diff --git a/supabase/migrations/20260419002044_99d5c58a-bba9-4a99-97b7-21ff6daea6b2.sql b/supabase/migrations/20260419002044_99d5c58a-bba9-4a99-97b7-21ff6daea6b2.sql
new file mode 100644
index 0000000..81e16b1
--- /dev/null
+++ b/supabase/migrations/20260419002044_99d5c58a-bba9-4a99-97b7-21ff6daea6b2.sql
@@ -0,0 +1,3 @@
+CREATE UNIQUE INDEX IF NOT EXISTS time_entries_external_id_key
+  ON public.time_entries (external_id)
+  WHERE external_id IS NOT NULL;
\ No newline at end of file