diff --git a/src/api/__tests__/live-stalwart-calendar.test.ts b/src/api/__tests__/live-stalwart-calendar.test.ts
new file mode 100644
index 00000000..f112f0f5
--- /dev/null
+++ b/src/api/__tests__/live-stalwart-calendar.test.ts
@@ -0,0 +1,726 @@
+/**
+ * Live calendar checks against a real Stalwart server.
+ *
+ * Opt-in like live-stalwart.test.ts: skipped unless `BULWARK_LIVE_JMAP` and
+ * `BULWARK_LIVE_PASS` are set. `BULWARK_LIVE_USER2` (same password) is the
+ * attendee of the invitations and the account that shares a calendar and a
+ * mail folder with the first one; without it those checks are skipped.
+ *
+ *   BULWARK_LIVE_JMAP=http://10.10.10.62:8120 \
+ *   BULWARK_LIVE_USER=e2e-tablet-light@example.org \
+ *   BULWARK_LIVE_USER2=e2e-tablet-land@example.org \
+ *   BULWARK_LIVE_PASS=… npx vitest run src/api/__tests__/live-stalwart-calendar.test.ts
+ *
+ * Everything it creates carries the run's marker in its title or name and is
+ * removed afterwards, also after a failed check. The events lie in 2027, away
+ * from anything a person keeps in the account.
+ *
+ * Verified against stalwartlabs/stalwart:v0.16.27 and v1.0.0.
+ */
+import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest';
+
+vi.hoisted(() => {
+  process.env.TZ = 'Europe/Berlin';
+});
+
+import { JMAPClient } from '../jmap-client';
+import { CAPABILITIES } from '../types';
+import type { Calendar, CalendarEvent, Participant } from '../types';
+import {
+  createEvent,
+  deleteEvents,
+  getCalendars,
+  getEvents,
+  queryEvents,
+  isCalendarAccessDenied,
+} from '../calendar';
+import { useCalendarStore } from '../../stores/calendar-store';
+import { useSettingsStore } from '../../stores/settings-store';
+import { saveOccurrenceEdit, deleteOccurrence, type SeriesEdit } from '../../lib/recurrence-scope-edit';
+import { editorTimesChanged, editorTimesFromEvent, eventTimeFieldsToSave } from '../../lib/event-editor-times';
+import { participantFieldsToSave, participantLimitOf, seedAttendees, type Attendee } from '../../lib/calendar-participants';
+import { expandRecurringEvents } from '../../lib/recurrence-expansion';
+import { getEventStartDate } from '../../lib/calendar-utils';
+
+const SERVER = process.env.BULWARK_LIVE_JMAP;
+const USER = process.env.BULWARK_LIVE_USER ?? 'usera@example.org';
+const USER2 = process.env.BULWARK_LIVE_USER2;
+const PASS = process.env.BULWARK_LIVE_PASS ?? '';
+const live = SERVER && PASS ? describe : describe.skip;
+const liveTwo = SERVER && PASS && USER2 ? describe : describe.skip;
+
+const USING = [CAPABILITIES.CORE, CAPABILITIES.CALENDARS];
+const MAIL_USING = [CAPABILITIES.CORE, CAPABILITIES.MAIL];
+const RUN = `live-cal-${Date.now().toString(36)}`;
+
+let client: JMAPClient;
+let other: JMAPClient | null = null;
+
+async function connectSingleton(): Promise<void> {
+  const mod = await import('../jmap-client');
+  client = new JMAPClient();
+  await client.connect(SERVER!, USER, PASS);
+  // The singleton is a const binding; copy the connected state onto it.
+  (mod.jmapClient as unknown as JMAPClient).restoreSnapshot(client.snapshot());
+  useCalendarStore.getState().reset();
+}
+
+/** The singleton the api modules use. */
+async function singleton(): Promise<JMAPClient> {
+  return (await import('../jmap-client')).jmapClient as unknown as JMAPClient;
+}
+
+type Response = [string, Record<string, any>, string];
+
+async function raw(c: JMAPClient, calls: [string, Record<string, unknown>, string][], using: string[] = USING): Promise<Response[]> {
+  return (await c.request(calls, using)).methodResponses as Response[];
+}
+
+/** Stalwart 1.0 advertises JMAP Metadata; 0.16 does not. */
+function isStalwart10(): boolean {
+  return Object.values(client.currentSession?.accounts ?? {}).some(
+    (account) => 'urn:ietf:params:jmap:metadata' in (account.accountCapabilities ?? {}),
+  );
+}
+
+async function ownCalendarId(): Promise<string> {
+  const calendars = await getCalendars();
+  const own = calendars.filter((c) => !c.accountId);
+  const cal = own.find((c) => c.isDefault) ?? own[0];
+  expect(cal, 'the account has a calendar').toBeTruthy();
+  return cal.id;
+}
+
+const SERIES_RULE = (count: number) => [{ '@type': 'RecurrenceRule', frequency: 'weekly', count }] as CalendarEvent['recurrenceRules'];
+
+function seriesData(title: string, start: string, count: number, extra: Partial<CalendarEvent> = {}): Partial<CalendarEvent> {
+  return {
+    '@type': 'Event',
+    title: `${RUN} ${title}`,
+    start,
+    duration: 'PT1H',
+    timeZone: 'Europe/Berlin',
+    recurrenceRules: SERIES_RULE(count),
+    ...extra,
+  } as Partial<CalendarEvent>;
+}
+
+/** Load [after, before] into the store and return the occurrences of `uid`, by start. */
+async function loadOccurrences(uid: string, after: string, before: string): Promise<CalendarEvent[]> {
+  const store = useCalendarStore.getState();
+  await store.fetchCalendars();
+  const ids = useCalendarStore.getState().calendars.map((c) => c.id);
+  await useCalendarStore.getState().fetchEvents(ids, after, before);
+  expect(useCalendarStore.getState().error).toBeNull();
+  return useCalendarStore.getState().events
+    .filter((e) => e.uid === uid)
+    .sort((a, b) => getEventStartDate(a).getTime() - getEventStartDate(b).getTime());
+}
+
+const startsOf = (events: CalendarEvent[]) => events.map((e) => getEventStartDate(e).toISOString());
+
+/**
+ * What the event editor (EventModal.handleSave) writes for `event` when the
+ * user changes its title, moves it by `moveMinutes` or edits the attendees.
