserSurfacedPermissions,
     threadType,
   );
 
   const descendantKnowOf = DESCENDANT + threadPermissions.KNOW_OF;
   const descendantVisible = DESCENDANT + threadPermissions.VISIBLE;
   const topLevelDescendantJoinThread =
     TOP_LEVEL_DESCENDANT + threadPermissions.JOIN_THREAD;
   const childJoinThread = CHILD + threadPermissions.JOIN_THREAD;
   const descendantVoiced = DESCENDANT + threadPermissions.VOICED;
   const descendantEditEntries = DESCENDANT + threadPermissions.EDIT_ENTRIES;
   const descendantEditThreadName =
     DESCENDANT + threadPermissions.EDIT_THREAD_NAME;
   const descendantEditThreadColor =
     DESCENDANT + threadPermissions.EDIT_THREAD_COLOR;
   const descendantEditThreadDescription =
     DESCENDANT + threadPermissions.EDIT_THREAD_DESCRIPTION;
   const descendantEditThreadAvatar =
     DESCENDANT + threadPermissions.EDIT_THREAD_AVATAR;
   const topLevelDescendantCreateSubchannels =
     TOP_LEVEL_DESCENDANT + threadPermissions.CREATE_SUBCHANNELS;
   const topLevelDescendantCreateSidebars =
     TOP_LEVEL_DESCENDANT + threadPermissions.CREATE_SIDEBARS;
   const descendantAddMembers = DESCENDANT + threadPermissions.ADD_MEMBERS;
   const descendantDeleteThread = DESCENDANT + threadPermissions.DELETE_THREAD;
   const descendantEditPermissions =
     DESCENDANT + threadPermissions.EDIT_PERMISSIONS;
   const descendantRemoveMembers = DESCENDANT + threadPermissions.REMOVE_MEMBERS;
   const descendantChangeRole = DESCENDANT + threadPermissions.CHANGE_ROLE;
   const descendantManagePins = DESCENDANT + threadPermissions.MANAGE_PINS;
   const topLevelDescendantVoicedInAnnouncementChannels =
     TOP_LEVEL_DESCENDANT + threadPermissions.VOICED_IN_ANNOUNCEMENT_CHANNELS;
 
   const baseAdminPermissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
     [threadPermissions.VOICED]: true,
     [threadPermissions.REACT_TO_MESSAGE]: true,
     [threadPermissions.EDIT_MESSAGE]: true,
     [threadPermissions.EDIT_ENTRIES]: true,
     [threadPermissions.EDIT_THREAD_NAME]: true,
     [threadPermissions.EDIT_THREAD_COLOR]: true,
     [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
     [threadPermissions.EDIT_THREAD_AVATAR]: true,
     [threadPermissions.CREATE_SUBCHANNELS]: true,
     [threadPermissions.CREATE_SIDEBARS]: true,
     [threadPermissions.DELETE_THREAD]: true,
     [threadPermissions.REMOVE_MEMBERS]: true,
     [threadPermissions.CHANGE_ROLE]: true,
     [threadPermissions.MANAGE_PINS]: true,
     [threadPermissions.MANAGE_INVITE_LINKS]: true,
     [threadPermissions.VOICED_IN_ANNOUNCEMENT_CHANNELS]: true,
     [threadPermissions.MANAGE_FARCASTER_CHANNEL_TAGS]: true,
     [descendantKnowOf]: true,
     [descendantVisible]: true,
     [topLevelDescendantJoinThread]: true,
     [childJoinThread]: true,
     [descendantVoiced]: true,
     [descendantEditEntries]: true,
     [descendantEditThreadName]: true,
     [descendantEditThreadColor]: true,
     [descendantEditThreadDescription]: true,
     [descendantEditThreadAvatar]: true,
     [topLevelDescendantCreateSubchannels]: true,
     [topLevelDescendantCreateSidebars]: true,
     [descendantAddMembers]: true,
     [descendantDeleteThread]: true,
     [descendantEditPermissions]: true,
     [descendantRemoveMembers]: true,
     [descendantChangeRole]: true,
     [descendantManagePins]: true,
     [topLevelDescendantVoicedInAnnouncementChannels]: true,
   };
 
   let adminPermissions;
   if (threadType === threadTypes.GENESIS) {
     adminPermissions = {
       ...baseAdminPermissions,
       [threadPermissions.ADD_MEMBERS]: true,
     };
   } else {
     adminPermissions = {
       ...baseAdminPermissions,
       [threadPermissions.LEAVE_THREAD]: true,
     };
   }
 
   return {
     Members: memberPermissions,
     Admins: adminPermissions,
   };
 }
 
