diff --git a/lib/permissions/minimally-encoded-thread-permissions-test-data.js b/lib/permissions/minimally-encoded-thread-permissions-test-data.js
--- a/lib/permissions/minimally-encoded-thread-permissions-test-data.js
+++ b/lib/permissions/minimally-encoded-thread-permissions-test-data.js
@@ -305,12 +305,14 @@
   parentThreadID: '1',
   members: [
     {
+      minimallyEncoded: true,
       id: '256',
       role: null,
       permissions: '87fff',
       isSender: false,
     },
     {
+      minimallyEncoded: true,
       id: '83853',
       role: '85172',
       permissions: '3027f',
@@ -319,6 +321,7 @@
   ],
   roles: {
     '85172': {
+      minimallyEncoded: true,
       id: '85172',
       name: 'Members',
       permissions: [
@@ -340,6 +343,7 @@
     },
   },
   currentUser: {
+    minimallyEncoded: true,
     role: '85172',
     permissions: '3027f',
     subscription: {
diff --git a/lib/permissions/minimally-encoded-thread-permissions.js b/lib/permissions/minimally-encoded-thread-permissions.js
--- a/lib/permissions/minimally-encoded-thread-permissions.js
+++ b/lib/permissions/minimally-encoded-thread-permissions.js
@@ -220,15 +220,17 @@
     ]),
   );
 
-export type MinimallyEncodedRoleInfo = {
+export type MinimallyEncodedRoleInfo = $ReadOnly<{
   ...RoleInfo,
+  +minimallyEncoded: true,
   +permissions: $ReadOnlyArray<string>,
-};
+}>;
 
 const tHexEncodedRolePermission: TRegex = tRegex(/^[0-9a-fA-F]{3,}$/);
 const minimallyEncodedRoleInfoValidator: TInterface<MinimallyEncodedRoleInfo> =
   tShape<MinimallyEncodedRoleInfo>({
     ...roleInfoValidator.meta.props,
+    minimallyEncoded: tBool(true),
     permissions: t.list(tHexEncodedRolePermission),
   });
 
@@ -236,27 +238,33 @@
   roleInfo: RoleInfo,
 ): MinimallyEncodedRoleInfo => ({
   ...roleInfo,
+  minimallyEncoded: true,
   permissions: threadRolePermissionsBlobToBitmaskArray(roleInfo.permissions),
 });
 
 const decodeMinimallyEncodedRoleInfo = (
   minimallyEncodedRoleInfo: MinimallyEncodedRoleInfo,
-): RoleInfo => ({
-  ...minimallyEncodedRoleInfo,
-  permissions: decodeThreadRolePermissionsBitmaskArray(
-    minimallyEncodedRoleInfo.permissions,
-  ),
-});
+): RoleInfo => {
+  const { minimallyEncoded, ...rest } = minimallyEncodedRoleInfo;
+  return {
+    ...rest,
+    permissions: decodeThreadRolePermissionsBitmaskArray(
+      minimallyEncodedRoleInfo.permissions,
+    ),
+  };
+};
 
-export type MinimallyEncodedThreadCurrentUserInfo = {
+export type MinimallyEncodedThreadCurrentUserInfo = $ReadOnly<{
   ...ThreadCurrentUserInfo,
+  +minimallyEncoded: true,
   +permissions: string,
-};
+}>;
 
 const tHexEncodedPermissionsBitmask: TRegex = tRegex(/^[0-9a-fA-F]+$/);
 const minimallyEncodedThreadCurrentUserInfoValidator: TInterface<MinimallyEncodedThreadCurrentUserInfo> =
   tShape<MinimallyEncodedThreadCurrentUserInfo>({
     ...threadCurrentUserInfoValidator.meta.props,
+    minimallyEncoded: tBool(true),
     permissions: tHexEncodedPermissionsBitmask,
   });
 
@@ -264,26 +272,32 @@
   threadCurrentUserInfo: ThreadCurrentUserInfo,
 ): MinimallyEncodedThreadCurrentUserInfo => ({
   ...threadCurrentUserInfo,
+  minimallyEncoded: true,
   permissions: permissionsToBitmaskHex(threadCurrentUserInfo.permissions),
 });
 
 const decodeMinimallyEncodedThreadCurrentUserInfo = (
   minimallyEncodedThreadCurrentUserInfo: MinimallyEncodedThreadCurrentUserInfo,
-): ThreadCurrentUserInfo => ({
-  ...minimallyEncodedThreadCurrentUserInfo,
-  permissions: threadPermissionsFromBitmaskHex(
-    minimallyEncodedThreadCurrentUserInfo.permissions,
-  ),
-});
+): ThreadCurrentUserInfo => {
+  const { minimallyEncoded, ...rest } = minimallyEncodedThreadCurrentUserInfo;
+  return {
+    ...rest,
+    permissions: threadPermissionsFromBitmaskHex(
+      minimallyEncodedThreadCurrentUserInfo.permissions,
+    ),
+  };
+};
 
-export type MinimallyEncodedMemberInfo = {
+export type MinimallyEncodedMemberInfo = $ReadOnly<{
   ...MemberInfo,
+  +minimallyEncoded: true,
   +permissions: string,
-};
+}>;
 
 const minimallyEncodedMemberInfoValidator: TInterface<MinimallyEncodedMemberInfo> =
   tShape<MinimallyEncodedMemberInfo>({
     ...memberInfoValidator.meta.props,
+    minimallyEncoded: tBool(true),
     permissions: tHexEncodedPermissionsBitmask,
   });
 
