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/routes/users.test.ts

@@ -669,6 +669,19 @@ test("renaming: the old name redirects for good, and nobody else can take it", a
   assertEquals((await rename(other.id, old)).status, 409);
   // Nor to a current one.
   assertEquals((await rename(other.id, renamed)).status, 409);
+  // Nor to everyone, in any case, which the chat's @everyone takes.
+  assertEquals((await rename(other.id, "Everyone")).status, 409);
+  assertEquals(
+    (await post("/api/users", {
+      json: {
+        username: "everyone",
+        password: PASSWORD,
+        email: `${uniqueName()}@example.test`,
+        inviteToken: invite(other.id),
+      },
+    })).status,
+    409,
+  );
   // Signing in takes the current name only.
   assertEquals(
     (await post("/api/sessions", {

api/test/routes/ws.test.ts

@@ -448,6 +448,73 @@ wsTest(
   },
 );
 
+wsTest(
+  "chat: @everyone notifies all who aren't reading, when its author may say it",
+  async (connect) => {
+    const mod = await createUser({ role: "moderator" });
+    const user = await createUser();
+    const named = await createUser();
+    const reader = await createUser();
+    const m = await connect(mod);
+    const u = await connect(user);
+    const r = await connect(reader);
+    r.send({ type: "chat_focus", open: true });
+    await r.sync();
+    const mentioned = () =>
+      Object.fromEntries(
+        (db.prepare(
+          `SELECT user_id, data FROM notifications WHERE type = 'user_mentioned';`,
+        ).all() as { user_id: string; data: string }[])
+          .map((row) => [row.user_id, !!JSON.parse(row.data).everyone]),
+      );
+
+    // A user's @everyone reaches no one.
+    u.send({ type: "chat_send", body: "@everyone hi" });
+    const plain = (await m.next("chat_message")).message;
+    assertEquals(plain.mentionsEveryone, undefined);
+    assertEquals(mentioned(), {});
+
+    // A moderator's reaches all but its author and the reader, and a user
+    // named too is told by name.
+    m.send({
+      type: "chat_send",
+      body: `@Everyone, and @${named.username}`,
+    });
+    const byMod = (x: { message: { userId: string } }) =>
+      x.message.userId === mod.id;
+    const sent = (await u.next("chat_message", byMod)).message;
+    assertEquals(sent.mentionsEveryone, true);
+    const expected = { [user.id]: true, [named.id]: false };
+    assertEquals(mentioned(), expected);
+
+    // Fixing a typo reaches no one new, not even a newcomer.
+    const late = await createUser();
+    m.send({ type: "chat_edit", id: sent.id, body: "@everyone, and all" });
+    await u.next("chat_message_updated");
+    assertEquals(mentioned(), expected);
+
+    // A moderator's edit can't make a user's message reach everyone.
+    m.send({ type: "chat_edit", id: plain.id, body: "@everyone edited" });
+    const edited = (await u.next("chat_message_updated")).message;
+    assertEquals(edited.mentionsEveryone, undefined);
+    assertEquals(mentioned(), expected);
+
+    // An edit that adds it notifies, the newcomer included.
+    m.send({ type: "chat_send", body: "soon" });
+    const draft = (await u.next("chat_message", byMod)).message;
+    m.send({ type: "chat_edit", id: draft.id, body: "now, @everyone" });
+    await u.next("chat_message_updated");
+    assertEquals(
+      count(
+        `SELECT COUNT(*) AS n FROM notifications WHERE data LIKE ?;`,
+        `%${draft.id}%`,
+      ),
+      3,
+    );
+    assertEquals(mentioned()[late.id], true);
+  },
+);
+
 wsTest("chat: typing and read markers", async (connect) => {
   const alice = await createUser();
   const bob = await createUser();