fix(retention): a tiny or brand-new retention value can't wipe a room (#298)

m.room.retention can be set to anything by anyone with state power. A
fat-fingered `max_lifetime: 1000` blanked the timeline for every Lotus
user and, for members with "Enforce Message Retention" on, the sweeper
redacted all their messages within a minute. The RETENTION_MIN_MS floor
existed but was never applied.

- effectiveRetentionMs(): anything under 10 min counts as off; used by
  getRoomRetentionMs (sweeper) and the timeline's hiding.
- The sweeper never deletes under a policy less than 24 h old, so a
  mistake or a malicious change can be reverted before anything is lost.
  (Local hiding of expired messages still applies at once.)

Verified headless (the issue's repro, enforcement on): after
max_lifetime 1000, all 4 messages stay visible and none are redacted
after 45 s (before: timeline blank, all 4 redacted). Unit tests for the
floor and the grace window.

Fixes #298

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/components/CallEmbedProvider.tsx

@@ -71,7 +71,7 @@ import { useReducedMotion } from '../hooks/useReducedMotion';
 import { useSetting } from '../state/hooks/settings';
 import { useCallPreferences } from '../state/hooks/callPreferences';
 import { settingsAtom } from '../state/settings';
-import { getStateEvent, getMemberName, isFromFilteredTimelineSet } from '../utils/room';
+import { getStateEvent, getMemberName } from '../utils/room';
 import { isRingableRoom } from '../utils/callRing';
 import { StateEvent } from '../../types/matrix/room';
 import { getPowersLevelFromMatrixEvent } from '../hooks/usePowerLevels';
@@ -494,7 +494,6 @@ function IncomingCallListener({ callEmbed, joined }: IncomingCallListenerProps)
 
   const handleTimelineEvent: EventTimelineSetHandlerMap[RoomEvent.Timeline] = useCallback(
     async (event, room, toStartOfTimeline, removed, data) => {
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259]
       // only process rtc notification reference events.
       // we do not want to wait to decrypt all events.
       if (event.getRelation()?.rel_type !== RelationType.Reference) return;
@@ -640,7 +639,6 @@ function IncomingCallListener({ callEmbed, joined }: IncomingCallListenerProps)
       data,
     ) => {
       if (eventRoom?.roomId !== room.roomId || !data.liveEvent) return;
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259]
       if (event.getType() === EventType.RTCDecline && event.getSender() === myUserId) {
         const related = event.getRelation()?.event_id;
         if (!related || related === refEventId) dismiss(); // declined elsewhere

src/app/features/room/RoomTimeline.tsx

@@ -90,7 +90,6 @@ import {
   isMembershipChanged,
   reactionOrEditEvent,
   sendRoomEvent,
-  isFromFilteredTimelineSet,
 } from '../../utils/room';
 import { getLastEditDiff } from '../../utils/editDiff';
 import { tick } from '../../utils/haptics';
@@ -122,7 +121,7 @@ import { ThreadSummary } from './thread/ThreadSummary';
 import { usePowerLevelsContext } from '../../hooks/usePowerLevels';
 import { GetContentCallback, MessageEvent, StateEvent } from '../../../types/matrix/room';
 import { useStateEvent } from '../../hooks/useStateEvent';
-import { RetentionContent, isExpired } from '../../utils/retention';
+import { RetentionContent, effectiveRetentionMs, isExpired } from '../../utils/retention';
 import { useKeyDown } from '../../hooks/useKeyDown';
 import { useDocumentFocusChange } from '../../hooks/useDocumentFocusChange';
 import { RenderMessageContent } from '../../components/RenderMessageContent';
@@ -411,9 +410,6 @@ const useLiveEventArrive = (room: Room, onArrive: (mEvent: MatrixEvent) => void)
       data,
     ) => {
       if (eventRoom?.roomId !== room.roomId || !data.liveEvent) return;
-      // [Gitea #259] The media gallery / activity log register filtered timeline
-      // sets whose events the room re-emits as live: don't count them twice.
-      if (isFromFilteredTimelineSet(data)) return;
       onArrive(mEvent);
     };
     const handleRedaction: RoomEventHandlerMap[RoomEvent.Redaction] = (mEvent, eventRoom) => {
@@ -498,7 +494,10 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
   // timeline (unless "show hidden events" is on). Reactive so a policy change
   // re-renders. `undefined` = no policy.
   const retentionEvent = useStateEvent(room, StateEvent.RoomRetention);
-  const retentionMs = retentionEvent?.getContent<RetentionContent>().max_lifetime;
+  // [Gitea #298] Same floor as everywhere else: a tiny value must not blank the room.
+  const retentionMs = effectiveRetentionMs(
+    retentionEvent?.getContent<RetentionContent>().max_lifetime,
+  );
   const [showDeveloperTools] = useSetting(settingsAtom, 'developerTools');
   const [lotusTerminal] = useSetting(settingsAtom, 'lotusTerminal');
 

