diff --git a/lib/shared/dm-ops/send-text-message-spec.js b/lib/shared/dm-ops/send-text-message-spec.js
--- a/lib/shared/dm-ops/send-text-message-spec.js
+++ b/lib/shared/dm-ops/send-text-message-spec.js
@@ -1,14 +1,40 @@
 // @flow
 
+import uuid from 'uuid';
+
 import type { DMOperationSpec } from './dm-op-spec.js';
 import type { DMSendTextMessageOperation } from '../../types/dm-ops.js';
+import { messageTypes } from '../../types/message-types-enum.js';
+import { updateTypes } from '../../types/update-types-enum.js';
+import type { ClientUpdateInfo } from '../../types/update-types.js';
 
 export const sendTextMessageSpec: DMOperationSpec<DMSendTextMessageOperation> =
   Object.freeze({
-    processDMOperation: async () => {
+    processDMOperation: async (
+      dmOperation: DMSendTextMessageOperation,
+      viewerID: string,
+    ) => {
+      const { threadID, creatorID, time, text } = dmOperation;
+      const textMessage = {
+        type: messageTypes.TEXT,
+        threadID,
+        creatorID,
+        time,
+        text,
+      };
+      const updateInfos: Array<ClientUpdateInfo> = [];
+      if (creatorID !== viewerID) {
+        updateInfos.push({
+          type: updateTypes.UPDATE_THREAD_READ_STATUS,
+          id: uuid.v4(),
+          time,
+          threadID,
+          unread: true,
+        });
+      }
       return {
-        rawMessageInfos: [],
-        updateInfos: [],
+        rawMessageInfos: [textMessage],
+        updateInfos,
       };
     },
   });