feat(channels): ship M4 per-thread unread with thread receipts mute-aware atom and architectural cleanup

public/locales/en.json

@@ -520,6 +520,10 @@
     "thread_summary_count_other": "{{count}} replies",
     "thread_summary_open_thread": "Open thread",
     "thread_summary_last_reply_by": "last reply from {{name}}",
+    "thread_summary_unread_one": "{{count}} unread",
+    "thread_summary_unread_other": "{{count}} unread",
+    "thread_summary_highlight_one": "{{count}} mention",
+    "thread_summary_highlight_other": "{{count}} mentions",
     "no_post_permission": "You do not have permission to post in this room",
 
     "conversation_beginning": "This is the beginning of conversation.",

public/locales/ru.json

@@ -526,6 +526,14 @@
     "thread_summary_count_other": "{{count}} ответа",
     "thread_summary_open_thread": "Открыть тред",
     "thread_summary_last_reply_by": "последний ответ от {{name}}",
+    "thread_summary_unread_one": "{{count}} непрочитанное",
+    "thread_summary_unread_few": "{{count}} непрочитанных",
+    "thread_summary_unread_many": "{{count}} непрочитанных",
+    "thread_summary_unread_other": "{{count}} непрочитанных",
+    "thread_summary_highlight_one": "{{count}} упоминание",
+    "thread_summary_highlight_few": "{{count}} упоминания",
+    "thread_summary_highlight_many": "{{count}} упоминаний",
+    "thread_summary_highlight_other": "{{count}} упоминания",
     "no_post_permission": "У вас нет разрешения на отправку сообщений в этой комнате",
 
     "conversation_beginning": "Начало переписки.",

src/app/features/room/Room.tsx

@@ -25,6 +25,7 @@ import { useChannelsMode, ThreadDrawerOpenProvider } from '../../hooks/useChanne
 import { CHANNELS_THREAD_PATH } from '../../pages/paths';
 import { getChannelsRoomPath } from '../../pages/pathUtils';
 import { isBridgedRoom } from '../../utils/room';
+import { useUnreadThreadingEnabled } from '../../hooks/useClientConfig';
 
 type RoomProps = {
   renderRoomView?: (props: { eventId?: string }) => React.ReactNode;
@@ -88,22 +89,29 @@ export function Room({ renderRoomView }: RoomProps) {
   // changes (provider is reactive via `useIsOneOnOneRoom` upstream).
   const isOneOnOne = useIsOneOnOne();
 
+  const unreadThreadingEnabled = useUnreadThreadingEnabled();
+
   useKeyDown(
     window,
     useCallback(
       (evt) => {
-        // Skip Escape-markAsRead when the thread drawer is open. The
-        // existing handler in `state/room/roomToUnread.ts` blind-deletes
-        // ALL room unread on any own receipt — so firing markAsRead
-        // here while the drawer is the active surface would also wipe
-        // unrelated channel-main unread that the user hasn't seen.
-        // M4 will refactor the receipt handler to partition by
-        // thread_id; until then, gate the Escape shortcut.
-        if (isKeyHotkey('escape', evt) && !showThreadDrawer) {
+        // Escape marks the room as read. Pre-M4 the receipt handler
+        // blind-deleted ALL room unread on any own receipt, so the
+        // drawer-open case had to be skipped to avoid wiping thread
+        // unread the user hadn't seen. After the M4 receipt-handler
+        // refactor (PUT-with-fresh, partitioned by thread_id) main and
+        // thread unread are independent, so Escape on the channel main
+        // surface marks main as read and leaves threads alone — works
+        // unconditionally. Under the kill switch the handler reverts
+        // to blind DELETE, so we keep the drawer-open guard there.
+        if (
+          isKeyHotkey('escape', evt) &&
+          (unreadThreadingEnabled || !showThreadDrawer)
+        ) {
           markAsRead(mx, room.roomId, hideActivity);
         }
       },
-      [mx, room.roomId, hideActivity, showThreadDrawer]
+      [mx, room.roomId, hideActivity, showThreadDrawer, unreadThreadingEnabled]
     )
   );
 

src/app/features/room/RoomInput.tsx

@@ -186,7 +186,11 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
     const [autocompleteQuery, setAutocompleteQuery] =
       useState<AutocompleteQuery<AutocompletePrefix>>();
 
-    const sendTypingStatus = useTypingStatusUpdater(mx, roomId);
+    // Suppress typing notifications from the drawer composer — see
+    // useTypingStatusUpdater for the spec-level reason (m.typing has
+    // no thread_id, so a thread-composer typing event would surface
+    // in the main channel chat as if the user were typing there).
+    const sendTypingStatus = useTypingStatusUpdater(mx, roomId, !!threadId);
 
     const handleFiles = useCallback(
       async (files: File[]) => {

src/app/features/room/RoomTimeline.tsx

@@ -751,7 +751,16 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
           }
 
           scrollToBottomRef.current.count += 1;
-          scrollToBottomRef.current.smooth = mEvt.getSender() !== mx.getUserId();
+          // Always instant — never smooth on incoming. Smooth animation
+          // briefly takes the at-bottom anchor out of the
+          // IntersectionObserver's intersection box during the
+          // animation frame, which the 1s debounce sometimes turns
+          // into a false-positive «user scrolled away» → atBottom flips
+          // false → next message stops auto-following. Direct snap
+          // matches Discord / Telegram and the drawer (M4 fix in
+          // ThreadDrawer.tsx) — predictable, no animation surface for
+          // the observer to misinterpret.
+          scrollToBottomRef.current.smooth = false;
           if (isOwnLiveStreamMessage) {
             setAtBottom(true);
             if (!atLiveEndRef.current) {
@@ -904,7 +913,13 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
     useCallback(
       () => ({
         root: getScrollElement(),
-        rootMargin: '100px',
+        // Forgiving threshold: 100px was too tight — single tall
+        // message + minor touch-scroll inertia easily took users out
+        // of «at-bottom» state, after which incoming events stopped
+        // auto-following. 400px gives roughly two-three Stream rows
+        // of slack before treating the scroll as a deliberate detach,
+        // matching Discord / Slack auto-follow generosity.
+        rootMargin: '400px',
       }),
       [getScrollElement]
     ),

