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/components/chat/ChatMessageItem.tsx

@@ -35,7 +35,10 @@ export interface ChatMessageItemProps {
    * float over its top.
    */
   grouped: boolean;
-  /** Highlights a message that @mentions the user or replies to them. */
+  /**
+   * Highlights a message that @mentions the user, `@everyone` included, or
+   * replies to them.
+   */
   mentionsMe: boolean;
   /**
    * Set when the replied-to message was deleted live, after the server filled
@@ -199,7 +202,10 @@ export function ChatMessageItem(
             />
           )
           : (
-            <Markdown className={messageTextClass(message.body)}>
+            <Markdown
+              className={messageTextClass(message.body)}
+              everyone={message.mentionsEveryone}
+            >
               {message.body}
             </Markdown>
           )}

src/components/chat/ChatModal.tsx

@@ -143,6 +143,7 @@ export function ChatModal(
   } = useWSChat();
   const { authFetch, user } = useAuth();
   const canModerate = can(user, "chat:moderate");
+  const canMentionEveryone = can(user, "chat:everyone");
   const userId = user?.id;
 
   const [history, setHistory] = useState<ChatMessage[]>([]);
@@ -701,7 +702,7 @@ export function ChatModal(
               message={m}
               grouped={row.grouped}
               mentionsMe={!isOwn && !!username &&
-                (mentionsUser(m.body, username) ||
+                (!!m.mentionsEveryone || mentionsUser(m.body, username) ||
                   m.replyToAuthor === username)}
               replyDeleted={!!m.replyToId && deletedIds.has(m.replyToId)}
               canEdit={isOwn || canModerate}
@@ -853,6 +854,7 @@ export function ChatModal(
             autoResize
             maxLength={VALIDATION.CHAT_MESSAGE_MAX}
             countFrom={COUNT_FROM}
+            mentionEveryone={canMentionEveryone}
             className="comment-reply-textarea chat-input"
             onSubmit={handleSend}
             onKeyDown={handleComposerKeyDown}

src/components/editor/Markdown.tsx

@@ -11,6 +11,7 @@ import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
 import { useAuth } from "../../hooks/auth/useAuth.ts";
 import { userPath } from "../../../shared/paths.ts";
+import { EVERYONE } from "../../../shared/mention.ts";
 
 /** Passed to {@link Markdown} by any component that shows a user's text. */
 export interface MarkdownProps {
@@ -21,6 +22,12 @@ export interface MarkdownProps {
    * would break the layout. The full text is one click away.
    */
   inline?: boolean;
+  /**
+   * Shows `@everyone` as a mention, from a chat message's
+   * `mentionsEveryone`. Without it, `@everyone` is plain text: anyone may type
+   * it, and it reaches no one.
+   */
+  everyone?: boolean;
 }
 
 /**
@@ -36,14 +43,18 @@ interface MdNode {
   value?: string;
   url?: string;
   children?: MdNode[];
+  /** Read by mdast-util-to-hast: the element and attributes to render. */
+  data?: { hName: string; hProperties: Record<string, string> };
 }
 
 /**
  * Turns a bare `@username` into a link to that user's profile. It works on the
  * parsed tree rather than the source, so code keeps its `@`s and a URL that
  * contains one (`https://mastodon.social/@bob`) isn't split in two.
+ * `@everyone` names no profile: it is left as text, or with `everyone` set,
+ * becomes a `span.md-everyone`.
  */
-function remarkMentions() {
+function remarkMentions({ everyone = false }: { everyone?: boolean } = {}) {
   const walk = (node: MdNode) => {
     if (!node.children) return;
     // Link text is already a link, whatever it says.
@@ -56,14 +67,27 @@ function remarkMentions() {
       const out: MdNode[] = [];
       let last = 0;
       for (const m of child.value.matchAll(MENTION_RE)) {
+        const isEveryone = m[1].toLowerCase() === EVERYONE;
+        if (isEveryone && !everyone) continue;
         if (m.index > last) {
           out.push({ type: "text", value: child.value.slice(last, m.index) });
         }
-        out.push({
-          type: "link",
-          url: userPath(m[1]),
-          children: [{ type: "text", value: m[0] }],
-        });
+        out.push(
+          isEveryone
+            ? {
+              type: "emphasis",
+              data: {
+                hName: "span",
+                hProperties: { className: "md-everyone" },
+              },
+              children: [{ type: "text", value: m[0] }],
+            }
+            : {
+              type: "link",
+              url: userPath(m[1]),
+              children: [{ type: "text", value: m[0] }],
+            },
+        );
         last = m.index + m[0].length;
       }
       if (last === 0) return [child];
@@ -101,6 +125,13 @@ function remarkBreaks() {
 
 const REMARK_PLUGINS = [remarkGfm, remarkMentions, remarkBreaks];
 
