diff --git a/cmd/mesh-controller/adoption.go b/cmd/mesh-controller/adoption.go
index 6b9d95b..2e5bdc0 100644
--- a/cmd/mesh-controller/adoption.go
+++ b/cmd/mesh-controller/adoption.go
@@ -7,6 +7,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"net"
 	"slices"
 	"sort"
 	"strings"
@@ -309,7 +310,7 @@ func converge(ctx context.Context, open *stores, node string, yes bool, digest s
 		return "", err
 	}
 	derived := derivedFilter{rules: rules, foundation: with.Foundation, mesh: with.Mesh,
-		outward: plan.PublicDomain != ""}
+		outward: plan.PublicDomain != "", routed: with.Routed}
 	preview, saw := previewOf(node, reported, derived, plan, taken, filter, runs[filter])
 	preview += "\n\n  preview " + saw
 	if !yes {
@@ -414,6 +415,17 @@ func previewOf(node string, reported inventory.Adoption, derived derivedFilter,
 	b.WriteString("    not previewed: traffic the machine routes that is not a published port " +
 		"(a tunnel, NAT in the found firewall) — the derived filter drops it unless a module " +
 		"declares it\n")
+	// What it routes, said rather than left to the sentence above (novox/hq ADR 0137). The filter
+	// forwards the container runtime's own default pools without being told; anything else is this
+	// list, and a machine whose guests live outside those pools and names none of them loses their
+	// egress at the flip, silently, which is how this was found.
+	if len(derived.routed) > 0 {
+		b.WriteString(fmt.Sprintf("    it routes: %s — kept forwarded, and their guests keep "+
+			"address and name service\n", strings.Join(derived.routed, ", ")))
+	} else {
+		b.WriteString("    it routes: nothing said, so only the container runtime's own default " +
+			"pools are forwarded — `node networks <node> <cidr>...` if its guests live elsewhere\n")
+	}
 
 	isTaken := map[string]bool{}
 	for _, m := range taken {
@@ -473,6 +485,9 @@ type derivedFilter struct {
 	// mesh is every address on the private network; outward says the machine faces outside.
 	mesh    []string
 	outward bool
+	// routed is the networks this machine says it routes for what it hosts (novox/hq ADR 0137):
+	// their guests keep address and name service, and what they send onward keeps being forwarded.
+	routed []string
 }
 
 // closesOutside is what a narrowing from everywhere to the private network is called: it closes.
@@ -498,6 +513,13 @@ func (d derivedFilter) fate(r inventory.Reach) string {
 			return "stays open — the mesh's own, from anywhere"
 		}
 	}
+	// A guest on a network this machine routes asks it for an address and for names, and those two
+	// arrive here (novox/hq ADR 0137). Matched on the listener's own address: a resolver bound to a
+	// bridge in one of those networks is the one its guests ask.
+	if within(r.Address, d.routed) &&
+		((r.Protocol == "udp" && (r.Port == 53 || r.Port == 67)) || (r.Protocol == "tcp" && r.Port == 53)) {
+		return "stays open — address and name service for a network this machine routes"
+	}
 	for _, rule := range d.rules {
 		if rule.Port != r.Port || rule.Protocol != r.Protocol {
 			continue
@@ -520,6 +542,24 @@ func (d derivedFilter) fate(r inventory.Reach) string {
 	return "WILL CLOSE — no module assigned here declares it"
 }
 
+// within says whether an address the machine reported sits inside one of the networks it routes.
+func within(address string, networks []string) bool {
+	ip := net.ParseIP(strings.Trim(address, "[]"))
+	if ip == nil {
+		return false
+	}
+	for _, n := range networks {
+		_, block, err := net.ParseCIDR(n)
+		if err != nil {
+			continue
+		}
+		if block.Contains(ip) {
+			return true
+		}
+	}
+	return false
+}
+
 // countReachable is how much of a node's account of itself names something off the machine.
 // Loopback is left out for the same reason the preview leaves it out: nothing outside reaches it,
 // so a report of loopback alone says nothing about what the filter would close.
diff --git a/cmd/mesh-controller/main.go b/cmd/mesh-controller/main.go
index 28d52a1..6b0f312 100644
--- a/cmd/mesh-controller/main.go
+++ b/cmd/mesh-controller/main.go
@@ -148,6 +148,9 @@ func usage() {
   node public-domain <name>      the domain it composes its routed names under
   node public-domain <name> <d>  ...set it to d
   node public-domain <name> --clear   ...it faces the outside no longer
+  node networks <name>           the networks it routes for what it hosts
+  node networks <name> <cidr>... ...set them; its filter forwards these too
+  node networks <name> --clear   ...only the container runtime's own
   token issue --node <name>      a one-time right to join, for an existing record
   token issue --new <name>       create the record and issue for it
   token issue ... --adopted      ...for a machine in use, which joins adopted
diff --git a/cmd/mesh-controller/nodes.go b/cmd/mesh-controller/nodes.go
index 6f54179..59aa7b8 100644
--- a/cmd/mesh-controller/nodes.go
+++ b/cmd/mesh-controller/nodes.go
@@ -21,7 +21,8 @@ import (
 
