fix: send invitations with a server-scheduled organizer and match RSVPs against identities and aliases (#731)

docs/parity/05-calendar.md

@@ -22,7 +22,7 @@ RN has a solid read path (month/week/agenda, shared-calendar namespacing, per-vi
   - What RN does: `updateEvent` maps only `e.id === id` (`src/stores/calendar-store.ts:315-317`), so sibling occurrences keep the old title/time until a pull-to-refresh; `deleteEvent` removes only the tapped occurrence from state while the server destroyed the master (`:320-329`).
   - Fix hint: after mutating a `recurrenceId`/`recurrenceRules` event call `get().refresh()` (RN already has it) like WEB's `refetchAfterOccurrenceMutation`.
 
-- [ ] **RSCALE=GREGORIAN;SKIP=OMIT still emitted by the custom recurrence editor (#805)** — `P2` — `bugfix-parity`
+- [x] **RSCALE=GREGORIAN;SKIP=OMIT still emitted by the custom recurrence editor (#805)** — `P2` — `bugfix-parity` — fixed in 58a6f45
   - What WEB does: `createRecurrenceRule` deliberately omits `rscale`/`skip` because Stalwart serialises them into the RRULE and DAVx5 rejects it (ref `lib/recurrence-rule.ts:5-33`, changelog 1.9.2 #805).
   - What RN does: `buildRuleFromEditorValue` sets `rscale: 'gregorian', skip: 'omit'` on every custom rule (ref `src/lib/recurrence.ts:220-221`). RN affected: any custom recurrence created on mobile breaks Android CalDAV sync.
   - Fix hint: delete the two properties in `buildRuleFromEditorValue`; the simple presets in `EventModal.tsx:143-146` are already clean.
@@ -32,7 +32,7 @@ RN has a solid read path (month/week/agenda, shared-calendar namespacing, per-vi
   - What RN does: always fetches raw events and expands on the client (`src/stores/calendar-store.ts:228`, `src/lib/recurrence-expansion.ts`). Functionally fine on all server versions; RN's expansion file is a line-for-line port of WEB's (diffed: only comments, formatting and the `isServerRecurrenceInstance` pass-through differ).
   - Fix hint: optional. If adopted, port `recurrence-instances.ts` wholesale and the `isServerRecurrenceInstance` guard in `expandRecurringEvents`.
 
-- [ ] **Removing recurrence / participants / reminders / location on edit does not persist** — `P2` — `bug`
+- [x] **Removing recurrence / participants / reminders / location on edit does not persist** — `P2` — `bug` — fixed in 58a6f45
   - What WEB does: sends explicit `null` for `recurrenceRules` (+ `recurrenceOverrides`, `excludedRecurrenceRules`), `alerts`, `participants` (+ `replyTo`, `organizerCalendarAddress`), `locations`, `virtualLocations` when the field was cleared (ref `components/calendar/event-modal.tsx:528-549, 560-563, 588-592`).
   - What RN does: `handleSave` emits `undefined` for cleared fields (`recurrenceRules: undefined`, `participants: undefined`, `alerts: remindersToAlerts([]) === undefined`, `locations: undefined`) which JSON serialisation drops, so the server keeps the old value (ref `src/components/calendar/EventModal.tsx:262-281`, `src/lib/calendar-alerts.ts:72-73`). Setting "Does not repeat" on a recurring event, removing all attendees, deleting the last reminder or clearing the location silently does nothing.
   - Fix hint: in edit mode compare against `event` and send `null` for fields that existed and are now empty; RN's `cleanRecurrenceRules` already turns `[]`/`null` into `recurrenceRule: null` (`src/api/calendar.ts:115-118`), so `recurrenceRules: []` works today for recurrence.
@@ -43,12 +43,12 @@ RN has a solid read path (month/week/agenda, shared-calendar namespacing, per-vi
 
 ### Events: create / edit
 
-- [ ] **All-day events are created and saved one day too long** — `P1` — `rn-only-bug`
+- [x] **All-day events are created and saved one day too long** — `P1` — `rn-only-bug` — fixed in 58a6f45
   - What WEB does: seeds the end field from `getEventDisplayEndDate` (inclusive, end - 1 ms) for all-day events and builds `buildAllDayDuration(start, inclusiveEnd)` (ref `components/calendar/event-modal.tsx:274-280, 471-477`).
   - What RN does: edit seeds `end` with `getEventEndDate(event)` which is the exclusive end (start + P1D = next day 00:00) (`src/components/calendar/EventModal.tsx:198`); the all-day toggle effect pushes `end` to the next day whenever `end <= start` (`:231-242`); `handleSave` then calls `buildAllDayDuration(start, end)` which is inclusive (`:269`, `src/lib/calendar-utils.ts:183-189`), yielding `P2D` for a one-day event. Every create-via-toggle and every re-save of an all-day event adds a day.
   - Fix hint: seed/display the inclusive end (`getEventDisplayEndDate`) for all-day events, and in the all-day effect set `e = s` (same day) when `end <= start`; keep `buildAllDayDuration` inclusive.
 