+ */
+function editorSave(
+  event: CalendarEvent,
+  change: { title?: string; moveMinutes?: number; attendees?: Attendee[] },
+  userEmails: string[],
+): { updates: Partial<CalendarEvent>; edit: SeriesEdit; sendScheduling: boolean } {
+  const times = editorTimesFromEvent(event);
+  if (change.moveMinutes) {
+    const shift = change.moveMinutes * 60_000;
+    times.start = new Date(times.start.getTime() + shift);
+    times.end = new Date(times.end.getTime() + shift);
+  }
+  const attendees = change.attendees ?? seedAttendees(event, userEmails);
+  const updates: Partial<CalendarEvent> = {
+    title: change.title ?? event.title,
+    ...eventTimeFieldsToSave(times, event),
+    recurrenceRules: event.recurrenceRules,
+  };
+  Object.assign(updates, participantFieldsToSave(event, attendees, {
+    userEmail: userEmails[0],
+    userEmails,
+    rescheduled: editorTimesChanged(times, event),
+  }));
+  for (const key of Object.keys(updates) as (keyof CalendarEvent)[]) {
+    if (updates[key] === undefined) delete updates[key];
+  }
+  return { updates, edit: { attendees, when: times, ruleChanged: false }, sendScheduling: attendees.length > 0 };
+}
+
+function storeActions() {
+  const s = useCalendarStore.getState();
+  return { updateEvent: s.updateEvent, createEvent: s.createEvent, getMasterEvent: s.getMasterEvent, deleteEvent: s.deleteEvent };
+}
+
+/** The stored series (with its overrides) of `uid` in the account `c` serves. */
+async function seriesByUid(c: JMAPClient, uid: string): Promise<Record<string, any>[]> {
+  const res = await raw(c, [
+    ['CalendarEvent/query', { accountId: c.accountId, filter: { uid } }, 'q'],
+    ['CalendarEvent/get', {
+      accountId: c.accountId,
+      '#ids': { resultOf: 'q', name: 'CalendarEvent/query', path: '/ids' },
+      properties: ['id', 'uid', 'title', 'start', 'status', 'recurrenceRule', 'recurrenceOverrides', 'participants', 'useDefaultAlerts', 'alerts'],
+    }, 'g'],
+  ]);
+  return (res.find((r) => r[2] === 'g')?.[1].list ?? []) as Record<string, any>[];
+}
+
+async function waitFor<T>(read: () => Promise<T>, done: (value: T) => boolean, ms = 15_000): Promise<T> {
+  const until = Date.now() + ms;
+  let value = await read();
+  while (!done(value) && Date.now() < until) {
+    await new Promise((resolve) => setTimeout(resolve, 500));
+    value = await read();
+  }
+  return value;
+}
+
+function statusOf(participants: Record<string, Participant> | undefined | null, email: string): string | undefined {
+  const p = Object.values(participants ?? {}).find((x) =>
+    (x.calendarAddress ?? '').toLowerCase() === `mailto:${email.toLowerCase()}`
+    || (x.email ?? '').toLowerCase() === email.toLowerCase());
+  return p?.participationStatus;
+}
+
+/** Destroy every event of `c`'s account whose title carries the run's marker. */
+async function removeRunEvents(c: JMAPClient): Promise<void> {
+  const res = await raw(c, [
+    ['CalendarEvent/query', { accountId: c.accountId }, 'q'],
+    ['CalendarEvent/get', {
+      accountId: c.accountId,
+      '#ids': { resultOf: 'q', name: 'CalendarEvent/query', path: '/ids' },
+      properties: ['id', 'title'],
+    }, 'g'],
+  ]);
+  const ids = ((res.find((r) => r[2] === 'g')?.[1].list ?? []) as { id: string; title?: string }[])
+    .filter((e) => e.title?.includes(RUN))
+    .map((e) => e.id);
+  if (ids.length > 0) {
+    await raw(c, [['CalendarEvent/set', { accountId: c.accountId, destroy: ids, sendSchedulingMessages: false }, 'd']]);
+  }
+}
+
+live('live Stalwart calendar', () => {
+  let calendarId = '';
+
+  beforeAll(async () => {
+    await connectSingleton();
+    if (USER2) {
+      other = new JMAPClient();
+      await other.connect(SERVER!, USER2, PASS);
+    }
+    calendarId = await ownCalendarId();
+  }, 60_000);
+
+  afterAll(async () => {
+    useSettingsStore.setState({ calendarTimeZone: 'auto' });
+    await removeRunEvents(await singleton()).catch(() => undefined);
+    if (other) await removeRunEvents(other).catch(() => undefined);
+  }, 60_000);
+
+  describe('a series with overrides in its own time zone (native #89)', () => {
+    // Six Mondays at 10:00 in Berlin across the start of summer time on
+    // 28 March 2027; the second moved to 14:00 with a title of its own, the
+    // fourth excluded.
