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>

api/test/db/migrations/0023_mention_everyone.test.ts

@@ -0,0 +1,39 @@
+import "../../setup.ts";
+import { assertEquals } from "@std/assert";
+import { DatabaseSync } from "node:sqlite";
+import { up as up0023 } from "../../../db/migrations/0023_mention_everyone.ts";
+
+Deno.test("migration 0023 flags past @everyone and frees the name", () => {
+  const db = new DatabaseSync(":memory:");
+  db.exec(`
+    CREATE TABLE users (id TEXT PRIMARY KEY, username TEXT, role TEXT);
+    CREATE TABLE user_aliases (username TEXT PRIMARY KEY, user_id TEXT);
+    CREATE TABLE chat_messages (id TEXT PRIMARY KEY, user_id TEXT, body TEXT);
+    INSERT INTO users VALUES
+      ('m', 'mod', 'moderator'), ('u', 'Everyone', 'user'),
+      ('t', 'everyone_2', 'user'), ('a', 'ann', 'user');
+    INSERT INTO user_aliases VALUES ('everyone_3', 't'), ('EVERYONE', 'a');
+    INSERT INTO chat_messages VALUES
+      ('1', 'm', 'hi @everyone'), ('3', 'u', 'hi @everyone'),
+      ('4', 'm', 'hi all');
+  `);
+  // In code, it says nothing.
+  db.prepare(`INSERT INTO chat_messages VALUES ('2', 'm', ?);`).run(
+    "hi `@everyone`",
+  );
+  up0023(db);
+  up0023(db); // idempotent
+
+  const flagged = db.prepare(
+    `SELECT id FROM chat_messages WHERE mentions_everyone = 1;`,
+  ).all() as { id: string }[];
+  assertEquals(flagged.map((r) => r.id), ["1"]);
+  const names = db.prepare(`SELECT id, username FROM users ORDER BY id;`)
+    .all() as { id: string; username: string }[];
+  assertEquals(names.find((r) => r.id === "u")?.username, "everyone_4");
+  const aliases = db.prepare(`SELECT username FROM user_aliases;`).all() as {
+    username: string;
+  }[];
+  assertEquals(aliases.map((r) => r.username), ["everyone_3"]);
+  db.close();
+});