src/app/features/room/ThreadDrawer.tsx

@@ -32,6 +32,10 @@ import { Opts as LinkifyOpts } from 'linkifyjs';
 import * as css from './ThreadDrawer.css';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { useMediaAuthentication } from '../../hooks/useMediaAuthentication';
+import { useResizeObserver } from '../../hooks/useResizeObserver';
+import { scrollToBottom } from '../../utils/dom';
+import { useUnreadThreadingEnabled } from '../../hooks/useClientConfig';
+import { markAsThreadRead } from '../../utils/notifications';
 import { useEditor } from '../../components/editor';
 import {
   getEditedEvent,
@@ -231,8 +235,11 @@ export function ThreadDrawer({
   const [mediaAutoLoad] = useSetting(settingsAtom, 'mediaAutoLoad');
   const [urlPreview] = useSetting(settingsAtom, 'urlPreview');
   const [encUrlPreview] = useSetting(settingsAtom, 'encUrlPreview');
+  const [hideActivity] = useSetting(settingsAtom, 'hideActivity');
   const showUrlPreview = room.hasEncryptionStateEvent() ? encUrlPreview : urlPreview;
 
+  const unreadThreadingEnabled = useUnreadThreadingEnabled();
+
   const mentionClickHandler = useMentionClickHandler(room.roomId);
   const spoilerClickHandler = useSpoilerClickHandler();
 
@@ -610,14 +617,15 @@ export function ThreadDrawer({
       })
     : [];
 
-  // Read receipts intentionally NOT fired here in M2. With
-  // threadSupport: true the SDK auto-attaches `thread_id: rootId` to
-  // any sendReadReceipt call from a thread event, but the existing
-  // receipt handler in `state/room/roomToUnread.ts` does a blind
-  // DELETE on any own receipt — so a thread read would wipe the
-  // whole channel's unread badge including main-timeline messages
-  // the user has not seen. M4 will refactor the handler to partition
-  // by thread_id; until then the drawer leaves unread state alone.
+  // Read receipts (M4): fired on first reveal at-bottom, on reply
+  // growth while at-bottom, and on own send via the layout/effect
+  // pair below. The receipt handler in `state/room/roomToUnread.ts`
+  // partitions by thread_id (PUT-with-fresh instead of blind DELETE)
+  // so a thread receipt no longer wipes main-timeline unread. SDK
+  // auto-attaches `thread_id: rootId` via `threadIdForReceipt(event)`.
+  // Gated on `unreadThreadingEnabled` so the kill switch falls back
+  // to pre-M4 silence (no thread receipts → channel-list badge
+  // semantics match the pre-M4 blind-DELETE handler).
 
   // Track whether the user is parked at the bottom of the replies
   // list via IntersectionObserver on the sentinel. Element-web's
@@ -670,6 +678,23 @@ export function ThreadDrawer({
   const repliesCount = replies.length;
   const lastReplyCountRef = useRef(0);
   const myUserId = mx.getUserId();
+
+  // Fire a thread-scoped read receipt when the user lands at-bottom on
+  // a thread with replies. SDK auto-routes `thread_id: rootId` via
+  // `threadIdForReceipt(event)` (client.js:2655). Skipped when the
+  // kill switch (`channels.unreadThreading: false`) is set — the
+  // receipt handler in roomToUnread.ts then runs in pre-M4
+  // blind-DELETE mode, so a thread receipt would wipe channel-main
+  // unread (the M2 reason this was deferred). Also skipped when the
+  // tab is backgrounded, mirroring RoomTimeline's `document.hasFocus`
+  // gate so push notifications keep firing for unfocused tabs.
+  const tryMarkThreadRead = useCallback(() => {
+    if (!unreadThreadingEnabled) return;
+    if (!thread) return;
+    if (!document.hasFocus()) return;
+    markAsThreadRead(mx, thread, hideActivity);
+  }, [mx, thread, hideActivity, unreadThreadingEnabled]);
+
   useLayoutEffect(() => {
     const host = scrollHostRef.current;
     if (!host) return;
@@ -678,7 +703,8 @@ export function ThreadDrawer({
     host.scrollTop = host.scrollHeight;
     isAtBottomRef.current = true;
     lastReplyCountRef.current = repliesCount;
-  }, [repliesCount]);
+    tryMarkThreadRead();
+  }, [repliesCount, tryMarkThreadRead]);
 
