diff --git a/internal/compose/resolution/declaration.go b/internal/compose/resolution/declaration.go
index 6f0f165..3133367 100644
--- a/internal/compose/resolution/declaration.go
+++ b/internal/compose/resolution/declaration.go
@@ -147,7 +147,7 @@ func resolutionCompose(r mcat.Resolution, with mcat.Rendering, owner map[string]
 	// Before placing, because a placement is a setting too.
 	left := LeftOut(r, with.Settings, with.Adopted)
 	kept := make([]mcat.Manifest, 0, len(r.Modules))
-	var stillBackedUp []mcat.Manifest
+	var stillBackedUp, stillRunning []mcat.Manifest
 	for module, why := range with.NotPlaced {
 		if _, already := left[module]; !already {
 			left[module] = why
@@ -162,6 +162,10 @@ func resolutionCompose(r mcat.Resolution, with mcat.Rendering, owner map[string]
 			// the data it already holds on the machine is the reason to keep copying it. Only its data,
 			// as the backup holder's lines are derived from it, and the directories they name.
 			stillBackedUp = append(stillBackedUp, backupView(m))
+			// **And what it runs is still let through** (issue 1966): its containers and services are left as they run, so
+			// the filter keeps opening what its listens say, at the machine ports this node holds for it, rather than
+			// closing a port that still serves (the artifact store's 5100 on the control-node, 98 minutes).
+			stillRunning = append(stillRunning, m)
 			continue
 		}
 		kept = append(kept, m)
@@ -255,7 +259,9 @@ func resolutionCompose(r mcat.Resolution, with mcat.Rendering, owner map[string]
 	// Once, from every module's listens -- not per module. A module receiving only its own ports
 	// would write a rule set that closed every other module on the machine. Each module's per-node
 	// exposure settings override its listens' source first (novox/hq ADR 0046).
-	rules, err := Rules(r, with)
+	filtered := r
+	filtered.Modules = append(slices.Clone(r.Modules), stillRunning...)
+	rules, err := Rules(filtered, with)
 	if err != nil {
 		return nil, err
 	}
@@ -1242,46 +1248,19 @@ func resolutionFiltersHere(r mcat.Resolution) string {
 // is adopted or converged — the one loads it as a filter, the other declares it as openings.
 func Rules(r mcat.Resolution, with mcat.Rendering) ([]mcat.Rule, error) {
 	// A module whose settings cannot compose is left out of the declaration (novox/hq ADR 0163,
-	// rule 6), and out of the filter with it: nothing of it is declared, so nothing of it is let
-	// through.
+	// rule 6), and not out of the filter: what it runs is left running, so a port it serves stays
+	// open (issue 1966). Its per-node exposure and reaches still narrow it (ADR 0046); where they
+	// cannot be read for it, its listens open no wider than the mesh, never at the manifest's
+	// default, which could reopen a port an operator had narrowed.
 	left := LeftOut(r, with.Settings, with.Adopted)
 	exposure := map[string]map[int]string{}
 	for _, m := range r.Modules {
-		if _, isLeft := left[m.Module]; isLeft {
-			continue
-		}
-		e, err := Exposure(m, with.Settings[m.Module])
+		e, err := exposureOf(m, with.Settings[m.Module])
 		if err != nil {
-			return nil, err
-		}
-		// And how far each endpoint reaches, which says the same thing to the filter and more
-		// besides (novox/hq ADR 0138). Folded in here rather than beside: the filter has one
-		// question — from where — and a reach answers it, so giving it two inputs would let them
-		// disagree. Reaches refuses a port that both name, so this cannot silently prefer one.
-		reaches, err := Reaches(m, with.Settings[m.Module])
-		if err != nil {
-			return nil, err
-		}
-		// **Only for an endpoint the proxy does not serve.** A routed endpoint's port is how the
-		// proxy reaches it and nothing else (ADR 0045), so `public` there asks for a public name and
-		// says nothing about the port — opening it to the world as well would undo the arrangement
-		// the proxy exists for, and would silently reopen a port an operator had narrowed.
-		//
-		// Found by trying to express a real module: one whose routed name must be public and whose
-		// machine-side port must not be. Under one value for both, there was no way to say it.
-		routed := RoutedPorts(m)
-		for port, reach := range reaches {
-			if routed[port] {
-				continue
+			if _, isLeft := left[m.Module]; !isLeft {
+				return nil, err
 			}
-			source, ok := FilterSource(reach)
-			if !ok {
-				return nil, fmt.Errorf("%s: %q is not a reach the filter can read", m.Module, reach)
-			}
-			if e == nil {
-				e = map[int]string{}
-			}
-			e[port] = source
+			e = noWiderThanTheMesh(m)
 		}
 		if e != nil {
 			exposure[m.Module] = e
@@ -1290,6 +1269,60 @@ func Rules(r mcat.Resolution, with mcat.Rendering) ([]mcat.Rule, error) {
 	return Filtering(r, with.Generators, with.Ports, exposure)
 }
 
+// noWiderThanTheMesh is the exposure of a module left out whose own cannot be read: each of its
+// listens from wider than the mesh narrowed to the mesh, a narrower one kept.
+func noWiderThanTheMesh(m mcat.Manifest) map[int]string {
+	var e map[int]string
+	for _, l := range m.Listens {
+		if l.From == mcat.FromLocalNetwork || l.From == mcat.FromEverywhere {
+			if e == nil {
+				e = map[int]string{}
+			}
+			e[l.Port] = mcat.FromMesh
+		}
+	}
+	return e
+}
+
+// exposureOf is a module's per-node exposure, declared port to source: its expose setting, and
+// the reaches of its endpoints the proxy does not serve.