+    let uid = '';
+    let id = '';
+
+    beforeAll(async () => {
+      const created = await createEvent(seriesData('series', '2027-03-15T10:00:00', 6, {
+        recurrenceOverrides: {
+          '2027-03-22T10:00:00': { start: '2027-03-22T14:00:00', title: `${RUN} moved` },
+          '2027-04-05T10:00:00': { excluded: true },
+        } as CalendarEvent['recurrenceOverrides'],
+      }), calendarId);
+      id = created.id;
+      uid = (await getEvents([id]))[0].uid!;
+    }, 30_000);
+
+    it('cannot ask 1.0 for overrides and UTC times in one get, which is why the app reads them apart', async () => {
+      const [[name, result]] = await raw(client, [['CalendarEvent/get', {
+        accountId: client.accountId, ids: [id], properties: ['id', 'utcStart', 'recurrenceOverrides'],
+      }, '0']]);
+      if (isStalwart10()) {
+        expect(name).toBe('error');
+        expect(result.type).toBe('invalidArguments');
+      } else {
+        expect(name).toBe('CalendarEvent/get');
+      }
+    });
+
+    it('reads the series with its overrides and its UTC times', async () => {
+      const [event] = await getEvents([id]);
+      expect(event.utcStart).toBe('2027-03-15T09:00:00Z');
+      expect(Object.keys(event.recurrenceOverrides ?? {}).sort()).toEqual(['2027-03-22T10:00:00', '2027-04-05T10:00:00']);
+      expect(event.recurrenceRules?.[0]?.count).toBe(6);
+    });
+
+    it('shows the occurrences on the calendar at their Berlin clock time, moved and excluded ones included', async () => {
+      const occurrences = await loadOccurrences(uid, '2027-03-14T00:00:00.000Z', '2027-04-30T00:00:00.000Z');
+      expect(startsOf(occurrences)).toEqual([
+        '2027-03-15T09:00:00.000Z',
+        '2027-03-22T13:00:00.000Z',
+        '2027-03-29T08:00:00.000Z',
+        '2027-04-12T08:00:00.000Z',
+        '2027-04-19T08:00:00.000Z',
+      ]);
+      expect(occurrences[1].title).toBe(`${RUN} moved`);
+      expect(occurrences[2].title).toBe(`${RUN} series`);
+    });
+
+    it('expands the same occurrences on the device from the series it reads', async () => {
+      const [event] = await getEvents([id]);
+      const expanded = expandRecurringEvents([event], '2027-03-14T00:00:00.000Z', '2027-04-30T00:00:00.000Z')
+        .sort((a, b) => getEventStartDate(a).getTime() - getEventStartDate(b).getTime());
+      expect(startsOf(expanded)).toEqual([
+        '2027-03-15T09:00:00.000Z',
+        '2027-03-22T13:00:00.000Z',
+        '2027-03-29T08:00:00.000Z',
+        '2027-04-12T08:00:00.000Z',
+        '2027-04-19T08:00:00.000Z',
+      ]);
+      expect(expanded[1].title).toBe(`${RUN} moved`);
+    });
+
+    it('loads the calendar in a time zone the server does not know', async () => {
+      // Intl takes "europe/berlin"; Stalwart 1.0 refuses it (0.16 reads it as UTC).
+      const warn = vi.spyOn(console, 'warn').mockImplementation(() => undefined);
+      useSettingsStore.setState({ calendarTimeZone: 'europe/berlin' });
+      try {
+        useCalendarStore.getState().reset();
+        const occurrences = await loadOccurrences(uid, '2027-03-14T00:00:00.000Z', '2027-04-30T00:00:00.000Z');
+        expect(occurrences).toHaveLength(5);
+        // Events with a zone of their own keep their times whatever zone the query is in.
+        expect(startsOf(occurrences)[0]).toBe('2027-03-15T09:00:00.000Z');
+        const refused = warn.mock.calls.some((args) => String(args[0]).includes('does not know the time zone'));
+        expect(refused).toBe(isStalwart10());
+        // Remembered: the next reads go out in UTC without a refused request first.
+        expect((await queryEvents([], '2027-03-14T00:00:00.000Z', '2027-04-30T00:00:00.000Z')).length).toBeGreaterThan(0);
+      } finally {
+        warn.mockRestore();
+        useSettingsStore.setState({ calendarTimeZone: 'auto' });
+        useCalendarStore.getState().reset();
+      }
+    }, 30_000);
+
+    it('loads a week that starts at a midnight the clocks repeat', async () => {
+      // Havana turns its clocks back from 01:00 to 00:00 on 7 November 2027;
+      // 0.16 refused an expanded query from that midnight.
