An older merge does not move a source

The forge announces what it finds merged, and an old merge surfacing late moved the recorded head backwards and rebuilt everything built from that repository, once per old merge. A merge made before the source was last seen is history; one that says nothing about when is taken as news. The catalogue now carries when each source was last seen. The bus-records test follows #116: a module's tools are every one under its own name.
Merge pull request 'A module hears what it consumes: its consumer is raised with the bus, and it pulls it' (#118 ) from fix/a-module-hears-what-it-consumes into main
2026-09-28 05:12:37 +02:00 · 2026-09-28 02:29:34 +00:00 · 2026-09-28 04:29:32 +02:00 · 2026-09-28 02:21:26 +00:00 · 2026-09-28 04:21:25 +02:00 · 2026-09-28 02:14:52 +00:00
133 changed files with 12562 additions and 2283 deletions
@@ -86,13 +86,19 @@ proxy-image:

 # The whole gate. Raises a database, runs everything against it, and takes it down again --
 # including when the tests fail, which is why the teardown is not conditional.
+#
+# **One package at a time (-p 1), and it is not about speed.** The live tests reach one bus, and on
+# it they assert, read and remove the mesh's own objects -- streams and consumers with fixed names,
+# because those names are the mesh's and a test cannot choose others. Two packages doing that at once
+# is one deleting a consumer the other is reading through, and the failure lands in whichever test
+# was reading, as "no response from stream". That reads as a bug in the code under test.
 check: fmt vet postgres
-	@go test ./... ; status=$$? ; $(MAKE) postgres-stop ; exit $$status
+	@go test -p 1 ./... ; status=$$? ; $(MAKE) postgres-stop ; exit $$status

 # Without a database the live tests skip rather than fail, so this is the honest subset and not
-# the gate.
+# the gate. Serialised for the same reason check is: a bus may be configured even when a store is not.
 test:
-	go test ./...
+	go test -p 1 ./...

 vet:
 	go vet ./...
@@ -17,22 +17,15 @@ package main

 import (
 	"context"
-	"crypto/sha256"
-	"crypto/tls"
-	"crypto/x509"
-	"encoding/hex"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"net/url"
 	"os"
 	"os/signal"
 	"strings"
 	"syscall"
-	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"

+	"github.com/novox/mesh-controller/internal/broker"
 	"github.com/novox/mesh-controller/internal/builder"
 	"github.com/novox/mesh-controller/internal/link"
 )
@@ -52,7 +45,6 @@ const usage = `mesh-builder — builds modules for the mesh
 It consumes build requests and answers with what it made. Nothing is listened on and nothing
 is dialled except the broker.

-  MESH_BROKER_AMQP   where the broker is, with this builder's own credential
  MESH_BROKER_FILE   a file the mesh sealed to this machine holding the same
  MESH_REGISTRY      host:port to publish artifacts to, when the mesh has not said
  MESH_BINDING       a file the mesh wrote saying where the artifact store is
@@ -115,72 +107,48 @@ func run() error {
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()

-	conn, err := dial(credential)
-	if err != nil {
-		// Not quoted back: the URL carries this builder's broker password.
-		return fmt.Errorf("cannot reach the broker: %w", err)
-	}
-	defer conn.Close()
-	channel, err := conn.Channel()
-	if err != nil {
-		return err
-	}
-	defer channel.Close()
-
-	if _, err := channel.QueueDeclare(link.BuildQueue, true, false, false, false, nil); err != nil {
-		return err
-	}
-	// One at a time. A build machine that took five requests at once would run five container
-	// builds against one runtime and finish all of them slower than it would have finished the
-	// first — and the queue is what shares work between machines, so nothing is lost by it.
-	if err := channel.Qos(1, 0, false); err != nil {
-		return err
-	}
-
-	// Not auto-acknowledged. A request acknowledged on arrival is a build that vanishes if this
-	// process dies mid-way, with nobody waiting on it ever hearing why.
-	requests, err := channel.ConsumeWithContext(ctx, link.BuildQueue, "mesh-builder",
-		false, false, false, false, nil)
+	machine, err := takeWorkFrom(credential, on)
 	if err != nil {
 		return err
 	}
+	defer machine.Close()

 	fmt.Fprintf(os.Stderr, "building for the mesh, publishing to %s\n", registry)
 	publisher := builder.Registry{Address: registry, Run: builder.Command}

-	for {
-		select {
-		case <-ctx.Done():
-			fmt.Println("stopping")
-			return nil
-		case delivery, ok := <-requests:
-			if !ok {
-				return fmt.Errorf("the broker closed the connection")
-			}
-			answer(ctx, channel, publisher, on, workspace, delivery)
-		}
+	return machine.Take(ctx, func(ctx context.Context, work link.Build) {
+		answer(ctx, publisher, on, workspace, work)
+	})
+}
+
+// takeWorkFrom opens this machine's link to whichever bus the mesh is on.
+//
+// **One place chooses**, as everywhere else the bus change went (novox/hq ADR 0116 step 5): a build
+// machine told about both would take work from one and answer on the other, and every log line would
+// say it was fine.
+func takeWorkFrom(credential Credential, on string) (link.BuildMachine, error) {
+	// **The credential names the bus, and there is one** (novox/hq ADR 0131, design 28 task 5.5).
+	// A credential for the mesh's bus carries user, password and fingerprint beside the address,
+	// and that is enough to dial it, pinned.
+	if !credential.onTheNewBus() {
+		return nil, fmt.Errorf("the credential at hand names %q, which is not the mesh's bus", credential.URL)
 	}
+	js, err := broker.DialPinned(credential.natsURL(), credential.Fingerprint)
+	if err != nil {
+		return nil, err
+	}
+	return link.MachineOverNATS(js, on), nil
 }

 // answer does one build and says what happened, whichever way it went.
-func answer(ctx context.Context, channel *amqp.Channel, publisher builder.Publisher,
-	on, workspace string, delivery amqp.Delivery) {
+func answer(ctx context.Context, publisher builder.Publisher, on, workspace string, work link.Build) {
+	request := work.Request()

-	// **First thing, and to stdout.** A build request that arrives and produces no visible line
-	// until it either finishes or fails is indistinguishable from one that never arrived — which
-	// cost a long diagnosis against a running mesh, chasing "the handler never fired" when the
-	// truth was only that the handler said nothing until the end.
-	fmt.Fprintf(os.Stderr, "a build request arrived (%d bytes)\n", len(delivery.Body))
-
-	var request link.BuildRequest
-	if err := json.Unmarshal(delivery.Body, &request); err != nil {
-		// Unreadable. Acknowledged and dropped rather than requeued: a message this builder
-		// cannot parse will not become parseable by being delivered again, and requeueing it
-		// would put it in front of every real request for ever.
-		fmt.Fprintf(os.Stderr, "a request could not be read and was dropped: %v\n", err)
-		_ = delivery.Ack(false)
-		return
-	}
+	// **First thing, and to stdout.** A build request that arrives and produces no visible line until
+	// it either finishes or fails is indistinguishable from one that never arrived — which cost a long
+	// diagnosis against a running mesh, chasing "the handler never fired" when the truth was only that
+	// the handler said nothing until the end.
+	fmt.Fprintf(os.Stderr, "a build request arrived for %s\n", request.Repository)

 	result := link.BuildResult{
 		ID: request.ID, Repository: request.Repository, Path: request.Path,
@@ -199,8 +167,8 @@ func answer(ctx context.Context, channel *amqp.Channel, publisher builder.Publis
 	var built builder.Result
 	if err == nil {
 		// The package-registry credential is a build input, so it is resolved before the clone: a
-		// build that could not have resolved its dependencies is refused in front of the reason,
-		// not after a clone that then fails at npm ci.
+		// build that could not have resolved its dependencies is refused in front of the reason, not
+		// after a clone that then fails at npm ci.
 		built, err = builder.Build(ctx, builder.Command, publisher,
 			request.Repository, request.Path, request.Ref, workspace, request.Held, npmrc,
 			forgeFrom(),
@@ -230,67 +198,19 @@ func answer(ctx context.Context, channel *amqp.Channel, publisher builder.Publis
 		}
 	}

-	body, err := json.Marshal(result)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "cannot report a build: %v\n", err)
-		_ = delivery.Ack(false)
+	if err := work.Announce(ctx, result); err != nil {
+		// Said, not fatal: the build happened. A build reported as failed because announcing it
+		// failed is a lie about work that was done — and the request stays unsettled below only if
+		// nothing was said at all, so another machine can try.
+		fmt.Fprintf(os.Stderr, "cannot say what came of a build: %v\n", err)
 		return
 	}

-	// Always through the exchange, whether or not somebody is waiting.
-	//
-	// **Never the default exchange.** Permission there is granted per exchange rather than per
-	// queue, so a builder allowed to use it could publish into any node's queue — the privilege a
-	// build machine most obviously should not have. An asker binds its own reply queue to this
-	// key and filters by correlation; a control plane that records builds is bound to it too, so
-	// a result nobody asked for is still kept rather than reported into the void.
-	publishCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
-	defer cancel()
-	if err := channel.PublishWithContext(publishCtx, link.Exchange, link.KeyBuilt, false, false,
-		amqp.Publishing{
-			ContentType:   "application/json",
-			CorrelationId: result.ID,
-			Body:          body,
-		}); err != nil {
-		fmt.Fprintf(os.Stderr, "cannot answer a build request: %v\n", err)
+	// Settled only once the outcome is away, so a machine that dies before answering leaves the work
+	// for another rather than losing it.
+	if err := work.Done(); err != nil {
+		fmt.Fprintf(os.Stderr, "the outcome is away and the request could not be settled: %v\n", err)
 	}
-	// **And announced, which is a different act from answering.** The reply goes to whoever asked
-	// and is correlated to their request; this says to the whole mesh that a module now exists at
-	// a commit, and the catalogue places it in the module graph (novox/hq ADR 0072). A build
-	// nobody asked for still has to be announced, or the graph knows less than the registry does.
-	//
-	// Only on success: a failed build produced no module-version, and announcing one would put
-	// something in the graph that was never made.
-	if result.Failed == "" && result.Commit != "" {
-		announced := map[string]any{
-			"module": moduleOf(result.Manifest), "commit": result.Commit,
-			"repository": result.Repository, "path": result.Path, "ref": result.Ref,
-			"manifest": json.RawMessage(result.Manifest), "against": result.Against,
-			"made": result.Made,
-		}
-		if err := link.EmitEvent(publishCtx, channel, link.KeyModuleBuilt, "builder", on, announced); err != nil {
-			// Said, not fatal: the build happened and was answered. A module the catalogue has not
-			// heard of is a gap somebody can close; a build reported as failed because announcing
-			// it failed is a lie about work that was done.
-			fmt.Fprintf(os.Stderr, "  built, but could not announce it: %v\n", err)
-		}
-	}
-
-	// Acknowledged only once the answer is away, so a builder that dies before answering leaves
-	// the request for another machine rather than losing it.
-	_ = delivery.Ack(false)
-}
-
-// moduleOf reads the module's name out of the manifest it just built, which is the only place it is
-// authoritative — the request named a repository and a path, not a module.
-func moduleOf(manifest json.RawMessage) string {
-	var named struct {
-		Module string `json:"module"`
-	}
-	if err := json.Unmarshal(manifest, &named); err != nil {
-		return ""
-	}
-	return named.Module
 }

 // packagesFrom is where a build resolves the mesh's own published packages — the SDK above all
@@ -499,13 +419,8 @@ func brokerFrom() (Credential, error) {
 		// broker is then verified against whatever this machine already trusts.
 		return Credential{URL: said}, nil
 	}
-	url := strings.TrimSpace(os.Getenv("MESH_BROKER_AMQP"))
-	if url == "" {
-		return Credential{}, fmt.Errorf(
-			"neither MESH_BROKER_FILE nor MESH_BROKER_AMQP: a builder with no broker has " +
-				"nothing to build")
-	}
-	return Credential{URL: url}, nil
+	return Credential{}, fmt.Errorf(
+		"no MESH_BROKER_FILE: a build machine with no credential for the bus has nothing to build")
 }

 // Credential is what a build machine is given so it can reach the broker.
@@ -517,48 +432,24 @@ func brokerFrom() (Credential, error) {
 // **The same shape a node gets, for the same reason** (novox/hq ADR 0004): the fingerprint travels
 // out of band — here, sealed with the credential — and the endpoint is verified once at connect.
 type Credential struct {
-	URL string `json:"url"`
-	// Fingerprint is SHA-256 over the broker certificate's DER bytes, or empty to verify the
-	// ordinary way.
+	URL         string `json:"url"`
 	Fingerprint string `json:"fingerprint,omitempty"`
+	// User and Password ride beside the address on the bus being built (design 25): a credential
+	// embedded in a URL leaks into every log line that prints a connection, so the mesh seals them
+	// as two fields and this machine joins them once, here, to dial.
+	User     string `json:"user,omitempty"`
+	Password string `json:"password,omitempty"`
 }

-// dial opens the connection, pinning the broker's certificate when there is one to pin.
-func dial(held Credential) (*amqp.Connection, error) {
-	if held.Fingerprint == "" {
-		return amqp.Dial(held.URL)
-	}
-	return amqp.DialTLS(held.URL, pinning(held.Fingerprint))
-}
+// onTheNewBus is whether a credential is for the bus being built: its address says so, and the
+// mesh only ever seals such a credential with the user and password beside it.
+func (c Credential) onTheNewBus() bool { return strings.HasPrefix(strings.TrimSpace(c.URL), "nats://") }

-// pinning is a TLS configuration that trusts exactly one certificate.
-//
-// InsecureSkipVerify with a VerifyPeerCertificate is **pinning, not skipping**: the standard chain
-// check is replaced, not removed, and what replaces it is stricter — one certificate is accepted
-// rather than every certificate a public authority would sign.
-//
-// Its own function so a test can drive it against a real handshake. A pin check that is only ever
-// exercised through a broker is a pin check nothing tests.
-func pinning(fingerprint string) *tls.Config {
-	return &tls.Config{
-		InsecureSkipVerify: true,
-		VerifyPeerCertificate: func(raw [][]byte, _ [][]*x509.Certificate) error {
-			if len(raw) == 0 {
-				return errors.New("the broker presented no certificate")
-			}
-			// The leaf, and in the same spelling the mesh writes it — `sha256:` and 64 hex
-			// characters. Comparing a bare digest against a written fingerprint never matches,
-			// and the failure is indistinguishable from being pointed at the wrong broker.
-			sum := sha256.Sum256(raw[0])
-			got := "sha256:" + hex.EncodeToString(sum[:])
-			if got != fingerprint {
-				return fmt.Errorf(
-					"this is not the broker this builder was told about\n  expected %s\n  "+
-						"got      %s\nEither this mesh's broker was replaced, or this builder is "+
-						"being pointed at something else. Retrying will not help",
-					fingerprint, got)
-			}
-			return nil
-		},
+// natsURL is the address with this machine's credential in it, for the one dial that needs it.
+func (c Credential) natsURL() string {
+	rest := strings.TrimPrefix(strings.TrimSpace(c.URL), "nats://")
+	if c.User == "" {
+		return "nats://" + rest
 	}
+	return "nats://" + c.User + ":" + c.Password + "@" + rest
 }
@@ -14,8 +14,8 @@ func TestBuilderDiagnosticsStayOffStdout(t *testing.T) {
 	allowed := map[string]bool{
 		"string(body)": true, // once.go: the result JSON, which IS stdout
 		"version)":     true, // --version
-		`"stopping")`: true,  // the loop.s shutdown line
-		"usage)":       true,  // --help text, for a human
+		`"stopping")`:  true, // the loop.s shutdown line
+		"usage)":       true, // --help text, for a human
 	}
 	for _, file := range []string{"once.go", "main.go"} {
 		src, err := os.ReadFile(file)
@@ -15,6 +15,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/novox/mesh-controller/internal/broker"
 )

 // Where a builder publishes.
@@ -193,9 +195,9 @@ func TestThePinIsComparedInTheSpellingTheMeshWritesIt(t *testing.T) {
 	}
 }

-// handshakeWith runs the builder's own pin check against an address.
+// handshakeWith runs the pin check the builder dials with against an address.
 func handshakeWith(address, pin string) error {
-	conn, err := tls.Dial("tcp", address, pinning(pin))
+	conn, err := tls.Dial("tcp", address, broker.PinnedToFingerprint(pin))
 	if err != nil {
 		return err
 	}
@@ -17,8 +17,8 @@ import (

 var aDigest = "sha256:" + strings.Repeat("e", 64)

-// **A build is recorded by digest and path**, whatever address the builder pushed to — and only
-// what the build made is rewritten: an image the module runs from elsewhere is left where it says.
+// **A build is recorded by digest and path**, whatever address the builder pushed to — what it
+// made and what it stood on both; an image the module runs from elsewhere is left where it says.
 func TestABuildIsRecordedWithoutTheStoresAddress(t *testing.T) {
 	manifest, _ := json.Marshal(map[string]any{
 		"module": "gitea", "version": "1",
@@ -65,8 +65,11 @@ func TestABuildIsRecordedWithoutTheStoresAddress(t *testing.T) {
 	if strings.Contains(string(kept.Manifest), "anchor.internal:5100") {
 		t.Errorf("the recorded manifest still carries the store's address:\n%s", kept.Manifest)
 	}
-	if kept.Against[0] != "anchor.internal:5100/mesh-tools/runtime@"+aDigest {
-		t.Errorf("what the build stood on was rewritten: %v", kept.Against)
+	// What the build stood on is an edge to another module's artifact, and it is recorded the way
+	// that artifact is: by path in the store, so the edge still names the same thing when the
+	// store answers at another address.
+	if kept.Against[0] != catalogue.ArtifactStoreScheme+"mesh-tools/runtime@"+aDigest {
+		t.Errorf("what the build stood on was recorded by address: %v", kept.Against)
 	}
 }

@@ -37,13 +37,13 @@ func askCommand(ctx context.Context, args []string) error {
 		arguments = json.RawMessage(positionals[2])
 	}

-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
 	defer server.Close()

-	answer, err := link.Ask(ctx, server.Channel(), module, tool, arguments, *wait)
+	answer, err := link.Ask(ctx, server.Bus(), module, tool, arguments, *wait)
 	if err != nil {
 		return err
 	}
@@ -2,8 +2,6 @@ package main

 import (
 	"context"
-	"crypto/rand"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -31,6 +29,51 @@ import (
 // control plane may send a machine is bounded by the declaration language. This is the shape the
 // builder module will take when it is given work over the broker; today a person runs it, and the
 // mesh records the result the same way either way.
+// buildOn rebuilds every module the mesh holds that stands on the named module's artifacts — the
+// rebuild a changed base needs, which nothing else asks for: their sources did not move, and
+// "behind" does not see a base that did (novox/hq 04-ISSUES/131). Bases first among them too.
+func buildOn(ctx context.Context, base string, wait time.Duration) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	held, err := open.inventory.Catalogued(ctx)
+	if err != nil {
+		return err
+	}
+	against, err := open.inventory.BuiltAgainst(ctx)
+	if err != nil {
+		return err
+	}
+	var on []inventory.Entry
+	for _, e := range held {
+		if standsOnModule(e, base, against) {
+			on = append(on, e)
+		}
+	}
+	if len(on) == 0 {
+		fmt.Printf("nothing the mesh holds stands on %s\n", base)
+		return nil
+	}
+	on = orderByBases(on, against)
+	fmt.Printf("%d module(s) stand on %s:\n", len(on), base)
+	var failed []string
+	for _, e := range on {
+		fmt.Printf("--- %s\n", e.Manifest.Module)
+		source := buildSource{Repository: e.Source.Repository, Seat: e.Source.Seat}
+		if err := buildOne(ctx, source, e.Source.Path, e.Source.Ref, wait); err != nil {
+			fmt.Printf("  %v\n", err)
+			failed = append(failed, e.Manifest.Module)
+		}
+	}
+	if len(failed) > 0 {
+		return fmt.Errorf("%d of %d could not be built: %s", len(failed), len(on), strings.Join(failed, ", "))
+	}
+	fmt.Printf("\n%d module(s) rebuilt on %s. `push --behind` sends them on\n", len(on), base)
+	return nil
+}
+
 func buildCommand(ctx context.Context, args []string) error {
 	set := flag.NewFlagSet("build", flag.ContinueOnError)
 	ref := set.String("ref", "", "the branch, tag or commit to build")
@@ -46,6 +89,7 @@ func buildCommand(ctx context.Context, args []string) error {
 	// retype each repository is asking them to be the loop. Naming a repository and asking which
 	// ones need building are different requests, so they are not combined.
 	behind := set.Bool("behind", false, "every module the mesh holds older than its source has")
+	on := set.String("on", "", "rebuild every module that stands on this module's artifacts — the rebuild a changed base needs")
 	// A repository on the mesh's own forge, named by its path there (novox/hq ADR 0111). Without it
 	// the repository is external, cloned exactly as given — see source.go.
 	self := set.Bool("self", false, "the repository is a path on the forge holding the git seat")
@@ -53,6 +97,13 @@ func buildCommand(ctx context.Context, args []string) error {
 	if err != nil {
 		return err
 	}
+	if *on != "" {
+		if len(positionals) != 0 || *behind || *self {
+			return errors.New("build --on <module> names a base and nothing else")
+		}
+		return buildOn(ctx, *on, *wait)
+	}
+
 	if *behind {
 		if len(positionals) != 0 || *self {
 			return errors.New("build <repository> or build --behind, not both: one names a " +
@@ -61,7 +112,7 @@ func buildCommand(ctx context.Context, args []string) error {
 		return buildBehind(ctx, *wait)
 	}
 	if len(positionals) != 1 {
-		return errors.New("build <repository> [--self] [--path P] [--ref R] [--wait D] [--dry-run]")
+		return errors.New("build <repository> [--self] [--path P] [--ref R] [--wait D] [--dry-run]  |  build --behind  |  build --on <module>")
 	}
 	source := buildSource{Repository: positionals[0]}
 	if *self {
@@ -81,8 +132,9 @@ func buildCommand(ctx context.Context, args []string) error {
 //
 // **By digest and path, never by where it was pushed** (novox/hq 04-ISSUES/102). The builder
 // says `<registry>:<port>/<module>/<artifact>@sha256:…`; the mesh records the artifact-store
-// reference and composes the store's address back in where a reference is used. `against` is kept
-// as announced: it is what the build stood on as the builder saw it, and the catalogue's edge.
+// reference and composes the store's address back in where a reference is used. `against` — what
+// the build stood on, the catalogue's edge — is recorded the same way, so an edge names a module's
+// artifact and not the machine it was pulled from.
 func buildFrom(result link.BuildResult) inventory.Build {
 	kept := inventory.Build{
 		ID: result.ID, Repository: result.Repository, Ref: result.Ref,
@@ -92,7 +144,10 @@ func buildFrom(result link.BuildResult) inventory.Build {
 		// edges, and it is not always listening when a build happens — on a fresh mesh it cannot
 		// be, for exactly the modules it needs most. Keeping them is what makes a replay able to
 		// rebuild the graph rather than a list of names.
-		Path: result.Path, Against: result.Against,
+		Path: result.Path,
+	}
+	for _, ref := range result.Against {
+		kept.Against = append(kept.Against, catalogue.Recorded(ref))
 	}
 	var announced []inventory.Artifact
 	for _, made := range result.Made {
@@ -206,85 +261,45 @@ func builderCommand(ctx context.Context, args []string) error {
 	}
 	name := positionals[1]

-	management, err := broker.ManagementFromEnvironment()
+	// **The build machine's credential is a module's credential** (novox/hq ADR 0131, design 28
+	// task 5.5): minted into the mesh's records and sealed to the machine as the builder module's
+	// broker secret, usable at the next push — the same act `module issue` performs, and the same
+	// account the composed user list carries. Nothing is created on a server; the bus reads the list.
+	open, err := openStores(ctx)
 	if err != nil {
 		return err
 	}
-
-	// The same shape of secret a token carries: enough entropy that guessing is not a strategy,
-	// and safe to put in a URL because that is where it goes.
-	raw := make([]byte, 32)
-	if _, err := rand.Read(raw); err != nil {
+	defer open.Close()
+	inv := open.inventory
+	shelf, err := inv.Catalogue(ctx)
+	if err != nil {
 		return err
 	}
-	password := base64.RawURLEncoding.EncodeToString(raw)
-	if err := management.CreateBuilderAccount(ctx, name, password); err != nil {
+	m, known := shelf[*module]
+	if !known {
+		return fmt.Errorf("%s is not in the catalogue; `module add` it first", *module)
+	}
+	fmt.Printf("build machine %s: ", name)
+	node := *forNode
+	if node == "" {
+		entries, err := inv.Catalogued(ctx)
+		if err != nil {
+			return err
+		}
+		for _, e := range entries {
+			if e.Manifest.Module == *module && len(e.On) > 0 {
+				node = e.On[0]
+			}
+		}
+	}
+	if node == "" {
+		return fmt.Errorf("%s is assigned nowhere; `assign <machine> %s` first, or say --node", *module, *module)
+	}
+	address, err := broker.BusAddress()
+	if err != nil {
 		return err
 	}
-
-	fmt.Printf("broker account %s created, scoped to the %s queue and the %s exchange\n\n",
-		name, link.BuildQueue, link.Exchange)
-
-	if *forNode != "" {
-		known, err := broker.FromEnvironment()
-		if err != nil {
-			return fmt.Errorf("cannot deliver a credential without knowing where the broker is: %w", err)
-		}
-		inv, err := openInventory(ctx)
-		if err != nil {
-			return err
-		}
-		defer inv.Close()
-
-		brokerAddr, err := brokerReachableAt(ctx, inv, known, *forNode)
-		if err != nil {
-			return err
-		}
-
-		// The URL and what verifies the broker, together. A mesh's broker presents a certificate
-		// of the mesh's own, which is in no public trust store — so a URL on its own reaches only
-		// a broker somebody else vouches for, and the connection fails at TLS with an error about
-		// an unknown authority rather than about a missing pin.
-		//
-		// **The same two facts a node's token carries** (novox/hq ADR 0004), delivered the same
-		// way: out of band relative to the broker, so what is trusted does not come from the thing
-		// being trusted.
-		held, err := json.Marshal(struct {
-			URL         string `json:"url"`
-			Fingerprint string `json:"fingerprint,omitempty"`
-		}{
-			URL:         fmt.Sprintf("amqps://%s:%s@%s/", name, password, brokerAddr),
-			Fingerprint: known.Fingerprint,
-		})
-		if err != nil {
-			return err
-		}
-		if err := inv.AcceptSecretForModule(ctx, *forNode, *module, "broker", string(held)); err != nil {
-			return err
-		}
-		// Not printed. It is sealed to that machine and the mesh cannot read it back, which is
-		// the whole point — printing it here would put the one copy that matters on a terminal.
-		fmt.Printf("  sealed to %s, for the %s module. It arrives with the next push.\n",
-			*forNode, *module)
-		fmt.Printf("  run `push %s` to send it\n", *forNode)
-		return nil
-	}
-
-	// The whole line only when the address is known. A URL with a placeholder where the host
-	// should be is a URL somebody pastes and then debugs, and the placeholder is the last thing
-	// they look at.
-	if known, err := broker.FromEnvironment(); err == nil {
-		fmt.Printf("  MESH_BROKER_AMQP=amqps://%s:%s@%s/\n\n", name, password, known.Address)
-	} else {
-		fmt.Printf("  the password is %s\n\n", password)
-		fmt.Printf("  This control plane has no %s, so it cannot say where the broker is.\n"+
-			"  Put the password in MESH_BROKER_AMQP on the build machine.\n\n",
-			broker.AddressVar)
-	}
-	// Shown once, like a token, and for the same reason: what is stored is the broker's own hash
-	// of it, and a control plane that could show it back would be a control plane that holds it.
-	fmt.Println("This is the only time it is shown.")
-	return nil
+	return issueOnTheNewBus(ctx, inv, m, node, address)
 }

 // buildBehind builds every module the mesh holds older than its source has.
@@ -329,6 +344,14 @@ func buildBehind(ctx context.Context, wait time.Duration) error {
 	}
 	fmt.Println()

+	// Bases first: a module built before the module it stands on is built against the old one
+	// and reports success (novox/hq 04-ISSUES/131).
+	against, err := inv.BuiltAgainst(ctx)
+	if err != nil {
+		return err
+	}
+	stale = orderByBases(stale, against)
+
 	var failed []string
 	for _, e := range stale {
 		fmt.Printf("--- %s\n", e.Manifest.Module)
@@ -368,7 +391,7 @@ func buildOne(ctx context.Context, source buildSource, path, ref string, wait ti
 	}
 	defer ident.Close()

-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -395,7 +418,13 @@ func buildOne(ctx context.Context, source buildSource, path, ref string, wait ti
 	}
 	fmt.Println()

-	result, err := link.RequestBuild(ctx, server.Channel(), request, wait)
+	ask, err := askOver(server)
+	if err != nil {
+		return err
+	}
+	defer ask.Close()
+
+	result, err := ask.Submit(ctx, request, wait)
 	if err != nil {
 		return err
 	}
@@ -466,13 +495,19 @@ func buildAndShow(ctx context.Context, source buildSource, path, ref string, wai
 		return err
 	}
 	defer ident.Close()
-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
 	defer server.Close()

-	result, err := link.RequestBuild(ctx, server.Channel(), link.BuildRequest{
+	ask, err := askOver(server)
+	if err != nil {
+		return err
+	}
+	defer ask.Close()
+
+	result, err := ask.Submit(ctx, link.BuildRequest{
 		ID:         fmt.Sprintf("%s-%d", "build", time.Now().UnixNano()),
 		Repository: repository, Path: path, Ref: ref,
 		Held: heldBy(ctx),
@@ -557,3 +592,16 @@ func heldBy(ctx context.Context) map[string]string {
 	}
 	return routed
 }
+
+// askOver opens the way a build is asked for, on whichever bus the mesh is on.
+//
+// **One place chooses**, as everywhere else the bus change went (novox/hq ADR 0116 step 5). On the bus
+// the mesh runs on today this needs the controller's own connection, so it is handed one; on the bus
+// being built it dials, because a build request is a one-shot and holds nothing else.
+func askOver(_ *link.Server) (link.Builders, error) {
+	address, err := broker.BusAddress()
+	if err != nil {
+		return nil, err
+	}
+	return link.BuildsOverNATS(address)
+}
@@ -114,8 +114,12 @@ func run() error {
 		return planCommand(ctx, args[1:])
 	case "push":
 		return pushCommand(ctx, args[1:])
+	case "rollout":
+		return rolloutCommand(ctx, args[1:])
 	case "seats":
 		return seatsCommand(ctx, args[1:])
+	case "seat":
+		return seatCommand(ctx, args[1:])
 	case "status":
 		return statusCommand(ctx, args[1:])
 	case "version":
@@ -180,6 +184,7 @@ func usage() {
  operator key show                         the operator key, and what it can recover
  build <repository> [--ref R]   have a build machine build it, and record what came out
  build --behind                 build every module the mesh holds older than its source
+  build --on <module>            rebuild every module that stands on this module's artifacts, bases first
  builds [<module>]              what has been built lately, and what came of it
  builder issue <name>           a broker account for a build machine, scoped to build work,
                                 delivered as the builder module's broker secret (module add it first)
@@ -2,8 +2,6 @@ package main

 import (
 	"context"
-	"crypto/rand"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -257,66 +255,15 @@ func moduleCommand(ctx context.Context, args []string) error {
 			return err
 		}

-		management, err := broker.ManagementFromEnvironment()
+		// Which bus this mesh is on. A module gets a credential for exactly one, and the two are
+		// made in entirely different ways: on the bus the mesh runs on today an account is a
+		// management call, and on the bus being built it is a row the next composition writes into
+		// the server's user list (novox/hq design 25 §4).
+		busAddress, err := broker.BusAddress()
 		if err != nil {
 			return err
 		}
-		// The foundation owns the bus; make sure it exists before a module binds onto it.
-		if err := management.EnsureEventExchanges(ctx); err != nil {
-			return err
-		}
-
-		secret := make([]byte, 32)
-		if _, err := rand.Read(secret); err != nil {
-			return err
-		}
-		password := base64.RawURLEncoding.EncodeToString(secret)
-		account, err := management.CreateModuleAccount(ctx, *forNode, module, password, m.Emits, m.Consumes)
-		if err != nil {
-			return err
-		}
-		// A consumer's queue, with its dead-letter, is the foundation's to declare — its own account
-		// may not (ADR 0043). Made now, so it exists before the module binds onto it.
-		if len(m.Consumes) > 0 {
-			if err := management.EnsureModuleQueue(ctx, *forNode, module); err != nil {
-				return err
-			}
-		}
-
-		known, err := broker.FromEnvironment()
-		if err != nil {
-			return fmt.Errorf("cannot deliver a credential without knowing where the broker is: %w", err)
-		}
-		brokerAddr, err := brokerReachableAt(ctx, inv, known, *forNode)
-		if err != nil {
-			return err
-		}
-		// The URL and what verifies the broker, together — a mesh's broker presents its own
-		// certificate, in no public trust store, so a URL alone fails at TLS (as `builder issue`).
-		held, err := json.Marshal(struct {
-			URL         string `json:"url"`
-			Fingerprint string `json:"fingerprint,omitempty"`
-			Node        string `json:"node"`
-			Module      string `json:"module"`
-		}{
-			URL:         fmt.Sprintf("amqps://%s:%s@%s/", account, password, brokerAddr),
-			Fingerprint: known.Fingerprint,
-			// The node and module the account is for, so the runtime names its queue as the mesh
-			// scoped it (<node>.<module>.events) without a manifest having to interpolate a node.
-			Node:   *forNode,
-			Module: module,
-		})
-		if err != nil {
-			return err
-		}
-		if err := inv.AcceptSecretForModule(ctx, *forNode, module, "broker", string(held)); err != nil {
-			return err
-		}
-		fmt.Printf("broker account %s created for %s, scoped to what it emits and consumes\n",
-			account, module)
-		fmt.Printf("  sealed to %s. It arrives with the next push — `push %s` to send it\n",
-			*forNode, *forNode)
-		return nil
+		return issueOnTheNewBus(ctx, inv, m, *forNode, busAddress)

 	default:
 		return fmt.Errorf("module has no %q; it has add, list, moved, forget and issue", args[0])
@@ -567,3 +514,91 @@ func mayIssue(m catalogue.Manifest) error {
 	}
 	return nil
 }
+
+// issueOnTheNewBus gives an assigned module its credential on the bus being built.
+//
+// **Three things differ from a management call, and each is the point of the move.** The credential
+// is minted into the mesh's records and becomes usable at the next composition, so there is no
+// server to be reachable for this to work. The password travels beside the address rather than inside
+// it, because the runtime's contract already separates them and a credential embedded in a URL is one
+// that leaks into every log line that prints a connection. And the module's durable consumer is
+// derived from what it declared rather than declared by name, so a module cannot ask for delivery of
+// something it did not say it consumes.
+func issueOnTheNewBus(ctx context.Context, inv *inventory.Inventory, m catalogue.Manifest,
+	node, busAddress string) error {
+
+	user := broker.Principal{Kind: broker.KindModule, Node: node, Module: m.Module}.Username()
+	password, err := inv.MintBusPassword(ctx, inventory.BusUser{
+		Username: user, Kind: inventory.BusModule, Node: node, Module: m.Module,
+	})
+	if err != nil {
+		return err
+	}
+
+	// Where the module is told to find the bus, and what certificate it must present. The same pair
+	// a node is told, for the same reason: a mesh's bus presents its own certificate, in no public
+	// trust store, so an address alone fails at TLS.
+	known, err := broker.FromEnvironment()
+	if err != nil {
+		return fmt.Errorf("cannot deliver a credential without knowing where the bus is: %w", err)
+	}
+	reachable, err := brokerReachableAt(ctx, inv, known, node)
+	if err != nil {
+		return err
+	}
+	return issueWith(ctx, inv, m, node, busAddress, known, reachable, user, password)
+}
+
+// issueWith is the delivery half: the minted password sealed to the machine as the module's broker
+// secret, and the module's consumer created where the bus can be reached. Split from the minting
+// so the move can issue every module against a bus whose address it worked out itself
+// (`rollout mint`, design 28 task 5.2) rather than the one in this process's environment.
+func issueWith(ctx context.Context, inv *inventory.Inventory, m catalogue.Manifest,
+	node, busAddress string, known broker.Broker, reachable, user, password string) error {
+	held, err := json.Marshal(struct {
+		URL         string `json:"url"`
+		Fingerprint string `json:"fingerprint,omitempty"`
+		Node        string `json:"node"`
+		Module      string `json:"module"`
+		User        string `json:"user"`
+		Password    string `json:"password"`
+	}{
+		URL: "nats://" + reachable, Fingerprint: known.Fingerprint,
+		Node: node, Module: m.Module, User: user, Password: password,
+	})
+	if err != nil {
+		return err
+	}
+	if err := inv.AcceptSecretForModule(ctx, node, m.Module, "broker", string(held)); err != nil {
+		return err
+	}
+
+	// And how it hears what it consumes. Derived from its declaration, and only when it declared
+	// something: a module that consumes nothing needs no consumer, and creating one would be a
+	// durable subscription nobody reads.
+	if consumer, needed := broker.ConsumerFor(broker.Principal{
+		Kind: broker.KindModule, Node: node, Module: m.Module,
+		Emits: m.Emits, Consumes: m.Consumes, Serves: m.Tools,
+	}); needed {
+		if busAddress == "" {
+			fmt.Printf("  %s consumes; its consumer is created when the bus is reachable (`push`, then "+
+				"`rollout mint` again is harmless)\n", m.Module)
+		} else {
+			js, err := broker.Dial(busAddress)
+			if err != nil {
+				return fmt.Errorf("the credential is minted and the mesh cannot reach the bus to create "+
+					"how %s hears what it consumes: %w", m.Module, err)
+			}
+			defer js.Close()
+			if err := js.EnsureConsumer(consumer); err != nil {
+				return err
+			}
+		}
+	}
+
+	fmt.Printf("bus user %s minted for %s, scoped to what it emits and consumes\n", user, m.Module)
+	fmt.Printf("  sealed to %s. It arrives with the next push — `push %s` to send it\n", node, node)
+	fmt.Printf("  and it works once the bus has been told: the user list is composed into the " +
+		"machine holding mesh-broker\n")
+	return nil
+}
@@ -256,7 +256,7 @@ func network(ctx context.Context, inv *inventory.Inventory, on map[string]bool,
 					"Re-place it — `overlay place %s --hub --endpoint <host>:%d …` — and push again; "+
 					"nothing was composed", p.Name, t.Interface, wrong, p.Name, t.Port)
 			}
-			n.TakesOver = &overlay.TakeOver{Interface: t.Interface, Unit: t.Unit, Config: t.Config, Port: t.Port}
+			n.TakesOver = &overlay.TakeOver{Interface: t.Interface, Unit: t.Unit, Config: t.Config, Port: t.Port, MTU: t.MTU}
 		}
 		if p.Hub {
 			for _, c := range carried {
@@ -537,6 +537,15 @@ func onTheNetwork(ctx context.Context, inv *inventory.Inventory,
 	if err != nil {
 		return nil, err
 	}
+	// **With the seat holders on record**, or a machine running the next holder of a seat beside
+	// the current one resolves as two holders, is refused, and drops out of the map — taking the
+	// address every other machine composes for what it offers (novox/hq ADR 0131). Found live:
+	// the control node vanished from the private network the moment the new bus was assigned
+	// beside the old one.
+	holdings, err := inv.Holdings(ctx)
+	if err != nil {
+		return nil, err
+	}
 	var out []inventory.Overlay
 	for _, p := range places {
 		if p.Address == "" {
@@ -549,7 +558,7 @@ func onTheNetwork(ctx context.Context, inv *inventory.Inventory,
 		caps, _ := inv.ProfileOf(ctx, p.Name)
 		got, err := catalogue.Resolve(shelf, assigned,
 			catalogue.Node{Name: p.Name, Site: p.Site, Capabilities: caps},
-			catalogue.World{Unchecked: true})
+			catalogue.World{Unchecked: true, Holdings: holdings})
 		if err != nil {
 			continue
 		}
@@ -10,7 +10,6 @@ import (

 	"github.com/novox/mesh-controller/internal/broker"
 	"github.com/novox/mesh-controller/internal/inventory"
-	"github.com/novox/mesh-controller/internal/link"
 	"github.com/novox/mesh-controller/internal/token"
 )

@@ -67,8 +66,14 @@ 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 "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;
+		// an optional second argument is the home when it is not /home/<account>.
+		return nodeAccount(ctx, inv, args[1:])
+
 	default:
-		return fmt.Errorf("node has no %q; it has add, list, show and public-domain", args[0])
+		return fmt.Errorf("node has no %q; it has add, list, show, public-domain and account", args[0])
 	}
 }

@@ -106,6 +111,39 @@ func modeOf(n inventory.Node) string {
 }

 // publicDomainUsage is the one description of the three forms, so a refusal and the help agree.
+// nodeAccount reports or sets a node's operator account (novox/hq to-be 29). Read-shaped with no
+// argument, like public-domain: `node account novox` answers, it does not change anything.
+func nodeAccount(ctx context.Context, inv *inventory.Inventory, positionals []string) error {
+	if len(positionals) == 0 || len(positionals) > 3 {
+		return errors.New("node account <name> — what it is now; " +
+			"node account <name> <account> [home] — set it (home defaults to /home/<account>)")
+	}
+	node := positionals[0]
+	if len(positionals) == 1 {
+		who, err := inv.NodeByName(ctx, node)
+		if err != nil {
+			return err
+		}
+		if who.Account == "" {
+			fmt.Printf("%s has no operator account known\n", node)
+			fmt.Printf("  `node account %s <account>` sets it\n", node)
+			return nil
+		}
+		fmt.Printf("%s logs a person in as %s (home %s)\n", node, who.Account, who.Home())
+		return nil
+	}
+	home := ""
+	if len(positionals) == 3 {
+		home = positionals[2]
+	}
+	if err := inv.SetAccount(ctx, node, positionals[1], home); err != nil {
+		return err
+	}
+	fmt.Printf("%s logs a person in as %s\n", node, positionals[1])
+	fmt.Printf("  run `push %s` once ssh-client is assigned, to send its operator config\n", node)
+	return nil
+}
+
 const publicDomainUsage = "node public-domain <name> — what it is now; " +
 	"<name> <domain> to set it; <name> --clear to take it away"

@@ -219,15 +257,6 @@ func tokenCommand(ctx context.Context, args []string) error {
 	// chicken-and-egg entirely: the mesh runs the broker, so a joining node's credentials can
 	// exist before it does. The one-time secret IS the password, so a node's first connection is
 	// already authenticated and enrolment is what happens over it.
-	if management, err := broker.ManagementFromEnvironment(); err == nil {
-		if err := management.CreateNodeAccount(ctx, issued.Node.Name, issued.Secret); err != nil {
-			return err
-		}
-		fmt.Printf("broker account %s created, scoped to %s and the %s exchange\n\n",
-			issued.Node.Name, link.QueueFor(issued.Node.Name), link.Exchange)
-	} else if !errors.Is(err, broker.ErrNotConfigured) {
-		return err
-	}

 	made := token.Token{Node: issued.Node.Name, Signer: key.Public, Secret: issued.Secret,
 		Adopted: issued.Node.Adopted}
@@ -2,12 +2,15 @@ package main

 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"flag"
 	"fmt"
 	"os"
 	"strings"

+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/secrets"
 )

@@ -26,9 +29,25 @@ import (
 //	operator key make [--out <file>]    make a keypair: private half to the file, public half printed
 //	operator key set <public>           tell the mesh which key to seal to
 //	operator key show                   the public key, its fingerprint, and what it can recover
-const operatorUsage = "operator key make [--out <file>] | operator key set <public> [--replace] | operator key show"
+const operatorUsage = "operator key make [--out <file>] | operator key set <public> [--replace] | " +
+	"operator key show | operator issue <name> --invokes <tool,tool|*> | operator revoke <name> | " +
+	"operator list"

 func operatorCommand(ctx context.Context, args []string) error {
+	if len(args) == 0 {
+		return errors.New(operatorUsage)
+	}
+	// The people who may reach the mesh's tools (design 25 §7). Beside the operator's key because
+	// both answer "who, other than a machine, may do something here" — and a person reading this
+	// command's usage is asking exactly that.
+	switch args[0] {
+	case "issue":
+		return personIssue(ctx, args[1:])
+	case "revoke":
+		return personRevoke(ctx, args[1:])
+	case "list":
+		return personList(ctx)
+	}
 	if len(args) < 2 || args[0] != "key" {
 		return errors.New(operatorUsage)
 	}
@@ -160,3 +179,125 @@ func readPrivateKey(path string) (string, error) {
 	}
 	return strings.TrimSpace(string(raw)), nil
 }
+
+// personIssue gives somebody a credential for the mesh's tools, and prints it once.
+//
+// **Printed, not stored.** The mesh keeps a hash and nothing else, so this is the only moment the
+// credential exists anywhere but on the workstation that will use it — the same contract a token has,
+// and for the same reason: a credential recoverable from the mesh's store has the store's blast
+// radius.
+func personIssue(ctx context.Context, args []string) error {
+	set := flag.NewFlagSet("operator issue", flag.ContinueOnError)
+	invokes := set.String("invokes", "", "the tools this person may call, comma-separated, or * for every one")
+	if err := set.Parse(args); err != nil {
+		return err
+	}
+	if set.NArg() != 1 {
+		return errors.New("operator issue <name> --invokes <tool,tool|*>")
+	}
+	name := set.Arg(0)
+	if *invokes == "" {
+		return errors.New(
+			"say what this person may call: --invokes mesh-catalog.catalog_tools,gitea.repo_create, " +
+				"or --invokes '*' for an administrator")
+	}
+	var tools []string
+	for _, t := range strings.Split(*invokes, ",") {
+		if t = strings.TrimSpace(t); t != "" {
+			tools = append(tools, t)
+		}
+	}
+
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	if err := inv.RecordPerson(ctx, inventory.Person{Name: name, Invokes: tools}); err != nil {
+		return err
+	}
+	// Refused here rather than at the next composition, where it would stop the whole file being
+	// written for everybody. A name that cannot be part of a subject is one the server would read as
+	// a wider permission than anybody granted.
+	if _, err := broker.PermissionsFor(broker.Principal{
+		Kind: broker.KindPerson, Module: name, Invokes: tools, PasswordHash: "x",
+	}); err != nil {
+		return err
+	}
+
+	user := broker.Principal{Kind: broker.KindPerson, Module: name}.Username()
+	password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: user, Kind: inventory.BusPerson})
+	if err != nil {
+		return err
+	}
+
+	where, err := broker.FromEnvironment()
+	if err != nil && !errors.Is(err, broker.ErrNotConfigured) {
+		return err
+	}
+	held, err := json.Marshal(struct {
+		URL         string   `json:"url"`
+		Fingerprint string   `json:"fingerprint,omitempty"`
+		User        string   `json:"user"`
+		Password    string   `json:"password"`
+		Person      string   `json:"person"`
+		Invokes     []string `json:"invokes"`
+	}{
+		URL: "nats://" + where.Address, Fingerprint: where.Fingerprint,
+		User: user, Password: password, Person: name, Invokes: tools,
+	})
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("issued %s, who may call %s\n", name, strings.Join(tools, ", "))
+	fmt.Println("  this is the only time the credential is printed; the mesh keeps a hash")
+	fmt.Println("  it works once the bus has been told, which is the next push to the machine holding mesh-broker")
+	fmt.Println()
+	fmt.Println(string(held))
+	return nil
+}
+
+func personRevoke(ctx context.Context, args []string) error {
+	if len(args) != 1 {
+		return errors.New("operator revoke <name>")
+	}
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+
+	if err := open.inventory.ForgetPerson(ctx, args[0]); err != nil {
+		return err
+	}
+	// **Revoked at the next composition, not now.** The bus's users are a file, so a credential stops
+	// working when the file no longer names it. Said plainly, because "revoked" that still works for
+	// another minute is worth knowing about.
+	fmt.Printf("%s is forgotten, and their credential stops working at the next composition — "+
+		"push the machine holding mesh-broker to make it so\n", args[0])
+	return nil
+}
+
+func personList(ctx context.Context) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+
+	people, err := open.inventory.People(ctx)
+	if err != nil {
+		return err
+	}
+	if len(people) == 0 {
+		fmt.Println("nobody but machines reaches this mesh")
+		return nil
+	}
+	for _, p := range people {
+		fmt.Printf("%-20s %s\n", p.Name, strings.Join(p.Invokes, ", "))
+	}
+	return nil
+}
@@ -0,0 +1,108 @@
+package main
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/inventory"
+	"github.com/novox/mesh-controller/internal/link"
+)
+
+// entry is a module as the catalogue holds it: built, so its manifest carries no `build` any more.
+func entry(module string, _ ...string) inventory.Entry {
+	return inventory.Entry{Manifest: catalogue.Manifest{Module: module}}
+}
+
+// stoodOn is what each module's newest build recorded it was handed.
+func stoodOn(edges map[string][]string) map[string][]string {
+	out := map[string][]string{}
+	for module, bases := range edges {
+		for _, b := range bases {
+			out[module] = append(out[module], catalogue.ArtifactStoreScheme+b+"/runtime@sha256:"+strings.Repeat("0", 64))
+		}
+	}
+	return out
+}
+
+// A module built before the module it stands on is built against the old one and reports success
+// (novox/hq 04-ISSUES/131). So bases come first, however the set arrived.
+func TestBasesAreBuiltBeforeWhatStandsOnThem(t *testing.T) {
+	in := []inventory.Entry{entry("app"), entry("runtime"), entry("other"), entry("base")}
+	edges := stoodOn(map[string][]string{"app": {"runtime"}, "runtime": {"base"}})
+	got := orderByBases(in, edges)
+	pos := map[string]int{}
+	for i, e := range got {
+		pos[e.Manifest.Module] = i
+	}
+	if !(pos["base"] < pos["runtime"] && pos["runtime"] < pos["app"]) {
+		t.Fatalf("bases not first: %v", pos)
+	}
+	if len(got) != 4 {
+		t.Fatalf("an entry was lost or doubled: %d", len(got))
+	}
+	// A base outside the set is not waited for: it is not being rebuilt.
+	got = orderByBases([]inventory.Entry{entry("app")}, stoodOn(map[string][]string{"app": {"elsewhere"}}))
+	if len(got) != 1 {
+		t.Fatalf("a dependency outside the set changed the set: %v", got)
+	}
+}
+
+// A module registered from its manifest and never built still names its bases there; once built,
+// the recorded edge is what says so. Both are read, and a module never stands on itself.
+func TestWhatStandsOnAModuleIsReadFromItsBuildOrItsManifest(t *testing.T) {
+	built := entry("gitea")
+	edges := stoodOn(map[string][]string{"gitea": {"mesh-tools"}})
+	if !standsOnModule(built, "mesh-tools", edges) {
+		t.Fatal("a recorded edge was not read")
+	}
+	if standsOnModule(built, "gitea", edges) || standsOnModule(built, "postgres", edges) {
+		t.Fatal("an edge was invented")
+	}
+	fresh := inventory.Entry{Manifest: catalogue.Manifest{Module: "plex", Build: &catalogue.Build{
+		On: []catalogue.BuildsOn{{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"}},
+	}}}
+	if !standsOnModule(fresh, "mesh-tools", nil) {
+		t.Fatal("a manifest's own base was not read")
+	}
+}
+
+// A merge names a repository the way the forge does; a source is recorded the way a build was
+// asked for. The two meet on owner/repo and branch, whichever form the record took.
+func TestAMergeMatchesTheSourcesBuiltFromIt(t *testing.T) {
+	m := link.SourceMoved{Owner: "novox", Repo: "mesh-controller", Base: "main",
+		CloneURL: "http://forge.internal:20000/novox/mesh-controller.git"}
+	for _, s := range []inventory.Source{
+		{Repository: "http://forge.internal:20000/novox/mesh-controller.git", Ref: "main"},
+		{Repository: "novox/mesh-controller", Seat: "git", Ref: ""},
+		{Repository: "https://elsewhere.example/novox/mesh-controller", Ref: "main"},
+	} {
+		if !sourceIs(s, m) {
+			t.Errorf("%+v was not matched by the merge", s)
+		}
+	}
+	for _, s := range []inventory.Source{
+		{Repository: "novox/mesh-host", Seat: "git"},
+		{Repository: "http://forge.internal:20000/novox/mesh-controller.git", Ref: "release"},
+	} {
+		if sourceIs(s, m) {
+			t.Errorf("%+v was matched by a merge that is not its", s)
+		}
+	}
+}
+
+// A merge made before the source was last seen is history: it does not move the source, and a
+// merge that says nothing about when it was made is taken as news.
+func TestAMergeOlderThanTheLastLookIsHistory(t *testing.T) {
+	seen := time.Date(2026, 9, 28, 3, 0, 0, 0, time.UTC)
+	if !isHistory("2026-09-28T02:00:00Z", seen) {
+		t.Fatal("an older merge was taken as news")
+	}
+	if isHistory("2026-09-28T04:00:00Z", seen) {
+		t.Fatal("a newer merge was taken as history")
+	}
+	if isHistory("", seen) || isHistory("2026-09-28T02:00:00Z", time.Time{}) {
+		t.Fatal("a merge or a source with no time on it was refused")
+	}
+}
@@ -83,9 +83,17 @@ func planFor(ctx context.Context, open *stores, nodeName string) (catalogue.Reso
 		return catalogue.Resolution{}, nil, err
 	}

+	// The operator account this node logs a person in as, and where its home is (novox/hq to-be
+	// 29) — carried so a home-scoped file's owner and path resolve for this machine.
+	who, err := inv.NodeByName(ctx, nodeName)
+	if err != nil {
+		return catalogue.Resolution{}, nil, err
+	}
+
 	resolved, err := catalogue.Resolve(shelf, assigned,
 		catalogue.Node{Name: nodeName, Site: site, Capabilities: capabilities,
-			At: onNetwork[nodeName], PublicDomain: publicDomain}, world)
+			At: onNetwork[nodeName], PublicDomain: publicDomain,
+			Account: who.Account, AccountHome: who.AccountHome}, world)
 	if err != nil {
 		return catalogue.Resolution{}, nil, err
 	}
@@ -177,6 +185,15 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,

 	// Every node, not only the placed ones. A machine that was never put on the private network
 	// still runs modules, still holds claims, and still offers whatever it offers.
+	// **Who holds each seat on record, before anything is resolved** (novox/hq ADR 0131). Both
+	// passes below need it: without it, the assignment standing beside a seat's holder — the next
+	// holder, waiting for the handover — is refused as a second holder, and its node's whole set
+	// with it.
+	holdings, err := inv.Holdings(ctx)
+	if err != nil {
+		return catalogue.World{}, err
+	}
+
 	nodes, err := inv.Nodes(ctx)
 	if err != nil {
 		return catalogue.World{}, err
@@ -219,7 +236,7 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
 	offered := map[string][]catalogue.Provider{}
 	var firstHeld []catalogue.Held
 	for _, o := range others {
-		got, err := catalogue.Resolve(shelf, o.assigned, o.node, catalogue.World{Unchecked: true})
+		got, err := catalogue.Resolve(shelf, o.assigned, o.node, catalogue.World{Unchecked: true, Holdings: holdings})
 		if err != nil {
 			// Their set does not resolve for some other reason. Not this node's problem to
 			// report, and nothing of theirs is running, so it offers nothing.
@@ -250,7 +267,7 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
 	// with several providers (novox/hq ADR 0110), so a node consuming one resolves only once the
 	// holder is known. Without them its set is refused here, and a refused node's own claims drop
 	// out of what the mesh holds — so a second holder of one of its seats would pass unrefused.
-	world := catalogue.World{Offered: offered, Held: firstHeld}
+	world := catalogue.World{Offered: offered, Held: firstHeld, Holdings: holdings}
 	var held []catalogue.Held
 	for _, o := range others {
 		got, err := catalogue.Resolve(shelf, o.assigned, o.node, world)
@@ -488,6 +505,13 @@ func renderingFor(ctx context.Context, open *stores, node string,
 	if err != nil {
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}
+	// The private network's range, offered to a module as ${machine:mesh-range} — a module that must
+	// name the whole mesh (an intrusion filter that must never ban a tunnel peer) names it here
+	// rather than hardcoding a value it cannot know.
+	meshRange, err := overlayRange(ctx, inv)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}

 	// The artifact store as this node reaches it now — the address every image and archive the
 	// mesh built is fetched through, composed here and recorded nowhere — with what the mesh has
@@ -513,6 +537,19 @@ func renderingFor(ctx context.Context, open *stores, node string,
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}

+	// Each machine's operator account, so an ssh Host block can name the login for every node
+	// (novox/hq to-be 29). Keyed by the bare node name, which entriesFrom falls back to.
+	allNodes, err := inv.Nodes(ctx)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}
+	accounts := map[string]string{}
+	for _, n := range allNodes {
+		if n.Account != "" {
+			accounts[n.Name] = n.Account
+		}
+	}
+
 	// And every routed name → the node that serves it (novox/hq ADR 0066). Alongside the
 	// `<node>.internal` names above, so a container — or an internal ACME validator — resolves a
 	// routed name to the proxy that serves it, mesh-wide. The mesh publishes the names it was told
@@ -593,12 +630,25 @@ func renderingFor(ctx context.Context, open *stores, node string,
 	if err != nil {
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}
+	// The bus's user list, for the machine that runs the bus. Composed per push rather than kept,
+	// because it is a function of the mesh's records and a kept copy could disagree with them.
+	busUsers, err := composeBusUsers(ctx, inv, plan.Modules)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}
+	memberships, err := inv.BusMemberships(ctx)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}
 	return catalogue.Rendering{
-		Settings: settings, Generators: gens, Grants: grants, Needed: needed, Ports: ports,
+		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(), Foundation: foundation, Kept: kept, Adopted: record.Adopted,
+		Suffix:   overlay.Suffix(), MeshRange: meshRange, Accounts: accounts, Foundation: foundation,
+		Kept: kept, Adopted: record.Adopted,
 		Given: given, Taken: taken, Seats: seats, ArtifactStore: artifactStore, Built: built,
+		BusUsers: busUsers,
 	}, record, nil
 }

@@ -923,12 +973,26 @@ func planCommand(ctx context.Context, args []string) error {
 			if !ok {
 				continue
 			}
-			fmt.Printf("\n--- %v  %v ---\n%s", r["id"], r["path"], content)
+			fmt.Printf("\n--- %s ---\n%s", shownAs(r), content)
 		}
 	}
 	return nil
 }

+// shownAs is the heading `plan --show` puts over a resource's content.
+//
+// **A file written into says so.** Its content is the mesh's part of a file that is otherwise the
+// machine's — the keys of a JSON document (novox/hq ADR 0102), the region of a hosts file (issue
+// 128). Shown under a bare path it reads as the whole file, and a person checking what a take
+// replaces would see a hosts file of a dozen lines where the machine keeps thirty.
+func shownAs(r map[string]any) string {
+	heading := fmt.Sprintf("%v  %v", r["id"], r["path"])
+	if into, ok := r["into"].(string); ok && into != "" {
+		heading += fmt.Sprintf(" (written into, %s)", into)
+	}
+	return heading
+}
+
 // licencesFor is what this node can be answered with by record, and what it was put on.
 //
 // A mesh with no licences at all is the ordinary case and must not be an error: every existing
@@ -1144,6 +1208,76 @@ func portsOn(
 	return out, nil
 }

+// composeBusUsers is the bus's user list, for a push to the machine that runs the bus.
+//
+// Empty for every other machine, and for every machine while the mesh is on the bus it runs on
+// today — where accounts are a management call and there is no file to write.
+//
+// **Composed on each push, never kept.** The list is a function of the mesh's records (who exists,
+// what runs where, what each declares), and a stored copy would be a second account of who may reach
+// the bus, able to disagree with the records while both looked internally consistent (ADR 0043).
+//
+// A user the mesh has never minted a password for is **left out and said**, not written as a user
+// without one — the composer refuses that, because a user with no password is a user anybody is. That
+// is an ordinary situation with an obvious remedy (`module issue`, or enrolling), so the push carries
+// the rest rather than failing: a bus that is missing one module's user is a mesh where that module
+// cannot connect, and a bus with no file at all is a mesh where nothing can.
+func composeBusUsers(ctx context.Context, inv *inventory.Inventory,
+	onThisNode []catalogue.Manifest) (string, error) {
+
+	// **Not gated on which bus the controller is on, and that was a bug.** It read "compose this only
+	// once the mesh is on the new bus" — which cannot work, because the server needs its user list
+	// *before* anything moves onto it. Step 2 of the change is exactly that: the server stands in the
+	// mesh carrying nothing, on its own ports, while every node is still on the old bus (novox/hq
+	// ADR 0116). Under the old gating that step could not happen: the module would come up, find no
+	// accounts file, and its entrypoint would wait for one the controller had decided not to write.
+	//
+	// So the question is only whether this machine runs the module that asked for the file. A mesh
+	// that never moves has written a user list nothing reads, which costs a few hundred bytes on one
+	// node; the reverse cost a step that cannot be taken.
+	//
+	// Asked of what this push resolves to rather than of the seat's holder mesh-wide: the file is a
+	// resource of that module, so the question is whether it is here.
+	holdsTheBus := false
+	for _, m := range onThisNode {
+		if m.BusUsers != "" && m.ClaimsSeat("mesh-broker") {
+			holdsTheBus = true
+		}
+	}
+	if !holdsTheBus {
+		return "", nil
+	}
+
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		return "", err
+	}
+	users, err := broker.Users(records)
+	if err != nil {
+		return "", err
+	}
+	kept, err := inv.BusUsers(ctx)
+	if err != nil {
+		return "", err
+	}
+	hashes := make(map[string]string, len(kept))
+	for name, u := range kept {
+		hashes[name] = u.PasswordHash
+	}
+	filled, missing := broker.WithPasswords(users, hashes)
+	if len(missing) > 0 {
+		fmt.Printf("the bus's user list leaves out %d user(s) the mesh has minted no credential "+
+			"for: %s. Each is a user that cannot connect until one is issued\n",
+			len(missing), strings.Join(missing, ", "))
+	}
+	if len(filled) == 0 {
+		return "", fmt.Errorf(
+			"this machine runs the bus and not one user has a credential, so the composed list " +
+				"would refuse every connection in the mesh")
+	}
+	return broker.ComposeAccounts(filled)
+}
+
 // foundationPortsFor is the broker port, kept only when a module resolved onto this node listens
 // on it (novox/hq issue: the broker opening leaked onto every node). The foundation opening
 // exists to WIDEN the broker's `from: mesh` port to from-anywhere, because a machine enrolling is
@@ -35,3 +35,17 @@ func TestListensLinesAreEmptyForAModuleWithNothingToListenOn(t *testing.T) {
 		t.Errorf("a module with no listens should print nothing, got %v", got)
 	}
 }
+
+// `plan --show` says when a file is written into rather than over (novox/hq issue 128), or the
+// mesh's region of a hosts file reads as the whole file.
+func TestAFileWrittenIntoIsShownAsSuch(t *testing.T) {
+	region := shownAs(map[string]any{
+		"id": "mesh-wireguard.fact-node-names", "path": "/etc/hosts", "into": "block"})
+	if region != "mesh-wireguard.fact-node-names  /etc/hosts (written into, block)" {
+		t.Errorf("the region is shown as %q", region)
+	}
+	whole := shownAs(map[string]any{"id": "dnsmasq.fact-node-zones", "path": "/etc/mesh-resolver/nodes.conf"})
+	if strings.Contains(whole, "written into") {
+		t.Errorf("a whole file is shown as written into: %q", whole)
+	}
+}
@@ -38,6 +38,27 @@ func reportUnhostable(node string, plan catalogue.Resolution) {
 // nothing in it was wrong, and no one edit was the one that should have been a new file.

