diff --git a/lib/permissions/minimally-encoded-raw-thread-info-validators.js b/lib/permissions/minimally-encoded-raw-thread-info-validators.js
--- a/lib/permissions/minimally-encoded-raw-thread-info-validators.js
+++ b/lib/permissions/minimally-encoded-raw-thread-info-validators.js
@@ -12,6 +12,8 @@
   ThreadCurrentUserInfo,
   RawThreadInfo,
   RoleInfo,
+  RoleInfoWithoutSpecialRole,
+  RawThreadInfoWithoutSpecialRole,
 } from '../types/minimally-encoded-thread-permissions-types.js';
 import {
   type LegacyRawThreadInfo,
@@ -28,11 +30,15 @@
     permissions: tHexEncodedPermissionsBitmask,
   });
 
-const roleInfoValidator: TInterface<RoleInfo> = tShape<RoleInfo>({
+const roleInfoValidatorBase = {
   id: tID,
   name: t.String,
   minimallyEncoded: tBool(true),
   permissions: t.list(tHexEncodedRolePermission),
+};
+
+const roleInfoValidator: TInterface<RoleInfo> = tShape<RoleInfo>({
+  ...roleInfoValidatorBase,
   specialRole: t.maybe(specialRoleValidator),
 });
 
@@ -72,8 +78,25 @@
   },
 );
 
-const mixedRawThreadInfoValidator: TUnion<LegacyRawThreadInfo | RawThreadInfo> =
-  t.union([legacyRawThreadInfoValidator, rawThreadInfoValidator]);
+const roleInfoWithoutSpecialRolesValidator: TInterface<RoleInfoWithoutSpecialRole> =
+  tShape<RoleInfoWithoutSpecialRole>({
+    ...roleInfoValidatorBase,
+    isDefault: t.maybe(t.Boolean),
+  });
+
+const rawThreadInfoWithoutSpecialRoles: TInterface<RawThreadInfoWithoutSpecialRole> =
+  tShape<RawThreadInfoWithoutSpecialRole>({
+    ...rawThreadInfoValidator.meta.props,
+    roles: t.dict(tID, roleInfoWithoutSpecialRolesValidator),
+  });
+
+const mixedRawThreadInfoValidator: TUnion<
+  LegacyRawThreadInfo | RawThreadInfo | RawThreadInfoWithoutSpecialRole,
+> = t.union([
+  legacyRawThreadInfoValidator,
+  rawThreadInfoValidator,
+  rawThreadInfoWithoutSpecialRoles,
+]);
 
 export {
   memberInfoValidator,
diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -893,29 +893,27 @@
 
   if (!shouldMinimallyEncodePermissions) {
     return rawThreadInfo;
-  } else if (!shouldIncludeSpecialRoleFieldInRoles) {
-    return minimallyEncodeRawThreadInfo(rawThreadInfo);
   }
 
-  const rawThreadInfoWithoutSpecialRoles =
-    minimallyEncodeRawThreadInfo(rawThreadInfo);
+  const minimallyEncoded = minimallyEncodeRawThreadInfo(rawThreadInfo);
+  if (shouldIncludeSpecialRoleFieldInRoles) {
+    return minimallyEncoded;
+  }
 
-  const rolesWithSpecialRoleField = Object.fromEntries(
-    entries(rawThreadInfoWithoutSpecialRoles.roles).map(([key, role]) => [
+  const minimallyEncodedRolesWithoutSpecialRoleField = Object.fromEntries(
+    entries(minimallyEncoded.roles).map(([key, role]) => [
       key,
       {
-        ..._omit('isDefault')(role),
-        specialRole: rolesWithFilteredThreadPermissions[key]?.specialRole,
+        ..._omit('specialRole')(role),
+        isDefault: roleIsDefaultRole(role),
       },
     ]),
   );
 
-  const rawThreadInfoWithSpecialRolesPatchedIn = {
-    ...rawThreadInfoWithoutSpecialRoles,
-    roles: rolesWithSpecialRoleField,
+  return {
+    ...minimallyEncoded,
+    roles: minimallyEncodedRolesWithoutSpecialRoleField,
   };
-
-  return rawThreadInfoWithSpecialRolesPatchedIn;
 }
 
 function threadUIName(threadInfo: ThreadInfo): string | ThreadEntity {
diff --git a/lib/types/minimally-encoded-thread-permissions-types.js b/lib/types/minimally-encoded-thread-permissions-types.js
--- a/lib/types/minimally-encoded-thread-permissions-types.js
+++ b/lib/types/minimally-encoded-thread-permissions-types.js
@@ -22,11 +22,15 @@
 import { roleIsAdminRole, roleIsDefaultRole } from '../shared/thread-utils.js';
 import type { ThreadEntity } from '../utils/entity-text.js';
 
-export type RoleInfo = $ReadOnly<{
+type RoleInfoBase = $ReadOnly<{
   +id: string,
   +name: string,
   +minimallyEncoded: true,
   +permissions: $ReadOnlyArray<string>,
+}>;
+
+export type RoleInfo = $ReadOnly<{
+  ...RoleInfoBase,
   +specialRole?: ?SpecialRole,
 }>;
 
@@ -171,6 +175,16 @@
   };
 };
 
+export type RoleInfoWithoutSpecialRole = $ReadOnly<{
+  ...RoleInfoBase,
+  +isDefault?: boolean,
+}>;
+
+export type RawThreadInfoWithoutSpecialRole = $ReadOnly<{
+  ...RawThreadInfo,
+  +roles: { +[id: string]: RoleInfoWithoutSpecialRole },
+}>;
+
 export type ThreadInfo = $ReadOnly<{
   +minimallyEncoded: true,
   +id: string,