v3: the chat stops dropping things and holds up to long messages — a message sent while the socket was down vanished with the draft already cleared, and a rejected one fared no better since the client ignored any error that wasn't about a vote or a like. Sends now carry a nonce and sit dimmed in the list until their echo retires them; the server's refusal, an offline socket or ten seconds of silence turns one into a failed row with retry, edit and discard, and a failed row that turns up in the history after a reconnect is retired as having landed after all. Failed edits and deletes show in a bar above the composer. The live stream only goes to signed-in sockets, matching the history behind auth; sends, edits and deletes share a per-user token bucket (typing and read markers get their own, and are just dropped past it); and moderation re-reads the role from the database on every check rather than trusting the one a week-old socket captured. Unread now lives on the server as users.chat_read_at (migration 0014, existing users start caught up), so the count survives a reload and every tab and device clears together; opening onto unread history lands on a "new" divider rather than the bottom, and marks it read only once you've scrolled down to it. After a reconnect the chat re-reads everything from its oldest loaded message and takes that as the truth, edits and deletions included, or reloads the latest page if too much happened. History pages on (created_at, id) so a shared millisecond can't hide a message at a boundary. In the modal: a run of messages from one author shares a header with the time in the gutter on hover, mentions and replies to you get an accent edge, a pill counts what arrived while you were scrolled up, the draft survives closing and reloading, relative times tick, reply previews are flattened from markdown, owners can delete their own messages, ↑ in an empty composer edits your last one, and there's a proper loading and retry state instead of a flash of "No messages yet". Long messages: the composer and edit box grow only so far and then scroll, instead of squeezing the list away; the counter shows only near the limit and sits above the box, since .comment-reply-textarea's padding shorthand had quietly cancelled the room kept for it inside; TextEditor sizes itself before paint, so opening an edit animates to the right height instead of dipping and snapping; and the list follows the bottom through any change in its content's height while pinned there, so ending an edit returns you to the end. A mention notification opens the chat over the page you're on rather than the home page.

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

api/model/interfaces.ts

@@ -101,7 +101,8 @@ export type Role = "user" | "moderator" | "admin";
 export const ROLES: readonly Role[] = ["user", "moderator", "admin"];
 
 export function isRole(value: unknown): value is Role {
-  return typeof value === "string" && (ROLES as readonly string[]).includes(value);
+  return typeof value === "string" &&
+    (ROLES as readonly string[]).includes(value);
 }
 
 export interface User {
@@ -595,6 +596,9 @@ export interface ChatSendMessage {
   body: string;
   /** Id of the message being replied to, if this is a reply. */
   replyToId?: string;
+  /** Client-chosen id echoed on the broadcast (or on the error), so the
+   * sender can match the outcome to its pending message. */
+  nonce?: string;
 }
 
 // Sent while the user is composing (true) and when they stop (false). The
@@ -622,6 +626,12 @@ export interface ChatDeleteMessage {
   id: string;
 }
 
+// The user has seen the chat up to the message created at `at`.
+export interface ChatReadMessage {
+  type: "chat_read";
+  at: string;
+}
+
 export type ClientToServerMessage =
   | PingMessage
   | PongMessage
@@ -633,7 +643,8 @@ export type ClientToServerMessage =
   | ChatTypingMessage
   | ChatFocusMessage
   | ChatEditMessage
-  | ChatDeleteMessage;
+  | ChatDeleteMessage
+  | ChatReadMessage;
 
 // ── Server → Client ──────────────────────────────────────────────────────────
 
@@ -650,6 +661,10 @@ export interface WelcomeMessage {
   myVotes: string[];
   myCommentLikes: string[];
   unreadNotificationCount: number;
+  /** The user's chat read marker and the unread count behind it (signed-in
+   * users only). */
+  chatReadAt?: string;
+  unreadChatCount: number;
 }
 
 export interface PresenceUpdateMessage {
@@ -758,6 +773,10 @@ export interface ErrorMessage {
   dumpId?: string;
   commentId?: string;
   action?: "cast" | "remove";
+  /** Set when a chat action failed, so the client can surface it in the chat. */
+  scope?: "chat";
+  /** Echo of the failed chat_send's nonce. */
+  nonce?: string;
 }
 
 export interface ForceLogoutMessage {
@@ -767,6 +786,8 @@ export interface ForceLogoutMessage {
 export interface ChatMessageMessage {
   type: "chat_message";
   message: ChatMessage;
+  /** The sender's nonce, so its pending copy can be retired. */
+  nonce?: string;
 }
 
 export interface ChatMessageUpdatedMessage {
@@ -786,6 +807,13 @@ export interface ChatTypingUpdateMessage {
   users: OnlineUser[];
 }
 
+// The user's read marker moved (from any of their tabs or devices).
+export interface ChatReadUpdateMessage {
+  type: "chat_read_update";
+  readAt: string;
+  unread: number;
+}
+
 export type ServerToClientMessage =
   | PingMessage
   | WelcomeMessage
@@ -811,7 +839,8 @@ export type ServerToClientMessage =
   | ChatMessageMessage
   | ChatMessageUpdatedMessage
   | ChatMessageDeletedMessage
-  | ChatTypingUpdateMessage;
+  | ChatTypingUpdateMessage
+  | ChatReadUpdateMessage;
 
 /**
  * Follows