diff --git a/lib/permissions/thread-permissions.js b/lib/permissions/thread-permissions.js
--- a/lib/permissions/thread-permissions.js
+++ b/lib/permissions/thread-permissions.js
@@ -466,6 +466,10 @@
   threadType: ThickThreadType,
 ): ThreadRolePermissionsBlob {
   invariant(threadTypeIsThick(threadType), 'ThreadType should be thick');
+  const openDescendantKnowOf = OPEN_DESCENDANT + threadPermissions.KNOW_OF;
+  const openDescendantVisible = OPEN_DESCENDANT + threadPermissions.VISIBLE;
+  const openChildJoinThread = OPEN_CHILD + threadPermissions.JOIN_THREAD;
+
   const basePermissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
@@ -493,6 +497,9 @@
       ...basePermissions,
       [threadPermissions.EDIT_ENTRIES]: true,
       [threadPermissions.CREATE_SIDEBARS]: true,
+      [openDescendantKnowOf]: true,
+      [openDescendantVisible]: true,
+      [openChildJoinThread]: true,
     };
   }
   return {
@@ -501,6 +508,9 @@
     [threadPermissions.CREATE_SIDEBARS]: true,
     [threadPermissions.ADD_MEMBERS]: true,
     [threadPermissions.LEAVE_THREAD]: true,
+    [openDescendantKnowOf]: true,
+    [openDescendantVisible]: true,
+    [openChildJoinThread]: true,
   };
 }
 
diff --git a/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js b/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
--- a/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
+++ b/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
@@ -55,7 +55,7 @@
     ) => {
       const { time, messageID, addedUserIDs, existingThreadDetails } =
         dmOperation;
-      const { viewerID, threadInfos } = utilities;
+      const { threadInfos } = utilities;
 
       const { rawMessageInfo } =
         createAddViewerToThreadMembersMessageDataWithInfoFromDMOp(dmOperation);
@@ -115,7 +115,7 @@
             },
           },
         },
-        viewerID,
+        utilities,
       );
       const updateInfos = [
         {
diff --git a/lib/shared/dm-ops/create-sidebar-spec.js b/lib/shared/dm-ops/create-sidebar-spec.js
--- a/lib/shared/dm-ops/create-sidebar-spec.js
+++ b/lib/shared/dm-ops/create-sidebar-spec.js
@@ -153,7 +153,7 @@
           containingThreadID: parentThreadID,
           timestamps: createThreadTimestamps(time, allMemberIDs),
         },
-        viewerID,
+        utilities,
       );
 
       const { sidebarSourceMessageInfo, createSidebarMessageInfo } =
diff --git a/lib/shared/dm-ops/create-thread-spec.js b/lib/shared/dm-ops/create-thread-spec.js
--- a/lib/shared/dm-ops/create-thread-spec.js
+++ b/lib/shared/dm-ops/create-thread-spec.js
@@ -1,5 +1,6 @@
 // @flow
 
+import invariant from 'invariant';
 import uuid from 'uuid';
 
 import type {
@@ -11,6 +12,7 @@
   getAllThreadPermissions,
   makePermissionsBlob,
   getThickThreadRolePermissionsBlob,
+  makePermissionsForChildrenBlob,
 } from '../../permissions/thread-permissions.js';
 import type {
   CreateThickRawThreadInfoInput,
@@ -59,10 +61,41 @@
   };
 }
 
+function createPermissionsInfoForNonMembers(
+  threadID: string,
+  threadType: ThickThreadType,
+  parentThreadInfo: ?ThickRawThreadInfo,
+): ThreadPermissionsInfo {
+  if (!parentThreadInfo) {
+    return getAllThreadPermissions(
+      makePermissionsBlob(null, null, threadID, threadType),
+      threadID,
+    );
+  }
+  const parentThreadRolePermissions = getThickThreadRolePermissionsBlob(
+    parentThreadInfo.type,
+  );
+  const parentPermissionsBlob = makePermissionsBlob(
+    parentThreadRolePermissions,
+    null,
+    parentThreadInfo.id,
+    parentThreadInfo.type,
+  );
+  return getAllThreadPermissions(
+    makePermissionsBlob(
+      null,
+      makePermissionsForChildrenBlob(parentPermissionsBlob),
+      threadID,
+      threadType,
+    ),
+    threadID,
+  );
+}
+
 type MutableThickRawThreadInfo = { ...ThickRawThreadInfo };
 function createThickRawThreadInfo(
   input: CreateThickRawThreadInfoInput,
-  viewerID: string,
+  utilities: ProcessDMOperationUtilities,
 ): MutableThickRawThreadInfo {
   const {
     threadID,
@@ -89,6 +122,27 @@
   const { membershipPermissions, role } =
     createRoleAndPermissionForThickThreads(threadType, threadID, roleID);
 