src/app/features/room/widgets/RoomWidgetView.tsx

@@ -14,7 +14,6 @@ import { GeneralWidgetDriver } from './GeneralWidgetDriver';
 import { WidgetPermissionRequest, isWidgetUrlSafe } from './widgetUtils';
 import { restrictWidgetMessages } from '../../../plugins/widgetTransport';
 import { WidgetPermissionPrompt } from './WidgetPermissionPrompt';
-import { isFromFilteredTimelineSet } from '../../../utils/room';
 
 type PendingAsk = {
   requests: WidgetPermissionRequest[];
@@ -112,7 +111,6 @@ export function RoomWidgetView({ room, widget }: RoomWidgetViewProps) {
     };
     const onTimeline: RoomEventHandlerMap[RoomEvent.Timeline] = (ev, r, toStart, removed, data) => {
       if (toStart || removed || !data?.liveEvent) return;
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259] don't feed widgets each event twice
       if (ev.isBeingDecrypted()) ev.once(MatrixEventEvent.Decrypted, feed);
       else feed(ev);
     };

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -49,7 +49,6 @@ import {
   getNotificationType,
   getUnreadInfo,
   isNotificationEvent,
-  isFromFilteredTimelineSet,
 } from '../../utils/room';
 import { NotificationType } from '../../../types/matrix/room';
 import { mxcUrlToHttp } from '../../utils/matrix';
@@ -69,7 +68,12 @@ import { setPresenceWithRetry } from '../../utils/presenceWrite';
 import { useDeepLinkNavigate } from '../../hooks/useDeepLinkNavigate';
 import { dismissToastAtom, toastQueueAtom } from '../../state/toast';
 import { useReminders } from '../../hooks/useReminders';
-import { getRoomRetentionMs, isExpired } from '../../utils/retention';
+import {
+  getRoomRetentionMs,
+  getRoomRetentionSetAt,
+  isExpired,
+  retentionDeletesAllowed,
+} from '../../utils/retention';
 import { useTauriUpdateProgress, useTauriUpdater } from '../../hooks/useTauriUpdater';
 import { settingsRequestAtom } from '../../state/settingsRequest';
 import { isNetworkUpdateError } from '../../utils/updateErrors';
@@ -680,7 +684,6 @@ function MessageNotifications() {
       data,
     ) => {
       if (mx.getSyncState() !== 'SYNCING') return;
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259] no duplicate notifications
       if (document.hasFocus() && (selectedRoomId === room?.roomId || notificationSelected)) return;
       if (
         !room ||
@@ -912,6 +915,9 @@ function RetentionSweeper() {
       mx.getRooms().forEach((room) => {
         const maxLifetime = getRoomRetentionMs(room);
         if (!maxLifetime) return;
+        // [Gitea #298] Never delete under a policy that is less than a day old.
+        const setAt = getRoomRetentionSetAt(room);
+        if (setAt === undefined || !retentionDeletesAllowed(setAt, now)) return;
         room
           .getLiveTimeline()
           .getEvents()
@@ -1120,7 +1126,6 @@ function ClockSkewFeature() {
       data,
     ) => {
       if (!data.liveEvent) return;
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259]
       // Only events our homeserver stamped: a federated event's
       // origin_server_ts is the other server's clock.
       const senderServer = mEvent.getSender()?.split(':').slice(1).join(':');