 // serve is the control plane running: one connection to the broker, one queue, one consumer.
+// connectLink opens the controller's link over whichever bus this process is on (design 25: one
+// variable moves it). The streams and this controller's consumers are raised first on the new bus,
+// so nothing served here finds them missing.
+func connectLink(ctx context.Context, inv *inventory.Inventory, enroller link.Enroller, listener link.Listener) (*link.Server, error) {
+	busAddress, err := broker.BusAddress()
+	if err != nil {
+		return nil, err
+	}
+	if inv != nil {
+		if err := raiseTheBus(ctx, inv, busAddress); err != nil {
+			return nil, err
+		}
+	}
+	js, err := broker.Dial(busAddress)
+	if err != nil {
+		return nil, fmt.Errorf("the mesh is on the bus at %s and this control plane cannot reach it: %w",
+			broker.BareAddress(busAddress), err)
+	}
+	return link.ConnectNats(js, enroller, listener), nil
+}
+
 func serve(ctx context.Context) error {
 	open, err := openStores(ctx)
 	if err != nil {
@@ -61,11 +82,6 @@ func serve(ctx context.Context) error {
 	}
 	fmt.Printf("signing as %s\n", key.Fingerprint()[:16])

-	management, err := broker.ManagementFromEnvironment()
-	if err != nil && !errors.Is(err, broker.ErrNotConfigured) {
-		return err
-	}
-
 	// Where the broker is and what to expect there, so a node can be told how to come back
 	// without a person and a new token.
 	known, err := broker.FromEnvironment()
@@ -77,12 +93,22 @@ func serve(ctx context.Context) error {
 			"reconnect. Set %s and %s.\n", broker.AddressVar, broker.CertificateVar)
 	}

-	work := link.Enrolment{Inventory: inv, Identity: ident, Management: management, Broker: known}
-	server, err := link.Connect(work, work)
+	// **Which bus this mesh is on, read once** (novox/hq ADR 0116 step 5). Both clients ship; both
+	// being live is refused, because a mesh half on each is one where a declaration goes out on one
+	// and the report comes back on the other, and every component logs success while it happens.
+
+	work := link.Enrolment{Inventory: inv, Identity: ident, Broker: known,
+		OnNATS: true}
+	server, err := connectLink(ctx, inv, work, work)
 	if err != nil {
 		return err
 	}
 	defer server.Close()
+
+	// The bus's own objects, asserted on every start. **Not created once at genesis**: a stream
+	// somebody deleted, a mesh raised from a restored backup, or a bus whose data directory was
+	// replaced all have records and no objects — and a node whose consumer is missing hears nothing
+	// while everything else about it looks correct.
 	// And build results nobody was waiting for. A build triggered any other way than `build`
 	// would otherwise be reported into the void, which is the same as not reporting it.
 	server.Records(builds{inv})
@@ -136,13 +162,13 @@ func declare(ctx context.Context, args []string) error {
 		return err
 	}

-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
 	defer server.Close()

-	if err := link.Declare(ctx, server.Channel(), ident, node, raw, 15*time.Second); err != nil {
+	if err := link.Declare(ctx, server.Bus(), ident, node, raw, 15*time.Second); err != nil {
 		return err
 	}
 	fmt.Printf("sent %s a signed declaration (%d bytes)\n", node, len(raw))
@@ -249,7 +275,7 @@ func pushCommand(ctx context.Context, args []string) error {
 		return err
 	}

-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -310,7 +336,7 @@ func pushCommand(ctx context.Context, args []string) error {
 		if err != nil {
 			return err
 		}
-		if err := link.Declare(ctx, server.Channel(), ident, s.node, body, 15*time.Second); err != nil {
+		if err := link.Declare(ctx, server.Bus(), ident, s.node, body, 15*time.Second); err != nil {
 			return err
 		}
 		// After it is away, not before. A digest recorded for something that failed to send would
@@ -393,7 +419,7 @@ func pushCommand(ctx context.Context, args []string) error {
 					return declarationWith(held, open, node, plan, settings, gens, Allocating)
 				},
 				func(s readyNode, body []byte) error {
-					if err := link.Declare(ctx, server.Channel(), ident, s.node, body,
+					if err := link.Declare(ctx, server.Bus(), ident, s.node, body,
 						15*time.Second); err != nil {
 						return err
 					}
@@ -502,8 +528,14 @@ func composeEach(names []string,
 			continue
 		}
 		if len(declared.Resources) == 0 {
-			fmt.Printf("%s is assigned nothing — skipped\n", name)
-			continue
+			// Sent, not skipped (novox/hq issue 127). A node whose declaration composes to
+			// nothing may have HELD something before — the broker opening a placement gave it,
+			// say — and skipping the empty declaration leaves that last resource in force
+			// forever, re-applied by the node's own heartbeat, with no way for the mesh to say
+			// it is gone. An empty declaration is the correction: the host drops what the mesh
+			// owned and keeps what it found (the adoption envelope still rides along). A node
+			// that never held anything applies it as the no-op it is.
+			fmt.Printf("%s owns nothing now — sent so it drops what it last held\n", name)
 		}
 		sending = append(sending, readyNode{name, declared})
 	}
@@ -600,7 +632,7 @@ func sendTo(ctx context.Context, open *stores, names []string) error {
 			len(refusals), strings.Join(refusals, "\n\n"))
 	}

-	server, err := link.Connect(nil, nil)
+	server, err := connectLink(ctx, nil, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -611,7 +643,7 @@ func sendTo(ctx context.Context, open *stores, names []string) error {
 		if err != nil {
 			return err
 		}
-		if err := link.Declare(ctx, server.Channel(), ident, s.node, body, 15*time.Second); err != nil {
+		if err := link.Declare(ctx, server.Bus(), ident, s.node, body, 15*time.Second); err != nil {
 			return err
 		}
 		record, err := inv.NodeByName(ctx, s.node)
@@ -664,3 +696,122 @@ func wouldSend(ctx context.Context, open *stores,
 	}
 	return out, nil
 }
+
+// raiseTheBus asserts the streams and consumers the mesh's own traffic needs.
+//
+// **Every start, and it says what it did.** The objects are the mesh's, created by nothing else —
+// the controller is their only writer (design 25 §3) — so a mesh that came up without them is one
+// where nodes connect, authenticate, and hear nothing. Said rather than silent for the reason the
+// first line of `serve` is said: a log that is quiet on success and loud on failure reads as broken
+// when it is working.
+func raiseTheBus(ctx context.Context, inv *inventory.Inventory, address string) error {
+	js, err := broker.Dial(address)
+	if err != nil {
+		return fmt.Errorf("the mesh is on the bus at %s and this control plane cannot reach it: %w",
+			broker.BareAddress(address), err)
+	}
+	defer js.Close()
+
+	// **Its own user, before anything else.** The controller's account is created by the installer at
+	// a bootstrap password, before there is a controller to mint one — so nothing recorded a hash for
+	// it, and the first composition would leave the writer out of the file it was writing. Recorded
+	// only if absent: a credential the mesh minted since is the one that counts.
+	// **Its own user, before anything else it does here.** The controller's account is created by the
+	// installer at a bootstrap password, before there is a controller to mint one — so nothing
+	// recorded a hash for it, and the first composition would leave the writer out of the file it was
+	// writing: a bus nothing can connect to, produced by the thing connected to it. Recorded only if
+	// absent, so a restart cannot put the bootstrap credential back over a rotated one.
+	if user, password, _ := broker.CredentialIn(address); user != "" && password != "" {
+		if err := inv.SeedBusUser(ctx, inventory.BusUser{
+			Username: user, Kind: inventory.BusController,
+		}, password); err != nil {
+			return fmt.Errorf("cannot record the credential this control plane is using: %w", err)
+		}
+	}
+
+	nodes, err := inv.Nodes(ctx)
+	if err != nil {
+		return err
+	}
+	names := make([]string, 0, len(nodes))
+	for _, n := range nodes {
+		names = append(names, n.Name)
+	}
+	if err := broker.Raise(js, names); err != nil {
+		return err
+	}
+	// The work queues of the mesh's own roles (novox/hq ADR 0121). The queue before the holder,
+	// deliberately: work queues until somebody arrives to do it, so assigning a build machine a week
+	// after something started asking for builds flushes the backlog instead of having lost it.
+	// With the seats' holders, so each role's work queue gets the consumer its holder takes
+	// work from. Passed as nil until the first live raise, which left the build machine bound to a
+	// consumer nothing had created (2026-09-28).
+	holders, err := seatHolders(ctx, inv)
+	if err != nil {
+		return err
+	}
+	if err := broker.RaiseSeats(js, inventory.MeshSeats(), holders); err != nil {
+		return err
+	}
+	// And how every module hears what it consumes. Derived from the same records the user list is
+	// composed from, so a module the mesh grants a consumer's subjects has that consumer waiting.
+	// Done on every raise, not only when a credential is issued: every module moved onto this bus
+	// by the rollout was issued on the old one, and came up with nothing to bind to (2026-09-28).
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		return err
+	}
+	users, err := broker.Users(records)
+	if err != nil {
+		return err
+	}
+	hearing := 0
+	for _, p := range users {
+		consumer, needed := broker.ConsumerFor(p)
+		if !needed {
+			continue
+		}
+		if err := js.EnsureConsumer(consumer); err != nil {
+			return fmt.Errorf("how %s on %s hears what it consumes: %w", p.Module, p.Node, err)
+		}
+		hearing++
+	}
+	fmt.Printf("the bus at %s has its streams, %d machine(s) can hear a declaration, and %d module(s) "+
+		"can hear what they consume\n", broker.BareAddress(address), len(names), hearing)
+	return nil
+}
+
+// seatHolders is who holds each of the mesh's seats, by seat name: the record where a handover
+// wrote one, and the assigned module claiming the seat otherwise — the same derivation the
+// resolver makes, read from the catalogue rather than re-resolved.
+func seatHolders(ctx context.Context, inv *inventory.Inventory) (map[string]broker.Holder, error) {
+	out := map[string]broker.Holder{}
+	entries, err := inv.Catalogued(ctx)
+	if err != nil {
+		return nil, err
+	}
+	for _, e := range entries {
+		if len(e.On) == 0 {
+			continue
+		}
+		for _, c := range e.Manifest.Claims {
+			seat, known := catalogue.SeatNamed(c.Name)
+			if !known {
+				continue
+			}
+			if _, taken := out[seat.Name]; !taken {
+				out[seat.Name] = broker.Holder{Node: e.On[0], Module: e.Manifest.Module}
+			}
+		}
+	}
+	recorded, err := inv.Holdings(ctx)
+	if err != nil {
+		return nil, err
+	}
+	for _, h := range recorded {
+		if seat, known := catalogue.SeatNamed(h.Claim); known {
+			out[seat.Name] = broker.Holder{Node: h.Node, Module: h.Module}
+		}
+	}
+	return out, nil
+}
@@ -39,12 +39,14 @@ func TestOneUnresolvableNodeStillLetsTheRestBeSent(t *testing.T) {
 	}
 }

-// And a machine assigned nothing is neither sent nor a refusal — it is nothing to say.
-func TestAMachineAssignedNothingIsNotARefusal(t *testing.T) {
+// A machine whose declaration composes to nothing is SENT the empty declaration, not skipped
+// (novox/hq issue 127): it may have held something before, and only sending the empty
+// declaration tells it to drop what the mesh owned. It is never a refusal.
+func TestAnEmptyDeclarationIsSentSoTheNodeDropsWhatItHeld(t *testing.T) {
 	sending, refusals := composeEach([]string{"spare"},
 		func(string) (sendable, error) { return sendable{}, nil })
-	if len(sending) != 0 || len(refusals) != 0 {
-		t.Errorf("a machine assigned nothing was treated as something: %v / %v", sending, refusals)
+	if len(sending) != 1 || len(refusals) != 0 {
+		t.Errorf("an empty declaration must be sent, not skipped or refused: %v / %v", sending, refusals)
 	}
 }

@@ -0,0 +1,455 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/inventory"
+	"github.com/novox/mesh-controller/internal/secrets"
+)
+
+// Moving the mesh's own traffic to the bus being built (novox/hq ADR 0116 step 5).
+//
+// **The whole mesh moves at once, so there is nothing to inspect afterwards.** Every seam ships both
+// transports and every one of them chooses by a single fact; this is the step that flips it. That
+// shape is deliberate — steps 1 to 4 leave every node where it is, so the cost of being wrong stays
+// bounded until here — and it means the useful work is almost all in the checking.
+//
+// So `rollout check` is the command that matters and the one that can be run any number of times
+// against a mesh that is serving. It answers from records: what is missing, and what would happen.
+// `rollout` itself refuses unless the check is clean.
+//
+// **The old broker goes with the move, and goes last** (novox/hq ADR 0131): AMQP is not a provision,
+// so once every machine reports on the new bus its module is unassigned. Only the mesh's own traffic
+// is what moves, which is why this is survivable at all: what breaks if it goes wrong is the mesh's
+// ability to change things, not the services its modules are serving — measured on 2026-09-27, when
+// a seat emptied mid-change and the control plane looped for two hours while every service stayed up.
+
+const rolloutUsage = "rollout check | rollout mint [--again] | rollout hand <node> | rollout --confirm"
+
+func rolloutCommand(ctx context.Context, args []string) error {
+	switch {
+	case len(args) == 1 && args[0] == "check":
+		return rolloutCheck(ctx)
+	case len(args) == 1 && args[0] == "mint":
+		return rolloutMint(ctx, false)
+	case len(args) == 2 && args[0] == "hand":
+		return rolloutHand(ctx, args[1])
+	case len(args) == 2 && args[0] == "mint" && args[1] == "--again":
+		// Every credential minted afresh, whether or not one exists — for a mint that was wrong
+		// before anything was pushed. Afterwards nothing that received the old one still works,
+		// which is fine exactly when nothing received it.
+		return rolloutMint(ctx, true)
+	case len(args) == 1 && args[0] == "--confirm":
+		return errors.New(
+			"the rollout itself is not built yet: `rollout check` answers whether it could run, and " +
+				"what is missing. Moving every node at once is the one step with nothing to inspect " +
+				"afterwards, so it is not being written before the check it depends on has been run " +
+				"against a real mesh")
+	default:
+		return errors.New(rolloutUsage)
+	}
+}
+
+// rolloutCheck says whether the mesh could move, and what would happen if it did.
+func rolloutCheck(ctx context.Context) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	state, err := readinessOf(ctx, inv)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println("the bus this mesh would move to")
+	if state.TheBus == "" {
+		fmt.Printf("  nothing names one (%s is unset)\n", broker.NATSVar)
+	} else {
+		standing := "not answering"
+		if state.ServerStanding {
+			standing = "answering"
+		}
+		fmt.Printf("  %s — %s\n", state.TheBus, standing)
+	}
+	fmt.Println()
+
+	fmt.Println("what would move")
+	for _, step := range broker.WhatMoves(state) {
+		fmt.Printf("  %s\n", step)
+	}
+	fmt.Println()
+
+	why := notReadyOf(state)
+	if len(why) == 0 {
+		fmt.Println("nothing is missing: this mesh could move its bus.")
+		fmt.Println()
+		fmt.Println("Read `what would move` above once more before running it. Every node moves at the")
+		fmt.Println("same moment and there is no half-moved state to look at afterwards.")
+		return nil
+	}
+	fmt.Printf("not ready — %d thing(s) to do first:\n", len(why))
+	for i, w := range why {
+		fmt.Printf("  %d. %s\n", i+1, w)
+	}
+	return nil
+}
+
+// readinessOf gathers what the mesh knows about its own ability to move.
+//
+// Reads and one dial, and nothing is written. Safe to run on a mesh that is serving, which is the
+// point: the answer is only useful if it can be had without committing to anything.
+func readinessOf(ctx context.Context, inv *inventory.Inventory) (broker.Readiness, error) {
+	state := broker.Readiness{
+		Credentialled:       map[string]bool{},
+		ModuleCredentialled: map[string]bool{},
+		// The old broker keeps its other clients on this installation, and saying so is how the plan
+		// stops reading as a retirement.
+	}
+
+	address, _, err := broker.OnNATS()
+	if err != nil {
+		return state, err
+	}
+	state.TheBus = address
+	if address != "" {
+		// One dial, briefly. "Is it answering" is the one fact records cannot hold, and a mesh about
+		// to move onto a server that is not there should hear it here rather than afterwards.
+		//
+		// **Dialled the way the mesh dials it** — credential and pin — because a bare connect to a
+		// bus that requires TLS and a user fails at the handshake, and the check then reported a
+		// standing server as absent (seen live, 2026-09-28).
+		if js, err := broker.Dial(address, nats.Timeout(5*time.Second)); err == nil {
+			state.ServerStanding = true
+			js.Close()
+		}
+	}
+
+	nodes, err := inv.Nodes(ctx)
+	if err != nil {
+		return state, err
+	}
+	kept, err := inv.BusUsers(ctx)
+	if err != nil {
+		return state, err
+	}
+	shelf, err := inv.Catalogue(ctx)
+	if err != nil {
+		return state, err
+	}
+
+	for _, n := range nodes {
+		state.Nodes = append(state.Nodes, n.Name)
+		_, has := kept[broker.Principal{Kind: broker.KindNode, Node: n.Name}.Username()]
+		state.Credentialled[n.Name] = has
+
+		assigned, err := inv.Assigned(ctx, n.Name)
+		if err != nil {
+			return state, err
+		}
+		for _, module := range assigned {
+			m, known := shelf[module]
+			if !known {
+				continue
+			}
+			// The machine that holds the bus seat is the one that would be sent the user list.
+			if m.BusUsers != "" && m.ClaimsSeat("mesh-broker") {
+				state.Holder = n.Name
+				state.AccountsComposed = wasSentTheUserList(ctx, inv, n.Name)
+			}
+			// A module that never speaks needs no credential, so it is not counted as missing one.
+			if !speaksOnTheBus(m) {
+				continue
+			}
+			named := n.Name + "/" + module
+			state.Modules = append(state.Modules, named)
+			_, hasOne := kept[broker.Principal{
+				Kind: broker.KindModule, Node: n.Name, Module: module,
+			}.Username()]
+			state.ModuleCredentialled[named] = hasOne
+		}
+	}
+	return state, nil
+}
+
+// speaksOnTheBus says whether a module reaches the bus at all.
+//
+// A third of the catalogue never does (novox/hq ADR 0120), and counting those as missing a credential
+// would bury the ones that matter under a list nobody can act on.
+func speaksOnTheBus(m catalogue.Manifest) bool {
+	return len(m.Emits) > 0 || len(m.Consumes) > 0 || len(m.Tools) > 0 ||
+		len(m.DefinesSeats) > 0 || len(m.Uses) > 0 || len(m.Claims) > 0
+}
+
+// wasSentTheUserList says whether the machine holding the bus has had a declaration since the user
+// list became part of one.
+//
+// Read from what the mesh recorded sending rather than asked of the machine: a machine that is away
+// has still been sent it, and this question is about whether the mesh did its part.
+func wasSentTheUserList(ctx context.Context, inv *inventory.Inventory, node string) bool {
+	digest, err := inv.Outstanding(ctx, node)
+	return err == nil && strings.TrimSpace(digest) != ""
+}
+
+// notReadyOf is the readiness reasoning, named here so a test can reach it without the command's
+// printing. The reasoning itself is the broker package's, where it is pure.
+func notReadyOf(state broker.Readiness) []string { return broker.NotReady(state) }
+
+// rolloutMint gives every principal the new bus will have a credential it does not yet have, and
+// puts each where its owner reads it (novox/hq design 28, task 5.2): a machine's as a membership
+// sealed into its declaration, a module's as its broker secret, the control plane's own as its
+// `bus` secret. Idempotent: what already has a hash is left alone, so running it again is harmless.
+//
+// **Before anything moves, and it is what makes moving possible.** A machine moved without a
+// credential cannot come back, and afterwards there is no bus to tell it anything over — which is
+// why `rollout check` refuses until this has run. The bus's address is worked out here, from where
+// the module that provides it is assigned, rather than read from this process's environment: this
+// process is still on the old bus when this runs, and must be.
+func rolloutMint(ctx context.Context, again bool) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	known, err := broker.FromEnvironment()
+	if err != nil {
+		return fmt.Errorf("the bus's certificate is not known to this process, and every membership "+
+			"must carry its fingerprint: %w", err)
+	}
+	shelf, err := inv.Catalogue(ctx)
+	if err != nil {
+		return err
+	}
+	entries, err := inv.Catalogued(ctx)
+	if err != nil {
+		return err
+	}
+	var busNode, controllerNode string
+	for _, e := range entries {
+		switch {
+		case e.Manifest.ClaimsSeat("mesh-broker") && providesBus(e.Manifest) && len(e.On) > 0:
+			busNode = e.On[0]
+		case e.Manifest.Module == "mesh-controller" && len(e.On) > 0:
+			controllerNode = e.On[0]
+		}
+	}
+	if busNode == "" {
+		return errors.New("no assigned module provides mesh-bus and claims mesh-broker, so there is no " +
+			"bus to mint credentials for — register and assign it first")
+	}
+	onNetwork, err := whereEveryoneIs(ctx, inv, shelf)
+	if err != nil {
+		return err
+	}
+	busHost := onNetwork[busNode]
+	if busHost == "" {
+		// **The hub is not in that map.** The machine that took over the tunnel is where the current
+		// bus already answers, and every machine dials it at the address the mesh handed them — so
+		// when the new bus runs on the same machine, that address is the one to tell them, with the
+		// new port. Found live: the control node is the hub, and the map lists the machines placed
+		// around it.
+		// The host alone: no scheme (BareAddress adds one where none was, which is the wrong
+		// direction here — every URL built below adds its own) and no port.
+		_, _, host := broker.CredentialIn(known.Address)
+		if host == "" {
+			host = known.Address
+		}
+		if _, after, hasScheme := strings.Cut(host, "://"); hasScheme {
+			host = after
+		}
+		host = strings.TrimSpace(host)
+		if i := strings.LastIndex(host, ":"); i > 0 && !strings.Contains(host[i:], "]") {
+			host = host[:i]
+		}
+		if host == "" {
+			return fmt.Errorf("%s runs the new bus and has no address on the private network, and the "+
+				"current bus's address is unknown too, so no machine could be told where it is", busNode)
+		}
+		busHost = host
+	}
+	busAddress := busHost + ":4222"
+
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		return err
+	}
+	users, err := broker.Users(records)
+	if err != nil {
+		return err
+	}
+	kept, err := inv.BusUsers(ctx)
+	if err != nil {
+		return err
+	}
+	hashes := make(map[string]string, len(kept))
+	for name, u := range kept {
+		hashes[name] = u.PasswordHash
+	}
+	_, missing := broker.WithPasswords(users, hashes)
+	wanted := map[string]bool{}
+	for _, m := range missing {
+		wanted[m] = true
+	}
+
+	var machines, modules, skipped int
+	for _, p := range users {
+		if !again && !wanted[p.Username()] {
+			continue
+		}
+		switch p.Kind {
+		case broker.KindController:
+			if controllerNode == "" {
+				return errors.New("the control plane is not assigned anywhere, so its credential has nowhere to go")
+			}
+			password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: p.Username(), Kind: inventory.BusController})
+			if err != nil {
+				return err
+			}
+			url := "nats://" + p.Username() + ":" + password + "@" + busAddress
+			if err := inv.AcceptSecretForModule(ctx, controllerNode, "mesh-controller", "bus", url); err != nil {
+				return fmt.Errorf("the control plane's credential is minted and could not be sealed to %s: %w", controllerNode, err)
+			}
+			fmt.Printf("control plane: credential minted, sealed to %s as its `bus` secret\n", controllerNode)
+
+		case broker.KindNode:
+			password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: p.Username(), Kind: inventory.BusNode, Node: p.Node})
+			if err != nil {
+				return err
+			}
+			membership, _ := json.Marshal(map[string]string{
+				"broker": busAddress, "fingerprint": known.Fingerprint, "password": password, "transport": "nats",
+			})
+			key, err := inv.SealingKeyOf(ctx, p.Node)
+			if err != nil {
+				return fmt.Errorf("%s has no sealing key, so its membership cannot be sealed to it: %w", p.Node, err)
+			}
+			sealed, err := secrets.Seal(key, membership)
+			if err != nil {
+				return err
+			}
+			if err := inv.PutBusMembership(ctx, p.Node, sealed); err != nil {
+				return err
+			}
+			machines++
+
+		case broker.KindModule:
+			if p.Module == "mesh-controller" {
+				// The control plane is a module too, and its `broker` secret is the old bus's
+				// credential it is still using while this runs. Writing the new bus's blob there
+				// cut the mesh off from its own old bus mid-move (2026-09-28). Its new-bus credential
+				// is the controller principal's `bus` secret above; nothing else is needed here.
+				skipped++
+				continue
+			}
+			m, inShelf := shelf[p.Module]
+			if !inShelf {
+				skipped++
+				continue
+			}
+			if _, reads := m.OwnSecrets["broker"]; !reads {
+				fmt.Printf("  %s on %s speaks on the bus but declares no `broker` secret to receive a credential in; skipped\n", p.Module, p.Node)
+				skipped++
+				continue
+			}
+			password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: p.Username(), Kind: inventory.BusModule, Node: p.Node, Module: p.Module})
+			if err != nil {
+				return err
+			}
+			if err := issueWith(ctx, inv, m, p.Node, "", known, busAddress, p.Username(), password); err != nil {
+				return err
+			}
+			modules++
+
+		default:
+			skipped++
+		}
+	}
+	fmt.Printf("minted for %d machine(s) and %d module runtime(s); %d skipped; the bus is at %s\n",
+		machines, modules, skipped, busAddress)
+	fmt.Println("  each machine's membership and each module's credential arrive with the next push of its machine;")
+	fmt.Println("  push the machine running the bus first, so the bus stands with its user list before anything dials it")
+	return nil
+}
+
+// providesBus is whether a manifest provides the mesh's bus.
+func providesBus(m catalogue.Manifest) bool {
+	for _, o := range m.Provides {
+		if o.Name == "mesh-bus" {
+			return true
+		}
+	}
+	return false
+}
+
+// rolloutHand mints a machine its credential for the new bus afresh and prints its membership
+// once, for an operator to carry by hand — the rescue for a machine that cannot be reached over
+// any bus: rotated while it still held the old password, or reachable only by ssh. The plaintext
+// exists on this terminal and then only where it is written; the store keeps the hash, and the
+// sealed copy in the machine's declaration is replaced too, so the next push says the same.
+func rolloutHand(ctx context.Context, node string) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	known, err := broker.FromEnvironment()
+	if err != nil {
+		return fmt.Errorf("the bus's certificate is not known to this process: %w", err)
+	}
+	busAddress, _, err := broker.OnNATS()
+	if err != nil {
+		return err
+	}
+	if busAddress == "" {
+		return errors.New("this control plane is not on the new bus, so there is no membership to hand out")
+	}
+	_, _, bare := broker.CredentialIn(busAddress)
+	if _, after, has := strings.Cut(bare, "://"); has {
+		bare = after
+	}
+	if _, err := inv.NodeByName(ctx, node); err != nil {
+		return err
+	}
+	p := broker.Principal{Kind: broker.KindNode, Node: node}
+	password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: p.Username(), Kind: inventory.BusNode, Node: node})
+	if err != nil {
+		return err
+	}
+	membership, _ := json.Marshal(map[string]string{
+		"broker": bare, "fingerprint": known.Fingerprint, "password": password, "transport": "nats",
+	})
+	key, err := inv.SealingKeyOf(ctx, node)
+	if err != nil {
+		return err
+	}
+	sealed, err := secrets.Seal(key, membership)
+	if err != nil {
+		return err
+	}
+	if err := inv.PutBusMembership(ctx, node, sealed); err != nil {
+		return err
+	}
+	// The one line of output is the membership itself, so it can be piped to the machine without
+	// being read on the way. Everything else goes to stderr.
+	fmt.Fprintf(os.Stderr, "%s's credential is minted afresh. Write this to %s on it and restart its host; "+
+		"then push the machine running the bus so the user list carries the new hash.\n",
+		node, catalogue.BusMembershipPath)
+	fmt.Println(string(membership))
+	return nil
+}
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/inventory"
+)
+
+// Whether a mesh could move its bus, read from a real store.
+//
+// The readiness reasoning has its own tests; this is about the gathering — that the question is
+// answered from what the mesh actually holds, on a store with machines and modules in it, without
+// writing anything.
+
+func TestReadinessIsGatheredFromWhatTheMeshHolds(t *testing.T) {
+	inv := inventory.ForTest(t)
+	ctx := context.Background()
+
+	// A mesh mid-change: two machines, the bus module on one of them, a module that speaks and a
+	// module that never does.
+	for _, m := range []catalogue.Manifest{
+		{Module: "nats", Version: "1", BusUsers: "/var/lib/nats-module/conf/accounts.conf",
+			Claims: []catalogue.Claim{{Name: "mesh-broker", Scope: catalogue.ScopeMesh}}},
+		{Module: "gitea", Version: "1", Tools: []string{"repo_create"}},
+		{Module: "wallpaper", Version: "1"},
+	} {
+		if err := inv.RegisterModule(ctx, m, inventory.Source{Repository: "/r"}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, n := range []string{"anchor", "laptop"} {
+		if _, err := inv.AddNode(ctx, n); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, a := range [][2]string{{"anchor", "nats"}, {"anchor", "gitea"}, {"laptop", "wallpaper"}} {
+		if _, err := inv.Assign(ctx, a[0], a[1]); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	state, err := readinessOf(ctx, inv)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if state.Holder != "anchor" {
+		t.Errorf("the machine holding the bus reads as %q", state.Holder)
+	}
+	if len(state.Nodes) != 2 {
+		t.Errorf("machines read as %v", state.Nodes)
+	}
+	// **A module that never speaks is not counted as missing a credential.** A third of the catalogue
+	// never reaches the bus, and listing those would bury the ones that matter.
+	for _, m := range state.Modules {
+		if strings.HasSuffix(m, "/wallpaper") {
+			t.Errorf("a module that never speaks was counted: %v", state.Modules)
+		}
+	}
+	if len(state.Modules) != 2 {
+		t.Errorf("modules that speak read as %v; expected the bus module and the one with a tool",
+			state.Modules)
+	}
+
+	// Nothing has been minted, so it is not ready — and it says so about each machine by name.
+	why := notReadyOf(state)
+	if len(why) == 0 {
+		t.Fatal("a mesh where nothing has a credential was reported ready to move")
+	}
+	said := strings.Join(why, "\n")
+	for _, name := range []string{"anchor", "laptop"} {
+		if !strings.Contains(said, name) {
+			t.Errorf("the refusal does not name %s: %s", name, said)
+		}
+	}
+
+	// Mint for one machine and it drops out of the complaint, which is how somebody works through it.
+	if _, err := inv.MintBusPassword(ctx, inventory.BusUser{
+		Username: "node.laptop", Kind: inventory.BusNode, Node: "laptop",
+	}); err != nil {
+		t.Fatal(err)
+	}
+	state, err = readinessOf(ctx, inv)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !state.Credentialled["laptop"] {
+		t.Error("a machine that was minted a credential still reads as having none")
+	}
+}
@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"slices"
 	"sort"
 	"strings"
 	"text/tabwriter"
@@ -43,15 +44,16 @@ type seatRow struct {
 // overview would make the one thing the overview is for — what does this mesh have — quietly
 // incomplete.
 func seatsHeld(seats []catalogue.Seat, held []catalogue.Held) ([]seatRow, []catalogue.Held) {
-	defined := map[string]bool{}
 	rows := make([]seatRow, 0, len(seats))
 	for _, s := range seats {
-		defined[s.Name] = true
 		row := seatRow{Seat: s.Name, Scope: s.Scope, Delivers: s.Delivers, Decision: s.Decision,
 			Holders: []seatHolder{}}
 		seen := map[seatHolder]bool{}
 		for _, h := range held {
-			if h.Claim != s.Name || h.Scope != s.Scope {
+			// Resolve the held claim to a seat rather than comparing names, so a record naming a
+			// seat's former name groups under it after a rename (novox/hq ADR 0122).
+			hs, ok := catalogue.SeatNamed(h.Claim)
+			if !ok || hs.Name != s.Name || h.Scope != s.Scope {
 				continue
 			}
 			holder := seatHolder{Node: h.Node, Module: h.Module}
@@ -70,7 +72,8 @@ func seatsHeld(seats []catalogue.Seat, held []catalogue.Held) ([]seatRow, []cata
 	}
 	var outside []catalogue.Held
 	for _, h := range held {
-		if !defined[h.Claim] {
+		// Outside the set only if it resolves to no seat at all — a former name still resolves.
+		if _, ok := catalogue.SeatNamed(h.Claim); !ok {
 			outside = append(outside, h)
 		}
 	}
@@ -83,6 +86,120 @@ func seatsHeld(seats []catalogue.Seat, held []catalogue.Held) ([]seatRow, []cata
 	return rows, outside
 }

+// seatCommand changes the set — the whole point of it being data (novox/hq ADR 0122) — and, since
+// ADR 0131, changes who holds a seat.
+func seatCommand(ctx context.Context, args []string) error {
+	if len(args) == 3 && args[0] == "rename" {
+		from, to := args[1], args[2]
+		open, err := openStores(ctx)
+		if err != nil {
+			return err
+		}
+		defer open.Close()
+		if err := open.inventory.RenameSeat(ctx, from, to); err != nil {
+			return err
+		}
+		fmt.Printf("%s is now %s — its former name still resolves, so nothing is rebuilt, "+
+			"re-registered or frozen (novox/hq ADR 0122)\n", from, to)
+		return nil
+	}
+	if len(args) == 3 && args[1] == "--to" {
+		return handOver(ctx, args[0], args[2])
+	}
+	return fmt.Errorf("seat rename <from> <to>  |  seat <name> --to <node>/<module>")
+}
+
+// handOver makes one assignment the holder of a seat, as one act, so the seat is never without a
+// holder in between (novox/hq ADR 0131, design 28 task 5.3). The control plane finds its own bus
+// through one of these seats; the day it was left empty mid-change is why this exists.
+//
+// Everything that could make the new holder wrong is refused here, before the row is written: the
+// seat must exist, the assignment must exist, and the module must be able to hold the seat —
+// claim it at its scope and provide what it delivers, judged against the store's row. What is
+// **not** checked is whether the module is running yet: that is what `push` confirms afterwards,
+// and refusing to record a handover to a module the node has not started would make the handover
+// impossible to do before the switch instead of as the switch.
+func handOver(ctx context.Context, seatName, to string) error {
+	nodeName, module, ok := strings.Cut(to, "/")
+	if !ok || nodeName == "" || module == "" {
+		return fmt.Errorf("the new holder is named <node>/<module>, not %q", to)
+	}
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	seat, known := catalogue.SeatNamed(seatName)
+	if !known {
+		return fmt.Errorf("%q is not a seat this mesh defines — `seats` lists them", seatName)
+	}
+	assigned, err := inv.Assigned(ctx, nodeName)
+	if err != nil {
+		return err
+	}
+	if !slices.Contains(assigned, module) {
+		return fmt.Errorf("%s is not assigned to %s, so it cannot hold anything there — "+
+			"`assign %s %s` first", module, nodeName, nodeName, module)
+	}
+	entries, err := inv.Catalogued(ctx)
+	if err != nil {
+		return err
+	}
+	var m *catalogue.Manifest
+	for i := range entries {
+		if entries[i].Manifest.Module == module {
+			m = &entries[i].Manifest
+		}
+	}
+	if m == nil {
+		return fmt.Errorf("%s is assigned but not in the catalogue, which should not happen", module)
+	}
+	var was string
+	holdings, err := inv.Holdings(ctx)
+	if err != nil {
+		return err
+	}
+	for _, h := range holdings {
+		if hs, ok := catalogue.SeatNamed(h.Claim); ok && hs.Name == seat.Name {
+			was = h.Node
+		}
+	}
+
+	// **Recording who already holds the seat is not making a new holder, and is not judged like
+	// one.** On a mesh that predates the record, the first handover has to begin by writing down
+	// the standing holder — otherwise the next holder cannot be assigned beside it, because two
+	// eligible claimants with nothing on record are refused. That standing holder may no longer
+	// satisfy what the seat delivers (the row moved under it, on purpose, as ADR 0131's first step),
+	// and it holds regardless: derivation never read that column. So when nothing is on record and
+	// the named assignment is the one holding by derivation, only the claim itself is checked here.
+	// Every *change* of holder is judged in full.
+	claimsIt := false
+	for _, c := range m.Claims {
+		if cs, ok := catalogue.SeatNamed(c.Name); ok && cs.Name == seat.Name && c.At() == seat.Scope {
+			claimsIt = true
+		}
+	}
+	if was == "" && claimsIt {
+		fmt.Printf("nothing was on record for %s; recording %s on %s as its standing holder\n",
+			seat.Name, module, nodeName)
+	} else if err := catalogue.CanHold(*m, seat); err != nil {
+		return fmt.Errorf("%s cannot hold %s: %w", module, seat.Name, err)
+	}
+	if err := inv.HoldSeat(ctx, seat.Name, seat.Scope, nodeName, module); err != nil {
+		return err
+	}
+	fmt.Printf("%s is held by %s on %s\n", seat.Name, module, nodeName)
+	if was != "" && was != nodeName {
+		fmt.Printf("  `push %s` and `push %s` send both machines what changed\n", was, nodeName)
+	} else {
+		fmt.Printf("  `push %s` sends the machine what changed; every other machine that reads the "+
+			"seat is re-declared by `push --behind`\n", nodeName)
+	}
+	return nil
+}
+
 func seatsCommand(ctx context.Context, args []string) error {
 	set := flag.NewFlagSet("seats", flag.ContinueOnError)
 	asJSON := set.Bool("json", false, "the same, as JSON")
@@ -35,13 +35,13 @@ func TestEverySeatIsListedIncludingTheOnesNobodyHolds(t *testing.T) {

 func TestANodeSeatListsEveryMachineHoldingIt(t *testing.T) {
 	rows, _ := seatsHeld(catalogue.Seats(), []catalogue.Held{
-		{Claim: "the-packet-filter", Scope: catalogue.ScopeNode, Node: "node2", Module: "nftables"},
-		{Claim: "the-packet-filter", Scope: catalogue.ScopeNode, Node: "anchor", Module: "nftables"},
+		{Claim: "node-packet-filter", Scope: catalogue.ScopeNode, Node: "node2", Module: "nftables"},
+		{Claim: "node-packet-filter", Scope: catalogue.ScopeNode, Node: "anchor", Module: "nftables"},
 		// Resolved twice, reported once: a machine is one holder however many passes saw it.
-		{Claim: "the-packet-filter", Scope: catalogue.ScopeNode, Node: "anchor", Module: "nftables"},
+		{Claim: "node-packet-filter", Scope: catalogue.ScopeNode, Node: "anchor", Module: "nftables"},
 	})
 	for _, r := range rows {
-		if r.Seat != "the-packet-filter" {
+		if r.Seat != "node-packet-filter" {
 			continue
 		}
 		if len(r.Holders) != 2 || r.Holders[0].Node != "anchor" || r.Holders[1].Node != "node2" {
@@ -38,6 +38,12 @@ func (s sendable) Body() ([]byte, error) {
 	if s.Adoption != nil {
 		envelope["adoption"] = s.Adoption
 	}
+	// An empty declaration is deliberate here — the node owns nothing the mesh put there
+	// (novox/hq issue 127) — and the host refuses an empty body unless it is told the emptiness
+	// is meant, so a truncated or mis-composed body is never mistaken for "own nothing".
+	if len(s.Resources) == 0 {
+		envelope["owns_nothing"] = true
+	}
 	return json.Marshal(envelope)
 }

@@ -355,3 +355,25 @@ func TestTheMachineSideOfAMappingIsMovedEverywhereTheNumberIsUsed(t *testing.T)
 		t.Fatalf("the consumer is told the forge answers on %v", told)
 	}
 }
+
+func TestAnEmptyDeclarationSaysOwnsNothing(t *testing.T) {
+	// The host refuses an empty body unless told the emptiness is meant (novox/hq issue 127).
+	body, err := sendable{}.Body()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var env map[string]any
+	if err := json.Unmarshal(body, &env); err != nil {
+		t.Fatal(err)
+	}
+	if env["owns_nothing"] != true {
+		t.Fatalf("an empty declaration must mark owns_nothing; got %v", env)
+	}
+	// A declaration with resources does not carry the marker.
+	body, _ = sendable{Resources: []map[string]any{{"id": "x"}}}.Body()
+	var env2 map[string]any
+	_ = json.Unmarshal(body, &env2)
+	if _, present := env2["owns_nothing"]; present {
+		t.Fatalf("a non-empty declaration must not mark owns_nothing; got %v", env)
+	}
+}
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"time"

+	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/identity"
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/licences"
@@ -72,6 +73,14 @@ func migrate(ctx context.Context) error {
 		}
 		fmt.Printf("provided %s\n", m.Module)
 	}
+	// The seats the mesh ships with, into the table that now holds the set (novox/hq ADR 0122).
+	// Idempotent: fills an empty table on first boot, adds a seat a release ships, and leaves an
+	// operator's changes in the table as they are.
+	added, err := inv.SeedSeats(ctx, catalogue.DefaultSeats())
+	if err != nil {
+		return err
+	}
+	fmt.Printf("seeded %d seat(s)\n", added)
 	return nil
 }

@@ -85,6 +94,18 @@ func openInventory(ctx context.Context) (*inventory.Inventory, error) {
 		inv.Close()
 		return nil, err
 	}
+	// Load the seat set from the store, so the control plane reads the set as data rather than as
+	// the slice it was compiled with (novox/hq ADR 0122). A store not yet seeded — or one whose
+	// seat table a migration has not reached — returns nothing, and UseSeats leaves the compiled
+	// defaults in force: the set is never emptied by a read that found nothing, which would refuse
+	// every claim. So this can only ever replace the defaults with what the mesh actually holds.
+	if seats, err := inv.Seats(ctx); err == nil {
+		catalogue.UseSeats(seats)
+	}
+	// And the former names, so a reference to a seat's old name resolves after a rename (ADR 0122).
+	if aliases, err := inv.Aliases(ctx); err == nil {
+		catalogue.UseAliases(aliases)
+	}
 	return inv, nil
 }

@@ -6,7 +6,9 @@ import (
 	"flag"
 	"fmt"
 	"strings"
+	"time"

+	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/link"
 )
@@ -218,3 +220,165 @@ func notNow(err error) error {
 	}
 	return err
 }
+
+// SourceMoved is the forge announcing a merge: every module recorded as built from that
+// repository and branch is marked as moved to the merge commit, and built — bases first, so a
+// module that stands on another's artifact is built after it and not against the old one
+// (novox/hq 04-ISSUES/131). Nothing is pushed here: what a finished build does to the machines
+// running the module is the upgrade's decision, taken when the catalogue announces it.
+func (f following) SourceMoved(ctx context.Context, m link.SourceMoved) error {
+	inv := f.open.inventory
+	entries, err := inv.Catalogued(ctx)
+	if err != nil {
+		return notNow(err)
+	}
+	var moved []inventory.Entry
+	for _, e := range entries {
+		if !sourceIs(e.Source, m) {
+			continue
+		}
+		if e.Source.BuiltFrom == m.Commit {
+			continue
+		}
+		// **A merge older than the last look at the source is history, not a move.** The forge
+		// announces what it finds merged, and an old merge surfacing late would otherwise move the
+		// recorded head backwards and rebuild everything built from that repository, once per old
+		// merge (2026-09-28).
+		if isHistory(m.MergedAt, e.Source.Seen) {
+			continue
+		}
+		if err := inv.SourceMoved(ctx, e.Manifest.Module, m.Commit); err != nil {
+			return notNow(err)
+		}
+		moved = append(moved, e)
+	}
+	if len(moved) == 0 {
+		fmt.Printf("%s/%s merged into %s (%.8s); nothing the mesh holds is built from it\n",
+			m.Owner, m.Repo, m.Base, m.Commit)
+		return nil
+	}
+	against, err := inv.BuiltAgainst(ctx)
+	if err != nil {
+		return notNow(err)
+	}
+	ordered := orderByBases(moved, against)
+	names := make([]string, 0, len(ordered))
+	for _, e := range ordered {
+		names = append(names, e.Manifest.Module)
+	}
+	fmt.Printf("%s/%s merged into %s (%.8s); building %s\n",
+		m.Owner, m.Repo, m.Base, m.Commit, strings.Join(names, ", "))
+	var failed []string
+	for _, e := range ordered {
+		source := buildSource{Repository: e.Source.Repository, Seat: e.Source.Seat}
+		if err := buildOne(ctx, source, e.Source.Path, e.Source.Ref, 20*time.Minute); err != nil {
+			fmt.Printf("  %s: %v\n", e.Manifest.Module, err)
+			failed = append(failed, e.Manifest.Module)
+			// A base that failed is a reason to stop: what stands on it would be built against
+			// the old one, and report success (novox/hq 04-ISSUES/131).
+			if standsOn(ordered, e.Manifest.Module, against) {
+				fmt.Printf("  stopping: %s is a base of what was still to build\n", e.Manifest.Module)
+				break
+			}
+		}
+	}
+	if len(failed) > 0 {
+		fmt.Printf("%d of %d not built: %s\n", len(failed), len(ordered), strings.Join(failed, ", "))
+	}
+	return nil
+}
+
+// sourceIs is whether a recorded source is the repository and branch a merge announced. A source on
+// the git seat is recorded as its path on the forge; one elsewhere as the URL it was cloned from.
+// An empty recorded ref is the repository's default branch, which is what a merge into the base
+// branch of the forge's default means.
+func sourceIs(s inventory.Source, m link.SourceMoved) bool {
+	want := strings.ToLower(m.Owner + "/" + m.Repo)
+	repo := strings.ToLower(strings.TrimSuffix(s.Repository, ".git"))
+	matches := repo == want || strings.HasSuffix(repo, "/"+want) ||
+		(m.CloneURL != "" && strings.EqualFold(strings.TrimSuffix(s.Repository, ".git"), strings.TrimSuffix(m.CloneURL, ".git")))
+	if !matches {
+		return false
+	}
+	return s.Ref == "" || s.Ref == m.Base
+}
+
+// orderByBases is the entries with every base before what stands on it: a module whose build stood
+// on another's artifact comes after that module. Entries outside the set are not waited for — they
+// are not being rebuilt. Stable for what has no order between it.
+//
+// `against` is what each module's newest build stood on (inventory.BuiltAgainst): the edges are
+// derived from builds, not declared, because a recorded manifest no longer carries `build.on`.
+func orderByBases(entries []inventory.Entry, against map[string][]string) []inventory.Entry {
+	inSet := map[string]bool{}
+	for _, e := range entries {
+		inSet[e.Manifest.Module] = true
+	}
+	var out []inventory.Entry
+	placed := map[string]bool{}
+	var place func(e inventory.Entry, seen map[string]bool)
+	place = func(e inventory.Entry, seen map[string]bool) {
+		name := e.Manifest.Module
+		if placed[name] || seen[name] {
+			return
+		}
+		seen[name] = true
+		for _, base := range entries {
+			if base.Manifest.Module != name && inSet[base.Manifest.Module] && standsOnModule(e, base.Manifest.Module, against) {
+				place(base, seen)
+			}
+		}
+		placed[name] = true
+		out = append(out, e)
+	}
+	for _, e := range entries {
+		place(e, map[string]bool{})
+	}
+	return out
+}
+
+// standsOn is whether anything in the set is built on the named module's artifacts.
+func standsOn(entries []inventory.Entry, module string, against map[string][]string) bool {
+	for _, e := range entries {
+		if standsOnModule(e, module, against) {
+			return true
+		}
+	}
+	return false
+}
+
+// standsOnModule is whether an entry's build stood on the named module: by what its newest build
+// recorded it was handed (`artifact-store://<module>/<artifact>@…`, the module's own artifact), or
+// — for a module registered from a manifest and not yet built — by the base its manifest names.
+func standsOnModule(e inventory.Entry, module string, against map[string][]string) bool {
+	if e.Manifest.Module == module {
+		return false
+	}
+	if e.Manifest.Build != nil {
+		for _, on := range e.Manifest.Build.On {
+			if on.Module == module {
+				return true
+			}
+		}
+	}
+	prefix := catalogue.ArtifactStoreScheme + module + "/"
+	for _, ref := range against[e.Manifest.Module] {
+		if strings.HasPrefix(ref, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// isHistory is whether a merge made at mergedAt predates the last time the source was seen. A merge
+// with no time on it is taken as news: refusing it would silence a forge that says less.
+func isHistory(mergedAt string, seen time.Time) bool {
+	if mergedAt == "" || seen.IsZero() {
+		return false
+	}
+	at, err := time.Parse(time.RFC3339, mergedAt)
+	if err != nil {
+		return false
+	}
+	return at.Before(seen)
+}
@@ -1,19 +1,22 @@
 module github.com/novox/mesh-controller

-go 1.25.0
+go 1.26.0

 require (
 	github.com/jackc/pgx/v5 v5.10.0
-	github.com/rabbitmq/amqp091-go v1.14.0
-	golang.org/x/crypto v0.55.0
+	github.com/nats-io/nats.go v1.54.0
+	golang.org/x/crypto v0.57.0
 )

