diff --git a/supabase/migrations/0004_fix_log_event_alight_record.sql b/supabase/migrations/0004_fix_log_event_alight_record.sql
new file mode 100644
index 0000000..15d4df2
--- /dev/null
+++ b/supabase/migrations/0004_fix_log_event_alight_record.sql
@@ -0,0 +1,78 @@
+create or replace function commute.log_event(
+  p_secret    text,
+  p_direction text,
+  p_event     text,
+  p_weather   text default 'unknown',
+  p_temp_c    numeric default null,
+  p_lat       numeric default null,
+  p_lon       numeric default null,
+  p_note      text default null
+) returns jsonb
+language plpgsql security definer
+set search_path = commute, public
+as $$
+declare
+  v_now        timestamptz := now();
+  v_local      timestamp   := (v_now at time zone 'Asia/Taipei');
+  v_weekday    smallint    := extract(isodow from v_local)::smallint;
+  v_date       date        := v_local::date;
+  v_time       time        := v_local::time;
+  v_id         uuid;
+  v_pred       record;
+  v_src        text        := null;
+  v_prediction jsonb       := null;
+begin
+  if not commute.check_secret(p_secret) then
+    raise exception 'unauthorized' using errcode = '42501';
+  end if;
+
+  if p_direction not in ('to_work','from_work') then
+    raise exception 'invalid direction' using errcode = '22023';
+  end if;
+  if p_event not in ('board','alight') then
+    raise exception 'invalid event' using errcode = '22023';
+  end if;
+
+  insert into commute.events
+    (event_at, local_date, local_time, weekday, direction, event, weather, temp_c, lat, lon, note)
+  values
+    (v_now, v_date, v_time, v_weekday,
+     p_direction, p_event, p_weather, p_temp_c, p_lat, p_lon, p_note)
+  returning id into v_id;
+
+  if p_event = 'board' then
+    select * into v_pred from commute.predictions
+    where direction = p_direction
+      and weekday   = v_weekday
+      and weather   = p_weather
+      and n >= 3;
+    if found then v_src := 'weather'; end if;
+
+    if not found then
+      select * into v_pred from commute.predictions_weekday
+      where direction = p_direction
+        and weekday   = v_weekday
+        and n >= 3;
+      if found then v_src := 'weekday'; end if;
+    end if;
+
+    if v_src is not null then
+      v_prediction := jsonb_build_object(
+        'median_min', v_pred.median_min,
+        'p90_min',    v_pred.p90_min,
+        'n',          v_pred.n,
+        'source',     v_src
+      );
+    end if;
+  end if;
+
+  return jsonb_build_object(
+    'id', v_id,
+    'logged_at', v_now,
+    'local_date', v_date,
+    'local_time', v_time,
+    'weekday', v_weekday,
+    'prediction', v_prediction
+  );
+end;
+$$;