fix: preserve cross-pod message order

loadtest/im-pressure/merge_test.go

@@ -148,6 +148,43 @@ func TestRunMergeReportsSameClockDeliveryLatency(t *testing.T) {
 	}
 }
 
+func TestRunMergeTreatsLateSuccessAsFinalAcceptance(t *testing.T) {
+	dir := t.TempDir()
+	late := AgentSummary{
+		RunID: "run1", Scenario: "group", Machine: "a", ExpectedConnections: 1, ReadyConnections: 1,
+		PublishAttempted: 1, PublishAccepted: 0, CtrlTrackingEnabled: true,
+		PublishCtrlObserved: 1, PublishLateCtrl: 1, PublishCtrlUnresolved: 0,
+		PublishErrors:          map[string]int64{"ctrl_timeout": 1},
+		CtrlObservationSamples: []CtrlObservationSample{{Code: 202, Late: true}},
+		Errors:                 []string{"publish message-1: ctrl timeout id=pub-a-1"},
+	}
+	timely := AgentSummary{
+		RunID: "run1", Scenario: "group", Machine: "b", ExpectedConnections: 1, ReadyConnections: 1,
+		PublishAttempted: 1, PublishAccepted: 1, CtrlTrackingEnabled: true,
+		PublishCtrlObserved: 1, PublishErrors: map[string]int64{},
+	}
+	aPath, bPath, reportPath := filepath.Join(dir, "a.json"), filepath.Join(dir, "b.json"), filepath.Join(dir, "report.json")
+	writeSummaryForTest(t, aPath, late)
+	writeSummaryForTest(t, bPath, timely)
+	if err := runMerge(aPath, bPath, reportPath); err != nil {
+		t.Fatal(err)
+	}
+	var report CombinedReport
+	raw, err := os.ReadFile(reportPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = json.Unmarshal(raw, &report); err != nil {
+		t.Fatal(err)
+	}
+	if report.PublishAccepted != 1 || report.PublishLateAccepted != 1 || report.PublishFinalAccepted != 2 || report.PublishSuccessRate != 1 {
+		t.Fatalf("late acceptance was not included in final publish outcome: %+v", report)
+	}
+	if !report.Passed || len(report.FailureReasons) != 0 {
+		t.Fatalf("resolved late ACK must not fail the report: %+v", report.FailureReasons)
+	}
+}
+
 func writeSummaryForTest(t *testing.T, path string, summary AgentSummary) {
 	t.Helper()
 	raw, err := json.Marshal(summary)