   useEffect(() => {
     const host = scrollHostRef.current;
@@ -696,25 +722,49 @@ export function ThreadDrawer({
       // new arrival from someone else.
       return;
     }
-    if (lastIsOwn) {
-      // Own send: jump to bottom instantly — the user just hit Enter,
-      // a smooth scroll animation feels like the input «kicks back»
-      // before settling. Slack/iMessage do the same. Direct scrollTop
-      // write is synchronous; no animation.
-      host.scrollTop = host.scrollHeight;
-    } else {
-      // Reply from someone else while at-bottom: smooth scroll keeps
-      // a visual cue («new reply landed»).
-      bottomSentinelRef.current.scrollIntoView({
-        behavior: 'smooth',
-        block: 'end',
-      });
-    }
+    // Always instant — never smooth. Cold-load arrives in 1-2 waves
+    // (SDK cache + mx.relations resolve), so the first growth pass
+    // after initial reveal would otherwise smooth-scroll a few rows
+    // and leak a visible animation on drawer-open. Even for
+    // steady-state live replies a snap-to-bottom matches Discord /
+    // Telegram and beats the «kicks back before settling» feel of a
+    // smooth scrollIntoView. Direct scrollTop write is synchronous —
+    // browser repaints with the new position in the same frame.
+    host.scrollTop = host.scrollHeight;
     isAtBottomRef.current = true;
+    tryMarkThreadRead();
     // Intentional: replies array read inside is stable identity-wise
     // because computed inline; lint disable for the false-positive.
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [repliesCount, myUserId]);
+  }, [repliesCount, myUserId, tryMarkThreadRead]);
+
+  // Stay at-bottom when the drawer scroll container resizes — Android
+  // soft-keyboard open/close shrinks the viewport, and Capacitor's
+  // default `windowSoftInputMode=adjustResize` shrinks the WebView
+  // so our scroll host's clientHeight changes. Without this, the
+  // composer pushes up to roughly mid-replies because `scrollHeight`
+  // grows past the new shrunk viewport while `scrollTop` stays put.
+  // Mirrors the keyboard-open fix in `RoomTimeline.tsx::useResizeObserver`
+  // (line 858+). Skip the first observer callback (initial mount fires
+  // synthetic resize) so we don't fight the first-reveal layout-effect.
+  useResizeObserver(
+    useMemo(() => {
+      let mounted = false;
+      return (_entries: ResizeObserverEntry[]) => {
+        if (!mounted) {
+          mounted = true;
+          return;
+        }
+        if (isAtBottomRef.current) {
+          requestAnimationFrame(() => {
+            const el = scrollHostRef.current;
+            if (el) scrollToBottom(el);
+          });
+        }
+      };
+    }, []),
+    useCallback(() => scrollHostRef.current, [])
+  );
 
   // Autofocus: drop focus on the close button ONCE per drawer
   // lifetime so screen-reader / keyboard users land somewhere

src/app/features/room/ThreadSummaryCard.css.ts

@@ -39,14 +39,32 @@ export const Root = style({
   },
 });
 
-// 6px dot indicator. Filled `Primary.Main` — on M4 will flip to
-// `OnContainerLine` for read threads, kept static on M3.
+// 6px dot indicator. Visible ONLY when the thread has unread content
+// (M4): `unread` → `Primary.Main` (lavender, total > 0); `highlight`
+// → `Critical.Main` (mention). On `read` state the dot is hidden
+// outright via `display: none` — a dim-coloured dot against the pill
+// bg (`SurfaceVariant.ContainerHover`) rendered at ~1.28:1 contrast,
+// effectively invisible on dim screens, so the user couldn't tell
+// «read» apart from «no indicator». Hiding makes the absence
+// load-bearing: dot present → unread, dot absent → read. Under the
+// kill switch the parent always passes `read`; the card collapses to
+// a clean count + time + chevron pill.
 export const Dot = style({
   flexShrink: 0,
   width: toRem(6),
   height: toRem(6),
   borderRadius: '50%',
-  backgroundColor: color.Primary.Main,
+  display: 'none',
+  selectors: {
+    '&[data-unread-state="unread"]': {
+      display: 'block',
+      backgroundColor: color.Primary.Main,
+    },
+    '&[data-unread-state="highlight"]': {
+      display: 'block',
+      backgroundColor: color.Critical.Main,
+    },
+  },
 });
 
 export const Count = style({

src/app/features/room/ThreadSummaryCard.tsx

@@ -6,8 +6,10 @@ import { Icon, Icons, Text, as } from 'folds';
 import {
   type IThreadBundledRelationship,
   type MatrixEvent,
+  NotificationCountType,
   RelationType,
   type Room,
+  RoomEvent,
   type Thread,
   ThreadEvent,
 } from 'matrix-js-sdk';
@@ -17,6 +19,7 @@ import { Time } from '../../components/message';
 import { getChannelsThreadPath } from '../../pages/pathUtils';
 import { getMemberDisplayName } from '../../utils/room';
 import { getMxIdLocalPart } from '../../utils/matrix';
+import { useUnreadThreadingEnabled } from '../../hooks/useClientConfig';
 
 export type ThreadSummaryCardProps = {
   room: Room;
@@ -94,6 +97,33 @@ export const ThreadSummaryCard = as<'button', ThreadSummaryCardProps>(
       };
     }, [thread]);
 
+    // Per-thread unread refresh (M4). `RoomEvent.UnreadNotifications`
+    // fires from three SDK call sites (matrix-js-sdk room.js:1354/1398
+    // /1426): per-thread set (with threadId), per-thread reset from
+    // /sync (NO threadId, room.js:1398), and main-timeline set (no
+    // threadId, room.js:1426). Accept `firedThreadId === rootId` AND
+    // the no-threadId reset/main-timeline cases so a /sync that zeros
+    // all thread counts in one shot still ticks our card. The cost of
+    // a no-op tick on unrelated main-timeline updates is negligible
+    // because we only read a couple of cheap counters. Skipped under
+    // the kill switch — pre-M4 cards don't surface unread state.
+    const unreadThreadingEnabled = useUnreadThreadingEnabled();
+    useEffect(() => {
+      if (!unreadThreadingEnabled || !rootId) return undefined;
+      const handle = (
+        _count: unknown,
+        firedThreadId: string | undefined
+      ) => {
+        if (firedThreadId === undefined || firedThreadId === rootId) {
+          setVersion((v) => v + 1);
+        }
+      };
+      room.on(RoomEvent.UnreadNotifications, handle);
+      return () => {
+        room.off(RoomEvent.UnreadNotifications, handle);
+      };
+    }, [room, rootId, unreadThreadingEnabled]);
+
     const bundled = rootId
       ? rootEvent.getServerAggregatedRelation<IThreadBundledRelationship>(RelationType.Thread)
       : undefined;
@@ -123,8 +153,32 @@ export const ThreadSummaryCard = as<'button', ThreadSummaryCardProps>(
       ? getMemberDisplayName(room, senderId) ?? getMxIdLocalPart(senderId) ?? senderId
       : null;
 