 require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
-	golang.org/x/net v0.57.0 // indirect
-	golang.org/x/sync v0.22.0 // indirect
-	golang.org/x/sys v0.47.0 // indirect
-	golang.org/x/text v0.41.0 // indirect
+	github.com/klauspost/compress v1.20.0 // indirect
+	github.com/nats-io/nkeys v0.4.16 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/net v0.58.0 // indirect
+	golang.org/x/sync v0.23.0 // indirect
+	golang.org/x/sys v0.48.0 // indirect
+	golang.org/x/text v0.42.0 // indirect
 )
@@ -9,27 +9,31 @@ github.com/jackc/pgx/v5 v5.10.0 h1:VhSvgU2jSli8o3AqIEOTJr7rZwAEUVo4E4XhR94Zfr0=
 github.com/jackc/pgx/v5 v5.10.0/go.mod h1:mal1tBGAFfLHvZzaYh77YS/eC6IX9OWbRV1QIIM0Jn4=
 github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
 github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
+github.com/klauspost/compress v1.20.0 h1:a3C1ke2ohxFymNlb2HWAHjDeKCI90scRskErZkR0ezA=
+github.com/klauspost/compress v1.20.0/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
+github.com/nats-io/nats.go v1.54.0 h1:vsXoOxjHp/GmPUN+EcI7uOf/uB+iAP+kEsAFNQN0yzA=
+github.com/nats-io/nats.go v1.54.0/go.mod h1:y+DZoD1oBOYfZTU681eTUiUjI0vbqYGixNVFHcjHJ0k=
+github.com/nats-io/nkeys v0.4.16 h1:rd5oAuLOb8mnAycB0xleuEBNS1pVVnN0fv/FF34Eypg=
+github.com/nats-io/nkeys v0.4.16/go.mod h1:llLgWoI0o4z/Q57q2R1kHfmocyhGV6VG/U18Glg1Afs=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rabbitmq/amqp091-go v1.14.0 h1:RSaT7aOKt/OrkVUyswPDW29lnRz9psuGmfZFBmLqLek=
-github.com/rabbitmq/amqp091-go v1.14.0/go.mod h1:Hy4jKW5kQART1u+JkDTF9YYOQUHXqMuhrgxOEeS7G4o=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
-go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
-golang.org/x/crypto v0.55.0 h1:+KWHjbgOaAQ66dh/YlkZKHlz9ZUlq61AFirAR9ntP8M=
-golang.org/x/crypto v0.55.0/go.mod h1:uq0V9dE/fzQuJtbnL+2EhWOE63vo164FY8xqEnV9xis=
-golang.org/x/net v0.57.0 h1:K5+3DljvIuDG9/Jv9rvyMywYNFCQ9RSUY6OOTTkT+tE=
-golang.org/x/net v0.57.0/go.mod h1:KpXc8iv+r3XplLAG/f7Jsf9RPszJzdR0f58q9vGOuEU=
-golang.org/x/sync v0.22.0 h1:SZjpbeLmrCk4xhRSZFNZW5gFUeCeFgjekvI/+gfScek=
-golang.org/x/sync v0.22.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
-golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
-golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
-golang.org/x/text v0.41.0 h1:vz/seA0lnX87Othu2f/0L24RcgrXD9/YFTSuGjj3rH8=
-golang.org/x/text v0.41.0/go.mod h1:jvf1O8ajNzZqhSrQBPbutR/EB83Cc0CFrezNQIwbb5M=
+golang.org/x/crypto v0.57.0 h1:3ZVCjf8Ggz7zneR/EHRVx68Ctf+2pmIMP2UFhh9cC6M=
+golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZA=
+golang.org/x/net v0.58.0 h1:ynWG7rqYi4ccpTEuPZ2QGWHktVEM9DMCj9yzDE0Q7To=
+golang.org/x/net v0.58.0/go.mod h1:YwCddHnFlT7eLQqVprV19OnhLGtc5xOKgE0RyqgfWAU=
+golang.org/x/sync v0.23.0 h1:KameEIfc1IkluZyXWLn39Wd4tURc6GbCiISGiZm2bQk=
+golang.org/x/sync v0.23.0/go.mod h1:sUUOizhqBxiL6pEWpqNLUiaJn1ShEbZ6BBqskPbjZm0=
+golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
+golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
+golang.org/x/text v0.42.0 h1:JbOZXgfeCPU9gacVtYliJqOhD+zhrEqK4LfdpmlUZqI=
+golang.org/x/text v0.42.0/go.mod h1:ojzP1Z+2QtioaF8DTtO8K5q7JWVVYwZKenzujK0Zd0E=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
@@ -0,0 +1,125 @@
+package broker
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Do the emitters and the consumers of a catalogue agree?
+//
+// **The check that was missing** (novox/hq 04-ISSUES/127). Every manifest was individually
+// well-formed and every derivation individually correct, and no cross-module subscription in the
+// mesh matched anything: a consumer's declaration derived into a namespace nobody publishes to.
+// Nothing failed, because a subscription that matches nothing is not an error — it is silence.
+//
+// The comparison has to be over the whole catalogue, because the two halves live in different
+// manifests, and it cannot simply demand that every consumed event have a live emitter: a module
+// may be installed long before the one whose events it wants. So the rule is narrower and still
+// catches this: **where the emitter is present, it must emit what the consumer asked for.**
+
+// AConsumer is one module's interest in another's events, as this check needs it.
+type AConsumer struct {
+	Module   string
+	Consumes []string
+}
+
+// AnEmitter is one module's events.
+type AnEmitter struct {
+	Module string
+	Emits  []string
+}
+
+// Disagreements are the consumed events whose emitter is in the catalogue and does not emit them.
+//
+// Returned as sentences rather than as structs: every one of them is read by a person deciding
+// whether a manifest or a catalogue is wrong, and a pair of names without the reason is a puzzle.
+func Disagreements(emitters []AnEmitter, consumers []AConsumer, seats []DeclaredSeat) []string {
+	emits := map[string]map[string]bool{}
+	for _, e := range emitters {
+		if emits[e.Module] == nil {
+			emits[e.Module] = map[string]bool{}
+		}
+		for _, name := range e.Emits {
+			emits[e.Module][name] = true
+		}
+	}
+	// A seat's events are published by its holder under the seat's name, so a consumer naming the
+	// seat is naming something real even though no module declares it as its own.
+	for _, s := range seats {
+		if len(s.Emits) == 0 {
+			continue
+		}
+		if emits[s.Name] == nil {
+			emits[s.Name] = map[string]bool{}
+		}
+		for _, name := range s.Emits {
+			emits[s.Name][name] = true
+		}
+	}
+
+	var out []string
+	for _, c := range consumers {
+		for _, pattern := range c.Consumes {
+			emitter, event, named := strings.Cut(pattern, ".")
+			// Every event from everyone, or every event from one module: both are deliberate and
+			// neither names a particular event to check.
+			if !named || emitter == "*" || emitter == catalogueTheRest || event == catalogueTheRest {
+				continue
+			}
+			known, present := emits[emitter]
+			if !present {
+				// Not installed here, which is ordinary: a module lives in its own repository and
+				// may be registered later. Nothing to compare, so nothing to say.
+				continue
+			}
+			if matchesAny(event, known) {
+				continue
+			}
+			out = append(out, fmt.Sprintf(
+				"%s consumes %q and %s emits %s — so that subscription would match nothing, and "+
+					"nothing would report it",
+				c.Module, pattern, emitter, listOf(known)))
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// matchesAny says whether one of an emitter's event names satisfies a consumer's pattern.
+func matchesAny(pattern string, emitted map[string]bool) bool {
+	want := strings.Split(pattern, ".")
+	for name := range emitted {
+		if matches(want, strings.Split(name, ".")) {
+			return true
+		}
+	}
+	return false
+}
+
+func matches(pattern, name []string) bool {
+	for i, part := range pattern {
+		if part == catalogueTheRest {
+			return i < len(name)
+		}
+		if i >= len(name) {
+			return false
+		}
+		if part != "*" && part != name[i] {
+			return false
+		}
+	}
+	return len(pattern) == len(name)
+}
+
+func listOf(names map[string]bool) string {
+	if len(names) == 0 {
+		return "nothing"
+	}
+	out := make([]string, 0, len(names))
+	for n := range names {
+		out = append(out, n)
+	}
+	sort.Strings(out)
+	return strings.Join(out, ", ")
+}
@@ -0,0 +1,236 @@
+package broker
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// **Do the catalogue's emitters and consumers agree?**
+//
+// This is the check whose absence let issue 127 stand: every manifest was individually well-formed,
+// every derivation individually correct, and no cross-module subscription in the mesh matched
+// anything. A subscription that matches nothing is not an error — it is silence — so nothing
+// anywhere reported it.
+//
+// It compares what one manifest asks to hear against what another says it emits. It cannot demand
+// that every consumed event have a live emitter, because a module lives in its own repository and
+// may be registered long before the one whose events it wants. Where the emitter *is* here, it must
+// emit what the consumer asked for.
+func TestTheCataloguesEmittersAndConsumersAgree(t *testing.T) {
+	emitters, consumers, seats := theCataloguesEvents(t)
+
+	if bad := Disagreements(emitters, consumers, seats); len(bad) > 0 {
+		t.Fatalf("%d subscription(s) in the catalogue would match nothing:\n  %s",
+			len(bad), strings.Join(bad, "\n  "))
+	}
+}
+
+// And the check itself catches the thing it exists for, so it cannot pass by doing nothing.
+func TestTheAgreementCheckCatchesASubscriptionThatMatchesNothing(t *testing.T) {
+	bad := Disagreements(
+		[]AnEmitter{{Module: "builder", Emits: []string{"built"}}},
+		[]AConsumer{{Module: "mesh-catalog", Consumes: []string{"builder.finished"}}},
+		nil)
+	if len(bad) != 1 {
+		t.Fatalf("a consumer asking for an event its emitter does not emit was not caught: %v", bad)
+	}
+	if !strings.Contains(bad[0], "builder.finished") || !strings.Contains(bad[0], "built") {
+		t.Fatalf("the report names neither what was asked for nor what is emitted: %s", bad[0])
+	}
+
+	// A module that is not here is not a disagreement: it may be registered later.
+	if bad := Disagreements(nil,
+		[]AConsumer{{Module: "plex", Consumes: []string{"sonarr.download.completed"}}}, nil); len(bad) != 0 {
+		t.Fatalf("a consumer whose emitter is not installed was reported: %v", bad)
+	}
+
+	// A wildcard over emitters is deliberate and names no particular event to check.
+	if bad := Disagreements([]AnEmitter{{Module: "sonarr", Emits: []string{"download.completed"}}},
+		[]AConsumer{{Module: "plex", Consumes: []string{"*.download.completed"}}}, nil); len(bad) != 0 {
+		t.Fatalf("a wildcard over emitters was reported: %v", bad)
+	}
+
+	// A consumer of a role's event whose role does not emit it is caught, which is what stops the
+	// catalogue check above from passing by knowing nothing about roles.
+	if bad := Disagreements(nil,
+		[]AConsumer{{Module: "mesh-catalog", Consumes: []string{"mesh-build-machine.finished"}}},
+		[]DeclaredSeat{{Name: "mesh-build-machine", Emits: []string{"built"}}}); len(bad) != 1 {
+		t.Fatalf("a consumer of a role event the role does not emit was not caught: %v", bad)
+	}
+
+	// An event published under a seat's name is real even though no module declares it as its own.
+	if bad := Disagreements(nil,
+		[]AConsumer{{Module: "watcher", Consumes: []string{"mesh-artifact-store.image.pushed"}}},
+		[]DeclaredSeat{{Name: "the-artifact-store", Emits: []string{"image.pushed"}}}); len(bad) != 0 {
+		t.Fatalf("an event a seat emits was reported as matching nothing: %v", bad)
+	}
+}
+
+func theCataloguesEvents(t *testing.T) ([]AnEmitter, []AConsumer, []DeclaredSeat) {
+	t.Helper()
+	root := filepath.Join("..", "..", "..", "mesh-catalog", "modules")
+	entries, err := os.ReadDir(root)
+	if err != nil {
+		t.Skipf("catalogue sibling not present: %v", err)
+	}
+	var emitters []AnEmitter
+	var consumers []AConsumer
+	// The mesh's own roles, which emit under the seat's name rather than any module's (novox/hq
+	// ADR 0121). Without these the check skips every consumer of a role's event as "the emitter is
+	// not installed" — which is how it passed vacuously the first time one existed.
+	var seats []DeclaredSeat
+	for _, own := range catalogue.SeatsWithAProtocol() {
+		seats = append(seats, DeclaredSeat{Name: own.Name, Accepts: own.Accepts, Emits: own.Emits})
+	}
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		raw, err := os.ReadFile(filepath.Join(root, e.Name(), "module.json"))
+		if err != nil {
+			continue
+		}
+		var m struct {
+			Module   string   `json:"module"`
+			Emits    []string `json:"emits"`
+			Consumes []string `json:"consumes"`
+			Seats    []struct {
+				Name  string   `json:"name"`
+				Emits []string `json:"emits"`
+			} `json:"seats"`
+		}
+		if err := json.Unmarshal(raw, &m); err != nil {
+			t.Fatalf("%s: %v", e.Name(), err)
+		}
+		if len(m.Emits) > 0 {
+			emitters = append(emitters, AnEmitter{Module: m.Module, Emits: m.Emits})
+		}
+		if len(m.Consumes) > 0 {
+			consumers = append(consumers, AConsumer{Module: m.Module, Consumes: m.Consumes})
+		}
+		for _, s := range m.Seats {
+			seats = append(seats, DeclaredSeat{Name: s.Name, Emits: s.Emits})
+		}
+	}
+	if len(emitters) == 0 {
+		t.Skip("no manifests found beside this checkout")
+	}
+	return emitters, consumers, seats
+}
+
+// **Do the derived subjects meet, not just the names?**
+//
+// The check above compares what a consumer asks for against what an emitter says it emits, by name. It
+// passed while the catalogue's subscription pointed at `mesh.mod.mesh-build-machine.event.built` — a
+// module namespace for a role's event, which no emitter owns. The names agreed; the subjects did not,
+// and the graph stayed empty.
+//
+// So this compares the thing that actually has to match: the subject a consumer subscribes against the
+// subject an emitter publishes. It is the last place the two halves can be held together, because
+// after this the server is the only thing that knows and it says nothing — a subscription that matches
+// nothing is silence.
+func TestTheCataloguesDerivedSubjectsMeet(t *testing.T) {
+	emitters, consumers, seats := theCataloguesEvents(t)
+
+	// Every subject something publishes: a module's own events, and the events of every role.
+	published := map[string]bool{}
+	for _, e := range emitters {
+		for _, name := range e.Emits {
+			published["mesh.mod."+e.Module+".event."+name] = true
+		}
+	}
+	for _, s := range seats {
+		for _, name := range s.Emits {
+			published["mesh.seat."+s.Name+".event."+name] = true
+		}
+	}
+
+	byName := map[string]DeclaredSeat{}
+	for _, s := range seats {
+		byName[s.Name] = s
+	}
+
+	var lonely []string
+	for _, c := range consumers {
+		principal := Principal{Kind: KindModule, Node: "one", Module: c.Module, PasswordHash: "x"}
+		for _, want := range c.Consumes {
+			emitter, event, named := strings.Cut(want, ".")
+			if named {
+				if s, isASeat := byName[emitter]; isASeat {
+					principal.Watches = append(principal.Watches,
+						Seat{Name: s.Name, Emits: []string{event}})
+					continue
+				}
+			}
+			principal.Consumes = append(principal.Consumes, want)
+		}
+		perms, err := PermissionsFor(principal)
+		if err != nil {
+			t.Fatalf("%s: %v", c.Module, err)
+		}
+		for _, subject := range perms.Subscribe {
+			if !strings.Contains(subject, ".event.") {
+				continue
+			}
+			if reaches(subject, published) {
+				continue
+			}
+			// A wildcard over emitters reaches whatever arrives later, and an emitter that is not
+			// installed is ordinary — both are already excused by the check above, so only a subject
+			// that can never match anything gets here.
+			if strings.Contains(subject, "*") || strings.Contains(subject, ">") {
+				continue
+			}
+			lonely = append(lonely, c.Module+" subscribes "+subject+", which nothing publishes")
+		}
+	}
+	if len(lonely) > 0 {
+		sort.Strings(lonely)
+		t.Fatalf("%d subscription(s) derive to a subject no emitter owns:\n  %s",
+			len(lonely), strings.Join(lonely, "\n  "))
+	}
+}
+
+// And it catches the thing it exists for: a role's event read as a module's.
+func TestTheDerivedSubjectCheckCatchesARolesEventReadAsAModules(t *testing.T) {
+	published := map[string]bool{"mesh.seat.mesh-build-machine.event.built": true}
+	// What the derivation produced before a consumed seat name was resolved as one.
+	if reaches("mesh.mod.mesh-build-machine.event.built", published) {
+		t.Fatal("a module namespace was treated as reaching a role's event, which is the bug")
+	}
+	// And the corrected one does reach it.
+	if !reaches("mesh.seat.mesh-build-machine.event.built", published) {
+		t.Fatal("the role's own subject does not reach the role's event")
+	}
+}
+
+// reaches says whether a subscribed subject admits any published one.
+func reaches(subject string, published map[string]bool) bool {
+	for p := range published {
+		if admitsSubject(strings.Split(subject, "."), strings.Split(p, ".")) {
+			return true
+		}
+	}
+	return false
+}
+
+func admitsSubject(pattern, subject []string) bool {
+	for i, token := range pattern {
+		if token == ">" {
+			return i < len(subject)
+		}
+		if i >= len(subject) {
+			return false
+		}
+		if token != "*" && token != subject[i] {
+			return false
+		}
+	}
+	return len(pattern) == len(subject)
+}
@@ -1,67 +0,0 @@
-package broker_test
-
-import (
-	"regexp"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/broker"
-	"github.com/novox/mesh-controller/internal/link"
-)
-
-// The names are written twice, so a test keeps them agreeing.
-//
-// `link` imports `broker`, so `broker` cannot import `link` — the queue and exchange names
-// therefore exist in both. A scoped account naming a queue nothing publishes to produces a
-// builder that takes no work and says nothing about why, which is the worst kind of silence.
-//
-// An external test package, because it may import both without either importing the other.
-func TestTheNamesTheBrokerScopesAreTheNamesTheLinkUses(t *testing.T) {
-	for _, agreed := range []struct {
-		what     string
-		scoped   string
-		actually string
-	}{
-		{"the build queue", broker.BuildQueueName, link.BuildQueue},
-		{"the exchange", broker.ExchangeName, link.Exchange},
-		{"a node's queue", broker.QueueFor("somewhere"), link.QueueFor("somewhere")},
-	} {
-		if agreed.scoped != agreed.actually {
-			t.Errorf("%s: the broker scopes %q and the link uses %q",
-				agreed.what, agreed.scoped, agreed.actually)
-		}
-	}
-}
-
-func TestABuilderMayWriteToAReplyQueueAndReadNoNodesDeclarations(t *testing.T) {
-	// The scoping, checked as patterns rather than by connecting: what it may write must include
-	// the queue an asker actually waits on, and what it may read must not include any node's.
-	//
-	// This exists because the first version scoped writes to `amq.gen-*` — the name one broker
-	// happens to generate — and the builder built, could not answer, and the connection simply
-	// closed saying only "not allowed to publish to exchange \'\'". Answering through the
-	// exchange is what removed the need for any of that.
-	write := regexp.MustCompile("^" + regexp.QuoteMeta(broker.ExchangeName) + "$")
-	if !write.MatchString(broker.ExchangeName) {
-		t.Error("a builder may not write to the exchange, so it can take work and never answer")
-	}
-	// And not the default exchange, where permission is per exchange rather than per queue — a
-	// builder allowed to use it could publish into any node's queue.
-	//
-	// Confirmed against a real broker as well, and worth recording how that nearly went wrong:
-	// an unconfirmed publish is asynchronous, so a refusal arrives as a channel close afterwards
-	// and a naive check reports success. With publisher confirms the broker's refusal is
-	// immediate. **A negative security assertion made against an asynchronous call is not an
-	// assertion.**
-	if write.MatchString("") {
-		t.Error("a builder may publish to the default exchange, and so into any node's queue")
-	}
-
-	read := regexp.MustCompile("^" + regexp.QuoteMeta(broker.BuildQueueName) + "$")
-	if !read.MatchString(broker.BuildQueueName) {
-		t.Error("a builder may not read the build queue")
-	}
-	if read.MatchString(link.QueueFor("someone-else")) {
-		// A build machine is not a node, and a node's queue carries its declarations.
-		t.Error("a builder may read another machine's declarations")
-	}
-}
@@ -194,16 +194,3 @@ func TestTheAddressPortFollowsThePortTwin(t *testing.T) {
 		t.Fatalf("the address is %q; the node put the bus on 5679", b.Address)
 	}
 }
-
-func TestTheManagementPortFollowsThePortTwin(t *testing.T) {
-	t.Setenv(ManagementVar, "http://guest:guest@127.0.0.1:15672")
-	t.Setenv(ManagementVar+"_FILE", "")
-	t.Setenv(ManagementVar+"_PORT", "15673")
-	m, err := ManagementFromEnvironment()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if m.base.Host != "127.0.0.1:15673" {
-		t.Fatalf("the management API is at %q; the node put it on 15673", m.base.Host)
-	}
-}
@@ -0,0 +1,237 @@
+package broker
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Streams and consumers derived from what modules declare.
+//
+// The mesh's own four exist before any module does (streams.go). Everything here is the other
+// half: a seat's stream comes into being when the module declaring it is **registered**, and a
+// consumer when a module is **assigned** — which is why ADR 0116's task 1.4 had to be narrowed to
+// the foundation set. Neither has happened at genesis.
+//
+// All of it is a pure function of declarations. The controller is still the only writer; this is
+// only what it writes.
+
+// A Consumer is a durable subscription the controller creates on a module's behalf. A module
+// declares what it reacts to, never how delivery works, so it does not name these and cannot
+// misconfigure them.
+type Consumer struct {
+	Name   string
+	Stream string
+	// Filters are the subjects this consumer receives. One consumer per module with several
+	// filters, rather than one per consumed event: its ack subject is derived from its name, and
+	// a module with five consumers would need five ack permissions to ack its own deliveries.
+	Filters []string
+	// Queue is the queue group, set for a seat's worker so that "exactly one holder" survives a
+	// seat later being relaxed to several. Authority and delivery are kept separate on purpose.
+	Queue string
+	// Push asks the server to deliver to a subject rather than wait to be pulled.
+	//
+	// For the mesh's own consumer, where the controller wants every message to arrive in the one
+	// loop it already runs: pulling would mean a second goroutine fetching batches and handing
+	// them over, and a loop that acts on one message at a time is the property the store window
+	// depends on. A queue group implies this, because a group has nothing to pull from.
+	Push bool
+	// AckWaitSeconds before an unacknowledged delivery is redelivered.
+	AckWaitSeconds int
+	// MaxDeliver before the message is dead-lettered; zero for the mesh's default.
+	MaxDeliver int
+	Why        string
+}
+
+// seatStreamName is the stream holding a seat's inbound work. Named after the seat rather than
+// the module holding it, because the holder can change and the queued work must not care — which
+// is the whole reason a caller addresses a seat instead of a module.
+func seatStreamName(seat string) string { return "SEAT_" + upperSnake(seat) }
+
+// SeatStreams is one work queue per declared seat, created when the declaring module is
+// registered rather than when it is assigned.
+//
+// **The stream exists before anyone holds the seat, and that is the point.** Work queues until a
+// holder appears, so installing the telegram module a week after something started sending to it
+// flushes the backlog instead of having lost it. A stream created at assignment would make "the
+// holder is not here yet" mean "your messages are gone".
+func SeatStreams(seats []DeclaredSeat) []Stream {
+	sorted := append([]DeclaredSeat(nil), seats...)
+	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Name < sorted[j].Name })
+
+	var out []Stream
+	for _, s := range sorted {
+		if len(s.Accepts) == 0 {
+			// A seat that only emits and serves needs no stream: its events ride EVENTS and its
+			// tools are core request/reply, which is never persisted.
+			continue
+		}
+		retain := s.RetainSeconds
+		if retain == 0 {
+			retain = 7 * 24 * 60 * 60
+		}
+		out = append(out, Stream{
+			Name:      seatStreamName(s.Name),
+			Subjects:  []string{"mesh.seat." + s.Name + ".accept.>"},
+			Retention: RetentionWorkQueue,
+			MaxAge:    retain,
+			Why: fmt.Sprintf("work submitted to the %s seat; one holder consumes it, and it "+
+				"queues while nobody does", s.Name),
+		})
+	}
+	return out
+}
+
+// A DeclaredSeat is a seat as the catalogue knows it. Mirrored here rather than imported so this
+// package stays free of the catalogue's own types — the same reason the host mirrors the
+// contracts instead of importing the sdk.
+type DeclaredSeat struct {
+	Name    string
+	Accepts []string
+	// Emits are the verbs the seat's holder publishes under the seat's own name. An event about a
+	// role belongs here rather than in the holder's namespace, because the name then outlives
+	// whoever fills it (novox/hq ADR 0121, 04-ISSUES/127).
+	Emits []string
+	// Serves are the verbs the holder answers, request and reply.
+	Serves        []string
+	RetainSeconds int
+}
+
+// ConsumerFor is the durable consumer a module's declarations imply, or false when it subscribes
+// to nothing and needs none.
+//
+// One per module, with every consumed subject as a filter, because its ack permission is derived
+// from its name: a module with a consumer per event would need an ack permission per consumer,
+// and the permission list would stop being derivable from the declaration.
+func ConsumerFor(p Principal) (Consumer, bool) {
+	// A module that reacts to anything — a module's events or a role's (novox/hq ADR 0121). Watching
+	// a role was missing here, so the one module that does it got no consumer at all: it started,
+	// connected, and its graph stayed empty with nothing anywhere reporting why.
+	if p.Kind != KindModule || (len(p.Consumes) == 0 && len(p.Watches) == 0) {
+		return Consumer{}, false
+	}
+	perms, err := PermissionsFor(p)
+	if err != nil {
+		return Consumer{}, false
+	}
+	// Events, wherever they live: a module's own namespace, and the namespace of any role it watches
+	// (novox/hq ADR 0121). Tool subjects and inboxes are subscribed directly and are not a consumer's
+	// business, which is why this is a filter and not the whole list.
+	var filters []string
+	for _, s := range perms.Subscribe {
+		if strings.Contains(s, ".event.") {
+			filters = append(filters, s)
+		}
+	}
+	if len(filters) == 0 {
+		return Consumer{}, false
+	}
+	sort.Strings(filters)
+	return Consumer{
+		Name:           consumerDurable(p),
+		Stream:         consumerStream(p),
+		Filters:        filters,
+		AckWaitSeconds: 30,
+		MaxDeliver:     5,
+		Why:            "what " + p.Module + " declared it consumes; after max-deliver it dead-letters",
+	}, true
+}
+
+// HolderConsumerFor is the worker a seat's holder gets on that seat's work queue.
+//
+// **A queue group even though the seat guarantees one holder.** The seat is *authority* — who may
+// be the telegram sender — and the queue group is *delivery*. Tie delivery to the seat and the
+// day somebody allows two holders for throughput, every message is processed twice with nothing
+// reporting it. Kept separate, relaxing one changes nothing about the other.
+func HolderConsumerFor(node, module string, seat DeclaredSeat) (Consumer, bool) {
+	if len(seat.Accepts) == 0 {
+		return Consumer{}, false
+	}
+	return Consumer{
+		Name:           "SEAT_" + upperSnake(seat.Name) + "_worker",
+		Stream:         seatStreamName(seat.Name),
+		Filters:        []string{"mesh.seat." + seat.Name + ".accept.>"},
+		Queue:          "holders",
+		AckWaitSeconds: 60,
+		MaxDeliver:     5,
+		Why: fmt.Sprintf("%s on %s holds %s; it acknowledges after the work is done, so a "+
+			"crash mid-work redelivers rather than loses", module, node, seat.Name),
+	}, true
+}
+
+// NodeConsumer is the durable consumer a node reads its own declaration through.
+//
+// **Derived from a node existing, and created by the controller, because a host cannot create it.**
+// A host's account may subscribe its own declaration subject and publish its own ack subject, and
+// reaches no part of the JetStream API — which is correct (the controller is the only writer of
+// consumer definitions, design 25 §3) and means the consumer must be waiting before the host binds
+// to it. Named after the node, because the node's ack grant is `$JS.ACK.NODES.<node>.>` and a
+// consumer named anything else is one the host cannot acknowledge a delivery from.
+//
+// **No max-deliver, and a long ack wait.** A declaration is settled only after the node has applied
+// it and reported, which is minutes on a machine pulling images; and a declaration the mesh cannot
+// get a node to accept is not one to dead-letter, because the stream keeps only the newest per node
+// anyway — so there is exactly one message per node to redeliver, for as long as that node is away.
+func NodeConsumer(node string) Consumer {
+	return Consumer{
+		Name:           node,
+		Stream:         "NODES",
+		Filters:        []string{"mesh.node." + node + ".declare"},
+		Push:           true,
+		AckWaitSeconds: 300,
+		Why: "how " + node + " hears what it should be; last-per-subject, so a node that was away " +
+			"gets exactly the current declaration and nothing older",
+	}
+}
+
+// AssertNodeConsumers brings every known node's declaration consumer into being.
+//
+// Asserted on start as well as created at enrolment, for the reason the streams are: a mesh raised
+// from a restored backup, or one whose bus was recreated, has node records and no consumers, and a
+// node whose consumer is missing hears nothing while everything else about it looks correct.
+func AssertNodeConsumers(e Ensurer, nodes []string) error {
+	for _, n := range nodes {
+		if err := e.EnsureConsumer(NodeConsumer(n)); err != nil {
+			return fmt.Errorf("asserting how %s hears its declaration: %w", n, err)
+		}
+	}
+	return nil
+}
+
+// AllOverlaps reports subject filters claimed by more than one stream, across the mesh's own and
+// every derived one.
+//
+// NATS refuses an overlapping stream rather than merging it (verified against nats-server 2.10:
+// "subjects overlap with an existing stream"), so this is not a subtle divergence — it is a
+// registration that fails. Catching it here names both streams, before a half-applied mesh does.
+func AllOverlaps(seats []DeclaredSeat) []string {
+	all := append(MeshStreams(), SeatStreams(seats)...)
+	seen := map[string]string{}
+	var clashes []string
+	for _, s := range all {
+		for _, subject := range s.Subjects {
+			if first, ok := seen[subject]; ok {
+				clashes = append(clashes, fmt.Sprintf("%s and %s both claim %s", first, s.Name, subject))
+				continue
+			}
+			seen[subject] = s.Name
+		}
+	}
+	sort.Strings(clashes)
+	return clashes
+}
+
+// upperSnake makes a stream name from a seat name. NATS stream names may not contain a dot,
+// a space or a wildcard, and a hyphen is legal but reads badly beside the mesh's own.
+func upperSnake(s string) string {
+	out := []rune(s)
+	for i, r := range out {
+		switch {
+		case r >= 'a' && r <= 'z':
+			out[i] = r - 32
+		case r == '-' || r == '.':
+			out[i] = '_'
+		}
+	}
+	return string(out)
+}
@@ -0,0 +1,155 @@
+package broker
+
+import (
+	"strings"
+	"testing"
+)
+
+func telegramSeat() DeclaredSeat {
+	return DeclaredSeat{Name: "telegram-sender", Accepts: []string{"send"}}
+}
+
+// The stream exists from registration, not assignment: work queues until a holder appears, so
+// installing the module a week later flushes the backlog rather than having lost it.
+func TestASeatGetsAWorkQueueOfItsOwn(t *testing.T) {
+	got := SeatStreams([]DeclaredSeat{telegramSeat()})
+	if len(got) != 1 {
+		t.Fatalf("expected one stream, got %d", len(got))
+	}
+	s := got[0]
+	if s.Retention != RetentionWorkQueue {
+		t.Fatalf("a seat's inbound queue retains as %q; one holder must take each message once", s.Retention)
+	}
+	if s.Subjects[0] != "mesh.seat.telegram-sender.accept.>" {
+		t.Fatalf("filters on %v", s.Subjects)
+	}
+}
+
+// A seat that only emits and serves needs no stream: its events ride EVENTS and its tools are
+// core request/reply, which is never persisted.
+func TestASeatThatAcceptsNothingGetsNoStream(t *testing.T) {
+	if got := SeatStreams([]DeclaredSeat{{Name: "announcer"}}); len(got) != 0 {
+		t.Fatalf("a seat with no inbound work got %d stream(s)", len(got))
+	}
+}
+
+// Retention belongs to whoever owns the namespace, and a seat owns its own.
+func TestASeatsRetentionIsItsOwn(t *testing.T) {
+	s := SeatStreams([]DeclaredSeat{{Name: "slow", Accepts: []string{"work"}, RetainSeconds: 30 * 24 * 60 * 60}})
+	if s[0].MaxAge != 30*24*60*60 {
+		t.Fatalf("the seat's declared retention was not used: %d", s[0].MaxAge)
+	}
+	d := SeatStreams([]DeclaredSeat{telegramSeat()})
+	if d[0].MaxAge == 0 {
+		t.Fatal("a seat that declares no retention got an unbounded queue")
+	}
+}
+
+// NATS refuses an overlapping stream outright, so a clash here is a registration that fails.
+func TestNoDerivedStreamOverlapsTheMeshsOwn(t *testing.T) {
+	seats := []DeclaredSeat{telegramSeat(), {Name: "licensing-master", Accepts: []string{"report"}}}
+	if c := AllOverlaps(seats); len(c) != 0 {
+		t.Fatalf("overlapping filters: %v", c)
+	}
+}
+
+// One consumer per module, with every consumed subject as a filter — because its ack permission
+// is derived from its name, and a consumer per event would need an ack permission per consumer.
+func TestAModuleGetsOneConsumerCarryingEveryFilter(t *testing.T) {
+	c, ok := ConsumerFor(Principal{Kind: KindModule, Node: "one", Module: "audit",
+		Consumes: []string{"shop.order.placed", "billing.invoice.sent"}, PasswordHash: "x"})
+	if !ok {
+		t.Fatal("a module that consumes got no consumer")
+	}
+	if len(c.Filters) != 2 {
+		t.Fatalf("expected both subjects as filters, got %v", c.Filters)
+	}
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "audit",
+		Consumes: []string{"shop.order.placed"}, PasswordHash: "x"})
+	ack := "$JS.ACK." + c.Stream + "." + c.Name + ".>"
+	found := false
+	for _, p := range perms.Publish {
+		if p == ack {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("the consumer is named %q but the ack permission is %v; a module could not ack "+
+			"its own deliveries", c.Name, perms.Publish)
+	}
+}
+
+// A module that subscribes to nothing needs no consumer, and creating one would leave an object
+// nothing reads and everything has to maintain.
+func TestAModuleThatConsumesNothingGetsNoConsumer(t *testing.T) {
+	if _, ok := ConsumerFor(Principal{Kind: KindModule, Node: "one", Module: "shop",
+		Emits: []string{"order.placed"}, PasswordHash: "x"}); ok {
+		t.Fatal("a pure emitter got a consumer")
+	}
+}
+
+// The seat is authority and the queue group is delivery. Tie them together and the day somebody
+// allows two holders, every message is processed twice with nothing reporting it.
+func TestAHoldersWorkerUsesAQueueGroupAnyway(t *testing.T) {
+	c, ok := HolderConsumerFor("one", "telegram", telegramSeat())
+	if !ok {
+		t.Fatal("the holder of a seat with inbound work got no worker")
+	}
+	if c.Queue == "" {
+		t.Fatal("the worker is not in a queue group, so a second holder would double-process")
+	}
+	if c.Stream != "SEAT_TELEGRAM_SENDER" {
+		t.Fatalf("the worker reads %q, not the seat's own stream", c.Stream)
+	}
+	if c.MaxDeliver == 0 {
+		t.Fatal("a failing worker would redeliver forever rather than dead-letter")
+	}
+}
+
+// The stream is named after the seat, not its holder: the holder can change and the queued work
+// must not care.
+func TestASeatsStreamIsNamedAfterTheSeat(t *testing.T) {
+	name := seatStreamName("telegram-sender")
+	if strings.Contains(name, "telegram-sender") {
+		t.Fatalf("%q keeps characters a stream name may not hold", name)
+	}
+	if name != "SEAT_TELEGRAM_SENDER" {
+		t.Fatalf("unexpected stream name %q", name)
+	}
+}
+
+// A node hears its declaration through a consumer only the controller can make.
+//
+// The three things that would each break it silently: a name other than the node's is one the host
+// cannot acknowledge a delivery from, because its ack grant is derived from the node's name; a
+// filter other than its own declaration subject is a node reading another's; and a pull consumer is
+// one the host cannot bind a channel to without creating something, which it has no authority for.
+func TestANodesDeclarationConsumerIsWhatItsOwnGrantAllows(t *testing.T) {
+	c := NodeConsumer("anchor")
+	if c.Name != "anchor" {
+		t.Fatalf("named %q, so the node cannot ack from it: its grant is $JS.ACK.NODES.anchor.>", c.Name)
+	}
+	if c.Stream != "NODES" {
+		t.Fatalf("on stream %q rather than the one declarations live in", c.Stream)
+	}
+	if len(c.Filters) != 1 || c.Filters[0] != "mesh.node.anchor.declare" {
+		t.Fatalf("filters %v, which is not this node's own declaration and nothing else", c.Filters)
+	}
+	if !c.Push {
+		t.Fatal("pulled, which a host cannot do: pulling needs the JetStream API and a host reaches none of it")
+	}
+	if c.MaxDeliver != 0 {
+		t.Fatalf("max-deliver %d: a declaration a node has not taken yet is not one to dead-letter, "+
+			"because the stream holds exactly one per node", c.MaxDeliver)
+	}
+
+	// And the grant the node actually gets has to match, or none of the above matters.
+	perms, err := PermissionsFor(Principal{Kind: KindNode, Node: "anchor"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Without the ack grant every declaration a node receives is redelivered for ever; without the
+	// subscribe grant its consumer delivers to nobody.
+	has(t, perms.Publish, "$JS.ACK.NODES."+c.Name+".>")
+	has(t, perms.Subscribe, c.Filters[0])
+}
@@ -0,0 +1,126 @@
+package broker
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+	"testing"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+// **The first user list the installer carries must be the one the controller would compose.**
+//
+// At genesis there is no mesh to write the bus's user list, so the installer carries one: the
+// controller's own account, at a bootstrap password, the way the store is reached at
+// `postgres:bootstrap` (novox/hq design 25 §4, task 1.7). It is written by hand in a template and
+// derived in code here, which is two statements of one fact — so this compares them.
+//
+// Getting it wrong is the worst kind of silent: a controller whose carried permissions are narrower
+// than the ones it derives comes up, connects, and is refused on the first thing it tries, with an
+// authorisation error that names a subject and not the template that forgot it. And a mesh cannot be
+// raised twice to find out.
+func TestTheInstallersFirstUserListIsWhatTheControllerWouldCompose(t *testing.T) {
+	accounts := theCarriedAccounts(t)
+
+	want, err := PermissionsFor(Principal{Kind: KindController, PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	carriedPub := subjectsIn(accounts, "publish")
+	carriedSub := subjectsIn(accounts, "subscribe")
+
+	if diff := missing(want.Publish, carriedPub); len(diff) > 0 {
+		t.Errorf("the installer's user list does not let the controller publish %v — it would come up "+
+			"and be refused on the first thing it tried", diff)
+	}
+	if diff := missing(want.Subscribe, carriedSub); len(diff) > 0 {
+		t.Errorf("the installer's user list does not let the controller subscribe %v", diff)
+	}
+	// And nothing wider than what it derives, or genesis quietly grants a privilege the composition
+	// takes away again on the first push.
+	if diff := missing(carriedPub, want.Publish); len(diff) > 0 {
+		t.Errorf("the installer's user list lets the controller publish %v, which it does not derive", diff)
+	}
+	if diff := missing(carriedSub, want.Subscribe); len(diff) > 0 {
+		t.Errorf("the installer's user list lets the controller subscribe %v, which it does not derive", diff)
+	}
+
+	// The credential is the bootstrap one and the hash really is of it, because a hash of something
+	// else is a controller that cannot log in to the bus it was just given.
+	hash := regexp.MustCompile(`\$2[aby]?\$[0-9]+\$[A-Za-z0-9./]{53}`).FindString(accounts)
+	if hash == "" {
+		t.Fatal("the installer's user list carries no password hash")
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte("bootstrap")); err != nil {
+		t.Fatalf("the carried hash does not verify the bootstrap credential the template also carries: %v", err)
+	}
+}
+
+// theCarriedAccounts is the accounts file the installer's template writes at genesis.
+func theCarriedAccounts(t *testing.T) string {
+	t.Helper()
+	path := filepath.Join("..", "..", "..", "mesh-host", "examples", "foundation-first-node-nats.lock")
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Skipf("the host's checkout is not beside this one: %v", err)
+	}
+	// The template is JSON with line comments, which is how every one of them is written.
+	var lines []string
+	for _, l := range strings.Split(string(raw), "\n") {
+		if !strings.HasPrefix(strings.TrimSpace(l), "//") {
+			lines = append(lines, l)
+		}
+	}
+	var bundle struct {
+		Resources []map[string]any `json:"resources"`
+	}
+	if err := json.Unmarshal([]byte(strings.Join(lines, "\n")), &bundle); err != nil {
+		t.Fatalf("the template is not readable: %v", err)
+	}
+	for _, r := range bundle.Resources {
+		if r["id"] == "bus-accounts" {
+			content, _ := r["content"].(string)
+			if content == "" {
+				t.Fatal("the template's accounts file is empty, so the bus would refuse every connection")
+			}
+			return content
+		}
+	}
+	t.Fatal("the template carries no accounts file, so a mesh raised from it has a bus nobody may use")
+	return ""
+}
+
+// subjectsIn reads one allow-list out of a composed accounts file.
+func subjectsIn(accounts, which string) []string {
+	found := regexp.MustCompile(which + `: \{ allow: \[([^\]]*)\]`).FindStringSubmatch(accounts)
+	if len(found) != 2 {
+		return nil
+	}
+	var out []string
+	for _, part := range strings.Split(found[1], ",") {
+		if s := strings.Trim(strings.TrimSpace(part), `"`); s != "" {
+			out = append(out, s)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// missing is what is in want and not in got.
+func missing(want, got []string) []string {
+	have := map[string]bool{}
+	for _, g := range got {
+		have[g] = true
+	}
+	var out []string
+	for _, w := range want {
+		if !have[w] {
+			out = append(out, w)
+		}
+	}
+	return out
+}
@@ -0,0 +1,213 @@
+package broker
+
+import (
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go"
+)
+
+// The JetStream side of the controller: the one place the mesh's streams and consumers are
+// actually created.
+//
+// Everything that decides *what* they are is pure and lives beside this (streams.go, derived.go).
+// This is only the part that talks to a server, kept small on purpose: a bug in a subject filter
+// should be findable in a unit test, and only a bug in "did the server accept it" should need one
+// running.
+
+// A JetStream is a connection to the bus, as the controller uses it.
+type JetStream struct {
+	conn *nats.Conn
+	js   nats.JetStreamContext
+}
+
+// Dial connects and returns the controller's JetStream handle.
+func Dial(url string, opts ...nats.Option) (*JetStream, error) {
+	opts = append(opts, nats.Name("mesh-controller"), nats.Timeout(10*time.Second))
+	// **Pinned, not named.** The bus presents the mesh's own certificate, which names nothing a
+	// public verifier would accept (design 25 §4: a host pins the server's exact certificate and
+	// checks nothing else, and so does this). Without this, the first connection failed with
+	// "certificate is not valid for any names" against a bus that was answering (2026-09-28).
+	if path := strings.TrimSpace(os.Getenv(CertificateVar)); path != "" {
+		pinned, err := pinnedTo(path)
+		if err != nil {
+			return nil, err
+		}
+		opts = append(opts, nats.Secure(pinned))
+	}
+	// **Its own inbox, and nothing wider.** Every principal is granted `_INBOX.<its user>.>` and
+	// no other inbox; the client's default prefix is random, and the server refused the first
+	// subscription to it (2026-09-28). The user is in the URL, so the prefix follows from it.
+	if user, _, _ := CredentialIn(url); user != "" {
+		opts = append(opts, nats.CustomInboxPrefix("_INBOX."+user))
+	}
+	// The address in an error is the address alone. The URL carries this controller's password,
+	// and an error here is written on the assumption it will be logged.
+	where := BareAddress(url)
+	conn, err := nats.Connect(url, opts...)
+	if err != nil {
+		return nil, fmt.Errorf("connecting to the bus at %s: %w", where, err)
+	}
+	js, err := conn.JetStream()
+	if err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("the bus at %s has no JetStream: %w", where, err)
+	}
+	return &JetStream{conn: conn, js: js}, nil
+}
+
+// pinnedTo is a TLS configuration that accepts exactly the certificate in the file and no other:
+// the leaf's SHA-256, compared on every handshake, with the name and the chain deliberately not
+// consulted — a self-signed certificate with no names is the ordinary case for a mesh's bus.
+func pinnedTo(path string) (*tls.Config, error) {
+	want, err := FingerprintOf(path)
+	if err != nil {
+		return nil, err
+	}
+	return PinnedToFingerprint(want), nil
+}
+
+// DialPinned is Dial with the server's certificate pinned by a fingerprint the caller already holds
+// — a module or a build machine that was handed one beside its credential, and has no file.
+func DialPinned(url, fingerprint string, opts ...nats.Option) (*JetStream, error) {
+	if strings.TrimSpace(fingerprint) != "" {
+		opts = append(opts, nats.Secure(PinnedToFingerprint(fingerprint)))
+	}
+	return Dial(url, opts...)
+}
+
+// PinnedToFingerprint accepts exactly the certificate with this SHA-256 and no other.
+func PinnedToFingerprint(want string) *tls.Config {
+	return &tls.Config{
+		InsecureSkipVerify: true, //nolint:gosec // replaced by the pin below, which is stricter
+		MinVersion:         tls.VersionTLS12,
+		VerifyPeerCertificate: func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
+			if len(rawCerts) == 0 {
+				return errors.New("the bus presented no certificate")
+			}
+			sum := sha256.Sum256(rawCerts[0])
+			got := "sha256:" + hex.EncodeToString(sum[:])
+			if got != want {
+				return fmt.Errorf("the bus presented a certificate this mesh does not know (%s…), expected %s…", got[:23], want[:23])
+			}
+			return nil
+		},
+	}
+}
+
+// Conn is the connection itself, for what the mesh keeps off JetStream on purpose — a heartbeat,
+// a tool call — where a lost message is answered by the next one or by a timeout the caller
+// already handles (design 25 §3).
+func (j *JetStream) Conn() *nats.Conn { return j.conn }
+
+// Context is the JetStream handle, for subscribing to what the consumers above define.
+func (j *JetStream) Context() nats.JetStreamContext { return j.js }
+
+func (j *JetStream) Close() {
+	if j.conn != nil {
+		j.conn.Close()
+	}
+}
+
+// EnsureStream creates the stream if it is absent and brings it to match if it is present.
+//
+// **Idempotent, because the controller asserts on every start** rather than creating once at
+// genesis: a stream somebody deleted, or a mesh raised from a restored backup, has to converge
+// rather than run without the guarantee its messages assume.
+//
+// An update, not a delete and recreate. Recreating would discard every message the stream holds
+// and every consumer's position in it — which for CONTROL means the pushes being held through a
+// store restart, exactly the guarantee the stream exists for.
+func (j *JetStream) EnsureStream(s Stream) error {
+	want := &nats.StreamConfig{
+		Name:              s.Name,
+		Subjects:          s.Subjects,
+		Retention:         retentionOf(s.Retention),
+		MaxAge:            time.Duration(s.MaxAge) * time.Second,
+		MaxMsgsPerSubject: int64(s.MaxMsgsPerSubject),
+		Description:       s.Why,
+	}
+	if s.Retention == RetentionLastPerSubject {
+		// Last-per-subject is a limits stream with one message kept per subject, not a
+		// retention policy of its own — the state shape, spelled the way the server spells it.
+		want.Retention = nats.LimitsPolicy
+		want.MaxMsgsPerSubject = 1
+		want.MaxAge = 0
+	}
+
+	switch _, err := j.js.StreamInfo(s.Name); {
+	case err == nil:
+		if _, err := j.js.UpdateStream(want); err != nil {
+			return fmt.Errorf("bringing stream %s to match: %w", s.Name, err)
+		}
+		return nil
+	case errors.Is(err, nats.ErrStreamNotFound):
+		if _, err := j.js.AddStream(want); err != nil {
+			return fmt.Errorf("creating stream %s: %w", s.Name, err)
+		}
+		return nil
+	default:
+		return fmt.Errorf("asking about stream %s: %w", s.Name, err)
+	}
+}
+
+// EnsureConsumer creates or updates one durable consumer.
+//
+// Explicit acknowledgement throughout: a consumer that acknowledges on delivery cannot redeliver
+// work its holder died in the middle of, which is the whole difference between a queue and a
+// firehose.
+func (j *JetStream) EnsureConsumer(c Consumer) error {
+	want := &nats.ConsumerConfig{
+		Durable:        c.Name,
+		AckPolicy:      nats.AckExplicitPolicy,
+		AckWait:        time.Duration(c.AckWaitSeconds) * time.Second,
+		MaxDeliver:     c.MaxDeliver,
+		DeliverGroup:   c.Queue,
+		DeliverSubject: "",
+		Description:    c.Why,
+	}
+	switch len(c.Filters) {
+	case 0:
+	case 1:
+		want.FilterSubject = c.Filters[0]
+	default:
+		want.FilterSubjects = c.Filters
+	}
+	// A queue group needs a delivery subject: a pull consumer has no group, and declaring one
+	// without the other is refused by the server with a message that does not say which half is
+	// missing.
+	if c.Queue != "" || c.Push {
+		want.DeliverSubject = "_DELIVER." + c.Name
+	}
+
+	switch _, err := j.js.ConsumerInfo(c.Stream, c.Name); {
+	case err == nil:
+		if _, err := j.js.UpdateConsumer(c.Stream, want); err != nil {
+			return fmt.Errorf("bringing consumer %s on %s to match: %w", c.Name, c.Stream, err)
+		}
+		return nil
+	case errors.Is(err, nats.ErrConsumerNotFound):
+		if _, err := j.js.AddConsumer(c.Stream, want); err != nil {
+			return fmt.Errorf("creating consumer %s on %s: %w", c.Name, c.Stream, err)
+		}
+		return nil
+	default:
+		return fmt.Errorf("asking about consumer %s on %s: %w", c.Name, c.Stream, err)
+	}
+}
+
+func retentionOf(r Retention) nats.RetentionPolicy {
+	switch r {
+	case RetentionWorkQueue:
+		return nats.WorkQueuePolicy
+	default:
+		return nats.LimitsPolicy
+	}
+}
@@ -0,0 +1,71 @@
+package broker
+
+import (
+	"os"
+	"testing"
+)
+
+// Against a real server, because the questions here are all "does the server accept this" —
+// which a mock would answer by agreeing with whatever this file already believes.
+//
+// Skipped unless MESH_TEST_NATS names one, so the ordinary suite stays fast and offline:
+//
+//	docker run -d --rm --name t -p 14222:4222 nats:2.10-alpine -js
+//	MESH_TEST_NATS=nats://127.0.0.1:14222 go test ./internal/broker/ -run TestAgainstARealServer
+func TestAgainstARealServer(t *testing.T) {
+	url := os.Getenv("MESH_TEST_NATS")
+	if url == "" {
+		t.Skip("MESH_TEST_NATS unset")
+	}
+	js, err := Dial(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer js.Close()
+
+	t.Run("the mesh's own streams are accepted", func(t *testing.T) {
+		if err := AssertMeshStreams(js); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("asserting again changes nothing and fails nothing", func(t *testing.T) {
+		if err := AssertMeshStreams(js); err != nil {
+			t.Fatalf("the second assertion failed, so the controller cannot restart: %v", err)
+		}
+	})
+
+	t.Run("a seat's work queue is accepted beside them", func(t *testing.T) {
+		seats := []DeclaredSeat{{Name: "telegram-sender", Accepts: []string{"send"}}}
+		for _, s := range SeatStreams(seats) {
+			if err := js.EnsureStream(s); err != nil {
+				t.Fatal(err)
+			}
+		}
+		if c := AllOverlaps(seats); len(c) != 0 {
+			t.Fatalf("overlaps the server would refuse: %v", c)
+		}
+	})
+
+	t.Run("a module's consumer is accepted and is idempotent", func(t *testing.T) {
+		c, ok := ConsumerFor(Principal{Kind: KindModule, Node: "one", Module: "audit",
+			Consumes: []string{"shop.order.placed", "billing.invoice.sent"}, PasswordHash: "x"})
+		if !ok {
+			t.Fatal("no consumer derived")
+		}
+		if err := js.EnsureConsumer(c); err != nil {
+			t.Fatal(err)
+		}
+		if err := js.EnsureConsumer(c); err != nil {
+			t.Fatalf("the second assertion failed: %v", err)
+		}
+	})
+
+	t.Run("a holder's worker is accepted with its queue group", func(t *testing.T) {
+		c, _ := HolderConsumerFor("one", "telegram",
+			DeclaredSeat{Name: "telegram-sender", Accepts: []string{"send"}})
+		if err := js.EnsureConsumer(c); err != nil {
+			t.Fatal(err)
+		}
+	})
+}
@@ -1,366 +0,0 @@
-package broker
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"fmt"
-	"github.com/novox/mesh-controller/internal/envfile"
-	"io"
-	"net/http"
-	"net/url"
-	"regexp"
-	"strings"
-	"time"
-)
-
-// The mesh runs the broker, so there is no chicken-and-egg in a node needing an account before it
-// can connect: the account is created when the token is issued, and the one-time secret in that
-// token IS the password. A node's first connection is already authenticated, and enrolment is
-// what happens over it.
-//
-// novox/hq ADR 0004's *a node holds its own identity and nothing else* is why the account is per
-// node rather than shared. A shared enrolment account would let any node consume another's queue,
-// which is the shared-credential fault that record exists to remove, reappearing at the transport.
-
-// ManagementVar holds the broker's management API, credentials included.
-const ManagementVar = "MESH_BROKER_MANAGEMENT"
-
-// safeName is what a node may be called at the broker.
-//
-// The name goes into a URL path and into permission patterns, which are regular expressions. A
-// name carrying a `.` or a `*` would silently widen what that node may reach — so it is
-// constrained here rather than escaped later, because an escape that is forgotten once is a node
-// reading everybody's queues.
-var safeName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,62}$`)
-
-// Management is the broker's administrative interface.
-type Management struct {
-	base   *url.URL
-	client *http.Client
-}
-
-// ManagementFromEnvironment reads where the management API is, if it is configured.
-//
-// On the port MESH_BROKER_MANAGEMENT_PORT names when the node moved it (novox/hq 04-ISSUES/102);
-// the URL's own port otherwise.
-func ManagementFromEnvironment() (*Management, error) {
-	raw, err := envfile.Placed(ManagementVar)
-	if err != nil {
-		return nil, err
-	}
-	if raw == "" {
-		return nil, ErrNotConfigured
-	}
-	base, err := url.Parse(raw)
-	if err != nil || base.Host == "" {
-		// The value carries a password, so it is not quoted back.
-		return nil, fmt.Errorf("%s is not a usable URL", ManagementVar)
-	}
-	return &Management{base: base, client: &http.Client{Timeout: 15 * time.Second}}, nil
-}
-
-// QueueFor is the queue a node consumes from. One per node, named after it.
-func QueueFor(node string) string { return "node." + node }
-
-// ExchangeName is where nodes publish what they have to say. One exchange, and the control plane
-// is the only consumer behind it (novox/hq ADR 0006 — one consumer, so two cannot silently split
-// the traffic between them).
-const ExchangeName = "mesh"
-
-// BuildQueueName is where build work waits. Duplicated from `link` rather than imported, for the
-// same reason QueueFor above is: this package must not depend on the one that uses it, and a
-// constant that differed would be caught by the test that asserts they agree.
-const BuildQueueName = "builds"
-
-// The events bus (novox/hq ADR 0042): one topic exchange every event rides, a second for tool
-// RPC kept apart, and a dead-letter home for a poison event. The foundation owns these — a module's
-// account cannot declare them, only bind its own queue to the events one.
-const (
-	EventsExchangeName = "mesh.events"
-	RPCExchangeName    = "mesh.rpc"
-	DeadExchangeName   = "mesh.events.dead"
-)
-
-// ModuleQueueFor is the durable queue a module consumes its events from — one per module per node
-// (novox/hq ADR 0042), named so the account that may read it is exactly this module's.
-func ModuleQueueFor(node, module string) string { return node + "." + module + ".events" }
-
-// modulePermissions is a module's authority on the bus, derived from its manifest (novox/hq
-// ADR 0043): what it consumes and what it emits, and nothing else. Pure, so the scope is tested as
-// patterns without a broker — the way a builder's is.
-//
-// A note on the limit: the broker's write permission is per exchange, not per routing key (LavinMQ
-// has no topic permissions), so an emitting module is granted the events exchange whole. ADR 0042's
-// origin reservation — a module publishes only under `module.<self>.*` — is stamped by the sdk, not
-// enforced here; that gap is the broker's, and is recorded rather than hidden. A pure consumer like
-// the audit logger is unaffected: it is granted no write to the exchange at all.
-func modulePermissions(node, module string, emits, consumes []string) (configure, write, read string) {
-	queue := regexp.QuoteMeta(ModuleQueueFor(node, module))
-	events := regexp.QuoteMeta(EventsExchangeName)
-	rpc := regexp.QuoteMeta(RPCExchangeName)
-	// A module serves each of its tools on its own queue, namespaced by the module (novox/hq
-	// ADR 0047) — serve.<module>.<tool> — so the account may declare, bind and read exactly its own,
-	// and no other module's.
-	serve := "serve\\." + regexp.QuoteMeta(module) + "\\..*"
-
-	// Declare its own events queue and its own tool serve queues.
-	configure = "^(" + queue + "|" + serve + ")$"
-
-	// Write to bind its queue and serve queues (binding is a write on the queue), and to the RPC
-	// exchange to publish replies (ADR 0047: replies ride mesh.rpc, never the default exchange, which
-	// would let it publish into any queue). To the events exchange only if it emits.
-	writes := []string{queue, serve, rpc}
-	if len(emits) > 0 {
-		writes = append(writes, events)
-	}
-	write = "^(" + strings.Join(writes, "|") + ")$"
-
-	// Read its own queue and serve queues to consume them, and the RPC exchange to bind its serve
-	// queues onto. The events exchange to bind onto only if it consumes.
-	reads := []string{queue, serve, rpc}
-	if len(consumes) > 0 {
-		reads = append(reads, events)
-	}
-	read = "^(" + strings.Join(reads, "|") + ")$"
-	return configure, write, read
-}
-
-// CreateModuleAccount gives an assigned module its own broker account, scoped by what it emits and
-// consumes (novox/hq ADR 0043). The account name carries the node so the same module on two machines
-// holds two accounts, each sealed to its own; the permissions carry the module so one module cannot
-// read another's queue. Generic — the builder is one instance of this rule, not a separate kind.
-func (m *Management) CreateModuleAccount(ctx context.Context, node, module, password string, emits, consumes []string) (string, error) {
-	if !safeName.MatchString(node) {
-		return "", fmt.Errorf("%q cannot be part of a broker account: it is a permission pattern", node)
-	}
-	if !safeName.MatchString(module) {
-		return "", fmt.Errorf("%q cannot be part of a broker account: it is a permission pattern", module)
-	}
-	account := node + "-" + module
-	if !safeName.MatchString(account) {
-		return "", fmt.Errorf("%q is not a usable broker account name", account)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(account),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return "", fmt.Errorf("cannot create the broker account for %s on %s: %w", module, node, err)
-	}
-
-	configure, write, read := modulePermissions(node, module, emits, consumes)
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(account), map[string]string{
-		"configure": configure, "write": write, "read": read,
-	}); err != nil {
-		return "", fmt.Errorf("cannot scope the broker account for %s on %s: %w", module, node, err)
-	}
-	return account, nil
-}
-
-// EnsureModuleQueue declares a consuming module's queue with its dead-letter exchange, idempotently.
-// The foundation declares it because a scoped module account may not: the broker refuses a queue with
-// a dead-letter exchange to a non-administrator (novox/hq ADR 0043), so a consumer passively checks
-// the queue the mesh made rather than declaring its own.
-func (m *Management) EnsureModuleQueue(ctx context.Context, node, module string) error {
-	queue := ModuleQueueFor(node, module)
-	if err := m.put(ctx, "/api/queues/%2f/"+url.PathEscape(queue), map[string]any{
-		"durable":   true,
-		"arguments": map[string]any{"x-dead-letter-exchange": DeadExchangeName},
-	}); err != nil {
-		return fmt.Errorf("cannot declare the queue for %s on %s: %w", module, node, err)
-	}
-	return nil
-}
-
-// EnsureEventExchanges declares the bus's exchanges and the dead-letter home, idempotently. The
-// foundation owns them (a module's account may not declare an exchange), and a dead-letter exchange
-// with no queue behind it drops what it receives — so a durable queue bound to `#` retains a poison
-// event for inspection, which is the whole reason the trail exists.
-func (m *Management) EnsureEventExchanges(ctx context.Context) error {
-	for _, exchange := range []string{EventsExchangeName, RPCExchangeName, DeadExchangeName} {
-		if err := m.put(ctx, "/api/exchanges/%2f/"+url.PathEscape(exchange),
-			map[string]any{"type": "topic", "durable": true}); err != nil {
-			return fmt.Errorf("cannot declare the %s exchange: %w", exchange, err)
-		}
-	}
-	if err := m.put(ctx, "/api/queues/%2f/"+url.PathEscape(DeadExchangeName),
-		map[string]any{"durable": true}); err != nil {
-		return fmt.Errorf("cannot declare the dead-letter queue: %w", err)
-	}
-	if err := m.post(ctx, "/api/bindings/%2f/e/"+url.PathEscape(DeadExchangeName)+
-		"/q/"+url.PathEscape(DeadExchangeName), map[string]string{"routing_key": "#"}); err != nil {
-		return fmt.Errorf("cannot bind the dead-letter queue: %w", err)
-	}
-	return nil
-}
-
-// CreateNodeAccount gives a node its own broker account, with the token's secret as the password.
-//
-// Scoped so a node can reach its own queue and the one exchange, and nothing else. The patterns
-// are anchored: a node called `laptop` must not be able to read `laptop-of-somebody-else`.
-func (m *Management) CreateNodeAccount(ctx context.Context, node, password string) error {
-	if !safeName.MatchString(node) {
-		return fmt.Errorf(
-			"%q cannot be a broker account name: it becomes part of a permission pattern, so it "+
-				"is lower-case letters, digits and dashes", node)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(node),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return fmt.Errorf("cannot create the broker account for %s: %w", node, err)
-	}
-
-	queue := regexp.QuoteMeta(QueueFor(node))
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(node), map[string]string{
-		"configure": "^" + queue + "$",
-		"write":     "^(" + regexp.QuoteMeta(ExchangeName) + "|" + queue + ")$",
-		"read":      "^" + queue + "$",
-	}); err != nil {
-		return fmt.Errorf("cannot scope the broker account for %s: %w", node, err)
-	}
-	return nil
-}
-
-// CreateBuilderAccount scopes an account to taking build work and answering it.
-//
-// **A build machine is not a node**, and giving it a node's account would let it read another
-// machine's declarations. What it needs is narrower and different: read the build queue, and
-// write to the exchange and to whatever temporary queue an asker is waiting on.
-//
-// The reply queues are the reason `write` is not simply the exchange. `RequestBuild` declares an
-// exclusive queue with a generated name and waits on it, so a builder that could not write to it
-// could take work and never answer — which is the failure that looks like a builder that is not
-// running.
-func (m *Management) CreateBuilderAccount(ctx context.Context, name, password string) error {
-	if !safeName.MatchString(name) {
-		return fmt.Errorf(
-			"%q cannot be a broker account name: it becomes part of a permission pattern, so it "+
-				"is lower-case letters, digits and dashes", name)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(name),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return fmt.Errorf("cannot create the broker account for %s: %w", name, err)
-	}
-
-	builds := regexp.QuoteMeta(BuildQueueName)
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(name), map[string]string{
-		// It declares the build queue, because whichever builder starts first must be able to —
-		// and a queue nobody may declare is a queue that exists only if the control plane has
-		// already run, which makes the order they start in matter.
-		"configure": "^" + builds + "$",
-		// Two exchanges, and nothing else. **Not the default exchange**: permission there is
-		// granted per exchange rather than per queue, so a builder allowed to use it could
-		// publish into any node's queue — the privilege a build machine most obviously should
-		// not have. Answers go through the node exchange; announcing what was built goes through
-		// the events exchange, which is a different act with a different audience (novox/hq
-		// ADR 0072). A builder that could answer and not announce would leave the module graph
-		// knowing less than the registry does.
-		"write": "^(" + regexp.QuoteMeta(ExchangeName) + "|" + regexp.QuoteMeta(EventsExchangeName) + ")$",
-		// The build queue and nothing else. Not another machine's declarations.
-		"read": "^" + builds + "$",
-	}); err != nil {
-		return fmt.Errorf("cannot scope the broker account for %s: %w", name, err)
-	}
-	return nil
-}
-
-// RemoveNodeAccount withdraws a node's access.
-func (m *Management) RemoveNodeAccount(ctx context.Context, node string) error {
-	if !safeName.MatchString(node) {
-		return fmt.Errorf("%q is not a broker account name", node)
-	}
-	return m.do(ctx, http.MethodDelete, "/api/users/"+url.PathEscape(node), nil)
-}
-
-// Accounts lists the broker's users, so a picture can be read from the system rather than assumed
-// (novox/hq ADR 0018).
-func (m *Management) Accounts(ctx context.Context) ([]string, error) {
-	body, err := m.get(ctx, "/api/users")
-	if err != nil {
-		return nil, err
-	}
-	var users []struct {
-		Name string `json:"name"`
-	}
-	if err := json.Unmarshal(body, &users); err != nil {
-		return nil, err
-	}
-	names := make([]string, 0, len(users))
-	for _, u := range users {
-		names = append(names, u.Name)
-	}
-	return names, nil
-}
-
-func (m *Management) put(ctx context.Context, path string, body any) error {
-	return m.do(ctx, http.MethodPut, path, body)
-}
-
-func (m *Management) post(ctx context.Context, path string, body any) error {
-	return m.do(ctx, http.MethodPost, path, body)
-}
-
-func (m *Management) get(ctx context.Context, path string) ([]byte, error) {
-	request, err := m.request(ctx, http.MethodGet, path, nil)
-	if err != nil {
-		return nil, err
-	}
-	response, err := m.client.Do(request)
-	if err != nil {
-		return nil, err
-	}
-	defer response.Body.Close()
-	if response.StatusCode >= 300 {
-		return nil, fmt.Errorf("the broker's management API answered %s to GET %s",
-			response.Status, path)
-	}
-	return io.ReadAll(io.LimitReader(response.Body, 1<<20))
-}
-
-func (m *Management) do(ctx context.Context, method, path string, body any) error {
-	request, err := m.request(ctx, method, path, body)
-	if err != nil {
-		return err
-	}
-	response, err := m.client.Do(request)
-	if err != nil {
-		return err
-	}
-	defer response.Body.Close()
-	if response.StatusCode >= 300 {
-		detail, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
-		return fmt.Errorf("the broker's management API answered %s to %s %s: %s",
-			response.Status, method, path, strings.TrimSpace(string(detail)))
-	}
-	return nil
-}
-
-func (m *Management) request(ctx context.Context, method, path string, body any) (*http.Request, error) {
-	var payload io.Reader
-	if body != nil {
-		raw, err := json.Marshal(body)
-		if err != nil {
-			return nil, err
-		}
-		payload = bytes.NewReader(raw)
-	}
-
-	// Path joined by hand rather than through url.Parse: %2f is the default vhost and must reach
-	// the broker still encoded. Parsing would decode it to a slash and address a different route.
-	target := strings.TrimSuffix(m.base.String(), "/")
-	if user := m.base.User; user != nil {
-		target = strings.TrimSuffix(m.base.Scheme+"://"+m.base.Host, "/")
-	}
-	request, err := http.NewRequestWithContext(ctx, method, target+path, payload)
-	if err != nil {
-		return nil, err
-	}
-	if user := m.base.User; user != nil {
-		password, _ := user.Password()
-		request.SetBasicAuth(user.Username(), password)
-	}
-	if body != nil {
-		request.Header.Set("Content-Type", "application/json")
-	}
-	return request, nil
-}
@@ -1,96 +0,0 @@
-package broker_test
-
-import (
-	"context"
-	"encoding/json"
-	"net/http"
-	"net/http/httptest"
-	"regexp"
-	"strings"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/broker"
-)
-
-// The audit logger consumes everything and emits nothing. Its account must let it declare and read
-// its own queue and read the events exchange to bind onto — and must not reach another module's
-// queue, nor grant any write to the events exchange (novox/hq ADR 0043).
-func TestAConsumerReadsItsOwnQueueAndTheEventsExchangeAndNoOthers(t *testing.T) {
-	// Rebuilt through CreateModuleAccount's own path by asking for the same scope it would apply.
-	// The queue this module reads:
-	mine := broker.ModuleQueueFor("anchor", "audit-logger")
-	other := broker.ModuleQueueFor("anchor", "plex")
-
-	read := scope(t, "read", "anchor", "audit-logger", nil, []string{"#"})
-	if !read.MatchString(mine) {
-		t.Error("the audit logger may not read its own queue, so it consumes nothing")
-	}
-	if !read.MatchString(broker.EventsExchangeName) {
-		t.Error("the audit logger may not read the events exchange, so it cannot bind onto it")
-	}
-	if read.MatchString(other) {
-		t.Error("the audit logger may read another module's queue")
-	}
-
-	// It emits nothing, so it is granted no write to the events exchange — only its own queue, to bind.
-	write := scope(t, "write", "anchor", "audit-logger", nil, []string{"#"})
-	if write.MatchString(broker.EventsExchangeName) {
-		t.Error("a pure consumer was granted write to the events exchange")
-	}
-	if !write.MatchString(mine) {
-		t.Error("the audit logger may not write to its own queue, so it cannot bind it")
-	}
-}
-
-// An emitter is granted the events exchange to write; a consumer is not.
-func TestAnEmitterMayWriteTheEventsExchangeAndAConsumerMayNot(t *testing.T) {
-	emitter := scope(t, "write", "anchor", "umami", []string{"module.umami.site.created"}, nil)
-	if !emitter.MatchString(broker.EventsExchangeName) {
-		t.Error("an emitting module may not write the events exchange, so it cannot emit")
-	}
-}
-
-// scope reconstructs one of the three permission patterns CreateModuleAccount would apply, by
-// reading it back from a captured request against a stub management API.
-func scope(t *testing.T, which, node, module string, emits, consumes []string) *regexp.Regexp {
-	t.Helper()
-	pat := capturePermission(t, which, node, module, emits, consumes)
-	re, err := regexp.Compile(pat)
-	if err != nil {
-		t.Fatalf("the %s pattern does not compile: %v", which, err)
-	}
-	return re
-}
-
-// capturePermission runs CreateModuleAccount against a stub management API and returns the pattern
-// it set for `which` ("configure"/"write"/"read"). The scope is tested where it is applied, not
-// reconstructed by the test — so a change to the mapping cannot pass a test that hard-codes the old
-// one.
-func capturePermission(t *testing.T, which, node, module string, emits, consumes []string) string {
-	t.Helper()
-	var captured map[string]string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if strings.HasPrefix(r.URL.Path, "/api/permissions/") {
-			_ = json.NewDecoder(r.Body).Decode(&captured)
-		}
-		w.WriteHeader(http.StatusNoContent)
-	}))
-	defer server.Close()
-
-	t.Setenv(broker.ManagementVar, server.URL)
-	m, err := broker.ManagementFromEnvironment()
-	if err != nil {
-		t.Fatalf("stub management not usable: %v", err)
-	}
-	if _, err := m.CreateModuleAccount(context.Background(), node, module, "pw", emits, consumes); err != nil {
-		t.Fatalf("CreateModuleAccount: %v", err)
-	}
-	if captured == nil {
-		t.Fatal("no permissions were set")
-	}
-	pattern, ok := captured[which]
-	if !ok {
-		t.Fatalf("no %s permission was set; got %v", which, captured)
-	}
-	return pattern
-}
@@ -0,0 +1,589 @@
+// Composing the bus's own configuration.
+//
+// An account is *composed*, never called for: the controller writes accounts, users and
+// per-subject permissions into one file the host keeps current, and the server reloads it in
+// place (novox/hq ADR 0106 — never through a management API; design 25 §4).
+//
+// Everything here is pure. Given the principals, it returns the file's text — so the whole of the
+// mesh's authority model is testable as strings, with no server.
+//
+// **Permissions are per subject, so a module's own name is the server's to enforce.** ADR 0042
+// reserves a module's origin — it publishes only under its own name — and here that is a refusal
+// rather than something a library promises.
+package broker
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+// A Kind is what a principal is, which decides the shape of its authority rather than its
+// contents: a module's comes from its declaration, a host's from its node, and the controller's
+// and the enrolment user's are fixed.
+type Kind string
+
+const (
+	KindModule     Kind = "module"
+	KindNode       Kind = "node"
+	KindController Kind = "controller"
+	KindEnrolment  Kind = "enrolment"
+	// KindPerson is somebody reaching the mesh's tools from a workstation (design 25 §7). Its
+	// authority is a list of tools and nothing else — not control, not declarations, not builds,
+	// and no ability to answer anything, because a person asks.
+	KindPerson Kind = "person"
+)
+
+// Seat is a role on the bus as a principal relates to it: the subjects it accepts, and those it
+// emits (novox/hq ADR 0118, design 29 §5).
+type Seat struct {
+	Name     string
+	Accepts  []string
+	Emits    []string
+	Serves   []string
+	Versions []string // protocol versions served beside the current one; empty for v1 only
+}
+
+// A Principal is one user of the bus. Its permissions are derived from what it declares and
+// nothing else (novox/hq ADR 0043), over the three namespaces of design 29 §2: its own, the seats
+// it holds, and the seats it uses.
+type Principal struct {
+	Kind   Kind
+	Node   string
+	Module string
+
+	Emits    []string
+	Consumes []string
+	Serves   []string
+
+	Holds []Seat
+	Uses  []Seat
+	// Watches are seats whose events this principal consumes. Separate from Consumes because a
+	// role's event lives under the seat's namespace and not a module's, and this package cannot tell
+	// a seat's name from a module's by looking at it — whoever resolved the declaration can, and
+	// does (novox/hq ADR 0121).
+	//
+	// **Found by a consumer reading nothing.** The catalogue consumes the build machine's outcome;
+	// with that name read as a module's, its subscription pointed at `mesh.mod.mesh-build-machine.…`,
+	// a namespace no such module owns. Every service started and the graph stayed empty.
+	Watches []Seat
+
+	// Invokes are the tools a person may call, as `<module>.<tool>`; a single `*` is every tool,
+	// for an administrator. Only meaningful for KindPerson.
+	//
+	// **A list, not a role.** A person is not a module and holds no seat: nothing is addressed
+	// to them, nothing is delivered to them, and they have no durable consumer to acknowledge.
+	// What they have is permission to ask.
+	Invokes []string
+
+	// PasswordHash is the bcrypt hash the mesh minted. The plaintext is sealed to the principal
+	// and never appears here: this file is written to a node's disk and read by a server, and a
+	// secret that can be read from a configuration file is a secret with a wider blast radius
+	// than the one it protects (novox/hq design 29 §10).
+	PasswordHash string
+}
+
+// meshSeatsTheControllerUses are the roles the mesh's own flows submit work to. Named rather than
+// derived from the seat set: the controller is not a module and declares no `uses`, so its side of a
+// seat has to be stated, and a list is what makes "which roles does the mesh itself talk to" answerable.
+var meshSeatsTheControllerUses = []string{"mesh-build-machine"}
+
+// enrolmentPrefix is the space every enrolling node's user and inbox live under, so the one place the
+// controller may answer an enrolment is derived from the same constant the user is named from.
+const enrolmentPrefix = "enrol"
+
+// safeSubject refuses anything that would change the meaning of a subject rather than sit inside
+// one. A name carrying a dot would silently widen a permission by adding a token; a name carrying
+// `>` or `*` would widen it to a wildcard, which is the whole authority model gone.
+var safeSubject = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
+
+// Username is how a principal is named to the server. The node is part of it, so the same module
+// on two machines holds two users, each sealed to its own — the rule management.go already
+// applies, kept.
+func (p Principal) Username() string {
+	switch p.Kind {
+	case KindPerson:
+		return "person." + p.Module
+	case KindModule:
+		return p.Node + "." + p.Module
+	case KindNode:
+		return "node." + p.Node
+	case KindController:
+		return "controller"
+	case KindEnrolment:
+		// Per token, not one shared user. **The inbox is the reason**: with a single `enrolment`
+		// user every machine enrolling at once could read every other's answer, and an answer
+		// carries that node's credentials sealed to it. Design 25 §6 says the inbox a token
+		// derives, and a permission belongs to a user, so the user is per token.
+		//
+		// Named after the node, which **is** the token's id: a token is issued for a node record,
+		// the mesh holds one live claim per record, and the node's name is the one identifier both
+		// sides already have before anything else is agreed. It is also exactly what the other
+		// transport does, where the account is named after the node and the secret is its password.
+		return enrolmentPrefix + "." + p.Node
+	}
+	return ""
+}
+
+// inbox is a principal's own reply space. No user is ever granted a bare `_INBOX.>` (design 25
+// §4): with one account, inbox privacy is the permission list or it is nothing, so each user's
+// inbox is derived from its own identity and its permissions name that prefix and no other.
+func (p Principal) inbox() string { return "_INBOX." + p.Username() + ".>" }
+
+// Permissions is what a principal may publish and subscribe, and whether it may answer.
+type Permissions struct {
+	Publish   []string
+	Subscribe []string
+	// AllowResponses lets a principal reply to a request it received, on the reply subject that
+	// request carried, once.
+	//
+	// **This is what makes scoped inboxes possible at all**, and design 25 §4 did not say it. If
+	// every user's inbox is private to it, a module serving a tool cannot publish the answer —
+	// the answer goes to the *caller's* inbox, which the responder has no permission for. The two
+	// ways out are granting responders `_INBOX.>`, which is precisely the blanket grant §4
+	// refuses, or this: the server itself permits one reply to the subject of a message the user
+	// actually received, and nothing else. The authority is bounded by having been asked.
+	AllowResponses bool
+}
+
+// PermissionsFor derives a principal's authority. Pure, and the only place authority is decided:
+// a permission that cannot be derived from a declaration is a permission nobody can explain.
+func PermissionsFor(p Principal) (Permissions, error) {
+	for _, part := range []struct{ what, value string }{
+		{"node", p.Node}, {"module", p.Module},
+	} {
+		if part.value == "" {
+			continue
+		}
+		if !safeSubject.MatchString(part.value) {
+			return Permissions{}, fmt.Errorf(
+				"%q cannot be part of a subject: a permission is a subject pattern, and this would widen it", part.value)
+		}
+	}
+
+	var pub, sub []string
+	switch p.Kind {
+	case KindController:
+		// The controller owns the mesh's own traffic and the streams. It is the only writer of
+		// stream definitions (design 25 §3), so it alone reaches the JetStream API.
+		pub = []string{"mesh.control.>", "mesh.node.>", "$JS.API.>"}
+		// **And where its consumers deliver.** A push consumer delivers on `_DELIVER.<its name>`,
+		// and a client bound to it subscribes exactly that; the server refused it for every
+		// principal the first time one bound a consumer (2026-09-28). Each kind below is granted
+		// its own consumers' delivery subjects and no other's.
+		sub = []string{"mesh.control.>", "$JS.API.>", "_DELIVER." + ControllerName, "_DELIVER." + ControllerName + ".>"}
+
+		// Work the mesh's own flows submit to a role, and the outcomes they wait on (ADR 0121). A
+		// build is the one today: the controller asks, and reads the answer from the seat's event
+		// like the catalogue does — which is why no holder needs to publish into anybody's inbox.
+		for _, seat := range meshSeatsTheControllerUses {
+			pub = append(pub, "mesh.seat."+seat+".accept.>")
+		}
+		// Every module's tools: **the control plane is the way in** (novox/hq ADR 0095). A person
+		// or an agent asks through it and every question passes one process where an audit
+		// belongs — so it, alone among principals, may call any tool by name. The first `ask` on
+		// the new bus was refused the publish (2026-09-28).
+		pub = append(pub, "mesh.mod.*.tool.>")
+
+		// The two events it reacts to, and its ack subject on the stream they arrive from
+		// (streams.go). **Each named, not a pattern**: `mesh.mod.*.event.>` would make the
+		// controller a subscriber to every event in the mesh, and its permission list would stop
+		// saying what it is for. The ack grant below is scoped per stream because the controller's
+		// consumer name is the same on both and `$JS.ACK.CONTROL.controller.>` does not cover a
+		// delivery from EVENTS — a consumer that cannot ack has every message redelivered for
+		// ever, refused by the list it already has.
+		sub = append(sub, ControllerFollows...)
+		pub = append(pub, "$JS.ACK.EVENTS."+ControllerName+".>")
+
+		// **Where an enrolment's answer goes**, and `allow_responses` does not cover it. That
+		// permits one reply to the reply subject of a message the user received — and a message a
+		// JetStream consumer delivers has had that field claimed for the consumer's own ack address
+		// (design 25 §2), so the address the controller actually answers is the one the request
+		// carried in its payload, which is not a reply subject as the server understands it.
+		//
+		// Verified against a real server before this line existed: the answer was refused with
+		// "Permissions Violation for Publish to _INBOX.enrol.anchor…", and every enrolment on the
+		// mesh would have timed out while the controller logged success.
+		//
+		// **The enrolment inbox space, not a blanket `_INBOX.>`.** Design 25 §4 refuses that, and
+		// this is not it: nothing but an enrolling node ever subscribes under this prefix, each
+		// scoped to its own token's, so the controller publishing here is the mesh answering
+		// enrolments and can reach nothing else.
+		pub = append(pub, "_INBOX."+enrolmentPrefix+".>")
+
+	case KindPerson:
+		// Tools, and nothing else. Every subject a person may publish is a tool call; a person
+		// who could publish an event would be able to claim a module said something.
+		for _, t := range p.Invokes {
+			if t == "*" {
+				pub = append(pub, "mesh.mod.*.tool.>")
+				continue
+			}
+			module, tool, ok := strings.Cut(t, ".")
+			if !ok {
+				return Permissions{}, fmt.Errorf(
+					"%q does not name a tool: a person invokes <module>.<tool>, or * for every one", t)
+			}
+			pub = append(pub, "mesh.mod."+module+".tool."+tool)
+		}
+
+	case KindEnrolment:
+		// A leaked token is useless for anything but enrolling: it cannot read a declaration, hear
+		// an event, or subscribe any inbox but the one its own token derives (design 25 §6).
+		//
+		// **The inbox was missing and the handshake could not have completed without it.** An
+		// enrolling node publishes its request and waits on an address it states in the payload;
+		// with nothing to subscribe it waits out its timeout against a mesh that answered. Its own
+		// and no wider: `_INBOX.enrol.<node>.>`, so what is sealed to one machine cannot be read by
+		// another enrolling beside it.
+		if p.Node == "" {
+			// Refused rather than composed into `_INBOX.enrol..>`, which is a subject with an empty
+			// token in it — and worse, one every nameless enrolment user would share. A shared
+			// enrolment inbox is one machine able to read the credentials sealed to another.
+			return Permissions{}, errors.New(
+				"an enrolment user names no node, so its inbox would be shared with every other " +
+					"enrolment: a token is issued for a node record, and that record's name is " +
+					"the token's id")
+		}
+		pub = []string{"mesh.control.enrol"}
+		sub = []string{p.inbox()}
+
+	case KindNode:
+		// A host publishes its own node's control traffic and subscribes its own declaration —
+		// and nothing of any other node's.
+		// And binding to its consumer, which asks the server about it (CONSUMER.INFO) — the one
+		// thing the host does that nothing granted. Found the first time a machine dialled a
+		// permissioned server: "this node cannot read its declarations" (2026-09-28). The ack and
+		// the inbox are granted below with every principal's.
+		pub = []string{
+			"mesh.control." + p.Node + ".>",
+			"$JS.API.CONSUMER.INFO.NODES." + p.Node,
+		}
+		sub = []string{"mesh.node." + p.Node + ".declare", "_DELIVER." + p.Node}
+
+	case KindModule:
+		// 1. Its own namespace: it publishes its events there and serves its tools there. Nothing
+		//    else may publish into it, so an event's source is a fact the server enforces rather
+		//    than a claim in the body (design 29 §2).
+		own := "mesh.mod." + p.Module
+		for _, e := range p.Emits {
+			pub = append(pub, own+".event."+e)
+		}
+		// Every tool under its own name, not a list: the tools a module serves are what its code
+		// answers, and a second copy of that list in the manifest would be a second source of
+		// truth for the mesh to keep in step (2026-09-28: every module that served a tool was
+		// refused the subscription, because none had written the list twice). Nothing is given
+		// away — no other principal may subscribe this namespace, and a caller's authority is
+		// still granted per tool, by name, on the publish side.
+		sub = append(sub, own+".tool.>")
+
+		// 2. What it consumes, by the emitter's own subject — an event is addressed to its
+		//    emitter, because the emitter's identity is the meaning (ADR 0118).
+		for _, c := range p.Consumes {
+			subject, err := consumedSubject(c)
+			if err != nil {
+				return Permissions{}, err
+			}
+			sub = append(sub, subject)
+		}
+
+		// 2b. Events of a role it watches, under the seat's own namespace. Subscribe only: watching a
+		//     role is hearing what it announced, not taking part in it.
+		for _, w := range p.Watches {
+			for _, e := range w.Emits {
+				sub = append(sub, seatSubject(w, "event", e))
+			}
+		}
+
+		// 2c. Its own consumer, which it **pulls**: the runtime asks for the next message and is
+		//     answered on its own inbox, so what it needs is to ask about the consumer and to ask it
+		//     for messages — its own consumer's name, and no other's. Pulled rather than pushed
+		//     because that is the one shape a runtime's client binds without creating anything; the
+		//     controller and the hosts are pushed to. Named here rather than through ConsumerFor,
+		//     which asks for these permissions to build the consumer and would ask forever. A
+		//     subject for a consumer that turns out not to exist grants nothing anybody can use.
+		pub = append(pub,
+			"$JS.API.CONSUMER.INFO."+consumerStream(p)+"."+consumerDurable(p),
+			"$JS.API.CONSUMER.MSG.NEXT."+consumerStream(p)+"."+consumerDurable(p))
+
+		// 3. Seats it holds: full participation.
+		for _, s := range p.Holds {
+			// Taking work from the role's queue: the worker consumer it binds (asked about,
+			// delivered on, acknowledged), each on the seat's own stream. The first machine to
+			// take work over the new bus was refused the asking (2026-09-28).
+			worker := "SEAT_" + upperSnake(s.Name) + "_worker"
+			stream := seatStreamName(s.Name)
+			sub = append(sub, "_DELIVER."+worker)
+			pub = append(pub, "$JS.API.CONSUMER.INFO."+stream+"."+worker, "$JS.ACK."+stream+"."+worker+".>")
+			for _, a := range s.Accepts {
+				sub = append(sub, seatSubject(s, "accept", a))
+			}
+			for _, e := range s.Emits {
+				pub = append(pub, seatSubject(s, "event", e))
+			}
+			for _, t := range s.Serves {
+				sub = append(sub, seatSubject(s, "tool", t))
+			}
+		}
+
+		// 4. Seats it uses: publish only, and only the accepts half. A caller cannot subscribe a
+		//    seat's inbound subject and watch other modules' traffic, nor publish its outbound
+		//    events and lie about outcomes (design 29 §2).
+		for _, s := range p.Uses {
+			for _, a := range s.Accepts {
+				pub = append(pub, seatSubject(s, "accept", a))
+			}
+			for _, t := range s.Serves {
+				pub = append(pub, seatSubject(s, "tool", t))
+			}
+		}
+	}
+
+	if p.Kind == KindPerson {
+		// An inbox to hear answers in, and nothing else. No ack subject: a person has no durable
+		// consumer, because nothing is delivered to a person — they ask and are answered.
+		sub = append(sub, p.inbox())
+	}
+
+	if p.Kind == KindModule || p.Kind == KindNode || p.Kind == KindController {
+		// Its own reply space, and nothing wider.
+		sub = append(sub, p.inbox())
+
+		// Acking a JetStream delivery is a publish to that consumer's own ack address — a
+		// different subject from anything the consumer subscribes. Without it every message a
+		// module received would be redelivered forever, refused by the permission list it already
+		// has (design 25 §4). Scoped to this principal's own consumer name, so it can ack its own
+		// deliveries and no other's.
+		pub = append(pub, "$JS.ACK."+consumerStream(p)+"."+consumerDurable(p)+".>")
+	}
+
+	sort.Strings(pub)
+	sort.Strings(sub)
+	return Permissions{
+		Publish:   pub,
+		Subscribe: sub,
+		// A module answers what it was asked — a tool call reaches it on its own namespace, so the
