diff --git a/backend/migrations/077_add_usage_log_requested_model.sql b/backend/migrations/077_add_usage_log_requested_model.sql
new file mode 100644
index 00000000..4b87df86
--- /dev/null
+++ b/backend/migrations/077_add_usage_log_requested_model.sql
@@ -0,0 +1,3 @@
+-- Add requested_model field to usage_logs for normalized request/upstream model tracking.
+-- NULL means historical rows written before requested_model dual-write was introduced.
+ALTER TABLE usage_logs ADD COLUMN IF NOT EXISTS requested_model VARCHAR(100);
diff --git a/backend/migrations/078_add_usage_log_requested_model_index_notx.sql b/backend/migrations/078_add_usage_log_requested_model_index_notx.sql
new file mode 100644
index 00000000..c3412562
--- /dev/null
+++ b/backend/migrations/078_add_usage_log_requested_model_index_notx.sql
@@ -0,0 +1,3 @@
+-- Support requested_model / upstream_model aggregations with time-range filters.
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_usage_logs_created_requested_model_upstream_model
+ON usage_logs (created_at, requested_model, upstream_model);