 func nodeCommand(ctx context.Context, args []string) error {
 	if len(args) == 0 {
-		return errors.New("node add <name>, node list, node show <name>, or " + publicDomainUsage)
+		return errors.New("node add <name>, node list, node show <name>, " + publicDomainUsage +
+			", or " + networksUsage)
 	}
 	open, err := openStores(ctx)
 	if err != nil {
@@ -66,6 +67,12 @@ func nodeCommand(ctx context.Context, args []string) error {
 		// because the damage is already done by the time it prints.
 		return publicDomain(ctx, inv, args[1:])
 
+	case "networks":
+		// The networks this machine routes for what it hosts (novox/hq ADR 0137): what the derived
+		// filter must keep forwarding, beyond the container runtime's own default pools which it
+		// allows without being told. Reports with no argument, for the same reason the domain does.
+		return nodeNetworks(ctx, inv, args[1:])
+
 	case "account":
 		// The operator's login on this machine (novox/hq to-be 29): what a home-scoped file is
 		// owned by and which account `ssh <node>` uses. Reports with no argument; sets with one;
@@ -144,6 +151,67 @@ func nodeAccount(ctx context.Context, inv *inventory.Inventory, positionals []st
 	return nil
 }
 
+const networksUsage = "node networks <name> — what it routes now; " +
+	"<name> <cidr>... to set them; <name> --clear to route only the container runtime's own"
+
+// nodeNetworks reads, sets or clears the networks a machine routes for what it hosts.
+//
+// The same three forms as the domain above, and the read-shaped one reports rather than clearing,
+// for the same reason: this list is what keeps a machine's guests reaching anything, and losing it
+// by asking a question is not a mistake anybody can see afterwards.
+func nodeNetworks(ctx context.Context, inv *inventory.Inventory, args []string) error {
+	set := flag.NewFlagSet("node networks", flag.ContinueOnError)
+	clear := set.Bool("clear", false,
+		"route only the container runtime's own default pools, as a machine that has said nothing does")
+	positionals, err := parseAround(set, args)
+	if err != nil {
+		return err
+	}
+	if len(positionals) == 0 {
+		return errors.New(networksUsage)
+	}
+	node := positionals[0]
+
+	switch {
+	case *clear && len(positionals) > 1:
+		return fmt.Errorf("give %s networks or --clear, not both: %q and --clear say opposite "+
+			"things and the mesh will not choose between them", node, strings.Join(positionals[1:], " "))
+
+	case *clear:
+		if err := inv.SetRoutedNetworks(ctx, node, nil); err != nil {
+			return err
+		}
+		fmt.Printf("%s routes only the container runtime's own default pools\n", node)
+		fmt.Printf("  run `push %s` to send its filter\n", node)
+		return nil
+
+	case len(positionals) > 1:
+		if err := inv.SetRoutedNetworks(ctx, node, positionals[1:]); err != nil {
+			return err
+		}
+		fmt.Printf("%s routes %s\n", node, strings.Join(positionals[1:], ", "))
+		fmt.Printf("  its filter forwards them, and their guests keep address and name service\n")
+		fmt.Printf("  run `push %s` to send it\n", node)
+		return nil
+
+	default:
+		if _, err := inv.NodeByName(ctx, node); err != nil {
+			return err
+		}
+		networks, err := inv.RoutedNetworksOf(ctx, node)
+		if err != nil {
+			return err
+		}
+		if len(networks) == 0 {
+			fmt.Printf("%s routes only the container runtime's own default pools\n", node)
+			fmt.Printf("  `node networks %s <cidr>...` if its guests live elsewhere\n", node)
+			return nil
+		}
+		fmt.Printf("%s routes %s\n", node, strings.Join(networks, ", "))
+		return nil
+	}
+}
+
 const publicDomainUsage = "node public-domain <name> — what it is now; " +
 	"<name> <domain> to set it; <name> --clear to take it away"
 