-- [ ] **Events created without `timeZone` (floating time)** — `P1` — `bug`
+- [x] **Events created without `timeZone` (floating time)** — `P1` — `bug` — fixed in 58a6f45
   - What WEB does: every timed event carries `timeZone: getEffectiveTimeZone()` (all-day: `null`) so other clients and invitees resolve the wall-clock correctly (ref `components/calendar/event-modal.tsx:494-502`, `lib/timezone.ts:64-75`).
   - What RN does: `handleSave` never sets `timeZone` (`src/components/calendar/EventModal.tsx:262-281`) and `createEvent` does not add one (`src/api/calendar.ts:248-275`). Stalwart stores a floating DTSTART; attendees in other zones, CalDAV clients, and the user after travelling see wrong times; iMIP invites sent for such events are ambiguous.
   - Fix hint: set `timeZone: allDay ? null : Intl.DateTimeFormat().resolvedOptions().timeZone` (reuse `getUserTimeZone` from `src/api/calendar.ts:15`); once a custom time-zone setting exists (see below) use that.

src/api/calendar.ts

@@ -328,11 +328,15 @@ export async function deleteEvents(
 
 // RSVP to an invitation: patch the participant's participationStatus via a JSON
 // Pointer (RFC 6901) and let Stalwart send the iTIP REPLY (sendSchedulingMessages).
+// Stalwart routes the REPLY to the stored ORGANIZER (organizerCalendarAddress);
+// the RFC 8984 replyTo property is retired in jscalendarbis and ignored. The
+// caller passes `repairOrganizerAddress` only for events that lack an
+// organizer (e.g. imported ones) — attendees may not modify an existing one.
 export async function rsvpEvent(
   eventId: string,
   participantId: string,
   status: 'accepted' | 'declined' | 'tentative',
-  replyTo?: Record<string, string> | null,
+  repairOrganizerAddress?: string | null,
   targetAccountId?: string,
 ): Promise<void> {
   const accountId = targetAccountId || jmapClient.accountId;
@@ -341,7 +345,7 @@ export async function rsvpEvent(
   const patch: Record<string, unknown> = {
     [`participants/${escaped}/participationStatus`]: status,
   };
-  if (replyTo) patch.replyTo = replyTo;
+  if (repairOrganizerAddress) patch.organizerCalendarAddress = repairOrganizerAddress;
   const res = await jmapClient.request(
     [['CalendarEvent/set', { accountId, update: { [eventId]: patch }, sendSchedulingMessages: true }, '0']],
     USING,

src/components/calendar/EventDetailSheet.tsx

@@ -35,16 +35,17 @@ import { useColors } from '../../theme/colors';
 import {
   eventTimeRange,
   getEventColor,
+  getEventDisplayEndDate,
   getPrimaryCalendarId,
   timePattern,
   type TimeFormat,
 } from '../../lib/calendar-utils';
 import { alertsToReminders, formatReminder } from '../../lib/calendar-alerts';
 import {
-  findParticipantByEmail,
-  isOrganizerParticipant,
-} from '../../lib/calendar-invitation';
-import { useAccountStore } from '../../stores/account-store';
+  getParticipantList,
+  getUserParticipantId,
+  isOrganizer,
+} from '../../lib/calendar-participants';
 import { useSheetDrag } from '../../lib/use-sheet-drag';
 
 type RsvpStatus = 'accepted' | 'declined' | 'tentative';
@@ -53,6 +54,8 @@ interface EventDetailSheetProps {
   event: CalendarEvent | null;
   calendars: Calendar[];
   timeFormat?: TimeFormat;
+  // Login address + identities + aliases; finds "me" among the participants.
+  currentUserEmails?: string[];
   onClose: () => void;
   onEdit?: (event: CalendarEvent) => void;
   onDelete?: (event: CalendarEvent) => void;
@@ -61,7 +64,10 @@ interface EventDetailSheetProps {
 }
 
 function formatRange(event: CalendarEvent, timeFormat?: TimeFormat): string {
-  const { start, end, allDay } = eventTimeRange(event);
+  const { start, allDay } = eventTimeRange(event);
+  // All-day events store an exclusive end (next day 00:00); show the
+  // inclusive last day so a one-day event doesn't read as two (#318).
+  const end = allDay ? getEventDisplayEndDate(event) : eventTimeRange(event).end;
   if (allDay) {
     if (
       start.getFullYear() === end.getFullYear() &&
@@ -105,6 +111,7 @@ export function EventDetailSheet({
   event,
   calendars,
   timeFormat,
+  currentUserEmails = [],
   onClose,
   onEdit,
   onDelete,
@@ -112,7 +119,6 @@ export function EventDetailSheet({
   onRsvp,
 }: EventDetailSheetProps) {
   const c = useColors();
-  const activeEmail = useAccountStore((s) => s.getActiveAccount()?.email ?? null);
   const [rsvpBusy, setRsvpBusy] = React.useState(false);
   const styles = React.useMemo(() => makeStyles(c), [c]);
   const slideY = React.useRef(new Animated.Value(Dimensions.get('window').height)).current;
@@ -164,21 +170,24 @@ export function EventDetailSheet({
   const range = formatRange(event, timeFormat);
   const recurrence = recurrenceLabel(event);
   const reminders = alertsToReminders(event.alerts);
-  const participants = event.participants ? Object.values(event.participants) : [];
+  const participants = getParticipantList(event);
   const location = event.locations ? Object.values(event.locations)[0]?.name : undefined;
   const videoUri = event.virtualLocations ? Object.values(event.virtualLocations)[0]?.uri : undefined;
+  const isCancelled = event.status === 'cancelled';
 
   // Can the signed-in user RSVP? Only when they appear as a non-organizer
-  // participant and the caller wired an onRsvp handler.
-  const me = activeEmail ? findParticipantByEmail(event, [activeEmail]) : null;
-  const canRsvp = Boolean(onRsvp && me && !isOrganizerParticipant(me.participant));
-  const myStatus = me?.participant.participationStatus;
+  // participant (matched against every address of theirs: login, identities,
+  // aliases) and the caller wired an onRsvp handler.
+  const myParticipantId = getUserParticipantId(event, currentUserEmails);
+  const userIsOrganizer = isOrganizer(event, currentUserEmails);
+  const canRsvp = Boolean(onRsvp && myParticipantId && !userIsOrganizer);
+  const myStatus = myParticipantId ? event.participants?.[myParticipantId]?.participationStatus : undefined;
 
