diff --git a/changelogs/unreleased/10307-kaovilai b/changelogs/unreleased/10307-kaovilai
new file mode 100644
index 000000000..cdb6f54a1
--- /dev/null
+++ b/changelogs/unreleased/10307-kaovilai
@@ -0,0 +1 @@
+Fix generic CSI changeID retrieval and honor snapshot class deletion policy for CBT retention
diff --git a/pkg/exposer/csi_snapshot.go b/pkg/exposer/csi_snapshot.go
index a5639537c..247ae9003 100644
--- a/pkg/exposer/csi_snapshot.go
+++ b/pkg/exposer/csi_snapshot.go
@@ -496,6 +496,7 @@ func (e *csiSnapshotExposer) CleanUp(ctx context.Context, ownerObject corev1api.
 	backupPodName := ownerObject.Name
 	backupPVCName := ownerObject.Name
 	backupVSName := ownerObject.Name
+	backupVSCName := ownerObject.Name
 
 	kube.DeletePodIfAny(ctx, e.kubeClient.CoreV1(), backupPodName, ownerObject.Namespace, e.log)
 	kube.DeletePVAndPVCIfAny(ctx, e.kubeClient.CoreV1(), backupPVCName, ownerObject.Namespace, cleanUpTimeout, e.log)
@@ -507,6 +508,13 @@ func (e *csiSnapshotExposer) CleanUp(ctx context.Context, ownerObject corev1api.
 
 	csi.DeleteVolumeSnapshotIfAny(ctx, e.csiSnapshotClient, backupVSName, ownerObject.Namespace, e.log)
 	csi.DeleteVolumeSnapshotIfAny(ctx, e.csiSnapshotClient, vsName, sourceNamespace, e.log)
+
+	// The backup VSC is created by Velero as an internal handle to the source
+	// snapshot. Deleting the backup VS above only cascades to it when its
+	// deletion policy is Delete, so remove it explicitly to avoid leaking the
+	// object under a Retain policy. Deleting a Retain VSC drops only the API
+	// object and leaves the underlying snapshot intact.
+	csi.DeleteVolumeSnapshotContentIfAny(ctx, e.csiSnapshotClient, backupVSCName, e.log)
 }
 