+func exposureOf(m mcat.Manifest, layers []mcat.Layer) (map[int]string, error) {
+	e, err := Exposure(m, layers)
+	if err != nil {
+		return nil, err
+	}
+	// And how far each endpoint reaches, which says the same thing to the filter and more
+	// besides (novox/hq ADR 0138). Folded in here rather than beside: the filter has one
+	// question — from where — and a reach answers it, so giving it two inputs would let them
+	// disagree. Reaches refuses a port that both name, so this cannot silently prefer one.
+	reaches, err := Reaches(m, layers)
+	if err != nil {
+		return nil, err
+	}
+	// **Only for an endpoint the proxy does not serve.** A routed endpoint's port is how the
+	// proxy reaches it and nothing else (ADR 0045), so `public` there asks for a public name and
+	// says nothing about the port — opening it to the world as well would undo the arrangement
+	// the proxy exists for, and would silently reopen a port an operator had narrowed.
+	//
+	// Found by trying to express a real module: one whose routed name must be public and whose
+	// machine-side port must not be. Under one value for both, there was no way to say it.
+	routed := RoutedPorts(m)
+	for port, reach := range reaches {
+		if routed[port] {
+			continue
+		}
+		source, ok := FilterSource(reach)
+		if !ok {
+			return nil, fmt.Errorf("%s: %q is not a reach the filter can read", m.Module, reach)
+		}
+		if e == nil {
+			e = map[int]string{}
+		}
+		e[port] = source
+	}
+	return e, nil
+}
+
 // provisionsAs is the account that reads what the mesh writes for this provider: the one secret
 // per consumer it must open to set that consumer's password (novox/hq issue 225).
 //
diff --git a/internal/compose/resolution/filtering_test.go b/internal/compose/resolution/filtering_test.go
index e8976c1..79e4e53 100644
--- a/internal/compose/resolution/filtering_test.go
+++ b/internal/compose/resolution/filtering_test.go
@@ -60,6 +60,59 @@ func TestTheModuleAskingForTheRuleSetGetsEveryModulesPorts(t *testing.T) {
 	if !strings.Contains(content, "dport 443 accept") {
 		t.Fatalf("the rule set holds only the asking module's ports:\n%s", content)
 	}
+
+	// Issue 1966, novox 2026-11-09 07:46-09:24 UTC: a module left out of the declaration for a setting its new definition
+	// no longer composes (ADR 0163 rule 6) keeps running what it ran, so the filter keeps letting it through. The
+	// artifact store's build 6e1dfaa8 listens on 5100 from a process and publishes no container port 5000, while its
+	// node layer still gave 5000 the machine port 5100: left out, and the filter closed 5100 for 98 minutes while the old
+	// registry container still served there; every build failed "dial tcp 10.10.0.1:5100: i/o timeout".
+	r.Modules = append(r.Modules, mcat.Manifest{Module: "distribution",
+		Listens: []mcat.Listening{{Name: "registry", Port: 5100, Protocol: "tcp", From: mcat.FromEverywhere}},
+		Resources: []map[string]any{{"id": "store", "type": "container", "name": "mesh-registry",
+			"image": "registry@sha256:" + strings.Repeat("a", 64), "ports": []any{"127.0.0.1:5001:5001"}}}})
+	with := mcat.Rendering{Mesh: []string{"198.51.100.2"}, OutwardLinks: []string{"eth0"}, TunnelInterface: "mesh0",
+		Settings: mcat.SettingsBy{"distribution": {{From: "novox", Placement: map[string]any{mcat.PortsSetting: map[string]any{"5000": 5100}}}}}}
+	if left := LeftOut(r, with.Settings, false); left["distribution"] == "" {
+		t.Fatalf("the stale port setting does not leave distribution out: %v", left)
+	}
+	if out, err = Declaration(r, with); err != nil {
+		t.Fatalf("declaration with a module left out: %v", err)
+	}
+	content = ""
+	for _, res := range out {
+		if res["path"] == "/etc/mesh/filter.nft" {
+			content, _ = res["content"].(string)
+		}
+	}
+	if !strings.Contains(content, "dport 5100 accept") || !strings.Contains(content, "dport 443 accept") {
+		t.Fatalf("the filter closes the port of a module left out of the declaration, which still runs:\n%s", content)
+	}
+	// Its per-node narrowing still holds (ADR 0046), and an exposure that cannot be read for it opens it no wider than
+	// the mesh, never at the manifest's default (review round 1).
+	for _, row := range []struct {
+		expose map[string]any
+		from   string
+	}{
+		{map[string]any{"5100": mcat.FromMachine}, mcat.FromMachine},
+		{map[string]any{"9999": mcat.FromMachine}, mcat.FromMesh}, // a port it does not listen on: refused
+	} {
+		layer := with.Settings["distribution"][0]
+		layer.Placement = map[string]any{mcat.PortsSetting: map[string]any{"5000": 5100}, mcat.ExposeSetting: row.expose}
+		with.Settings = mcat.SettingsBy{"distribution": {layer}}
+		rules, err := Rules(r, with)
+		if err != nil {
+			t.Fatalf("expose %v: %v", row.expose, err)
+		}
+		var from []string
+		for _, rule := range rules {
+			if rule.Port == 5100 {
+				from = append(from, rule.From)
+			}
+		}
+		if len(from) != 1 || from[0] != row.from {
+			t.Errorf("expose %v: the left-out module's 5100 opens from %v, want %s", row.expose, from, row.from)
+		}
+	}
 }
 
 // The host does not sort, so the order the mesh writes is the order a machine applies.