diff --git a/supabase/migrations/20260419175749_a359e1ae-edf9-4934-935f-d3c09c4b69d2.sql b/supabase/migrations/20260419175749_a359e1ae-edf9-4934-935f-d3c09c4b69d2.sql
new file mode 100644
index 0000000..e36b585
--- /dev/null
+++ b/supabase/migrations/20260419175749_a359e1ae-edf9-4934-935f-d3c09c4b69d2.sql
@@ -0,0 +1,37 @@
+
+-- Replace partial unique indexes on external_id with full unique constraints
+-- so PostgREST .upsert(onConflict: 'external_id') can match them.
+-- Postgres allows multiple NULLs in a UNIQUE constraint, so partial index is unnecessary.
+
+DO $$
+DECLARE
+  t text;
+  tables text[] := ARRAY[
+    'cases','clients','contacts','homeowners','tasks','events','call_logs',
+    'expenses','invoices','time_entries','status_updates','documents'
+  ];
+BEGIN
+  FOREACH t IN ARRAY tables LOOP
+    -- Drop the old partial unique index if present
+    EXECUTE format('DROP INDEX IF EXISTS public.%I', t || '_external_id_uidx');
+    -- Drop legacy duplicate if present
+    EXECUTE format('DROP INDEX IF EXISTS public.%I', t || '_external_id_key');
+
+    -- Add a real UNIQUE constraint (only if not already present)
+    IF NOT EXISTS (
+      SELECT 1
+      FROM pg_constraint c
+      JOIN pg_class r ON r.oid = c.conrelid
+      JOIN pg_namespace n ON n.oid = r.relnamespace
+      WHERE n.nspname = 'public'
+        AND r.relname = t
+        AND c.contype = 'u'
+        AND c.conname = t || '_external_id_unique'
+    ) THEN
+      EXECUTE format(
+        'ALTER TABLE public.%I ADD CONSTRAINT %I UNIQUE (external_id)',
+        t, t || '_external_id_unique'
+      );
+    END IF;
+  END LOOP;
+END $$;