 const nonCommunityVoicedPermissions = {
   [threadPermissions.VOICED]: true,
   [threadPermissions.EDIT_ENTRIES]: true,
   [threadPermissions.EDIT_THREAD_NAME]: true,
   [threadPermissions.EDIT_THREAD_COLOR]: true,
   [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
   [threadPermissions.EDIT_THREAD_AVATAR]: true,
   [threadPermissions.CREATE_SUBCHANNELS]: true,
   [threadPermissions.ADD_MEMBERS]: true,
 };
 
 function getRolePermissionBlobs(threadType: ThreadType): RolePermissionBlobs {
-  if (threadType === threadTypes.SIDEBAR) {
+  if (threadTypeIsThick(threadType)) {
+    const thickThreadType = assertThickThreadType(threadType);
+    const memberPermissions =
+      getThickThreadRolePermissionsBlob(thickThreadType);
+    return {
+      Members: memberPermissions,
+    };
+  }
+  const thinThreadType = assertThinThreadType(threadType);
+
+  if (thinThreadType === threadTypes.SIDEBAR) {
     const memberPermissions = {
       [threadPermissions.VOICED]: true,
       [threadPermissions.REACT_TO_MESSAGE]: true,
       [threadPermissions.EDIT_MESSAGE]: true,
       [threadPermissions.EDIT_THREAD_NAME]: true,
       [threadPermissions.EDIT_THREAD_COLOR]: true,
       [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
       [threadPermissions.EDIT_THREAD_AVATAR]: true,
       [threadPermissions.ADD_MEMBERS]: true,
       [threadPermissions.EDIT_PERMISSIONS]: true,
       [threadPermissions.REMOVE_MEMBERS]: true,
       [threadPermissions.LEAVE_THREAD]: true,
     };
     return {
       Members: memberPermissions,
     };
   }
 
   const openDescendantKnowOf = OPEN_DESCENDANT + threadPermissions.KNOW_OF;
   const openDescendantVisible = OPEN_DESCENDANT + threadPermissions.VISIBLE;
   const openChildJoinThread = OPEN_CHILD + threadPermissions.JOIN_THREAD;
 
-  if (threadType === threadTypes.GENESIS_PRIVATE) {
+  if (thinThreadType === threadTypes.GENESIS_PRIVATE) {
     const memberPermissions = {
       [threadPermissions.KNOW_OF]: true,
       [threadPermissions.VISIBLE]: true,
       [threadPermissions.VOICED]: true,
       [threadPermissions.REACT_TO_MESSAGE]: true,
       [threadPermissions.EDIT_MESSAGE]: true,
       [threadPermissions.EDIT_THREAD_COLOR]: true,
       [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
       [threadPermissions.CREATE_SIDEBARS]: true,
       [threadPermissions.EDIT_ENTRIES]: true,
       [openDescendantKnowOf]: true,
       [openDescendantVisible]: true,
       [openChildJoinThread]: true,
     };
     return {
       Members: memberPermissions,
     };
   }
 
-  if (threadType === threadTypes.GENESIS_PERSONAL) {
+  if (thinThreadType === threadTypes.GENESIS_PERSONAL) {
     return {
       Members: {
         [threadPermissions.KNOW_OF]: true,
         [threadPermissions.VISIBLE]: true,
         [threadPermissions.VOICED]: true,
         [threadPermissions.REACT_TO_MESSAGE]: true,
         [threadPermissions.EDIT_MESSAGE]: true,
         [threadPermissions.EDIT_ENTRIES]: true,
         [threadPermissions.EDIT_THREAD_NAME]: true,
         [threadPermissions.EDIT_THREAD_COLOR]: true,
         [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
         [threadPermissions.CREATE_SIDEBARS]: true,
         [openDescendantKnowOf]: true,
         [openDescendantVisible]: true,
         [openChildJoinThread]: true,
       },
     };
   }
 
   const openTopLevelDescendantJoinThread =
     OPEN_TOP_LEVEL_DESCENDANT + threadPermissions.JOIN_THREAD;
 
   const subthreadBasePermissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
     [threadPermissions.REACT_TO_MESSAGE]: true,
     [threadPermissions.EDIT_MESSAGE]: true,
     [threadPermissions.CREATE_SIDEBARS]: true,
     [threadPermissions.LEAVE_THREAD]: true,
     [openDescendantKnowOf]: true,
     [openDescendantVisible]: true,
     [openTopLevelDescendantJoinThread]: true,
     [openChildJoinThread]: true,
   };
 