+      useSettingsStore.setState({ calendarTimeZone: 'America/Havana' });
+      try {
+        useCalendarStore.getState().reset();
+        await useCalendarStore.getState().fetchCalendars();
+        await useCalendarStore.getState().fetchEvents(
+          useCalendarStore.getState().calendars.map((c) => c.id),
+          '2027-11-07T04:00:00.000Z',
+          '2027-11-14T05:00:00.000Z',
+        );
+        expect(useCalendarStore.getState().error).toBeNull();
+        expect(useCalendarStore.getState().loadedRange).toEqual({
+          after: '2027-11-07T04:00:00.000Z', before: '2027-11-14T05:00:00.000Z',
+        });
+      } finally {
+        useSettingsStore.setState({ calendarTimeZone: 'auto' });
+        useCalendarStore.getState().reset();
+      }
+    }, 30_000);
+  });
+
+  describe('series edits from an occurrence', () => {
+    // Six Mondays from 3 May 2027 at 10:00 in Berlin, no attendees.
+    const after = '2027-05-01T00:00:00.000Z';
+    const before = '2027-06-30T00:00:00.000Z';
+    let uid = '';
+    let masterId = '';
+    const me = [USER];
+
+    beforeAll(async () => {
+      const created = await createEvent(seriesData('edits', '2027-05-03T10:00:00', 6), calendarId);
+      masterId = created.id;
+      uid = (await getEvents([masterId]))[0].uid!;
+    }, 30_000);
+
+    const at = (events: CalendarEvent[], day: string) => events.find((e) => (e.recurrenceId ?? '').startsWith(day));
+
+    it('changes the title of this occurrence only', async () => {
+      const occurrences = await loadOccurrences(uid, after, before);
+      expect(occurrences).toHaveLength(6);
+      const { updates, edit } = editorSave(at(occurrences, '2027-05-10')!, { title: `${RUN} this` }, me);
+      expect(await saveOccurrenceEdit('this', { event: at(occurrences, '2027-05-10')!, updates, editor: edit, userEmails: me }, storeActions())).toBe(true);
+
+      const [master] = await seriesByUid(client, uid);
+      expect(master.title).toBe(`${RUN} edits`);
+      expect(master.recurrenceOverrides?.['2027-05-10T10:00:00']?.title).toBe(`${RUN} this`);
+      const after1 = await loadOccurrences(uid, after, before);
+      expect(after1.map((e) => e.title)).toEqual([
+        `${RUN} edits`, `${RUN} this`, `${RUN} edits`, `${RUN} edits`, `${RUN} edits`, `${RUN} edits`,
+      ]);
+    }, 30_000);
+
+    it('moves this occurrence only', async () => {
+      const occurrences = await loadOccurrences(uid, after, before);
+      const { updates, edit } = editorSave(at(occurrences, '2027-05-17')!, { moveMinutes: 120 }, me);
+      expect(await saveOccurrenceEdit('this', { event: at(occurrences, '2027-05-17')!, updates, editor: edit, userEmails: me }, storeActions())).toBe(true);
+      const moved = await loadOccurrences(uid, after, before);
+      expect(startsOf(moved)).toEqual([
+        '2027-05-03T08:00:00.000Z', '2027-05-10T08:00:00.000Z', '2027-05-17T10:00:00.000Z',
+        '2027-05-24T08:00:00.000Z', '2027-05-31T08:00:00.000Z', '2027-06-07T08:00:00.000Z',
+      ]);
+    }, 30_000);
+
+    it('deletes this occurrence only', async () => {
+      const occurrences = await loadOccurrences(uid, after, before);
+      expect(await deleteOccurrence('this', { event: at(occurrences, '2027-05-24')!, userEmails: me }, storeActions())).toBe(true);
+      const left = await loadOccurrences(uid, after, before);
+      expect(left.map((e) => e.recurrenceId?.slice(0, 10))).toEqual(['2027-05-03', '2027-05-10', '2027-05-17', '2027-05-31', '2027-06-07']);
+      const [master] = await seriesByUid(client, uid);
+      expect(master.recurrenceOverrides?.['2027-05-24T10:00:00']?.excluded).toBe(true);
+    }, 30_000);
+
+    it('splits the series at this and the following occurrences', async () => {
+      const occurrences = await loadOccurrences(uid, after, before);
+      const { updates, edit } = editorSave(at(occurrences, '2027-05-31')!, { title: `${RUN} following` }, me);
+      expect(await saveOccurrenceEdit('this_and_future', {
+        event: at(occurrences, '2027-05-31')!, updates, editor: edit, calendarId, userEmails: me,
+      }, storeActions())).toBe(true);
+
+      const [old] = await seriesByUid(client, uid);
+      expect(old.recurrenceRule?.until).toBeTruthy();
+      expect(old.recurrenceRule?.count ?? null).toBeNull();
+      const store = useCalendarStore.getState();
+      await store.fetchEvents(store.calendars.map((c) => c.id), after, before);
+      const rest = useCalendarStore.getState().events
+        .filter((e) => e.title === `${RUN} following`)
+        .sort((a, b) => getEventStartDate(a).getTime() - getEventStartDate(b).getTime());
+      // What was left of the count: two of six.