+		// authority is bounded by having been asked — and so does the controller. A node and a
+		// person are never asked anything, and are granted nothing here.
+		AllowResponses: p.Kind == KindModule || p.Kind == KindController,
+	}, nil
+}
+
+// seatSubject places a seat's verb under the kind of traffic it is.
+//
+// **The kind token is load-bearing, not decoration.** A stream is defined by a subject filter, so
+// without it a stream over a seat or a module's namespace would capture that namespace's *tool*
+// traffic too — and a tool call must never be persisted (design 25 §3: tools stay on core NATS).
+// Found while defining the streams: the first draft of design 29 had one namespace per module
+// with no kind, which reads well and cannot be filtered.
+//
+// A seat serving more than its current protocol version carries the version as a token
+// (design 29 §8): the seat stays one role, and v1 and v2 run beside each other until nothing is
+// bound to the old one.
+func seatSubject(s Seat, kind, verb string) string {
+	return "mesh.seat." + s.Name + "." + kind + "." + verb
+}
+
+// consumerStream and consumerDurable are the two halves of a consumer's identity, and they are
+// two functions because conflating them was a real bug.
+//
+// **A durable name may not contain a dot; an ack subject is built from two names that do.** The
+// server acknowledges on `$JS.ACK.<stream>.<consumer>.…`, so a single string "EVENTS.one_audit"
+// reads correctly inside the permission and is rejected as a consumer name — *nats: invalid
+// consumer name*. Caught against a running server, and worth the comment because the shape of
+// the failure if it had not been is the one design 25 §4 warns about: a consumer that cannot ack
+// has every message redelivered forever, and its permission list looks right while it happens.
+//
+// They are derived here, beside the permission that must match them, because two places deriving
+// the same name is how a module ends up unable to ack its own deliveries.
+// consumedSubject is where a consumed event lands, from the local pattern a module declared.
+//
+// **The mesh's wildcards become this transport's** (design 29 §1): `*` is one name on both, and `**`
+// — the rest — is `>` here. A module writes neither transport's spelling, so a manifest stays correct
+// when the wire changes, which is the whole reason names are local.
+//
+// `**` on its own is every event from every module: the emitter is any, the event is anything. An
+// audit logger wants exactly that and says so in one token.
+func consumedSubject(pattern string) (string, error) {
+	if pattern == catalogueTheRest {
+		return "mesh.mod.*.event.>", nil
+	}
+	emitter, event, named := strings.Cut(pattern, ".")
+	if !named || emitter == "" || event == "" {
+		return "", fmt.Errorf(
+			"%q does not name an emitter and an event: a consumed event is <emitter>.<event>, or "+
+				"%q for every event", pattern, catalogueTheRest)
+	}
+	if emitter == catalogueTheRest {
+		return "", fmt.Errorf("%q stands for the rest of a name, so it cannot name the emitter", catalogueTheRest)
+	}
+	// Each name is checked before it becomes a subject: a name carrying a dot would add a token and
+	// silently widen the permission, which is the whole reason safeSubject exists.
+	var out []string
+	for _, part := range strings.Split(event, ".") {
+		switch part {
+		case catalogueTheRest:
+			out = append(out, ">")
+		case "*":
+			out = append(out, "*")
+		default:
+			if !safeSubject.MatchString(part) {
+				return "", fmt.Errorf("%q cannot be part of a subject: it would widen the permission", part)
+			}
+			out = append(out, part)
+		}
+	}
+	if emitter != "*" && !safeSubject.MatchString(emitter) {
+		return "", fmt.Errorf("%q cannot name an emitter: it would widen the permission", emitter)
+	}
+	return "mesh.mod." + emitter + ".event." + strings.Join(out, "."), nil
+}
+
+// catalogueTheRest is the mesh's wildcard for "the rest of a name", duplicated from the catalogue
+// package for the one direction of dependency the build queue's name is duplicated for.
+const catalogueTheRest = "**"
+
+func consumerStream(p Principal) string {
+	switch p.Kind {
+	case KindModule:
+		return "EVENTS"
+	case KindNode:
+		return "NODES"
+	case KindController:
+		return "CONTROL"
+	}
+	return ""
+}
+
+func consumerDurable(p Principal) string {
+	switch p.Kind {
+	case KindModule:
+		return p.Node + "_" + p.Module
+	case KindNode:
+		return p.Node
+	case KindController:
+		return "controller"
+	}
+	return ""
+}
+
+// Server is everything the composed file needs that is not a principal.
+type Server struct {
+	// ClientPort carries TLS itself. There is no plaintext port beside it: a bus reachable
+	// without TLS is one a module can reach without TLS by mistake.
+	ClientPort     int
+	MonitoringPort int
+	TLSCert        string
+	TLSKey         string
+	TLSCA          string
+	// StoreDir is a host directory bind, not a named volume — issue 115 is resolved and converted
+	// four modules away from named volumes; the bus's own data is not the place to bring one back.
+	StoreDir string
+}
+
+// Compose renders the server's whole configuration. The order is stable and the output is
+// deterministic, because the file's digest is what the module's entrypoint watches to decide
+// whether to reload: a composer that reordered a map on each run would signal a reload every time
+// the controller restarted, for a file that had not changed.
+func Compose(s Server, principals []Principal) (string, error) {
+	sorted := append([]Principal(nil), principals...)
+	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Username() < sorted[j].Username() })
+
+	var b strings.Builder
+	b.WriteString("# Composed by the mesh controller. Do not edit: the next composition overwrites it.\n")
+	b.WriteString("# Accounts and permissions are derived from what each module declares and nothing\n")
+	b.WriteString("# else (novox/hq ADR 0043, design 29 §2).\n\n")
+
+	fmt.Fprintf(&b, "port: %d\n", s.ClientPort)
+	fmt.Fprintf(&b, "http: 127.0.0.1:%d\n\n", s.MonitoringPort)
+
+	// **No `verify`, and it said `verify: true` until this configuration was run.** That setting
+	// makes the server demand a *client* certificate, and nothing in the mesh presents one: a host
+	// pins this server's exact certificate and authenticates with the password the mesh minted
+	// (ADR 0004, design 25 §4), and so does a module's runtime. With it on, every connection in the
+	// mesh is refused at the TLS handshake before any password is looked at, and the error —
+	// "client didn't provide a certificate" — reads as a fault in the client.
+	//
+	// TLS is still required: the block is what requires it, and verify only decides whether client
+	// certificates are checked.
+	b.WriteString("tls {\n")
+	fmt.Fprintf(&b, "  cert_file: %q\n", s.TLSCert)
+	fmt.Fprintf(&b, "  key_file: %q\n", s.TLSKey)
+	fmt.Fprintf(&b, "  ca_file: %q\n", s.TLSCA)
+	b.WriteString("}\n\n")
+
+	b.WriteString("jetstream {\n")
+	fmt.Fprintf(&b, "  store_dir: %q\n", s.StoreDir)
+	b.WriteString("}\n\n")
+
+	accounts, err := ComposeAccounts(sorted)
+	if err != nil {
+		return "", err
+	}
+	b.WriteString(accounts)
+	return b.String(), nil
+}
+
+// ComposeAccounts is the accounts block alone — every user, and nothing about the server.
+//
+// **This is the only part of the configuration the mesh writes, and the split is deliberate.** A
+// server's ports, its TLS paths and its store directory are properties of the container the module
+// raises: they live in its image and its mounts, and they change when it does. The controller has no
+// business knowing them, and a controller that did would have to be kept in step with a Dockerfile
+// it never sees. What only the mesh knows is *who may connect*, so that is what it writes, and the
+// module's own configuration includes it.
+//
+// Four things checked against a running server before this shape was committed to: a user in an
+// included file authenticates; an unknown user is refused, so the include is the whole authority
+// rather than an addition to something; a publish outside a user's grant is refused; and rewriting
+// this file alone and signalling a reload makes a new user appear **without dropping the connection
+// the mesh already has** — which is what makes every later account, permission or person change cost
+// nothing (task 1.2's payoff).
+func ComposeAccounts(principals []Principal) (string, error) {
+	sorted := append([]Principal(nil), principals...)
+	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Username() < sorted[j].Username() })
+
+	var b strings.Builder
+	b.WriteString("# The mesh's users, composed by the controller. Do not edit: the next\n")
+	b.WriteString("# composition overwrites it. Permissions are derived from what each module\n")
+	b.WriteString("# declares and nothing else (novox/hq ADR 0043, design 29 §2).\n\n")
+
+	// One account for the mesh: accounts in NATS isolate subject spaces entirely, and the mesh is
+	// one space (design 25 §4). The cost of that — that permissions are the only isolation — is
+	// paid in the scoping of every inbox and every ack subject.
+	// JetStream is enabled per account once accounts exist at all: with only the global block set,
+	// a user in MESH is told "JetStream not enabled for account" the first time it binds a
+	// consumer, which is the first thing every host does (2026-09-28).
+	b.WriteString("accounts {\n  MESH {\n    jetstream: enabled\n    users = [\n")
+	for _, p := range sorted {
+		perms, err := PermissionsFor(p)
+		if err != nil {
+			return "", err
+		}
+		if p.PasswordHash == "" {
+			return "", fmt.Errorf("%s has no password hash: a user without one is a user anybody is", p.Username())
+		}
+		fmt.Fprintf(&b, "      { user: %q, password: %q, permissions: {\n", p.Username(), p.PasswordHash)
+		fmt.Fprintf(&b, "        publish: { allow: [%s] }\n", quoted(perms.Publish))
+		fmt.Fprintf(&b, "        subscribe: { allow: [%s] }\n", quoted(perms.Subscribe))
+		if perms.AllowResponses {
+			b.WriteString("        allow_responses: { max: 1, ttl: \"1m\" }\n")
+		}
+		b.WriteString("      } }\n")
+	}
+	b.WriteString("    ]\n  }\n}\n")
+	return b.String(), nil
+}
+
+func quoted(values []string) string {
+	if len(values) == 0 {
+		return ""
+	}
+	out := make([]string, len(values))
+	for i, v := range values {
+		out[i] = fmt.Sprintf("%q", v)
+	}
+	return strings.Join(out, ", ")
+}
@@ -0,0 +1,49 @@
+package broker
+
+import (
+	"flag"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+var update = flag.Bool("update", false, "rewrite the golden composition")
+
+// The composed file is the mesh's whole authority model, so a change to it should be visible in a
+// review rather than inferred from a diff of Go. The fixture is also the exact text checked
+// against the real server's parser (`nats-server -t`), which is what says this syntax is the
+// server's and not one we invented.
+func TestTheComposedConfigMatchesTheGolden(t *testing.T) {
+	seat := Seat{Name: "telegram-sender", Accepts: []string{"send"}, Emits: []string{"delivered", "failed"}}
+	got, err := Compose(
+		Server{ClientPort: 4222, MonitoringPort: 8222, StoreDir: "/data",
+			TLSCert: "/tls/tls.crt", TLSKey: "/tls/tls.key", TLSCA: "/tls/ca.crt"},
+		[]Principal{
+			{Kind: KindController, PasswordHash: "$2a$11$cccccccccccccccccccccc"},
+			{Kind: KindEnrolment, Node: "one", PasswordHash: "$2a$11$eeeeeeeeeeeeeeeeeeeeee"},
+			{Kind: KindNode, Node: "one", PasswordHash: "$2a$11$nnnnnnnnnnnnnnnnnnnnnn"},
+			{Kind: KindModule, Node: "one", Module: "telegram", Holds: []Seat{seat},
+				Serves: []string{"status"}, PasswordHash: "$2a$11$tttttttttttttttttttttt"},
+			{Kind: KindModule, Node: "two", Module: "shop", Uses: []Seat{seat},
+				Emits: []string{"order.placed"}, PasswordHash: "$2a$11$ssssssssssssssssssssss"},
+			{Kind: KindModule, Node: "two", Module: "audit",
+				Consumes: []string{"shop.order.placed"}, PasswordHash: "$2a$11$aaaaaaaaaaaaaaaaaaaaaa"},
+		})
+	if err != nil {
+		t.Fatal(err)
+	}
+	golden := filepath.Join("testdata", "composed.conf")
+	if *update {
+		if err := os.WriteFile(golden, []byte(got), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		return
+	}
+	want, err := os.ReadFile(golden)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != string(want) {
+		t.Errorf("composition changed; re-run with -update and read the diff:\n%s", got)
+	}
+}
@@ -0,0 +1,361 @@
+package broker
+
+import (
+	"slices"
+	"strings"
+	"testing"
+)
+
+func has(t *testing.T, subjects []string, want string) {
+	t.Helper()
+	for _, s := range subjects {
+		if s == want {
+			return
+		}
+	}
+	t.Fatalf("expected %q among %v", want, subjects)
+}
+
+func hasNot(t *testing.T, subjects []string, unwanted string) {
+	t.Helper()
+	for _, s := range subjects {
+		if s == unwanted {
+			t.Fatalf("did not expect %q among %v", unwanted, subjects)
+		}
+	}
+}
+
+// A module's authority comes from its declaration and nothing else (novox/hq ADR 0043).
+func TestAModulePublishesOnlyWhatItEmits(t *testing.T) {
+	p := Principal{Kind: KindModule, Node: "one", Module: "billing",
+		Emits: []string{"order.placed"}, PasswordHash: "x"}
+	perms, err := PermissionsFor(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	has(t, perms.Publish, "mesh.mod.billing.event.order.placed")
+	hasNot(t, perms.Publish, "mesh.mod.billing.>")
+	hasNot(t, perms.Publish, "mesh.mod.shipping.event.order.placed")
+}
+
+// The gap AMQP left open — an emitter granted the events exchange whole — is closed by per-subject
+// permissions. A module cannot publish under another module's name.
+func TestAModuleCannotPublishUnderAnothersName(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "billing",
+		Emits: []string{"order.placed"}, PasswordHash: "x"})
+	for _, p := range perms.Publish {
+		if strings.HasPrefix(p, "mesh.mod.") && !strings.HasPrefix(p, "mesh.mod.billing.") {
+			t.Fatalf("billing may publish %q, which is not its own namespace", p)
+		}
+	}
+}
+
+// A caller of a seat may publish what the seat accepts, and nothing else of it: not its outbound
+// events, and not a subscription to its inbound queue (design 29 §2).
+func TestUsingASeatIsPublishOnlyAndInboundOnly(t *testing.T) {
+	seat := Seat{Name: "telegram-sender", Accepts: []string{"send"}, Emits: []string{"delivered", "failed"}}
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "shop",
+		Uses: []Seat{seat}, PasswordHash: "x"})
+	has(t, perms.Publish, "mesh.seat.telegram-sender.accept.send")
+	hasNot(t, perms.Publish, "mesh.seat.telegram-sender.event.delivered")
+	hasNot(t, perms.Subscribe, "mesh.seat.telegram-sender.accept.send")
+}
+
+// The holder is the mirror image: it consumes what the seat accepts and publishes what it emits.
+func TestHoldingASeatIsTheMirrorOfUsingIt(t *testing.T) {
+	seat := Seat{Name: "telegram-sender", Accepts: []string{"send"}, Emits: []string{"delivered", "failed"}}
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "telegram",
+		Holds: []Seat{seat}, PasswordHash: "x"})
+	has(t, perms.Subscribe, "mesh.seat.telegram-sender.accept.send")
+	has(t, perms.Publish, "mesh.seat.telegram-sender.event.delivered")
+	hasNot(t, perms.Publish, "mesh.seat.telegram-sender.accept.send")
+}
+
+// Without an ack permission a durable consumer never really consumes: every message it receives is
+// redelivered forever, refused by the permission list it already has (design 25 §4).
+func TestAModuleMayAckItsOwnDeliveriesAndNoOthers(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "billing",
+		Consumes: []string{"shop.order.placed"}, PasswordHash: "x"})
+	has(t, perms.Publish, "$JS.ACK.EVENTS.one_billing.>")
+	hasNot(t, perms.Publish, "$JS.ACK.>")
+	hasNot(t, perms.Publish, "$JS.ACK.EVENTS.one_shop.>")
+}
+
+// With one account, inbox privacy is the permission list or it is nothing.
+func TestAnInboxIsScopedToItsOwner(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "billing", PasswordHash: "x"})
+	has(t, perms.Subscribe, "_INBOX.one.billing.>")
+	hasNot(t, perms.Subscribe, "_INBOX.>")
+	hasNot(t, perms.Subscribe, "_INBOX.one.shop.>")
+}
+
+// A responder answers on the caller's inbox, which it has no permission for. allow_responses is
+// what makes a scoped inbox workable at all — the authority is bounded by having been asked. A
+// module is asked on its own namespace and may answer; a node and a person are never asked.
+func TestOnlyWhatCanBeAskedMayAnswer(t *testing.T) {
+	module, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "audit",
+		Consumes: []string{"shop.order.placed"}, PasswordHash: "x"})
+	if !module.AllowResponses {
+		t.Fatal("a module cannot answer a tool call on its own namespace")
+	}
+	node, _ := PermissionsFor(Principal{Kind: KindNode, Node: "one", PasswordHash: "x"})
+	if node.AllowResponses {
+		t.Fatal("a node was granted the right to answer, and nothing asks a node anything")
+	}
+}
+
+// A module serves every tool under its own name, and no other module's.
+func TestAModuleServesItsOwnNamespaceAndNoOthers(t *testing.T) {
+	p, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "gitea", PasswordHash: "x"})
+	if !slices.Contains(p.Subscribe, "mesh.mod.gitea.tool.>") {
+		t.Fatalf("a module may not serve its own tools: %v", p.Subscribe)
+	}
+	for _, s := range p.Subscribe {
+		if strings.HasPrefix(s, "mesh.mod.") && !strings.HasPrefix(s, "mesh.mod.gitea.") {
+			t.Fatalf("a module may subscribe another's namespace: %s", s)
+		}
+	}
+}
+
+// A host reaches its own node's control traffic and its own declaration, and nothing of any
+// other node's.
+func TestAHostIsConfinedToItsOwnNode(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindNode, Node: "one", PasswordHash: "x"})
+	has(t, perms.Publish, "mesh.control.one.>")
+	has(t, perms.Subscribe, "mesh.node.one.declare")
+	hasNot(t, perms.Subscribe, "mesh.node.two.declare")
+	hasNot(t, perms.Subscribe, "mesh.node.>")
+}
+
+// A leaked enrolment token is useless for anything but enrolling (design 25 §6).
+func TestTheEnrolmentUserCanOnlyEnrol(t *testing.T) {
+	perms, err := PermissionsFor(Principal{Kind: KindEnrolment, Node: "anchor", PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(perms.Publish) != 1 || perms.Publish[0] != "mesh.control.enrol" {
+		t.Fatalf("enrolment may publish %v", perms.Publish)
+	}
+	// Its own inbox and nothing else. **Nothing else** is the point: no declaration, no event, and
+	// no other machine's answer — and the inbox itself is needed, because a node that cannot
+	// subscribe one waits out its timeout against a mesh that answered.
+	if len(perms.Subscribe) != 1 || perms.Subscribe[0] != "_INBOX.enrol.anchor.>" {
+		t.Fatalf("enrolment may subscribe %v, which is not its own inbox alone", perms.Subscribe)
+	}
+}
+
+// An enrolment user that names no node is refused: its inbox would be an empty subject token, and
+// one that every nameless enrolment user shared — which is one machine reading the credentials
+// sealed to another.
+func TestAnEnrolmentUserWithoutANodeIsRefused(t *testing.T) {
+	if _, err := PermissionsFor(Principal{Kind: KindEnrolment, PasswordHash: "x"}); err == nil {
+		t.Fatal("an enrolment user with no node was composed, so its inbox is shared")
+	}
+}
+
+// A name that would widen a permission is refused rather than quietly stretching one.
+func TestANameThatWouldWidenAPermissionIsRefused(t *testing.T) {
+	for _, bad := range []string{"bill.ing", "billing.>", "*", "bil>ling"} {
+		if _, err := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: bad, PasswordHash: "x"}); err == nil {
+			t.Fatalf("%q was accepted as part of a subject", bad)
+		}
+	}
+}
+
+// The entrypoint reloads on the file's digest changing, so an unchanged mesh must compose an
+// identical file — otherwise every controller restart signals a reload of the whole bus.
+func TestComposingTwiceGivesTheSameBytes(t *testing.T) {
+	s := Server{ClientPort: 4222, MonitoringPort: 8222, StoreDir: "/data",
+		TLSCert: "/tls/tls.crt", TLSKey: "/tls/tls.key", TLSCA: "/tls/ca.crt"}
+	ps := []Principal{
+		{Kind: KindModule, Node: "two", Module: "shop", Emits: []string{"order.placed"}, PasswordHash: "b"},
+		{Kind: KindController, PasswordHash: "c"},
+		{Kind: KindModule, Node: "one", Module: "billing", Consumes: []string{"shop.order.placed"}, PasswordHash: "a"},
+	}
+	first, err := Compose(s, ps)
+	if err != nil {
+		t.Fatal(err)
+	}
+	shuffled := []Principal{ps[2], ps[0], ps[1]}
+	second, err := Compose(s, shuffled)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if first != second {
+		t.Fatal("composition is order-dependent; every controller restart would reload the bus")
+	}
+}
+
+// A user without a password is a user anybody is.
+func TestAUserWithoutAPasswordIsRefused(t *testing.T) {
+	_, err := Compose(Server{ClientPort: 4222}, []Principal{{Kind: KindController}})
+	if err == nil {
+		t.Fatal("composed a user with no password hash")
+	}
+}
+
+// A person reaches the mesh's tools from a workstation (design 25 §7). Their authority is a list
+// of tools and nothing else.
+func TestAPersonMayAskOnlyTheToolsTheyWereGiven(t *testing.T) {
+	perms, err := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"shop.price", "telegram.status"}, PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	has(t, perms.Publish, "mesh.mod.shop.tool.price")
+	has(t, perms.Publish, "mesh.mod.telegram.tool.status")
+	hasNot(t, perms.Publish, "mesh.mod.shop.tool.refund")
+	hasNot(t, perms.Publish, "mesh.mod.*.tool.>")
+}
+
+// An administrator gets every tool, which is a different grant and looks like one.
+func TestAnAdministratorMayAskAnyTool(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"*"}, PasswordHash: "x"})
+	has(t, perms.Publish, "mesh.mod.*.tool.>")
+}
+
+// **Nothing but tools.** A person who could publish an event would be able to claim a module
+// said something; one who could publish control traffic would be a second controller.
+func TestAPersonReachesNothingButTools(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"*"}, PasswordHash: "x"})
+	for _, p := range perms.Publish {
+		if !strings.Contains(p, ".tool.") {
+			t.Errorf("a person may publish %q, which is not a tool call", p)
+		}
+	}
+	for _, s := range perms.Subscribe {
+		if !strings.HasPrefix(s, "_INBOX.person.") {
+			t.Errorf("a person may subscribe %q; only their own inbox should be reachable", s)
+		}
+	}
+}
+
+// A person has no durable consumer, because nothing is delivered to a person — so no ack
+// subject, and an ack permission would be authority over something that does not exist.
+func TestAPersonHasNoAckSubject(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"*"}, PasswordHash: "x"})
+	for _, p := range perms.Publish {
+		if strings.HasPrefix(p, "$JS.ACK") {
+			t.Errorf("a person was granted %q, and has no consumer to acknowledge", p)
+		}
+	}
+}
+
+// A person asks and is answered; they never answer. allow_responses would let a person reply to
+// a request — which, on a bus where anyone may serve a tool, is somebody impersonating a module.
+func TestAPersonMayNotAnswer(t *testing.T) {
+	perms, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"*"}, PasswordHash: "x"})
+	if perms.AllowResponses {
+		t.Fatal("a person may answer a request, which is impersonating a module")
+	}
+}
+
+// Two people do not share an inbox, or one would read the other's answers.
+func TestTwoPeopleDoNotShareAnInbox(t *testing.T) {
+	a, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "jo", Invokes: []string{"*"}, PasswordHash: "x"})
+	b, _ := PermissionsFor(Principal{Kind: KindPerson, Module: "sam", Invokes: []string{"*"}, PasswordHash: "x"})
+	if a.Subscribe[0] == b.Subscribe[0] {
+		t.Fatalf("both read %s", a.Subscribe[0])
+	}
+}
+
+// A malformed grant is refused rather than widened into something that happens to parse.
+func TestAToolGrantThatNamesNoToolIsRefused(t *testing.T) {
+	if _, err := PermissionsFor(Principal{Kind: KindPerson, Module: "jo",
+		Invokes: []string{"shop"}, PasswordHash: "x"}); err == nil {
+		t.Fatal("a grant naming a module but no tool was accepted")
+	}
+}
+
+// The controller can answer an enrolment, and reach no other inbox.
+//
+// **`allow_responses` does not cover this and that is the trap.** It permits one reply to the reply
+// subject of a message the user received — and a message a JetStream consumer delivers has had that
+// field claimed for the consumer's own ack address, so the address the controller actually answers is
+// the one the request carried in its payload, which the server does not recognise as a reply subject
+// at all.
+//
+// Found against a real server, after a live test on an *unpermissioned* one had passed: every
+// enrolment on the mesh would have timed out while the controller logged success.
+func TestTheControllerCanAnswerAnEnrolmentAndReachNoOtherInbox(t *testing.T) {
+	ctl, err := PermissionsFor(Principal{Kind: KindController, PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	enrolling, err := PermissionsFor(Principal{Kind: KindEnrolment, Node: "anchor", PasswordHash: "x"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Whatever the enrolling node waits on, the controller must be able to publish to.
+	if len(enrolling.Subscribe) != 1 {
+		t.Fatalf("an enrolling node subscribes %v, and this test knows only how to check one",
+			enrolling.Subscribe)
+	}
+	waitsOn := enrolling.Subscribe[0]
+	if !covers(ctl.Publish, waitsOn) {
+		t.Fatalf("the controller may publish %v, none of which reaches %s — so every enrolment on "+
+			"the mesh times out while the controller logs success", ctl.Publish, waitsOn)
+	}
+
+	// And nothing wider. A node's own inbox and a module's are not the controller's to write into:
+	// that is the blanket grant design 25 §4 refuses.
+	for _, other := range []string{"_INBOX.node.anchor.x", "_INBOX.one.shop.x", "_INBOX.person.ada.x"} {
+		if covers(ctl.Publish, other) {
+			t.Errorf("the controller can publish to %s, which is an inbox privacy the permission "+
+				"list is the only thing protecting", other)
+		}
+	}
+}
+
+// covers says whether any granted subject pattern admits one concrete subject, with NATS's own
+// wildcard meanings: `*` is one token, `>` is the rest.
+func covers(granted []string, subject string) bool {
+	want := strings.Split(subject, ".")
+	for _, pattern := range granted {
+		if admits(strings.Split(pattern, "."), want) {
+			return true
+		}
+	}
+	return false
+}
+
+func admits(pattern, subject []string) bool {
+	for i, token := range pattern {
+		if token == ">" {
+			return i < len(subject)
+		}
+		if i >= len(subject) {
+			return false
+		}
+		if token != "*" && token != subject[i] {
+			return false
+		}
+	}
+	return len(pattern) == len(subject)
+}
+
+// A module pulls its own consumer — asks about it, asks it for messages — and no other module's.
+func TestAModulePullsItsOwnConsumerAndNoOthers(t *testing.T) {
+	p, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "audit",
+		Consumes: []string{"shop.order.placed"}, PasswordHash: "x"})
+	for _, want := range []string{"$JS.API.CONSUMER.INFO.EVENTS.one_audit", "$JS.API.CONSUMER.MSG.NEXT.EVENTS.one_audit"} {
+		if !slices.Contains(p.Publish, want) {
+			t.Errorf("a module cannot bind its own consumer: %v lacks %s", p.Publish, want)
+		}
+	}
+	for _, s := range p.Publish {
+		if strings.Contains(s, "CONSUMER.") && !strings.HasSuffix(s, ".one_audit") {
+			t.Errorf("a module may reach another consumer: %s", s)
+		}
+	}
+	for _, s := range p.Subscribe {
+		if strings.HasPrefix(s, "_DELIVER.") {
+			t.Errorf("a module is granted a push delivery it never binds: %s", s)
+		}
+	}
+}
@@ -0,0 +1,83 @@
+package broker
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/novox/mesh-controller/internal/envfile"
+)
+
+// Whether this mesh's own traffic is on the bus being built.
+//
+// **One switch, read in one place** (novox/hq ADR 0116 step 5). Every seam the bus change went
+// behind ships both implementations, and until the rollout every one of them chooses the bus the
+// mesh runs on today. This is what the rollout flips, and it is deliberately a single fact rather
+// than a fact per component: a controller whose outbound is on one bus and whose inbound is on the
+// other is a mesh that hears nothing, and no test of either half would catch it.
+
+// NATSVar is where the controller finds the bus being built. Unset is the ordinary case and means
+// the mesh runs on the bus it has always run on.
+const NATSVar = "MESH_BUS_NATS"
+
+// OnNATS is the address of the bus being built, and whether the mesh is on it.
+//
+// Read from the node's own settings rather than baked in, for the reason the broker's address is
+// (novox/hq 04-ISSUES/102): an address recorded once does not follow a node's ports.
+func OnNATS() (address string, on bool, err error) {
+	address, err = envfile.Placed(NATSVar)
+	if err != nil {
+		return "", false, err
+	}
+	address = strings.TrimSpace(address)
+	if address == "" {
+		return "", false, nil
+	}
+	return address, true, nil
+}
+
+// CredentialIn reads the user and password out of a bus address, and the address without them.
+//
+// The controller's own credential arrives in its address, the way the old bus's does. Split out so the
+// controller can record a hash of what it is actually using: its user is created by the installer at a
+// bootstrap password, before the controller exists to mint one, and a composition that left itself out
+// would produce a bus the writer cannot connect to.
+func CredentialIn(address string) (user, password, bare string) {
+	at := strings.LastIndex(address, "@")
+	if at < 0 {
+		return "", "", address
+	}
+	scheme := ""
+	rest := address[:at]
+	if i := strings.Index(rest, "://"); i >= 0 {
+		scheme, rest = rest[:i+3], rest[i+3:]
+	}
+	user, password, _ = strings.Cut(rest, ":")
+	return user, password, scheme + address[at+1:]
+}
+
+// BareAddress is a bus address with any credential stripped, for something that only needs to know
+// whether a server is answering there.
+func BareAddress(address string) string {
+	_, _, bare := CredentialIn(address)
+	if bare == "" {
+		return address
+	}
+	if strings.Contains(bare, "://") {
+		return bare
+	}
+	return "nats://" + bare
+}
+
+// BusAddress is where the mesh's bus is, with this process's credential, and refuses to be empty:
+// there is one bus, and a control plane without it can hold records and answer nothing (novox/hq
+// ADR 0131, design 28 task 5.5).
+func BusAddress() (string, error) {
+	address, _, err := OnNATS()
+	if err != nil {
+		return "", err
+	}
+	if address == "" {
+		return "", fmt.Errorf("this control plane has no %s, so it cannot reach the mesh's bus", NATSVar)
+	}
+	return address, nil
+}
@@ -0,0 +1,28 @@
+package broker
+
+import (
+	"testing"
+)
+
+// Which bus the mesh is on is one fact, and being told about both is refused.
+//
+
+// The controller's own credential arrives in its address, and has to be readable out of it — its user
+// is created by the installer at a bootstrap password, before the controller exists to mint one.
+func TestACredentialIsReadOutOfABusAddress(t *testing.T) {
+	for _, c := range []struct{ in, user, password, bare string }{
+		{"nats://controller:secret@127.0.0.1:4222", "controller", "secret", "nats://127.0.0.1:4222"},
+		{"controller:secret@127.0.0.1:4222", "controller", "secret", "127.0.0.1:4222"},
+		{"nats://127.0.0.1:4222", "", "", "nats://127.0.0.1:4222"},
+		{"127.0.0.1:4222", "", "", "127.0.0.1:4222"},
+		// A password containing an at-sign: split on the last one, or the address becomes part of the
+		// credential and the connection goes somewhere nobody named.
+		{"nats://controller:a@b@127.0.0.1:4222", "controller", "a@b", "nats://127.0.0.1:4222"},
+	} {
+		user, password, bare := CredentialIn(c.in)
+		if user != c.user || password != c.password || bare != c.bare {
+			t.Errorf("%q read as %q/%q at %q; wanted %q/%q at %q",
+				c.in, user, password, bare, c.user, c.password, c.bare)
+		}
+	}
+}
@@ -0,0 +1,73 @@
+package broker
+
+import "fmt"
+
+// Bringing the bus's own objects into being, in the one order that works.
+//
+// **Asserted on every start rather than created once at genesis.** A stream somebody deleted, a mesh
+// raised from a restored backup, or a bus whose data directory was replaced all have records and no
+// objects — and a node whose consumer is missing hears nothing while everything else about it looks
+// correct. Idempotence is the whole requirement, and the parts are already idempotent; this is the
+// order they have to be asked in.
+
+// Raiser is everything asserting the bus's objects needs of a connection to it.
+type Raiser interface {
+	Asserter
+	Ensurer
+}
+
+// Raise asserts the mesh's streams, the controller's own consumers, and one consumer per node.
+//
+// **The order is not a preference.** A consumer on a stream that does not exist is refused, and the
+// refusal names the stream rather than the order — so somebody reading it goes looking for a deleted
+// stream instead of a reversed pair of lines. Nodes last, because the one a node reads lives on a
+// stream the mesh's own set defines.
+func Raise(r Raiser, nodes []string) error {
+	if err := AssertMeshStreams(r); err != nil {
+		return err
+	}
+	if err := AssertMeshConsumers(r); err != nil {
+		return err
+	}
+	if err := AssertNodeConsumers(r, nodes); err != nil {
+		return err
+	}
+	return nil
+}
+
+// RaiseSeats asserts one work queue per declared seat, and the worker of whoever holds it.
+//
+// Separate from Raise because it is answered by a different question: the mesh's own objects exist
+// because the mesh does, and a seat's exist because a module declaring one was registered. Kept
+// beside it so the order is visible — a holder's worker needs the seat's stream, and a seat's stream
+// needs nothing.
+func RaiseSeats(r Raiser, seats []DeclaredSeat, holders map[string]Holder) error {
+	for _, s := range SeatStreams(seats) {
+		if err := r.EnsureStream(s); err != nil {
+			return fmt.Errorf("asserting the work queue for %s: %w", s.Name, err)
+		}
+	}
+	for _, s := range seats {
+		h, held := holders[s.Name]
+		if !held {
+			// **The stream exists and the consumer does not, on purpose.** Work queues until a
+			// holder appears, so installing the module a week after something started sending to it
+			// flushes the backlog instead of having lost it.
+			continue
+		}
+		c, needed := HolderConsumerFor(h.Node, h.Module, s)
+		if !needed {
+			continue
+		}
+		if err := r.EnsureConsumer(c); err != nil {
+			return fmt.Errorf("asserting how %s on %s works %s: %w", h.Module, h.Node, s.Name, err)
+		}
+	}
+	return nil
+}
+
+// Holder is which module on which machine holds a seat.
+type Holder struct {
+	Node   string
+	Module string
+}
@@ -0,0 +1,196 @@
+package broker
+
+import (
+	"os"
+	"testing"
+
+	"github.com/nats-io/nats.go"
+)
+
+// Raising the bus's objects against a real server.
+//
+// The pure tests above say what is asked for and in what order. Only a server can say whether it
+// accepts them — and two of these are claims about the server's own behaviour that nothing else
+// could answer: that asserting twice changes nothing, and that a consumer really is bound to the one
+// subject its node is allowed to read.
+//
+//	docker run -d --rm --name t -p 14227:4222 nats:2.10-alpine -js
+//	MESH_TEST_NATS=nats://127.0.0.1:14227 go test ./internal/broker/ -run TestRaising
+
+func aLiveBus(t *testing.T) *JetStream {
+	t.Helper()
+	url := os.Getenv("MESH_TEST_NATS")
+	if url == "" {
+		t.Skip("MESH_TEST_NATS unset")
+	}
+	js, err := Dial(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(js.Close)
+	// **Nothing is deleted here, deliberately.** These objects are the mesh's own and every live
+	// test in every package shares one server: a test that deleted a stream to get a clean slate
+	// took it out from under whatever was running beside it, and the failure landed in the other
+	// test as "stream not found" — which reads as a bug in the code under test. Raise is idempotent
+	// by requirement, so asserting against whatever is already there is both safe and the realistic
+	// case.
+	return js
+}
+
+// Every object the mesh's own traffic needs, accepted by a real server, and asserting again changes
+// nothing — which is the whole requirement, because this runs on every start.
+func TestRaisingTheBusIsAcceptedAndIdempotent(t *testing.T) {
+	js := aLiveBus(t)
+
+	if err := Raise(js, []string{"anchor", "laptop"}); err != nil {
+		t.Fatalf("a real server refused the mesh's own objects: %v", err)
+	}
+	// Twice, with nothing in between. A start that failed the second time is a controller that
+	// cannot restart.
+	if err := Raise(js, []string{"anchor", "laptop"}); err != nil {
+		t.Fatalf("asserting the bus's objects a second time failed, so a restart would: %v", err)
+	}
+	// And again with a machine that was not there before, which is what enrolling one is.
+	if err := Raise(js, []string{"anchor", "laptop", "workstation"}); err != nil {
+		t.Fatalf("a machine joining an already-raised bus was refused: %v", err)
+	}
+
+	for _, s := range MeshStreams() {
+		if _, err := js.Context().StreamInfo(s.Name); err != nil {
+			t.Errorf("stream %s is not there: %v", s.Name, err)
+		}
+	}
+	for _, c := range MeshConsumers() {
+		if _, err := js.Context().ConsumerInfo(c.Stream, c.Name); err != nil {
+			t.Errorf("the controller's consumer on %s is not there: %v", c.Stream, err)
+		}
+	}
+	for _, node := range []string{"anchor", "laptop", "workstation"} {
+		info, err := js.Context().ConsumerInfo("NODES", node)
+		if err != nil {
+			t.Errorf("%s has no way to hear its declaration: %v", node, err)
+			continue
+		}
+		// **Its own subject and no other node's.** A consumer filtered on anything wider is a node
+		// reading another machine's declaration, and its own ack grant would not cover it either.
+		if info.Config.FilterSubject != "mesh.node."+node+".declare" {
+			t.Errorf("%s's consumer reads %q", node, info.Config.FilterSubject)
+		}
+		if info.Config.AckPolicy != nats.AckExplicitPolicy {
+			t.Errorf("%s's consumer acknowledges on delivery, so a declaration it died applying is "+
+				"never sent again", node)
+		}
+	}
+}
+
+// The store window needs unlimited redelivery on CONTROL: the bound belongs to the controller, and a
+// server that dead-lettered first would discard the push the stream exists to protect.
+func TestTheControlConsumerDoesNotDeadLetterBeforeTheControllerGivesUp(t *testing.T) {
+	js := aLiveBus(t)
+	if err := Raise(js, nil); err != nil {
+		t.Fatal(err)
+	}
+	info, err := js.Context().ConsumerInfo("CONTROL", ControllerName)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if info.Config.MaxDeliver > 0 {
+		t.Fatalf("max-deliver is %d: a push held through a store restart would be dead-lettered "+
+			"before the controller finished deciding about it", info.Config.MaxDeliver)
+	}
+}
+
+// A role's work queue exists before anybody holds it, against a real server.
+//
+// **The queue before the holder is the point** (novox/hq ADR 0121): work queues until somebody arrives
+// to do it, so assigning a build machine a week after something started asking for builds flushes the
+// backlog instead of having lost it. A stream created at assignment would make "the holder is not here
+// yet" mean "your requests are gone".
+func TestRaisingAMeshRolesWorkQueue(t *testing.T) {
+	js := aLiveBus(t)
+	seats := []DeclaredSeat{{Name: "mesh-build-machine", Accepts: []string{"build"},
+		Emits: []string{"built"}}}
+	t.Cleanup(func() { _ = js.Context().DeleteStream("SEAT_MESH_BUILD_MACHINE") })
+
+	if err := RaiseSeats(js, seats, nil); err != nil {
+		t.Fatalf("a real server refused a role's work queue: %v", err)
+	}
+	info, err := js.Context().StreamInfo("SEAT_MESH_BUILD_MACHINE")
+	if err != nil {
+		t.Fatalf("the role has no work queue: %v", err)
+	}
+	if info.Config.Retention != nats.WorkQueuePolicy {
+		t.Errorf("the queue retains as %v: work a holder took must leave it, or the next holder does "+
+			"it again", info.Config.Retention)
+	}
+	if len(info.Config.Subjects) != 1 || info.Config.Subjects[0] != "mesh.seat.mesh-build-machine.accept.>" {
+		t.Errorf("it carries %v rather than the role's own inbound subjects", info.Config.Subjects)
+	}
+	// Nobody holds it, so there is no worker — and asserting again changes nothing, because this runs
+	// on every start.
+	if err := RaiseSeats(js, seats, nil); err != nil {
+		t.Fatalf("asserting a role's queue a second time failed, so a restart would: %v", err)
+	}
+
+	// And once somebody holds it, the worker appears on that same queue.
+	if err := RaiseSeats(js, seats, map[string]Holder{
+		"mesh-build-machine": {Node: "anchor", Module: "builder"},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.Context().ConsumerInfo("SEAT_MESH_BUILD_MACHINE",
+		"SEAT_MESH_BUILD_MACHINE_worker"); err != nil {
+		t.Fatalf("the holder got no worker on the role's queue: %v", err)
+	}
+}
+
+// **A consumer created after the fact still sees what came before it**, which is why the mesh needs no
+// catch-up at all on this bus (novox/hq 04-ISSUES/050).
+//
+// On the bus the mesh runs on today a queue receives only what is published after it is bound, so
+// everything built before the catalogue existed was announced to nobody — and on a fresh mesh that is
+// always the foundation, because those are the things the catalogue needed in order to exist. A whole
+// mechanism was built for it: the catalogue asks, the controller re-publishes.
+//
+// A stream is a log and a consumer is a position in it. A consumer created later starts at the
+// beginning by default, so the builds are simply there. Asked of a real server rather than assumed,
+// because the whole decision about whether to keep that mechanism rests on it.
+func TestAConsumerCreatedAfterwardsStillSeesWhatCameBefore(t *testing.T) {
+	js := aLiveBus(t)
+	if err := AssertMeshStreams(js); err != nil {
+		t.Fatal(err)
+	}
+	if err := js.Context().PurgeStream("EVENTS"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Genesis: things are built before anything is listening.
+	built := []string{"base", "store", "mesh-catalog"}
+	for _, m := range built {
+		if _, err := js.Context().Publish("mesh.seat.mesh-build-machine.event.built",
+			[]byte(`{"module":"`+m+`"}`)); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Now the catalogue is installed and the controller creates its consumer.
+	c, ok := ConsumerFor(Principal{Kind: KindModule, Node: "one", Module: "mesh-catalog",
+		Watches: []Seat{{Name: "mesh-build-machine", Emits: []string{"built"}}}, PasswordHash: "x"})
+	if !ok {
+		t.Fatal("a module that watches a role got no consumer")
+	}
+	t.Cleanup(func() { _ = js.Context().DeleteConsumer(c.Stream, c.Name) })
+	if err := js.EnsureConsumer(c); err != nil {
+		t.Fatal(err)
+	}
+
+	info, err := js.Context().ConsumerInfo(c.Stream, c.Name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if info.NumPending != uint64(len(built)) {
+		t.Fatalf("a consumer created after %d builds has %d waiting for it — if this is 0 the mesh "+
+			"does need a catch-up after all, and the reasoning for deleting it is wrong",
+			len(built), info.NumPending)
+	}
+}
@@ -0,0 +1,139 @@
+package broker
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Whether a mesh could move its bus, and what is missing if not.
+//
+// **Asked before anything moves, and answerable from records alone.** The rollout moves every node at
+// once (novox/hq ADR 0116 step 5), so there is no partial state to inspect afterwards and no half to
+// roll back: either the mesh was ready or it was not. That makes a readiness question the most
+// valuable thing here — it costs nothing, it can be asked of a running mesh any number of times, and
+// every answer is a thing somebody can go and fix.
+//
+// Deliberately pure. It is handed what the mesh knows and returns sentences; nothing here connects to
+// anything, so it can be asked on a workstation about a mesh it has never reached.
+
+// Readiness is what the mesh knows about its own ability to move.
+type Readiness struct {
+	// TheBus is the address the mesh's own traffic would move to, empty when nothing names one.
+	TheBus string
+	// ServerStanding is whether a bus is reachable at that address, as somebody checked.
+	ServerStanding bool
+	// Holder is the node running the module that holds the bus seat, empty when nothing does.
+	Holder string
+	// AccountsComposed is whether that node has been sent the composed user list.
+	AccountsComposed bool
+	// Nodes is every machine the mesh knows.
+	Nodes []string
+	// Credentialled is which of them has a credential for the new bus.
+	Credentialled map[string]bool
+	// Modules is every assigned module, as `<node>/<module>`.
+	Modules []string
+	// ModuleCredentialled is which of those has one.
+	ModuleCredentialled map[string]bool
+}
+
+// NotReady is every reason this mesh cannot move its bus yet, in the order somebody would fix them.
+//
+// Empty means ready. **Each entry names one thing and what to do about it**, because a readiness check
+// that says "not ready" is a check nobody can act on — and this is read at the point where the next
+// step is irreversible.
+func NotReady(r Readiness) []string {
+	var why []string
+
+	if strings.TrimSpace(r.TheBus) == "" {
+		why = append(why, "nothing names the bus to move to: set "+NATSVar+" on the control node "+
+			"to the address the new server answers on")
+	}
+	if !r.ServerStanding {
+		why = append(why, "no bus is answering at that address. Step 2 of the change raises it beside "+
+			"the one the mesh is on, carrying nothing — assign the module that holds "+
+			"mesh-broker and push the machine that runs it")
+	}
+	if r.Holder == "" {
+		why = append(why, "no machine holds mesh-broker, so nothing would compose the bus's user "+
+			"list. Assign the module that claims it")
+	} else if !r.AccountsComposed {
+		why = append(why, fmt.Sprintf(
+			"%s holds mesh-broker and has not been sent the composed user list, so the bus would "+
+				"refuse every connection. `push %s`", r.Holder, r.Holder))
+	}
+
+	// A node with no credential cannot come back after the move, and a node that cannot come back is
+	// a machine the mesh has lost until somebody goes to it.
+	var missing []string
+	for _, n := range r.Nodes {
+		if !r.Credentialled[n] {
+			missing = append(missing, n)
+		}
+	}
+	sort.Strings(missing)
+	if len(missing) > 0 {
+		why = append(why, fmt.Sprintf(
+			"%d machine(s) have no credential for the new bus and would not come back: %s. Each needs "+
+				"one minted before the move, not after — after, there is no bus to ask over",
+			len(missing), strings.Join(missing, ", ")))
+	}
+
+	// A module without one keeps running and stops being reachable, which is a smaller fault and still
+	// one somebody should choose rather than discover.
+	var quiet []string
+	for _, m := range r.Modules {
+		if !r.ModuleCredentialled[m] {
+			quiet = append(quiet, m)
+		}
+	}
+	sort.Strings(quiet)
+	if len(quiet) > 0 {
+		why = append(why, fmt.Sprintf(
+			"%d module(s) have no credential for the new bus: %s. Each keeps serving and stops "+
+				"answering tools and hearing events until it is issued one",
+			len(quiet), strings.Join(quiet, ", ")))
+	}
+
+	return why
+}
+
+// WhatMoves is what the rollout would do, in order, for somebody reading before they commit.
+//
+// **Written out rather than summarised.** This is the one step with nothing to inspect afterwards, so
+// the last useful moment to disagree with it is while reading this.
+func WhatMoves(r Readiness) []string {
+	out := []string{
+		fmt.Sprintf("compose the bus's user list and send it to %s", holderOr(r.Holder)),
+		fmt.Sprintf("move this control plane to %s, and confirm it is heard", busOr(r.TheBus)),
+	}
+	nodes := append([]string(nil), r.Nodes...)
+	sort.Strings(nodes)
+	for _, n := range nodes {
+		out = append(out, fmt.Sprintf("move %s, and confirm it reports", n))
+	}
+	if len(r.Modules) > 0 {
+		out = append(out, fmt.Sprintf("move %d module runtime(s), and confirm each answers",
+			len(r.Modules)))
+	}
+	// **The old broker goes, and it goes last** (novox/hq ADR 0131). AMQP is not a provision, so once
+	// every machine reports on the new bus nothing of the mesh is left speaking to it, and its module
+	// is unassigned. Said as a step so nobody reads the move as leaving a second bus behind.
+	out = append(out, "then unassign the old broker's module: AMQP is not a provision (ADR 0131), and "+
+		"once every machine reports on the new bus nothing of the mesh speaks to it")
+	return out
+}
+
+func holderOr(node string) string {
+	if node == "" {
+		return "whichever machine holds mesh-broker"
+	}
+	return node
+}
+
+func busOr(address string) string {
+	if address == "" {
+		return "the new bus"
+	}
+	return address
+}
@@ -0,0 +1,98 @@
+package broker
+
+import (
+	"strings"
+	"testing"
+)
+
+// Whether a mesh could move its bus.
+//
+// Every case here is a way of moving that leaves something behind, and the one that matters most is a
+// machine with no credential: after the move there is no bus to ask it over, so it is lost until
+// somebody walks to it.
+
+func aMeshReadyToMove() Readiness {
+	return Readiness{
+		TheBus: "nats://127.0.0.1:5671", ServerStanding: true,
+		Holder: "anchor", AccountsComposed: true,
+		Nodes:               []string{"anchor", "laptop"},
+		Credentialled:       map[string]bool{"anchor": true, "laptop": true},
+		Modules:             []string{"anchor/gitea"},
+		ModuleCredentialled: map[string]bool{"anchor/gitea": true},
+	}
+}
+
+func TestAMeshWithEverythingInPlaceIsReady(t *testing.T) {
+	if why := NotReady(aMeshReadyToMove()); len(why) != 0 {
+		t.Fatalf("a mesh with everything in place was refused: %v", why)
+	}
+}
+
+// **A machine with no credential is the one that must stop this.** It keeps running and cannot come
+// back, and there is no bus left to tell it anything over — so the remedy has to happen before, and
+// the message says so.
+func TestAMachineWithNoCredentialStopsTheMove(t *testing.T) {
+	r := aMeshReadyToMove()
+	r.Credentialled = map[string]bool{"anchor": true}
+
+	why := NotReady(r)
+	if len(why) == 0 {
+		t.Fatal("a machine that could not come back did not stop the move")
+	}
+	said := strings.Join(why, "\n")
+	if !strings.Contains(said, "laptop") {
+		t.Errorf("the refusal does not name the machine: %s", said)
+	}
+	if !strings.Contains(said, "before the move") {
+		t.Errorf("the refusal does not say the remedy comes first: %s", said)
+	}
+}
+
+// A bus nobody has raised, a seat nobody holds, and a user list nobody has been sent: each stops it,
+// and each names its own next step, because "not ready" that cannot be acted on is not an answer.
+func TestEachThingMissingNamesItsOwnRemedy(t *testing.T) {
+	for _, c := range []struct {
+		what   string
+		break_ func(*Readiness)
+		says   string
+	}{
+		{"no address", func(r *Readiness) { r.TheBus = "" }, NATSVar},
+		{"no server", func(r *Readiness) { r.ServerStanding = false }, "carrying nothing"},
+		{"no holder", func(r *Readiness) { r.Holder = "" }, "mesh-broker"},
+		{"no user list", func(r *Readiness) { r.AccountsComposed = false }, "push anchor"},
+		{"a module with none", func(r *Readiness) {
+			r.ModuleCredentialled = map[string]bool{}
+		}, "anchor/gitea"},
+	} {
+		r := aMeshReadyToMove()
+		c.break_(&r)
+		why := NotReady(r)
+		if len(why) == 0 {
+			t.Errorf("%s did not stop the move", c.what)
+			continue
+		}
+		if !strings.Contains(strings.Join(why, "\n"), c.says) {
+			t.Errorf("%s: the refusal does not mention %q: %v", c.what, c.says, why)
+		}
+	}
+}
+
+// What the move would do is written out rather than summarised, because this is the one step with
+// nothing to inspect afterwards — so reading it is the last chance to disagree.
+func TestWhatMovesNamesEveryMachineAndEndsWithTheOldBrokerGoing(t *testing.T) {
+	r := aMeshReadyToMove()
+	steps := strings.Join(WhatMoves(r), "\n")
+
+	for _, want := range []string{"anchor", "laptop", "user list", "module runtime"} {
+		if !strings.Contains(steps, want) {
+			t.Errorf("the plan does not mention %q:\n%s", want, steps)
+		}
+	}
+	// Said explicitly, and last: AMQP is not a provision (novox/hq ADR 0131), so the move ends with
+	// the old broker's module unassigned, not left behind as a second bus. An earlier version of this
+	// test pinned the opposite, under a record 0131 superseded.
+	lines := WhatMoves(r)
+	if last := lines[len(lines)-1]; !strings.Contains(last, "unassign the old broker") {
+		t.Errorf("the plan does not end with the old broker going:\n%s", steps)
+	}
+}
@@ -0,0 +1,241 @@
+package broker
+
+import (
+	"fmt"
+	"sort"
+)
+
+// The mesh's own streams.
+//
+// **These four and no more** (novox/hq ADR 0116 task 1.4, as revised by ADR 0118). An earlier
+// reading had the controller create *every* stream at genesis, from a fixed set. That is only the
+// mesh's own half: a seat's streams are created when the module declaring it is registered, and a
+// module's durable consumers when it is assigned — neither of which has happened at genesis. What
+// is here is the foundation, which exists before any module does.
+//
+// The controller is the only writer of stream definitions (design 25 §3). A module declares
+// nothing about them and cannot reach the JetStream API to make one.
+
+// Retention is how a stream decides what to keep, which is the whole of what distinguishes the
+// mesh's four relationships on the wire (design 29 §4).
+type Retention string
+
+const (
+	// RetentionWorkQueue: a message is removed once a consumer acknowledges it. Exactly one
+	// worker does the work, and a worker that dies has its message redelivered.
+	RetentionWorkQueue Retention = "workqueue"
+	// RetentionLastPerSubject: only the newest message on each subject survives. This is the
+	// state shape — a node that was away gets exactly the current declaration and nothing older.
+	RetentionLastPerSubject Retention = "last_per_subject"
+	// RetentionLimits: kept until it ages or the stream fills. Events, where a subscriber that
+	// was down catches up and nobody is obliged to act.
+	RetentionLimits Retention = "limits"
+)
+
+// A Stream is one of the mesh's own, as the controller asserts it.
+type Stream struct {
+	Name      string
+	Subjects  []string
+	Retention Retention
+	// MaxAge in seconds, zero for unbounded. Per stream — JetStream has no per-subject age,
+	// which is why differing retention between modules would mean a stream each.
+	MaxAge int
+	// MaxMsgsPerSubject caps each subject independently, so one noisy emitter cannot push
+	// another's events out of a shared stream. Verified: with a cap of 3, ten messages on one
+	// subject and one on another leave four in the stream, not three.
+	MaxMsgsPerSubject int
+	// Why is carried into the assertion so an operator reading the server's own state finds the
+	// reason there, rather than only in a repository they may not have.
+	Why string
+}
+
+// MeshStreams is the foundation set, in the order a person reads it.
+//
+// **CONTROL names its subjects rather than taking `mesh.control.>`**, because heartbeats live
+// under that prefix and must not be persisted: a lost heartbeat is the next heartbeat, and a
+// stream of them is a stream of the least valuable messages the mesh sends, competing for the
+// same retention as the ones that matter.
+//
+// **EVENTS filters on the `event` token**, which is the reason that token exists. A module's
+// namespace carries both its events and its tool calls; a filter of `mesh.mod.*.>` would persist
+// every tool invocation in the mesh, and a tool call must never be persisted (design 25 §3 keeps
+// tools on core NATS, where a lost call is a timeout the caller already handles).
+func MeshStreams() []Stream {
+	return []Stream{
+		{
+			Name: "CONTROL",
+			// A build's outcome is no longer here: it is the build-machine seat's own event, so one
+			// publish reaches whoever asked, the controller and the catalogue (novox/hq ADR 0121).
+			Subjects:  []string{"mesh.control.*.report", "mesh.control.enrol"},
+			Retention: RetentionWorkQueue,
+			Why: "the store-window guarantee (ADR 0083): the controller naks with a delay while its " +
+				"store is away and the message is redelivered; nothing is dropped",
+		},
+		{
+			Name:      "NODES",
+			Subjects:  []string{"mesh.node.*.declare"},
+			Retention: RetentionLastPerSubject,
+			Why: "one declaration per node, always the newest; a node that sees sequence n refuses " +
+				"n-1 by construction (issue 107)",
+		},
+		{
+			Name: "EVENTS",
+			// A seat's own events ride here too: they are 1:many like any event, and the
+			// `event` token keeps them clear of both the seat's work queue (`accept`) and its
+			// tools (`tool`), which must not be persisted.
+			Subjects:          []string{"mesh.mod.*.event.>", "mesh.seat.*.event.>"},
+			Retention:         RetentionLimits,
+			MaxAge:            7 * 24 * 60 * 60,
+			MaxMsgsPerSubject: 10000,
+			Why: "a subscriber that was down catches up; tool traffic under the same prefix is " +
+				"excluded by the event token; per-subject caps keep a noisy emitter from " +
+				"evicting a quiet one without splitting the stream",
+		},
+	}
+}
+
+// An Asserter is the part of a JetStream connection stream assertion needs. Narrow on purpose: it
+// keeps this testable without a server, and keeps the client library out of everything that only
+// wants to know what the streams are.
+type Asserter interface {
+	// EnsureStream creates the stream if absent and updates it to match if present. It must be
+	// idempotent: the controller asserts on every start, not only at genesis.
+	EnsureStream(s Stream) error
+}
+
+// AssertMeshStreams brings the foundation set into being, in order, and says which one failed
+// rather than that something did.
+//
+// Asserted on every start rather than created once at genesis, because a stream that was deleted,
+// or a mesh raised from a restored backup, must converge rather than run without the guarantee
+// its messages assume. Idempotence is the whole requirement.
+func AssertMeshStreams(a Asserter) error {
+	for _, s := range MeshStreams() {
+		if err := a.EnsureStream(s); err != nil {
+			return fmt.Errorf("asserting stream %s: %w", s.Name, err)
+		}
+	}
+	return nil
+}
+
+// Overlaps reports subject filters claimed by more than one stream.
+//
+// **Corrected against the server**: an earlier version of this comment said NATS accepts
+// overlapping streams and stores the message twice. It does not — it refuses the second stream
+// with "subjects overlap with an existing stream" (verified against nats-server 2.10). The check
+// still earns its place, for a different reason: the server's refusal arrives when the controller
+// is applying, naming one stream, at a moment when the mesh is half-configured. This one arrives
+// where the set is written, names both, and cannot reach a running mesh.
+//
+// It also decides a design question. Because overlap is refused rather than merged, a shared
+// EVENTS stream and a per-module stream cannot coexist — the module's would be refused — so
+// "one stream for most, its own for a module that wants different retention" is not an option
+// the server allows. It is all of one or all of the other.
+func Overlaps() []string {
+	seen := map[string]string{}
+	var clashes []string
+	for _, s := range MeshStreams() {
+		for _, subject := range s.Subjects {
+			if first, ok := seen[subject]; ok {
+				clashes = append(clashes, fmt.Sprintf("%s and %s both claim %s", first, s.Name, subject))
+				continue
+			}
+			seen[subject] = s.Name
+		}
+	}
+	sort.Strings(clashes)
+	return clashes
+}
+
+// The mesh's own consumers.
+//
+// A seat's streams and a module's consumers are derived from declarations (derived.go). These two
+// are not: **the controller is not a module and files no manifest**, so its authority and its
+// subscriptions cannot come from a declaration that does not exist. They are named here, where the
+// mesh's own streams are named, and narrowly — a controller subscribing `mesh.mod.*.event.>` would
+// hear every event in the mesh, which it has no business doing and which would make its permission
+// list stop explaining anything.
+
+// ControllerName is the controller's durable consumer on each stream it reads, and the name its
+// ack subject is derived from (nats.go: `$JS.ACK.<stream>.controller.>`).
+const ControllerName = "controller"
+
+// ControllerFollows are the events the controller reacts to: the catalogue saying a module's
+// current version moved, and a catalogue that has just started saying it may have missed builds.
+//
+// **Derived the same way a module's subscription is**, from the emitter and the bare local event
+// name, rather than written out. They were written out while the catalogue still spelled its events
+// as the old bus's routing keys, and the moment those were converted (novox/hq 04-ISSUES/127) a
+// hard-coded pair became a controller listening to a subject nothing publishes — the same fault, from
+// the other side. Deriving them means the conversion could not leave these behind.
+var ControllerFollows = []string{
+	moduleEventSubject("mesh-catalog", "upgraded"),
+	moduleEventSubject("mesh-catalog", "catching-up"),
+	// A build's outcome, which is the build-machine role's own event now (ADR 0121) rather than a
+	// message on the control branch. Same three audiences, one publish: whoever asked, this, and the
+	// catalogue.
+	seatEventSubject("mesh-build-machine", "built"),
+	// The forge's merges: what moved a source, so the mesh builds what that source produces
+	// without anybody telling it (novox/hq 04-ISSUES/131). Appended, because the index is a name.
+	moduleEventSubject("gitea", "pull.merged"),
+}
+
+// moduleEventSubject is where one module's event lands. The same derivation PermissionsFor uses, so
+// what the controller subscribes and what the emitter is permitted to publish cannot drift apart.
+func moduleEventSubject(module, event string) string {
+	return "mesh.mod." + module + ".event." + event
+}
+
+// seatEventSubject is where a role's own event lands, derived the same way a holder's permission is.
+func seatEventSubject(seat, verb string) string {
+	return "mesh.seat." + seat + ".event." + verb
+}
+
+// MeshConsumers is what the controller consumes, in the order a person reads it.
+//
+// **Unlimited redelivery on CONTROL, deliberately.** The store window's bound is the controller's,
+// not the server's (window.go): a message is held with a nak-and-delay until the controller either
+// takes it or gives up and says so. A max-deliver here would dead-letter a push that was being
+// held through a store restart — the exact message the stream exists to protect — some minutes
+// before the controller had finished deciding about it.
+func MeshConsumers() []Consumer {
+	return []Consumer{
+		{
+			Name:           ControllerName,
+			Stream:         "CONTROL",
+			Push:           true,
+			AckWaitSeconds: 30,
+			Why: "the controller is the single consumer of what nodes say; explicit ack and no " +
+				"max-deliver, because the store window's bound is the controller's own",
+		},
+		{
+			Name:           ControllerName,
+			Stream:         "EVENTS",
+			Filters:        ControllerFollows,
+			Push:           true,
+			AckWaitSeconds: 30,
+			MaxDeliver:     5,
+			Why: "the two events the mesh's own controller reacts to; after max-deliver it " +
+				"dead-letters, because an announcement it cannot act on will not become actionable",
+		},
+	}
+}
+
+// Ensurer is the part of a JetStream connection consumer assertion needs, narrow for the reason
+// Asserter is.
+type Ensurer interface {
+	EnsureConsumer(c Consumer) error
+}
+
+// AssertMeshConsumers brings the controller's own consumers into being, and says which one failed.
+//
+// After the streams, necessarily: a consumer on a stream that does not exist is refused, and the
+// refusal names the stream rather than the order.
+func AssertMeshConsumers(e Ensurer) error {
+	for _, c := range MeshConsumers() {
+		if err := e.EnsureConsumer(c); err != nil {
+			return fmt.Errorf("asserting consumer %s on %s: %w", c.Name, c.Stream, err)
+		}
+	}
+	return nil
+}
@@ -0,0 +1,235 @@
+package broker
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+type recorder struct {
+	seen []Stream
+	fail string
+}
+
+func (r *recorder) EnsureStream(s Stream) error {
+	if s.Name == r.fail {
+		return errors.New("refused")
+	}
+	r.seen = append(r.seen, s)
+	return nil
+}
+
+// The controller asserts on every start, not only at genesis: a stream that was deleted, or a mesh
+// raised from a backup, must converge rather than run without the guarantee its messages assume.
+func TestAssertingTwiceIsTheSameAsOnce(t *testing.T) {
+	a, b := &recorder{}, &recorder{}
+	if err := AssertMeshStreams(a); err != nil {
+		t.Fatal(err)
+	}
+	if err := AssertMeshStreams(a); err != nil {
+		t.Fatal(err)
+	}
+	if err := AssertMeshStreams(b); err != nil {
+		t.Fatal(err)
+	}
+	if len(a.seen) != 2*len(b.seen) {
+		t.Fatalf("asserted %d then %d; assertion is not repeatable", len(a.seen), len(b.seen))
+	}
+}
+
+func TestAFailedAssertionNamesItsStream(t *testing.T) {
+	err := AssertMeshStreams(&recorder{fail: "NODES"})
+	if err == nil || !strings.Contains(err.Error(), "NODES") {
+		t.Fatalf("got %v, which does not say which stream failed", err)
+	}
+}
+
+// Two streams matching one subject is accepted by NATS and stores the message twice under two
+// retentions. Nothing reports that, so it is refused where the set is written.
+func TestNoTwoStreamsClaimTheSameSubject(t *testing.T) {
+	if clashes := Overlaps(); len(clashes) != 0 {
+		t.Fatalf("overlapping subject filters: %v", clashes)
+	}
+}
+
+// A heartbeat under mesh.control.> must not be persisted: a lost one is the next one, and a
+// stream of them competes for retention with the messages that matter.
+func TestHeartbeatsAreNotInTheControlStream(t *testing.T) {
+	for _, s := range MeshStreams() {
+		for _, subject := range s.Subjects {
+			if subject == "mesh.control.>" || strings.Contains(subject, "alive") {
+				t.Fatalf("stream %s claims %q, which captures heartbeats", s.Name, subject)
+			}
+		}
+	}
+}
+
+// The reason the kind token exists: a filter over a module's whole namespace would persist every
+// tool call in the mesh.
+func TestTheEventsStreamDoesNotCaptureToolCalls(t *testing.T) {
+	var events Stream
+	for _, s := range MeshStreams() {
+		if s.Name == "EVENTS" {
+			events = s
+		}
+	}
+	// Nothing a tool call rides may match any of the filters — a module's or a seat's.
+	for _, tool := range []string{
+		"mesh.mod.billing.tool.status",
+		"mesh.seat.telegram-sender.tool.status",
+		"mesh.seat.telegram-sender.accept.send", // work, not an event: its own stream
+	} {
+		for _, f := range events.Subjects {
+			if subjectMatches(f, tool) {
+				t.Fatalf("%q matches the events filter %q, so it would be persisted here", tool, f)
+			}
+		}
+	}
+	// And both kinds of event do match.
+	for _, event := range []string{
+		"mesh.mod.billing.event.order.placed",
+		"mesh.seat.telegram-sender.event.delivered",
+	} {
+		matched := false
+		for _, f := range events.Subjects {
+			if subjectMatches(f, event) {
+				matched = true
+			}
+		}
+		if !matched {
+			t.Fatalf("%q matches no events filter, so nothing would keep it", event)
+		}
+	}
+}
+
+// subjectMatches is NATS subject matching, enough for these filters: `*` is one token, `>` is the
+// rest.
+func subjectMatches(filter, subject string) bool {
+	f, s := strings.Split(filter, "."), strings.Split(subject, ".")
+	for i, tok := range f {
+		if tok == ">" {
+			return i <= len(s)
+		}
+		if i >= len(s) {
+			return false
+		}
+		if tok != "*" && tok != s[i] {
+			return false
+		}
+	}
+	return len(f) == len(s)
+}
+
+// Each relationship's retention is the thing that makes it what it is (design 29 §4).
+func TestEachStreamCarriesTheRetentionItsShapeNeeds(t *testing.T) {
+	want := map[string]Retention{
+		"CONTROL": RetentionWorkQueue,
+		"NODES":   RetentionLastPerSubject,
+		"EVENTS":  RetentionLimits,
+	}
+	got := map[string]Retention{}
+	for _, s := range MeshStreams() {
+		got[s.Name] = s.Retention
+		if s.Why == "" {
+			t.Errorf("stream %s says no reason it exists", s.Name)
+		}
+	}
+	if len(got) != len(want) {
+		t.Fatalf("the foundation set is %v", got)
+	}
+	for name, r := range want {
+		if got[name] != r {
+			t.Errorf("%s retains as %q, expected %q", name, got[name], r)
+		}
+	}
+}
+
+// The order the bus's objects are asserted in, because getting it wrong is a refusal that names the
+// wrong thing: a consumer on a stream that does not exist is refused naming the *stream*, so
+// somebody reading it goes looking for a deletion instead of a reversed pair of lines.
+func TestTheBusesObjectsAreAssertedStreamsBeforeConsumers(t *testing.T) {
+	r := &recording{}
+	if err := Raise(r, []string{"anchor", "laptop"}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Every stream before every consumer.
+	firstConsumer := -1
+	for i, step := range r.steps {
+		if strings.HasPrefix(step, "consumer ") && firstConsumer < 0 {
+			firstConsumer = i
+		}
+		if strings.HasPrefix(step, "stream ") && firstConsumer >= 0 {
+			t.Fatalf("a stream was asserted after a consumer: %v", r.steps)
+		}
+	}
+	if firstConsumer < 0 {
+		t.Fatalf("no consumer was asserted: %v", r.steps)
+	}
+
+	// And every node got one, named after it — without which that node hears nothing while
+	// everything else about it looks correct.
+	for _, node := range []string{"anchor", "laptop"} {
+		if !containsStep(r.steps, "consumer NODES/"+node) {
+			t.Errorf("%s was given no way to hear its declaration: %v", node, r.steps)
+		}
+	}
+	// And the controller its own, on both streams it reads.
+	for _, want := range []string{"consumer CONTROL/controller", "consumer EVENTS/controller"} {
+		if !containsStep(r.steps, want) {
+			t.Errorf("the controller is missing %s: %v", want, r.steps)
+		}
+	}
+}
+
+// A seat's work queue is asserted whether or not anybody holds it; the holder's worker only when
+// somebody does. **The stream without the consumer is the point**: work queues until a holder
+// appears, so installing the module later flushes the backlog instead of having lost it.
+func TestASeatsQueueExistsBeforeItsHolderDoes(t *testing.T) {
+	seats := []DeclaredSeat{{Name: "telegram-sender", Accepts: []string{"send"}}}
+
+	unheld := &recording{}
+	if err := RaiseSeats(unheld, seats, nil); err != nil {
+		t.Fatal(err)
+	}
+	if !containsStep(unheld.steps, "stream SEAT_TELEGRAM_SENDER") {
+		t.Fatalf("a declared seat got no work queue: %v", unheld.steps)
+	}
+	for _, step := range unheld.steps {
+		if strings.HasPrefix(step, "consumer ") {
+			t.Fatalf("a seat nobody holds got a worker: %v", unheld.steps)
+		}
+	}
+
+	held := &recording{}
+	if err := RaiseSeats(held, seats, map[string]Holder{
+		"telegram-sender": {Node: "anchor", Module: "telegram"},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if !containsStep(held.steps, "consumer SEAT_TELEGRAM_SENDER/SEAT_TELEGRAM_SENDER_worker") {
+		t.Fatalf("the seat's holder got no worker: %v", held.steps)
+	}
+}
+
+// recording is a connection to the bus that writes down what it was asked for.
+type recording struct{ steps []string }
+
+func (r *recording) EnsureStream(s Stream) error {
+	r.steps = append(r.steps, "stream "+s.Name)
+	return nil
+}
+
+func (r *recording) EnsureConsumer(c Consumer) error {
+	r.steps = append(r.steps, "consumer "+c.Stream+"/"+c.Name)
+	return nil
+}
+
+func containsStep(steps []string, want string) bool {
+	for _, s := range steps {
+		if s == want {
+			return true
+		}
+	}
+	return false
+}
@@ -0,0 +1,56 @@
+# Composed by the mesh controller. Do not edit: the next composition overwrites it.
+# Accounts and permissions are derived from what each module declares and nothing
+# else (novox/hq ADR 0043, design 29 §2).
+
+port: 4222
+http: 127.0.0.1:8222
+
+tls {
+  cert_file: "/tls/tls.crt"
+  key_file: "/tls/tls.key"
+  ca_file: "/tls/ca.crt"
+}
+
+jetstream {
+  store_dir: "/data"
+}
+
+# The mesh's users, composed by the controller. Do not edit: the next
+# composition overwrites it. Permissions are derived from what each module
+# declares and nothing else (novox/hq ADR 0043, design 29 §2).
+
+accounts {
+  MESH {
+    jetstream: enabled
+    users = [
+      { user: "controller", password: "$2a$11$cccccccccccccccccccccc", permissions: {
+        publish: { allow: ["$JS.ACK.CONTROL.controller.>", "$JS.ACK.EVENTS.controller.>", "$JS.API.>", "_INBOX.enrol.>", "mesh.control.>", "mesh.mod.*.tool.>", "mesh.node.>", "mesh.seat.mesh-build-machine.accept.>"] }
+        subscribe: { allow: ["$JS.API.>", "_DELIVER.controller", "_DELIVER.controller.>", "_INBOX.controller.>", "mesh.control.>", "mesh.mod.gitea.event.pull.merged", "mesh.mod.mesh-catalog.event.catching-up", "mesh.mod.mesh-catalog.event.upgraded", "mesh.seat.mesh-build-machine.event.built"] }
+        allow_responses: { max: 1, ttl: "1m" }
+      } }
+      { user: "enrol.one", password: "$2a$11$eeeeeeeeeeeeeeeeeeeeee", permissions: {
+        publish: { allow: ["mesh.control.enrol"] }
+        subscribe: { allow: ["_INBOX.enrol.one.>"] }
+      } }
+      { user: "node.one", password: "$2a$11$nnnnnnnnnnnnnnnnnnnnnn", permissions: {
+        publish: { allow: ["$JS.ACK.NODES.one.>", "$JS.API.CONSUMER.INFO.NODES.one", "mesh.control.one.>"] }
+        subscribe: { allow: ["_DELIVER.one", "_INBOX.node.one.>", "mesh.node.one.declare"] }
+      } }
+      { user: "one.telegram", password: "$2a$11$tttttttttttttttttttttt", permissions: {
+        publish: { allow: ["$JS.ACK.EVENTS.one_telegram.>", "$JS.ACK.SEAT_TELEGRAM_SENDER.SEAT_TELEGRAM_SENDER_worker.>", "$JS.API.CONSUMER.INFO.EVENTS.one_telegram", "$JS.API.CONSUMER.INFO.SEAT_TELEGRAM_SENDER.SEAT_TELEGRAM_SENDER_worker", "$JS.API.CONSUMER.MSG.NEXT.EVENTS.one_telegram", "mesh.seat.telegram-sender.event.delivered", "mesh.seat.telegram-sender.event.failed"] }
+        subscribe: { allow: ["_DELIVER.SEAT_TELEGRAM_SENDER_worker", "_INBOX.one.telegram.>", "mesh.mod.telegram.tool.>", "mesh.seat.telegram-sender.accept.send"] }
+        allow_responses: { max: 1, ttl: "1m" }
+      } }
+      { user: "two.audit", password: "$2a$11$aaaaaaaaaaaaaaaaaaaaaa", permissions: {
+        publish: { allow: ["$JS.ACK.EVENTS.two_audit.>", "$JS.API.CONSUMER.INFO.EVENTS.two_audit", "$JS.API.CONSUMER.MSG.NEXT.EVENTS.two_audit"] }
+        subscribe: { allow: ["_INBOX.two.audit.>", "mesh.mod.audit.tool.>", "mesh.mod.shop.event.order.placed"] }
+        allow_responses: { max: 1, ttl: "1m" }
+      } }
+      { user: "two.shop", password: "$2a$11$ssssssssssssssssssssss", permissions: {
+        publish: { allow: ["$JS.ACK.EVENTS.two_shop.>", "$JS.API.CONSUMER.INFO.EVENTS.two_shop", "$JS.API.CONSUMER.MSG.NEXT.EVENTS.two_shop", "mesh.mod.shop.event.order.placed", "mesh.seat.telegram-sender.accept.send"] }
+        subscribe: { allow: ["_INBOX.two.shop.>", "mesh.mod.shop.tool.>"] }
+        allow_responses: { max: 1, ttl: "1m" }
+      } }
+    ]
+  }
+}
@@ -0,0 +1,127 @@
+package broker
+
+import (
+	"fmt"
+	"sort"
+)
+
+// Every user the composed file should contain, derived from what the mesh knows.
+//
+// **The list is derived, never kept.** A stored user list would be a second account of who may
+// reach the bus, able to disagree with the records it came from — and the disagreement would be
+// invisible, because both would look internally consistent. So this is a pure function of the
+// mesh's records, run again every time the file is written.
+//
+// Records are mirrored into this package's own types rather than imported from the catalogue, for
+// the reason DeclaredSeat is: composing authority is a different job from parsing a manifest, and
+// this package stays free of the other's types so a change to a manifest field cannot quietly widen
+// a permission.
+
+// Declared is one module on one node, as composing its authority needs it.
+type Declared struct {
+	Module   string
+	Emits    []string
+	Consumes []string
+	Serves   []string
+	// Holds are the seats this module claims, with the protocol each seat declares. A seat the
+	// mesh defines for itself declares no protocol, so holding one grants nothing on the bus —
+	// which is right: those seats are about who does a job, not about who may say what.
+	Holds []Seat
+	// Uses are the seats this module sends to.
+	Uses []Seat
+	// Watches are the seats whose events it consumes.
+	Watches []Seat
+}
+
+// Records is what composing a user list needs to know about the mesh, and nothing more.
+type Records struct {
+	// Nodes is every machine the mesh knows. Each gets a host user.
+	Nodes []string
+	// Assigned is the modules on each node, as they declare themselves.
+	Assigned map[string][]Declared
+	// Enrolling is every node with a live token — one enrolment user each, because the inbox an
+	// answer goes to is scoped to the token and a shared one is one machine reading another's
+	// sealed credentials (design 25 §6).
+	Enrolling []string
+	// People is each person's name against the tools they may invoke, `*` for an administrator.
+	People map[string][]string
+}
+
+// Users is every user the composed file should contain, in the order it will be written.
+//
+// The controller is always first and always present: a mesh whose own controller is not in the file
+// is a mesh that cannot be told anything, and there is no state of the records in which that is
+// correct.
+func Users(r Records) ([]Principal, error) {
+	out := []Principal{{Kind: KindController}}
+
+	for _, node := range sortedCopy(r.Nodes) {
+		out = append(out, Principal{Kind: KindNode, Node: node})
+		for _, d := range r.Assigned[node] {
+			out = append(out, Principal{
+				Kind: KindModule, Node: node, Module: d.Module,
+				Emits: d.Emits, Consumes: d.Consumes, Serves: d.Serves,
+				Holds: d.Holds, Uses: d.Uses, Watches: d.Watches,
+			})
+		}
+	}
+	for _, node := range sortedCopy(r.Enrolling) {
+		out = append(out, Principal{Kind: KindEnrolment, Node: node})
+	}
+	for _, person := range sortedNames(r.People) {
+		out = append(out, Principal{Kind: KindPerson, Module: person, Invokes: r.People[person]})
+	}
+
+	// Refused here rather than discovered by the server. Two users with one name is a file the
+	// server reads as one of them, and which one depends on the order — so a module assigned to a
+	// node twice, or a person named after nothing, is a composition that must not be written.
+	seen := map[string]string{}
+	for _, p := range out {
+		name := p.Username()
+		if name == "" || name == "." {
+			return nil, fmt.Errorf("a %s user has no name, so nothing could authenticate as it", p.Kind)
+		}
+		if first, already := seen[name]; already {
+			return nil, fmt.Errorf(
+				"two users would be called %q (a %s and a %s): the server would read the file as "+
+					"one of them, and which one depends on the order", name, first, p.Kind)
+		}
+		seen[name] = string(p.Kind)
+	}
+	return out, nil
+}
+
+// WithPasswords fills each user's hash from what the mesh minted, and says which users have none.
+//
+// **Separated from Users because they fail differently.** A user missing from the records is a bug
+// in deriving them; a user with no password is a step that has not happened yet — a module assigned
+// but never given a credential, a node enrolled before this existed. The second is ordinary and its
+// remedy is to mint one, so it is named rather than returned as an error, and the caller decides
+// whether a partial composition is worth writing.
+func WithPasswords(principals []Principal, hashes map[string]string) (filled []Principal, missing []string) {
+	for _, p := range principals {
+		hash, ok := hashes[p.Username()]
+		if !ok || hash == "" {
+			missing = append(missing, p.Username())
+			continue
+		}
+		p.PasswordHash = hash
+		filled = append(filled, p)
+	}
+	return filled, missing
+}
+
+func sortedCopy(in []string) []string {
+	out := append([]string(nil), in...)
+	sort.Strings(out)
+	return out
+}
+
+func sortedNames(in map[string][]string) []string {
+	out := make([]string, 0, len(in))
+	for k := range in {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
@@ -0,0 +1,247 @@
+package broker
+
+import (
+	"strings"
+	"testing"
+)
+
+// Deriving the bus's user list from the mesh's records.
+//
+// Every test here is about a way the list could be wrong that the server would not tell anybody
+// about: a user missing, a user named twice, a user with authority it did not declare.
+
+func someRecords() Records {
+	return Records{
+		Nodes: []string{"two", "one"},
+		Assigned: map[string][]Declared{
+			"one": {{Module: "telegram", Serves: []string{"status"}}},
+			"two": {{Module: "shop", Emits: []string{"order.placed"}}},
+		},
+		Enrolling: []string{"three"},
+		People:    map[string][]string{"ada": {"mesh-catalog.catalog_tools"}},
+	}
+}
+
+func namesOf(t *testing.T, r Records) []string {
+	t.Helper()
+	users, err := Users(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := make([]string, 0, len(users))
+	for _, u := range users {
+		out = append(out, u.Username())
+	}
+	return out
+}
+
+// The controller is always there. A mesh whose own controller is not in the file is a mesh that
+// cannot be told anything, and there is no state of the records in which that is correct.
+func TestTheControllerIsAlwaysInTheList(t *testing.T) {
+	for _, r := range []Records{{}, someRecords()} {
+		names := namesOf(t, r)
+		if len(names) == 0 || names[0] != "controller" {
+			t.Fatalf("the controller is not first in %v", names)
+		}
+	}
+}
+
+// One user per node, one per module per node, one per live token and one per person — and nothing
+// else, because a user nobody derived is a user nobody can explain.
+func TestEveryRecordBecomesExactlyOneUser(t *testing.T) {
+	names := namesOf(t, someRecords())
+	want := []string{
+		"controller",
+		"node.one", "one.telegram",
+		"node.two", "two.shop",
+		"enrol.three",
+		"person.ada",
+	}
+	if strings.Join(names, ",") != strings.Join(want, ",") {
+		t.Fatalf("derived %v\n    want %v", names, want)
+	}
+}
+
+// Two users with one name is a file the server reads as one of them, and which one depends on the
+// order. Refused here, where both can be named, rather than left to be whichever the server picked.
+func TestTwoUsersWithOneNameAreRefused(t *testing.T) {
+	r := someRecords()
+	r.Assigned["one"] = append(r.Assigned["one"], Declared{Module: "telegram"})
+	_, err := Users(r)
+	if err == nil {
+		t.Fatal("a module assigned twice to one node composed two users with one name")
+	}
+	if !strings.Contains(err.Error(), "one.telegram") {
+		t.Fatalf("the refusal does not name the user: %v", err)
+	}
+}
+
+// A module's authority is what it declared and nothing more, carried through the derivation intact —
+// because this is the step where a mistake would grant something no manifest asked for.
+func TestAModulesAuthorityIsWhatItDeclared(t *testing.T) {
+	seat := Seat{Name: "telegram-sender", Accepts: []string{"send"}, Emits: []string{"delivered"}}
+	users, err := Users(Records{
+		Nodes: []string{"one"},
+		Assigned: map[string][]Declared{"one": {{
+			Module: "shop", Emits: []string{"order.placed"}, Uses: []Seat{seat},
+		}}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	perms, err := PermissionsFor(users[len(users)-1])
+	if err != nil {
+		t.Fatal(err)
+	}
+	has(t, perms.Publish, "mesh.mod.shop.event.order.placed")
+	has(t, perms.Publish, "mesh.seat.telegram-sender.accept.send")
+	// A seat it uses, not one it holds: it may submit work and may not publish the seat's own
+	// events, or it could lie about outcomes on a role somebody else fills.
+	hasNot(t, perms.Publish, "mesh.seat.telegram-sender.event.delivered")
+	hasNot(t, perms.Subscribe, "mesh.seat.telegram-sender.accept.send")
+}
+
+// A user the mesh has never minted a password for is named rather than silently dropped or
+// composed as a user anybody is. It is an ordinary situation — a module assigned a moment ago — and
+// the remedy is to mint one, so the caller decides whether to write a partial file.
+func TestAUserWithNoPasswordIsNamedRatherThanWritten(t *testing.T) {
+	users, err := Users(someRecords())
+	if err != nil {
+		t.Fatal(err)
+	}
+	filled, missing := WithPasswords(users, map[string]string{
+		"controller": "$2a$hash", "node.one": "$2a$hash",
+	})
+	if len(filled) != 2 {
+		t.Fatalf("composed %d users from two hashes", len(filled))
+	}
+	if len(missing) != len(users)-2 {
+		t.Fatalf("%d users are missing a password, of %d: %v", len(missing), len(users), missing)
+	}
+	for _, p := range filled {
+		if p.PasswordHash == "" {
+			t.Fatalf("%s was kept with no password, which is a user anybody is", p.Username())
+		}
+	}
+}
+
+// And the whole thing composes: records in, a file the server would read out.
+func TestRecordsComposeIntoAFile(t *testing.T) {
+	users, err := Users(someRecords())
+	if err != nil {
+		t.Fatal(err)
+	}
+	hashes := map[string]string{}
+	for _, u := range users {
+		hashes[u.Username()] = "$2a$11$" + strings.Repeat("x", 22)
+	}
+	filled, missing := WithPasswords(users, hashes)
+	if len(missing) != 0 {
+		t.Fatalf("users with no password: %v", missing)
+	}
+	got, err := Compose(Server{ClientPort: 4222, MonitoringPort: 8222, StoreDir: "/data",
+		TLSCert: "/tls/tls.crt", TLSKey: "/tls/tls.key", TLSCA: "/tls/ca.crt"}, filled)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{
+		`user: "controller"`, `user: "node.one"`, `user: "one.telegram"`,
+		`user: "enrol.three"`, `user: "person.ada"`,
+		`"_INBOX.enrol.three.>"`, `"mesh.mod.mesh-catalog.tool.catalog_tools"`,
+	} {
+		if !strings.Contains(got, want) {
+			t.Errorf("the composed file does not contain %s", want)
+		}
+	}
+}
+
+// The accounts block alone is what the mesh writes, and it holds nothing about the server.
+//
+// **The split is the whole design decision** (ComposeAccounts): ports, TLS paths and a store
+// directory are properties of the container the module raises, and a controller that wrote them
+// would have to be kept in step with a Dockerfile it never sees. So this test says what must not be
+// in the file as plainly as what must.
+func TestWhatTheMeshWritesIsUsersAndNothingAboutTheServer(t *testing.T) {
+	users, err := Users(someRecords())
+	if err != nil {
+		t.Fatal(err)
+	}
+	hashes := map[string]string{}
+	for _, u := range users {
+		hashes[u.Username()] = "$2a$11$" + strings.Repeat("x", 22)
+	}
+	filled, missing := WithPasswords(users, hashes)
+	if len(missing) != 0 {
+		t.Fatalf("users with no password: %v", missing)
+	}
+	got, err := ComposeAccounts(filled)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, want := range []string{"accounts {", `user: "controller"`, `user: "one.telegram"`} {
+		if !strings.Contains(got, want) {
+			t.Errorf("the accounts file does not contain %s", want)
+		}
+	}
+	// None of the server's own settings. Each of these in the mesh's file is a value the controller
+	// would then own, and the module could no longer change its own image without the mesh agreeing.
+	// `jetstream {` is the server's block (its store, its limits); `jetstream: enabled` inside the
+	// account is the account's, and the mesh owns the account — a user in it is told "JetStream
+	// not enabled for account" without it (2026-09-28).
+	if !strings.Contains(got, "jetstream: enabled") {
+		t.Errorf("the account does not enable JetStream, so no user in it can bind a consumer")
+	}
+	for _, absent := range []string{"port:", "http:", "jetstream {", "tls {", "store_dir", "cert_file"} {
+		if strings.Contains(got, absent) {
+			t.Errorf("the accounts file contains %q, which belongs to the module that raises the "+
+				"server, not to the mesh", absent)
+		}
+	}
+}
+
+// A user with no password is refused here too, not only by the whole-file composition: this is the
+// function the controller actually calls, and a user without a password is a user anybody is.
+func TestTheAccountsFileRefusesAUserWithNoPassword(t *testing.T) {
+	if _, err := ComposeAccounts([]Principal{{Kind: KindController}}); err == nil {
+		t.Fatal("a user with no password hash was written")
+	}
+}
+
+// **A user list is composed for a bus the mesh has not moved onto yet**, and that is the whole of
+// step 2 (novox/hq ADR 0116): the server stands in the mesh carrying nothing, on its own ports, while
+// every node is still on the bus it was on.
+//
+// Pinned because the first version of the composing step got it backwards — it wrote the list only
+// once the controller was already on the new bus, which is a step that cannot be taken: the module
+// comes up, finds no accounts file, and waits for one the controller had decided not to write.
+func TestAUserListIsComposedBeforeAnythingMovesOntoTheBus(t *testing.T) {
+	// Exactly the records of a mesh mid-change: everything running, nothing on the new bus.
+	users, err := Users(Records{
+		Nodes:    []string{"anchor"},
+		Assigned: map[string][]Declared{"anchor": {{Module: "nats"}}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	hashes := map[string]string{}
+	for _, u := range users {
+		hashes[u.Username()] = "$2a$11$" + strings.Repeat("x", 22)
+	}
+	filled, missing := WithPasswords(users, hashes)
+	if len(missing) != 0 {
+		t.Fatalf("users with no credential: %v", missing)
+	}
+	accounts, err := ComposeAccounts(filled)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// The controller's own user above all: a file without it is a bus its writer cannot connect to,
+	// which is what the server would be left holding the moment it starts.
+	if !strings.Contains(accounts, `user: "controller"`) {
+		t.Fatalf("the composed list does not contain the controller:\n%s", accounts)
+	}
+	if !strings.Contains(accounts, `user: "node.anchor"`) {
+		t.Errorf("the composed list does not contain the machine running the bus")
+	}
+}
@@ -169,6 +169,8 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 	}