   const doRsvp = async (status: RsvpStatus) => {
-    if (!onRsvp || !me || rsvpBusy) return;
+    if (!onRsvp || !myParticipantId || rsvpBusy) return;
     setRsvpBusy(true);
     try {
-      await onRsvp(event, me.id, status);
+      await onRsvp(event, myParticipantId, status);
     } finally {
       setRsvpBusy(false);
     }
@@ -206,7 +215,9 @@ export function EventDetailSheet({
             <View style={styles.header}>
               <View style={[styles.colorBar, { backgroundColor: color }]} />
               <View style={styles.headerText}>
-                <Text style={styles.title}>{event.title || 'Untitled'}</Text>
+                <Text style={[styles.title, isCancelled && styles.titleCancelled]}>
+                  {event.title || 'Untitled'}
+                </Text>
                 {calendar && <Text style={styles.subtitle}>{calendar.name}</Text>}
               </View>
               <Pressable onPress={onClose} style={styles.closeBtn} hitSlop={8}>
@@ -303,21 +314,24 @@ export function EventDetailSheet({
                     {participants.length} participants
                   </Text>
                 </View>
-                {participants.map((p, idx) => (
-                  <View key={idx} style={styles.participantRow}>
+                {participants.map((p) => (
+                  <View key={p.id} style={styles.participantRow}>
                     <View
                       style={[
                         styles.participantDot,
                         {
-                          backgroundColor: statusColor(c, p.participationStatus),
+                          backgroundColor: statusColor(c, p.status),
                         },
                       ]}
                     />
                     <Text style={styles.participantName} numberOfLines={1}>
                       {p.name || p.email || 'Unknown'}
+                      {p.isOrganizer ? (
+                        <Text style={styles.participantOrganizer}> (organizer)</Text>
+                      ) : null}
                     </Text>
                     <Text style={styles.participantStatus}>
-                      {statusLabel(p.participationStatus)}
+                      {p.isOrganizer ? '' : statusLabel(p.status)}
                     </Text>
                   </View>
                 ))}
@@ -508,6 +522,7 @@ function makeStyles(c: ThemePalette) {
   colorBar: { width: 4, alignSelf: 'stretch', borderRadius: 2 },
   headerText: { flex: 1 },
   title: { ...typography.h3, color: c.text },
+  titleCancelled: { textDecorationLine: 'line-through', color: c.textMuted },
   subtitle: { ...typography.caption, color: c.textMuted, marginTop: 2 },
   closeBtn: { padding: 4 },
 
@@ -567,6 +582,7 @@ function makeStyles(c: ThemePalette) {
   },
   participantDot: { width: 8, height: 8, borderRadius: 4 },
   participantName: { flex: 1, ...typography.body, color: c.text },
+  participantOrganizer: { ...typography.caption, color: c.textMuted },
   participantStatus: { ...typography.caption, color: c.textMuted },
 
   actions: {

src/components/calendar/EventModal.tsx

@@ -29,7 +29,6 @@ import { addHours, addMinutes, format } from 'date-fns';
 import type {
   Calendar,
   CalendarEvent,
-  Participant,
   EventLocation,
   RecurrenceRule,
   VirtualLocation,
@@ -53,6 +52,12 @@ import {
   type Reminder,
 } from '../../lib/calendar-alerts';
 import { buildRecurrenceSummary, isSimpleRecurrenceRule } from '../../lib/recurrence';
+import {
+  buildParticipantMap,
+  getParticipantList,
+  seedAttendees,
+  type Attendee,
+} from '../../lib/calendar-participants';
 import { Button } from '..';
 import { ParticipantInput } from './ParticipantInput';
 import { RecurrenceEditor } from './RecurrenceEditor';
@@ -74,6 +79,9 @@ interface EventModalProps {
   calendars: Calendar[];
   defaultDate?: Date;
   defaultCalendarId?: string;
+  // Login address + identities + aliases; the first one is the organizer
+  // address of invitations sent from this editor.
+  currentUserEmails?: string[];
   onSave: (data: Partial<CalendarEvent>, calendarId: string) => void | Promise<void>;
   onDelete?: (event: CalendarEvent) => void;
   onClose: () => void;
@@ -153,6 +161,7 @@ export function EventModal({
   calendars,
   defaultDate,
   defaultCalendarId,
+  currentUserEmails = [],
   onSave,
   onDelete,
   onClose,
@@ -174,7 +183,8 @@ export function EventModal({
     || calendars[0]?.id
     || '';
   const [calendarId, setCalendarId] = React.useState<string>(fallbackCalendarId);
-  const [participants, setParticipants] = React.useState<Record<string, Participant>>({});
+  // Attendee rows only — the organizer participant is rebuilt on save.
+  const [attendees, setAttendees] = React.useState<Attendee[]>([]);
   const [recurrence, setRecurrence] = React.useState<RecurrenceOption>('none');
   const [customRule, setCustomRule] = React.useState<RecurrenceRule | null>(null);
   const [recurrenceEditorOpen, setRecurrenceEditorOpen] = React.useState(false);
@@ -202,7 +212,7 @@ export function EventModal({
       // grows the event by one day.
       setEnd(event.showWithoutTime ? getEventDisplayEndDate(event) : getEventEndDate(event));
       setCalendarId(getPrimaryCalendarId(event) || calendars[0]?.id || '');
-      setParticipants(event.participants || {});
+      setAttendees(seedAttendees(event, currentUserEmails));
       const detected = detectRecurrence(event);
       setRecurrence(detected);
       setCustomRule(detected === 'custom' ? event.recurrenceRules?.[0] ?? null : null);
@@ -223,7 +233,7 @@ export function EventModal({
         || calendars[0]?.id
         || '',
       );
-      setParticipants({});
+      setAttendees([]);
       setRecurrence('none');
       setCustomRule(null);
       setRecurrenceEditorOpen(false);
@@ -231,7 +241,7 @@ export function EventModal({
       setLocation('');
       setVideoUrl('');
     }
-  }, [visible, event, defaultDate, defaultCalendarId, calendars]);
+  }, [visible, event, defaultDate, defaultCalendarId, calendars, currentUserEmails]);
 