+    // Per-thread unread state. Server-derived totals via SDK; only
+    // consulted when the kill switch is on, so disabled-config or
+    // MSC3773-less servers fall through to the static «read» dot.
+    const unreadTotal = unreadThreadingEnabled
+      ? room.getThreadUnreadNotificationCount(rootId, NotificationCountType.Total)
+      : 0;
+    const unreadHighlight = unreadThreadingEnabled
+      ? room.getThreadUnreadNotificationCount(rootId, NotificationCountType.Highlight)
+      : 0;
+    let dotState: 'read' | 'unread' | 'highlight' = 'read';
+    if (unreadHighlight > 0) dotState = 'highlight';
+    else if (unreadTotal > 0) dotState = 'unread';
+
     const countLabel = t('Room.thread_summary_count', { count });
     const ariaParts = [t('Room.thread_summary_open_thread'), countLabel];
+    if (unreadThreadingEnabled) {
+      // Highlight (mention) is a strict superset of unread for screen
+      // readers: prefer the mention phrasing when applicable so SR
+      // users get parity with sighted users (red dot vs lavender dot).
+      // Fall back to plain unread phrasing if total > 0 but no mention.
+      if (unreadHighlight > 0) {
+        ariaParts.push(t('Room.thread_summary_highlight', { count: unreadHighlight }));
+      } else if (unreadTotal > 0) {
+        ariaParts.push(t('Room.thread_summary_unread', { count: unreadTotal }));
+      }
+    }
     if (senderDisplayName) {
       ariaParts.push(t('Room.thread_summary_last_reply_by', { name: senderDisplayName }));
     }
@@ -143,9 +197,10 @@ export const ThreadSummaryCard = as<'button', ThreadSummaryCardProps>(
         onClick={handleOpen}
         aria-label={ariaLabel}
         data-event-id={rootId}
+        data-unread-state={dotState}
         {...props}
       >
-        <span className={css.Dot} aria-hidden />
+        <span className={css.Dot} data-unread-state={dotState} aria-hidden />
         <Text className={css.Count} as="span" size="T200">
           <b>{countLabel}</b>
         </Text>

src/app/hooks/useClientConfig.ts

@@ -26,6 +26,15 @@ export type BotConfig = {
   };
 };
 
+export type ChannelsConfig = {
+  /** Default true. When false, M4 per-thread unread machinery (badges,
+   * thread-aware receipt handler, drawer markAsRead) falls back to
+   * pre-M4 blind-DELETE semantics. `threadSupport: true` stays on
+   * unconditionally — drawer (M2) reads `room.getThread()` and
+   * ThreadEvent emitters which silently NO-OP without it. */
+  unreadThreading?: boolean;
+};
+
 export type ClientConfig = {
   defaultHomeserver?: number;
   homeserverList?: string[];
@@ -43,8 +52,13 @@ export type ClientConfig = {
   push?: PushConfig;
 
   bots?: BotConfig[];
+
+  channels?: ChannelsConfig;
 };
 
+export const isUnreadThreadingEnabled = (clientConfig: ClientConfig): boolean =>
+  clientConfig.channels?.unreadThreading !== false;
+
 const ClientConfigContext = createContext<ClientConfig | null>(null);
 
 export const ClientConfigProvider = ClientConfigContext.Provider;
@@ -55,6 +69,15 @@ export function useClientConfig(): ClientConfig {
   return config;
 }
 
+// Single source of truth for the M4 kill switch. Default true (absent
+// config = enabled). Consumers should call this hook instead of reading
+// `useClientConfig()` + `isUnreadThreadingEnabled(...)` separately —
+// keeps the predicate in one place and lets future telemetry / runtime
+// flips slot in transparently.
+export function useUnreadThreadingEnabled(): boolean {
+  return isUnreadThreadingEnabled(useClientConfig());
+}
+
 export const clientDefaultServer = (clientConfig: ClientConfig): string =>
   clientConfig.homeserverList?.[clientConfig.defaultHomeserver ?? 0] ?? 'matrix.org';
 

src/app/hooks/useTypingStatusUpdater.ts

@@ -4,11 +4,29 @@ import { TYPING_TIMEOUT_MS } from '../state/typingMembers';
 
 type TypingStatusUpdater = (typing: boolean) => void;
 