diff --git a/cmd/mesh-controller/plan.go b/cmd/mesh-controller/plan.go
index 0280117..a70a29f 100644
--- a/cmd/mesh-controller/plan.go
+++ b/cmd/mesh-controller/plan.go
@@ -640,13 +640,19 @@ func renderingFor(ctx context.Context, open *stores, node string,
 	if err != nil {
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}
+	// The networks this machine routes for what it hosts, which the derived filter must forward for
+	// (novox/hq ADR 0137).
+	routed, err := inv.RoutedNetworksOf(ctx, node)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}
 	return catalogue.Rendering{
 		BusMembership: memberships[node],
 		Settings:      settings, Generators: gens, Grants: grants, Needed: needed, Ports: ports,
 		Certificate: certificate, Authority: authority, Mesh: private, Names: names,
 		Machines: machines,
 		Suffix:   overlay.Suffix(), MeshRange: meshRange, Accounts: accounts, Foundation: foundation,
-		Kept: kept, Adopted: record.Adopted,
+		Kept: kept, Adopted: record.Adopted, Routed: routed,
 		Given: given, Taken: taken, Seats: seats, ArtifactStore: artifactStore, Built: built,
 		BusUsers: busUsers,
 	}, record, nil
diff --git a/internal/catalogue/declaration.go b/internal/catalogue/declaration.go
index a592599..6a44726 100644
--- a/internal/catalogue/declaration.go
+++ b/internal/catalogue/declaration.go
@@ -124,6 +124,11 @@ type Rendering struct {
 	// nothing on this node keeps them, or the mesh has no operator key.
 	Kept *KeptExport
 
+	// Routed is the networks this machine routes for what it hosts, beyond the container runtime's
+	// own default pools, which the filter allows without being told (novox/hq ADR 0137). A node-level
+	// fact: the machine routes them, and the module that loads the filter may be replaced.
+	Routed []string
+
 	// Foundation is the ports the mesh itself needs reachable on every machine, which no module
 	// declares because the foundation is not a module (novox/hq 04-ISSUES/051 and 052). The broker
 	// is the one that matters: a machine dials it to enrol, and a firewall derived only from
@@ -345,7 +350,7 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 	if err != nil {
 		return nil, err
 	}
-	filtering := AsNftables(rules, with.Mesh, r.PublicDomain != "", with.Foundation)
+	filtering := AsNftables(rules, with.Mesh, r.PublicDomain != "", with.Foundation, with.Routed)
 
 	var out []map[string]any
 	for _, m := range r.Modules {
diff --git a/internal/catalogue/filtering.go b/internal/catalogue/filtering.go
index fd3c78f..bd61b40 100644
--- a/internal/catalogue/filtering.go
+++ b/internal/catalogue/filtering.go
@@ -230,7 +230,7 @@ const SSHPort = 22
 // It is a floor for the same reason ssh is. A machine nobody can reach is a machine nobody can
 // repair; a machine the mesh cannot reach is a machine the mesh cannot manage. Neither is a thing
 // any module asks for, and neither may be derived away.
-func AsNftables(rules []Rule, mesh []string, outward bool, foundation []int) string {
+func AsNftables(rules []Rule, mesh []string, outward bool, foundation []int, routed []string) string {
 	var b strings.Builder
 	b.WriteString("# Computed by the mesh from what is assigned to this node.\n")
 	b.WriteString("# Edits are lost on the next declaration; change a module's listens instead.\n\n")
@@ -252,6 +252,21 @@ func AsNftables(rules []Rule, mesh []string, outward bool, foundation []int) str
 	b.WriteString("\t\ticmp type echo-request accept\n")
 	b.WriteString("\t\ticmpv6 type { echo-request, nd-neighbor-solicit, nd-neighbor-advert, nd-router-advert } accept\n")
 
+	// **What a machine it routes for must be able to ask it** (novox/hq ADR 0137). A guest on one of
+	// these networks gets its address and its names from this machine, over the bridge it is on, and
+	// those two questions arrive at the input chain like any other. Denied, the guest never gets an
+	// address and never resolves a name — which is not "a closed port" but a network that does not
+	// work at all, and it is this machine's own guest asking.
+	//
+	// Only these ports, and only for a network that was named: everything else a guest might want
+	// from its host is a port somebody declares, like every other port on this machine.
+	for _, network := range routed {
+		family := saddrFamily(network)
+		b.WriteString("\t\t# address and name service for a network this machine routes\n")
+		b.WriteString(fmt.Sprintf("\t\t%s saddr %s udp dport { 53, 67 } accept\n", family, network))
+		b.WriteString(fmt.Sprintf("\t\t%s saddr %s tcp dport 53 accept\n", family, network))
+	}
+
 	// **ssh, always, and not because a module asked.**
 	//
 	// Every other line in this chain is derived from what is assigned here, which is the whole
@@ -375,6 +390,13 @@ func AsNftables(rules []Rule, mesh []string, outward bool, foundation []int) str
 		b.WriteString(fmt.Sprintf("\t\t# %s\n", network.why))
 		b.WriteString(fmt.Sprintf("\t\tip saddr %s accept\n", network.cidr))
 	}
+	// And what this machine says it routes beyond them (novox/hq ADR 0137). Added to the defaults
+	// above, never replacing them: a machine that names one range has not stopped hosting whatever
+	// was already on the runtime's own.
+	for _, network := range routed {
+		b.WriteString("\t\t# a network this machine routes for what it hosts\n")
+		b.WriteString(fmt.Sprintf("\t\t%s saddr %s accept\n", saddrFamily(network), network))
+	}
 
