internal/apply/apply.go

@@ -1314,6 +1314,15 @@ func containerSpecReading(r *declaration.Container, declares, reads map[string]s
 	for _, a := range r.Args {
 		b.WriteString("arg " + a + "\n")
 	}
+	// The resolver and address are part of what was declared: a container whose dns or ip moved
+	// is a different container, or the fields could never reach one that already ran — which is
+	// exactly how their first deployment silently changed nothing.
+	for _, d := range r.Dns {
+		b.WriteString("dns " + d + "\n")
+	}
+	if r.IP != "" {
+		b.WriteString("ip " + r.IP + "\n")
+	}
 	// The cadence is part of what was declared, so a changed schedule is a changed spec — the marker
 	// moves and the install is reported "updated" and re-established. Added only when present, so no
 	// ordinary container's or run-once step's digest moves for a field it does not set.

internal/apply/vocabulary_test.go

@@ -435,3 +435,19 @@ func TestAContainerIsGivenItsResolverAndItsAddress(t *testing.T) {
 		}
 	}
 }
+
+// The resolver and address are part of the spec — a container whose dns or ip moved is a
+// different container, or the fields can never reach one that already runs. That is not
+// hypothetical: their first deployment compared equal and changed nothing.
+func TestAChangedResolverOrAddressIsAChangedContainer(t *testing.T) {
+	base := &declaration.Container{ID: "c", Name: "x", Image: "a@sha256:00"}
+	withDns := &declaration.Container{ID: "c", Name: "x", Image: "a@sha256:00", Dns: []string{"192.168.203.254"}}
+	withIP := &declaration.Container{ID: "c", Name: "x", Image: "a@sha256:00", IP: "192.168.203.254"}
+	plain := containerSpecReading(base, nil, nil)
+	if containerSpecReading(withDns, nil, nil) == plain {
+		t.Error("adding a resolver did not change the spec, so it can never reach a running container")
+	}
+	if containerSpecReading(withIP, nil, nil) == plain {
+		t.Error("adding an address did not change the spec, so it can never reach a running container")
+	}
+}