+      expect(startsOf(rest)).toEqual(['2027-05-31T08:00:00.000Z', '2027-06-07T08:00:00.000Z']);
+      expect(rest[0].uid).not.toBe(uid);
+      const kept = await loadOccurrences(uid, after, before);
+      expect(kept.map((e) => e.recurrenceId?.slice(0, 10))).toEqual(['2027-05-03', '2027-05-10', '2027-05-17']);
+
+      // Deleting the rest from its second occurrence on ends it after its first.
+      const second = rest[1];
+      expect(await deleteOccurrence('this_and_future', { event: second, userEmails: me }, storeActions())).toBe(true);
+      const [newSeries] = await seriesByUid(client, rest[0].uid!);
+      expect(newSeries.recurrenceRule?.until).toBeTruthy();
+      await store.fetchEvents(store.calendars.map((c) => c.id), after, before);
+      expect(useCalendarStore.getState().events.filter((e) => e.uid === rest[0].uid)).toHaveLength(1);
+    }, 60_000);
+
+    it('changes and moves all occurrences, keeping each one\'s own changes', async () => {
+      let occurrences = await loadOccurrences(uid, after, before);
+      const rename = editorSave(occurrences[0], { title: `${RUN} all` }, me);
+      expect(await saveOccurrenceEdit('all', { event: occurrences[0], updates: rename.updates, editor: rename.edit, userEmails: me }, storeActions())).toBe(true);
+      occurrences = await loadOccurrences(uid, after, before);
+      expect(occurrences.map((e) => e.title)).toEqual([`${RUN} all`, `${RUN} this`, `${RUN} all`]);
+
+      // An hour later, all of them: the occurrence moved on its own keeps
+      // the time the user gave it, the one deleted stays deleted, none is
+      // listed twice.
+      const move = editorSave(occurrences[0], { moveMinutes: 60 }, me);
+      expect(await saveOccurrenceEdit('all', { event: occurrences[0], updates: move.updates, editor: move.edit, userEmails: me }, storeActions())).toBe(true);
+      occurrences = await loadOccurrences(uid, after, before);
+      expect(startsOf(occurrences)).toEqual(['2027-05-03T09:00:00.000Z', '2027-05-10T09:00:00.000Z', '2027-05-17T10:00:00.000Z']);
+      expect(occurrences.map((e) => e.title)).toEqual([`${RUN} all`, `${RUN} this`, `${RUN} all`]);
+      const [master] = await seriesByUid(client, uid);
+      expect(master.start).toBe('2027-05-03T11:00:00');
+      expect(Object.keys(master.recurrenceOverrides ?? {}).sort()).toEqual([
+        '2027-05-10T11:00:00', '2027-05-17T11:00:00', '2027-05-24T11:00:00',
+      ]);
+      expect(master.recurrenceOverrides['2027-05-24T11:00:00'].excluded).toBe(true);
+    }, 60_000);
+
+    it('deletes the whole series from an occurrence', async () => {
+      const occurrences = await loadOccurrences(uid, after, before);
+      expect(await deleteOccurrence('all', { event: occurrences[1], userEmails: me }, storeActions())).toBe(true);
+      expect(await seriesByUid(client, uid)).toHaveLength(0);
+      expect(await loadOccurrences(uid, after, before)).toHaveLength(0);
+    }, 30_000);
+  });
+
+  describe('participant limit', () => {
+    it('names the server\'s participant limit when 1.0 refuses an event with too many', async () => {
+      const participants: Record<string, Participant> = {
+        org: { '@type': 'Participant', calendarAddress: `mailto:${USER}`, roles: { owner: true }, participationStatus: 'accepted' } as Participant,
+      };
+      for (let i = 0; i < 20; i++) {
+        participants[`a${i}`] = { '@type': 'Participant', calendarAddress: `mailto:guest${i}@example.net`, roles: { attendee: true } } as Participant;
+      }
+      const event = {
+        '@type': 'Event', title: `${RUN} crowd`, start: '2027-07-05T10:00:00', duration: 'PT1H', timeZone: 'Europe/Berlin',
+        participants, organizerCalendarAddress: `mailto:${USER}`,
+      } as Partial<CalendarEvent>;
+      let error: unknown = null;
+      try {
+        const created = await createEvent(event, calendarId, false);
+        await deleteEvents([created.id], false);
+      } catch (err) {
+        error = err;
+      }
+      if (isStalwart10()) {
+        expect(participantLimitOf(error)).toBe(20);
+      } else {
+        expect(error).toBeNull();
+      }
+    }, 30_000);
+  });
+
+  describe('default alerts', () => {
+    let calendar: Calendar | undefined;
+    let before: Record<string, unknown> | null = null;
+
+    beforeAll(async () => {
+      calendar = (await getCalendars()).find((c) => c.id === calendarId);
+      before = (calendar?.defaultAlertsWithTime as Record<string, unknown> | null | undefined) ?? null;
+      await raw(client, [['Calendar/set', {
+        accountId: client.accountId,
+        update: { [calendarId]: { defaultAlertsWithTime: { d1: { '@type': 'Alert', trigger: { '@type': 'OffsetTrigger', offset: '-PT15M' } } } } },