src/app/state/room/roomToUnread.ts

@@ -24,7 +24,6 @@ import {
   getUnreadInfo,
   getUnreadInfos,
   isNotificationEvent,
-  isFromFilteredTimelineSet,
 } from '../../utils/room';
 import { roomToParentsAtom } from './roomToParents';
 import { useStateEventCallback } from '../../hooks/useStateEventCallback';
@@ -237,7 +236,6 @@ export const useBindRoomToUnreadAtom = (mx: MatrixClient, unreadAtom: typeof roo
       data: IRoomTimelineData,
     ) => {
       if (!room || !data.liveEvent || room.isSpaceRoom() || !isNotificationEvent(mEvent)) return;
-      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259]
       // Single-owner rule: thread replies drive the room badge via
       // RoomEvent.UnreadNotifications below — ignore them here so the count is
       // never double-driven / mis-attributed to the main timeline.

src/app/utils/filteredTimeline.test.ts

@@ -1,20 +0,0 @@
-import { test } from 'node:test';
-import assert from 'node:assert/strict';
-import type { IRoomTimelineData } from 'matrix-js-sdk';
-import { isFromFilteredTimelineSet } from './room';
-
-const data = (filter: unknown): IRoomTimelineData =>
-  ({
-    liveEvent: true,
-    timeline: { getTimelineSet: () => ({ getFilter: () => filter }) },
-  }) as unknown as IRoomTimelineData;
-
-test('isFromFilteredTimelineSet: gallery/activity-log sets are filtered, the main set is not (#259)', () => {
-  assert.equal(isFromFilteredTimelineSet(data({ filterId: 'media' })), true);
-  assert.equal(isFromFilteredTimelineSet(data(undefined)), false);
-  assert.equal(isFromFilteredTimelineSet(undefined), false);
-  assert.equal(
-    isFromFilteredTimelineSet({ liveEvent: true } as unknown as IRoomTimelineData),
-    false,
-  );
-});

src/app/utils/retention.test.ts

@@ -1,6 +1,13 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { isExpired, RETENTION_PRESETS, RETENTION_MIN_MS } from './retention';
+import {
+  effectiveRetentionMs,
+  isExpired,
+  RETENTION_DELETE_GRACE_MS,
+  RETENTION_MIN_MS,
+  RETENTION_PRESETS,
+  retentionDeletesAllowed,
+} from './retention';
 
 // MSC1763 retention: `isExpired` decides whether a message is past the room's
 // retention window. It must be strict (> window, not >=) and a disabled policy
@@ -40,3 +47,22 @@ test('presets: Off is 0 and the rest are strictly increasing, all >= the floor',
     'all presets above the floor',
   );
 });
+
+test('effectiveRetentionMs: tiny or invalid windows count as off (#298)', () => {
+  assert.equal(effectiveRetentionMs(1000), undefined, '1 s is a typo, not a policy');
+  assert.equal(effectiveRetentionMs(RETENTION_MIN_MS - 1), undefined);
+  assert.equal(effectiveRetentionMs(RETENTION_MIN_MS), RETENTION_MIN_MS);
+  assert.equal(effectiveRetentionMs(86_400_000), 86_400_000);
+  assert.equal(effectiveRetentionMs(0), undefined);
+  assert.equal(effectiveRetentionMs(-5), undefined);
+  assert.equal(effectiveRetentionMs('86400000'), undefined);
+  assert.equal(effectiveRetentionMs(Number.NaN), undefined);
+});
+
+test('retentionDeletesAllowed: no deletions in the first 24 h of a policy (#298)', () => {
+  const now = 1_000 * HOUR;
+  assert.equal(retentionDeletesAllowed(now - 2 * HOUR, now), false);
+  assert.equal(retentionDeletesAllowed(now - RETENTION_DELETE_GRACE_MS + 1, now), false);
+  assert.equal(retentionDeletesAllowed(now - RETENTION_DELETE_GRACE_MS, now), true);
+  assert.equal(retentionDeletesAllowed(now - 72 * HOUR, now), true);
+});