 	var built []catalogue.Built
+	// stoodOn is every base the build was handed, as resolved — the edges the catalogue derives.
+	var stoodOn []string
 	if manifest.Build != nil {
 		// What this module said it stands on, answered with what this mesh actually holds. Done
 		// before anything is built, so a missing base is refused in front of the person who can
@@ -186,11 +188,12 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 			}
 			return from, nil
 		}
-		args, err := standingOn(ctx, manifest, held, mirror)
+		args, bases, err := standingOn(ctx, manifest, held, mirror)
 		if err != nil {
 			say("bases", "UNMET: %v", err)
 			return Result{}, err
 		}
+		stoodOn = bases
 		if len(args) > 0 {
 			say("bases", "%d resolved from what the mesh holds", len(args)/2)
 		}
@@ -217,7 +220,7 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 	}
 	say("done", "%s at %s — %d artifact(s) pinned", manifest.Module, short(commit), len(built))
 	return Result{Manifest: resolved, Commit: commit, Built: built,
-		Against: against(within, manifest)}, nil
+		Against: against(within, manifest, stoodOn)}, nil
 }

 // Log is where a build says what it is doing, step by step. Nil is silent — the tests pass none,
@@ -339,14 +342,27 @@ func describe(path string) string {
 // allowed to name — a tag is something somebody else can move under you.
 var pinnedImage = regexp.MustCompile(`[A-Za-z0-9][A-Za-z0-9._/:-]*@sha256:[0-9a-f]{64}`)

-// against reads what this module's image artifacts are built on top of, out of the files that
-// build them. Nothing is guessed: a reference that is not written down is not reported.
-func against(within string, manifest catalogue.Manifest) []string {
+// against is what this module's image artifacts are built on top of: every base the mesh resolved
+// and handed the recipe as a build argument (`build.on`), and any image a recipe pins by digest
+// itself. Nothing is guessed: a reference that was neither resolved nor written down is not
+// reported.
+//
+// **The resolved bases are the edges.** A recipe reads its base from an argument (`FROM
+// ${RUNTIME_BASE}`), so the digest is never in the file, and a derivation that read files alone
+// recorded no edge for any module on the mesh — which is why nothing knew what a changed base
+// meant to rebuild (novox/hq 04-ISSUES/131).
+func against(within string, manifest catalogue.Manifest, resolved []string) []string {
 	if manifest.Build == nil {
 		return nil
 	}
 	seen := map[string]bool{}
 	var out []string
+	for _, r := range resolved {
+		if r != "" && !seen[r] {
+			seen[r] = true
+			out = append(out, r)
+		}
+	}
 	for _, a := range manifest.Build.Artifacts {
 		if a.Kind != catalogue.ArtifactImage || a.From == "" {
 			continue
@@ -704,40 +720,42 @@ var _ io.Writer = (*stringWriter)(nil)
 // built cannot be built here yet, and the useful sentence names which module is missing — not the
 // one a container runtime produces when a recipe's first line refers to an image nobody has.
 //
-// The order is fixed so two builds of one commit invoke the same command.
+// The order is fixed so two builds of one commit invoke the same command. Returned alongside the
+// arguments is every reference they resolved to, which is what the build stood on.
 func standingOn(ctx context.Context, manifest catalogue.Manifest, held map[string]string,
-	mirror func(ctx context.Context, from, repository string) (string, error)) ([]string, error) {
+	mirror func(ctx context.Context, from, repository string) (string, error)) ([]string, []string, error) {
 	if manifest.Build == nil || len(manifest.Build.On) == 0 {
-		return nil, nil
+		return nil, nil, nil
 	}
 	on := append([]catalogue.BuildsOn{}, manifest.Build.On...)
 	sort.Slice(on, func(i, j int) bool { return on[i].Arg < on[j].Arg })

-	var args []string
+	var args, resolved []string
 	for _, base := range on {
 		if base.Image != "" {
 			// A vendor's image, declared (novox/hq 04-ISSUES/064, ADR 0097). Pinned, because a tag
 			// is what somebody else can move; copied into the mesh's registry, because a build
 			// that reaches a public registry on its own is a build that works sometimes.
 			if base.Arg == "" || base.Module != "" || base.Artifact != "" {
-				return nil, fmt.Errorf(
+				return nil, nil, fmt.Errorf(
 					"%s stands on the image %s, and a base is either a module's artifact or an "+
 						"image — never both — read from one build argument", manifest.Module, base.Image)
 			}
 			if !strings.Contains(base.Image, "@sha256:") {
-				return nil, fmt.Errorf(
+				return nil, nil, fmt.Errorf(
 					"%s stands on the image %q, which is not pinned by digest. A tag is what "+
 						"somebody else can move; name it as <image>@sha256:…", manifest.Module, base.Image)
 			}
 			reference, err := mirror(ctx, base.Image, manifest.Module+"/on-"+strings.ToLower(base.Arg))
 			if err != nil {
-				return nil, fmt.Errorf("%s stands on %s: %w", manifest.Module, base.Image, err)
+				return nil, nil, fmt.Errorf("%s stands on %s: %w", manifest.Module, base.Image, err)
 			}
 			args = append(args, "--build-arg", base.Arg+"="+reference)
+			resolved = append(resolved, reference)
 			continue
 		}
 		if base.Arg == "" || base.Module == "" || base.Artifact == "" {
-			return nil, fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"%s says its build stands on something, and does not say all of what: a base "+
 					"needs the module, the artifact, and the build argument the recipe reads it "+
 					"from", manifest.Module)
@@ -745,14 +763,15 @@ func standingOn(ctx context.Context, manifest catalogue.Manifest, held map[strin
 		key := base.Module + "/" + base.Artifact
 		reference, has := held[key]
 		if !has {
-			return nil, fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"%s builds on %s, and this mesh has not built it. Build %s first — every module "+
 					"in this toolchain stands on it, so it is the thing to have before anything "+
 					"else", manifest.Module, key, base.Module)
 		}
 		args = append(args, "--build-arg", base.Arg+"="+reference)
+		resolved = append(resolved, reference)
 	}
-	return args, nil
+	return args, resolved, nil
 }

 // compile runs a module's own code through its toolchain, and says where the result is.
@@ -22,7 +22,7 @@ func TestABaseTheMeshHasNotBuiltIsRefused(t *testing.T) {
 			On: []catalogue.BuildsOn{{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"}},
 		},
 	}
-	_, err := standingOn(context.Background(), manifest, map[string]string{}, noMirror)
+	_, _, err := standingOn(context.Background(), manifest, map[string]string{}, noMirror)
 	if err == nil {
 		t.Fatal("a base nothing has built was accepted; the build would have failed on its first line")
 	}
@@ -42,7 +42,7 @@ func TestABaseTheMeshHoldsBecomesABuildArgument(t *testing.T) {
 		},
 	}
 	held := map[string]string{"mesh-tools/runtime": "127.0.0.1:5000/mesh-tools/runtime@sha256:" + strings.Repeat("a", 64)}
-	args, err := standingOn(context.Background(), manifest, held, noMirror)
+	args, _, err := standingOn(context.Background(), manifest, held, noMirror)
 	if err != nil {
 		t.Fatalf("a base this mesh holds was refused: %v", err)
 	}
@@ -54,7 +54,7 @@ func TestABaseTheMeshHoldsBecomesABuildArgument(t *testing.T) {

 // A module naming no base asks for nothing, which is most modules.
 func TestAModuleNamingNoBaseAddsNoArguments(t *testing.T) {
-	args, err := standingOn(context.Background(), catalogue.Manifest{Module: "hello-web", Build: &catalogue.Build{}}, nil, noMirror)
+	args, _, err := standingOn(context.Background(), catalogue.Manifest{Module: "hello-web", Build: &catalogue.Build{}}, nil, noMirror)
 	if err != nil || args != nil {
 		t.Fatalf("a module naming no base produced %v, %v", args, err)
 	}
@@ -66,7 +66,7 @@ func TestAnIncompleteBaseIsRefused(t *testing.T) {
 		Module: "postgres",
 		Build:  &catalogue.Build{On: []catalogue.BuildsOn{{Module: "mesh-tools", Artifact: "runtime"}}},
 	}
-	if _, err := standingOn(context.Background(), manifest, map[string]string{"mesh-tools/runtime": "x"}, noMirror); err == nil {
+	if _, _, err := standingOn(context.Background(), manifest, map[string]string{"mesh-tools/runtime": "x"}, noMirror); err == nil {
 		t.Fatal("a base with no build argument was accepted; nothing would have read it")
 	}
 }
@@ -86,7 +86,7 @@ func TestADeclaredVendorImageIsCopiedInAndHandedToTheRecipe(t *testing.T) {
 		},
 	}
 	var asked []string
-	args, err := standingOn(context.Background(), manifest, nil, func(_ context.Context, from, repository string) (string, error) {
+	args, _, err := standingOn(context.Background(), manifest, nil, func(_ context.Context, from, repository string) (string, error) {
 		asked = append(asked, from+" -> "+repository)
 		return "127.0.0.1:5000/" + repository + "@sha256:" + strings.Repeat("d", 64), nil
 	})
@@ -101,7 +101,7 @@ func TestADeclaredVendorImageIsCopiedInAndHandedToTheRecipe(t *testing.T) {
 	}
 	// Unpinned, it is refused: a tag is what somebody else can move.
 	manifest.Build.On[0].Image = "quay.io/minio/mc:latest"
-	if _, err := standingOn(context.Background(), manifest, nil, noMirror); err == nil || !strings.Contains(err.Error(), "not pinned") {
+	if _, _, err := standingOn(context.Background(), manifest, nil, noMirror); err == nil || !strings.Contains(err.Error(), "not pinned") {
 		t.Fatalf("an unpinned vendor image was accepted: %v", err)
 	}
 }
@@ -151,3 +151,31 @@ func TestARecipeIsReadAsInstructions(t *testing.T) {
 		t.Fatalf("a heredoc line or a continued stage was read as a base: %v", bases)
 	}
 }
+
+// What a build was handed as its bases is what it stood on — recorded, so a changed base knows what
+// to rebuild (novox/hq 04-ISSUES/131). A recipe reads the base from an argument, so nothing else
+// could know.
+func TestTheBasesABuildWasHandedAreWhatItStoodOn(t *testing.T) {
+	manifest := catalogue.Manifest{
+		Module: "gitea",
+		Build: &catalogue.Build{
+			On: []catalogue.BuildsOn{
+				{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"},
+				{Arg: "BUILD_BASE", Module: "mesh-tools", Artifact: "build"},
+			},
+			Artifacts: []catalogue.Artifact{{Name: "runtime", Kind: catalogue.ArtifactImage, From: "Dockerfile"}},
+		},
+	}
+	held := map[string]string{
+		"mesh-tools/runtime": "127.0.0.1:5000/mesh-tools/runtime@sha256:" + strings.Repeat("a", 64),
+		"mesh-tools/build":   "127.0.0.1:5000/mesh-tools/build@sha256:" + strings.Repeat("b", 64),
+	}
+	_, resolved, err := standingOn(context.Background(), manifest, held, noMirror)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := against(t.TempDir(), manifest, resolved)
+	if len(got) != 2 || got[0] != held["mesh-tools/build"] || got[1] != held["mesh-tools/runtime"] {
+		t.Fatalf("the bases the build was handed were not what it stood on: %v", got)
+	}
+}
@@ -0,0 +1,48 @@
+package catalogue
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// **The word does not come back through a manifest** (novox/hq ADR 0131). A module that wants
+// messaging wants the mesh's bus, reached through the sdk and named by the `mesh-broker` seat. Naming
+// the old wire protocol asks for the one server being retired, so both directions are refused at the
+// parser — this is judged from the manifest alone, no store needed.
+
+func TestAManifestProvidingAmqpIsRefused(t *testing.T) {
+	raw := []byte(`{"module":"old-broker","version":"1","provides":[{"name":"amqp","scope":"mesh"}]}`)
+	_, err := ParseManifest(raw)
+	if err == nil || !strings.Contains(err.Error(), `provides "amqp", which is not a provision`) {
+		t.Fatalf("a module providing amqp was not refused, or not for the reason: %v", err)
+	}
+}
+
+func TestAManifestRequiringAmqpIsRefused(t *testing.T) {
+	raw := []byte(`{"module":"forwarder","version":"1","requires":["amqp"]}`)
+	_, err := ParseManifest(raw)
+	if err == nil || !strings.Contains(err.Error(), `requires "amqp", which is not a provision`) {
+		t.Fatalf("a module requiring amqp was not refused, or not for the reason: %v", err)
+	}
+}
+
+// And the catalogue as checked out beside this repository names it nowhere — the three modules that
+// did are removed under design 28 task 5.4, not converted.
+func TestNoCatalogueManifestNamesAmqp(t *testing.T) {
+	modules, err := filepath.Glob("../../../mesh-catalog/modules/*/module.json")
+	if err != nil || len(modules) == 0 {
+		t.Skip("the catalogue is not checked out beside this repository")
+	}
+	for _, path := range modules {
+		raw, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if strings.Contains(string(raw), `"amqp"`) {
+			t.Errorf("%s names amqp, which is not a provision (novox/hq ADR 0131)",
+				filepath.Base(filepath.Dir(path)))
+		}
+	}
+}
@@ -0,0 +1,87 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// The mesh's bus is one per mesh, read from the catalogue beside this checkout.
+//
+// **This is step 2's claim, and it is checked here rather than in a bed** (novox/hq ADR 0116):
+// adoption puts the NATS server into the `mesh-broker` seat on a mesh that is already running,
+// and the property that matters is that a second one anywhere is refused *when it is assigned*,
+// not discovered later as two servers holding different halves of the mesh's traffic. A second
+// bus is not a degraded mesh; it is two meshes that both believe they are the one.
+func TestASecondMeshBusAnywhereIsRefusedByName(t *testing.T) {
+	nats := catalogueManifest(t, "nats")
+
+	if _, err := Resolve(shelf(nats), []string{"nats"}, workstation(), World{}); err != nil {
+		t.Fatalf("the bus alone does not resolve: %v", err)
+	}
+
+	elsewhere := World{Held: []Held{{Claim: "mesh-broker", Scope: ScopeMesh,
+		Node: "anchor", Module: "nats"}}}
+	other := workstation()
+	other.Name = "laptop"
+	_, err := Resolve(shelf(nats), []string{"nats"}, other, elsewhere)
+	if err == nil {
+		t.Fatal("a second bus was accepted on another machine")
+	}
+	if !strings.Contains(err.Error(), "mesh-broker") || !strings.Contains(err.Error(), "one per mesh") {
+		t.Fatalf("refused without naming the seat: %v", err)
+	}
+}
+
+// The seat is the server's role, not the product's name (novox/hq ADR 0079). A different
+// implementation of the bus claims the same seat, and the mesh refuses it for the same reason —
+// which is the property that lets the bus be replaced at all.
+func TestTheSeatRefusesADifferentBusToo(t *testing.T) {
+	nats := catalogueManifest(t, "nats")
+	held := World{Held: []Held{{Claim: "mesh-broker", Scope: ScopeMesh,
+		Node: "anchor", Module: "some-other-broker"}}}
+	other := workstation()
+	other.Name = "laptop"
+	if _, err := Resolve(shelf(nats), []string{"nats"}, other, held); err == nil {
+		t.Fatal("the seat admitted a second holder because the module's name differed")
+	}
+}
+
+// The old broker is gone from the catalogue (novox/hq ADR 0131, design 28 task 5.4), so it is no
+// longer a fixture here. That two eligible holders stand beside each other with one on record is
+// pinned in holdings_test.go against manifests this package owns.
+
+// **A seat and the interface it delivers are different names, and renaming one must not rename
+// the other** (novox/hq ADR 0118). This nearly went wrong: the seats were renamed to the `mesh-*`
+// prefix, and a blanket search-and-replace also renamed `npm-package-registry` and `git` where
+// they are *provisions* — which a consumer requires and a provider offers. The tests failed with
+// "the package registry is served on <nil>", which does not say "you renamed an interface".
+func TestRenamingASeatDidNotRenameTheInterfaceItDelivers(t *testing.T) {
+	for _, pair := range []struct{ seat, delivers string }{
+		{"git", "git"},
+		{"npm-package-registry", "npm-package-registry"},
+		{"the-artifact-store", "artifact-store"},
+		{"mesh-store", "postgres-database"},
+		{"mesh-broker", "mesh-bus"},
+	} {
+		s, known := SeatNamed(pair.seat)
+		if !known {
+			t.Fatalf("%q is not a seat", pair.seat)
+		}
+		if s.Delivers != pair.delivers {
+			t.Errorf("the %s seat delivers %q, expected %q — renaming the seat moved the "+
+				"interface with it, and every consumer requiring it would stop resolving",
+				pair.seat, s.Delivers, pair.delivers)
+		}
+		// **Three of these deliberately share a name with what they deliver**, and that is not an
+		// incomplete rename. Renaming a seat that delivers a provision cascades to every consumer
+		// requiring it, with a mesh-wide window where a holder stops resolving mid-flight — so the
+		// trunk deferred exactly those three (novox/hq ADR 0121) while renaming the node-scoped ones.
+		// What this test is for is the other direction: that renaming a seat never moves the
+		// interface, which once produced "the package registry is served on <nil>".
+	}
+}
+
+// A manifest written against an old seat name is told what it became rather than refused as
+// unknown. **That map is the controller's store now, not this package** (novox/hq ADR 0122): a
+// rename is a row, so the courtesy survives a rename nobody recompiled for. Checked where the
+// table is read, not here, where there is no longer a hardcoded list to check against.
@@ -97,6 +97,29 @@ type Rendering struct {
 	// compose it a second time.
 	Suffix string