   React.useEffect(() => {
     if (allDay) {
@@ -295,16 +305,30 @@ export function EventModal({
         // every viewer; label the wall-clock with the zone it was entered in.
         // All-day events are date-only and carry no zone.
         timeZone: allDay ? null : getEffectiveTimeZone(),
-        participants: clearedOr(
-          Object.keys(participants).length > 0 ? participants : undefined,
-          'participants',
-        ),
         recurrenceRules: clearedOr(recurrenceRules, 'recurrenceRules'),
         alerts: clearedOr(remindersToAlerts(reminders), 'alerts'),
         useDefaultAlerts: reminders.length > 0 ? false : undefined,
         locations: clearedOr(buildLocations(location), 'locations'),
         virtualLocations: clearedOr(buildVirtualLocations(videoUrl), 'virtualLocations'),
       };
+      const organizerEmail = currentUserEmails[0];
+      if (attendees.length > 0 && organizerEmail) {
+        const organizerName =
+          (event ? getParticipantList(event).find((p) => p.isOrganizer)?.name : '') || '';
+        data.participants = buildParticipantMap(
+          { name: organizerName, email: organizerEmail },
+          attendees,
+        );
+        // Stalwart (calcard) derives the iCalendar ORGANIZER property solely from
+        // organizerCalendarAddress; without it no ORGANIZER is emitted and iTIP
+        // scheduling is silently skipped, so no invites are sent.
+        data.organizerCalendarAddress = `mailto:${organizerEmail}`;
+      } else if (attendees.length === 0 && isEdit && had('participants')) {
+        data.participants = null;
+        // Also clear the retired replyTo that older releases wrote.
+        if (event?.replyTo) data.replyTo = null;
+        if (event?.organizerCalendarAddress) data.organizerCalendarAddress = null;
+      }
       if (data.recurrenceRules === null) {
         // Dropping the rule leaves per-occurrence data dangling.
         if (had('recurrenceOverrides')) data.recurrenceOverrides = null;
@@ -619,8 +643,11 @@ export function EventModal({
             label="Participants"
           >
             <ParticipantInput
-              participants={participants}
-              onChange={setParticipants}
+              attendees={attendees}
+              onAdd={(a) => setAttendees((prev) => [...prev, a])}
+              onRemove={(email) =>
+                setAttendees((prev) => prev.filter((a) => a.email.toLowerCase() !== email.toLowerCase()))
+              }
             />
           </Section>
 

src/components/calendar/ParticipantInput.tsx

@@ -11,11 +11,13 @@ import { X } from 'lucide-react-native';
 import { radius, spacing, typography, type ThemePalette } from '../../theme/tokens';
 import { useColors } from '../../theme/colors';
 import { useContactsStore } from '../../stores/contacts-store';
-import type { Participant } from '../../api/types';
+import { useLocaleStore } from '../../stores/locale-store';
+import type { Attendee } from '../../lib/calendar-participants';
 
 interface ParticipantInputProps {
-  participants: Record<string, Participant>;
-  onChange: (next: Record<string, Participant>) => void;
+  attendees: Attendee[];
+  onAdd: (attendee: Attendee) => void;
+  onRemove: (email: string) => void;
 }
 
 interface Suggestion {
@@ -27,10 +29,6 @@ function emailRegex(): RegExp {
   return /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
 }
 
-function generateParticipantId(): string {
-  return `p-${Math.random().toString(36).slice(2, 10)}`;
-}
-
 function flattenContactEmails(): Suggestion[] {
   const contacts = useContactsStore.getState().contacts;
   const out: Suggestion[] = [];
@@ -44,15 +42,18 @@ function flattenContactEmails(): Suggestion[] {
   return out;
 }
 
-export function ParticipantInput({ participants, onChange }: ParticipantInputProps) {
+// Attendee rows only: the organizer participant is added by
+// buildParticipantMap on save (see lib/calendar-participants).
+export function ParticipantInput({ attendees, onAdd, onRemove }: ParticipantInputProps) {
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
+  const t = useLocaleStore((s) => s.t);
   const [draft, setDraft] = React.useState('');
   const [allSuggestions] = React.useState(() => flattenContactEmails());
 
   const existingEmails = React.useMemo(() => {
-    return new Set(Object.values(participants).map((p) => p.email?.toLowerCase()));
-  }, [participants]);
+    return new Set(attendees.map((a) => a.email.toLowerCase()));
+  }, [attendees]);
 
   const filteredSuggestions = React.useMemo(() => {
     const q = draft.trim().toLowerCase();
@@ -75,44 +76,24 @@ export function ParticipantInput({ participants, onChange }: ParticipantInputPro
       setDraft('');
       return;
     }
-    const id = generateParticipantId();
-    const next: Record<string, Participant> = {
-      ...participants,
-      [id]: {
-        email: trimmed,
-        name,
-        sendTo: { imip: `mailto:${trimmed}` },
-        roles: { attendee: true },
-        participationStatus: 'needs-action',
-        expectReply: true,
-      },
-    };
-    onChange(next);
+    onAdd({ name: name || '', email: trimmed });
     setDraft('');
   };
 
-  const removeParticipant = (id: string) => {
-    const next = { ...participants };
-    delete next[id];
-    onChange(next);
-  };
-
   const handleSubmit = () => {
     if (draft.trim()) addParticipant(draft);
   };
 