 	if len(rules) > 0 {
 		b.WriteString("\n")
@@ -442,6 +464,16 @@ var runtimeNetworks = []struct{ cidr, why string }{
 	{"192.168.128.0/17", "the networks its compose files are given"},
 }
 
+// saddrFamily is the match a network's family is written with: `ip saddr` or `ip6 saddr`. One match
+// for both families is a syntax error, and a ruleset that does not load is a machine filtering
+// nothing while its service reports a fault — the same reason byFamily below exists.
+func saddrFamily(network string) string {
+	if strings.Contains(network, ":") {
+		return "ip6"
+	}
+	return "ip"
+}
+
 // byFamily splits addresses into the two nftables understands separately.
 //
 // `ip saddr` and `ip6 saddr` are different matches, and one set holding both families is a syntax
diff --git a/internal/catalogue/filtering_foundation_test.go b/internal/catalogue/filtering_foundation_test.go
index c98da09..fb53cf3 100644
--- a/internal/catalogue/filtering_foundation_test.go
+++ b/internal/catalogue/filtering_foundation_test.go
@@ -19,7 +19,7 @@ func TestTheBrokersPortIsOpenedThoughNoModuleDeclaresIt(t *testing.T) {
 	// A machine on the private network, with one ordinary module rule, and nothing that mentions
 	// the broker — which is every machine.
 	rules := []Rule{{Port: 8080, From: FromMesh, Because: []string{"some-module"}}}
-	out := AsNftables(rules, []string{"10.42.0.1"}, false, []int{brokerPort})
+	out := AsNftables(rules, []string{"10.42.0.1"}, false, []int{brokerPort}, nil)
 