-export const useTypingStatusUpdater = (mx: MatrixClient, roomId: string): TypingStatusUpdater => {
+// `disabled` is the caller's opt-out for surfaces where typing
+// notifications would leak to the wrong audience. The Matrix
+// `m.typing` EDU is strictly room-scoped (the spec has no `thread_id`
+// field), so a thread composer that called `mx.sendTyping(roomId, ...)`
+// would broadcast «X is typing» to every member watching the main
+// channel chat — even though the user is privately drafting in a
+// thread drawer. The drawer passes `disabled=true` to keep the
+// indicator absent rather than misleading. Returns a stable noop
+// when disabled so call sites keep their stable identity.
+export const useTypingStatusUpdater = (
+  mx: MatrixClient,
+  roomId: string,
+  disabled = false
+): TypingStatusUpdater => {
   const statusSentTsRef = useRef<number>(0);
 
   const sendTypingStatus: TypingStatusUpdater = useMemo(() => {
     statusSentTsRef.current = 0;
+    if (disabled) {
+      return () => {
+        /* noop: typing leaks across thread/main boundary by spec */
+      };
+    }
     return (typing) => {
       if (typing) {
         if (Date.now() - statusSentTsRef.current < TYPING_TIMEOUT_MS) {
@@ -35,7 +53,7 @@ export const useTypingStatusUpdater = (mx: MatrixClient, roomId: string): Typing
       }
       statusSentTsRef.current = 0;
     };
-  }, [mx, roomId]);
+  }, [mx, roomId, disabled]);
 
   return sendTypingStatus;
 };

src/app/state/hooks/useBindAtoms.ts

@@ -2,18 +2,22 @@ import { MatrixClient } from 'matrix-js-sdk';
 import { allInvitesAtom, useBindAllInvitesAtom } from '../room-list/inviteList';
 import { allRoomsAtom, useBindAllRoomsAtom } from '../room-list/roomList';
 import { mDirectAtom, useBindMDirectAtom } from '../mDirectList';
-import { roomToUnreadAtom, useBindRoomToUnreadAtom } from '../room/roomToUnread';
+import { roomToUnreadAtom } from '../room/roomToUnread';
+import { useBindRoomToUnreadAtom } from '../room/useBindRoomToUnreadAtom';
 import { roomToParentsAtom, useBindRoomToParentsAtom } from '../room/roomToParents';
 import { roomIdToTypingMembersAtom, useBindRoomIdToTypingMembersAtom } from '../typingMembers';
 import { useAutoDirectSync } from '../../hooks/useAutoDirectSync';
+import { useUnreadThreadingEnabled } from '../../hooks/useClientConfig';
 
 export const useBindAtoms = (mx: MatrixClient) => {
+  const unreadThreadingEnabled = useUnreadThreadingEnabled();
+
   useBindMDirectAtom(mx, mDirectAtom);
   useAutoDirectSync(mx);
   useBindAllInvitesAtom(mx, allInvitesAtom);
   useBindAllRoomsAtom(mx, allRoomsAtom);
   useBindRoomToParentsAtom(mx, roomToParentsAtom);
-  useBindRoomToUnreadAtom(mx, roomToUnreadAtom);
+  useBindRoomToUnreadAtom(mx, roomToUnreadAtom, unreadThreadingEnabled);
 
   useBindRoomIdToTypingMembersAtom(mx, roomIdToTypingMembersAtom);
 };

src/app/state/room/roomToUnread.ts

@@ -1,34 +1,14 @@
 import produce from 'immer';
-import { atom, useSetAtom } from 'jotai';
-import {
-  IRoomTimelineData,
-  MatrixClient,
-  MatrixEvent,
-  Room,
-  RoomEvent,
-  SyncState,
-} from 'matrix-js-sdk';
-import { ReceiptContent, ReceiptType } from 'matrix-js-sdk/lib/@types/read_receipts';
-import { useCallback, useEffect } from 'react';
-import {
-  Membership,
-  NotificationType,
-  RoomToUnread,
-  UnreadInfo,
-  Unread,
-  StateEvent,
-} from '../../../types/matrix/room';
-import {
-  getAllParents,
-  getNotificationType,
-  getUnreadInfo,
-  getUnreadInfos,
-  isNotificationEvent,
-} from '../../utils/room';
+import { atom } from 'jotai';
+import { RoomToUnread, UnreadInfo, Unread } from '../../../types/matrix/room';
+import { getAllParents } from '../../utils/room';
 import { roomToParentsAtom } from './roomToParents';
-import { useStateEventCallback } from '../../hooks/useStateEventCallback';
-import { useSyncState } from '../../hooks/useSyncState';
-import { useRoomsNotificationPreferencesContext } from '../../hooks/useRoomsNotificationPreferences';
+
+// Pure reducer + helpers for the room → unread aggregate. The listener
+// wiring that drives this atom lives next door in
+// `useBindRoomToUnreadAtom.ts` — keeping the data shape file free of
+// MatrixClient / React lets the reducer stay testable in isolation
+// and shrinks the surface area each module is responsible for.
 