-  const entries = Object.entries(participants);
-
   return (
     <View style={styles.container}>
-      {entries.length > 0 && (
+      {attendees.length > 0 && (
         <View style={styles.chips}>
-          {entries.map(([id, p]) => (
-            <View key={id} style={styles.chip}>
+          {attendees.map((a) => (
+            <View key={a.email.toLowerCase()} style={styles.chip}>
               <Text style={styles.chipText} numberOfLines={1}>
-                {p.name || p.email || 'Unknown'}
+                {a.name || a.email}
               </Text>
-              <Pressable onPress={() => removeParticipant(id)} hitSlop={6}>
+              <Pressable onPress={() => onRemove(a.email)} hitSlop={6}>
                 <X size={12} color={c.textMuted} />
               </Pressable>
             </View>
@@ -123,12 +104,13 @@ export function ParticipantInput({ participants, onChange }: ParticipantInputPro
       <TextInput
         value={draft}
         onChangeText={setDraft}
-        placeholder="Add participant by email"
+        placeholder={t('calendar.event_modal.participant_placeholder', 'Add participant by email')}
         placeholderTextColor={c.textMuted}
         autoCapitalize="none"
         autoCorrect={false}
         keyboardType="email-address"
         onSubmitEditing={handleSubmit}
+        onBlur={handleSubmit}
         returnKeyType="done"
         style={styles.input}
       />

src/components/email/CalendarInvitationBanner.tsx

@@ -9,7 +9,6 @@ import { spacing, radius, typography, type ThemePalette } from '../../theme/toke
 import { useColors } from '../../theme/colors';
 import { parseCalendarBlob } from '../../api/calendar';
 import { useCalendarStore } from '../../stores/calendar-store';
-import { useAccountStore } from '../../stores/account-store';
 import { useSettingsStore } from '../../stores/settings-store';
 import {
   findCalendarAttachment,
@@ -19,6 +18,7 @@ import {
   inferInvitationMethod,
   type InvitationMethod,
 } from '../../lib/calendar-invitation';
+import { useUserCalendarAddresses } from '../../lib/calendar-user-addresses';
 
 type BannerState = 'loading' | 'parsed' | 'done' | 'error';
 type RsvpStatus = 'accepted' | 'tentative' | 'declined';
@@ -34,7 +34,9 @@ export function CalendarInvitationBanner({ email }: Props) {
   const calendars = useCalendarStore((s) => s.calendars);
   const importEvents = useCalendarStore((s) => s.importEvents);
   const rsvpEvent = useCalendarStore((s) => s.rsvpEvent);
-  const activeEmail = useAccountStore((s) => s.getActiveAccount()?.email ?? null);
+  // Login address + identities + aliases, so invitations addressed to an
+  // alias still show the RSVP buttons.
+  const currentUserEmails = useUserCalendarAddresses();
 
   const attachment = React.useMemo(() => findCalendarAttachment(email), [email]);
 
@@ -90,7 +92,7 @@ export function CalendarInvitationBanner({ email }: Props) {
   const organizer = getOrganizerName(event);
   const location = event.locations ? Object.values(event.locations)[0]?.name : undefined;
   const videoUri = event.virtualLocations ? Object.values(event.virtualLocations)[0]?.uri : undefined;
-  const me = activeEmail ? findParticipantByEmail(event, [activeEmail]) : null;
+  const me = findParticipantByEmail(event, currentUserEmails);
   const canRsvp = method !== 'cancel' && method !== 'reply' && !!me;
 
   const writableCalendar = calendars.find((cal) => !cal.myRights || cal.myRights.mayWrite !== false);
@@ -104,8 +106,8 @@ export function CalendarInvitationBanner({ email }: Props) {
       await importEvents([event], writableCalendar.id);
       // Re-read from the store to get the server-assigned id + participant.
       const stored = useCalendarStore.getState().events.find((e) => e.uid === event.uid);
-      const participant = stored && activeEmail
-        ? findParticipantByEmail(stored, [activeEmail])
+      const participant = stored
+        ? findParticipantByEmail(stored, currentUserEmails)
         : me;
       if (stored && participant) {
         await rsvpEvent(stored.id, participant.id, status, buildReplyTo(event));