+      }, '0']]);
+    }, 30_000);
+
+    afterAll(async () => {
+      await raw(client, [['Calendar/set', {
+        accountId: client.accountId, update: { [calendarId]: { defaultAlertsWithTime: before } },
+      }, '0']]).catch(() => undefined);
+    }, 30_000);
+
+    it('keeps the reminder changed on one occurrence of a series on the calendar\'s default reminders', async () => {
+      const created = await createEvent(seriesData('alerts', '2027-08-02T10:00:00', 3, { useDefaultAlerts: true }), calendarId);
+      const uid = (await getEvents([created.id]))[0].uid!;
+      const occurrences = await loadOccurrences(uid, '2027-08-01T00:00:00.000Z', '2027-08-31T00:00:00.000Z');
+      expect(occurrences).toHaveLength(3);
+      const own = { a1: { '@type': 'Alert', trigger: { '@type': 'OffsetTrigger', offset: '-PT1H' } } };
+      await useCalendarStore.getState().updateEvent(occurrences[1].id, { useDefaultAlerts: false, alerts: own } as Partial<CalendarEvent>);
+      const [master] = await seriesByUid(client, uid);
+      expect(master.useDefaultAlerts).toBe(false);
+      const reloaded = await loadOccurrences(uid, '2027-08-01T00:00:00.000Z', '2027-08-31T00:00:00.000Z');
+      const offsets = (e: CalendarEvent) => Object.values(e.alerts ?? {}).map((a) => (a.trigger as { offset?: string }).offset).sort();
+      expect(offsets(reloaded[1])).toEqual(['-PT1H']);
+      // The others keep the reminder the calendar gave them.
+      expect(offsets(reloaded[0])).toEqual(['-PT15M']);
+    }, 60_000);
+  });
+
+  liveTwo('invitations', () => {
+    const after = '2027-09-01T00:00:00.000Z';
+    const before = '2027-09-30T00:00:00.000Z';
+    let uid = '';
+    const me = [USER];
+
+    it('keeps the attendee\'s answer on a change and asks again when the organizer moves it', async () => {
+      // Four Mondays from 6 September 2027, the second user invited.
+      const invitation = editorSave(
+        { title: `${RUN} meeting`, start: '2027-09-06T10:00:00', duration: 'PT1H', timeZone: 'Europe/Berlin' } as CalendarEvent,
+        { attendees: [{ name: 'Land', email: USER2! }] },
+        me,
+      );
+      const created = await useCalendarStore.getState().createEvent({
+        ...seriesData('meeting', '2027-09-06T10:00:00', 4),
+        participants: invitation.updates.participants,
+        organizerCalendarAddress: invitation.updates.organizerCalendarAddress,
+      }, calendarId, { sendSchedulingMessages: true });
+      uid = created.uid!;
+
+      // The attendee's copy arrives through the server's own scheduling.
+      const copies = await waitFor(() => seriesByUid(other!, uid), (list) => list.length > 0);
+      expect(copies, 'the invitation reached the second user').toHaveLength(1);
+      const copy = copies[0];
+      const myId = Object.entries(copy.participants ?? {}).find(([, p]) =>
+        String((p as Participant).calendarAddress).toLowerCase() === `mailto:${USER2!.toLowerCase()}`)?.[0];
+      expect(myId).toBeTruthy();
+      await raw(other!, [['CalendarEvent/set', {
+        accountId: other!.accountId,
+        update: { [copy.id]: { [`participants/${myId}/participationStatus`]: 'accepted' } },
+        sendSchedulingMessages: true,
+      }, '0']]);
+      let [mine] = await waitFor(() => seriesByUid(client, uid), (list) => statusOf(list[0]?.participants, USER2!) === 'accepted');
+      expect(statusOf(mine.participants, USER2!)).toBe('accepted');
+
+      // The attendee declines the third occurrence alone, in the app.
+      (await singleton()).restoreSnapshot(other!.snapshot());
+      try {
+        useCalendarStore.getState().reset();
+        const theirs = await loadOccurrences(uid, after, before);
+        const third = theirs.find((e) => (e.recurrenceId ?? '').startsWith('2027-09-20'))!;
+        const participantId = Object.entries(third.participants ?? {}).find(([, p]) =>
+          String(p.calendarAddress).toLowerCase() === `mailto:${USER2!.toLowerCase()}`)![0];
+        await useCalendarStore.getState().rsvpEvent(third.id, participantId, 'declined', null, undefined, 'occurrence');
+      } finally {
+        await connectSingleton();
+      }
+      [mine] = await waitFor(() => seriesByUid(client, uid), (list) => {
+        const entry = list[0]?.recurrenceOverrides?.['2027-09-20T10:00:00'] as Record<string, any> | undefined;
+        return !!entry && JSON.stringify(entry).includes('declined');
+      });
+      expect(JSON.stringify(mine.recurrenceOverrides?.['2027-09-20T10:00:00'] ?? null)).toContain('declined');
+      expect(statusOf(mine.participants, USER2!)).toBe('accepted');
+
+      // A new title for all: the answer stays.