 export type RoomToUnreadAction =
   | {
@@ -165,118 +145,3 @@ export const roomToUnreadAtom = atom<RoomToUnread, [RoomToUnreadAction], undefin
     }
   }
 );
-
-export const useBindRoomToUnreadAtom = (mx: MatrixClient, unreadAtom: typeof roomToUnreadAtom) => {
-  const setUnreadAtom = useSetAtom(unreadAtom);
-  const roomsNotificationPreferences = useRoomsNotificationPreferencesContext();
-
-  useEffect(() => {
-    setUnreadAtom({
-      type: 'RESET',
-      unreadInfos: getUnreadInfos(mx),
-    });
-  }, [mx, setUnreadAtom]);
-
-  useSyncState(
-    mx,
-    useCallback(
-      (state, prevState) => {
-        if (
-          (state === SyncState.Prepared && prevState === null) ||
-          (state === SyncState.Syncing && prevState !== SyncState.Syncing)
-        ) {
-          setUnreadAtom({
-            type: 'RESET',
-            unreadInfos: getUnreadInfos(mx),
-          });
-        }
-      },
-      [mx, setUnreadAtom]
-    )
-  );
-
-  useEffect(() => {
-    const handleTimelineEvent = (
-      mEvent: MatrixEvent,
-      room: Room | undefined,
-      toStartOfTimeline: boolean | undefined,
-      removed: boolean,
-      data: IRoomTimelineData
-    ) => {
-      if (!room || !data.liveEvent || room.isSpaceRoom() || !isNotificationEvent(mEvent)) return;
-      if (getNotificationType(mx, room.roomId) === NotificationType.Mute) {
-        setUnreadAtom({
-          type: 'DELETE',
-          roomId: room.roomId,
-        });
-        return;
-      }
-
-      if (mEvent.getSender() === mx.getUserId()) return;
-      setUnreadAtom({ type: 'PUT', unreadInfo: getUnreadInfo(room) });
-    };
-    mx.on(RoomEvent.Timeline, handleTimelineEvent);
-    return () => {
-      mx.removeListener(RoomEvent.Timeline, handleTimelineEvent);
-    };
-  }, [mx, setUnreadAtom]);
-
-  useEffect(() => {
-    const handleReceipt = (mEvent: MatrixEvent, room: Room) => {
-      const myUserId = mx.getUserId();
-      if (!myUserId) return;
-      if (room.isSpaceRoom()) return;
-      const content = mEvent.getContent<ReceiptContent>();
-
-      const isMyReceipt = Object.keys(content).find((eventId) =>
-        (Object.keys(content[eventId]) as ReceiptType[]).find(
-          (receiptType) => content[eventId][receiptType][myUserId]
-        )
-      );
-      if (isMyReceipt) {
-        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
-      }
-    };
-    mx.on(RoomEvent.Receipt, handleReceipt);
-    return () => {
-      mx.removeListener(RoomEvent.Receipt, handleReceipt);
-    };
-  }, [mx, setUnreadAtom]);
-
-  useEffect(() => {
-    setUnreadAtom({
-      type: 'RESET',
-      unreadInfos: getUnreadInfos(mx),
-    });
-  }, [mx, setUnreadAtom, roomsNotificationPreferences]);
-
-  useEffect(() => {
-    const handleMembershipChange = (room: Room, membership: string) => {
-      if (membership !== Membership.Join) {
-        setUnreadAtom({
-          type: 'DELETE',
-          roomId: room.roomId,
-        });
-      }
-    };
-    mx.on(RoomEvent.MyMembership, handleMembershipChange);
-    return () => {
-      mx.removeListener(RoomEvent.MyMembership, handleMembershipChange);
-    };
-  }, [mx, setUnreadAtom]);
-
-  useStateEventCallback(
-    mx,
-    useCallback(
-      (mEvent) => {
-        if (mEvent.getType() === StateEvent.SpaceChild) {
-          setUnreadAtom({
-            type: 'RESET',
-            unreadInfos: getUnreadInfos(mx),
-          });
-        }
-      },
-      [mx, setUnreadAtom]
-    )
-  );
-};