src/lib/__tests__/calendar-participants.test.ts

@@ -0,0 +1,91 @@
+import { describe, it, expect } from 'vitest';
+import type { CalendarEvent } from '../../api/types';
+import {
+  buildParticipantMap,
+  collectUserCalendarAddresses,
+  getParticipantList,
+  getStatusCounts,
+  getUserParticipantId,
+  isOrganizer,
+  seedAttendees,
+} from '../calendar-participants';
+
+const event: Partial<CalendarEvent> = {
+  organizerCalendarAddress: 'mailto:Alice@example.com',
+  participants: {
+    // Stalwart rebuilds ORGANIZER into a roles-less participant (#731).
+    org: { calendarAddress: 'mailto:alice@example.com', name: 'Alice' },
+    bob: { email: 'bob@example.com', roles: { attendee: true }, participationStatus: 'accepted' },
+    carol: { calendarAddress: 'mailto:carol@example.com', roles: { attendee: true } },
+  },
+};
+
+describe('buildParticipantMap', () => {
+  it('emits an owner-only organizer plus server-scheduled attendees, deduped (#731)', () => {
+    const map = buildParticipantMap({ name: 'Alice', email: 'alice@example.com' }, [
+      { name: 'Bob', email: 'bob@example.com' },
+      { name: 'Alice again', email: 'ALICE@example.com' },
+      { name: 'Bob dup', email: 'Bob@example.com' },
+    ]);
+    const list = Object.values(map);
+    expect(list).toHaveLength(2);
+    const organizer = list.find((p) => p.roles?.owner)!;
+    expect(organizer.roles).toEqual({ owner: true });
+    expect(organizer.calendarAddress).toBe('mailto:alice@example.com');
+    expect(organizer.scheduleAgent).toBe('server');
+    expect(organizer.sendTo).toBeUndefined();
+    const bob = list.find((p) => p.email === 'bob@example.com')!;
+    expect(bob.roles).toEqual({ attendee: true });
+    expect(bob.calendarAddress).toBe('mailto:bob@example.com');
+    expect(bob.scheduleAgent).toBe('server');
+    expect(bob.expectReply).toBe(true);
+    expect(bob.participationStatus).toBe('needs-action');
+  });
+});
+
+describe('collectUserCalendarAddresses', () => {
+  it('merges groups, dedupes case-insensitively and drops blanks', () => {
+    expect(
+      collectUserCalendarAddresses(['Me@example.com'], ['me@example.com', ' ', null, 'alias@example.com']),
+    ).toEqual(['Me@example.com', 'alias@example.com']);
+  });
+});
+
+describe('organizer / participant detection', () => {
+  it('recognises the organizer via organizerCalendarAddress and an alias', () => {
+    expect(isOrganizer(event, ['alice@example.com'])).toBe(true);
+    expect(isOrganizer(event, ['bob@example.com'])).toBe(false);
+    expect(isOrganizer(event, [])).toBe(false);
+  });
+
+  it('finds the user participant by calendarAddress', () => {
+    expect(getUserParticipantId(event, ['CAROL@example.com'])).toBe('carol');
+    expect(getUserParticipantId(event, ['nobody@example.com'])).toBeNull();
+  });
+
+  it('marks the roles-less organizer participant as organizer', () => {
+    const list = getParticipantList(event);
+    expect(list.find((p) => p.id === 'org')?.isOrganizer).toBe(true);
+    expect(list.find((p) => p.id === 'bob')?.isOrganizer).toBe(false);
+    expect(list.find((p) => p.id === 'carol')?.email).toBe('carol@example.com');
+  });
+
+  it('does not count the organizer in status totals', () => {
+    expect(getStatusCounts(event)).toEqual({ accepted: 1, declined: 0, tentative: 0, 'needs-action': 1 });
+  });
+});
+
+describe('seedAttendees', () => {
+  it('never seeds the organizer or a repeated address (#731)', () => {
+    const attendees = seedAttendees(event, ['alice@example.com']);
+    expect(attendees.map((a) => a.email)).toEqual(['bob@example.com', 'carol@example.com']);
+  });
+
+  it('round-trips through buildParticipantMap without duplicating the organizer', () => {
+    const attendees = seedAttendees(event, ['alice@example.com']);
+    const map = buildParticipantMap({ name: 'Alice', email: 'alice@example.com' }, attendees);
+    const emails = Object.values(map).map((p) => p.email?.toLowerCase());
+    expect(emails.filter((e) => e === 'alice@example.com')).toHaveLength(1);
+    expect(emails).toHaveLength(3);
+  });
+});

