diff --git a/components/calendar/event-detail-popover.tsx b/components/calendar/event-detail-popover.tsx
index d7f1f9ba..ffa7cf68 100644
--- a/components/calendar/event-detail-popover.tsx
+++ b/components/calendar/event-detail-popover.tsx
@@ -182,7 +182,8 @@ export function EventDetailPopover({
 
   const isAttendeeMode = useMemo(() => {
     if (!event.participants) return false;
-    return !event.isOrigin && !userIsOrganizer;
+    if (userIsOrganizer) return false;
+    return event.isOrigin === false;
   }, [event, userIsOrganizer]);
 
   const userParticipantId = useMemo(
diff --git a/components/calendar/event-modal.tsx b/components/calendar/event-modal.tsx
index 27662dec..b2154f61 100644
--- a/components/calendar/event-modal.tsx
+++ b/components/calendar/event-modal.tsx
@@ -227,7 +227,12 @@ export function EventModal({
 
   const isAttendeeMode = useMemo(() => {
     if (!event || !event.participants) return false;
-    return !event.isOrigin && !userIsOrganizer;
+    // Only enter attendee (read-only + RSVP) mode when we are definitively NOT
+    // the organizer AND the event explicitly did not originate from this
+    // account. Stalwart may omit `isOrigin`, so treat a missing value as "ours"
+    // (editable) rather than locking the user out of their own events.
+    if (userIsOrganizer) return false;
+    return event.isOrigin === false;
   }, [event, userIsOrganizer]);
 
   const userParticipantId = useMemo(() => {