diff --git a/supabase/migrations/20260415_add_index_active_subscription_to_tools.sql b/supabase/migrations/20260415_add_index_active_subscription_to_tools.sql
new file mode 100644
index 0000000..64185d0
--- /dev/null
+++ b/supabase/migrations/20260415_add_index_active_subscription_to_tools.sql
@@ -0,0 +1,9 @@
+-- Index for active_subscription on tools table.
+-- The active_subscription column is used as a filter predicate in multiple
+-- computed selectors (totalMonthlyCost, totalAnnualCost, renewingWithin30Days).
+-- A partial index keeps the index small and targets the common query pattern
+-- of filtering for tools with an active subscription.
+
+create index if not exists idx_tools_active_subscription
+  on tools (billing_cycle)
+  where active_subscription = true;