src/lib/calendar-participants.ts

@@ -0,0 +1,249 @@
+import type { CalendarEvent, Participant } from '../api/types';
+import { generateUUID } from './uuid';
+
+// Port of the webmail's lib/calendar-participants.ts.
+
+export interface ParticipantInfo {
+  id: string;
+  name: string;
+  email: string;
+  status: Participant['participationStatus'];
+  isOrganizer: boolean;
+}
+
+export interface StatusCounts {
+  accepted: number;
+  declined: number;
+  tentative: number;
+  'needs-action': number;
+}
+
+/**
+ * Check if a participant matches any of the given email addresses.
+ * Checks p.email, p.calendarAddress (mailto:...), and p.sendTo values.
+ */
+function participantMatchesEmail(p: Participant, lowerEmails: string[]): boolean {
+  if (p.email && lowerEmails.includes(p.email.toLowerCase())) return true;
+  if (p.calendarAddress) {
+    const addr = p.calendarAddress.replace(/^mailto:/i, '').toLowerCase();
+    if (addr && lowerEmails.includes(addr)) return true;
+  }
+  if (p.sendTo) {
+    for (const addr of Object.values(p.sendTo)) {
+      const normalized = addr.replace(/^mailto:/i, '').toLowerCase();
+      if (normalized && lowerEmails.includes(normalized)) return true;
+    }
+  }
+  return false;
+}
+
+/** Best-effort scheduling address for a participant, without the mailto: scheme. */
+export function getParticipantEmail(p: Participant): string {
+  if (p.email) return p.email;
+  if (p.calendarAddress) return p.calendarAddress.replace(/^mailto:/i, '');
+  if (p.sendTo?.imip) return p.sendTo.imip.replace(/^mailto:/i, '');
+  return '';
+}
+
+/**
+ * Collects the event-level organizer calendar address(es).
+ * Stalwart conveys the organizer via `organizerCalendarAddress` / `replyTo`
+ * rather than a participant `roles.owner` flag, so self-organized events
+ * imported from another server have no owner participant to match against.
+ */
+export function getEventOrganizerEmails(event: Partial<CalendarEvent>): string[] {
+  const emails: string[] = [];
+  if (event.organizerCalendarAddress) {
+    emails.push(event.organizerCalendarAddress.replace(/^mailto:/i, '').toLowerCase());
+  }
+  if (event.replyTo) {
+    for (const addr of Object.values(event.replyTo)) {
+      emails.push(addr.replace(/^mailto:/i, '').toLowerCase());
+    }
+  }
+  return emails.filter(Boolean);
+}
+
+/**
+ * Merge the user's calendar addresses (login address, identities, account
+ * aliases) so isOrganizer() recognises alias-organized events as the user's
+ * own. De-duplicated case-insensitively (first casing kept); blanks dropped.
+ */
+export function collectUserCalendarAddresses(
+  ...groups: Array<ReadonlyArray<string | null | undefined>>
+): string[] {
+  const seen = new Set<string>();
+  const out: string[] = [];
+  for (const group of groups) {
+    for (const raw of group) {
+      const trimmed = raw?.trim();
+      if (!trimmed) continue;
+      const key = trimmed.toLowerCase();
+      if (seen.has(key)) continue;
+      seen.add(key);
+      out.push(trimmed);
+    }
+  }
+  return out;
+}
+
+export function isOrganizer(event: Partial<CalendarEvent>, userEmails: string[]): boolean {
+  if (userEmails.length === 0) return false;
+  const lower = userEmails.map((e) => e.toLowerCase());
+
+  if (event.participants) {
+    const ownerMatch = Object.values(event.participants).some(
+      (p) => p.roles?.owner && participantMatchesEmail(p, lower),
+    );
+    if (ownerMatch) return true;
+  }
+
+  // Fall back to the event-level organizer address (Stalwart / imported events
+  // mark the organizer here instead of via a participant `owner` role).
+  return getEventOrganizerEmails(event).some((email) => lower.includes(email));
+}
+
+export function getUserParticipantId(
+  event: Partial<CalendarEvent>,
+  userEmails: string[],
+): string | null {
+  if (!event.participants) return null;
+  const lower = userEmails.map((e) => e.toLowerCase());
+  for (const [id, p] of Object.entries(event.participants)) {
+    if (participantMatchesEmail(p, lower)) return id;
+  }
+  return null;
+}
+
+export function getUserStatus(
+  event: Partial<CalendarEvent>,
+  userEmails: string[],
+): Participant['participationStatus'] | null {
+  if (!event.participants) return null;
+  const lower = userEmails.map((e) => e.toLowerCase());
+  for (const p of Object.values(event.participants)) {
+    if (participantMatchesEmail(p, lower)) return p.participationStatus;
+  }
+  return null;
+}
+
+export function getParticipantList(event: Partial<CalendarEvent>): ParticipantInfo[] {
+  if (!event.participants) return [];
+  // Stalwart rebuilds the ORGANIZER line into a participant that carries only
+  // `calendarAddress` — no `roles` at all — so `roles.owner` alone would treat
+  // the organizer as a plain attendee on every re-read (#731).
+  const organizerEmails = getEventOrganizerEmails(event);
+  return Object.entries(event.participants).map(([id, p]) => {
+    const email = getParticipantEmail(p);
+    return {
+      id,
+      name: p.name || '',
+      email,
+      status: p.participationStatus || 'needs-action',
+      isOrganizer:
+        !!p.roles?.owner || (!!email && organizerEmails.includes(email.toLowerCase())),
+    };
+  });
+}
+
+export function getStatusCounts(event: Partial<CalendarEvent>): StatusCounts {
+  const counts: StatusCounts = { accepted: 0, declined: 0, tentative: 0, 'needs-action': 0 };
+  if (!event.participants) return counts;
+  const organizerEmails = getEventOrganizerEmails(event);
+  for (const p of Object.values(event.participants)) {
+    // The organizer is not awaiting their own reply; counting the roles-less
+    // participant Stalwart derives from ORGANIZER inflates the pending total.
+    const email = getParticipantEmail(p).toLowerCase();
+    if (p.roles?.owner || (email && organizerEmails.includes(email))) continue;
+    const s = p.participationStatus || 'needs-action';
+    if (s in counts) counts[s as keyof StatusCounts]++;
+  }
+  return counts;
+}
+
+export function getParticipantCount(event: Partial<CalendarEvent>): number {
+  if (!event.participants) return 0;
+  return Object.keys(event.participants).length;
+}
+
+export interface Attendee {
+  name: string;
+  email: string;
+}
+
+export function buildParticipantMap(
+  organizer: { name: string; email: string },
+  attendees: Attendee[],
+): Record<string, Participant> {
+  const participants: Record<string, Participant> = {};
+
+  const generateId = () => generateUUID();
+
+  // calendarAddress is the scheduling address in draft-ietf-calext-jscalendarbis
+  // (implemented by Stalwart); the RFC 8984 sendTo property is retired there and
+  // stored as an inert JSPROP, so it is intentionally not sent.
+  participants[generateId()] = {
+    '@type': 'Participant',
+    name: organizer.name,
+    email: organizer.email,
+    calendarAddress: `mailto:${organizer.email}`,
+    // owner only, NOT attendee: with roles.attendee set, Stalwart's server-side
+    // scheduling emits the organizer as an ATTENDEE line in addition to the
+    // ORGANIZER line, so the recipient sees the organizer listed twice.
+    roles: { owner: true },
+    participationStatus: 'accepted',
+    scheduleAgent: 'server',
+    expectReply: false,
+    kind: 'individual',
+  };
+
+  // The organizer already has an entry above, and an address must not appear
+  // twice in the invite list, so drop both cases case-insensitively (#731).
+  const seen = new Set<string>([organizer.email.trim().toLowerCase()]);
+
+  attendees.forEach((a) => {
+    const email = a.email.trim();
+    const key = email.toLowerCase();
+    if (!key || seen.has(key)) return;
+    seen.add(key);
+
+    participants[generateId()] = {
+      '@type': 'Participant',
+      name: a.name,
+      email,
+      calendarAddress: `mailto:${email}`,
+      roles: { attendee: true },
+      participationStatus: 'needs-action',
+      scheduleAgent: 'server',
+      expectReply: true,
+      kind: 'individual',
+    };
+  });
+
+  return participants;
+}
+
+/**
+ * The attendee rows an editor should start from: every participant except the
+ * organizer (who is re-added by buildParticipantMap on save), without
+ * duplicate addresses (#731).
+ */
+export function seedAttendees(
+  event: Partial<CalendarEvent> | null | undefined,
+  userEmails: string[],
+): Attendee[] {
+  if (!event?.participants) return [];
+  const excluded = new Set<string>();
+  if (isOrganizer(event, userEmails) && userEmails[0]) {
+    excluded.add(userEmails[0].toLowerCase());
+  }
+  const out: Attendee[] = [];
+  for (const p of getParticipantList(event)) {
+    if (p.isOrganizer) continue;
+    const key = p.email.trim().toLowerCase();
+    if (!key || excluded.has(key)) continue;
+    excluded.add(key);
+    out.push({ name: p.name, email: p.email.trim() });
+  }
+  return out;
+}

