diff --git a/internal/store/migrations/084-index-session-messages.sql b/internal/store/migrations/084-index-session-messages.sql
new file mode 100644
index 0000000..7d319bd
--- /dev/null
+++ b/internal/store/migrations/084-index-session-messages.sql
@@ -0,0 +1 @@
+CREATE INDEX events_message_session ON events(agent_session_id, seq) WHERE kind = 'user.message';