@@ -291,30 +305,34 @@
   memberInfo: MemberInfo,
 ): MinimallyEncodedMemberInfo => ({
   ...memberInfo,
+  minimallyEncoded: true,
   permissions: permissionsToBitmaskHex(memberInfo.permissions),
 });
 
 const decodeMinimallyEncodedMemberInfo = (
   minimallyEncodedMemberInfo: MinimallyEncodedMemberInfo,
-): MemberInfo => ({
-  ...minimallyEncodedMemberInfo,
-  permissions: threadPermissionsFromBitmaskHex(
-    minimallyEncodedMemberInfo.permissions,
-  ),
-});
+): MemberInfo => {
+  const { minimallyEncoded, ...rest } = minimallyEncodedMemberInfo;
+  return {
+    ...rest,
+    permissions: threadPermissionsFromBitmaskHex(
+      minimallyEncodedMemberInfo.permissions,
+    ),
+  };
+};
 
-export type MinimallyEncodedRawThreadInfo = {
-  minimallyEncoded: true,
+export type MinimallyEncodedRawThreadInfo = $ReadOnly<{
   ...RawThreadInfo,
+  +minimallyEncoded: true,
   +members: $ReadOnlyArray<MinimallyEncodedMemberInfo>,
   +roles: { +[id: string]: MinimallyEncodedRoleInfo },
   +currentUser: MinimallyEncodedThreadCurrentUserInfo,
-};
+}>;
 
 const minimallyEncodedRawThreadInfoValidator: TInterface<MinimallyEncodedRawThreadInfo> =
   tShape<MinimallyEncodedRawThreadInfo>({
-    minimallyEncoded: tBool(true),
     ...rawThreadInfoValidator.meta.props,
+    minimallyEncoded: tBool(true),
     members: t.list(minimallyEncodedMemberInfoValidator),
     roles: t.dict(tID, minimallyEncodedRoleInfoValidator),
     currentUser: minimallyEncodedThreadCurrentUserInfoValidator,
@@ -325,8 +343,8 @@
 ): MinimallyEncodedRawThreadInfo => {
   const { members, roles, currentUser, ...rest } = rawThreadInfo;
   return {
-    minimallyEncoded: true,
     ...rest,
+    minimallyEncoded: true,
     members: members.map(minimallyEncodeMemberInfo),
     roles: _mapValues(minimallyEncodeRoleInfo)(roles),
     currentUser: minimallyEncodeThreadCurrentUserInfo(currentUser),
diff --git a/lib/permissions/minimally-encoded-thread-permissions.test.js b/lib/permissions/minimally-encoded-thread-permissions.test.js
--- a/lib/permissions/minimally-encoded-thread-permissions.test.js
+++ b/lib/permissions/minimally-encoded-thread-permissions.test.js
@@ -277,6 +277,7 @@
   it('should validate correctly formed MinimallyEncodedRoleInfo', () => {
     expect(
       minimallyEncodedRoleInfoValidator.is({
+        minimallyEncoded: true,
         id: 'roleID',
         name: 'roleName',
         permissions: ['abc', 'def'],
@@ -337,12 +338,14 @@
   it('should validate correctly formed MinimallyEncodedThreadCurrentUserInfo', () => {
     expect(
       minimallyEncodedThreadCurrentUserInfoValidator.is({
+        minimallyEncoded: true,
         permissions: '100',
         subscription: { home: true, pushNotifs: true },
       }),
     ).toBe(true);
     expect(
       minimallyEncodedThreadCurrentUserInfoValidator.is({
+        minimallyEncoded: true,
         permissions: 'ABCDEFABCDEFABCD',
         subscription: { home: true, pushNotifs: true },
       }),
@@ -352,6 +355,7 @@
   it('should NOT validate malformed MinimallyEncodedThreadCurrentUserInfo', () => {
     expect(
       minimallyEncodedThreadCurrentUserInfoValidator.is({
+        minimallyEncoded: true,
         permissions: 'INVALID',
         subscription: { home: true, pushNotifs: true },
       }),
@@ -359,6 +363,7 @@
 
     expect(
       minimallyEncodedThreadCurrentUserInfoValidator.is({
+        minimallyEncoded: true,
         permissions: 'ABCDEF  hello  ABCDEFABCD',
         subscription: { home: true, pushNotifs: true },
       }),
@@ -366,6 +371,7 @@
 
     expect(
       minimallyEncodedThreadCurrentUserInfoValidator.is({
+        minimallyEncoded: true,
         permissions: 100,
         subscription: { home: true, pushNotifs: true },
       }),
@@ -377,6 +383,7 @@
   it('should validate correctly formed MinimallyEncodedMemberInfo', () => {
     expect(
       minimallyEncodedMemberInfoValidator.is({
+        minimallyEncoded: true,
         id: 'memberID',
         permissions: 'ABCDEF',
         isSender: true,
@@ -385,6 +392,7 @@
 
     expect(
       minimallyEncodedMemberInfoValidator.is({
+        minimallyEncoded: true,
         id: 'memberID',
         permissions: '01b',
         isSender: false,
@@ -395,6 +403,7 @@
   it('should NOT validate malformed MinimallyEncodedMemberInfo', () => {
     expect(
       minimallyEncodedMemberInfoValidator.is({
+        minimallyEncoded: true,
         id: 'memberID',
         permissions: 'INVALID',
         isSender: false,
@@ -403,6 +412,7 @@
 
     expect(
       minimallyEncodedMemberInfoValidator.is({
+        minimallyEncoded: true,
         id: 'memberID',
         permissions: 100,
         isSender: false,