src/app/state/room/useBindRoomToUnreadAtom.ts

@@ -0,0 +1,260 @@
+import { useCallback, useEffect } from 'react';
+import { useSetAtom } from 'jotai';
+import {
+  ClientEvent,
+  IRoomTimelineData,
+  MatrixClient,
+  MatrixEvent,
+  Room,
+  RoomEvent,
+  SyncState,
+} from 'matrix-js-sdk';
+import { ReceiptContent, ReceiptType } from 'matrix-js-sdk/lib/@types/read_receipts';
+import { Membership, NotificationType, StateEvent } from '../../../types/matrix/room';
+import {
+  getNotificationType,
+  getUnreadInfo,
+  getUnreadInfos,
+  isNotificationEvent,
+} from '../../utils/room';
+import { roomToUnreadAtom } from './roomToUnread';
+import { useStateEventCallback } from '../../hooks/useStateEventCallback';
+import { useSyncState } from '../../hooks/useSyncState';
+import { useRoomsNotificationPreferencesContext } from '../../hooks/useRoomsNotificationPreferences';
+
+// Wires the SDK signals (Timeline, Receipt, UnreadNotifications,
+// MyMembership, sync state, space-child) into `roomToUnreadAtom`.
+// Split from the atom file so the reducer + atom shape stay free of
+// MatrixClient / React imports — see `roomToUnread.ts` for the data
+// layer.
+export const useBindRoomToUnreadAtom = (
+  mx: MatrixClient,
+  unreadAtom: typeof roomToUnreadAtom,
+  unreadThreadingEnabled: boolean
+) => {
+  const setUnreadAtom = useSetAtom(unreadAtom);
+  const roomsNotificationPreferences = useRoomsNotificationPreferencesContext();
+
+  useEffect(() => {
+    setUnreadAtom({
+      type: 'RESET',
+      unreadInfos: getUnreadInfos(mx),
+    });
+  }, [mx, setUnreadAtom]);
+
+  useSyncState(
+    mx,
+    useCallback(
+      (state, prevState) => {
+        if (
+          (state === SyncState.Prepared && prevState === null) ||
+          (state === SyncState.Syncing && prevState !== SyncState.Syncing)
+        ) {
+          setUnreadAtom({
+            type: 'RESET',
+            unreadInfos: getUnreadInfos(mx),
+          });
+        }
+      },
+      [mx, setUnreadAtom]
+    )
+  );
+
+  useEffect(() => {
+    const handleTimelineEvent = (
+      mEvent: MatrixEvent,
+      room: Room | undefined,
+      toStartOfTimeline: boolean | undefined,
+      removed: boolean,
+      data: IRoomTimelineData
+    ) => {
+      if (!room || !data.liveEvent || room.isSpaceRoom() || !isNotificationEvent(mEvent)) return;
+      if (getNotificationType(mx, room.roomId) === NotificationType.Mute) {
+        setUnreadAtom({
+          type: 'DELETE',
+          roomId: room.roomId,
+        });
+        return;
+      }
+
+      if (mEvent.getSender() === mx.getUserId()) return;
+      setUnreadAtom({ type: 'PUT', unreadInfo: getUnreadInfo(room) });
+    };
+    mx.on(RoomEvent.Timeline, handleTimelineEvent);
+    return () => {
+      mx.removeListener(RoomEvent.Timeline, handleTimelineEvent);
+    };
+  }, [mx, setUnreadAtom]);
+
+  useEffect(() => {
+    const handleReceipt = (mEvent: MatrixEvent, room: Room) => {
+      const myUserId = mx.getUserId();
+      if (!myUserId) return;
+      if (room.isSpaceRoom()) return;
+      const content = mEvent.getContent<ReceiptContent>();
+
+      const isMyReceipt = Object.keys(content).find((eventId) =>
+        (Object.keys(content[eventId]) as ReceiptType[]).find(
+          (receiptType) => content[eventId][receiptType][myUserId]
+        )
+      );
+      if (!isMyReceipt) return;
+
+      // Pre-M4 fallback: blind DELETE wipes the whole room's unread on
+      // any own receipt. Acceptable when threading is disabled because
+      // there are no per-thread receipts to honour separately.
+      if (!unreadThreadingEnabled) {
+        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
+        return;
+      }
+
+      // Mute gate — pre-M4 the blind-DELETE path implicitly respected
+      // mute (DELETE is a no-op for muted rooms which were never in the
+      // atom). PUT-with-fresh would re-introduce a muted room into the
+      // unread index whenever its `getUnreadInfo` returned non-zero
+      // (e.g. server-side counters for a muted room still tick on
+      // pings). Mirrors the mute branch in the Timeline + UnreadNotifications
+      // handlers above/below.
+      if (getNotificationType(mx, room.roomId) === NotificationType.Mute) {
+        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
+        return;
+      }
+
+      // With per-thread unread on, an own receipt no longer implies the
+      // user read every thread in the room — SDK already partitioned
+      // counters by thread_id before firing this event, so trust it.
+      // `getUnreadInfo` reads `room.getUnreadNotificationCount(Total)`
+      // which sums main + all threads. If the receipt was for the main
+      // timeline, threaded counts stay; if for a thread, the rest stays.
+      const fresh = getUnreadInfo(room);
+      if (fresh.total === 0 && fresh.highlight === 0) {
+        // Explicit DELETE: putUnreadInfo would write a `{ total: 0,
+        // highlight: 0, from: null }` entry into the Map, which keeps
+        // the room in the index and breaks parent rollup deltas on the
+        // next PUT.
+        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
+      } else {
+        setUnreadAtom({ type: 'PUT', unreadInfo: fresh });
+      }
+    };
+    mx.on(RoomEvent.Receipt, handleReceipt);
+    return () => {
+      mx.removeListener(RoomEvent.Receipt, handleReceipt);
+    };
+  }, [mx, setUnreadAtom, unreadThreadingEnabled]);
+
+  // RoomEvent.UnreadNotifications is the canonical signal for unread
+  // count change — fired by the SDK whenever main-timeline or
+  // per-thread totals shift (room.js:1354 / 1398 / 1426). Catches three
+  // scenarios the Receipt + Timeline handlers miss:
+  //
+  // (a) Local-echo own receipt: `addLocalEchoReceipt` emits
+  //     `RoomEvent.Receipt` synchronously but only zeros notification
+  //     counters when reading own last event AND non-synthetic — for
+  //     drawer-fired thread receipts, counters stay stale until the
+  //     server echoes back via /sync. The /sync echo updates counters
+  //     before firing UnreadNotifications, so handler reads fresh.
+  // (b) Cross-device own receipt arriving via /sync ephemeral.
+  // (c) Encrypted-room decryption fixing notification counts after the
+  //     fact (`fixNotificationCountOnDecryption` in client.js).
+  //
+  // Per-Room event — not re-emitted to the client. Attach to existing
+  // rooms on mount + listen to ClientEvent.Room for new joins. Mirrors
+  // pattern in roomToParents.ts. Skipped when the kill switch is off
+  // — pre-M4 only listened to Receipt (blind DELETE), so the legacy
+  // path stays bit-equivalent without this listener.
+  useEffect(() => {
+    if (!unreadThreadingEnabled) return undefined;
+
+    const recompute = (room: Room) => {
+      if (room.isSpaceRoom()) return;
+      // Skip rooms the user no longer belongs to — late UnreadNotifications
+      // emits (e.g. queued before MyMembership DELETE flushed) would
+      // otherwise re-PUT a left room into the unread index.
+      if (room.getMyMembership() !== Membership.Join) return;
+      if (getNotificationType(mx, room.roomId) === NotificationType.Mute) {
+        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
+        return;
+      }
+      const fresh = getUnreadInfo(room);
+      if (fresh.total === 0 && fresh.highlight === 0) {
+        setUnreadAtom({ type: 'DELETE', roomId: room.roomId });
+      } else {
+        setUnreadAtom({ type: 'PUT', unreadInfo: fresh });
+      }
+    };
+
+    const handlers = new Map<Room, () => void>();
+    const attach = (room: Room) => {
+      if (handlers.has(room)) return;
+      const handler = () => recompute(room);
+      room.on(RoomEvent.UnreadNotifications, handler);
+      handlers.set(room, handler);
+    };
+    const detach = (room: Room) => {
+      const handler = handlers.get(room);
+      if (!handler) return;
+      room.removeListener(RoomEvent.UnreadNotifications, handler);
+      handlers.delete(room);
+    };
+    const handleNewRoom = (room: Room) => attach(room);
+    // ClientEvent.DeleteRoom fires when the SDK drops a room (rejected
+    // invite, forget, etc) — release the per-room handler ref so the
+    // Map doesn't grow unbounded across long-running sessions.
+    const handleDeleteRoom = (deletedRoomId: string) => {
+      handlers.forEach((_handler, room) => {
+        if (room.roomId === deletedRoomId) detach(room);
+      });
+    };
+
+    mx.getRooms().forEach(attach);
+    mx.on(ClientEvent.Room, handleNewRoom);
+    mx.on(ClientEvent.DeleteRoom, handleDeleteRoom);
+
+    return () => {
+      mx.removeListener(ClientEvent.Room, handleNewRoom);
+      mx.removeListener(ClientEvent.DeleteRoom, handleDeleteRoom);
+      handlers.forEach((handler, room) => {
+        room.removeListener(RoomEvent.UnreadNotifications, handler);
+      });
+      handlers.clear();
+    };
+  }, [mx, setUnreadAtom, unreadThreadingEnabled]);
+
+  useEffect(() => {
+    setUnreadAtom({
+      type: 'RESET',
+      unreadInfos: getUnreadInfos(mx),
+    });
+  }, [mx, setUnreadAtom, roomsNotificationPreferences]);
+
+  useEffect(() => {
+    const handleMembershipChange = (room: Room, membership: string) => {
+      if (membership !== Membership.Join) {
+        setUnreadAtom({
+          type: 'DELETE',
+          roomId: room.roomId,
+        });
+      }
+    };
+    mx.on(RoomEvent.MyMembership, handleMembershipChange);
+    return () => {
+      mx.removeListener(RoomEvent.MyMembership, handleMembershipChange);
+    };
+  }, [mx, setUnreadAtom]);
+
+  useStateEventCallback(
+    mx,
+    useCallback(
+      (mEvent) => {
+        if (mEvent.getType() === StateEvent.SpaceChild) {
+          setUnreadAtom({
+            type: 'RESET',
+            unreadInfos: getUnreadInfos(mx),
+          });
+        }
+      },
+      [mx, setUnreadAtom]
+    )
+  );
+};

