fixes

internal/features/spike_test.go

@@ -77,3 +77,24 @@ func TestSuppressorCooldownAndEscalation(t *testing.T) {
 		t.Fatal("alert after cooldown should pass")
 	}
 }
+
+func TestDetectSpikesWarmupGuard(t *testing.T) {
+	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
+	cfg := SpikeConfig{Window: 5 * time.Minute, BaselineWindows: 12, WarmupWindows: 6}
+	var events []Event
+	for i := 0; i < 20; i++ {
+		events = append(events, Event{Timestamp: at.Add(-time.Minute).Add(time.Duration(i) * time.Second), Service: "api", IsError: true, PatternSignature: "new"})
+	}
+	cfg.DataSince = at.Add(-10 * time.Minute) // data began 10 min ago: cold
+	if got := DetectSpikes(events, at, cfg); len(got) != 0 {
+		t.Fatalf("alerted during warm-up: %+v", got)
+	}
+	cfg.DataSince = at.Add(-2 * time.Hour) // warm
+	if got := DetectSpikes(events, at, cfg); len(got) != 1 {
+		t.Fatalf("expected alert once warm, got %+v", got)
+	}
+	cfg.DataSince = time.Time{} // guard disabled
+	if got := DetectSpikes(events, at, cfg); len(got) != 1 {
+		t.Fatalf("guard should be off when DataSince is zero")
+	}
+}