+	// BusUsers is the mesh's composed user list, for the module holding `mesh-broker`. Empty on
+	// every other node, and on this one until the controller has composed it.
+	//
+	// **Only the users, never the server's own settings**: those are the module's, in its image and
+	// its mounts (Manifest.BusUsers).
+	BusUsers string
+	// BusMembership is this machine's membership for the bus the mesh is moving to, sealed to it
+	// (design 28, task 5.2). Empty for a machine not being moved. Written as a file the host reads
+	// after the declaration has applied, so the bus it names is standing before the machine leaves
+	// the one it is on.
+	BusMembership string
+
+	// MeshRange is the private network's CIDR (the range node addresses are allocated from), for a
+	// module that must name the whole mesh rather than one machine — an intrusion filter that must
+	// never ban a tunnel peer, say. A per-mesh value the module cannot know, so it is carried here
+	// and offered as ${machine:mesh-range}, the same way one machine's address is.
+	MeshRange string
+
+	// Accounts is each machine's operator account, by the same internal name Names uses (novox/hq
+	// to-be 29). What an ssh Host block's `User` line is composed from; empty for a machine no
+	// operator account is known on.
+	Accounts map[string]string
+
 	// Kept is every operator-sealed secret in the mesh, for a module that `keeps` them. Nil when
 	// nothing on this node keeps them, or the mesh has no operator key.
 	Kept *KeptExport
@@ -220,9 +243,23 @@ func (r Resolution) Compose(with Rendering) (Composed, error) {
 	if err != nil {
 		return Composed{}, err
 	}
+	if with.BusMembership != "" {
+		// The machine's own, not any module's: how it reaches the mesh from now on. Sealed like a
+		// secret and placed where the host looks for exactly this (design 28, task 5.2).
+		resources = append(resources, map[string]any{
+			"id": BusMembershipID(), "type": "file", "path": BusMembershipPath,
+			"sealed": with.BusMembership, "mode": "0600",
+		})
+	}
 	return Composed{Resources: resources, Owner: owner}, nil
 }

+// BusMembershipID names the resource carrying a machine's membership for the new bus, and
+// BusMembershipPath is where the host reads it — the same constant on both sides.
+func BusMembershipID() string { return "bus-membership" }
+
+const BusMembershipPath = "/var/lib/mesh/membership-next.json"
+
 func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[string]any, error) {
 	// Every manifest is placed first (novox/hq ADR 0112): the maps naming where its bindings,
 	// credentials and contributions land are resolved against this node's directories, so every
@@ -339,6 +376,12 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 				"content": filtering, "mode": "0600",
 			})
 		}
+		// The node's fail2ban jails, composed from every module it runs (novox/hq to-be 31), written
+		// where the intrusion-prevention holder owns them. Like the rule set above: gathered from all
+		// modules, written by the one that holds the role.
+		if j := m.Jailing; j != nil {
+			first = append(first, jailsInto(r.Modules, j)...)
+		}
 		if c := m.Certificate; c != nil {
 			if with.Certificate == "" {
 				// Asked for and not issued. Refused rather than skipped: a module that serves TLS
@@ -359,6 +402,35 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 				})
 			}
 		}
+		if m.BusUsers != "" {
+			// **The claim authorises it, not the field.** This file holds every user's password
+			// hash, so a module that could ask for it could read every credential on the bus.
+			// Checked from this manifest alone, which is the cheapest check there is: whether some
+			// other module also claims the seat is resolution's business elsewhere, and one holder
+			// mesh-wide is already guaranteed.
+			if !m.ClaimsSeat("mesh-broker") {
+				return nil, fmt.Errorf(
+					"%s asks for the mesh's user list and does not claim mesh-broker. That file "+
+						"holds every user's password hash, so the seat is what authorises it",
+					m.Module)
+			}
+			if with.BusUsers == "" {
+				// Asked for and not composed. Refused rather than skipped, for the reason a
+				// certificate is: a bus with no user list refuses every connection in the mesh, and
+				// an empty file would look like a configuration problem on the machine.
+				return nil, fmt.Errorf(
+					"%s holds mesh-broker and the mesh composed no user list, so the bus would "+
+						"refuse every connection", m.Module)
+			}
+			first = append(first, map[string]any{
+				"id": BusUsersID(), "type": "file", "path": m.BusUsers,
+				"content": with.BusUsers,
+				// Readable by the server and nothing else. Hashes rather than passwords, so this is
+				// not a set of working credentials — but a list of every user in the mesh is worth
+				// keeping to the one process that needs it.
+				"mode": "0600",
+			})
+		}
 		for _, name := range sortedKeys(m.OwnSecrets) {
 			sealed := with.Needed[m.Module][name]
 			if sealed == "" {
@@ -545,7 +617,7 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 		// (novox/hq ADR 0112) — resolved once per module, named by ${dir:…} from any resource.
 		dirs := dirsFor(m, with)
 		// And the machine underneath, which no binding of its own can tell it.
-		thisMachine := machineFacts(r, with.Names)
+		thisMachine := machineFacts(r, with.Names, with.MeshRange)

 		// Which of this module's files carry a secret, for the rule that a container may not read
 		// one of them as its environment without saying so (ADR 0086, issue 041).
@@ -644,7 +716,7 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 		// plane's; making a name resolve is the module's software. Emitted as ordinary files under
 		// this module's name, so they are applied, reported and removed exactly as anything else
 		// it declares.
-		given, err := FactsInto(m, r, with.Names, with.Machines, with.Suffix)
+		given, err := FactsInto(m, r, with.Names, with.Machines, with.Accounts, with.Suffix)
 		if err != nil {
 			return nil, err
 		}
@@ -0,0 +1,80 @@
+package catalogue
+
+import "testing"
+
+// The mesh's user list reaches the module holding the bus, and nothing else.
+//
+// Three refusals and one delivery, because each of the refusals would be silent in a different way:
+// a module that asked and was given it could read every credential on the bus; a bus given an empty
+// file refuses every connection in the mesh and looks like a machine problem; and a bus that never
+// asked gets nothing rather than a file it does not read.
+func TestTheMeshsUserListGoesOnlyToTheModuleHoldingTheBus(t *testing.T) {
+	theBus := func() Manifest {
+		return Manifest{
+			Module: "nats", Version: "1",
+			Claims:    []Claim{{Name: "mesh-broker", Scope: ScopeMesh}},
+			BusUsers:  "/var/lib/nats-module/conf/accounts.conf",
+			Resources: []map[string]any{},
+		}
+	}
+
+	on := func(t *testing.T, m Manifest, with Rendering) ([]map[string]any, error) {
+		t.Helper()
+		return Resolution{Node: "anchor", Modules: []Manifest{m}}.Declaration(with)
+	}
+
+	t.Run("the holder is given it", func(t *testing.T) {
+		resources, err := on(t, theBus(), Rendering{BusUsers: "accounts { MESH { users = [] } }"})
+		if err != nil {
+			t.Fatal(err)
+		}
+		// Prefixed with the module it came from, like every resource: two modules may reasonably
+		// both call something "config", and without the prefix the second would silently replace
+		// the first.
+		var found map[string]any
+		for _, r := range resources {
+			if r["id"] == "nats."+BusUsersID() {
+				found = r
+			}
+		}
+		if found == nil {
+			t.Fatalf("the bus was given no user list: %+v", resources)
+		}
+		if found["path"] != "/var/lib/nats-module/conf/accounts.conf" {
+			t.Errorf("written to %v rather than where the module asked", found["path"])
+		}
+		if found["mode"] != "0600" {
+			t.Errorf("mode %v: a list of every user in the mesh belongs to the one process that "+
+				"needs it", found["mode"])
+		}
+	})
+
+	t.Run("a module that does not claim the seat is refused", func(t *testing.T) {
+		m := theBus()
+		m.Claims = nil
+		if _, err := on(t, m, Rendering{BusUsers: "accounts {}"}); err == nil {
+			t.Fatal("a module that claims nothing was handed every user's password hash")
+		}
+	})
+
+	t.Run("the holder with nothing composed is refused", func(t *testing.T) {
+		if _, err := on(t, theBus(), Rendering{}); err == nil {
+			t.Fatal("the bus was given an empty user list, so it would refuse every connection in " +
+				"the mesh and look like a machine problem")
+		}
+	})
+
+	t.Run("a module that did not ask gets nothing", func(t *testing.T) {
+		m := theBus()
+		m.BusUsers = ""
+		resources, err := on(t, m, Rendering{BusUsers: "accounts {}"})
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, r := range resources {
+			if r["id"] == "nats."+BusUsersID() {
+				t.Fatal("a module that asked for no user list was given one")
+			}
+		}
+	})
+}
@@ -0,0 +1,161 @@
+package catalogue
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// What a module may call an event, and what a consumer may ask for.
+//
+// A module names an event **locally**: `order.placed`, not a subject and not a routing key
+// (design 29 §1). A consumer names the emitter and the event: `billing.order.placed`. The mesh
+// derives the subject from those, so reorganising the subject space leaves every manifest correct.
+//
+// **Nothing checked this until every manifest in the catalogue was wrong the same way**
+// (novox/hq 04-ISSUES/127). All thirty-seven kept the old bus's routing key —
+// `module.<module>.<verb>` — which the derivation read as "a module called `module`", so every
+// cross-module subscription in the mesh pointed at a namespace nobody publishes to. Nothing failed:
+// the services started and none of them reacted. The documentation on these fields taught the old
+// form too, which is why the drift was uniform rather than scattered.
+
+// eventName is one name in a local event: lower-case, and no wildcard.
+var eventName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*$`)
+
+// The wildcards a consumer may use, spelled the mesh's way and derived to whatever the transport
+// spells them as.
+//
+// **A manifest holds no transport token**, which is the whole point of naming locally: the bus the
+// mesh runs on today spells these `*` and `#`, and the one being built spells them `*` and `>`. A
+// manifest that said either would be a manifest that stopped being true when the wire changed.
+const (
+	// OneName stands for exactly one name.
+	OneName = "*"
+	// TheRest stands for one or more names, and may only come last.
+	TheRest = "**"
+)
+
+// EventProblems is what is wrong with a manifest's events.
+//
+// Refused at registration, because the alternative is a module that installs, starts, connects and
+// reacts to nothing — and every log line says it is fine.
+func EventProblems(m Manifest) []string {
+	var problems []string
+
+	for _, e := range m.Emits {
+		if was, stale := staleEventForm(e, m.Module); stale {
+			problems = append(problems, fmt.Sprintf(
+				"%s emits %q, which is the old bus's routing key. An event is named locally now, so "+
+					"write %q — the mesh derives the subject (novox/hq design 29 §1)",
+				m.Module, was, strings.TrimPrefix(was, "module."+m.Module+".")))
+			continue
+		}
+		if strings.HasPrefix(e, "module.") {
+			problems = append(problems, fmt.Sprintf(
+				"%s emits %q: `module.` is reserved, because it is how the old bus spelled a "+
+					"routing key and an event named that way derives into a namespace nobody owns",
+				m.Module, e))
+			continue
+		}
+		if err := localName(e); err != nil {
+			problems = append(problems, fmt.Sprintf("%s emits %q: %v", m.Module, e, err))
+			continue
+		}
+		// **Its own name, never another's.** The bus enforces that a namespace belongs to the module
+		// it is named for, so an event named for somebody else cannot be published at all. If the
+		// event is about a role rather than about this module, it belongs on the seat: a name that
+		// is stable across whoever fills it (04-ISSUES/127).
+		if first, _, split := strings.Cut(e, "."); split && isAModuleNameOtherThan(first, m.Module) {
+			problems = append(problems, fmt.Sprintf(
+				"%s emits %q, which reads as another module's event. A module publishes under its "+
+					"own name only. If this is about a role rather than about %s, declare it on that "+
+					"seat, where the name survives the holder changing",
+				m.Module, e, m.Module))
+		}
+	}
+
+	for _, c := range m.Consumes {
+		if strings.HasPrefix(c, "module.") {
+			problems = append(problems, fmt.Sprintf(
+				"%s consumes %q, which is the old bus's pattern. A consumed event names its emitter "+
+					"and the event: write %q", m.Module, c, strings.TrimPrefix(c, "module.")))
+			continue
+		}
+		if c == "#" {
+			problems = append(problems, fmt.Sprintf(
+				"%s consumes %q, which is the old bus's wildcard for everything. Write %q",
+				m.Module, c, TheRest))
+			continue
+		}
+		if err := consumePattern(c); err != nil {
+			problems = append(problems, fmt.Sprintf("%s consumes %q: %v", m.Module, c, err))
+		}
+	}
+	return problems
+}
+
+// staleEventForm says an emitted name is this module's own old routing key, and what it was.
+func staleEventForm(event, module string) (string, bool) {
+	return event, module != "" && strings.HasPrefix(event, "module."+module+".")
+}
+
+// isAModuleNameOtherThan says a first token names some module of this mesh that is not this one.
+//
+// Only the mesh's own seats and the catalogue could answer this properly, and neither is reachable
+// from a parser given one manifest. So this catches the case that actually happened — a name that
+// is a *provision* the mesh defines, which is where "another module's event" comes from in practice
+// — and the whole-catalogue check catches the rest.
+func isAModuleNameOtherThan(first, module string) bool {
+	if first == module || first == "" {
+		return false
+	}
+	if _, isASeat := SeatNamed(first); isASeat {
+		return true
+	}
+	if _, isASeat := SeatDelivering(first); isASeat {
+		return true
+	}
+	return false
+}
+
+// localName checks one event name: dot-separated names, no wildcards, nothing else.
+func localName(event string) error {
+	if event == "" {
+		return fmt.Errorf("an event needs a name")
+	}
+	for _, part := range strings.Split(event, ".") {
+		if part == OneName || part == TheRest {
+			return fmt.Errorf("an emitted event names one event, so it carries no wildcard")
+		}
+		if !eventName.MatchString(part) {
+			return fmt.Errorf("%q is not a usable name: lower-case letters, digits and dashes", part)
+		}
+	}
+	return nil
+}
+
+// consumePattern checks a consumed pattern: the emitter, then the event, with wildcards.
+func consumePattern(pattern string) error {
+	if pattern == "" {
+		return fmt.Errorf("a consumed event needs an emitter and an event")
+	}
+	parts := strings.Split(pattern, ".")
+	for i, part := range parts {
+		switch {
+		case part == TheRest:
+			if i != len(parts)-1 {
+				return fmt.Errorf("%q stands for the rest of a name, so nothing may follow it", TheRest)
+			}
+		case part == OneName:
+		case !eventName.MatchString(part):
+			return fmt.Errorf("%q is not a usable name: lower-case letters, digits and dashes", part)
+		}
+	}
+	// `**` alone is every event from every module, which the audit logger wants and says plainly.
+	if len(parts) == 1 && parts[0] != TheRest {
+		return fmt.Errorf(
+			"%q names an emitter and no event. Write <emitter>.<event>, or %q for every event",
+			pattern, TheRest)
+	}
+	return nil
+}
@@ -1,184 +0,0 @@
-package catalogue
-
-import (
-	"fmt"
-	"sort"
-	"strings"
-)
-
-// What only the mesh knows, written where a module asks for it.
-//
-// **The graph is the control plane's; using it is the module's.** The mesh knows which machines
-// exist, what they are called, and where they are. Turning that into a name that resolves is
-// somebody's software, and which software is a choice the mesh should not be making.
-//
-// This replaced three modules — names, a resolver's data, and the private network's own
-// configuration — that existed only because computed output needed somewhere to live. They ran no
-// software and could not be swapped for anything, which is the test of whether something is a
-// module at all (novox/hq ADR 0040).
-
-const (
-	// FactNodeNames is every machine's name and address, as a hosts file.
-	//
-	// Exact names only: `homer` and `homer.internal` resolve to homer. Anything *under* a machine
-	// is a wildcard, which a hosts file cannot express — that is FactNodeZones.
-	FactNodeNames = "node-names"
-
-	// FactNodeZones is every machine as a wildcard: `*.homer.internal` is homer.
-	//
-	// Written in the form a resolver reads. A machine's own name and everything under it are one
-	// fact — if homer is at an address, so is anything homer serves.
-	FactNodeZones = "node-zones"
-)
-
-// facts is every fact the mesh computes, and what writes it.
-//
-// **A closed list.** A module asking for a fact the mesh does not have is asking for a file nobody
-// will write, and finding that out on a machine — as a daemon that starts, reads nothing, and
-// answers no queries — is worse than being told where the manifest is.
-// A fact is written from the names it is about. `every` is every name the mesh serves — machines
-// and the names it was told to route; `machines` is only the machines. A fact takes the set it is
-// true of, and the two must not be confused (novox/hq 04-ISSUES/111).
-var facts = map[string]func(r Resolution, every, machines map[string]string, suffix string) string{
-	FactNodeNames: func(r Resolution, every, _ map[string]string, suffix string) string {
-		return nodeNames(r, every, suffix)
-	},
-	FactNodeZones: func(r Resolution, _, machines map[string]string, suffix string) string {
-		return nodeZones(r, machines, suffix)
-	},
-}
-
-// FactsInto renders the facts a module asked for, as files it will be given.
-//
-// The module owns everything after the file exists: loading it, restarting on it, what a resolver
-// does with it. This only puts it there.
-func FactsInto(m Manifest, r Resolution, addresses, machines map[string]string, suffix string) ([]map[string]any, error) {
-	if len(m.Facts) == 0 {
-		return nil, nil
-	}
-	names := make([]string, 0, len(m.Facts))
-	for name := range m.Facts {
-		names = append(names, name)
-	}
-	sort.Strings(names)
-
-	out := make([]map[string]any, 0, len(names))
-	for _, name := range names {
-		write, known := facts[name]
-		if !known {
-			return nil, fmt.Errorf(
-				"%s asks the mesh for %q, which it does not compute. It has %s",
-				m.Module, name, spokenFacts())
-		}
-		path := m.Facts[name]
-		if !strings.HasPrefix(path, "/") {
-			return nil, fmt.Errorf(
-				"%s asks for %q at %q, which is not an absolute path", m.Module, name, path)
-		}
-		out = append(out, map[string]any{
-			"id": "fact-" + name, "type": "file", "path": path, "mode": "0644",
-			"content": write(r, addresses, machines, suffix),
-		})
-	}
-	return out, nil
-}
-
-// spokenFacts lists them, so a refusal says what would have worked.
-func spokenFacts() string {
-	names := make([]string, 0, len(facts))
-	for name := range facts {
-		names = append(names, name)
-	}
-	sort.Strings(names)
-	return strings.Join(names, ", ")
-}
-
-// nodeNames is every machine's name and address, as a hosts file.
-//
-// **A machine with no address is left out.** The mesh has a record for it — somebody added it —
-// and does not yet know where it is, which is the ordinary state between adding a machine and it
-// joining. Writing the name anyway would give a name that resolves to nothing, and a connection to
-// that hangs; leaving it out fails at once and says the name is unknown.
-func nodeNames(r Resolution, addresses map[string]string, suffix string) string {
-	var b strings.Builder
-	b.WriteString("# Generated by the mesh. Do not edit — this file is replaced whenever a machine\n")
-	b.WriteString("# joins or leaves, and an edit would survive until then and vanish.\n\n")
-	// The floor every Linux expects, and which removing would break things that have nothing to do
-	// with the mesh.
-	b.WriteString("127.0.0.1\tlocalhost\n")
-	b.WriteString("::1\t\tlocalhost ip6-localhost ip6-loopback\n")
-	if r.Node != "" {
-		fmt.Fprintf(&b, "127.0.1.1\t%s\n", r.Node)
-	}
-	b.WriteString("\n")
-	for _, name := range sortedNames(addresses) {
-		at := addresses[name]
-		internal, bare := meshName(name, suffix)
-		// Its mesh name resolves to its address on the private network rather than to loopback,
-		// so a service binding the name it was given stays reachable from everywhere else.
-		fmt.Fprintf(&b, "%s\t%s\t%s", at, internal, bare)
-		if bare == r.Node {
-			b.WriteString("\t# this machine")
-		}
-		b.WriteString("\n")
-	}
-	return b.String()
-}
-
-// nodeZones is every machine as a wildcard, in the form a resolver reads.
-//
-// `*.homer.internal` is homer, which is the whole rule: if homer is at an address, so is anything
-// homer serves. A module wanting this runs the resolver; the mesh only says what is true.
-//
-// **And the suffix itself, as a local domain.** A resolver that forwards what it cannot answer
-// would otherwise send a mesh name it does not know — a machine that left, a typo — to a public
-// resolver, which is a leak of the mesh's names for no answer. `local=` keeps everything under the
-// suffix here: answered from the lines below or refused. Written in this file rather than in the
-// resolver's own configuration because the suffix is the mesh's choice (the operator may have
-// picked another) and this file is the one place the mesh writes what it chose.
-func nodeZones(_ Resolution, addresses map[string]string, suffix string) string {
-	var b strings.Builder
-	b.WriteString("# Generated by the mesh. Do not edit — this file is replaced whenever a machine\n")
-	b.WriteString("# joins or leaves, and an edit would survive until then and vanish.\n\n")
-	fmt.Fprintf(&b, "local=/%s/\n", strings.TrimPrefix(suffixOr(suffix), "."))
-	for _, name := range sortedNames(addresses) {
-		internal, _ := meshName(name, suffix)
-		fmt.Fprintf(&b, "address=/%s/%s\n", internal, addresses[name])
-	}
-	return b.String()
-}
-
-// meshName is a machine's internal name and its bare one, from either. The control plane keys
-// the names it hands a resolution by the internal name (`homer.internal`), the same map a
-// container gets as its hosts; a caller that keys by the bare name gets the same answer. The
-// suffix is the one the control plane composed those names with, handed down rather than written
-// here a second time — the alternative was `homer.internal.internal` on every machine.
-func meshName(name, suffix string) (internal, bare string) {
-	dotted := "." + strings.TrimPrefix(suffixOr(suffix), ".")
-	if strings.HasSuffix(name, dotted) {
-		return name, strings.TrimSuffix(name, dotted)
-	}
-	return name + dotted, name
-}
-
-// suffixOr is the suffix given, or the one the mesh composes names with when none was handed down.
-// The one place the default is written in this file, so a fact and a name cannot disagree about it.
-func suffixOr(suffix string) string {
-	if suffix == "" {
-		return "internal"
-	}
-	return suffix
-}
-
-func sortedNames(addresses map[string]string) []string {
-	out := make([]string, 0, len(addresses))
-	for name, at := range addresses {
-		// See nodeNames: a machine the mesh cannot place is left out rather than named at nothing.
-		if at == "" {
-			continue
-		}
-		out = append(out, name)
-	}
-	sort.Strings(out)
-	return out
-}
@@ -1,188 +0,0 @@
-package catalogue
-
-import (
-	"strings"
-	"testing"
-)
-
-// Keyed by the internal name, as the control plane hands them (issue 079).
-var threeMachines = map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2", "bart.internal": ""}
-
-// **`*.homer.internal` is homer. That is the whole rule.** And the suffix itself is local: a
-// resolver that forwards what it cannot answer must not send a mesh name it does not know — a
-// machine that left, a typo — to a public resolver (hal dnsmasq-app conversion, novox/hq
-// 08-connectivity).
-func TestEveryMachineIsAWildcardUnderItsOwnName(t *testing.T) {
-	out := nodeZones(Resolution{Node: "homer"}, threeMachines, "")
-	for _, want := range []string{
-		"local=/internal/",
-		"address=/homer.internal/10.42.0.1",
-		"address=/marge.internal/10.42.0.2",
-	} {
-		if !strings.Contains(out, want) {
-			t.Fatalf("missing %q:\n%s", want, out)
-		}
-	}
-}
-
-// A machine the mesh has a record for and cannot place is left out of both.
-//
-// **Not an oversight — the alternative is worse.** A name written with no address resolves to
-// nothing, and a connection to that hangs. Leaving it out fails at once and says the name is
-// unknown, which is a thing somebody can act on.
-func TestAMachineWithNoAddressIsNotNamed(t *testing.T) {
-	for _, out := range []string{
-		nodeNames(Resolution{Node: "homer"}, threeMachines, ""),
-		nodeZones(Resolution{Node: "homer"}, threeMachines, ""),
-	} {
-		if strings.Contains(out, "bart") {
-			t.Fatalf("a machine with no address was named, so its name resolves to nothing:\n%s", out)
-		}
-	}
-}
-
-// A machine's own mesh name points at its address on the private network, not at loopback — or a
-// service binding the name it was given is unreachable from everywhere else.
-func TestAMachinesOwnNameIsItsMeshAddress(t *testing.T) {
-	out := nodeNames(Resolution{Node: "homer"}, threeMachines, "")
-	var line string
-	for _, l := range strings.Split(out, "\n") {
-		if strings.Contains(l, "homer.internal") {
-			line = l
-		}
-	}
-	if !strings.HasPrefix(line, "10.42.0.1") {
-		t.Fatalf("a machine's own mesh name is not its mesh address: %q", line)
-	}
-	// And the loopback floor is still there, or things with nothing to do with the mesh break.
-	if !strings.Contains(out, "127.0.0.1\tlocalhost") {
-		t.Fatalf("the loopback floor was removed:\n%s", out)
-	}
-}
-
-// A module says where it wants a fact, and is given a file.
-func TestAModuleIsGivenTheFactsItAskedFor(t *testing.T) {
-	m := Manifest{Module: "dnsmasq", Facts: map[string]string{FactNodeZones: "/etc/mesh/zones.conf"}}
-	given, err := FactsInto(m, Resolution{Node: "homer"}, threeMachines, threeMachines, "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	if len(given) != 1 {
-		t.Fatalf("expected one file, got %d", len(given))
-	}
-	if given[0]["path"] != "/etc/mesh/zones.conf" || given[0]["type"] != "file" {
-		t.Fatalf("not written where it was asked for: %v", given[0])
-	}
-	if !strings.Contains(given[0]["content"].(string), "homer.internal") {
-		t.Fatalf("the file does not hold the fact: %v", given[0]["content"])
-	}
-}
-
-// **Asking for a fact the mesh does not have is refused here, not on a machine.** A daemon that
-// starts, reads a file nobody wrote, and answers no queries is a much worse way to find out.
-func TestAskingForAFactTheMeshDoesNotHaveIsRefused(t *testing.T) {
-	m := Manifest{Module: "dnsmasq", Facts: map[string]string{"the-weather": "/etc/weather"}}
-	_, err := FactsInto(m, Resolution{}, nil, nil, "")
-	if err == nil {
-		t.Fatal("a module asked for something nobody computes and was given nothing, silently")
-	}
-	for _, known := range []string{FactNodeNames, FactNodeZones} {
-		if !strings.Contains(err.Error(), known) {
-			t.Fatalf("the refusal does not say what would have worked: %v", err)
-		}
-	}
-}
-
-// And a relative path is refused, or a module decides where the mesh writes on a machine.
-func TestAFactMustBeAskedForAtAnAbsolutePath(t *testing.T) {
-	m := Manifest{Module: "dnsmasq", Facts: map[string]string{FactNodeNames: "etc/hosts"}}
-	if _, err := FactsInto(m, Resolution{}, nil, nil, ""); err == nil {
-		t.Fatal("a relative path was accepted")
-	}
-}
-
-// **The names the control plane hands a resolution are already internal names** — `homer.internal`,
-// the same map every container gets as its hosts. Appending the suffix again wrote
-// `homer.internal.internal` into every hosts file and every resolver's zones, and the large mesh
-// bed's name test was the first to read it back. Either key gives the same files.
-func TestNamesKeyedByInternalNameAreNotSuffixedTwice(t *testing.T) {
-	internal := map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2"}
-	bare := map[string]string{"homer": "10.42.0.1", "marge": "10.42.0.2"}
-	if a, b := nodeZones(Resolution{Node: "homer"}, internal, ""), nodeZones(Resolution{Node: "homer"}, bare, ""); a != b {
-		t.Fatalf("the zones differ by how the names were keyed:\n%s\n---\n%s", a, b)
-	}
-	if a, b := nodeNames(Resolution{Node: "homer"}, internal, ""), nodeNames(Resolution{Node: "homer"}, bare, ""); a != b {
-		t.Fatalf("the hosts differ by how the names were keyed:\n%s\n---\n%s", a, b)
-	}
-	zones := nodeZones(Resolution{Node: "homer"}, internal, "")
-	if strings.Contains(zones, "internal.internal") || !strings.Contains(zones, "address=/homer.internal/10.42.0.1") {
-		t.Fatalf("the zones carry a doubled suffix or miss the name:\n%s", zones)
-	}
-	hosts := nodeNames(Resolution{Node: "homer"}, internal, "")
-	if !strings.Contains(hosts, "10.42.0.1\thomer.internal\thomer\t# this machine") {
-		t.Fatalf("the hosts line for the machine itself is not name, bare name and the mark:\n%s", hosts)
-	}
-}
-
-// The suffix the control plane composed the names with is the one the facts write — an operator
-// who chose another does not get `.internal` appended to it.
-func TestTheFactsWriteTheSuffixTheNamesWereComposedWith(t *testing.T) {
-	names := map[string]string{"homer.lan": "10.42.0.1"}
-	zones := nodeZones(Resolution{Node: "homer"}, names, "lan")
-	if !strings.Contains(zones, "address=/homer.lan/10.42.0.1") || strings.Contains(zones, "internal") {
-		t.Fatalf("the zones do not carry the operator's suffix as given:\n%s", zones)
-	}
-	if !strings.Contains(zones, "local=/lan/") {
-		t.Fatalf("the local domain is not the operator's suffix, so its names would leak upstream:\n%s", zones)
-	}
-	hosts := nodeNames(Resolution{Node: "homer"}, names, "lan")
-	if !strings.Contains(hosts, "10.42.0.1\thomer.lan\thomer\t# this machine") {
-		t.Fatalf("the hosts line does not carry the operator's suffix as given:\n%s", hosts)
-	}
-}
-
-// novox/hq 04-ISSUES/111: the map the control plane hands a resolution holds every name the mesh
-// serves — the machines, and the names it was told to route to whichever machine serves them. A
-// container's hosts wants all of it. A resolver's zones want only the machines: told the mesh's
-// suffix is its own, it answers authoritatively for everything under it and forwards nothing, so a
-// routed name written there with the suffix appended is a name nobody will ever ask for, standing
-// beside the machines and looking as real.
-func TestTheResolverIsToldTheMachinesAndNotTheNamesTheMeshMerelyServes(t *testing.T) {
-	machines := map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2"}
-	every := map[string]string{
-		"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2",
-		"drive.example.test": "10.42.0.1", "git.example.test": "10.42.0.2",
-	}
-	m := Manifest{Module: "resolver", Facts: map[string]string{
-		FactNodeZones: "/etc/zones.conf", FactNodeNames: "/etc/hosts",
-	}}
-	given, err := FactsInto(m, Resolution{Node: "homer"}, every, machines, "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	by := map[string]string{}
-	for _, f := range given {
-		by[f["path"].(string)] = f["content"].(string)
-	}
-
-	zones := by["/etc/zones.conf"]
-	for _, machine := range []string{"address=/homer.internal/10.42.0.1", "address=/marge.internal/10.42.0.2"} {
-		if !strings.Contains(zones, machine) {
-			t.Fatalf("the resolver was not told %q:\n%s", machine, zones)
-		}
-	}
-	for _, served := range []string{"drive.example.test", "git.example.test"} {
-		if strings.Contains(zones, served) {
-			t.Fatalf("the resolver was told %q, a name the mesh serves rather than a machine:\n%s", served, zones)
-		}
-	}
-
-	// And the hosts file is the other way about: every name, so a container reaching a routed name
-	// finds the machine serving it.
-	hosts := by["/etc/hosts"]
-	for _, name := range []string{"homer.internal", "drive.example.test", "git.example.test"} {
-		if !strings.Contains(hosts, name) {
-			t.Fatalf("a container would not resolve %q from its hosts:\n%s", name, hosts)
-		}
-	}
-}
@@ -28,8 +28,10 @@ func TestTheStoreAndTheBrokerSayWhatTheMeshGuards(t *testing.T) {
 	if got := catalogueManifest(t, "postgres").Guards; !reflect.DeepEqual(got, []int{5432}) {
 		t.Errorf("postgres guards %v; the store's port must be refused from outside", got)
 	}
-	if got := catalogueManifest(t, "lavinmq").Guards; !reflect.DeepEqual(got, []int{15672}) {
-		t.Errorf("lavinmq guards %v; the management port must be refused from outside", got)
+	// The bus's monitoring port, not its client port: a node reaches the bus, nobody outside
+	// reads its state (novox/hq ADR 0131 — the broker that guarded 15672 has left the catalogue).
+	if got := catalogueManifest(t, "nats").Guards; !reflect.DeepEqual(got, []int{8222}) {
+		t.Errorf("nats guards %v; the monitoring port must be refused from outside", got)
 	}
 }

@@ -0,0 +1,160 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// **A seat's holder on record settles who holds it, and lets the next holder stand beside the
+// current one** (novox/hq ADR 0131, design 28 task 5.3). Until the record existed, two assignments
+// whose modules both claimed a seat were refused outright — which left no way to hand a seat over
+// without a moment where nobody held it, and the control plane finds its own bus through one of
+// these seats. That moment was the outage of 2026-09-27.
+
+func busSeatDelivering(t *testing.T, delivers string) {
+	t.Helper()
+	was := Seats()
+	t.Cleanup(func() { UseSeats(was) })
+	UseSeats([]Seat{{Name: "mesh-broker", Scope: ScopeMesh, Delivers: delivers, Decision: "test"}})
+}
+
+func oldBroker() Manifest {
+	return Manifest{Module: "old-broker", Provides: []Offer{{Name: "mesh-bus", Scope: ScopeMesh}},
+		Claims: []Claim{{Name: "mesh-broker", Scope: ScopeMesh}}}
+}
+
+func newBroker() Manifest {
+	return Manifest{Module: "new-broker", Provides: []Offer{{Name: "mesh-bus", Scope: ScopeMesh}},
+		Claims: []Claim{{Name: "mesh-broker", Scope: ScopeMesh}}}
+}
+
+// Nothing on record: exactly the old rule. One claimant holds; two are refused.
+func TestWithNoHolderOnRecordTheSoleClaimantHoldsAndTwoAreRefused(t *testing.T) {
+	busSeatDelivering(t, "mesh-bus")
+	node := Node{Name: "anchor"}
+
+	held, problems := checkClaims([]Manifest{oldBroker()}, node, nil, nil)
+	if len(problems) != 0 || len(held) != 1 || held[0].Module != "old-broker" {
+		t.Fatalf("a sole claimant did not hold the seat: held=%v problems=%v", held, problems)
+	}
+	_, problems = checkClaims([]Manifest{oldBroker(), newBroker()}, node, nil, nil)
+	if len(problems) != 1 || !strings.Contains(problems[0], "both claim") {
+		t.Fatalf("two claimants with nothing on record were not refused: %v", problems)
+	}
+}
+
+// With a holder on record, the other eligible assignment is silent: not refused, and not holding.
+func TestTheHolderOnRecordHoldsAndTheOtherClaimantStandsBesideIt(t *testing.T) {
+	busSeatDelivering(t, "mesh-bus")
+	node := Node{Name: "anchor"}
+	record := []Held{{Claim: "mesh-broker", Scope: ScopeMesh, Node: "anchor", Module: "new-broker"}}
+
+	held, problems := checkClaims([]Manifest{oldBroker(), newBroker()}, node, nil, record)
+	if len(problems) != 0 {
+		t.Fatalf("the assignment beside the holder was refused: %v", problems)
+	}
+	if len(held) != 1 || held[0].Module != "new-broker" {
+		t.Fatalf("the holder on record is not the one holding: %v", held)
+	}
+}
+
+// The record names a node too: an eligible module on another machine holds nothing, and its
+// machine's set still resolves.
+func TestAHolderOnRecordElsewhereLeavesThisMachinesClaimantSilent(t *testing.T) {
+	busSeatDelivering(t, "mesh-bus")
+	record := []Held{{Claim: "mesh-broker", Scope: ScopeMesh, Node: "anchor", Module: "new-broker"}}
+
+	held, problems := checkClaims([]Manifest{oldBroker()}, Node{Name: "laptop"}, nil, record)
+	if len(problems) != 0 || len(held) != 0 {
+		t.Fatalf("a claimant elsewhere than the recorded holder was not simply silent: held=%v problems=%v",
+			held, problems)
+	}
+}
+
+// A record naming a seat's former name still applies to it after a rename (ADR 0122).
+func TestAHolderRecordedUnderAFormerNameStillHolds(t *testing.T) {
+	busSeatDelivering(t, "mesh-bus")
+	wasAliases := aliases
+	t.Cleanup(func() { UseAliases(wasAliases) })
+	UseAliases(map[string]string{"the-broker": "mesh-broker"})
+	record := []Held{{Claim: "the-broker", Scope: ScopeMesh, Node: "anchor", Module: "new-broker"}}
+
+	held, problems := checkClaims([]Manifest{oldBroker(), newBroker()}, Node{Name: "anchor"}, nil, record)
+	if len(problems) != 0 || len(held) != 1 || held[0].Module != "new-broker" {
+		t.Fatalf("a record under the former name did not settle the seat: held=%v problems=%v", held, problems)
+	}
+}
+
+// CanHold is the one judgement registration and the handover share, against the store's row.
+func TestCanHoldJudgesClaimScopeAndWhatTheSeatDelivers(t *testing.T) {
+	busSeatDelivering(t, "mesh-bus")
+	seat, _ := SeatNamed("mesh-broker")
+
+	if err := CanHold(newBroker(), seat); err != nil {
+		t.Fatalf("a module that claims the seat and provides what it delivers was refused: %v", err)
+	}
+	noClaim := Manifest{Module: "quiet", Provides: []Offer{{Name: "mesh-bus", Scope: ScopeMesh}}}
+	if err := CanHold(noClaim, seat); err == nil || !strings.Contains(err.Error(), "does not claim") {
+		t.Fatalf("a module that never claimed the seat was allowed to hold it: %v", err)
+	}
+	wrongScope := newBroker()
+	wrongScope.Claims[0].Scope = ScopeNode
+	if err := CanHold(wrongScope, seat); err == nil || !strings.Contains(err.Error(), "scope") {
+		t.Fatalf("a claim at the wrong scope was allowed: %v", err)
+	}
+	cannotAnswer := Manifest{Module: "amqp-only", Provides: []Offer{{Name: "amqp", Scope: ScopeMesh}},
+		Claims: []Claim{{Name: "mesh-broker", Scope: ScopeMesh}}}
+	if err := CanHold(cannotAnswer, seat); err == nil || !strings.Contains(err.Error(), `does not provide "mesh-bus"`) {
+		t.Fatalf("a holder that cannot answer for the seat was allowed: %v", err)
+	}
+	// And the judgement follows the store's row, not a compiled copy.
+	busSeatDelivering(t, "amqp")
+	seat, _ = SeatNamed("mesh-broker")
+	if err := CanHold(cannotAnswer, seat); err != nil {
+		t.Fatalf("with the row saying amqp, an amqp provider was refused: %v", err)
+	}
+}
+
+// A machine being moved is handed its membership for the new bus as a sealed file in its own
+// declaration — the machine's, not any module's (design 28, task 5.2).
+func TestAMembershipForTheNewBusIsComposedAsASealedFile(t *testing.T) {
+	r := Resolution{Node: "anchor"}
+	got, err := r.Compose(Rendering{BusMembership: "sealed-blob"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found map[string]any
+	for _, res := range got.Resources {
+		if res["id"] == BusMembershipID() {
+			found = res
+		}
+	}
+	if found == nil {
+		t.Fatalf("no membership resource in %v", got.Resources)
+	}
+	if found["path"] != BusMembershipPath || found["sealed"] != "sealed-blob" || found["mode"] != "0600" {
+		t.Fatalf("the membership is not a sealed 0600 file where the host reads it: %v", found)
+	}
+	// And a machine not being moved is handed nothing.
+	got, _ = r.Compose(Rendering{})
+	for _, res := range got.Resources {
+		if res["id"] == BusMembershipID() {
+			t.Fatal("a machine with no membership on record was handed one")
+		}
+	}
+}
+
+// The store's seat rows have no protocol columns yet; loading them must not drop the protocol the
+// bus is derived from, or no role's work queue is ever raised (found live, 2026-09-28).
+func TestAStoreRowWithoutAProtocolKeepsTheCompiledOne(t *testing.T) {
+	was := Seats()
+	t.Cleanup(func() { UseSeats(was) })
+	UseSeats([]Seat{{Name: "mesh-build-machine", Scope: ScopeMesh, Decision: "row"}})
+	got, ok := SeatNamed("mesh-build-machine")
+	if !ok || len(got.Accepts) == 0 {
+		t.Fatalf("the build machine's seat lost what it accepts when loaded from the store: %+v", got)
+	}
+	if got.Decision != "row" {
+		t.Fatalf("the store's own columns were not kept: %+v", got)
+	}
+}
@@ -0,0 +1,106 @@
+package catalogue_test
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/overlay"
+)
+
+// novox/hq issue 128, held where the host will see it: the shipped networking module's names,
+// through the whole composition, and not only through FactsInto.
+//
+// Composition prefixes a fact's id with the module that asked for it and passes everything else
+// through; a step that dropped `into` on the way would send the region as a whole file, and the
+// host would write the machine's hosts file over again with every unit test above still green.
+
+// onTheNetwork stands in for the overlay's generator: the node is part of the private network,
+// and what the generator writes is not what is under test here.
+type onTheNetwork struct{}
+
+func (onTheNetwork) Resources(string) ([]map[string]any, bool, error) {
+	return []map[string]any{{"id": "overlay-config", "type": "file",
+		"path": "/etc/wireguard/mesh0.conf", "mode": "0600", "content": "[Interface]\n"}}, true, nil
+}
+
+func TestTheHostsRegionArrivesAsTheHostWillReadIt(t *testing.T) {
+	shelf := provided(t)
+	// A resolver restarting on the names another module put on the machine, and one resource it
+	// only runs at start — neither of which composition has any business changing.
+	resolver, err := catalogue.ParseManifest([]byte(`{
+		"module": "resolver", "version": "1", "requires": ["mesh-addressing"],
+		"resources": [
+			{"id": "seed", "type": "file", "path": "/etc/resolver/seed", "mode": "0644",
+			 "content": "seed\n", "at": "start"},
+			{"id": "daemon", "type": "service", "unit": "resolver.service", "state": "running",
+			 "restart-on": ["seed", "mesh-wireguard.fact-node-names"]}
+		]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	shelf[resolver.Module] = resolver
+
+	got, err := catalogue.Resolve(shelf, []string{overlay.Domain, "resolver"},
+		catalogue.Node{Name: "homer", At: "homer.internal"}, catalogue.World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	names := map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2"}
+	out, err := got.Declaration(catalogue.Rendering{
+		Names: names, Machines: names, Suffix: "internal",
+		Generators: map[string]catalogue.Generator{overlay.Name: onTheNetwork{}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ids := map[string]map[string]any{}
+	for _, r := range out {
+		ids[r["id"].(string)] = r
+	}
+
+	hosts := ids[overlay.Name+".fact-node-names"]
+	if hosts == nil {
+		t.Fatalf("no names reached the machine; the declaration has %v", keys(ids))
+	}
+	if hosts["path"] != "/etc/hosts" || hosts["into"] != "block" {
+		t.Fatalf("the hosts file is not written into as a region: %v", hosts)
+	}
+	content := hosts["content"].(string)
+	if !strings.Contains(content, "10.42.0.1\thomer.internal\thomer\t# this machine\n") {
+		t.Errorf("the region does not name the machine:\n%s", content)
+	}
+	for _, floor := range []string{"Generated by the mesh", "localhost", "127.0.1.1"} {
+		if strings.Contains(content, floor) {
+			t.Errorf("the region carries %q, which is the machine's:\n%s", floor, content)
+		}
+	}
+
+	// The resolver's reference to it still names a resource the host will be sent.
+	daemon := ids["resolver.daemon"]
+	if daemon == nil {
+		t.Fatalf("the resolver's service was not composed: %v", keys(ids))
+	}
+	for _, named := range daemon["restart-on"].([]any) {
+		if ids[named.(string)] == nil {
+			t.Errorf("the resolver restarts on %v, which is nothing the host is sent", named)
+		}
+	}
+	if !reflect.DeepEqual(daemon["restart-on"], []any{"resolver.seed", overlay.Name + ".fact-node-names"}) {
+		t.Errorf("restart-on is %v", daemon["restart-on"])
+	}
+
+	// And a resource's own `at` passes through as the manifest wrote it.
+	if seed := ids["resolver.seed"]; seed == nil || seed["at"] != "start" {
+		t.Errorf("a resource's at did not survive composition: %v", seed)
+	}
+}
+
+func keys(m map[string]map[string]any) []string {
+	out := make([]string, 0, len(m))
+	for k := range m {
+		out = append(out, k)
+	}
+	return out
+}
@@ -0,0 +1,62 @@
+package catalogue
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// A node's fail2ban jails, composed from the modules it runs (novox/hq to-be 31).
+//
+// **The same shape as the firewall.** Every module's `listens` become the node's rule set; every
+// module's `jails` become the node's fail2ban config. A module that runs an authenticating service
+// declares what a break-in on it looks like and how to ban it, naming no node and no path (ADR
+// 0112); the intrusion-prevention holder — the one module with `jailing` — gathers them and writes
+// them where it owns. A node not running a module has none of its jails.
+
+// jailsInto composes every jail declared by the modules on a node into the files the holder writes:
+// one jail file (all stanzas, so the fail2ban service restarts on a single resource) and one filter
+// file per jail (its failregex, which fail2ban references by the jail's name).
+//
+// Owned by the holder, because the directory is: two modules writing into one fail2ban is the
+// collision the holder model exists to prevent. Empty when nothing declares a jail — then the file
+// is written empty rather than absent, so removing the last jail is an ordinary change the service
+// restarts on rather than a file that vanishes.
+func jailsInto(modules []Manifest, j *Jailing) []map[string]any {
+	type declared struct {
+		module string
+		jail   Jail
+	}
+	var jails []declared
+	for _, m := range modules {
+		for _, jail := range m.Jails {
+			jails = append(jails, declared{m.Module, jail})
+		}
+	}
+	// A stable order the host applies as given (ADR 0005), and so the same set composes byte for
+	// byte every time rather than differing by map iteration.
+	sort.Slice(jails, func(a, b int) bool { return jails[a].jail.Name < jails[b].jail.Name })
+
+	var composed strings.Builder
+	composed.WriteString("# The mesh's jails, composed from the modules this node runs. Do not edit —\n")
+	composed.WriteString("# replaced whenever the node's modules change (novox/hq to-be 31).\n")
+
+	out := make([]map[string]any, 0, len(jails)+1)
+	for _, d := range jails {
+		fmt.Fprintf(&composed, "\n# from %s\n[%s]\nenabled = true\nfilter = %s\n%s\n",
+			d.module, d.jail.Name, d.jail.Name, strings.TrimRight(d.jail.Jail, "\n"))
+		// The filter is a file of its own, named as the jail's filter= references it.
+		out = append(out, map[string]any{
+			"id":   "filter-" + d.jail.Name,
+			"type": "file", "path": strings.TrimRight(j.FilterInto, "/") + "/" + d.jail.Name + ".conf",
+			"mode": "0644",
+			"content": "# Generated by the mesh (from module " + d.module + "). Do not edit.\n" +
+				"[Definition]\nfailregex = " + d.jail.Failregex + "\n",
+		})
+	}
+	// The one jail file, first, with the fixed id the fail2ban service names in its restart-on.
+	return append([]map[string]any{{
+		"id": ComposedJailsID(), "type": "file", "path": j.Into, "mode": "0644",
+		"content": composed.String(),
+	}}, out...)
+}
@@ -0,0 +1,46 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// A node's fail2ban jails are composed from the modules it runs (novox/hq to-be 31): the holder
+// (jailing) gathers every module's declared jail into one jail file and a filter file per jail.
+func TestJailsAreComposedFromTheNodesModules(t *testing.T) {
+	modules := []Manifest{
+		{Module: "fail2ban", Jailing: &Jailing{Into: "/etc/fail2ban/jail.d/mesh-composed.conf", FilterInto: "/etc/fail2ban/filter.d"}},
+		{Module: "postgres", Jails: []Jail{{Name: "postgres-auth", Failregex: "auth failed from <HOST>", Jail: "port = 5432\nmaxretry = 5"}}},
+	}
+	files := jailsInto(modules, modules[0].Jailing)
+
+	by := map[string]map[string]any{}
+	for _, f := range files {
+		by[f["id"].(string)] = f
+	}
+	jail := by[ComposedJailsID()]
+	if jail == nil || jail["path"] != "/etc/fail2ban/jail.d/mesh-composed.conf" {
+		t.Fatalf("the composed jail file was not written: %v", jail)
+	}
+	body := jail["content"].(string)
+	if !strings.Contains(body, "[postgres-auth]") || !strings.Contains(body, "filter = postgres-auth") ||
+		!strings.Contains(body, "port = 5432") {
+		t.Fatalf("the postgres jail stanza was not composed in:\n%s", body)
+	}
+	filter := by["filter-postgres-auth"]
+	if filter == nil || filter["path"] != "/etc/fail2ban/filter.d/postgres-auth.conf" {
+		t.Fatalf("the jail's filter file was not written: %v", filter)
+	}
+	if !strings.Contains(filter["content"].(string), "failregex = auth failed from <HOST>") {
+		t.Fatalf("the failregex was not written: %v", filter["content"])
+	}
+}
+
+// A holder whose node runs no jail-declaring module still gets the file, empty — so removing the
+// last jail is a change the service restarts on, not a file that vanishes.
+func TestTheComposedJailFileIsWrittenEvenWhenEmpty(t *testing.T) {
+	files := jailsInto([]Manifest{{Module: "fail2ban"}}, &Jailing{Into: "/x", FilterInto: "/f"})
+	if len(files) != 1 || files[0]["id"] != ComposedJailsID() {
+		t.Fatalf("the empty composed jail file was not written alone: %v", files)
+	}
+}
@@ -57,7 +57,7 @@ func machineUsed(content string) []string {
 // the hosts file and the resolver's wildcards are written from, so a file naming the machine's
 // address and the file every other machine reaches it by cannot disagree. Absent, like `at`, when
 // the machine is off the network or the mesh has not placed it.
-func machineFacts(r Resolution, names map[string]string) map[string]string {
+func machineFacts(r Resolution, names map[string]string, meshRange string) map[string]string {
 	out := map[string]string{"name": r.Node}
 	if r.At != "" {
 		out["at"] = r.At
@@ -65,32 +65,59 @@ func machineFacts(r Resolution, names map[string]string) map[string]string {
 			out["address"] = address
 		}
 	}
+	// The private network's whole range — a mesh-wide fact, not this machine's, but named here
+	// because a module cannot know it and sometimes must (an intrusion filter that must never ban a
+	// tunnel peer). Absent when the mesh has no range to give.
+	if meshRange != "" {
+		out["mesh-range"] = meshRange
+	}
+	// The operator's login on this machine and where its home is (novox/hq to-be 29), so a module
+	// that writes operator config names the account and its home rather than a value it cannot know.
+	// Absent when no operator account is known — a headless box a person never logs into.
+	if r.Account != "" {
+		out["account"] = r.Account
+		out["account-home"] = accountHomeOf(r.Account, r.AccountHome)
+	}
 	return out
 }

+// accountHomeOf is where an account's home is: what was stored, or the derived default — /root for
+// root, /home/<account> otherwise. The one place the default is written, so a fact and the store
+// cannot disagree about it.
+func accountHomeOf(account, home string) string {
+	if home != "" {
+		return home
+	}
+	if account == "root" {
+		return "/root"
+	}
+	return "/home/" + account
+}
+
 // machineInto replaces a file's ${machine:…} placeholders with what the mesh knows about the
 // machine the module was assigned to.
 //
 // A key the mesh does not hold is refused, for the same reason a binding's is: left alone, the
 // literal would be written into a configuration file and read as a value.
 func machineInto(resource map[string]any, facts map[string]string, module string) error {
-	if fmt.Sprint(resource["type"]) != "file" {
-		return nil
-	}
-	content, ok := resource["content"].(string)
-	if !ok {
-		return nil
-	}
-	for _, key := range machineUsed(content) {
-		value, has := facts[key]
-		if !has {
-			return fmt.Errorf(
-				"%s has a file that says ${machine:%s}, and this machine says %s",
-				module, key, orNothing(namesOfFacts(facts)))
+	// Content, and now the path and owner too: a module that writes into a person's home names it
+	// with ${machine:account-home} and ${machine:account}, which it cannot know until assigned
+	// (novox/hq to-be 29), the same reason its content names ${machine:address}.
+	for _, field := range []string{"path", "owner", "content"} {
+		s, ok := resource[field].(string)
+		if !ok {
+			continue
+		}
+		for _, key := range machineUsed(s) {
+			value, has := facts[key]
+			if !has {
+				return fmt.Errorf(
+					"%s has a %s that says ${machine:%s}, and this machine says %s",
+					module, field, key, orNothing(namesOfFacts(facts)))
+			}
+			s = strings.ReplaceAll(s, fmt.Sprintf("${machine:%s}", key), value)
+			resource[field] = s
 		}
-		resource["content"] = strings.ReplaceAll(
-			content, fmt.Sprintf("${machine:%s}", key), value)
-		content = resource["content"].(string)
 	}
 	return nil
 }
@@ -103,3 +103,26 @@ func TestAModuleNamesTheAddressBehindItsMachinesName(t *testing.T) {
 		t.Fatalf("a machine off the network was given an address, or refused for another reason: %v", err)
 	}
 }
+
+// The mesh's private range is offered as ${machine:mesh-range}, so a module names it rather than
+// hardcoding a value it cannot know (novox/hq ADR 0112) — the fail2ban ignoreip is the case.
+func TestAModuleNamesTheMeshRange(t *testing.T) {
+	facts := machineFacts(Resolution{Node: "anchor", At: "anchor.internal"},
+		map[string]string{"anchor.internal": "10.10.0.1"}, "10.10.0.0/24")
+	if facts["mesh-range"] != "10.10.0.0/24" {
+		t.Fatalf("the mesh range is not a machine fact: %v", facts)
+	}
+	res := map[string]any{"type": "file", "id": "jail", "content": "ignoreip = 127.0.0.1/8 ${machine:mesh-range}\n"}
+	if err := machineInto(res, facts, "fail2ban"); err != nil {
+		t.Fatal(err)
+	}
+	if got := res["content"].(string); !strings.Contains(got, "10.10.0.0/24") || strings.Contains(got, "${machine:") {
+		t.Fatalf("the mesh range was not written in: %q", got)
+	}
+	// A mesh with no range gives no such fact, and a file that names it is refused rather than
+	// left with a literal placeholder in it.
+	none := machineFacts(Resolution{Node: "anchor"}, nil, "")
+	if _, has := none["mesh-range"]; has {
+		t.Fatal("a mesh with no range still offered one")
+	}
+}
@@ -176,15 +176,29 @@ type Manifest struct {
 	// Requires are names that must be provided by something assigned to the same node.
 	Requires []string `json:"requires,omitempty"`

-	// Emits are the event types this module publishes onto the broker — dotted topic keys, e.g.
-	// "module.umami.site.created". Declared so the mesh knows the event graph; events are
-	// provisioning's lighter sibling — 1:many and broadcast, no credential (novox/hq ADR 0041).
+	// Emits are the events this module publishes, named **locally**: `order.placed`, not a subject
+	// and not a routing key. The mesh derives where it lands (design 29 §1), so reorganising the
+	// subject space leaves this manifest correct. Events are provisioning's lighter sibling — 1:many
+	// and broadcast, no credential (novox/hq ADR 0041).
+	//
+	// A module publishes under its own name only. If the event is about a *role* rather than about
+	// this module, it belongs on that seat, where the name outlives whoever holds it.
+	//
+	// **This said "dotted topic keys, e.g. module.umami.site.created" until 04-ISSUES/127**, which
+	// is the old bus's routing key, and is why every manifest in the catalogue had the same mistake:
+	// nobody was guessing, everybody followed this comment.
 	Emits []string `json:"emits,omitempty"`

-	// Consumes are the event patterns this module subscribes to — topic patterns over module,
-	// mesh and node events alike, e.g. "node.*.joined" or "#" (the audit logger). The runtime
-	// wires the subscription; the module ships the handler. A Consumes for an event nothing on
-	// the mesh Emits is a dangling edge.
+	// Consumes are the events this module reacts to, each naming its emitter and the event:
+	// `billing.order.placed`. `*` stands for one name and `**` for the rest, so `*.download.completed`
+	// is that event from any module and `**` is every event in the mesh.
+	//
+	// Spelled the mesh's way rather than the wire's, for the reason Emits is: the bus the mesh runs
+	// on today spells these `*` and `#`, the one being built spells them `*` and `>`, and a manifest
+	// naming either would stop being true when the wire changed.
+	//
+	// The runtime wires the subscription; the module ships the handler. A Consumes for an event
+	// nothing on the mesh Emits is a dangling edge.
 	Consumes []string `json:"consumes,omitempty"`

 	// Claims are singular resources. Two modules claiming one thing within a scope cannot both
@@ -192,6 +206,34 @@ type Manifest struct {
 	// that every new module would force its predecessors to update.
 	Claims []Claim `json:"claims,omitempty"`

+	// DefinesSeats are the seats this module defines for itself, with their protocols
+	// (novox/hq ADR 0121, ADR 0129). The control plane defines the system seats — `mesh-*` and
+	// `node-*` — and a module may define its own, named outside that namespace, to coordinate its
+	// own instances: the mesh enforces one-holder-per-scope for it without knowing what it means. A
+	// module's declared seat is the only non-system name it may then claim; a claim to a name
+	// neither the mesh nor the module defines is refused.
+	//
+	// **Two lines of work built this at once**, one calling it `Seats` with a protocol and one
+	// `DefinesSeats` without. Same key in the file, so no manifest is affected: this is the trunk's
+	// name with the richer type, because what a role accepts, emits and serves is what lets the mesh
+	// check that a holder answers what its seat promises.
+	DefinesSeats []SeatDeclaration `json:"seats,omitempty"`
+
+	// Uses are seats this module sends to. It names the *seat*, never the module holding it, so
+	// the implementation can be replaced under it and no caller changes. A caller gets publish
+	// on that seat's inbound subjects and nothing else — not its outbound events, and not a
+	// subscription to the queue it writes to (design 29 §2).
+	Uses []string `json:"uses,omitempty"`
+
+	// Tools are the tools this module answers — request and reply, awaited.
+	//
+	// **New, and not `serves`**, which this manifest already uses for the facts a consumer needs
+	// in order to reach a provision. Two meanings under one key would be a footgun in the one
+	// file a module author reads most. Until now a module's tools were known only at runtime,
+	// from MESH_TOOL_MODULES in its image; declaring them is what lets the mesh check that a
+	// module claiming a seat answers what that seat's protocol promises (novox/hq ADR 0118).
+	Tools []string `json:"tools,omitempty"`
+
 	// Capabilities the machine must have. A different field from Requires because the remedy
 	// differs: a missing module can be assigned, and a missing capability means the wrong
 	// machine.
@@ -358,6 +400,14 @@ type Manifest struct {
 	// that could only see its own ports would write a rule set that closed everything else.
 	Filtering *Filtering `json:"filtering,omitempty"`

