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
@@ -348,8 +348,10 @@
 function getRolePermissionBlobs(threadType: ThreadType): RolePermissionBlobs {
   if (threadTypeIsThick(threadType)) {
     const thickThreadType = assertThickThreadType(threadType);
-    const memberPermissions =
-      getThickThreadRolePermissionsBlob(thickThreadType);
+    const memberPermissions = getThickThreadRolePermissionsBlob(
+      thickThreadType,
+      true,
+    );
     return {
       Members: memberPermissions,
     };
@@ -464,8 +466,20 @@
 
 function getThickThreadRolePermissionsBlob(
   threadType: ThickThreadType,
+  isMember: boolean,
 ): ThreadRolePermissionsBlob {
   invariant(threadTypeIsThick(threadType), 'ThreadType should be thick');
+
+  if (!isMember && threadType === threadTypes.THICK_SIDEBAR) {
+    return {
+      [threadPermissions.KNOW_OF]: true,
+      [threadPermissions.VISIBLE]: true,
+      [threadPermissions.JOIN_THREAD]: true,
+    };
+  } else if (!isMember) {
+    return {};
+  }
+
   const basePermissions = {
     [threadPermissions.KNOW_OF]: true,
     [threadPermissions.VISIBLE]: true,
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
@@ -36,7 +36,7 @@
   threadID: string,
   roleID: string,
 ): { +role: RoleInfo, +membershipPermissions: ThreadPermissionsInfo } {
-  const rolePermissions = getThickThreadRolePermissionsBlob(threadType);
+  const rolePermissions = getThickThreadRolePermissionsBlob(threadType, true);
   const membershipPermissions = getAllThreadPermissions(
     makePermissionsBlob(rolePermissions, null, threadID, threadType),
     threadID,
@@ -86,6 +86,23 @@
   const { membershipPermissions, role } =
     createRoleAndPermissionForThickThreads(threadType, threadID, roleID);
 
+  const isViewerMember = allMemberIDsWithSubscriptions.some(
+    member => member.id === viewerID,
+  );
+  let viewerMembershipPermissions = membershipPermissions;
+  let viewerRoleID: ?string = role.id;
+  if (!isViewerMember) {
+    const rolePermissions = getThickThreadRolePermissionsBlob(
+      threadType,
+      false,
+    );
+    viewerMembershipPermissions = getAllThreadPermissions(
+      makePermissionsBlob(rolePermissions, null, threadID, threadType),
+      threadID,
+    );
+    viewerRoleID = null;
+  }
+
   const newThread: MutableThickRawThreadInfo = {
     thick: true,
     minimallyEncoded: true,
@@ -98,8 +115,11 @@
       ({ id: memberID, subscription }) =>
         minimallyEncodeMemberInfo<ThickMemberInfo>({
           id: memberID,
-          role: role.id,
-          permissions: membershipPermissions,
+          role: memberID === viewerID ? viewerRoleID : role.id,
+          permissions:
+            memberID === viewerID
+              ? viewerMembershipPermissions
+              : membershipPermissions,
           isSender: memberID === viewerID,
           subscription,
         }),
@@ -108,8 +128,8 @@
       [role.id]: role,
     },
     currentUser: minimallyEncodeThreadCurrentUserInfo({
-      role: role.id,
-      permissions: membershipPermissions,
+      role: viewerRoleID,
+      permissions: viewerMembershipPermissions,
       subscription: joinThreadSubscription,
       unread,
     }),
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
@@ -7,6 +7,12 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
+import { permissionsToBitmaskHex } from '../../permissions/minimally-encoded-thread-permissions.js';
+import {
+  getAllThreadPermissions,
+  getThickThreadRolePermissionsBlob,
+  makePermissionsBlob,
+} from '../../permissions/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';
@@ -115,9 +121,30 @@
       ...memberTimestamps[editorID],
       isMember: time,
     };
+
+    let currentUser = threadInfo.currentUser;
+    if (editorID === viewerID) {
+      const rolePermissions = getThickThreadRolePermissionsBlob(
+        threadInfo.type,
+        false,
+      );
+      const viewerMembershipPermissions = permissionsToBitmaskHex(
+        getAllThreadPermissions(
+          makePermissionsBlob(rolePermissions, null, threadID, threadInfo.type),
+          threadID,
+        ),
+      );
+      currentUser = {
+        ...currentUser,
+        role: null,
+        permissions: viewerMembershipPermissions,
+      };
+    }
+
     const updatedThreadInfo = {
       ...threadInfo,
       members: threadInfo.members.filter(member => member.id !== editorID),
+      currentUser,
       timestamps: {
         ...threadInfo.timestamps,
         members: memberTimestamps,