+/** {@link REMARK_PLUGINS} for a text whose `@everyone` is a mention. */
+const REMARK_PLUGINS_EVERYONE = [
+  remarkGfm,
+  [remarkMentions, { everyone: true }],
+  remarkBreaks,
+] as React.ComponentProps<typeof ReactMarkdown>["remarkPlugins"];
+
 /**
  * Returns the path of a link into this app, relative or absolute to this
  * origin, or null for anywhere else. The API's files and attachments count as
@@ -180,7 +211,7 @@ const INLINE_MARKDOWN_COMPONENTS: Components = {
 export const Markdown: React.MemoExoticComponent<
   (props: MarkdownProps) => React.JSX.Element
 > = memo(function Markdown(
-  { children, className, inline = false }: MarkdownProps,
+  { children, className, inline = false, everyone = false }: MarkdownProps,
 ) {
   return (
     <div
@@ -189,7 +220,7 @@ export const Markdown: React.MemoExoticComponent<
       }`}
     >
       <ReactMarkdown
-        remarkPlugins={REMARK_PLUGINS}
+        remarkPlugins={everyone ? REMARK_PLUGINS_EVERYONE : REMARK_PLUGINS}
         components={inline ? INLINE_MARKDOWN_COMPONENTS : MARKDOWN_COMPONENTS}
       >
         {children}

src/components/editor/MentionDropdown.tsx

@@ -8,6 +8,7 @@
 import { type CSSProperties, useLayoutEffect, useRef } from "react";
 import { Avatar } from "../shared/Avatar.tsx";
 import type { UserSuggestion } from "../../../shared/user.ts";
+import { EVERYONE } from "../../../shared/mention.ts";
 
 /**
  * Passed to {@link MentionDropdown} by `TextEditor`, from the state of
@@ -65,12 +66,20 @@ export function MentionDropdown(
             onSelect(user.username);
           }}
         >
-          <Avatar
-            userId={user.id}
-            username={user.username}
-            hasAvatar={!!user.avatarMime}
-            size={20}
-          />
+          {user.username === EVERYONE
+            ? (
+              <span className="mention-dropdown-everyone" aria-hidden="true">
+                📣
+              </span>
+            )
+            : (
+              <Avatar
+                userId={user.id}
+                username={user.username}
+                hasAvatar={!!user.avatarMime}
+                size={20}
+              />
+            )}
           <span className="mention-dropdown-username">@{user.username}</span>
         </li>
       ))}

src/components/editor/TextEditor.tsx

@@ -80,6 +80,11 @@ export interface TextEditorProps {
    * before the warning colour does.
    */
   countFrom?: number;
+  /**
+   * Offers `@everyone` among the mention suggestions. The chat's composer
+   * sets it for a role with `chat:everyone`, the one place it notifies.
+   */
+  mentionEveryone?: boolean;
   "aria-invalid"?: boolean;
   /** Joined with the id of the editor's own upload notice when it shows one. */
   "aria-describedby"?: string;
@@ -138,6 +143,7 @@ export const TextEditor: React.ForwardRefExoticComponent<
       onKeyDown,
       maxLength,
       countFrom,
+      mentionEveryone = false,
       "aria-invalid": ariaInvalid,
       "aria-describedby": ariaDescribedBy,
     },
@@ -224,7 +230,7 @@ export const TextEditor: React.ForwardRefExoticComponent<
       closeMention,
       handleMentionKeyDown,
       handleMentionSelect,
-    } = useMentionAutocomplete(replace);
+    } = useMentionAutocomplete(replace, mentionEveryone);
 
     const {
       emojiMode,