+      let occurrences = await loadOccurrences(uid, after, before);
+      const rename = editorSave(occurrences[0], { title: `${RUN} meeting renamed` }, me);
+      expect(await saveOccurrenceEdit('all', {
+        event: occurrences[0], updates: rename.updates, editor: rename.edit, sendScheduling: rename.sendScheduling, userEmails: me,
+      }, storeActions())).toBe(true);
+      [mine] = await seriesByUid(client, uid);
+      expect(mine.title).toBe(`${RUN} meeting renamed`);
+      expect(statusOf(mine.participants, USER2!)).toBe('accepted');
+      expect(JSON.stringify(mine.recurrenceOverrides?.['2027-09-20T10:00:00'] ?? null)).toContain('declined');
+      const renamed = await waitFor(() => seriesByUid(other!, uid), (list) => list[0]?.title === `${RUN} meeting renamed`);
+      expect(statusOf(renamed[0].participants, USER2!)).toBe('accepted');
+
+      // One occurrence an hour later: asked again for that one alone.
+      occurrences = await loadOccurrences(uid, after, before);
+      const moveOne = editorSave(occurrences[1], { moveMinutes: 60 }, me);
+      expect(await saveOccurrenceEdit('this', {
+        event: occurrences[1], updates: moveOne.updates, editor: moveOne.edit, sendScheduling: moveOne.sendScheduling, userEmails: me,
+      }, storeActions())).toBe(true);
+      [mine] = await seriesByUid(client, uid);
+      const override = mine.recurrenceOverrides?.['2027-09-13T10:00:00'] as Record<string, any> | undefined;
+      expect(override?.start).toBe('2027-09-13T11:00:00');
+      const overrideStatus = override?.participants
+        ? statusOf(override.participants, USER2!)
+        : Object.entries(override ?? {}).find(([k]) => k.endsWith('/participationStatus'))?.[1];
+      expect(overrideStatus).toBe('needs-action');
+      expect(statusOf(mine.participants, USER2!)).toBe('accepted');
+
+      // All of them an hour later: asked again for the series.
+      occurrences = await loadOccurrences(uid, after, before);
+      const moveAll = editorSave(occurrences[0], { moveMinutes: 60 }, me);
+      expect(await saveOccurrenceEdit('all', {
+        event: occurrences[0], updates: moveAll.updates, editor: moveAll.edit, sendScheduling: moveAll.sendScheduling, userEmails: me,
+      }, storeActions())).toBe(true);
+      [mine] = await seriesByUid(client, uid);
+      expect(mine.start).toBe('2027-09-06T11:00:00');
+      expect(statusOf(mine.participants, USER2!)).toBe('needs-action');
+
+      // Cancelled for the attendee too.
+      occurrences = await loadOccurrences(uid, after, before);
+      expect(await deleteOccurrence('all', { event: occurrences[0], userEmails: me }, storeActions())).toBe(true);
+      const gone = await waitFor(() => seriesByUid(other!, uid), (list) => list.length === 0 || list[0]?.status === 'cancelled');
+      expect(gone.length === 0 || gone[0].status === 'cancelled').toBe(true);
+    }, 120_000);
+  });
+
+  liveTwo('shares', () => {
+    let mailboxId = '';
+    let sharedCalendarId = '';
+    let principal = '';
+
+    afterAll(async () => {
+      if (!other) return;
+      if (sharedCalendarId) {
+        await raw(other, [['Calendar/set', { accountId: other.accountId, destroy: [sharedCalendarId], onDestroyRemoveEvents: true }, '0']]).catch(() => undefined);
+      }
+      if (mailboxId) {
+        await raw(other, [['Mailbox/set', { accountId: other.accountId, destroy: [mailboxId], onDestroyRemoveEmails: true }, '0']], MAIL_USING).catch(() => undefined);
+      }
+      await connectSingleton().catch(() => undefined);
+    }, 60_000);
+
+    it('asks an account that shares only mail for its calendars once, without an error', async () => {
+      principal = client.accountId;
+      const [[, created]] = await raw(other!, [['Mailbox/set', {
+        accountId: other!.accountId,
+        create: { m: { name: `${RUN} shared`, shareWith: { [principal]: { mayReadItems: true } } } },
+      }, '0']], [...MAIL_USING, 'urn:ietf:params:jmap:principals']);
+      mailboxId = created.created?.m?.id ?? '';
+      expect(mailboxId, JSON.stringify(created.notCreated)).toBeTruthy();
+
+      await connectSingleton();
+      const sharer = other!.accountId;
+      expect(client.currentSession?.accounts?.[sharer], 'the sharer\'s account is in the session').toBeTruthy();
+      // What the server answers there: 0.16 forbidden, 1.0 accountNotSupportedByMethod.
+      const [[name, answer]] = await raw(client, [['Calendar/get', { accountId: sharer, ids: [] }, '0']]);
+      expect(name).toBe('error');
+      expect(['forbidden', 'accountNotSupportedByMethod', 'accountNotFound']).toContain(answer.type);
+      const jmap = await singleton();
+      const spy = vi.spyOn(jmap, 'request');
+      try {
+        const store = useCalendarStore.getState();
+        for (let i = 0; i < 3; i++) {
+          await store.fetchCalendars();
+          await useCalendarStore.getState().fetchEvents(useCalendarStore.getState().calendars.map((c) => c.id),
+            '2027-09-01T00:00:00.000Z', '2027-09-30T00:00:00.000Z');
+          await useCalendarStore.getState().fetchTasks();
+        }
+        expect(useCalendarStore.getState().error).toBeNull();
+        const toSharer = spy.mock.calls.filter(([calls]) =>
+          (calls as unknown as [string, Record<string, unknown>][]).some(([, args]) => args.accountId === sharer));
+        // At most the one probe: no retry on every load.
