diff --git a/lib/shared/markdown.js b/lib/shared/markdown.js
--- a/lib/shared/markdown.js
+++ b/lib/shared/markdown.js
@@ -3,7 +3,12 @@
 import invariant from 'invariant';
 
 import { markdownMentionRegex } from './mention-utils.js';
-import type { RelativeMemberInfo } from '../types/thread-types.js';
+import { validChatNameRegexString } from './thread-utils.js';
+import type {
+  RelativeMemberInfo,
+  ResolvedThreadInfo,
+  ChatMentionCandidates,
+} from '../types/thread-types.js';
 
 // simple-markdown types
 export type State = {
@@ -218,6 +223,37 @@
   return match;
 }
 
+const chatMentionRegexString = `^(?<!\\\\)(@\\[\\[([0-9,|]+):(${validChatNameRegexString}?)(?<!\\\\)\\]\\])`;
+const chatMentionRegex: RegExp = new RegExp(chatMentionRegexString);
+
+function matchChatMentions(): MatchFunction {
+  return (source: string, state: State) => {
+    if (!state.inline) {
+      return null;
+    }
+    const result = chatMentionRegex.exec(source);
+    return result;
+  };
+}
+
+function parseChatMention(
+  chatMentionCandidates: ChatMentionCandidates,
+  capture: Capture,
+): {
+  threadInfo: ?ResolvedThreadInfo,
+  content: string,
+  hasAccessToChat: boolean,
+} {
+  const threadInfo = chatMentionCandidates[capture[2]];
+  const threadName = threadInfo?.uiName ?? capture[3];
+  const content = `@${threadName}`;
+  return {
+    threadInfo,
+    content,
+    hasAccessToChat: !!threadInfo,
+  };
+}
+
 const blockQuoteRegex: RegExp = /^( *>[^\n]+(?:\n[^\n]+)*)(?:\n|$)/;
 const blockQuoteStripFollowingNewlineRegex: RegExp =
   /^( *>[^\n]+(?:\n[^\n]+)*)(?:\n|$){2}/;
@@ -317,4 +353,6 @@
   matchMentions,
   stripSpoilersFromNotifications,
   stripSpoilersFromMarkdownAST,
+  matchChatMentions,
+  parseChatMention,
 };
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
@@ -110,8 +110,8 @@
 const chatNameMaxLength = 191;
 const chatNameMinLength = 0;
 const secondCharRange = `{${chatNameMinLength},${chatNameMaxLength}}`;
-const validChatNameRegexString = `^.${secondCharRange}$`;
-const validChatNameRegex: RegExp = new RegExp(validChatNameRegexString);
+const validChatNameRegexString = `.${secondCharRange}`;
+const validChatNameRegex: RegExp = new RegExp(`^${validChatNameRegexString}$`);
 
 function threadHasPermission(
   threadInfo: ?(ThreadInfo | RawThreadInfo),
@@ -1777,6 +1777,7 @@
   getAvailableThreadMemberActions,
   threadMembersWithoutAddedAshoat,
   validChatNameRegex,
+  validChatNameRegexString,
   chatNameMaxLength,
   patchThreadInfoToIncludeMentionedMembersOfParent,
   threadInfoInsideCommunity,