 	if !strings.Contains(out, "tcp dport 5671 accept") {
 		t.Fatalf("the broker's port is not opened, so no machine could enrol:\n%s", out)
@@ -48,7 +48,7 @@ func TestTheBrokersPortIsOpenedThoughNoModuleDeclaresIt(t *testing.T) {
 // And a mesh that was never told about a broker still gets a ruleset, rather than an empty one or
 // a panic. A control plane in that state cannot issue tokens either, which is where it surfaces.
 func TestNoBrokerMeansNoFoundationRuleRatherThanNoRuleset(t *testing.T) {
-	out := AsNftables(nil, []string{"10.42.0.1"}, false, nil)
+	out := AsNftables(nil, []string{"10.42.0.1"}, false, nil, nil)
 	if !strings.Contains(out, "table inet mesh") {
 		t.Fatalf("no ruleset at all:\n%s", out)
 	}
diff --git a/internal/catalogue/filtering_routed_test.go b/internal/catalogue/filtering_routed_test.go
new file mode 100644
index 0000000..98dc618
--- /dev/null
+++ b/internal/catalogue/filtering_routed_test.go
@@ -0,0 +1,99 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// A machine's own guests keep working when the filter it is given denies by default.
+//
+// **The forward chain allowed the container runtime's two default pools and nothing else** — named
+// in this package's code with a comment saying a machine configured otherwise "needs this to say
+// so", and no way to say it (novox/hq ADR 0137). Measured on a workstation on 2026-09-28: the flip
+// to the derived filter cut egress for five of its container networks, allocated from ranges those
+// two defaults do not cover, and for every network its test beds create. Nothing reported a fault.
+// The guests simply could not reach anything, and the machine went on saying it had applied what it
+// was told.
+func TestWhatAMachineSaysItRoutesKeepsBeingForwarded(t *testing.T) {
+	const beds = "10.0.0.0/8"
+
+	ruleset := AsNftables(nil, []string{"10.10.0.1"}, false, nil, []string{beds})
+
+	forward := chainOf(t, ruleset, "forward")
+	if !strings.Contains(forward, "ip saddr "+beds+" accept") {
+		t.Errorf("the forward chain does not accept what the machine says it routes (%s):\n%s",
+			beds, forward)
+	}
+	// The defaults stay. A machine that names one range has not stopped hosting whatever was
+	// already on the runtime's own pools, and losing those would trade one silent breakage for
+	// another.
+	for _, network := range runtimeNetworks {
+		if !strings.Contains(forward, "ip saddr "+network.cidr+" accept") {
+			t.Errorf("naming a network dropped the runtime's own %s:\n%s", network.cidr, forward)
+		}
+	}
+
+	// And its guests can still ask this machine the two questions that make a network usable at
+	// all: what is my address, and what is that name.
+	input := chainOf(t, ruleset, "input")
+	for _, want := range []string{
+		"ip saddr " + beds + " udp dport { 53, 67 } accept",
+		"ip saddr " + beds + " tcp dport 53 accept",
+	} {
+		if !strings.Contains(input, want) {
+			t.Errorf("the input chain is missing %q, so a guest on %s gets no address and "+
+				"resolves no name:\n%s", want, beds, input)
+		}
+	}
+}
+
+// A machine that says nothing is filtered exactly as it was before this existed.
+//
+// The change has to be additive on every machine already converged: novox has been carrying this
+// mesh's public services behind the derived filter for weeks, and a new line in its ruleset is a
+// change to a production firewall nobody asked for.
+func TestAMachineThatNamesNoNetworksIsFilteredAsBefore(t *testing.T) {
+	rules := []Rule{{Port: 443, Protocol: "tcp", From: FromEverywhere, Because: []string{"proxy"}}}
+
+	said := AsNftables(rules, []string{"10.10.0.1"}, true, []int{4222}, nil)
+	quiet := AsNftables(rules, []string{"10.10.0.1"}, true, []int{4222}, []string{})
+
+	if said != quiet {
+		t.Errorf("nil and empty render differently:\n%s\n---\n%s", said, quiet)
+	}
+	if strings.Contains(said, "a network this machine routes") {
+		t.Errorf("a machine that named nothing carries a line about what it routes:\n%s", said)
+	}
+}
+
+// The two families are matched differently, and one set holding both is a syntax error — a ruleset
+// that does not load is a machine filtering nothing while its unit reports a fault.
+func TestARoutedNetworkIsMatchedInItsOwnFamily(t *testing.T) {
+	ruleset := AsNftables(nil, nil, false, nil, []string{"10.0.0.0/8", "fd00::/8"})
+
+	if !strings.Contains(ruleset, "ip saddr 10.0.0.0/8 accept") {
+		t.Errorf("the v4 network is not matched as ip saddr:\n%s", ruleset)
+	}
+	if !strings.Contains(ruleset, "ip6 saddr fd00::/8 accept") {
+		t.Errorf("the v6 network is not matched as ip6 saddr:\n%s", ruleset)
+	}
+	if strings.Contains(ruleset, "ip saddr fd00::/8") {
+		t.Errorf("a v6 network is matched as ip saddr, which nftables refuses:\n%s", ruleset)
+	}
+}
+
+// chainOf is one chain's body, so a test about the forward chain cannot pass on a line in the input
+// chain that happens to look the same.
+func chainOf(t *testing.T, ruleset, name string) string {
+	t.Helper()
+	start := strings.Index(ruleset, "chain "+name+" {")
+	if start < 0 {
+		t.Fatalf("no chain %q in:\n%s", name, ruleset)
+	}
+	rest := ruleset[start:]
+	end := strings.Index(rest, "\n\t}")
+	if end < 0 {
+		t.Fatalf("chain %q does not end:\n%s", name, rest)
+	}
+	return rest[:end]
+}
diff --git a/internal/catalogue/filtering_test.go b/internal/catalogue/filtering_test.go
index 22a4e3f..00e3040 100644
--- a/internal/catalogue/filtering_test.go
+++ b/internal/catalogue/filtering_test.go
@@ -79,7 +79,7 @@ func TestTwoModulesWantingOnePortAreBothNamed(t *testing.T) {
 		t.Fatalf("a module that wanted this port open is not named: %+v", rules[0])
 	}
 	// The consequence, which is the reason this matters: removing web must not read as closing 443.
-	nft := AsNftables(rules, nil, false, nil)
+	nft := AsNftables(rules, nil, false, nil, nil)
 	if !strings.Contains(nft, "web") || !strings.Contains(nft, "board") {
 		t.Fatalf("the rendered rule set does not name both sources:\n%s", nft)
 	}
@@ -107,7 +107,7 @@ func TestAPortOpenToEveryoneIsNotAlsoRestrictedToTheMesh(t *testing.T) {
 func TestWhatNoModuleDeclaredIsClosed(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "web", Listens: []Listening{{Port: 443, From: FromEverywhere}}},
-	}}, nil), []string{"198.51.100.2"}, false, nil)
+	}}, nil), []string{"198.51.100.2"}, false, nil, nil)
 	// Naming the chain, not just the policy: the forward chain drops too, and an assertion on
 	// "policy drop" alone passes while the input chain accepts everything. It did, once, here.
 	if !strings.Contains(nft, "type filter hook input priority filter; policy drop;") {
@@ -134,7 +134,7 @@ func TestWhatNoModuleDeclaredIsClosed(t *testing.T) {
 // `flush ruleset` would do the first and not the second: it empties every table on the machine,
 // including the ones the container runtime writes for its bridges.
 func TestReloadingReplacesOnlyTheMeshsOwnRules(t *testing.T) {
-	nft := AsNftables(nil, nil, false, nil)
+	nft := AsNftables(nil, nil, false, nil, nil)
 	if strings.Contains(nft, "flush ruleset") {
 		t.Fatalf("loading the rule set empties every table on the machine:\n%s", nft)
 	}
@@ -160,7 +160,7 @@ func TestReloadingReplacesOnlyTheMeshsOwnRules(t *testing.T) {
 // So the chain exists and denies by default, and the runtime's own networks are allowed explicitly
 // — which is how the system being replaced has been doing it on these machines for months.
 func TestWhatIsForwardedIsGovernedToo(t *testing.T) {
-	nft := AsNftables(nil, []string{"198.51.100.2"}, false, nil)
+	nft := AsNftables(nil, []string{"198.51.100.2"}, false, nil, nil)
 	if !strings.Contains(nft, "hook forward priority filter; policy drop") {
 		t.Fatalf("forwarded traffic is not governed, so container ports are open:\n%s", nft)
 	}
@@ -168,7 +168,7 @@ func TestWhatIsForwardedIsGovernedToo(t *testing.T) {
 