+        expect(toSharer.length).toBeLessThanOrEqual(1);
+        if (toSharer.length === 1) expect(isCalendarAccessDenied(sharer)).toBe(true);
+      } finally {
+        spy.mockRestore();
+      }
+    }, 60_000);
+
+    it('shows a calendar another account shares and writes its events there', async () => {
+      const [[, created]] = await raw(other!, [['Calendar/set', {
+        accountId: other!.accountId,
+        create: { c: { name: `${RUN} team`, shareWith: { [principal]: { mayReadItems: true, mayWriteAll: true, mayWriteOwn: true, mayUpdatePrivate: true, mayRSVP: true, mayReadFreeBusy: true } } } },
+      }, '0']], [...USING, 'urn:ietf:params:jmap:principals']);
+      sharedCalendarId = created.created?.c?.id ?? '';
+      expect(sharedCalendarId, JSON.stringify(created.notCreated)).toBeTruthy();
+      const [[, made]] = await raw(other!, [['CalendarEvent/set', {
+        accountId: other!.accountId,
+        create: { e: { ...seriesData('owner series', '2027-10-04T10:00:00', 2), recurrenceRule: SERIES_RULE(2)![0], recurrenceRules: undefined, calendarIds: { [sharedCalendarId]: true } } },
+      }, '0']]);
+      expect(made.created?.e?.id, JSON.stringify(made.notCreated)).toBeTruthy();
+
+      await connectSingleton();
+      const store = useCalendarStore.getState();
+      await store.fetchCalendars();
+      const shared = useCalendarStore.getState().calendars.find((c) => c.name === `${RUN} team`);
+      expect(shared?.accountId).toBe(other!.accountId);
+      // The month as the app asks for it: from local midnight to local midnight.
+      await useCalendarStore.getState().fetchEvents(useCalendarStore.getState().calendars.map((c) => c.id),
+        '2027-09-30T22:00:00.000Z', '2027-10-30T22:00:00.000Z');
+      const theirs = useCalendarStore.getState().events
+        .filter((e) => e.title === `${RUN} owner series`)
+        .sort((a, b) => getEventStartDate(a).getTime() - getEventStartDate(b).getTime());
+      expect(theirs).toHaveLength(2);
+      expect(theirs.every((e) => e.accountId === other!.accountId && !!e.calendarIds?.[shared!.id])).toBe(true);
+
+      // An edit of one of its occurrences goes to the owner's account.
+      const { updates, edit } = editorSave(theirs[1], { title: `${RUN} owner second` }, [USER]);
+      expect(await saveOccurrenceEdit('this', { event: theirs[1], updates, editor: edit, userEmails: [USER] }, storeActions())).toBe(true);
+      const list = (await raw(other!, [['CalendarEvent/query', { accountId: other!.accountId, filter: { inCalendar: sharedCalendarId } }, 'q'],
+        ['CalendarEvent/get', { accountId: other!.accountId, '#ids': { resultOf: 'q', name: 'CalendarEvent/query', path: '/ids' }, properties: ['id', 'recurrenceOverrides'] }, 'g']]))
+        .find((r) => r[2] === 'g')?.[1].list as Record<string, any>[];
+      expect(list).toHaveLength(1);
+      expect(list[0].recurrenceOverrides?.['2027-10-11T10:00:00']?.title).toBe(`${RUN} owner second`);
+    }, 60_000);
+  });
+
+  describe('tasks', () => {
+    it('lists the account\'s own tasks and none of another account\'s', async () => {
+      const [[, created]] = await raw(client, [['CalendarEvent/set', {
+        accountId: client.accountId,
+        create: { t: { '@type': 'Task', title: `${RUN} task`, calendarIds: { [calendarId]: true }, due: '2027-11-01T10:00:00', timeZone: 'Europe/Berlin' } },
+      }, '0']]);
+      expect(created.created?.t?.id, JSON.stringify(created.notCreated)).toBeTruthy();
+      useCalendarStore.getState().reset();
+      await useCalendarStore.getState().fetchCalendars();
+      await useCalendarStore.getState().fetchTasks();
+      expect(useCalendarStore.getState().tasks.map((t) => t.title)).toContain(`${RUN} task`);
+
+      if (!USER2) return;
+      const second = new JMAPClient();
+      await second.connect(SERVER!, USER2, PASS);
+      const jmap = await singleton();
+      jmap.restoreSnapshot(second.snapshot());
+      try {
+        useCalendarStore.getState().reset();
+        await useCalendarStore.getState().fetchCalendars();
+        await useCalendarStore.getState().fetchTasks();
+        expect(useCalendarStore.getState().tasks.map((t) => t.title)).not.toContain(`${RUN} task`);
+      } finally {
+        await connectSingleton();
+      }
+    }, 60_000);
+  });
+});