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>

src/hooks/editor/useMentionAutocomplete.ts

@@ -16,7 +16,7 @@ import {
 import { API_URL } from "../../config/api.ts";
 import { insideCode } from "../../utils/editor/text.ts";
 import type { UserSuggestion } from "../../../shared/user.ts";
-import { MENTION_RE } from "../../../shared/mention.ts";
+import { EVERYONE, MENTION_RE } from "../../../shared/mention.ts";
 
 interface MentionState {
   open: boolean;
@@ -37,6 +37,16 @@ const CLOSED: MentionState = {
   selectedIndex: 0,
 };
 
+/**
+ * Offered first, to those who may say it, when the query starts `everyone`.
+ * No user has the name, so `MentionDropdown` tells it apart by it.
+ */
+const EVERYONE_SUGGESTION: UserSuggestion = {
+  id: EVERYONE,
+  username: EVERYONE,
+  avatarMime: null,
+};
+
 /**
  * Matches the `@query` ending at the caret by the rule of shared/mention.ts,
  * which the server notifies by, so that what is offered would notify.
@@ -100,10 +110,12 @@ export interface UseMentionAutocompleteResult {
  * Returns the suggestions' state and the functions that drive them. A pick
  * goes through `replace`, `TextEditor`'s function that puts the text over
  * `[start, end)` of the textarea's value, followed by a space when `word` is
- * set.
+ * set. With `everyone`, which the chat's composer sets for a role with
+ * `chat:everyone`, `@everyone` is offered too.
  */
 export function useMentionAutocomplete(
   replace: (start: number, end: number, text: string, word: boolean) => void,
+  everyone = false,
 ): UseMentionAutocompleteResult {
   const [state, setStateRaw] = useState<MentionState>(CLOSED);
   // Mirrored synchronously, so that the key handler and a late response both
@@ -165,13 +177,15 @@ export function useMentionAutocomplete(
           const current = stateRef.current;
           // Only the search for what is typed now may open or close the list.
           if (current.query !== mention.query) return;
-          if (body.success && body.data.length > 0) {
-            setState({
-              ...current,
-              open: true,
-              results: body.data,
-              selectedIndex: 0,
-            });
+          const results: UserSuggestion[] = [
+            ...(everyone &&
+                EVERYONE.startsWith(mention.query.toLowerCase())
+              ? [EVERYONE_SUGGESTION]
+              : []),
+            ...(body.success ? body.data : []),
+          ];
+          if (results.length > 0) {
+            setState({ ...current, open: true, results, selectedIndex: 0 });
           } else {
             setState({ ...current, open: false, results: [] });
           }
@@ -180,7 +194,7 @@ export function useMentionAutocomplete(
         }
       }, 150);
     },
-    [cancelLookup, close, setState],
+    [cancelLookup, close, everyone, setState],
   );
 
   const select = useCallback(