+	// Jails are the fail2ban jails this module declares for its own service (novox/hq to-be 31).
+	// Written into whichever node runs the module, the same way `listens` become that node's rules.
+	Jails []Jail `json:"jails,omitempty"`
+
+	// Jailing marks the module that composes the node's fail2ban jails — the intrusion-prevention
+	// holder. Like Filtering: one module per node gathers what every module declared and writes it.
+	Jailing *Jailing `json:"jailing,omitempty"`
+
 	// Guards are ports of this module's the mesh refuses on an adopted node except from the
 	// private network and from the machine itself (novox/hq ADR 0100) — the store's port and the
 	// broker's management port. The ports the software uses; the mesh guards where the machine
@@ -366,24 +416,29 @@ type Manifest struct {
 	// firewall does. Ignored on a converged node, whose derived filter already closes them.
 	Guards []int `json:"guards,omitempty"`

-	// Facts are things only the mesh knows, written where this module asks for them.
+	// Facts are things only the mesh knows, written where this module asks for them — in the
+	// module's own format.
 	//
-	// **The graph is the control plane's; how a machine uses it is the module's.** The mesh knows
-	// which machines exist, what they are called and where they are. Making a name resolve, or a
-	// peer reachable, is somebody's software — dnsmasq, a resolver, a VPN — and the mesh has no
-	// business shipping one, choosing which, or knowing its configuration language.
+	// **The graph is the control plane's; the format is the module's.** The mesh knows which
+	// machines exist, what they are called and where they are. Turning that into a name that
+	// resolves, a peer that is reachable, a host a client trusts, is somebody's software — dnsmasq,
+	// a resolver, a VPN, ssh — in its own configuration language, and the mesh has no business
+	// knowing it. So a module gives a path and a template; the mesh renders the roster through it
+	// and owns nothing of what the file says.
 	//
-	// So a module says *put the node names here* and owns everything after that. The same shape as
-	// `filtering`, generalised: a fact, and a path.
+	// This used to be a closed list of fact names, each formatted in Go in the control plane, so a
+	// new consumer meant a new formatter here in the consumer's language. Now the data is the mesh's
+	// and the format is the module's: the two built-in cases — the network module's `/etc/hosts` and
+	// dnsmasq's zones — render through the same template path any module uses, and no format lives
+	// in the control plane at all. See RosterFile for what a template sees.
 	//
 	// It replaces three modules that existed only because computed output needed somewhere to
 	// live — they ran no software, could not be swapped for anything, and appeared in the graph as
 	// modules while being a data channel wearing a costume.
 	//
-	// Keyed by fact name; the names are a closed list, because a module asking for one the mesh
-	// does not compute is asking for something nobody will write, and finding that out on a machine
-	// is worse than being told here.
-	Facts map[string]string `json:"facts,omitempty"`
+	// Keyed by a name the module chooses, which is the rendered file's id (`fact-<name>`) — what a
+	// `restart-on` names to restart when the roster changes.
+	Facts map[string]RosterFile `json:"facts,omitempty"`

 	// Certificate is where this module wants a certificate for its machine's name inside the
 	// mesh, and where the key that goes with it can be found.
@@ -403,6 +458,20 @@ type Manifest struct {
 	// A directory rather than one document for the same reason as above: each value is sealed
 	// separately and the mesh cannot open any of them to build a list.
 	Grants map[string]string `json:"grants,omitempty"`
+
+	// BusUsers is where this module wants the mesh's user list written, and it is only ever
+	// answered for the module holding `mesh-broker`.
+	//
+	// **The mesh writes who may connect; the module owns everything else about its server**
+	// (novox/hq design 25 §4, task 1.7). Ports, TLS paths and a store directory live in this
+	// module's image and its mounts and change when it does, so the module's own configuration
+	// carries them and includes this file. A controller that wrote the whole configuration would
+	// have to be kept in step with a Dockerfile it never sees.
+	//
+	// **Asking for it is not enough to receive it.** This file holds every user's password hash, so
+	// a module that could ask for it could read every credential on the bus — and the claim on
+	// `mesh-broker` is what authorises it, checked from this manifest alone.
+	BusUsers string `json:"bus-users,omitempty"`
 }

 // Build says how to produce this module's artifacts from its source.
@@ -602,6 +671,36 @@ func (l Listening) At() string {
 	return l.Protocol
 }

+// Jail is a fail2ban jail a module declares for its own service (novox/hq to-be 31).
+//
+// **The module names no node and no path** (ADR 0112): it says what a break-in on its service looks
+// like — the failregex — and the jail's own keys (the port it watches, where it logs, how many
+// tries, how long to ban). The mesh writes it into whichever node's fail2ban runs the module, the
+// same way a module's `listens` become that node's firewall rules. A node not running the module
+// has no such jail.
+type Jail struct {
+	// Name is the jail and its filter, e.g. "postgres-auth". One holder of the name per node.
+	Name string `json:"name"`
+	// Failregex is what a failed authentication looks like in the service's log — the filter.
+	Failregex string `json:"failregex"`
+	// Jail is the body of the jail's stanza: the keys under [<name>] the module knows and the mesh
+	// does not — the port it watches, its logpath and backend, maxretry, bantime.
+	Jail string `json:"jail"`
+}
+
+// Jailing says a module composes the node's fail2ban jails — the intrusion-prevention holder. Like
+// Filtering for the firewall: one module gathers what every other module declared and writes it
+// where it owns. Into is the one jail file the stanzas are composed into (so the fail2ban service
+// can restart on a single resource); FilterInto is the directory each jail's filter file goes in.
+type Jailing struct {
+	Into       string `json:"into"`
+	FilterInto string `json:"filter-into"`
+}
+
+// ComposedJailsID is the single jail file the mesh composes every declared jail into, so the
+// fail2ban service names one resource in its restart-on and a jail added or removed reaches it.
+func ComposedJailsID() string { return "composed-jails" }
+
 // Filtering says where a module wants the computed rule set.
 type Filtering struct {
 	// Into is the path to write it to. Whatever loads it is this module's own business — an
@@ -621,7 +720,22 @@ type Certificate struct {

 // CertificateID and AuthorityID are the resource identities of what the mesh issued.
 func CertificateID() string { return "certificate" }
-func AuthorityID() string   { return "certificate-authority" }
+
+// ClaimsSeat says whether this manifest claims one named seat.
+func (m Manifest) ClaimsSeat(seat string) bool {
+	for _, c := range m.Claims {
+		if c.Name == seat {
+			return true
+		}
+	}
+	return false
+}
+
+// BusUsersID names the mesh's composed user list, so it is the same resource across every
+// declaration and a change to it is an update rather than a second file beside the old one — which
+// on a bus reading a directory would be two account lists, and the server would take both.
+func BusUsersID() string  { return "bus-users" }
+func AuthorityID() string { return "certificate-authority" }

 // FilteringID names the computed rule set, so it is the same resource across every declaration
 // and a change to it is an update rather than an addition beside the old one.
@@ -913,6 +1027,28 @@ func ParseManifest(raw []byte) (Manifest, error) {
 		problems = append(problems, fmt.Sprintf(
 			"%q is not a usable slug: lower-case letters, digits, dashes and dots", m.Slug))
 	}
+	// **`amqp` is not a provision, and not a requirement** (novox/hq ADR 0131). A module that wants
+	// messaging wants the mesh's bus — it emits and consumes through the sdk, which the mesh hands the
+	// bus with the module's own credential — and the bus is whatever holds `mesh-broker`, spoken in
+	// whatever that holder speaks. Naming the old wire protocol asks for a specific server, and the
+	// only one that could answer is the one being retired. Refused here so the word cannot come back
+	// through a manifest.
+	for _, offer := range m.Provides {
+		if offer.Name == "amqp" {
+			problems = append(problems, fmt.Sprintf(
+				"%s provides %q, which is not a provision: the mesh's bus is whatever holds "+
+					"mesh-broker, and a module provides mesh-bus to be it (novox/hq ADR 0131)",
+				m.Module, offer.Name))
+		}
+	}
+	for _, r := range m.Requires {
+		if r == "amqp" {
+			problems = append(problems, fmt.Sprintf(
+				"%s requires %q, which is not a provision: a module reaches the mesh's bus through "+
+					"the sdk, and depends on the mesh-broker seat, not on a protocol (novox/hq ADR 0131)",
+				m.Module, r))
+		}
+	}
 	for _, offer := range m.Provides {
 		p := offer.Name
 		if !name.MatchString(p) {
@@ -950,6 +1086,10 @@ func ParseManifest(raw []byte) (Manifest, error) {
 			problems = append(problems, fmt.Sprintf("%s requires itself", m.Module))
 		}
 	}
+	// What it may call an event, and what it may ask to hear (events.go). Checked here because a
+	// module whose event names are wrong installs, starts, connects and reacts to nothing, with
+	// every log line saying it is fine (novox/hq 04-ISSUES/127).
+	problems = append(problems, EventProblems(m)...)
 	wellFormed := true
 	for _, c := range m.Claims {
 		if !name.MatchString(c.Name) {
@@ -970,6 +1110,10 @@ func ParseManifest(raw []byte) (Manifest, error) {
 	if wellFormed {
 		problems = append(problems, claimProblems(m)...)
 	}
+	// What one manifest can be judged on: a declaration's shape, its scope, and the reserved
+	// prefix. Whether a seat anybody names exists, and whether a holder answers for it, are
+	// facts about the catalogue and are checked at registration (CatalogueProblems).
+	problems = append(problems, declaredSeatProblems(m)...)
 	if m.Computed != "" && len(m.Resources) > 0 {
 		// One or the other. A module that both ships files and has them computed would leave
 		// nobody able to say where a given file came from.
@@ -0,0 +1,121 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+// **A manifest holds no subject** (novox/hq design 29 §1).
+//
+// A module names its events, tools and seats locally, and the mesh derives where they land. The
+// property that buys: reorganise the subject space and every manifest in the catalogue is still
+// correct. It holds today by construction — nothing reads a subject from a manifest — and a rule
+// held by construction is one a later field breaks quietly, with the symptom appearing as a
+// permission that does not match a subject rather than as a manifest that was wrong.
+func TestNoManifestContainsASubject(t *testing.T) {
+	root := filepath.Join("..", "..", "..", "mesh-catalog", "modules")
+	entries, err := os.ReadDir(root)
+	if err != nil {
+		t.Skipf("catalogue sibling not present: %v", err)
+	}
+
+	// Anything in the mesh's own subject space, and anything shaped like a wire address.
+	subject := regexp.MustCompile(`^(mesh|\$JS)\.[a-zA-Z0-9_*>.-]+$`)
+
+	var found []string
+	var walk func(module string, path string, v any)
+	walk = func(module, path string, v any) {
+		switch t := v.(type) {
+		case string:
+			if subject.MatchString(t) {
+				found = append(found, module+" "+path+" = "+t)
+			}
+		case map[string]any:
+			for k, inner := range t {
+				walk(module, path+"."+k, inner)
+			}
+		case []any:
+			for _, inner := range t {
+				walk(module, path+"[]", inner)
+			}
+		}
+	}
+
+	checked := 0
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		raw, err := os.ReadFile(filepath.Join(root, e.Name(), "module.json"))
+		if err != nil {
+			continue
+		}
+		var m any
+		if err := json.Unmarshal(raw, &m); err != nil {
+			t.Errorf("%s: %v", e.Name(), err)
+			continue
+		}
+		checked++
+		walk(e.Name(), "", m)
+	}
+	if checked == 0 {
+		t.Skip("no manifests read")
+	}
+	if len(found) > 0 {
+		t.Errorf("a manifest names a subject, so reorganising the subject space would mean "+
+			"editing the catalogue:\n  %s", strings.Join(found, "\n  "))
+	}
+	t.Logf("%d manifests hold no subject", checked)
+}
+
+// **Every module's event names are what design 29 says, across the whole catalogue.**
+//
+// The rule above holds by construction and turned out to be weaker than it reads: a manifest holds
+// no subject, and every manifest in the catalogue still held the old bus's routing key, which
+// derives into a namespace nobody owns (novox/hq 04-ISSUES/127). Nothing failed — the services
+// started and none of them reacted. This is the check that was missing.
+func TestEveryManifestsEventNamesAreLocal(t *testing.T) {
+	manifests := theCatalogue(t)
+
+	var problems []string
+	for _, m := range manifests {
+		problems = append(problems, EventProblems(m)...)
+	}
+	if len(problems) > 0 {
+		t.Fatalf("the catalogue holds %d event name(s) the mesh would derive wrongly:\n  %s",
+			len(problems), strings.Join(problems, "\n  "))
+	}
+}
+
+// theCatalogue is every manifest beside this checkout, parsed the way registration parses one.
+func theCatalogue(t *testing.T) []Manifest {
+	t.Helper()
+	root := filepath.Join("..", "..", "..", "mesh-catalog", "modules")
+	entries, err := os.ReadDir(root)
+	if err != nil {
+		t.Skipf("catalogue sibling not present: %v", err)
+	}
+	var out []Manifest
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		raw, err := os.ReadFile(filepath.Join(root, e.Name(), "module.json"))
+		if err != nil {
+			continue
+		}
+		var m Manifest
+		if err := json.Unmarshal(raw, &m); err != nil {
+			t.Fatalf("%s: %v", e.Name(), err)
+		}
+		out = append(out, m)
+	}
+	if len(out) == 0 {
+		t.Skip("no manifests found beside this checkout")
+	}
+	return out
+}
@@ -54,7 +54,7 @@ func TestTheShippedNetworkingModulesResolveOnTheirOwn(t *testing.T) {
 	// network is what gives a machine a name, so the provider asks for the node-names fact and
 	// there is nothing else to bring in. A module that ran nothing used to be here.
 	for _, m := range got.Modules {
-		if m.Module == overlay.Name && m.Facts["node-names"] == "" {
+		if m.Module == overlay.Name && m.Facts["node-names"].Path == "" {
 			t.Fatalf("the network's provider does not ask for the names: %+v", m.Facts)
 		}
 	}
@@ -28,6 +28,10 @@ type Node struct {
 	// (novox/hq ADR 0066). A route contribution carries only a label — the subdomain — and the mesh
 	// joins <label>.<public-domain> to make the name it grants, interpreting neither half.
 	PublicDomain string
+	// Account is the operator's login on this machine, AccountHome where its home is (novox/hq
+	// to-be 29). What a home-scoped file is owned by and what ${machine:account} resolves to.
+	Account     string
+	AccountHome string
 }

 // World is what the rest of the mesh already has.
@@ -37,6 +41,11 @@ type Node struct {
 type World struct {
 	// Held is the claims already taken, for the scopes wider than one node.
 	Held []Held
+	// Holdings is every seat whose holder is **on record** (novox/hq ADR 0131): the one assignment
+	// that holds it, chosen by a handover. A seat absent here is held by derivation — the sole
+	// eligible assignment — as it always was. Present, it decides, and any other assignment whose
+	// module could hold the seat is eligible and silent rather than refused.
+	Holdings []Held
 	// Offered is what other nodes provide at mesh scope, and everything needed to use it.
 	Offered map[string][]Provider
 	// Pinned is which node this machine was told to get a provision from, by name. Only consulted
@@ -114,6 +123,11 @@ type Resolution struct {
 	// (novox/hq ADR 0066). Carried from the node so that composing <label>.<public-domain> for a
 	// route contribution needs no store lookup here — the join is a fact about this one machine.
 	PublicDomain string
+	// Account and AccountHome are the operator's login on this machine and where its home is
+	// (novox/hq to-be 29), carried from the node so a home-scoped file's owner and path resolve
+	// here without a store lookup.
+	Account     string
+	AccountHome string

 	// Modules in the order they were resolved: assigned first, then what they pulled in.
 	Modules []Manifest
@@ -541,13 +555,14 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 	}

 	resolution := Resolution{Node: node.Name, At: node.At, PublicDomain: node.PublicDomain,
+		Account: node.Account, AccountHome: node.AccountHome,
 		Because: because, Needs: needs, Unhostable: unhostable}
 	for _, n := range providersFirst(order, catalogue) {
 		resolution.Modules = append(resolution.Modules, catalogue[n])
 	}

 	problems = append(problems, checkCapabilities(resolution.Modules, node)...)
-	claims, claimProblems := checkClaims(resolution.Modules, node, elsewhere)
+	claims, claimProblems := checkClaims(resolution.Modules, node, elsewhere, world.Holdings)
 	problems = append(problems, claimProblems...)
 	problems = append(problems, checkResources(resolution.Modules)...)
 	resolution.Claims = claims
@@ -640,14 +655,35 @@ func checkCapabilities(modules []Manifest, node Node) []string {
 //
 // Within this node's own set, and against what is already held elsewhere for the wider scopes. A
 // claim at mesh scope is the same idea as the mesh's one hub, said once instead of hard-coded.
-func checkClaims(modules []Manifest, node Node, elsewhere []Held) ([]Held, []string) {
+func checkClaims(modules []Manifest, node Node, elsewhere []Held, holdings []Held) ([]Held, []string) {
 	var problems []string
 	var held []Held

+	// onRecord is the recorded holder of a seat, if a handover ever named one.
+	onRecord := func(claim, scope string) (Held, bool) {
+		for _, h := range holdings {
+			hs, ok := SeatNamed(h.Claim)
+			cs, cok := SeatNamed(claim)
+			if ok && cok && hs.Name == cs.Name && h.Scope == scope {
+				return h, true
+			}
+		}
+		return Held{}, false
+	}
+
 	byScope := map[string]map[string]string{} // scope → claim → module
 	for _, m := range modules {
 		for _, c := range m.Claims {
 			scope := c.At()
+			// **A recorded holder settles it before any counting.** An assignment that could hold
+			// the seat but is not the one on record is eligible, and that is all: it is not a second
+			// holder, so it is not refused, and it does not hold (novox/hq ADR 0131). This is what
+			// lets the next holder stand beside the current one until the seat is handed over.
+			if rec, recorded := onRecord(c.Name, scope); recorded {
+				if rec.Node != node.Name || rec.Module != m.Module {
+					continue
+				}
+			}
 			if byScope[scope] == nil {
 				byScope[scope] = map[string]string{}
 			}
@@ -50,7 +50,7 @@ func TestTheResolverForwardsToFixedUpstreamsAndNeverReadsResolvConf(t *testing.T
 		"\nno-resolv\n", "\nserver=1.1.1.1\n", "\nserver=8.8.8.8\n",
 		"\nlisten-address=127.0.0.1\n", "\ninterface=mesh0\n", "\nbind-dynamic\n",
 		"\ndomain-needed\n", "\nbogus-priv\n",
-		"\nconf-file=" + m.Facts[FactNodeZones] + "\n",
+		"\nconf-file=" + m.Facts["node-zones"].Path + "\n",
 	} {
 		if !strings.Contains(config, want) {
 			t.Errorf("the resolver's configuration lacks %q:\n%s", strings.TrimSpace(want), config)
@@ -170,7 +170,7 @@ func TestTwoThingsDecidingWhatAMachineAsksAreRefused(t *testing.T) {
 	if err == nil {
 		t.Fatal("resolv-conf and resolved-split-dns were both assigned to one machine")
 	}
-	if !strings.Contains(err.Error(), "the-resolver-configuration") {
+	if !strings.Contains(err.Error(), "node-resolver-config") {
 		t.Fatalf("the refusal does not say what was claimed: %v", err)
 	}
 }
@@ -0,0 +1,210 @@
+package catalogue
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+	"strings"
+	"text/template"
+)
+
+// What only the mesh knows, written where a module asks for it — in the module's own format.
+//
+// **The graph is the control plane's; the format is the module's.** The mesh knows which machines
+// exist, what they are called and where they are. Turning that into a hosts file, a resolver's
+// zones, an ssh known_hosts is somebody's configuration language, and the mesh has no business
+// knowing it. So the mesh hands the roster to a template the module wrote and renders it; it never
+// learns what the file means.
+//
+// This used to be a closed list of fact names, each with its format written in Go here — a hosts
+// file, a resolver's zones. Every new consumer meant a new formatter in the control plane, in the
+// consumer's configuration language. Now the data is the mesh's and the format is a template the
+// module ships: the two built-in cases (the network module's `/etc/hosts`, dnsmasq's zones) render
+// the same way any module's would, and the control plane holds no format at all.
+//
+// It replaced three modules that existed only because computed output needed somewhere to live —
+// they ran no software, could not be swapped for anything, and appeared in the graph as modules
+// while being a data channel wearing a costume (novox/hq ADR 0040).
+
+// A RosterFile is a file the mesh renders from the roster of machines, in the format the module
+// gives as a Go text/template. The template sees a rosterView: `.Node` (this machine's bare name),
+// `.Suffix` (what its mesh name ends in), and two sets of `{Name, FQDN, Address}` — `.Names`, every
+// name the mesh serves, and `.Machines`, only the nodes of the mesh. Which set a template ranges is
+// how the hq issue 111 distinction is drawn: a container's hosts wants every name; a resolver told
+// the suffix is its own wants only the machines.
+type RosterFile struct {
+	// Path is where on the machine the rendered file goes. Absolute, or it is refused here rather
+	// than discovered as a daemon that reads nothing.
+	Path string `json:"path"`
+	// Template is the module's format, a Go text/template over the rosterView. It is the module's,
+	// not the mesh's: the mesh renders it and does not read it.
+	Template string `json:"template"`
+	// Shared is whether the file the fact goes to belongs to the machine rather than the mesh. When
+	// it does, the mesh owns only a marked region of it and keeps the rest byte for byte (novox/hq
+	// issue 128) — a hosts file is shared, since the distribution's `localhost`, the operator's own
+	// lines and other tools' blocks live there too; a resolver's zones file is not, the mesh owns it
+	// whole. A property of the fact, not of the path: the format determines whether the file is
+	// wholly the mesh's, not where a module happened to ask for it.
+	Shared bool `json:"shared,omitempty"`
+	// Home places the file under this node's operator-account home and chowns it to that account,
+	// rather than at an absolute system path (novox/hq to-be 29). Then Path is home-relative
+	// (`.ssh/config.d/mesh`), resolved against the account's home on the node it is composed for; a
+	// node with no operator account gets no such file. This is how the ssh-client config — every
+	// other node's Host block — is written into a person's home rather than into /etc.
+	Home bool `json:"home,omitempty"`
+}
+
+// rosterView is what a RosterFile's template sees. A closed shape — a template referencing a field
+// the mesh does not compute fails to render here, not on a machine.
+type rosterView struct {
+	Node     string
+	Suffix   string
+	Names    []rosterEntry
+	Machines []rosterEntry
+}
+
+// rosterEntry is one machine as a template sees it: its bare name, its full mesh name, its address,
+// and the operator account to log into it as (novox/hq to-be 29) — empty when none is known, so an
+// ssh Host block template can omit the User line for a machine nobody has an account on.
+type rosterEntry struct {
+	Name    string
+	FQDN    string
+	Address string
+	Account string
+}
+
+// FactsInto renders the roster files a module asked for, as files it will be given.
+//
+// The module owns everything after the file exists: loading it, restarting on it, what a resolver
+// or a client does with it. This only puts it there. `every` is every name the mesh serves;
+// `machines` is only the machines — the two must not be confused (novox/hq 04-ISSUES/111), so both
+// are given and the template chooses.
+func FactsInto(m Manifest, r Resolution, every, machines, accounts map[string]string, suffix string) ([]map[string]any, error) {
+	if len(m.Facts) == 0 {
+		return nil, nil
+	}
+	names := make([]string, 0, len(m.Facts))
+	for name := range m.Facts {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+
+	view := rosterView{
+		Node:     r.Node,
+		Suffix:   strings.TrimPrefix(suffixOr(suffix), "."),
+		Names:    entriesFrom(every, accounts, suffix),
+		Machines: entriesFrom(machines, accounts, suffix),
+	}
+
+	out := make([]map[string]any, 0, len(names))
+	for _, name := range names {
+		fact := m.Facts[name]
+		content, err := renderRoster(fact.Template, view)
+		if err != nil {
+			return nil, fmt.Errorf("%s cannot render %q: %w", m.Module, name, err)
+		}
+		// Where the file goes: under the operator's home and chowned to it (a home fact), or at the
+		// absolute system path it names. A home fact on a machine with no operator account cannot be
+		// placed, and is left out rather than written to nowhere (novox/hq to-be 29).
+		path := fact.Path
+		var owner string
+		if fact.Home {
+			if r.Account == "" {
+				continue
+			}
+			path = accountHomeOf(r.Account, r.AccountHome) + "/" + strings.TrimLeft(fact.Path, "/")
+			owner = r.Account
+		} else if !strings.HasPrefix(fact.Path, "/") {
+			return nil, fmt.Errorf(
+				"%s asks for %q at %q, which is not an absolute path", m.Module, name, fact.Path)
+		}
+		file := map[string]any{
+			"id": "fact-" + name, "type": "file", "path": path, "mode": "0644",
+			"content": content,
+		}
+		if owner != "" {
+			file["owner"] = owner
+		}
+		if fact.Shared {
+			// The host owns only the lines between `# BEGIN mesh <id>` and `# END mesh <id>` and
+			// keeps the rest of the file byte for byte; undeclared, the region goes and nothing else
+			// does (novox/hq issue 128). Every node on the private network receives this, so every
+			// node's host — the controller's own machine included — must be block-aware before a
+			// controller emitting it is rolled out: the order ADR 0102 set for `into: json`.
+			file["into"] = "block"
+		}
+		out = append(out, file)
+	}
+	return out, nil
+}
+
+// renderRoster runs a module's template over the roster. A template that will not parse, or reads
+// a field the mesh does not have, is an error here — where the manifest is — rather than an empty
+// file on a machine.
+func renderRoster(tmpl string, view rosterView) (string, error) {
+	t, err := template.New("roster").Option("missingkey=error").Parse(tmpl)
+	if err != nil {
+		return "", err
+	}
+	var b bytes.Buffer
+	if err := t.Execute(&b, view); err != nil {
+		return "", err
+	}
+	return b.String(), nil
+}
+
+// entriesFrom is a name→address map as sorted roster entries.
+//
+// **A machine with no address is left out.** The mesh has a record for it — somebody added it —
+// and does not yet know where it is, which is the ordinary state between adding a machine and it
+// joining. Writing the name anyway would give a name that resolves to nothing, and a connection to
+// that hangs; leaving it out fails at once and says the name is unknown.
+func entriesFrom(addresses, accounts map[string]string, suffix string) []rosterEntry {
+	out := make([]rosterEntry, 0, len(addresses))
+	for _, name := range sortedNames(addresses) {
+		internal, bare := meshName(name, suffix)
+		// The account is looked up by whichever key the caller keys accounts on — the internal name
+		// or the bare one — so a template gets the right login however the maps were built.
+		account := accounts[name]
+		if account == "" {
+			account = accounts[bare]
+		}
+		out = append(out, rosterEntry{Name: bare, FQDN: internal, Address: addresses[name], Account: account})
+	}
+	return out
+}
+
+// meshName is a machine's internal name and its bare one, from either. The control plane keys
+// the names it hands a resolution by the internal name (`homer.internal`), the same map a
+// container gets as its hosts; a caller that keys by the bare name gets the same answer. The
+// suffix is the one the control plane composed those names with, handed down rather than written
+// here a second time — the alternative was `homer.internal.internal` on every machine.
+func meshName(name, suffix string) (internal, bare string) {
+	dotted := "." + strings.TrimPrefix(suffixOr(suffix), ".")
+	if strings.HasSuffix(name, dotted) {
+		return name, strings.TrimSuffix(name, dotted)
+	}
+	return name + dotted, name
+}
+
+// suffixOr is the suffix given, or the one the mesh composes names with when none was handed down.
+// The one place the default is written, so a fact and a name cannot disagree about it.
+func suffixOr(suffix string) string {
+	if suffix == "" {
+		return "internal"
+	}
+	return suffix
+}
+
+func sortedNames(addresses map[string]string) []string {
+	out := make([]string, 0, len(addresses))
+	for name, at := range addresses {
+		// A machine the mesh cannot place is left out rather than named at nothing.
+		if at == "" {
+			continue
+		}
+		out = append(out, name)
+	}
+	sort.Strings(out)
+	return out
+}
@@ -0,0 +1,260 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// Keyed by the internal name, as the control plane hands them (issue 079). bart has no address —
+// the ordinary state between adding a machine and it joining.
+var threeMachines = map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2", "bart.internal": ""}
+
+// A module says where it wants a roster file and in what format, and is given the rendered file.
+func TestAModuleIsGivenTheFileItAskedFor(t *testing.T) {
+	m := Manifest{Module: "resolver", Facts: map[string]RosterFile{
+		"zones": {Path: "/etc/mesh/zones.conf", Template: "{{range .Machines}}address=/{{.FQDN}}/{{.Address}}\n{{end}}"},
+	}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, threeMachines, threeMachines, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(given) != 1 {
+		t.Fatalf("expected one file, got %d", len(given))
+	}
+	if given[0]["path"] != "/etc/mesh/zones.conf" || given[0]["type"] != "file" {
+		t.Fatalf("not written where it was asked for: %v", given[0])
+	}
+	// The id is fact-<name>, which is what a restart-on names when the roster changes.
+	if given[0]["id"] != "fact-zones" {
+		t.Fatalf("the file's id is not fact-<name>, so a restart-on cannot find it: %v", given[0]["id"])
+	}
+	if !strings.Contains(given[0]["content"].(string), "address=/homer.internal/10.42.0.1") {
+		t.Fatalf("the file does not hold the fact: %v", given[0]["content"])
+	}
+}
+
+// **A shared fact is written into a region of the machine's file, not over it** (novox/hq issue
+// 128). A hosts file is the machine's — its localhost, the operator's lines, other tools' blocks —
+// so the mesh owns only a marked region (`into: block`); a resolver's zones file is the mesh's
+// whole, and carries no `into`.
+func TestASharedFactIsWrittenIntoARegion(t *testing.T) {
+	roster := map[string]string{"homer.internal": "10.42.0.1"}
+	m := Manifest{Module: "net", Facts: map[string]RosterFile{
+		"node-names": {Path: "/etc/hosts", Template: "{{range .Names}}{{.FQDN}}\n{{end}}", Shared: true},
+		"node-zones": {Path: "/etc/zones", Template: "{{range .Machines}}{{.FQDN}}\n{{end}}"},
+	}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, roster, roster, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	by := map[string]map[string]any{}
+	for _, f := range given {
+		by[f["path"].(string)] = f
+	}
+	if by["/etc/hosts"]["into"] != "block" {
+		t.Fatalf("a shared fact is not written into a region, so the mesh writes the file whole: %v", by["/etc/hosts"])
+	}
+	if _, has := by["/etc/zones"]["into"]; has {
+		t.Fatalf("an unshared fact was written into a region, so the mesh does not own its own file whole: %v", by["/etc/zones"])
+	}
+}
+
+// **The format is the module's — the mesh renders whatever template it gives.** The same roster
+// through two templates is two entirely different files, and the control plane reads neither.
+func TestTheFormatIsTheModulesOwn(t *testing.T) {
+	roster := map[string]string{"homer.internal": "10.42.0.1"}
+	hostsish := Manifest{Module: "a", Facts: map[string]RosterFile{
+		"f": {Path: "/f", Template: "{{range .Names}}{{.Address}}\t{{.Name}}\n{{end}}"}}}
+	sshish := Manifest{Module: "b", Facts: map[string]RosterFile{
+		"f": {Path: "/f", Template: "{{range .Names}}Host {{.Name}}\n  HostName {{.FQDN}}\n{{end}}"}}}
+
+	h, err := FactsInto(hostsish, Resolution{Node: "homer"}, roster, roster, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	s, err := FactsInto(sshish, Resolution{Node: "homer"}, roster, roster, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if h[0]["content"] != "10.42.0.1\thomer\n" {
+		t.Fatalf("the hosts-shaped template did not render its format: %q", h[0]["content"])
+	}
+	if s[0]["content"] != "Host homer\n  HostName homer.internal\n" {
+		t.Fatalf("the ssh-shaped template did not render its format: %q", s[0]["content"])
+	}
+}
+
+// **A template that will not parse is refused here, not on a machine.** A daemon that starts, reads
+// a file the mesh could not render, and answers nothing is a much worse way to find out.
+func TestABrokenTemplateIsRefusedHere(t *testing.T) {
+	m := Manifest{Module: "resolver", Facts: map[string]RosterFile{
+		"zones": {Path: "/etc/zones", Template: "{{range .Machines}}oops"}}}
+	_, err := FactsInto(m, Resolution{}, nil, nil, nil, "")
+	if err == nil {
+		t.Fatal("a template that does not parse was accepted, so the machine gets an empty file")
+	}
+	if !strings.Contains(err.Error(), "resolver") || !strings.Contains(err.Error(), "zones") {
+		t.Fatalf("the refusal does not say whose template, or which: %v", err)
+	}
+}
+
+// A template reading something the mesh does not compute is refused, not rendered empty. The roster
+// is a closed shape; asking it for the weather fails where the manifest is.
+func TestATemplateReadingWhatTheMeshDoesNotHaveIsRefused(t *testing.T) {
+	m := Manifest{Module: "resolver", Facts: map[string]RosterFile{
+		"zones": {Path: "/etc/zones", Template: "{{.Weather}}"}}}
+	if _, err := FactsInto(m, Resolution{}, nil, nil, nil, ""); err == nil {
+		t.Fatal("a template read a field nobody computes and rendered anyway, silently")
+	}
+}
+
+// A relative path is refused, or a module decides where the mesh writes on a machine.
+func TestAFactMustBeAskedForAtAnAbsolutePath(t *testing.T) {
+	m := Manifest{Module: "resolver", Facts: map[string]RosterFile{
+		"hosts": {Path: "etc/hosts", Template: "x"}}}
+	if _, err := FactsInto(m, Resolution{}, nil, nil, nil, ""); err == nil {
+		t.Fatal("a relative path was accepted")
+	}
+}
+
+// A machine the mesh has a record for and cannot place is left out of the roster.
+//
+// **Not an oversight — the alternative is worse.** A name written with no address resolves to
+// nothing, and a connection to that hangs. Leaving it out fails at once and says the name is
+// unknown, which is a thing somebody can act on.
+func TestAMachineWithNoAddressIsNotInTheRoster(t *testing.T) {
+	m := Manifest{Module: "a", Facts: map[string]RosterFile{
+		"f": {Path: "/f", Template: "{{range .Machines}}{{.Name}}\n{{end}}"}}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, threeMachines, threeMachines, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(given[0]["content"].(string), "bart") {
+		t.Fatalf("a machine with no address was in the roster, so its name resolves to nothing:\n%s", given[0]["content"])
+	}
+}
+
+// **The names the control plane hands a resolution are already internal names** — `homer.internal`,
+// the same map every container gets as its hosts. A roster entry's FQDN is that name, not it with
+// the suffix appended a second time; either key gives the same entries.
+func TestNamesAreNotSuffixedTwice(t *testing.T) {
+	internal := map[string]string{"homer.internal": "10.42.0.1"}
+	bare := map[string]string{"homer": "10.42.0.1"}
+	tmpl := RosterFile{Path: "/f", Template: "{{range .Machines}}{{.FQDN}} {{.Name}}\n{{end}}"}
+
+	fromInternal, err := FactsInto(Manifest{Module: "a", Facts: map[string]RosterFile{"f": tmpl}}, Resolution{Node: "homer"}, internal, internal, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fromBare, err := FactsInto(Manifest{Module: "a", Facts: map[string]RosterFile{"f": tmpl}}, Resolution{Node: "homer"}, bare, bare, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fromInternal[0]["content"] != fromBare[0]["content"] {
+		t.Fatalf("the roster differs by how the names were keyed:\n%q\n%q", fromInternal[0]["content"], fromBare[0]["content"])
+	}
+	got := fromInternal[0]["content"].(string)
+	if strings.Contains(got, "internal.internal") || !strings.Contains(got, "homer.internal homer") {
+		t.Fatalf("the entry carries a doubled suffix or the wrong bare name:\n%s", got)
+	}
+}
+
+// The suffix the control plane composed the names with is the one a template sees — an operator who
+// chose another does not get `.internal`. `.Suffix` is the bare form, and FQDNs carry it.
+func TestTheSuffixIsCarriedAsComposed(t *testing.T) {
+	names := map[string]string{"homer.lan": "10.42.0.1"}
+	m := Manifest{Module: "a", Facts: map[string]RosterFile{
+		"f": {Path: "/f", Template: "local=/{{.Suffix}}/\n{{range .Machines}}{{.FQDN}}\n{{end}}"}}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, names, names, nil, "lan")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := given[0]["content"].(string)
+	if !strings.Contains(got, "local=/lan/") || strings.Contains(got, "internal") {
+		t.Fatalf("the operator's suffix was not carried, so its names would be wrong:\n%s", got)
+	}
+	if !strings.Contains(got, "homer.lan") {
+		t.Fatalf("the FQDN does not carry the operator's suffix:\n%s", got)
+	}
+}
+
+// novox/hq 04-ISSUES/111: a template is given both sets and chooses. `.Names` is every name the mesh
+// serves — the machines and the names it was told to route; `.Machines` is only the machines. A
+// container's hosts wants every name so a routed name resolves to the machine serving it; a resolver
+// told the suffix is its own wants only the machines, or a routed name written there with the suffix
+// is a name nobody will ever ask for, standing beside the machines and looking as real.
+func TestATemplateChoosesMachinesOrEveryName(t *testing.T) {
+	machines := map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2"}
+	every := map[string]string{
+		"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2",
+		"drive.example.test": "10.42.0.1", "git.example.test": "10.42.0.2",
+	}
+	m := Manifest{Module: "resolver", Facts: map[string]RosterFile{
+		"zones": {Path: "/etc/zones", Template: "{{range .Machines}}{{.FQDN}}\n{{end}}"},
+		"hosts": {Path: "/etc/hosts", Template: "{{range .Names}}{{.FQDN}}\n{{end}}"},
+	}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, every, machines, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	by := map[string]string{}
+	for _, f := range given {
+		by[f["path"].(string)] = f["content"].(string)
+	}
+
+	zones := by["/etc/zones"]
+	for _, served := range []string{"drive.example.test", "git.example.test"} {
+		if strings.Contains(zones, served) {
+			t.Fatalf("a template over .Machines saw %q, a name the mesh serves rather than a machine:\n%s", served, zones)
+		}
+	}
+	if !strings.Contains(zones, "homer.internal") {
+		t.Fatalf("a template over .Machines did not see the machines:\n%s", zones)
+	}
+
+	hosts := by["/etc/hosts"]
+	for _, name := range []string{"homer.internal", "drive.example.test", "git.example.test"} {
+		if !strings.Contains(hosts, name) {
+			t.Fatalf("a template over .Names did not see %q, so a container would not resolve it:\n%s", name, hosts)
+		}
+	}
+}
+
+// A home fact is placed under the operator account's home and chowned to it, and its template sees
+// each node's account (novox/hq to-be 29) — the ssh-client config is the case.
+func TestAHomeFactIsPlacedUnderTheAccountsHomeAndOwnedByIt(t *testing.T) {
+	names := map[string]string{"homer.internal": "10.42.0.1", "marge.internal": "10.42.0.2"}
+	accounts := map[string]string{"homer": "jo", "marge": "jo"}
+	m := Manifest{Module: "ssh-client", Facts: map[string]RosterFile{
+		"ssh-config": {Path: ".ssh/config.d/mesh", Home: true,
+			Template: "{{range .Names}}Host {{.Name}}\n  HostName {{.FQDN}}\n  User {{.Account}}\n{{end}}"}}}
+	given, err := FactsInto(m, Resolution{Node: "homer", Account: "jo"}, names, names, accounts, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f := given[0]
+	if f["path"] != "/home/jo/.ssh/config.d/mesh" {
+		t.Fatalf("the home fact was not placed under the account's home: %v", f["path"])
+	}
+	if f["owner"] != "jo" {
+		t.Fatalf("the home fact is not owned by the account: %v", f["owner"])
+	}
+	if !strings.Contains(f["content"].(string), "Host marge\n  HostName marge.internal\n  User jo") {
+		t.Fatalf("the config does not name the peer's account:\n%s", f["content"])
+	}
+}
+
+// A machine with no operator account gets no home fact — it cannot be placed, so it is left out
+// rather than written to nowhere.
+func TestAHomeFactIsSkippedWhereThereIsNoAccount(t *testing.T) {
+	names := map[string]string{"homer.internal": "10.42.0.1"}
+	m := Manifest{Module: "ssh-client", Facts: map[string]RosterFile{
+		"ssh-config": {Path: ".ssh/config", Home: true, Template: "x"}}}
+	given, err := FactsInto(m, Resolution{Node: "homer"}, names, names, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(given) != 0 {
+		t.Fatalf("a home fact was placed on a machine with no operator account: %v", given)
+	}
+}
@@ -13,7 +13,6 @@ func TestASeatPlaceholderAnswersWhereThisMachinePutTheHolder(t *testing.T) {
 		"type": "container", "id": "server", "name": "mesh-controller",
 		"env": map[string]any{
 			"MESH_STORE_INVENTORY_PORT": "${seat:mesh-store:5432}",
-			"MESH_BROKER_AMQP_PORT":     "${seat:mesh-broker:5672}",
 			"MESH_BROKER_ADDRESS_PORT":  "${seat:mesh-broker:5671}",
 			"MESH_STORE_INVENTORY_FILE": "/run/secrets/inventory",
 		},
@@ -27,7 +26,6 @@ func TestASeatPlaceholderAnswersWhereThisMachinePutTheHolder(t *testing.T) {
 	env := control["env"].(map[string]any)
 	for key, want := range map[string]string{
 		"MESH_STORE_INVENTORY_PORT": "6852",
-		"MESH_BROKER_AMQP_PORT":     "5679",
 		"MESH_BROKER_ADDRESS_PORT":  "5671",
 		"MESH_STORE_INVENTORY_FILE": "/run/secrets/inventory",
 	} {
@@ -146,7 +144,6 @@ func TestTheControlPlanesOwnAddressesFollowTheNodesPorts(t *testing.T) {
 		"MESH_STORE_INVENTORY_PORT":   "6852",
 		"MESH_STORE_IDENTITY_PORT":    "6852",
 		"MESH_STORE_LICENCES_PORT":    "6852",
-		"MESH_BROKER_AMQP_PORT":       "5679",
 		"MESH_BROKER_MANAGEMENT_PORT": "15673",
 		"MESH_BROKER_ADDRESS_PORT":    "5671",
 	} {
@@ -164,7 +161,7 @@ func TestTheControlPlanesOwnAddressesFollowTheNodesPorts(t *testing.T) {
 		t.Fatal(err)
 	}
 	env, _ = fileNamed(out, "mesh-controller.server")["env"].(map[string]any)
-	if env["MESH_STORE_INVENTORY_PORT"] != "" || env["MESH_BROKER_AMQP_PORT"] != "" {
+	if env["MESH_STORE_INVENTORY_PORT"] != "" {
 		t.Errorf("with no settings, the control plane is told %v", env)
 	}
 }
@@ -175,7 +172,6 @@ var SeatPorts = map[string]string{
 	"MESH_STORE_INVENTORY_PORT":   "${seat:mesh-store:5432}",
 	"MESH_STORE_IDENTITY_PORT":    "${seat:mesh-store:5432}",
 	"MESH_STORE_LICENCES_PORT":    "${seat:mesh-store:5432}",
-	"MESH_BROKER_AMQP_PORT":       "${seat:mesh-broker:5672}",
 	"MESH_BROKER_MANAGEMENT_PORT": "${seat:mesh-broker:15672}",
 	"MESH_BROKER_ADDRESS_PORT":    "${seat:mesh-broker:5671}",
 }
@@ -27,40 +27,144 @@ type Seat struct {
 	// provision may only be held by a module providing it at the seat's scope, and its holder is
 	// what a requirement for that provision resolves to when several modules provide it.
 	Delivers string
+	// Accepts, Emits and Serves are the protocol of the role, as local verbs — the same three a
+	// module declares for a seat of its own (novox/hq ADR 0118), and empty for most of these: a seat
+	// is usually about who does a job and not about what may be said to them.
+	//
+	// **Named here so the mesh has no role it cannot describe** (ADR 0121). Without them a build
+	// machine had three audiences for one outcome and nothing derived a grant for any of them, and an
+	// event about a role had nowhere to live but the namespace of whichever module held that role
+	// today — which the bus refuses, because a namespace belongs to who it is named for.
+	Accepts []string
+	Emits   []string
+	Serves  []string
 	// Decision is the record that made it a seat.
 	Decision string
 }

-// seats is the whole set, in the order a person reads it: the mesh's own, then a node's.
-var seats = []Seat{
+// defaultSeats is the set the mesh ships with — the seed for the control plane's seat table and the
+// fallback when it has none (novox/hq ADR 0122). It is the one place the closed set 0110 defines is
+// written; the store's table is seeded from it and thereafter is the live, editable copy.
+//
+// In the order a person reads it: the mesh's own, then a node's.
+var defaultSeats = []Seat{
 	{Name: "mesh-controller", Scope: ScopeMesh, Decision: "novox/hq ADR 0079"},
 	{Name: "mesh-store", Scope: ScopeMesh, Delivers: "postgres-database", Decision: "novox/hq ADR 0079"},
-	{Name: "mesh-broker", Scope: ScopeMesh, Delivers: "amqp", Decision: "novox/hq ADR 0079"},
+	// **Delivers the mesh's own bus, not `amqp`.** Those were the same word until
+	// ADR 0127 separated them: `amqp` is a backing service a module may require, and this seat is
+	// the mesh's own transport. ADR 0128 then made that connection something a module requires
+	// rather than receives ambiently — 23 of the catalogue's modules never speak, and an ambient
+	// connection would mint a credential for each.
+	{Name: "mesh-broker", Scope: ScopeMesh, Delivers: "mesh-bus", Decision: "novox/hq ADR 0079"},
 	{Name: "the-artifact-store", Scope: ScopeMesh, Delivers: "artifact-store", Decision: "novox/hq ADR 0075"},
-	{Name: "the-catalogue", Scope: ScopeMesh, Decision: "novox/hq ADR 0110"},
+	{Name: "mesh-catalog", Scope: ScopeMesh, Decision: "novox/hq ADR 0121"},
+	// Deferred renames (novox/hq ADR 0121): these deliver a provision, so renaming them is a
+	// delivering-seat migration with a mesh-wide cascade if a holder stops resolving mid-flight.
+	// They keep their names until that migration is done deliberately, apart from the node-* pass.
 	{Name: "npm-package-registry", Scope: ScopeMesh, Delivers: "npm-package-registry", Decision: "novox/hq ADR 0109"},
 	{Name: "git", Scope: ScopeMesh, Delivers: "git", Decision: "novox/hq ADR 0111"},
-	{Name: "the-build-machine", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
-	{Name: "the-dns-port", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
-	{Name: "the-intrusion-prevention", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
-	{Name: "the-packet-filter", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
+	// A build is work submitted to this role and its outcome is the role's own event (ADR 0129).
+	// One publish reaches whoever asked, the controller that records it, and the catalogue that
+	// places it in the graph — what the old bus's shared exchange did for free.
+	{Name: "mesh-build-machine", Scope: ScopeMesh,
+		Accepts: []string{"build"}, Emits: []string{"built"}, Decision: "novox/hq ADR 0121"},
+	{Name: "node-dns-resolver", Scope: ScopeNode, Decision: "novox/hq ADR 0121"},
+	{Name: "node-intrusion-prevention", Scope: ScopeNode, Decision: "novox/hq ADR 0121"},
+	{Name: "node-packet-filter", Scope: ScopeNode, Decision: "novox/hq ADR 0121"},
+	// Deferred (novox/hq ADR 0121): renaming to mesh-private-network is a scope + server/client
+	// model change, not a rename, so it stays until that is built.
 	{Name: "the-private-network", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
-	{Name: "the-resolver-configuration", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
-	{Name: "the-showcase", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},
+	{Name: "node-resolver-config", Scope: ScopeNode, Decision: "novox/hq ADR 0121"},
+	// The program that manages the machine's own network. It delivers nothing: its holder only
+	// keeps the manager and the mesh from contradicting each other — the resolver file left to the
+	// mesh, the private network's interface left alone — and never declares a link, an address or
+	// a wireless network, because the link is the only channel a fix could arrive on. A seat
+	// rather than a condition in the resolver's module, so a machine running two managers is
+	// refused at assignment instead of found by the resolver being rewritten (novox/hq ADR 0117).
+	{Name: "node-uplink", Scope: ScopeNode, Decision: "novox/hq ADR 0117"},
 }

+// A system seat name is the control plane's namespace: `mesh-*` for a mesh-wide role, `node-*` for
+// a per-node one (novox/hq ADR 0121). A claim to a system name the mesh does not define is refused;
+// any other name is a module's own to define and claim. Some of the mesh's own seats predate this
+// convention and are not yet renamed (git, npm-package-registry, the-artifact-store,
+// the-private-network) — those are in the set, so they resolve by name, not by prefix.
+func isSystemSeatName(name string) bool {
+	return strings.HasPrefix(name, "mesh-") || strings.HasPrefix(name, "node-")
+}
+
+// seats is the working set the lookups read. It starts as the compiled defaults and is replaced by
+// what the control plane loaded from its store (novox/hq ADR 0122), so a change to the set is a
+// change to data, not to this code.
+var seats = defaultSeats
+
+// DefaultSeats is the set the mesh ships with, for seeding the store's seat table.
+func DefaultSeats() []Seat { return append([]Seat(nil), defaultSeats...) }
+
+// UseSeats replaces the working set with the one the control plane read from its store.
+//
+// **Empty is ignored on purpose.** A store that has not been seeded yet — or one that could not be
+// read — must leave the compiled defaults in force rather than emptying the set: an empty set would
+// refuse every claim and could stop the control plane composing at all, which is a far worse failure
+// than running on the set the binary shipped with. So the store can only ever *replace* the set with
+// a non-empty one, never erase it.
+func UseSeats(s []Seat) {
+	if len(s) == 0 {
+		return
+	}
+	// **The store's rows carry no protocol yet, and the protocol is what the bus is derived
+	// from.** ADR 0129 gives a seat what it accepts, emits and serves; ADR 0122 moved the set into
+	// a table that has name, scope, delivers and decision and nothing else, and the columns for
+	// the rest are not there yet. So a row replacing a compiled entry would silently drop the
+	// protocol, and the roles' work queues would never be raised — found live as "no response
+	// from stream" the first time a build was submitted over the new bus (2026-09-28). Until the
+	// table gains the columns, a row without a protocol keeps the compiled one of the same name.
+	byName := map[string]Seat{}
+	for _, d := range defaultSeats {
+		byName[d.Name] = d
+	}
+	merged := make([]Seat, 0, len(s))
+	for _, row := range s {
+		if len(row.Accepts)+len(row.Emits)+len(row.Serves) == 0 {
+			if d, known := byName[row.Name]; known {
+				row.Accepts, row.Emits, row.Serves = d.Accepts, d.Emits, d.Serves
+			}
+		}
+		merged = append(merged, row)
+	}
+	seats = merged
+}
+
+// aliases maps a seat's former names to its current canonical name (novox/hq ADR 0122). Loaded from
+// the store alongside the set, so a reference to a name a seat used to have — a manifest's claim, a
+// held record — still resolves to it after a rename, and nothing downstream has to change.
+var aliases = map[string]string{}
+
+// UseAliases replaces the former-name map with the one the control plane read from its store. Empty
+// is fine and ordinary: a mesh whose seats have never been renamed has no aliases.
+func UseAliases(m map[string]string) { aliases = m }
+
 // Seats is every seat the mesh defines, in reading order.
 func Seats() []Seat {
 	return append([]Seat(nil), seats...)
 }

-// SeatNamed is the seat a claim names, if the mesh defines one.
+// SeatNamed is the seat a name refers to, whether that is its current name or one it used to have
+// (novox/hq ADR 0122). A former name resolves to the seat's canonical row, so a rename breaks no
+// reference to the old name.
 func SeatNamed(name string) (Seat, bool) {
 	for _, s := range seats {
 		if s.Name == name {
 			return s, true
 		}
 	}
+	if canonical, aliased := aliases[name]; aliased {
+		for _, s := range seats {
+			if s.Name == canonical {
+				return s, true
+			}
+		}
+	}
 	return Seat{}, false
 }

@@ -77,35 +181,93 @@ func SeatDelivering(provision string) (Seat, bool) {
 	return Seat{}, false
 }

-// claimProblems is what is wrong with a manifest's claims against the set.
+// claimProblems is what is wrong with a manifest's claims and the seats it defines.
 //
-// Three refusals, each naming the seat: a seat the mesh does not define, a seat claimed at another
-// scope, and a seat that delivers a provision claimed by a module that does not provide it — which
-// would make the module the mesh's answer for something it cannot answer.
+// A claim is one of three things (novox/hq ADR 0121): a **system seat** the control plane defines —
+// checked for scope and, if it delivers a provision, that the claimant provides it; a **system name
+// the mesh does not define** (`mesh-*`/`node-*`) — refused, because that namespace is the control
+// plane's; or a **module-defined seat** — valid only when this manifest also declares it, since a
+// module may coordinate its own instances through a seat of its own but may not invent one by
+// claiming it. A module's own seat declaration may not sit in the system namespace or shadow a
+// system seat.
 func claimProblems(m Manifest) []string {
 	var problems []string
-	for _, c := range m.Claims {
-		seat, known := SeatNamed(c.Name)
-		if !known {
+
+	defined := map[string]SeatDeclaration{}
+	for _, d := range m.DefinesSeats {
+		if _, isSystem := SeatNamed(d.Name); isSystem || isSystemSeatName(d.Name) {
 			problems = append(problems, fmt.Sprintf(
-				"%s claims %q, which is not a seat this mesh defines (novox/hq ADR 0110) — "+
-					"the seats are: %s", m.Module, c.Name, seatNames()))
+				"%s defines a seat %q in the mesh's own namespace; a module's seat is named outside "+
+					"mesh-*/node-* (novox/hq ADR 0121)", m.Module, d.Name))
 			continue
 		}
-		if c.At() != seat.Scope {
-			problems = append(problems, fmt.Sprintf(
-				"%s claims %s at scope %q, and %s is a %s seat",
-				m.Module, c.Name, c.At(), c.Name, seat.Scope))
+		defined[d.Name] = d
+	}
+
+	for _, c := range m.Claims {
+		if _, known := SeatNamed(c.Name); known {
+			// **A seat's scope and what it delivers are not judged here** (novox/hq ADR 0122).
+			// This function runs wherever a manifest is parsed, and one of those places is the
+			// build machine, which has no store: there, `SeatNamed` answers from the set the
+			// binary shipped with, so a build would be refused for disagreeing with a compiled
+			// copy of data the control plane owns. Exactly that happened — a holder of the bus
+			// seat was refused for not providing what a stale compiled row said the seat
+			// delivered, while the store's own row said otherwise.
+			//
+			// Both checks moved to CatalogueProblems, which only ever runs in the control plane,
+			// after UseSeats has replaced the set with the store's.
+			continue
 		}
-		if seat.Delivers != "" && !providesAt(m, seat.Delivers, seat.Scope) {
+		if isSystemSeatName(c.Name) {
 			problems = append(problems, fmt.Sprintf(
-				"%s claims %s, whose holder answers for %q, and %s does not provide %q at %s scope",
-				m.Module, c.Name, seat.Delivers, m.Module, seat.Delivers, seat.Scope))
+				"%s claims %q, which is a seat in the mesh's own namespace (mesh-*/node-*) that it "+
+					"does not define (novox/hq ADR 0121) — the seats are: %s", m.Module, c.Name, seatNames()))
+			continue
+		}
+		d, ours := defined[c.Name]
+		if !ours {
+			// **A claim on a seat this manifest does not declare is not the parser's to judge.**
+			// A module may hold a seat another module declared — that is why ADR 0126 has callers
+			// name the seat and not its provider, so an implementation can be replaced without
+			// touching a caller. Whether the seat exists is a fact about the whole catalogue, so
+			// the refusal is at registration, where every declaration is in view
+			// (`CatalogueProblems`: "which no module declares and the mesh does not define").
+			continue
+		}
+		if c.At() != d.At() {
+			problems = append(problems, fmt.Sprintf(
+				"%s claims its own seat %s at scope %q, having declared it at %q",
+				m.Module, c.Name, c.At(), d.At()))
 		}
 	}
 	return problems
 }