 // And containers keep working, which is the whole reason the chain was left out before.
 func TestTheRuntimesOwnNetworksKeepWorking(t *testing.T) {
-	nft := AsNftables(nil, []string{"198.51.100.2"}, false, nil)
+	nft := AsNftables(nil, []string{"198.51.100.2"}, false, nil, nil)
 	for _, network := range []string{"172.16.0.0/12", "192.168.128.0/17"} {
 		if !strings.Contains(nft, "ip saddr "+network+" accept") {
 			t.Fatalf("%s is not allowed, so denying by default stops every container:\n%s", network, nft)
@@ -183,7 +183,7 @@ func TestTheRuntimesOwnNetworksKeepWorking(t *testing.T) {
 func TestAPublishedPortIsMatchedByWhatWasAskedFor(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "web", Listens: []Listening{{Port: 8080, From: FromEverywhere}}},
-	}}, nil), []string{"198.51.100.2"}, false, nil)
+	}}, nil), []string{"198.51.100.2"}, false, nil, nil)
 	if !strings.Contains(nft, "ct original proto-dst 8080 accept") {
 		t.Fatalf("the forwarded rule does not match the port a client asked for:\n%s", nft)
 	}
@@ -193,7 +193,7 @@ func TestAPublishedPortIsMatchedByWhatWasAskedFor(t *testing.T) {
 func TestAMeshScopedPortIsMeshScopedWhenForwarded(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "store", Listens: []Listening{{Port: 5432, From: FromMesh}}},
-	}}, nil), []string{"198.51.100.2"}, false, nil)
+	}}, nil), []string{"198.51.100.2"}, false, nil, nil)
 	if !strings.Contains(nft, "ip saddr { 198.51.100.2 } ct original proto-dst 5432 accept") {
 		t.Fatalf("a mesh-only port is reachable from anywhere once forwarded:\n%s", nft)
 	}
@@ -203,7 +203,7 @@ func TestAMeshScopedPortIsMeshScopedWhenForwarded(t *testing.T) {
 func TestFromTheMeshIsTheNodesTheMeshKnows(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "store", Listens: []Listening{{Port: 5432, From: FromMesh}}},
-	}}, nil), []string{"198.51.100.2", "198.51.100.3"}, false, nil)
+	}}, nil), []string{"198.51.100.2", "198.51.100.3"}, false, nil, nil)
 	if !strings.Contains(nft, "ip saddr { 198.51.100.2, 198.51.100.3 } tcp dport 5432 accept") {
 		t.Fatalf("a mesh-scoped port was not restricted to the mesh's addresses:\n%s", nft)
 	}
@@ -213,7 +213,7 @@ func TestFromTheMeshIsTheNodesTheMeshKnows(t *testing.T) {
 func TestAMeshPortOnANodeWithNoMeshIsClosedAndSaysSo(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "store", Listens: []Listening{{Port: 5432, From: FromMesh}}},
-	}}, nil), nil, false, nil)
+	}}, nil), nil, false, nil, nil)
 	if strings.Contains(nft, "dport 5432 accept") {
 		t.Fatalf("a port meant for the mesh was opened to everything:\n%s", nft)
 	}
@@ -226,7 +226,7 @@ func TestAMeshPortOnANodeWithNoMeshIsClosedAndSaysSo(t *testing.T) {
 func TestAMachineScopedPortIsNotOpened(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "cache", Listens: []Listening{{Port: 6379, From: FromMachine}}},
-	}}, nil), []string{"198.51.100.2"}, false, nil)
+	}}, nil), []string{"198.51.100.2"}, false, nil, nil)
 	if strings.Contains(nft, "dport 6379 accept") {
 		t.Fatalf("a port for this machine only was opened to the network:\n%s", nft)
 	}
@@ -268,7 +268,7 @@ func TestAskingForTheRuleSetWithNowhereToPutItIsRefused(t *testing.T) {
 func TestAMeshOnBothAddressFamiliesRendersBoth(t *testing.T) {
 	nft := AsNftables(mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "store", Listens: []Listening{{Port: 5432, From: FromMesh}}},
-	}}, nil), []string{"198.51.100.2", "2001:db8::2"}, false, nil)
+	}}, nil), []string{"198.51.100.2", "2001:db8::2"}, false, nil, nil)
 	if !strings.Contains(nft, "ip saddr { 198.51.100.2 } tcp dport 5432 accept") {
 		t.Fatalf("the machines with v4 addresses were dropped:\n%s", nft)
 	}
@@ -672,7 +672,7 @@ func TestExposureRefusesAPortNotListenedOnAndABadSource(t *testing.T) {
 // loading the rules lives on conntrack until it drops, and then the machine is reached from a
 // rescue console (novox/hq issue 047).
 func TestSSHIsOpenFromTheMeshEvenWhenNothingIsAssigned(t *testing.T) {
-	nft := AsNftables(nil, []string{"198.51.100.2", "198.51.100.3"}, false, nil)