src/app/utils/notifications.ts

@@ -1,26 +1,49 @@
-import { MatrixClient, ReceiptType } from 'matrix-js-sdk';
+import { MatrixClient, MatrixEvent, ReceiptType, Thread } from 'matrix-js-sdk';
+
+// Walks a timeline backwards and returns the latest event that is
+// fully sent to the homeserver (not local-echo / pending). Shared by
+// the main-room and thread receipt senders so the «which event is
+// the read marker pointed at» semantic stays consistent.
+//
+// Note: deliberately does NOT skip on `evt.getId() === readEventId`.
+// SDK's `addLocalEchoReceipt` updates the local read-up-to marker
+// synchronously on every `sendReadReceipt` call (read-receipt.js:329-332),
+// so a readEventId-match short-circuit would bail on the second
+// invocation even when the server failed to process the first one
+// (network failure, 5xx, MSC3773-less server) — leaving the unread
+// counters stuck. The server is idempotent on duplicate receipts, so
+// re-sending costs at most one round-trip; callers gate on
+// `document.hasFocus()` to avoid spam from backgrounded tabs.
+const pickLatestNonPending = (events: MatrixEvent[]): MatrixEvent | null => {
+  for (let i = events.length - 1; i >= 0; i -= 1) {
+    const evt = events[i];
+    if (evt && !evt.isSending()) {
+      return evt;
+    }
+  }
+  return null;
+};
+
+const receiptType = (privateReceipt: boolean): ReceiptType =>
+  privateReceipt ? ReceiptType.ReadPrivate : ReceiptType.Read;
 
 export async function markAsRead(mx: MatrixClient, roomId: string, privateReceipt: boolean) {
   const room = mx.getRoom(roomId);
   if (!room) return;
-
-  const timeline = room.getLiveTimeline().getEvents();
-  const readEventId = room.getEventReadUpTo(mx.getUserId()!);
-
-  const getLatestValidEvent = () => {
-    for (let i = timeline.length - 1; i >= 0; i -= 1) {
-      const latestEvent = timeline[i];
-      if (latestEvent.getId() === readEventId) return null;
-      if (!latestEvent.isSending()) return latestEvent;
-    }
-    return null;
-  };
-  if (timeline.length === 0) return;
-  const latestEvent = getLatestValidEvent();
-  if (latestEvent === null) return;
-
-  await mx.sendReadReceipt(
-    latestEvent,
-    privateReceipt ? ReceiptType.ReadPrivate : ReceiptType.Read
-  );
+  const latestEvent = pickLatestNonPending(room.getLiveTimeline().getEvents());
+  if (!latestEvent) return;
+  await mx.sendReadReceipt(latestEvent, receiptType(privateReceipt));
+}
+
+// Thread-scoped variant. SDK auto-attaches `thread_id: <rootId>` via
+// `threadIdForReceipt(event)` (matrix-js-sdk client.js:2655).
+export async function markAsThreadRead(
+  mx: MatrixClient,
+  thread: Thread,
+  privateReceipt: boolean
+) {
+  if (!mx.getUserId()) return;
+  const latestEvent = pickLatestNonPending(thread.liveTimeline.getEvents());
+  if (!latestEvent) return;
+  await mx.sendReadReceipt(latestEvent, receiptType(privateReceipt));
 }