 func getVolumeModeByAccessMode(accessMode string, dataMover string) (corev1api.PersistentVolumeMode, error) {
@@ -571,7 +579,21 @@ func (e *csiSnapshotExposer) createBackupVSC(ctx context.Context, ownerObject co
 			Source: snapshotv1api.VolumeSnapshotContentSource{
 				SnapshotHandle: snapshotVSC.Status.SnapshotHandle,
 			},
-			DeletionPolicy:          snapshotv1api.VolumeSnapshotContentDelete,
+			// The backup VSC is statically provisioned against the same
+			// snapshot handle as the source VSC, so both objects refer to one
+			// physical snapshot. Inherit the source's deletion policy instead
+			// of forcing Delete, otherwise a user who configured Retain on the
+			// VolumeSnapshotClass still loses the snapshot when the backup VSC
+			// is cleaned up.
+			//
+			// For Case 2 storages per the design (design/block-data-mover/block-data-mover.md,
+			// e.g. Ceph RBD), inheriting Retain is not just an option but a requirement for
+			// incrementals to work at all: rbd snap diff needs the base and target snapshots
+			// in the same clone chain, so Delete destroys the base as soon as this backup
+			// completes. The next incremental's delta query then fails and degrades to an
+			// allocated-blocks backup (see the CBT tier ladder) or, without that fix, a full
+			// whole-device transfer.
+			DeletionPolicy:          snapshotVSC.Spec.DeletionPolicy,
 			Driver:                  snapshotVSC.Spec.Driver,
 			VolumeSnapshotClassName: snapshotVSC.Spec.VolumeSnapshotClassName,
 		},
diff --git a/pkg/exposer/csi_snapshot_test.go b/pkg/exposer/csi_snapshot_test.go
index 688c439a9..8502b47b8 100644
--- a/pkg/exposer/csi_snapshot_test.go
+++ b/pkg/exposer/csi_snapshot_test.go
@@ -2537,3 +2537,62 @@ func TestCleanUp_SecretsAndConfigMaps(t *testing.T) {
 	_, err = fakeKubeClient.CoreV1().Secrets("velero").Get(t.Context(), "other-secret", metav1.GetOptions{})
 	assert.NoError(t, err, "unrelated secret should not be deleted")
 }
+
+func TestCreateBackupVSCDeletionPolicy(t *testing.T) {
+	tests := []struct {
+		name           string
+		sourcePolicy   snapshotv1api.DeletionPolicy
+		expectedPolicy snapshotv1api.DeletionPolicy
+	}{
+		{
+			name:           "Delete policy is inherited",
+			sourcePolicy:   snapshotv1api.VolumeSnapshotContentDelete,
+			expectedPolicy: snapshotv1api.VolumeSnapshotContentDelete,
+		},
+		{
+			// The backup VSC points at the same snapshot handle as the source
+			// VSC, so forcing Delete here would destroy a snapshot the user
+			// asked to keep.
+			name:           "Retain policy is inherited",
+			sourcePolicy:   snapshotv1api.VolumeSnapshotContentRetain,
+			expectedPolicy: snapshotv1api.VolumeSnapshotContentRetain,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			handle := "fake-snapshot-handle"
+			className := "fake-snapshot-class"
+
+			sourceVSC := &snapshotv1api.VolumeSnapshotContent{
+				ObjectMeta: metav1.ObjectMeta{Name: "source-vsc"},
+				Spec: snapshotv1api.VolumeSnapshotContentSpec{
+					DeletionPolicy:          test.sourcePolicy,
+					Driver:                  "fake-driver",
+					VolumeSnapshotClassName: &className,
+				},
+				Status: &snapshotv1api.VolumeSnapshotContentStatus{
+					SnapshotHandle: &handle,
+				},
+			}
+
+			exposer := csiSnapshotExposer{
+				csiSnapshotClient: snapshotFake.NewSimpleClientset().SnapshotV1(),
+				log:               velerotest.NewLogger(),
+			}
+
+			ownerObject := corev1api.ObjectReference{
+				Name:      "fake-du",
+				Namespace: "velero",
+			}
+			vs := &snapshotv1api.VolumeSnapshot{
+				ObjectMeta: metav1.ObjectMeta{Name: "fake-du", Namespace: "velero"},
+			}
+
+			backupVSC, err := exposer.createBackupVSC(t.Context(), ownerObject, sourceVSC, vs)
+			require.NoError(t, err)
+			assert.Equal(t, test.expectedPolicy, backupVSC.Spec.DeletionPolicy)
+			assert.Equal(t, handle, *backupVSC.Spec.Source.SnapshotHandle)
+		})
+	}
+}
diff --git a/pkg/util/csi/cbt.go b/pkg/util/csi/cbt.go
index 00342996d..ed872023f 100644
--- a/pkg/util/csi/cbt.go
+++ b/pkg/util/csi/cbt.go
@@ -64,6 +64,11 @@ func GetCBTInfo(ctx context.Context, kubeClient kubernetes.Interface, log logrus
 
 		if vsc.Status != nil && vsc.Status.SnapshotHandle != nil {
 			cbtInfo.ChangeID = *vsc.Status.SnapshotHandle
+		} else if vsc.Spec.Source.SnapshotHandle != nil {
+			// The backup VSC is statically provisioned from the source VSC's
+			// snapshot handle; its status is populated asynchronously and may
+			// not be set yet, but the handle is already in the spec.
+			cbtInfo.ChangeID = *vsc.Spec.Source.SnapshotHandle
 		}
 
 		if pv.Spec.CSI != nil && pv.Spec.CSI.VolumeHandle != "" {