+	nft := AsNftables(nil, []string{"198.51.100.2", "198.51.100.3"}, false, nil, nil)
 	if !strings.Contains(nft, "ip saddr { 198.51.100.2, 198.51.100.3 } tcp dport 22 accept") {
 		t.Fatalf("ssh is not open to the mesh, so a machine can lock everyone out:\n%s", nft)
 	}
@@ -685,7 +685,7 @@ func TestSSHIsOpenFromTheMeshEvenWhenNothingIsAssigned(t *testing.T) {
 // And from outside as well, on a machine that faces outward — because that is the way in when the
 // private network is the thing that broke.
 func TestSSHIsOpenFromOutsideOnAMachineThatFacesIt(t *testing.T) {
-	nft := AsNftables(nil, []string{"198.51.100.2"}, true, nil)
+	nft := AsNftables(nil, []string{"198.51.100.2"}, true, nil, nil)
 	if !strings.Contains(nft, "\t\ttcp dport 22 accept") {
 		t.Fatalf("a machine reachable from outside does not answer ssh there:\n%s", nft)
 	}
@@ -697,7 +697,7 @@ func TestSSHIsOpenFromOutsideOnAMachineThatFacesIt(t *testing.T) {
 // to narrow the rule to, so narrowing it shuts the port entirely — on the first machine anybody
 // adopts, reached over the network, closed by the act of adopting it.
 func TestSSHIsNeverLeftWithoutARule(t *testing.T) {
-	nft := AsNftables(nil, nil, false, nil)
+	nft := AsNftables(nil, nil, false, nil, nil)
 	if !strings.Contains(nft, "tcp dport 22 accept") {
 		t.Fatalf("a machine with no mesh addresses has no ssh rule, so adopting it locks it:\n%s", nft)
 	}
diff --git a/internal/catalogue/print_rehearsal_test.go b/internal/catalogue/print_rehearsal_test.go
index 65fbb58..c136ab2 100644
--- a/internal/catalogue/print_rehearsal_test.go
+++ b/internal/catalogue/print_rehearsal_test.go
@@ -12,5 +12,5 @@ func TestPrintRehearsalRuleset(t *testing.T) {
 	rules := mustFilter(t, Resolution{Modules: []Manifest{
 		{Module: "pub", Listens: []Listening{{Port: 8099, From: FromMesh, Why: "the thing it serves"}}},
 	}}, nil)
-	t.Log("\n" + AsNftables(rules, []string{"192.0.2.20"}, true, nil))
+	t.Log("\n" + AsNftables(rules, []string{"192.0.2.20"}, true, nil, nil))
 }
diff --git a/internal/inventory/migrations/0043-a-machine-says-which-networks-it-routes.sql b/internal/inventory/migrations/0043-a-machine-says-which-networks-it-routes.sql
new file mode 100644
index 0000000..4372efa
--- /dev/null
+++ b/internal/inventory/migrations/0043-a-machine-says-which-networks-it-routes.sql
@@ -0,0 +1,19 @@
+-- The networks a machine routes for what it hosts, beyond the container runtime's own defaults.
+--
+-- novox/hq ADR 0137. The derived packet filter denies forwarding by default and then allows the
+-- container runtime's two default pools, named in the controller's code with a comment saying that
+-- a machine configured otherwise "needs this to say so" — and no way to say it. So the filter was
+-- correct only on a machine whose runtime used the defaults, and silently wrong on any other.
+--
+-- Measured on 2026-09-28: flipping a workstation to the derived filter cut egress for five of its
+-- container networks and for every network its test beds create, because those are allocated from
+-- ranges the two defaults do not cover. Nothing reported a fault; the containers simply could not
+-- reach anything.
+--
+-- A node-level fact, beside the node's public domain and for the same reason: it is a property of
+-- the machine, not of whichever module happens to load the filter today. Swapping that module must
+-- not lose it.
+--
+-- Null for a machine that routes nothing but the runtime's defaults, which is the ordinary case and
+-- what every machine held before this column existed.
+alter table node add column routed_networks jsonb;
diff --git a/internal/inventory/nodes.go b/internal/inventory/nodes.go
index b0d52b8..c166a94 100644
--- a/internal/inventory/nodes.go
+++ b/internal/inventory/nodes.go
@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"net"
 	"sort"
 	"strings"
 	"time"
@@ -518,6 +519,69 @@ func (i *Inventory) PublicDomainOf(ctx context.Context, name string) (string, er
 	return *domain, nil
 }
 
