diff --git a/internal/engine/bench_test.go b/internal/engine/bench_test.go
new file mode 100644
index 0000000..afd2d7c
--- /dev/null
+++ b/internal/engine/bench_test.go
@@ -0,0 +1,30 @@
+package engine
+
+import "testing"
+
+// Benchmarks are a baseline, not a gate: run them manually with
+//
+//	go test -bench=. -benchmem ./internal/engine/
+//
+// The numbers become interesting in milestone 5, when the optimisation
+// feature starts running thousands of cascades per request; comparing
+// against this baseline catches accidental quadratic behaviour.
+
+func BenchmarkHolmeKim(b *testing.B) {
+	config := DefaultConfig()
+	for b.Loop() {
+		_, err := HolmeKim(config.NumStudents, config.EdgesPerNode, config.TriangleProb, newRand(config.GraphSeed))
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkRunScenario(b *testing.B) {
+	config := DefaultConfig()
+	for b.Loop() {
+		if _, err := RunScenario(config, StrategyMostConnected); err != nil {
+			b.Fatal(err)
+		}
+	}
+}