+  const isViewerMember = allMemberIDsWithSubscriptions.some(
+    member => member.id === utilities.viewerID,
+  );
+  let viewerMembershipPermissions = membershipPermissions;
+  let viewerRoleID: ?string = role.id;
+  if (!isViewerMember) {
+    viewerRoleID = null;
+    const parentThreadInfo = parentThreadID
+      ? utilities.threadInfos[parentThreadID]
+      : null;
+    invariant(
+      !parentThreadInfo || parentThreadInfo.thick,
+      'Parent thread should be thick',
+    );
+    viewerMembershipPermissions = createPermissionsInfoForNonMembers(
+      threadID,
+      threadType,
+      parentThreadInfo,
+    );
+  }
+
   const newThread: MutableThickRawThreadInfo = {
     thick: true,
     minimallyEncoded: true,
@@ -101,9 +155,12 @@
       ({ id: memberID, subscription }) =>
         minimallyEncodeMemberInfo<ThickMemberInfo>({
           id: memberID,
-          role: role.id,
-          permissions: membershipPermissions,
-          isSender: memberID === viewerID,
+          role: memberID === utilities.viewerID ? viewerRoleID : role.id,
+          permissions:
+            memberID === utilities.viewerID
+              ? viewerMembershipPermissions
+              : membershipPermissions,
+          isSender: memberID === utilities.viewerID,
           subscription,
         }),
     ),
@@ -111,8 +168,8 @@
       [role.id]: role,
     },
     currentUser: minimallyEncodeThreadCurrentUserInfo({
-      role: role.id,
-      permissions: membershipPermissions,
+      role: viewerRoleID,
+      permissions: viewerMembershipPermissions,
       subscription: joinThreadSubscription,
       unread,
     }),
@@ -189,7 +246,7 @@
           unread: creatorID !== viewerID,
           timestamps: createThreadTimestamps(time, allMemberIDs),
         },
-        viewerID,
+        utilities,
       );
 
       const { rawMessageInfo } =
@@ -222,4 +279,5 @@
   createThickRawThreadInfo,
   createThreadSpec,
   createRoleAndPermissionForThickThreads,
+  createPermissionsInfoForNonMembers,
 };
diff --git a/lib/shared/dm-ops/join-thread-spec.js b/lib/shared/dm-ops/join-thread-spec.js
--- a/lib/shared/dm-ops/join-thread-spec.js
+++ b/lib/shared/dm-ops/join-thread-spec.js
@@ -118,7 +118,7 @@
             members: memberTimestamps,
           },
         },
-        viewerID,
+        utilities,
       );
       updateInfos.push({
         type: updateTypes.JOIN_THREAD,
diff --git a/lib/shared/dm-ops/leave-thread-spec.js b/lib/shared/dm-ops/leave-thread-spec.js
--- a/lib/shared/dm-ops/leave-thread-spec.js
+++ b/lib/shared/dm-ops/leave-thread-spec.js
@@ -3,10 +3,12 @@
 import invariant from 'invariant';
 import uuid from 'uuid';
 
+import { createPermissionsInfoForNonMembers } from './create-thread-spec.js';
 import type {
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
+import { permissionsToBitmaskHex } from '../../permissions/minimally-encoded-thread-permissions.js';
 import type { DMLeaveThreadOperation } from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { ThickRawThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
@@ -121,9 +123,33 @@
       ...memberTimestamps[editorID],
       isMember: time,
     };
+
+    let currentUser = threadInfo.currentUser;
+    if (editorID === viewerID) {
+      const parentThreadID = threadInfo.parentThreadID;
+      const parentThreadInfo = parentThreadID
+        ? utilities.threadInfos[parentThreadID]
+        : null;
+      invariant(
+        parentThreadInfo?.thick,
+        'Parent thread should be present and thick',
+      );
+      const viewerMembershipPermissions = createPermissionsInfoForNonMembers(
+        threadID,
+        threadInfo.type,
+        parentThreadInfo,
+      );
+      currentUser = {
+        ...currentUser,
+        role: null,
+        permissions: permissionsToBitmaskHex(viewerMembershipPermissions),
+      };
+    }
+
     const updatedThreadInfo = {
       ...threadInfo,
       members: threadInfo.members.filter(member => member.id !== editorID),
+      currentUser,
       timestamps: {
         ...threadInfo.timestamps,
         members: memberTimestamps,