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/features/room/RoomTimeline.tsx

@@ -121,7 +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';
@@ -494,7 +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/pages/client/ClientNonUIFeatures.tsx

@@ -68,7 +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';
@@ -910,6 +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()

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 effectiveRetentionMs(event?.getContent<RetentionContent>()?.max_lifetime);
-  return typeof ms === 'number' && ms > 0 ? ms : undefined;
 };
 
+/**
+ * [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;