apps/app/src/pages/events/[id]/timetable/index.vue

@@ -51,7 +51,12 @@ const eventIdRef = eventId
 const { data: eventDetail } = useEventDetail(orgId, eventId)
 const { data: subEvents } = useEventChildren(orgId, eventId)
 
-const isFlatEvent = computed(() => !subEvents.value || subEvents.value.length === 0)
+// Authoritative once eventDetail loads (single-row endpoint, fast).
+// Pre-load it returns `false`, which keeps dayOptions empty until we
+// actually know whether this is a flat event or a festival — avoids the
+// `?day={festival_id}` URL flicker that occurred when subEvents was
+// still pending (it was being read as "no children → flat event").
+const isFlatEvent = computed(() => eventDetail.value?.event_type === 'event')
 
 const dayOptions = computed(() => {
   if (isFlatEvent.value && eventDetail.value)