   if (
-    threadType === threadTypes.COMMUNITY_OPEN_SUBTHREAD ||
-    threadType === threadTypes.COMMUNITY_SECRET_SUBTHREAD
+    thinThreadType === threadTypes.COMMUNITY_OPEN_SUBTHREAD ||
+    thinThreadType === threadTypes.COMMUNITY_SECRET_SUBTHREAD
   ) {
     const memberPermissions = {
       [threadPermissions.REMOVE_MEMBERS]: true,
       [threadPermissions.EDIT_PERMISSIONS]: true,
       ...subthreadBasePermissions,
       ...nonCommunityVoicedPermissions,
     };
     return {
       Members: memberPermissions,
     };
   }
 
   if (
-    threadType === threadTypes.COMMUNITY_OPEN_ANNOUNCEMENT_SUBTHREAD ||
-    threadType === threadTypes.COMMUNITY_SECRET_ANNOUNCEMENT_SUBTHREAD
+    thinThreadType === threadTypes.COMMUNITY_OPEN_ANNOUNCEMENT_SUBTHREAD ||
+    thinThreadType === threadTypes.COMMUNITY_SECRET_ANNOUNCEMENT_SUBTHREAD
   ) {
     return {
       Members: subthreadBasePermissions,
     };
   }
 
-  return getRolePermissionBlobsForCommunityRoot(threadType);
+  return getRolePermissionBlobsForCommunityRoot(thinThreadType);
 }
 
 // ESLint doesn't recognize that invariant always throws
 // eslint-disable-next-line consistent-return
 function getUniversalCommunityRootPermissionsBlob(
-  threadType: ThreadType,
+  threadType: ThinThreadType,
 ): ThreadRolePermissionsBlob {
   const openDescendantKnowOf = OPEN_DESCENDANT + threadPermissions.KNOW_OF;
   const openDescendantVisible = OPEN_DESCENDANT + threadPermissions.VISIBLE;
   const openChildJoinThread = OPEN_CHILD + threadPermissions.JOIN_THREAD;
   const openTopLevelDescendantJoinThread =
     OPEN_TOP_LEVEL_DESCENDANT + threadPermissions.JOIN_THREAD;
 
   const genesisUniversalCommunityPermissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
     [openDescendantKnowOf]: true,
     [openDescendantVisible]: true,
     [openTopLevelDescendantJoinThread]: true,
   };
 
   const baseUniversalCommunityPermissions = {
     ...genesisUniversalCommunityPermissions,
     [threadPermissions.CREATE_SIDEBARS]: true,
     [threadPermissions.LEAVE_THREAD]: true,
     [openChildJoinThread]: true,
   };
 
   if (threadType === threadTypes.GENESIS) {
     return genesisUniversalCommunityPermissions;
   } else if (threadType === threadTypes.COMMUNITY_ANNOUNCEMENT_ROOT) {
     return baseUniversalCommunityPermissions;
   } else if (threadType === threadTypes.COMMUNITY_ROOT) {
     return {
       ...baseUniversalCommunityPermissions,
       [threadPermissions.VOICED]: true,
     };
   }
 
   invariant(false, 'invalid threadType parameter');
 }
 
+function getThickThreadRolePermissionsBlob(
+  threadType: ThickThreadType,
+): ThreadRolePermissionsBlob {
+  invariant(threadTypeIsThick(threadType), 'ThreadType should be thick');
+  const basePermissions = {
+    [threadPermissions.KNOW_OF]: true,
+    [threadPermissions.VISIBLE]: true,
+    [threadPermissions.VOICED]: true,
+    [threadPermissions.REACT_TO_MESSAGE]: true,
+    [threadPermissions.EDIT_MESSAGE]: true,
+    [threadPermissions.EDIT_THREAD_NAME]: true,
+    [threadPermissions.EDIT_THREAD_COLOR]: true,
+    [threadPermissions.EDIT_THREAD_DESCRIPTION]: true,
+    [threadPermissions.EDIT_THREAD_AVATAR]: true,
+    [threadPermissions.ADD_MEMBERS]: true,
+    [threadPermissions.LEAVE_THREAD]: true,
+  };
+  if (threadType === threadTypes.THICK_SIDEBAR) {
+    return {
+      ...basePermissions,
+      [threadPermissions.JOIN_THREAD]: true,
+    };
+  }
+  return {
+    ...basePermissions,
+    [threadPermissions.EDIT_ENTRIES]: true,
+    [threadPermissions.CREATE_SIDEBARS]: true,
+  };
+}
+
 export {
   permissionLookup,
   getAllThreadPermissions,
   makePermissionsBlob,
   makePermissionsForChildrenBlob,
   getRoleForPermissions,
   getThreadPermissionBlobFromUserSurfacedPermissions,
   getRolePermissionBlobs,
   getUniversalCommunityRootPermissionsBlob,
+  getThickThreadRolePermissionsBlob,
 };