diff --git a/lib/shared/updates/join-thread-spec.js b/lib/shared/updates/join-thread-spec.js
--- a/lib/shared/updates/join-thread-spec.js
+++ b/lib/shared/updates/join-thread-spec.js
@@ -178,4 +178,7 @@
     truncationStatus: messageTruncationStatusValidator,
     rawEntryInfos: t.list(rawEntryInfoValidator),
   }),
+  getUpdatedThreadInfo(update: ThreadJoinUpdateInfo) {
+    return update.threadInfo;
+  },
 });
diff --git a/lib/shared/updates/update-spec.js b/lib/shared/updates/update-spec.js
--- a/lib/shared/updates/update-spec.js
+++ b/lib/shared/updates/update-spec.js
@@ -14,9 +14,11 @@
   MessageTruncationStatuses,
   FetchMessageInfosResult,
 } from '../../types/message-types.js';
+import type { RawThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import type {
   RawThreadInfos,
   MixedRawThreadInfos,
+  LegacyRawThreadInfo,
 } from '../../types/thread-types.js';
 import type { UpdateType } from '../../types/update-types-enum.js';
 import type {
@@ -103,4 +105,8 @@
   +generateOpsForUserInfoUpdates?: (
     update: UpdateInfo,
   ) => ?$ReadOnlyArray<UserStoreOperation>,
+  +getUpdatedThreadInfo?: (
+    update: UpdateInfo,
+    threadInfo: LegacyRawThreadInfo | RawThreadInfo,
+  ) => LegacyRawThreadInfo | RawThreadInfo,
 };
diff --git a/lib/shared/updates/update-thread-read-status-spec.js b/lib/shared/updates/update-thread-read-status-spec.js
--- a/lib/shared/updates/update-thread-read-status-spec.js
+++ b/lib/shared/updates/update-thread-read-status-spec.js
@@ -3,7 +3,11 @@
 import t from 'tcomb';
 
 import type { UpdateSpec } from './update-spec.js';
-import type { RawThreadInfos } from '../../types/thread-types.js';
+import type { RawThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
+import type {
+  LegacyRawThreadInfo,
+  RawThreadInfos,
+} from '../../types/thread-types.js';
 import { updateTypes } from '../../types/update-types-enum.js';
 import type {
   ThreadReadStatusUpdateInfo,
@@ -106,4 +110,25 @@
     threadID: tID,
     unread: t.Boolean,
   }),
+  getUpdatedThreadInfo(
+    update: ThreadReadStatusUpdateInfo,
+    threadInfo: LegacyRawThreadInfo | RawThreadInfo,
+  ): LegacyRawThreadInfo | RawThreadInfo {
+    if (threadInfo.minimallyEncoded) {
+      return {
+        ...threadInfo,
+        currentUser: {
+          ...threadInfo.currentUser,
+          unread: update.unread,
+        },
+      };
+    }
+    return {
+      ...threadInfo,
+      currentUser: {
+        ...threadInfo.currentUser,
+        unread: update.unread,
+      },
+    };
+  },
 });
diff --git a/lib/shared/updates/update-thread-spec.js b/lib/shared/updates/update-thread-spec.js
--- a/lib/shared/updates/update-thread-spec.js
+++ b/lib/shared/updates/update-thread-spec.js
@@ -119,4 +119,7 @@
     time: t.Number,
     threadInfo: mixedRawThreadInfoValidator,
   }),
+  getUpdatedThreadInfo(update: ThreadUpdateInfo) {
+    return update.threadInfo;
+  },
 });