diff --git a/internal/diff/diff_test.go b/internal/diff/diff_test.go
index 9771acb..eac6b43 100644
--- a/internal/diff/diff_test.go
+++ b/internal/diff/diff_test.go
@@ -59,6 +59,46 @@ func TestDiffMarksReadOnlyForNSSOA(t *testing.T) {
 	}
 }
 
+// Global Constraint: an empty/nil template must not silently no-op — every managed
+// record in the zone must surface as a Delete, while read-only records (NS/SOA)
+// stay ReadOnly and excluded from Actionable(). This guards against mass deletion
+// bugs where a missing template accidentally wipes the zone unattended.
+func TestDiffEmptyTemplateDeletesAllManagedKeepsNSReadOnly(t *testing.T) {
+	actual := []model.Record{
+		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
+		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}},
+		{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}},
+	}
+	cs := Diff(nil, actual)
+
+	if len(cs.Diffs) != 3 {
+		t.Fatalf("expected 3 diffs (2 A deletes + 1 NS), got %d: %+v", len(cs.Diffs), cs.Diffs)
+	}
+
+	da := find(cs, "A a.example.com.")
+	if da == nil || da.Kind != Delete || da.ReadOnly {
+		t.Fatalf("A a.example.com. must be a non-read-only Delete, got %+v", da)
+	}
+	db := find(cs, "A b.example.com.")
+	if db == nil || db.Kind != Delete || db.ReadOnly {
+		t.Fatalf("A b.example.com. must be a non-read-only Delete, got %+v", db)
+	}
+	dns := find(cs, "NS example.com.")
+	if dns == nil || dns.Kind != Delete || !dns.ReadOnly {
+		t.Fatalf("NS example.com. must be a ReadOnly Delete, got %+v", dns)
+	}
+
+	act := cs.Actionable()
+	if len(act) != 2 {
+		t.Fatalf("expected 2 actionable deletes (A records only), got %d: %+v", len(act), act)
+	}
+	for _, d := range act {
+		if d.Type == model.NS {
+			t.Fatalf("NS must be excluded from Actionable(), got %+v", d)
+		}
+	}
+}
+
 func TestActionableExcludesInSyncAndReadOnly(t *testing.T) {
 	tmpl := []model.Record{
 		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},          // in sync