v4: a moderator's or an admin's @everyone in the chat notifies every user — there was no way to reach everyone at once. The new chat:everyone permission, held by moderators and admins, lets a chat message saying @everyone notify every user but its author and those reading the chat, through notifyEveryone, after notifyMentions, so a user also named is told once, by name; the notification is a user_mentioned with everyone set, which the notifications page and the digest word as "mentioned everyone in the chat". chat_messages.mentions_everyone, sent as ChatMessage.mentionsEveryone, is set from the author's role each time the body is written, so a user's @everyone reaches no one, a moderator's edit of a user's message can't make it reach everyone, and a demoted author's next edit loses it. Only an edit that adds @everyone notifies, so fixing an announcement's typo reaches no one new. The client highlights and chimes by the flag, never by the text; Markdown shows @everyone as a mention only in a flagged message, and never links it to a profile. The chat composer offers @everyone first to those who may say it. No account may be named everyone, in any case: migration 0023 adds the column, flags the moderators' and admins' past @everyone messages, renames a user named everyone to everyone_N and drops an alias everyone. 265 backend tests and 681 frontend tests pass, and deno check, tsc, eslint, doc:lint and i18n:compile --strict are clean; checked in screenshots of the chat at 1280 and 390px, with a moderator's and a user's @everyone and the suggestions open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shared/permissions.ts

@@ -18,6 +18,7 @@ export type Permission =
   | "comment:moderate"
   | "playlist:moderate"
   | "chat:moderate"
+  | "chat:everyone"
   | "user:manage"
   | "category:manage";
 
@@ -26,13 +27,15 @@ const ALL_PERMISSIONS: readonly Permission[] = [
   "comment:moderate",
   "playlist:moderate",
   "chat:moderate",
+  "chat:everyone",
   "user:manage",
   "category:manage",
 ];
 
 /**
  * Read through {@link hasPermission}. Roles are fixed in code. An admin holds
- * every permission, and a moderator the moderation ones only.
+ * every permission, and a moderator the moderation ones and `@everyone` in
+ * the chat.
  */
 export const ROLE_PERMISSIONS: Record<Role, readonly Permission[]> = {
   admin: ALL_PERMISSIONS,
@@ -41,6 +44,7 @@ export const ROLE_PERMISSIONS: Record<Role, readonly Permission[]> = {
     "comment:moderate",
     "playlist:moderate",
     "chat:moderate",
+    "chat:everyone",
   ],
   user: [],
 };