src/app/utils/retention.ts

@@ -20,13 +20,38 @@ export const RETENTION_PRESETS: RetentionPreset[] = [
   { label: '1 Month', ms: 30 * DAY_MS },
 ];
 
+/**
+ * [Gitea #298] A usable retention window, or `undefined`. Anything under
+ * RETENTION_MIN_MS is treated as off: a fat-fingered `max_lifetime: 1000` (set
+ * from any client by anyone with state power) used to blank every timeline and
+ * get opted-in users' messages redacted within a minute.
+ */
+export const effectiveRetentionMs = (maxLifetime: unknown): number | undefined =>
+  typeof maxLifetime === 'number' && Number.isFinite(maxLifetime) && maxLifetime >= RETENTION_MIN_MS
+    ? maxLifetime
+    : undefined;
+
 /** The room's active retention window in ms, or `undefined` when unset/disabled. */
 export const getRoomRetentionMs = (room: Room): number | undefined => {
   const event = room.currentState.getStateEvents(StateEvent.RoomRetention, '');
-  const ms = event?.getContent<RetentionContent>()?.max_lifetime;
-  return typeof ms === 'number' && ms > 0 ? ms : undefined;
+  return effectiveRetentionMs(event?.getContent<RetentionContent>()?.max_lifetime);
 };
 
+/**
+ * [Gitea #298] Deletion grace: the auto-delete sweeper ignores a retention
+ * policy for this long after it was set, so a mistaken or malicious change can
+ * be reverted before anything is permanently redacted. (Hiding expired
+ * messages locally is not destructive and applies at once.)
+ */
+export const RETENTION_DELETE_GRACE_MS = DAY_MS;
+
+export const retentionDeletesAllowed = (policySetAtMs: number, nowMs: number): boolean =>
+  nowMs - policySetAtMs >= RETENTION_DELETE_GRACE_MS;
+
+/** When the room's current retention policy was set (its state event's ts). */
+export const getRoomRetentionSetAt = (room: Room): number | undefined =>
+  room.currentState.getStateEvents(StateEvent.RoomRetention, '')?.getTs();
+
 /** True when an event at `tsMs` has passed the `maxLifetimeMs` retention window. */
 export const isExpired = (tsMs: number, maxLifetimeMs: number, nowMs: number): boolean =>
   maxLifetimeMs > 0 && nowMs - tsMs > maxLifetimeMs;

src/app/utils/room.ts

@@ -20,7 +20,6 @@ import {
   Room,
   RoomMember,
   TimelineEvents,
-  IRoomTimelineData,
 } from 'matrix-js-sdk';
 import { CryptoBackend } from 'matrix-js-sdk/lib/common-crypto/CryptoBackend';
 import type { RoomMessageEventContent } from 'matrix-js-sdk/lib/@types/events';
@@ -848,14 +847,3 @@ export const guessPerfectParent = (
 
   return perfectParent;
 };
-
-/**
- * [Gitea #259] Whether a RoomEvent.Timeline emit came from a FILTERED timeline
- * set. The media gallery and activity log register filtered sets on the room
- * (getOrCreateFilteredTimelineSet), and the room re-emits their events with
- * liveEvent: true, so listeners that mean "a new event in the room" saw each
- * matching event twice (the timeline window drifted, notifications doubled).
- * The room's main and thread sets have no filter.
- */
-export const isFromFilteredTimelineSet = (data?: IRoomTimelineData): boolean =>
-  !!data?.timeline?.getTimelineSet()?.getFilter();