diff --git a/src/apps/epic/views.py b/src/apps/epic/views.py
index 17e80e6..2c1ba63 100644
--- a/src/apps/epic/views.py
+++ b/src/apps/epic/views.py
@@ -803,7 +803,48 @@ def sig_ready(request, room_id):
 
 @login_required
 def sig_confirm(request, room_id):
-    """No-op: polarity confirmation is now driven server-side by threading.Timer in tasks.py."""
+    """Finalise polarity group once the countdown fires.
+    POST body: polarity=levity|gravity
+    """
+    if request.method != "POST":
+        return HttpResponse(status=405)
+    room = Room.objects.get(id=room_id)
+    if room.table_status != Room.SIG_SELECT:
+        return HttpResponse(status=400)
+    user_seat = _canonical_user_seat(room, request.user)
+    if user_seat is None:
+        return HttpResponse(status=403)
+
+    polarity = request.POST.get("polarity", SigReservation.LEVITY)
+    polarity_roles = _LEVITY_ROLES if polarity == SigReservation.LEVITY else _GRAVITY_ROLES
+
+    # Idempotency: seats already have significators
+    if not room.table_seats.filter(role__in=polarity_roles, significator__isnull=True).exists():
+        return HttpResponse(status=200)
+
+    # All three in the polarity group must be ready
+    ready_count = SigReservation.objects.filter(room=room, polarity=polarity, ready=True).count()
+    if ready_count < 3:
+        return HttpResponse(status=400)
+
+    # Assign significators from reservations
+    reservations = list(
+        SigReservation.objects.filter(room=room, polarity=polarity, ready=True)
+        .select_related('seat', 'card')
+    )
+    for res in reservations:
+        if res.seat:
+            res.seat.significator = res.card
+            res.seat.save(update_fields=['significator'])
+    SigReservation.objects.filter(room=room, polarity=polarity).update(countdown_remaining=None)
+
+    _notify_polarity_room_done(room_id, polarity)
+
+    # If both polarities are now done, advance to SKY_SELECT
+    if not room.table_seats.filter(significator__isnull=True).exists():
+        Room.objects.filter(id=room_id).update(table_status=Room.SKY_SELECT)
+        _notify_pick_sky_available(room_id)
+
     return HttpResponse(status=200)