+// SetRoutedNetworks records the networks this machine routes for what it hosts, beyond the
+// container runtime's own default pools.
+//
+// A node-level fact (novox/hq ADR 0137), beside the node's public domain: the machine routes them,
+// not whichever module loads the filter, so swapping that module must not lose them. Added to the
+// runtime's defaults rather than replacing them, so a machine that says one range does not lose the
+// ranges its containers were already using. An empty list clears it.
+//
+// Each entry is checked as a CIDR here rather than at render time: an address that does not parse
+// becomes a line nftables refuses, and a refused ruleset is a machine that filters nothing while
+// its service reports a configuration fault.
+func (i *Inventory) SetRoutedNetworks(ctx context.Context, name string, networks []string) error {
+	node, err := i.NodeByName(ctx, name)
+	if err != nil {
+		return err
+	}
+	var kept []string
+	for _, n := range networks {
+		n = strings.TrimSpace(n)
+		if n == "" {
+			continue
+		}
+		if _, _, err := net.ParseCIDR(n); err != nil {
+			return fmt.Errorf("%q is not a network in CIDR form (10.0.0.0/8, 192.168.0.0/16): %w",
+				n, err)
+		}
+		kept = append(kept, n)
+	}
+	if len(kept) == 0 {
+		_, err = i.store.Pool().Exec(ctx,
+			`update node set routed_networks = null where id = $1`, node.ID)
+		return err
+	}
+	body, err := json.Marshal(kept)
+	if err != nil {
+		return err
+	}
+	_, err = i.store.Pool().Exec(ctx,
+		`update node set routed_networks = $2 where id = $1`, node.ID, string(body))
+	return err
+}
+
+// RoutedNetworksOf is the networks a machine routes for what it hosts, empty when it has named none.
+func (i *Inventory) RoutedNetworksOf(ctx context.Context, name string) ([]string, error) {
+	var body []byte
+	err := i.store.Pool().QueryRow(ctx,
+		`select routed_networks from node where name = $1`, name).Scan(&body)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, fmt.Errorf("%w: %s", ErrNoSuchNode, name)
+	}
+	if err != nil {
+		return nil, err
+	}
+	if len(body) == 0 {
+		return nil, nil
+	}
+	var networks []string
+	if err := json.Unmarshal(body, &networks); err != nil {
+		return nil, fmt.Errorf("the networks recorded for %s are not a list: %w", name, err)
+	}
+	return networks, nil
+}
+
 // RecordOverlayKey keeps the public half a node generated.
 func (i *Inventory) RecordOverlayKey(ctx context.Context, node, key string) error {
 	if strings.TrimSpace(key) == "" {