src/lib/calendar-user-addresses.ts

@@ -0,0 +1,70 @@
+import React from 'react';
+import { useAccountStore } from '../stores/account-store';
+import { useSettingsStore } from '../stores/settings-store';
+import { jmapClient } from '../api/jmap-client';
+import { fetchPrincipal } from '../api/account-security';
+import { collectUserCalendarAddresses } from './calendar-participants';
+
+// Account aliases come from x:Account/get (Stalwart's principal object) and
+// only change when an admin edits the account, so they're fetched once per
+// JMAP account and remembered for the session. Failure (older server, no
+// permission) simply leaves the list at login address + identities.
+const aliasCache = new Map<string, string[]>();
+const aliasInFlight = new Map<string, Promise<string[]>>();
+const aliasListeners = new Set<() => void>();
+
+function loadAliases(accountId: string): Promise<string[]> {
+  const cached = aliasCache.get(accountId);
+  if (cached) return Promise.resolve(cached);
+  const pending = aliasInFlight.get(accountId);
+  if (pending) return pending;
+  const p = fetchPrincipal()
+    .then((info) => info.emails)
+    .catch(() => [] as string[])
+    .then((emails) => {
+      aliasCache.set(accountId, emails);
+      aliasInFlight.delete(accountId);
+      for (const l of aliasListeners) l();
+      return emails;
+    });
+  aliasInFlight.set(accountId, p);
+  return p;
+}
+
+/** Test hook: forget cached aliases (also useful after re-login). */
+export function resetUserCalendarAddressCache(): void {
+  aliasCache.clear();
+  aliasInFlight.clear();
+}
+
+/**
+ * Every address the signed-in user can be addressed at for scheduling: the
+ * login address, the sending identities and the account aliases. Used to
+ * find "me" among an event's participants (RSVP), to detect alias-organized
+ * events as the user's own, and as the organizer address of new invites.
+ */
+export function useUserCalendarAddresses(): string[] {
+  const activeEmail = useAccountStore((s) => s.getActiveAccount()?.email ?? null);
+  const identities = useSettingsStore((s) => s.identities);
+  const [, bump] = React.useReducer((n: number) => n + 1, 0);
+
+  const accountId = jmapClient.isConnected ? jmapClient.accountId : null;
+  React.useEffect(() => {
+    if (!accountId) return;
+    if (aliasCache.has(accountId)) return;
+    aliasListeners.add(bump);
+    void loadAliases(accountId);
+    return () => { aliasListeners.delete(bump); };
+  }, [accountId]);
+
+  const aliases = accountId ? aliasCache.get(accountId) ?? [] : [];
+  return React.useMemo(
+    () => collectUserCalendarAddresses(
+      [activeEmail],
+      identities.map((i) => i.email),
+      aliases,
+    ),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [activeEmail, identities, aliases.join('|')],
+  );
+}

src/screens/CalendarScreen.tsx

@@ -73,6 +73,7 @@ import {
 import { generateBirthdayEvents, createBirthdayCalendar, BIRTHDAY_CALENDAR_ID } from '../lib/birthday-calendar';
 import { useContactsStore } from '../stores/contacts-store';
 import { useLocaleStore } from '../stores/locale-store';
+import { useUserCalendarAddresses } from '../lib/calendar-user-addresses';
 import type { Calendar, CalendarEvent, RecurrenceRule } from '../api/types';
 
 type ViewMode = 'month' | 'week' | 'agenda';
@@ -126,6 +127,7 @@ export default function CalendarScreen() {
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
   const t = useLocaleStore((s) => s.t);
+  const currentUserEmails = useUserCalendarAddresses();
   const calendarDefaultView = useSettingsStore((s) => s.calendarDefaultView);
   const calendarFirstDayOfWeek = useSettingsStore((s) => s.calendarFirstDayOfWeek);
   const calendarShowWeekNumbers = useSettingsStore((s) => s.calendarShowWeekNumbers);
@@ -627,6 +629,7 @@ export default function CalendarScreen() {
         event={detailEvent}
         calendars={calendars}
         timeFormat={calendarTimeFormat}
+        currentUserEmails={currentUserEmails}
         onClose={() => setDetailEvent(null)}
         onEdit={handleEditFromDetail}
         onDelete={handleDeleteFromDetail}
@@ -651,6 +654,7 @@ export default function CalendarScreen() {
         event={modalEvent}
         calendars={eventCalendars}
         defaultDate={modalDate}
+        currentUserEmails={currentUserEmails}
         onSave={handleSave}
         onDelete={handleDeleteFromModal}
         onClose={() => setModalVisible(false)}

src/stores/calendar-store.ts

@@ -375,12 +375,20 @@ export const useCalendarStore = create<CalendarState>()(
   },
 
   rsvpEvent: async (eventId, participantId, status, replyTo) => {
-    if (!participantId || participantId.includes('..')) {
+    // JMAP participant ids are opaque strings (they can contain @, ., :, /);
+    // the api layer RFC 6901-escapes them, so only reject empty values.
+    if (!participantId) {
       throw new Error('Invalid participant ID');
     }
     const storeEvent = get().events.find((e) => e.id === eventId);
     const realId = storeEvent?.originalId || eventId;
-    await apiRsvpEvent(realId, participantId, status, replyTo, storeEvent?.accountId);
+    // Repair events that are missing the organizer (e.g. imported ones) so
+    // Stalwart can route the REPLY; never touch an existing one.
+    const repair =
+      replyTo?.imip && storeEvent && !storeEvent.organizerCalendarAddress
+        ? replyTo.imip
+        : undefined;
+    await apiRsvpEvent(realId, participantId, status, repair, storeEvent?.accountId);
     set({
       events: get().events.map((e) => {
         if (e.id !== eventId || !e.participants?.[participantId]) return e;