diff --git a/lib/shared/mention-utils.js b/lib/shared/mention-utils.js
--- a/lib/shared/mention-utils.js
+++ b/lib/shared/mention-utils.js
@@ -2,7 +2,11 @@
 
 import { oldValidUsernameRegexString } from './account-utils.js';
 import SentencePrefixSearchIndex from './sentence-prefix-search-index.js';
-import { threadOtherMembers, chatNameMaxLength } from './thread-utils.js';
+import {
+  threadOtherMembers,
+  chatNameMaxLength,
+  extractThreadID,
+} from './thread-utils.js';
 import { stringForUserExplicit } from './user-utils.js';
 import { threadTypes } from '../types/thread-types-enum.js';
 import type {
@@ -11,6 +15,7 @@
   ResolvedThreadInfo,
   ChatMentionCandidates,
 } from '../types/thread-types.js';
+import { ET, entityTextToRawString } from '../utils/entity-text.js';
 import { idSchemaRegex } from '../utils/validation-utils.js';
 
 export type TypeaheadMatchedStrings = {
@@ -58,8 +63,54 @@
   'g',
 );
 
-const chatMentionRegexString = `^(?<!\\\\)(@\\[\\[(${idSchemaRegex}):(.{1,${chatNameMaxLength}}?)(?<!\\\\)\\]\\])`;
-const chatMentionRegex: RegExp = new RegExp(chatMentionRegexString);
+const chatMentionRegexString = `(?<!\\\\)(@\\[\\[(${idSchemaRegex}):(.{1,${chatNameMaxLength}}?)(?<!\\\\)\\]\\])`;
+const chatMentionRegex: RegExp = new RegExp(`^${chatMentionRegexString}`);
+const globalChatMentionRegex: RegExp = new RegExp(chatMentionRegexString, 'g');
+
+function extractChatMentions(text: string): $ReadOnlyArray<{
+  +threadID: string,
+  +defaultText: string,
+}> {
+  const matches = text.matchAll(globalChatMentionRegex);
+  if (!matches) {
+    return [];
+  }
+  const result = [];
+  for (const match of matches) {
+    result.push({
+      threadID: match[2],
+      defaultText: match[3],
+    });
+  }
+  return result;
+}
+
+function renderChatMentions(
+  text: string,
+  threadInfos: { +[idWithoutKeyserverPrefix: string]: ThreadInfo },
+  mentionableThreadIDs: $ReadOnlySet<string>,
+): string {
+  const matches = text.matchAll(globalChatMentionRegex);
+  if (!matches) {
+    return text;
+  }
+  let newText = text;
+  for (const match of matches) {
+    const threadID = extractThreadID(match[2]);
+    if (mentionableThreadIDs.has(threadID) && threadInfos[threadID]) {
+      const mentionedThreadInfo = threadInfos[threadID];
+      const thread = ET.thread({
+        display: 'uiName',
+        threadInfo: mentionedThreadInfo,
+      });
+      const threadName = entityTextToRawString(ET`${thread}`);
+      newText = newText.replace(match[0], `@${threadName}`);
+    } else {
+      newText = newText.replace(match[0], `@${match[3]}`);
+    }
+  }
+  return newText;
+}
 
 function encodeChatMentionText(text: string): string {
   return text.replace(/]/g, '\\]');
@@ -182,4 +233,6 @@
   chatMentionRegex,
   encodeChatMentionText,
   decodeChatMentionText,
+  extractChatMentions,
+  renderChatMentions,
 };
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
@@ -1810,6 +1810,10 @@
   ];
 }
 
+function extractThreadID(threadID: string): string {
+  return threadID.slice(threadID.indexOf('|') + 1);
+}
+
 export {
   threadHasPermission,
   viewerIsMember,
@@ -1882,4 +1886,5 @@
   useChatMentionCandidatesObj,
   useThreadChatMentionCandidates,
   useThreadChatMentionSearchIndex,
+  extractThreadID,
 };