+// CanHold is why a module could not hold a seat, or nothing: its definition must claim the seat at
+// the seat's scope, and provide what the seat delivers, if it delivers anything. The seat is the
+// store's row, so this is judged only where the store's set is loaded — at registration and in the
+// handover command (novox/hq ADR 0131), never in the parser.
+func CanHold(m Manifest, seat Seat) error {
+	var claimed *Claim
+	for i := range m.Claims {
+		if hs, ok := SeatNamed(m.Claims[i].Name); ok && hs.Name == seat.Name {
+			claimed = &m.Claims[i]
+		}
+	}
+	if claimed == nil {
+		return fmt.Errorf("%s does not claim %s", m.Module, seat.Name)
+	}
+	if claimed.At() != seat.Scope {
+		return fmt.Errorf("%s claims %s at scope %q, and %s is a %s seat",
+			m.Module, seat.Name, claimed.At(), seat.Name, seat.Scope)
+	}
+	if seat.Delivers != "" && !providesAt(m, seat.Delivers, seat.Scope) {
+		return fmt.Errorf("%s claims %s, whose holder answers for %q, and %s does not provide %q at %s scope",
+			m.Module, seat.Name, seat.Delivers, m.Module, seat.Delivers, seat.Scope)
+	}
+	return nil
+}
+
 func providesAt(m Manifest, provision, scope string) bool {
 	for _, o := range m.Provides {
 		if o.Name == provision && o.At() == scope {
@@ -136,7 +298,10 @@ func HolderAmong(provision string, providers []Provider, held []Held) (Provider,
 		return Provider{}, false
 	}
 	for _, h := range held {
-		if h.Claim != seat.Name || h.Scope != seat.Scope {
+		// Resolve the held claim to a seat rather than comparing names, so a record naming a seat's
+		// former name still matches it after a rename (novox/hq ADR 0122).
+		hs, ok := SeatNamed(h.Claim)
+		if !ok || hs.Name != seat.Name || h.Scope != seat.Scope {
 			continue
 		}
 		for _, p := range providers {
@@ -147,3 +312,18 @@ func HolderAmong(provision string, providers []Provider, held []Held) (Provider,
 	}
 	return Provider{}, false
 }
+
+// SeatsWithAProtocol are the mesh's own seats that say something about what may be said to them or by
+// them, which is the set the bus derives streams, consumers and permissions from.
+//
+// Most of the set is not here, and that is the ordinary case: a seat saying only who does a job grants
+// nothing on the bus and needs no queue.
+func SeatsWithAProtocol() []Seat {
+	var out []Seat
+	for _, s := range seats {
+		if len(s.Accepts) > 0 || len(s.Emits) > 0 || len(s.Serves) > 0 {
+			out = append(out, s)
+		}
+	}
+	return out
+}
@@ -0,0 +1,247 @@
+package catalogue
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Seats a module declares of its own (novox/hq ADR 0118).
+//
+// The set of seats a mesh has is **derived**: the mesh's own, in seats.go, plus those declared by
+// every module it has registered. Still closed — a seat named nowhere is refused — but computed
+// from the catalogue rather than written in the controller, which is what ADR 0110 actually
+// needed and a hand-maintained table could not keep. Its own evidence: the enumeration done by
+// hand while that record was written reported eleven claims where there were thirteen.
+//
+// **What can be checked from one manifest and what cannot.** A declaration's shape, its scope,
+// and the reserved prefix are facts about the manifest in front of you. Whether a seat anybody
+// names actually exists, whether two modules declared the same one, and whether a holder
+// satisfies the protocol are facts about the *catalogue* — so they are checked at registration,
+// by CatalogueProblems, which is the last moment the mesh can still say no.
+
+// meshSeatPrefix is reserved to the mesh. The prefix *is* the reservation rule: no list of
+// reserved names to maintain, no way for the mesh's own namespace to be colonised by a manifest,
+// and nothing to keep in step when a mesh seat is added.
+const meshSeatPrefix = "mesh-"
+
+// A SeatDeclaration is a role a module offers on the bus: what may be sent to it, what it says,
+// and what it answers. A caller declares that it uses the *seat*, never the module, so the
+// implementation can be replaced under it.
+type SeatDeclaration struct {
+	Name  string `json:"name"`
+	Scope string `json:"scope,omitempty"`
+
+	// Accepts are the verbs others may submit work on. Each becomes a work-queue subject, and
+	// the holder is the only consumer — so exactly one worker does the job, by construction
+	// rather than by how carefully somebody wrote a subscribe call.
+	Accepts []string `json:"accepts,omitempty"`
+	// Emits are the verbs the holder publishes: 1:many, nobody obliged to act.
+	Emits []string `json:"emits,omitempty"`
+	// Serves are the verbs the holder answers: request and reply, awaited.
+	Serves []string `json:"serves,omitempty"`
+
+	// RetainSeconds is how long the inbound backlog survives with no holder, zero for the
+	// mesh's default. Retention belongs to whoever owns the namespace (design 29 §3) — a seat
+	// owns its own, which is why a seat is also the answer for a module that needs retention
+	// its events cannot have.
+	RetainSeconds int `json:"retain-seconds,omitempty"`
+}
+
+// At is this declaration's scope, with the default applied. Mesh by default, because a seat
+// declared by a module is nearly always "there is one of these in the mesh" — a per-node worker
+// is the deliberate case, and says so.
+func (s SeatDeclaration) At() string {
+	if s.Scope == "" {
+		return ScopeMesh
+	}
+	return s.Scope
+}
+
+// verbs is everything the protocol names, for the checks that do not care which half.
+func (s SeatDeclaration) verbs() []string {
+	out := append([]string{}, s.Accepts...)
+	out = append(out, s.Emits...)
+	return append(out, s.Serves...)
+}
+
+// declaredSeatProblems is what one manifest can be judged on alone.
+func declaredSeatProblems(m Manifest) []string {
+	var problems []string
+	seen := map[string]bool{}
+
+	for _, s := range m.DefinesSeats {
+		switch {
+		case s.Name == "":
+			problems = append(problems, fmt.Sprintf("%s declares a seat with no name", m.Module))
+			continue
+		case !name.MatchString(s.Name):
+			problems = append(problems, fmt.Sprintf(
+				"%s declares a seat named %q, which is not a usable name", m.Module, s.Name))
+			continue
+		case strings.HasPrefix(s.Name, meshSeatPrefix):
+			// The mesh's own code dereferences its seats by name — the resolver *is* the thing
+			// that finds the store — so the prefix is not a convention, it is a namespace.
+			problems = append(problems, fmt.Sprintf(
+				"%s declares a seat named %q; %q is reserved to the mesh, which defines its own "+
+					"seats (novox/hq ADR 0118)", m.Module, s.Name, meshSeatPrefix+"*"))
+			continue
+		}
+		if seen[s.Name] {
+			problems = append(problems, fmt.Sprintf(
+				"%s declares the seat %q twice", m.Module, s.Name))
+			continue
+		}
+		seen[s.Name] = true
+
+		if _, isMesh := SeatNamed(s.Name); isMesh {
+			problems = append(problems, fmt.Sprintf(
+				"%s declares %q, which is a seat the mesh already defines", m.Module, s.Name))
+		}
+		switch s.At() {
+		case ScopeNode, ScopeSite, ScopeMesh:
+		default:
+			problems = append(problems, fmt.Sprintf(
+				"%s declares seat %s at scope %q; a seat is held per node, per site or per mesh",
+				m.Module, s.Name, s.Scope))
+		}
+		// A seat with an empty protocol is allowed, and is the mesh saying what a machine is:
+		// which module is this node's packet filter, or its showcase. Design 26 calls it a seat
+		// that delivers nothing, and that is most of the node-scoped ones. ADR 0126's "a declared
+		// seat carries a protocol" governs what a holder must satisfy, not that every seat offers
+		// something — a marker seat's protocol is satisfied by holding it. Nothing can reach this
+		// state by accident: a mistyped field name is refused by the parser above, so an empty
+		// protocol was written as one.
+		for _, v := range s.verbs() {
+			if !name.MatchString(v) {
+				problems = append(problems, fmt.Sprintf(
+					"%s declares %s.%s, which is not a usable verb", m.Module, s.Name, v))
+			}
+		}
+	}
+
+	for _, u := range m.Uses {
+		if !name.MatchString(u) {
+			problems = append(problems, fmt.Sprintf("%s uses %q, which is not a usable seat name", m.Module, u))
+		}
+	}
+	return problems
+}
+
+// A Shelf is every manifest the mesh has registered, by module name.
+type Shelf map[string]Manifest
+
+// CatalogueProblems are the rules no single manifest can be judged against.
+//
+// Run at registration, which is the last moment the mesh can still refuse: after it, a caller is
+// bound to a seat and a refusal is an outage rather than a conversation.
+func CatalogueProblems(shelf Shelf) []string {
+	var problems []string
+
+	// Who declares what, and who declared it first.
+	declaredBy := map[string]string{}
+	declared := map[string]SeatDeclaration{}
+	for _, module := range shelfOrder(shelf) {
+		for _, s := range shelf[module].DefinesSeats {
+			if s.Name == "" {
+				continue
+			}
+			if first, taken := declaredBy[s.Name]; taken {
+				// The second loses. A seat name meaning two different protocols is the failure
+				// nobody could diagnose afterwards — a caller would bind to whichever happened
+				// to register first, and the symptom would appear in the other module.
+				problems = append(problems, fmt.Sprintf(
+					"%s declares the seat %q, which %s already declares; a seat name means one "+
+						"protocol", module, s.Name, first))
+				continue
+			}
+			declaredBy[s.Name] = module
+			declared[s.Name] = s
+		}
+	}
+
+	exists := func(seat string) bool {
+		if _, isMesh := SeatNamed(seat); isMesh {
+			return true
+		}
+		_, ok := declaredBy[seat]
+		return ok
+	}
+
+	for _, module := range shelfOrder(shelf) {
+		m := shelf[module]
+
+		// A `uses` naming nothing is where ADR 0110's guarantee lands under a derived set: the
+		// same refusal, at the same moment, from a set nobody maintains by hand.
+		for _, u := range m.Uses {
+			if !exists(u) {
+				problems = append(problems, fmt.Sprintf(
+					"%s uses the seat %q, which no module declares and the mesh does not define",
+					module, u))
+			}
+		}
+
+		for _, c := range m.Claims {
+			if !exists(c.Name) {
+				problems = append(problems, fmt.Sprintf(
+					"%s claims the seat %q, which no module declares and the mesh does not define",
+					module, c.Name))
+				continue
+			}
+			s, isModuleSeat := declared[c.Name]
+			if !isModuleSeat {
+				// **A mesh seat is judged here and nowhere else** (novox/hq ADR 0122): the set is
+				// the store's, and this is the only place that runs with the store's set loaded.
+				// The parser cannot do it — it also runs on the build machine, against whatever
+				// set that binary was compiled with.
+				seat, _ := SeatNamed(c.Name)
+				if err := CanHold(m, seat); err != nil {
+					problems = append(problems, err.Error())
+				}
+				continue
+			}
+			if c.At() != s.At() {
+				problems = append(problems, fmt.Sprintf(
+					"%s claims %s at scope %q, and %s declares it at %s",
+					module, c.Name, c.At(), declaredBy[c.Name], s.At()))
+			}
+			// A holder that does not answer what the seat promises is a caller's timeout, found
+			// at assignment instead.
+			if missing := unserved(m, s); len(missing) > 0 {
+				problems = append(problems, fmt.Sprintf(
+					"%s claims %s but does not serve %s, which that seat's protocol promises",
+					module, c.Name, strings.Join(missing, ", ")))
+			}
+		}
+	}
+	sort.Strings(problems)
+	return problems
+}
+
+// unserved is what a seat's protocol promises and the claimant does not answer. Only the tools
+// are checked: `accepts` and `emits` are wired by the runtime from the declaration, while a tool
+// is code the module either has or has not written.
+func unserved(m Manifest, s SeatDeclaration) []string {
+	has := map[string]bool{}
+	for _, t := range m.Tools {
+		has[t] = true
+	}
+	var missing []string
+	for _, t := range s.Serves {
+		if !has[t] {
+			missing = append(missing, t)
+		}
+	}
+	return missing
+}
+
+// shelfOrder is the catalogue in a stable order, so two runs report the same problems in the same
+// sequence — a refusal that reorders itself is a refusal nobody can diff.
+func shelfOrder(shelf Shelf) []string {
+	out := make([]string, 0, len(shelf))
+	for k := range shelf {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
@@ -0,0 +1,146 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+func problemsFor(t *testing.T, shelf Shelf) string {
+	t.Helper()
+	return strings.Join(CatalogueProblems(shelf), "; ")
+}
+
+func telegram() Manifest {
+	return Manifest{Module: "telegram", Tools: []string{"status"}, DefinesSeats: []SeatDeclaration{{
+		Name: "telegram-sender", Scope: ScopeMesh,
+		Accepts: []string{"send"}, Emits: []string{"delivered", "failed"}, Serves: []string{"status"},
+	}}, Claims: []Claim{{Name: "telegram-sender", Scope: ScopeMesh}}}
+}
+
+// The whole point: a module contributes a capability without the mesh being changed.
+func TestAModuleDeclaresItsOwnSeatAndHoldsIt(t *testing.T) {
+	shop := Manifest{Module: "shop", Uses: []string{"telegram-sender"}}
+	if got := problemsFor(t, Shelf{"telegram": telegram(), "shop": shop}); got != "" {
+		t.Fatalf("a declared seat and its caller were refused: %s", got)
+	}
+}
+
+// The prefix is the reservation rule, so there is no list to maintain and none to drift.
+func TestAModuleCannotDeclareAMeshSeat(t *testing.T) {
+	for _, n := range []string{"mesh-broker", "mesh-anything", "mesh-store"} {
+		m := Manifest{Module: "impostor", DefinesSeats: []SeatDeclaration{{Name: n, Accepts: []string{"x"}}}}
+		got := strings.Join(declaredSeatProblems(m), "; ")
+		if !strings.Contains(got, "reserved to the mesh") {
+			t.Fatalf("%q was accepted as a module's seat: %q", n, got)
+		}
+	}
+}
+
+// A seat name meaning two protocols is the failure nobody could diagnose afterwards.
+func TestTwoModulesCannotDeclareTheSameSeat(t *testing.T) {
+	other := Manifest{Module: "aardvark", DefinesSeats: []SeatDeclaration{{
+		Name: "telegram-sender", Scope: ScopeMesh, Accepts: []string{"something-else"}}}}
+	got := problemsFor(t, Shelf{"telegram": telegram(), "aardvark": other})
+	if !strings.Contains(got, "already declares") {
+		t.Fatalf("both declarations stood: %s", got)
+	}
+	// The first declarer keeps it; only the second is refused.
+	if strings.Count(got, "already declares") != 1 {
+		t.Fatalf("expected exactly one refusal: %s", got)
+	}
+}
+
+// Where ADR 0110's guarantee lands under a derived set: a typo is refused, not resolved to
+// nothing at runtime.
+func TestUsingASeatNobodyDeclaresIsRefused(t *testing.T) {
+	shop := Manifest{Module: "shop", Uses: []string{"telegram-sendr"}}
+	got := problemsFor(t, Shelf{"telegram": telegram(), "shop": shop})
+	if !strings.Contains(got, "telegram-sendr") || !strings.Contains(got, "no module declares") {
+		t.Fatalf("a misspelled seat was accepted: %s", got)
+	}
+}
+
+// A holder that does not answer what the seat promises is a caller's timeout, found here instead.
+func TestAHolderMustServeWhatItsSeatPromises(t *testing.T) {
+	m := telegram()
+	m.Tools = nil // declares the seat, serves none of it
+	got := problemsFor(t, Shelf{"telegram": m})
+	if !strings.Contains(got, "does not serve status") {
+		t.Fatalf("a holder was accepted that answers nothing its seat promises: %s", got)
+	}
+}
+
+// A seat with no protocol is a marker: which module is this node's showcase, or its packet filter.
+// Most node-scoped seats are markers, so refusing one would refuse the majority of the set.
+func TestASeatWithoutAProtocolIsAMarkerNotAMistake(t *testing.T) {
+	m := Manifest{Module: "vague", DefinesSeats: []SeatDeclaration{{Name: "something", Scope: ScopeNode}}}
+	if got := strings.Join(declaredSeatProblems(m), "; "); got != "" {
+		t.Fatalf("a marker seat was refused: %s", got)
+	}
+}
+
+// A claim at the wrong scope is a different seat than the one declared.
+func TestAClaimMustMatchTheDeclaredScope(t *testing.T) {
+	m := telegram()
+	m.Claims = []Claim{{Name: "telegram-sender", Scope: ScopeNode}}
+	got := problemsFor(t, Shelf{"telegram": m})
+	if !strings.Contains(got, "scope") {
+		t.Fatalf("a claim at the wrong scope was accepted: %s", got)
+	}
+}
+
+// The mesh's own seats still work, and are not shadowed by the derived half.
+func TestTheMeshsOwnSeatsAreStillClaimable(t *testing.T) {
+	// It delivers the bus, so its holder provides the bus — the rule this check now enforces.
+	m := Manifest{Module: "nats",
+		Provides: []Offer{{Name: "mesh-bus", Scope: ScopeMesh}},
+		Claims:   []Claim{{Name: "mesh-broker", Scope: ScopeMesh}}}
+	if got := problemsFor(t, Shelf{"nats": m}); got != "" {
+		t.Fatalf("a mesh seat was refused by the derived check: %s", got)
+	}
+}
+
+// A refusal that reorders itself between runs is a refusal nobody can diff.
+func TestTheProblemsAreStable(t *testing.T) {
+	shelf := Shelf{"telegram": telegram(), "shop": {Module: "shop", Uses: []string{"nope"}},
+		"other": {Module: "other", Uses: []string{"also-nope"}}}
+	first, second := problemsFor(t, shelf), problemsFor(t, shelf)
+	if first != second {
+		t.Fatalf("unstable:\n%s\n%s", first, second)
+	}
+}
+
+// **A build machine has no store, so it may not judge a seat.** The set is data the control plane
+// owns (novox/hq ADR 0122), and `ParseManifest` runs on the build machine too, against whatever set
+// that binary was compiled with. When the two disagreed, a valid holder of the bus seat was refused
+// mid-rollout — the compiled row said the seat delivered one provision, the store's row said
+// another, and the build failed on the copy rather than the truth. The parser judges the manifest;
+// the seat set judges the claim, where it is loaded.
+func TestTheParserDoesNotJudgeWhatOnlyTheStoreKnows(t *testing.T) {
+	was := Seats()
+	t.Cleanup(func() { UseSeats(was) })
+
+	// A store whose bus seat delivers something this module does provide.
+	UseSeats([]Seat{{Name: "mesh-broker", Scope: ScopeMesh, Delivers: "mesh-bus", Decision: "test"}})
+	raw := []byte(`{"module":"a-bus","version":"1",` +
+		`"provides":[{"name":"mesh-bus","scope":"mesh"}],` +
+		`"claims":[{"name":"mesh-broker","scope":"mesh"}]}`)
+
+	m, err := ParseManifest(raw)
+	if err != nil {
+		t.Fatalf("the parser refused a claim only the seat set can judge: %v", err)
+	}
+	if got := CatalogueProblems(Shelf{m.Module: m}); len(got) != 0 {
+		t.Fatalf("a holder that provides what the store says the seat delivers was refused: %v", got)
+	}
+
+	// And with the store saying the seat delivers something else, registration is what refuses it.
+	UseSeats([]Seat{{Name: "mesh-broker", Scope: ScopeMesh, Delivers: "other-bus", Decision: "test"}})
+	if _, err := ParseManifest(raw); err != nil {
+		t.Fatalf("the parser judged it the second time: %v", err)
+	}
+	got := strings.Join(CatalogueProblems(Shelf{m.Module: m}), "; ")
+	if !strings.Contains(got, `does not provide "other-bus"`) {
+		t.Fatalf("registration did not refuse a holder that cannot answer for the seat: %q", got)
+	}
+}
@@ -50,44 +50,120 @@ func TestTheSeatsAreAClosedSetAndEachNamesItsDecision(t *testing.T) {
 	}
 }

+// novox/hq ADR 0117: a machine's uplink is a seat, held per machine, and delivers nothing.
+//
+// **Nothing, because nothing may be required of it.** A holder only keeps its network manager from
+// contradicting the mesh; a requirement resolving to it would make the manager the mesh's answer
+// for something, and the manager's link is the one thing the mesh must never be able to break.
+func TestTheUplinkIsANodeSeatThatDeliversNothing(t *testing.T) {
+	seat, known := SeatNamed("node-uplink")
+	if !known {
+		t.Fatalf("the uplink is not a seat; the seats are: %s", seatNames())
+	}
+	if seat.Scope != ScopeNode || seat.Delivers != "" || seat.Decision != "novox/hq ADR 0117" {
+		t.Fatalf("the uplink is %+v, not a node seat delivering nothing by ADR 0117", seat)
+	}
+	// And a manager's module can hold it without providing anything.
+	raw := []byte(`{"module":"networkmanager","version":"1","claims":[{"name":"node-uplink","scope":"node"}]}`)
+	if _, err := ParseManifest(raw); err != nil {
+		t.Fatalf("a network manager's module could not hold the uplink: %v", err)
+	}
+}
+
 func claimed(claims string) []byte {
 	return []byte(`{"module":"thing","version":"1","provides":[{"name":"npm-package-registry","scope":"mesh"}],"claims":` + claims + `}`)
 }

-func TestAClaimOnASeatTheMeshDoesNotDefineIsRefused(t *testing.T) {
-	_, err := ParseManifest(claimed(`[{"name":"the-anything","scope":"node"}]`))
-	if err == nil {
-		t.Fatal("a module invented a seat by claiming it")
+// **The refusal moved, it did not go** (novox/hq ADR 0118, superseding 0110). A module may now
+// declare its own seats, so whether a claimed seat exists is a fact about the *catalogue* and not
+// about the manifest in front of the parser: a claim on a seat another registered module declares
+// is perfectly good, and the parser cannot tell the two cases apart. So the parser accepts it and
+// registration refuses it — the same guarantee, at the same moment work would otherwise start,
+// from a set nobody maintains by hand.
+func TestAClaimOnASeatNobodyDeclaresIsRefusedAtRegistration(t *testing.T) {
+	m, err := ParseManifest(claimed(`[{"name":"the-anything","scope":"node"}]`))
+	if err != nil {
+		t.Fatalf("the parser judged a claim it cannot judge alone: %v", err)
 	}
-	if !strings.Contains(err.Error(), "the-anything") || !strings.Contains(err.Error(), "not a seat") {
-		t.Fatalf("the refusal does not say the seat is unknown: %v", err)
+
+	problems := CatalogueProblems(Shelf{m.Module: m})
+	if len(problems) == 0 {
+		t.Fatal("a module invented a seat by claiming it, and registration allowed it")
 	}
-	// And it says what the seats are, because "no" without the list sends somebody reading code.
-	if !strings.Contains(err.Error(), "the-packet-filter") {
-		t.Fatalf("the refusal does not list the seats: %v", err)
+	joined := strings.Join(problems, "; ")
+	if !strings.Contains(joined, "the-anything") || !strings.Contains(joined, "no module declares") {
+		t.Fatalf("the refusal does not say the seat is nobody's: %v", problems)
 	}
 }

-func TestASeatClaimedAtAnotherScopeIsRefused(t *testing.T) {
-	_, err := ParseManifest(claimed(`[{"name":"npm-package-registry","scope":"node"}]`))
-	if err == nil {
-		t.Fatal("a mesh seat was held per node")
+// And the same claim is fine once something declares that seat, which is the case the parser
+// could not have distinguished.
+func TestAClaimOnASeatAnotherModuleDeclaresIsAccepted(t *testing.T) {
+	claimant, err := ParseManifest(claimed(`[{"name":"the-anything","scope":"node"}]`))
+	if err != nil {
+		t.Fatal(err)
 	}
-	if !strings.Contains(err.Error(), "mesh seat") {
-		t.Fatalf("the refusal does not say which scope the seat is: %v", err)
+	declarer := Manifest{Module: "someone", DefinesSeats: []SeatDeclaration{
+		{Name: "the-anything", Scope: ScopeNode, Accepts: []string{"work"}},
+	}}
+	if problems := CatalogueProblems(Shelf{claimant.Module: claimant, "someone": declarer}); len(problems) != 0 {
+		t.Fatalf("a claim on a declared seat was refused: %v", problems)
+	}
+}
+
+// A module may define its own seat and claim it — the mesh enforces exclusivity without knowing
+// what it means (novox/hq ADR 0121). But it may not define one in the mesh's own namespace.
+func TestAModuleDefinesAndClaimsItsOwnSeat(t *testing.T) {
+	ok := []byte(`{"module":"showcase","version":"1","seats":[{"name":"the-showcase","scope":"node"}],` +
+		`"claims":[{"name":"the-showcase","scope":"node"}]}`)
+	if _, err := ParseManifest(ok); err != nil {
+		t.Fatalf("a module could not define and claim its own seat: %v", err)
+	}
+	// Claiming a name nobody defines is still refused — but **at registration, not here**: with
+	// seats declared by modules, a claim on a seat *another* module declares is good, and the
+	// parser cannot tell that from an invented name. See
+	// TestAClaimOnASeatNobodyDeclaresIsRefusedAtRegistration.
+	claimant, err := ParseManifest(claimed(`[{"name":"the-anything","scope":"node"}]`))
+	if err != nil {
+		t.Fatalf("the parser judged a claim it cannot judge alone: %v", err)
+	}
+	if len(CatalogueProblems(Shelf{claimant.Module: claimant})) == 0 {
+		t.Fatal("a module claimed a seat nobody defines")
+	}
+	// A module may not carve its seat out of the mesh's own namespace.
+	bad := []byte(`{"module":"x","version":"1","seats":[{"name":"node-mine","scope":"node"}],` +
+		`"claims":[{"name":"node-mine","scope":"node"}]}`)
+	if _, err := ParseManifest(bad); err == nil || !strings.Contains(err.Error(), "own namespace") {
+		t.Fatalf("a module defined a seat in the mesh's namespace and was not refused: %v", err)
+	}
+}
+
+// **At registration, not in the parser** (novox/hq ADR 0122): a seat's scope is a property of the
+// set, the set is the store's, and the parser also runs on a build machine that has no store.
+func TestASeatClaimedAtAnotherScopeIsRefused(t *testing.T) {
+	m, err := ParseManifest(claimed(`[{"name":"npm-package-registry","scope":"node"}]`))
+	if err != nil {
+		t.Fatalf("the parser judged a scope it reads from data it may not have: %v", err)
+	}
+	got := strings.Join(CatalogueProblems(Shelf{m.Module: m}), "; ")
+	if !strings.Contains(got, "mesh seat") {
+		t.Fatalf("the refusal does not say which scope the seat is: %q", got)
 	}
 }

 func TestADeliveringSeatIsOnlyHeldByAModuleThatProvides(t *testing.T) {
 	// Holding it makes the module the mesh's answer for the provision. A module that cannot answer
 	// would be the answer anyway, and every consumer would be sent to it.
+	// And refused at registration, where the seat set is the store's: what a seat delivers is
+	// data, so a compiled copy of it may not be what refuses a build (novox/hq ADR 0122).
 	raw := []byte(`{"module":"thing","version":"1","claims":[{"name":"git","scope":"mesh"}]}`)
-	_, err := ParseManifest(raw)
-	if err == nil {
-		t.Fatal("a module holding the git seat need not provide git")
+	m, err := ParseManifest(raw)
+	if err != nil {
+		t.Fatalf("the parser judged what a seat delivers: %v", err)
 	}
-	if !strings.Contains(err.Error(), `does not provide "git"`) {
-		t.Fatalf("the refusal does not say what is missing: %v", err)
+	got := strings.Join(CatalogueProblems(Shelf{m.Module: m}), "; ")
+	if !strings.Contains(got, `does not provide "git"`) {
+		t.Fatalf("the refusal does not say what is missing: %q", got)
 	}
 }

@@ -206,3 +282,43 @@ func TestTheHolderIsTheModuleNotTheMachine(t *testing.T) {
 		t.Fatalf("the holder was not told apart from a neighbour: %+v", holder)
 	}
 }
+
+// The working set is loaded from the store, and an empty load never erases it (novox/hq ADR 0122).
+func TestUseSeatsReplacesTheSetButNeverEmptiesIt(t *testing.T) {
+	before := Seats()
+	defer UseSeats(DefaultSeats()) // restore for other tests, whatever this leaves it as
+
+	// An empty load (store not seeded, or unreadable) leaves the compiled defaults in force.
+	UseSeats(nil)
+	if len(Seats()) != len(before) {
+		t.Fatalf("an empty load changed the set from %d to %d seats", len(before), len(Seats()))
+	}
+	// A non-empty load replaces it — this is how a rename in the store reaches the lookups.
+	UseSeats([]Seat{{Name: "node-firewall", Scope: ScopeNode, Decision: "novox/hq ADR 0122"}})
+	if _, known := SeatNamed("node-firewall"); !known {
+		t.Fatal("the loaded set did not replace the working set")
+	}
+	if len(Seats()) != 1 {
+		t.Fatalf("the working set is %d seats, not the one that was loaded", len(Seats()))
+	}
+}
+
+// A former name resolves to the seat it was renamed from (novox/hq ADR 0122), so a manifest's claim
+// and a held record naming the old name break nothing after a rename.
+func TestAFormerNameResolvesAfterARename(t *testing.T) {
+	defer func() { UseSeats(DefaultSeats()); UseAliases(nil) }()
+	UseSeats([]Seat{{Name: "git", Scope: ScopeMesh, Delivers: "git", Decision: "novox/hq ADR 0121"}})
+	UseAliases(map[string]string{"git": "git"})
+
+	// The old name resolves to the renamed seat.
+	if s, ok := SeatNamed("git"); !ok || s.Name != "git" {
+		t.Fatalf("the former name did not resolve to the renamed seat: %+v ok=%v", s, ok)
+	}
+	// And a holder recorded under the old name is still found for the provision the seat delivers.
+	providers := []Provider{{Node: "anchor", At: "anchor.internal", Module: "gitea"}}
+	held := []Held{{Claim: "git", Scope: ScopeMesh, Node: "anchor", Module: "gitea"}}
+	holder, found := HolderAmong("git", providers, held)
+	if !found || holder.Module != "gitea" {
+		t.Fatalf("the holder recorded under the former name was not matched: %+v found=%v", holder, found)
+	}
+}
@@ -0,0 +1,46 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// The ssh-client module, composed as a machine receives it (novox/hq to-be 29): every other node's
+// Host block written into a marked region of the operator's ~/.ssh/config, owned by the account,
+// with ~/.ssh created 0700 — the operator's own config kept.
+func TestSSHClientOwnsTheOperatorsSSHConfig(t *testing.T) {
+	shelf := shelf(catalogueManifest(t, "ssh-client"))
+	got, err := Resolve(shelf, []string{"ssh-client"},
+		Node{Name: "homer", At: "homer.internal", Account: "jo"}, World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	names := map[string]string{"homer.internal": "10.10.0.1", "marge.internal": "10.10.0.2"}
+	out, err := got.Declaration(Rendering{
+		Names: names, Machines: names, Accounts: map[string]string{"homer": "jo", "marge": "jo"},
+		Suffix: "internal",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	by := map[string]map[string]any{}
+	for _, r := range out {
+		by[r["id"].(string)] = r
+	}
+
+	dir := by["ssh-client.ssh-dir"]
+	if dir == nil || dir["path"] != "/home/jo/.ssh" || dir["owner"] != "jo" || dir["mode"] != "0700" {
+		t.Fatalf("~/.ssh is not created 0700 owned by the account: %v", dir)
+	}
+	cfg := by["ssh-client.fact-ssh-config"]
+	if cfg == nil || cfg["path"] != "/home/jo/.ssh/config" || cfg["owner"] != "jo" || cfg["into"] != "block" {
+		t.Fatalf("the ssh config is not written into the operator's ~/.ssh/config as a region: %v", cfg)
+	}
+	body := cfg["content"].(string)
+	if !strings.Contains(body, "Host marge marge.internal") || !strings.Contains(body, "User jo") {
+		t.Fatalf("the config does not name the peer node and its account:\n%s", body)
+	}
+	if strings.Contains(body, "Host homer ") {
+		t.Fatalf("the config names the machine itself, not only its peers:\n%s", body)
+	}
+}
@@ -164,6 +164,41 @@ func (i *Inventory) Held(ctx context.Context) (map[string]string, error) {
 	return held, rows.Err()
 }

+// BuiltAgainst is what each module's newest successful build stood on, as recorded — the build
+// edges (ADR 0009). A module whose last build recorded no bases is absent, which is also what a
+// module standing on nothing looks like: an edge the mesh has not derived is not an edge.
+func (i *Inventory) BuiltAgainst(ctx context.Context) (map[string][]string, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select distinct on (module) module, built_against
+		   from build
+		  where module is not null and module <> '' and failed = ''
+		  order by module, at desc`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	against := map[string][]string{}
+	for rows.Next() {
+		var module string
+		var raw []byte
+		if err := rows.Scan(&module, &raw); err != nil {
+			return nil, err
+		}
+		if len(raw) == 0 {
+			continue
+		}
+		var refs []string
+		if err := json.Unmarshal(raw, &refs); err != nil {
+			continue
+		}
+		if len(refs) > 0 {
+			against[module] = refs
+		}
+	}
+	return against, rows.Err()
+}
+
 // manifestOrNil keeps the difference between "declared nothing" and "predates this being kept".
 //
 // A build recorded before the mesh kept manifests has no manifest, and that is not the same as one
@@ -0,0 +1,178 @@
+package inventory
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// What the bus's user list is derived from, read out of the mesh's records.
+//
+// The deriving itself is pure and lives in the broker package; this is the reading, and it is kept
+// apart for the reason that package keeps its own types: a permission must be a function of what a
+// module declared, and a query that decided anything would be a second place authority came from.
+
+// BusRecords is every fact the composer needs about who may reach the bus.
+//
+// **A module's authority comes from the manifest, not from the assignment.** The assignment says
+// *where* it runs; what it may say is in what it declared, so the two are read together and the
+// manifest is the one that decides.
+func (i *Inventory) BusRecords(ctx context.Context) (broker.Records, error) {
+	nodes, err := i.Nodes(ctx)
+	if err != nil {
+		return broker.Records{}, fmt.Errorf("cannot read the mesh's machines: %w", err)
+	}
+	declared, err := i.Catalogue(ctx)
+	if err != nil {
+		return broker.Records{}, fmt.Errorf("cannot read the catalogue: %w", err)
+	}
+
+	// Every seat any module declares, by name, so a module's claim can be resolved to the protocol
+	// that seat promises. **Across the whole catalogue, not one manifest**: a seat is declared by
+	// one module and held by another, which is the whole reason a seat exists (ADR 0118).
+	seats := map[string]catalogue.SeatDeclaration{}
+	for _, m := range declared {
+		for _, s := range m.DefinesSeats {
+			seats[s.Name] = s
+		}
+	}
+	// And the mesh's own, which carry protocol too (novox/hq ADR 0121). Added after the modules'
+	// rather than before, because a `mesh-*` name is the mesh's and registration refuses a module
+	// declaring one — so this cannot be shadowed, and if it ever were, the mesh's own would win.
+	for _, own := range catalogue.SeatsWithAProtocol() {
+		seats[own.Name] = catalogue.SeatDeclaration{
+			Name: own.Name, Scope: own.Scope,
+			Accepts: own.Accepts, Emits: own.Emits, Serves: own.Serves,
+		}
+	}
+
+	out := broker.Records{Assigned: map[string][]broker.Declared{}, People: map[string][]string{}}
+	for _, n := range nodes {
+		out.Nodes = append(out.Nodes, n.Name)
+		modules, err := i.Assigned(ctx, n.Name)
+		if err != nil {
+			return broker.Records{}, fmt.Errorf("cannot read what %s runs: %w", n.Name, err)
+		}
+		for _, module := range modules {
+			m, known := declared[module]
+			if !known {
+				// Assigned and not in the catalogue. Said rather than composed with no authority:
+				// a user with an empty permission list is a module that starts, connects, and is
+				// refused by the server on its first publish — an authorisation error that says
+				// nothing about a missing manifest.
+				//
+				// **The catalogue refuses to forget an assigned module, so this is the second line
+				// and not the first.** It earns its place there anyway: relying on another
+				// package's invariant is how a rule ends up enforced by nothing.
+				return broker.Records{}, fmt.Errorf(
+					"%s is assigned to %s and is not in the catalogue, so what it may say cannot "+
+						"be derived", module, n.Name)
+			}
+			out.Assigned[n.Name] = append(out.Assigned[n.Name], declaredFor(m, seats))
+		}
+	}
+
+	enrolling, err := i.NodesWithALiveToken(ctx)
+	if err != nil {
+		return broker.Records{}, err
+	}
+	out.Enrolling = enrolling
+
+	people, err := i.People(ctx)
+	if err != nil {
+		return broker.Records{}, err
+	}
+	for _, p := range people {
+		out.People[p.Name] = p.Invokes
+	}
+	return out, nil
+}
+
+// declaredFor is one module's manifest as the composer needs it: what it says about itself, and the
+// protocol of every seat it holds or uses.
+func declaredFor(m catalogue.Manifest, seats map[string]catalogue.SeatDeclaration) broker.Declared {
+	// A consumed name is a module's event unless it names a seat, and only somebody holding the seat
+	// set can tell (novox/hq ADR 0121). Split here, because the composer cannot look at a name and
+	// know — and a role's event read as a module's is a subscription to a namespace nobody owns.
+	var fromModules []string
+	var watches []broker.Seat
+	for _, c := range m.Consumes {
+		emitter, event, named := strings.Cut(c, ".")
+		if named {
+			if s, isASeat := seats[emitter]; isASeat {
+				watches = append(watches, broker.Seat{Name: s.Name, Emits: []string{event}})
+				continue
+			}
+		}
+		fromModules = append(fromModules, c)
+	}
+
+	d := broker.Declared{
+		Module:   m.Module,
+		Emits:    m.Emits,
+		Consumes: fromModules,
+		Watches:  watches,
+		// The tools it answers, which is `tools` and not `serves`: the manifest's `serves` is the
+		// facts a consumer needs to reach a provision, a different meaning under a similar word.
+		Serves: m.Tools,
+	}
+	for _, c := range m.Claims {
+		// Every seat with a protocol, the mesh's own included. One that says only who does a job is
+		// not here and grants nothing, which is most of them.
+		if s, hasAProtocol := seats[c.Name]; hasAProtocol {
+			d.Holds = append(d.Holds, asSeat(s))
+		}
+	}
+	for _, name := range m.Uses {
+		if s, declaredSomewhere := seats[name]; declaredSomewhere {
+			d.Uses = append(d.Uses, asSeat(s))
+		}
+	}
+	return d
+}
+
+func asSeat(s catalogue.SeatDeclaration) broker.Seat {
+	return broker.Seat{Name: s.Name, Accepts: s.Accepts, Emits: s.Emits, Serves: s.Serves}
+}
+
+// MeshSeats are the mesh's own seats that carry a protocol, as the bus needs them: what to make a work
+// queue for, and whose holder gets a worker on it (novox/hq ADR 0121).
+func MeshSeats() []broker.DeclaredSeat {
+	var out []broker.DeclaredSeat
+	for _, s := range catalogue.SeatsWithAProtocol() {
+		out = append(out, broker.DeclaredSeat{
+			Name: s.Name, Accepts: s.Accepts, Emits: s.Emits, Serves: s.Serves,
+		})
+	}
+	return out
+}
+
+// NodesWithALiveToken is every machine holding a token that could still be presented — issued, not
+// expired, not redeemed.
+//
+// **One enrolment user per such token** (design 25 §6): the inbox an answer goes to is scoped to the
+// token, because an answer carries that machine's credentials sealed to it and a shared inbox is one
+// machine able to read another's.
+func (i *Inventory) NodesWithALiveToken(ctx context.Context) ([]string, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select distinct n.name
+		   from enrolment_token t join node n on n.id = t.node
+		  where t.redeemed is null and t.expires > now()
+		  order by n.name`)
+	if err != nil {
+		return nil, fmt.Errorf("cannot read which machines hold a live token: %w", err)
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		out = append(out, name)
+	}
+	return out, rows.Err()
+}
@@ -0,0 +1,166 @@
+package inventory
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// Reading the bus's user list out of the mesh's records, against a real store.
+//
+// What each of these is about is a user that would be **missing or wrong in a way nothing reports**:
+// the server reads whatever file it is given, and a module whose user is absent fails on its first
+// publish with an authorisation error that says nothing about a missing assignment.
+
+func aMeshWith(t *testing.T, manifests ...catalogue.Manifest) (*Inventory, context.Context) {
+	t.Helper()
+	inv := ForTest(t)
+	ctx := context.Background()
+	for _, m := range manifests {
+		if err := inv.RegisterModule(ctx, m, Source{Repository: "/r"}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return inv, ctx
+}
+
+func theSeatDeclarer() catalogue.Manifest {
+	return catalogue.Manifest{
+		Module: "telegram", Version: "1",
+		DefinesSeats: []catalogue.SeatDeclaration{{
+			Name: "telegram-sender", Accepts: []string{"send"}, Emits: []string{"delivered"},
+		}},
+		Claims: []catalogue.Claim{{Name: "telegram-sender", Scope: catalogue.ScopeMesh}},
+	}
+}
+
+// A module assigned to a machine becomes a user with the authority its manifest declared — and the
+// protocol of a seat declared by a *different* module, which is the whole reason a seat exists.
+func TestAnAssignedModuleBecomesAUserWithWhatItDeclared(t *testing.T) {
+	shop := catalogue.Manifest{
+		Module: "shop", Version: "1",
+		Emits: []string{"order.placed"}, Tools: []string{"price"},
+		Uses: []string{"telegram-sender"},
+	}
+	inv, ctx := aMeshWith(t, theSeatDeclarer(), shop)
+	if _, err := inv.AddNode(ctx, "one"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.Assign(ctx, "one", "shop"); err != nil {
+		t.Fatal(err)
+	}
+
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	on := records.Assigned["one"]
+	if len(on) != 1 || on[0].Module != "shop" {
+		t.Fatalf("the machine's modules read as %+v", on)
+	}
+	if len(on[0].Uses) != 1 || on[0].Uses[0].Accepts[0] != "send" {
+		t.Fatalf("the seat it uses carries no protocol: %+v — so it would be granted nothing on a "+
+			"seat it was assigned to send to", on[0].Uses)
+	}
+	if len(on[0].Serves) != 1 || on[0].Serves[0] != "price" {
+		t.Fatalf("its tools read as %v, and a module that cannot subscribe its own tool subject "+
+			"serves nothing", on[0].Serves)
+	}
+
+	// And it derives into a user the server would accept.
+	users, err := broker.Users(records)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found bool
+	for _, u := range users {
+		if u.Username() != "one.shop" {
+			continue
+		}
+		found = true
+		perms, err := broker.PermissionsFor(u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		// Its tools are every one under its own name — the list in the manifest is a person's
+		// vocabulary for asking, not the module's permission to answer.
+		if !granted(perms.Publish, "mesh.mod.shop.event.order.placed") ||
+			!granted(perms.Publish, "mesh.seat.telegram-sender.accept.send") ||
+			!granted(perms.Subscribe, "mesh.mod.shop.tool.>") {
+			t.Fatalf("one.shop's authority is not what it declared: %+v", perms)
+		}
+	}
+	if !found {
+		t.Fatal("no user was derived for the assigned module")
+	}
+}
+
+// A machine holding a live token gets an enrolment user; one whose token is spent or expired does
+// not. **An enrolment user outliving its token is a right to join that nobody issued.**
+func TestOnlyAMachineWithALiveTokenHasAnEnrolmentUser(t *testing.T) {
+	inv, ctx := aMeshWith(t)
+	for _, name := range []string{"live", "expired", "none"} {
+		if _, err := inv.AddNode(ctx, name); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if _, err := inv.IssueToken(ctx, "live", time.Hour); err != nil {
+		t.Fatal(err)
+	}
+	// Briefly, then waited out: a token with no lifetime is refused at issue, which is the right
+	// refusal and leaves this as the way to have an expired one.
+	if _, err := inv.IssueToken(ctx, "expired", 10*time.Millisecond); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(50 * time.Millisecond)
+
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Join(records.Enrolling, ",") != "live" {
+		t.Fatalf("machines with a live token read as %v", records.Enrolling)
+	}
+}
+
+// A module assigned and absent from the catalogue is refused rather than composed with no authority.
+//
+// **The catalogue refuses to forget an assigned module, so this is the second line and not the
+// first** — and it earns its place there: relying on another package's invariant is how a rule ends
+// up enforced by nothing. Checked against the derivation directly, because the situation cannot be
+// reached through the store.
+func TestAnAssignmentWithNoManifestDerivesNoAuthority(t *testing.T) {
+	// What BusRecords would have produced had it composed a ghost: a module with nothing declared.
+	users, err := broker.Users(broker.Records{
+		Nodes:    []string{"one"},
+		Assigned: map[string][]broker.Declared{"one": {{Module: "ghost"}}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	perms, err := broker.PermissionsFor(users[len(users)-1])
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Its inbox and its ack subject, and nothing it could say. That is a module which starts,
+	// connects, and is refused by the server on its first publish — an authorisation error that
+	// says nothing about a missing manifest, which is why BusRecords names it instead.
+	for _, p := range perms.Publish {
+		if strings.HasPrefix(p, "mesh.mod.ghost.event.") {
+			t.Fatalf("a module with no manifest was granted %s", p)
+		}
+	}
+}
+
+func granted(all []string, one string) bool {
+	for _, s := range all {
+		if s == one {
+			return true
+		}
+	}
+	return false
+}
@@ -0,0 +1,264 @@
+package inventory
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"golang.org/x/crypto/bcrypt"
+)
+
+// The bus's own users, as records.
+//
+// **Only the credential is kept here.** A user's *authority* is derived from what its module
+// declares, every time the file is written (novox/hq ADR 0043) — a stored copy of a permission list
+// would be a second account of a user's authority, able to disagree with the first, and the
+// disagreement would be invisible until somebody compared a composed file with a manifest.
+//
+// What cannot be derived is the password, and on the bus being built it has to outlive its own
+// minting: the whole user list is one file, rewritten whenever any of it changes, so a person's
+// access change would blank every module's password if the mesh kept nothing (design 25 §4, and the
+// migration beside this).
+
+// BusUser is one user of the bus, as the mesh records it.
+type BusUser struct {
+	Username string
+	Kind     string
+	Node     string
+	Module   string
+	// PasswordHash is what the composed file carries. The plaintext is returned once, by Mint, and
+	// then exists only where it was sealed.
+	PasswordHash string
+}
+
+// The kinds of bus user the mesh records. The same words the composer uses, so a row and a
+// principal do not need a translation table between them.
+const (
+	BusController = "controller"
+	BusNode       = "node"
+	BusModule     = "module"
+	BusEnrolment  = "enrolment"
+	BusPerson     = "person"
+)
+
+// MintBusPassword makes a bus password and records its hash under a username, replacing whatever was
+// there, and returns the plaintext **once**.
+//
+// **Once is the whole contract.** The caller seals it to whoever will use it — into an enrolment
+// reply, into a module's sealed environment — and the mesh keeps only the hash, so a credential is
+// never recoverable from the store. A caller that loses it must mint again, which is a rotation and
+// is meant to feel like one.
+func (i *Inventory) MintBusPassword(ctx context.Context, u BusUser) (string, error) {
+	if u.Username == "" || u.Kind == "" {
+		return "", errors.New("a bus user needs a username and a kind")
+	}
+	raw := make([]byte, 32)
+	if _, err := rand.Read(raw); err != nil {
+		return "", fmt.Errorf("cannot generate a bus password: %w", err)
+	}
+	password := base64.RawURLEncoding.EncodeToString(raw)
+
+	// The cost the server will pay on every connection. Left at the library's default rather than
+	// raised: a node reconnecting after a network blip pays it, and the mesh's own links reconnect
+	// far more often than a person logs in anywhere.
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return "", fmt.Errorf("cannot hash a bus password: %w", err)
+	}
+
+	if _, err := i.store.Pool().Exec(ctx,
+		`insert into bus_user (username, kind, node, module, password_hash)
+		 values ($1, $2, $3, $4, $5)
+		 on conflict (username) do update
+		   set kind = excluded.kind, node = excluded.node, module = excluded.module,
+		       password_hash = excluded.password_hash, minted_at = now()`,
+		u.Username, u.Kind, u.Node, u.Module, string(hash)); err != nil {
+		return "", fmt.Errorf("cannot record the bus user %s: %w", u.Username, err)
+	}
+	return password, nil
+}
+
+// BusUsers is every user the composed file should contain, by username.
+//
+// Returned as a map because the composer asks by username: the principals are derived from records
+// elsewhere, and this is only what each one's password is. A principal with no row here has no
+// password, and the composer refuses it rather than writing a user anybody is.
+func (i *Inventory) BusUsers(ctx context.Context) (map[string]BusUser, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select username, kind, node, module, password_hash from bus_user order by username`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[string]BusUser{}
+	for rows.Next() {
+		var u BusUser
+		if err := rows.Scan(&u.Username, &u.Kind, &u.Node, &u.Module, &u.PasswordHash); err != nil {
+			return nil, err
+		}
+		out[u.Username] = u
+	}
+	return out, rows.Err()
+}
+
+// BusUserHash is one user's hash, or false when the mesh has never minted one for it.
+func (i *Inventory) BusUserHash(ctx context.Context, username string) (string, bool, error) {
+	var hash string
+	err := i.store.Pool().QueryRow(ctx,
+		`select password_hash from bus_user where username = $1`, username).Scan(&hash)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return "", false, nil
+	}
+	return hash, err == nil, err
+}
+
+// ForgetBusUser removes one user, so the next composition does not contain it.
+//
+// **Removal is what makes revocation real here.** On a bus with a management call, deleting an
+// account ends its connections; here the credential stops working when the file no longer names it,
+// which is the next composition — so forgetting the row and composing are one act, and a caller
+// that does the first without the second has revoked nothing.
+func (i *Inventory) ForgetBusUser(ctx context.Context, username string) error {
+	_, err := i.store.Pool().Exec(ctx, `delete from bus_user where username = $1`, username)
+	return err
+}
+
+// ForgetBusUsersOf removes every user belonging to one node — its host's, and every module assigned
+// to it. What a forgotten node leaves behind on the bus is otherwise a set of credentials for a
+// machine the mesh no longer knows.
+func (i *Inventory) ForgetBusUsersOf(ctx context.Context, node string) error {
+	if node == "" {
+		return errors.New("forgetting the bus users of no node would forget every user that has none")
+	}
+	_, err := i.store.Pool().Exec(ctx, `delete from bus_user where node = $1`, node)
+	return err
+}
+
+// SeedBusUser records a hash of a credential the mesh did not mint, so a composition contains it.
+//
+// **Genesis is the reason this exists.** The controller's own user is created before the controller
+// runs — by the installer, at a well-known bootstrap password, the way the store's and the old bus's
+// are (`postgres:bootstrap`, `guest:guest`). Nothing minted it, so nothing recorded a hash for it, and
+// the controller's first composition would leave itself out of the very file it was writing: a bus
+// nothing can connect to, produced by the thing connected to it.
+//
+// Idempotent, and it does not overwrite. A credential the mesh *did* mint is the one that counts, so
+// once there is a row this does nothing — otherwise a restart would put the bootstrap password back
+// over a rotated one.
+func (i *Inventory) SeedBusUser(ctx context.Context, u BusUser, password string) error {
+	if u.Username == "" || u.Kind == "" || password == "" {
+		return errors.New("a bus user needs a username, a kind and the credential it is using")
+	}
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("cannot hash a bus password: %w", err)
+	}
+	_, err = i.store.Pool().Exec(ctx,
+		`insert into bus_user (username, kind, node, module, password_hash)
+		 values ($1, $2, $3, $4, $5)
+		 on conflict (username) do nothing`,
+		u.Username, u.Kind, u.Node, u.Module, string(hash))
+	return err
+}
+
+// A person who may call the mesh's tools (novox/hq design 25 §7).
+//
+// **Their authority is a list of tools and nothing else.** Not a module: they hold no seat, nothing is
+// addressed to them, nothing is delivered to them, and they have no consumer to acknowledge. What
+// they have is permission to ask.
+
+// Person is somebody who may reach the mesh's tools.
+type Person struct {
+	Name string
+	// Invokes are the tools they may call, each `<module>.<tool>`, or the single entry `*` for an
+	// administrator.
+	Invokes []string
+}
+
+// RecordPerson adds somebody, or changes what they may call.
+//
+// Replacing rather than merging: what a person may call is stated in full, so a change that meant to
+// remove a tool does remove it. A list that could only grow is a permission nobody can take back.
+func (i *Inventory) RecordPerson(ctx context.Context, p Person) error {
+	if p.Name == "" {
+		return errors.New("a person needs a name: it becomes their user on the bus")
+	}
+	if len(p.Invokes) == 0 {
+		return fmt.Errorf(
+			"%s may call nothing, so there is no reason for them to reach the mesh. Name the tools, "+
+				"or `*` for an administrator", p.Name)
+	}
+	_, err := i.store.Pool().Exec(ctx,
+		`insert into person (name, invokes) values ($1, $2)
+		 on conflict (name) do update set invokes = excluded.invokes`,
+		p.Name, p.Invokes)
+	return err
+}
+
+// People is everybody who may reach the mesh's tools.
+func (i *Inventory) People(ctx context.Context) ([]Person, error) {
+	rows, err := i.store.Pool().Query(ctx, `select name, invokes from person order by name`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Person
+	for rows.Next() {
+		var p Person
+		if err := rows.Scan(&p.Name, &p.Invokes); err != nil {
+			return nil, err
+		}
+		out = append(out, p)
+	}
+	return out, rows.Err()
+}
+
+// ForgetPerson removes somebody and the credential they were given.
+//
+// **Both, or neither is a revocation.** A person's row gone and their bus user left behind is a
+// credential that still works and that nothing derives, which is the worst of both: it keeps working
+// and nobody can explain why.
+func (i *Inventory) ForgetPerson(ctx context.Context, name string) error {
+	if name == "" {
+		return errors.New("forgetting nobody would forget everybody")
+	}
+	if _, err := i.store.Pool().Exec(ctx, `delete from person where name = $1`, name); err != nil {
+		return err
+	}
+	return i.ForgetBusUser(ctx, "person."+name)
+}
+
+// PutBusMembership records a machine's membership for the new bus, sealed to it (design 28, 5.2).
+// Replaces any earlier one: a machine has one membership per bus, and re-minting is re-telling.
+func (i *Inventory) PutBusMembership(ctx context.Context, nodeName, sealed string) error {
+	node, err := i.NodeByName(ctx, nodeName)
+	if err != nil {
+		return err
+	}
+	_, err = i.store.Pool().Exec(ctx,
+		`insert into bus_membership (node, sealed) values ($1, $2)
+		 on conflict (node) do update set sealed = excluded.sealed, since = now()`, node.ID, sealed)
+	return err
+}
+
+// BusMemberships is every machine's sealed membership for the new bus, by node name.
+func (i *Inventory) BusMemberships(ctx context.Context) (map[string]string, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select n.name, b.sealed from bus_membership b join node n on n.id = b.node`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[string]string{}
+	for rows.Next() {
+		var name, sealed string
+		if err := rows.Scan(&name, &sealed); err != nil {
+			return nil, err
+		}
+		out[name] = sealed
+	}
+	return out, rows.Err()
+}
@@ -0,0 +1,160 @@
+package inventory
+
+import (
+	"context"
+	"testing"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+// The bus's users as records — against a real store, because what is being checked is that the
+// column exists, the upsert behaves, and a plaintext is returned exactly once.
+
+func aBusUser(module string) BusUser {
+	return BusUser{Username: "one." + module, Kind: BusModule, Node: "one", Module: module}
+}
+
+// The plaintext comes back once and the store keeps only a hash that verifies against it. **A
+// credential recoverable from the mesh's store is one whose blast radius is the store's**, so what
+// is asserted is that the password is not in there.
+func TestABusPasswordIsReturnedOnceAndOnlyItsHashIsKept(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+
+	password, err := inv.MintBusPassword(ctx, aBusUser("shop"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if password == "" {
+		t.Fatal("no password came back, so nothing can be sealed to the module")
+	}
+
+	hash, known, err := inv.BusUserHash(ctx, "one.shop")
+	if err != nil || !known {
+		t.Fatalf("the user was not recorded: %v %v", known, err)
+	}
+	if hash == password {
+		t.Fatal("the store holds the password itself")
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)); err != nil {
+		t.Fatalf("the recorded hash does not verify the password it was made from: %v", err)
+	}
+}
+
+// Minting again replaces what was there rather than failing or adding a second row: that is a
+// rotation, and the old credential stops working at the next composition.
+func TestMintingAgainRotatesRatherThanAddsAUser(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+
+	first, err := inv.MintBusPassword(ctx, aBusUser("shop"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	second, err := inv.MintBusPassword(ctx, aBusUser("shop"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if first == second {
+		t.Fatal("minting twice produced the same password")
+	}
+	users, err := inv.BusUsers(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(users) != 1 {
+		t.Fatalf("%d users after two mints for one name", len(users))
+	}
+	hash := users["one.shop"].PasswordHash
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(second)); err != nil {
+		t.Fatal("the kept hash is not the newest password's")
+	}
+	if bcrypt.CompareHashAndPassword([]byte(hash), []byte(first)) == nil {
+		t.Fatal("the previous password still verifies, so a rotation revoked nothing")
+	}
+}
+
+// Forgetting a node takes every credential that belonged to it — its host's and every module
+// assigned to it. What a forgotten node leaves behind otherwise is a working set of credentials for
+// a machine the mesh no longer knows.
+func TestForgettingANodeTakesItsBusUsersWithIt(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+
+	for _, u := range []BusUser{
+		{Username: "node.one", Kind: BusNode, Node: "one"},
+		aBusUser("shop"),
+		{Username: "node.two", Kind: BusNode, Node: "two"},
+		{Username: "controller", Kind: BusController},
+	} {
+		if _, err := inv.MintBusPassword(ctx, u); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := inv.ForgetBusUsersOf(ctx, "one"); err != nil {
+		t.Fatal(err)
+	}
+	users, err := inv.BusUsers(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, still := users["node.one"]; still {
+		t.Fatal("a forgotten node's host credential still works")
+	}
+	if _, still := users["one.shop"]; still {
+		t.Fatal("a module on a forgotten node still has a credential")
+	}
+	// And nothing else went with it: the controller has no node, and another machine's user is
+	// another machine's.
+	for _, kept := range []string{"node.two", "controller"} {
+		if _, ok := users[kept]; !ok {
+			t.Fatalf("%s was removed with another node's users", kept)
+		}
+	}
+}
+
+// Forgetting the users of no node would forget every user that has none — the controller and every
+// person — so it is refused rather than run.
+func TestForgettingTheUsersOfNoNodeIsRefused(t *testing.T) {
+	inv := ForTest(t)
+	if err := inv.ForgetBusUsersOf(context.Background(), ""); err == nil {
+		t.Fatal("forgetting the bus users of no node was allowed")
+	}
+}
+
+// The controller's own user is created by the installer, so the mesh has to be able to record a
+// credential it did not mint — or the first composition leaves the writer out of the file it writes.
+func TestACredentialTheMeshDidNotMintIsRecordedOnceAndNotOverwritten(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+
+	if err := inv.SeedBusUser(ctx, BusUser{Username: "controller", Kind: BusController},
+		"bootstrap"); err != nil {
+		t.Fatal(err)
+	}
+	hash, known, err := inv.BusUserHash(ctx, "controller")
+	if err != nil || !known {
+		t.Fatalf("the credential was not recorded: %v %v", known, err)
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte("bootstrap")); err != nil {
+		t.Fatalf("what was recorded does not verify the credential given: %v", err)
+	}
+
+	// Minted since, then seeded again — which is what a restart does. The rotation must stand, or
+	// every restart would put the bootstrap password back over it.
+	minted, err := inv.MintBusPassword(ctx, BusUser{Username: "controller", Kind: BusController})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.SeedBusUser(ctx, BusUser{Username: "controller", Kind: BusController},
+		"bootstrap"); err != nil {
+		t.Fatal(err)
+	}
+	hash, _, err = inv.BusUserHash(ctx, "controller")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(minted)); err != nil {
+		t.Fatal("a restart put the bootstrap credential back over a rotated one")
+	}
+}
@@ -8,6 +8,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"time"

 	"github.com/jackc/pgx/v5"
 	"github.com/novox/mesh-controller/internal/catalogue"
@@ -38,6 +39,9 @@ type Source struct {
 	BuiltFrom string
 	// Head is the newest commit the source is known to have.
 	Head string
+	// Seen is when the source was last looked at — by a build, by hand, or by the forge saying it
+	// moved. What a late report of an older move is judged against.
+	Seen time.Time
 }

 // Current reports whether what the mesh holds is what the source last had.
@@ -936,12 +940,13 @@ func (i *Inventory) Catalogued(ctx context.Context) ([]Entry, error) {
 		`select m.name, m.manifest,
 		        coalesce(m.source, ''), m.source_path, m.source_seat, coalesce(m.ref, ''),
 		        coalesce(m.built_from, ''), coalesce(m.source_head, ''),
+		        coalesce(m.source_seen, to_timestamp(0)),
 		        coalesce(array_agg(n.name order by n.name) filter (where n.name is not null), '{}')
 		 from module m
 		 left join assignment a on a.module = m.name
 		 left join node n on n.id = a.node
 		 group by m.name, m.manifest, m.source, m.source_path, m.source_seat, m.ref, m.built_from,
-		          m.source_head
+		          m.source_head, m.source_seen
 		 order by m.name`)
 	if err != nil {
 		return nil, err
@@ -955,9 +960,12 @@ func (i *Inventory) Catalogued(ctx context.Context) ([]Entry, error) {
 		var source Source
 		var on []string
 		if err := rows.Scan(&name, &raw, &source.Repository, &source.Path, &source.Seat, &source.Ref,
-			&source.BuiltFrom, &source.Head, &on); err != nil {
+			&source.BuiltFrom, &source.Head, &source.Seen, &on); err != nil {
 			return nil, err
 		}
+		if source.Seen.Unix() == 0 {
+			source.Seen = time.Time{}
+		}
 		var m catalogue.Manifest
 		if err := json.Unmarshal(raw, &m); err != nil {
 			return nil, err
@@ -0,0 +1,99 @@
+package inventory
+
+import (
+	"context"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// A seat's holder is a row, changed as one act (novox/hq ADR 0131). What these pin is the shape of
+// that row's life: it needs an assignment to point at, it is replaced rather than added to, and it
+// goes when the assignment does — so a seat never points at something that is not running anywhere.
+
+func twoBrokersOnTwoNodes(t *testing.T) (*Inventory, context.Context) {
+	t.Helper()
+	old := catalogue.Manifest{Module: "old-broker", Version: "1",
+		Provides: []catalogue.Offer{{Name: "mesh-bus", Scope: catalogue.ScopeMesh}},
+		Claims:   []catalogue.Claim{{Name: "mesh-broker", Scope: catalogue.ScopeMesh}}}
+	new := catalogue.Manifest{Module: "new-broker", Version: "1",
+		Provides: []catalogue.Offer{{Name: "mesh-bus", Scope: catalogue.ScopeMesh}},
+		Claims:   []catalogue.Claim{{Name: "mesh-broker", Scope: catalogue.ScopeMesh}}}
+	inv, ctx := aMeshWith(t, old, new)
+	// The holding references the seat's row, which `migrate` seeds on a real mesh.
+	if _, err := inv.SeedSeats(ctx, catalogue.DefaultSeats()); err != nil {
+		t.Fatal(err)
+	}
+	for _, n := range []string{"anchor", "laptop"} {
+		if _, err := inv.AddNode(ctx, n); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if _, err := inv.Assign(ctx, "anchor", "old-broker"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.Assign(ctx, "laptop", "new-broker"); err != nil {
+		t.Fatal(err)
+	}
+	return inv, ctx
+}
+
+func TestAHandoverIsOneRowReplacedNotOneAdded(t *testing.T) {
+	inv, ctx := twoBrokersOnTwoNodes(t)
+
+	if err := inv.HoldSeat(ctx, "mesh-broker", catalogue.ScopeMesh, "anchor", "old-broker"); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.HoldSeat(ctx, "mesh-broker", catalogue.ScopeMesh, "laptop", "new-broker"); err != nil {
+		t.Fatal(err)
+	}
+	held, err := inv.Holdings(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(held) != 1 || held[0].Node != "laptop" || held[0].Module != "new-broker" || held[0].Scope != catalogue.ScopeMesh {
+		t.Fatalf("after a handover the seat is not held by exactly the new holder: %+v", held)
+	}
+}
+
+func TestASeatCannotBeHandedToSomethingNotAssigned(t *testing.T) {
+	inv, ctx := twoBrokersOnTwoNodes(t)
+	// new-broker is assigned to laptop, not anchor.
+	if err := inv.HoldSeat(ctx, "mesh-broker", catalogue.ScopeMesh, "anchor", "new-broker"); err == nil {
+		t.Fatal("a seat was handed to a module not assigned where it was named")
+	}
+}
+
+func TestUnassigningTheHolderTakesTheHoldingWithIt(t *testing.T) {
+	inv, ctx := twoBrokersOnTwoNodes(t)
+	if err := inv.HoldSeat(ctx, "mesh-broker", catalogue.ScopeMesh, "laptop", "new-broker"); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.Unassign(ctx, "laptop", "new-broker"); err != nil {
+		t.Fatal(err)
+	}
+	held, err := inv.Holdings(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(held) != 0 {
+		t.Fatalf("the holding outlived the assignment it pointed at: %+v", held)
+	}
+}
+
+func TestAMachinesMembershipIsOneRowReplacedAndGoesWithTheMachine(t *testing.T) {
+	inv, ctx := twoBrokersOnTwoNodes(t)
+	if err := inv.PutBusMembership(ctx, "anchor", "first"); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.PutBusMembership(ctx, "anchor", "second"); err != nil {
+		t.Fatal(err)
+	}
+	got, err := inv.BusMemberships(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got["anchor"] != "second" || len(got) != 1 {
+		t.Fatalf("a re-told membership did not replace the first: %v", got)
+	}
+}
@@ -0,0 +1,17 @@
+-- The seats are data the control plane owns, not a slice compiled into it (novox/hq ADR 0122).
+--
+-- Until this, the closed set 0110 defines lived only as a Go slice, referenced by name everywhere,
+-- so renaming a seat or adding one meant a controller rebuild and a mesh-wide, freeze-prone deploy.
+-- The set is now a table: one row per seat, seeded from the binary's defaults the first time the
+-- control plane comes up, and thereafter the live copy the control plane reads and an operator can
+-- change. A rename becomes an update here rather than a release.
+--
+-- The name is the key for now, because claims and held records still reference a seat by name; the
+-- move to a stable id that a rename does not touch is the next step (ADR 0122). `delivers` is empty
+-- for a seat that answers for no provision, matching the compiled default.
+create table seat (
+  name     text primary key,
+  scope    text not null,
+  delivers text not null default '',
+  decided  text not null
+);
@@ -0,0 +1,12 @@
+-- A seat keeps its former names, so a rename breaks nothing (novox/hq ADR 0122).
+--
+-- Phase 1 made the seat set data, but a rename still broke every reference to the old name — a
+-- manifest's claim, a held record, the git-seat lookup — because they name the seat and the name
+-- had changed. This is the stable identity ADR 0122 asked for, realised the simple way: a seat's
+-- canonical name changes, and its old name becomes an alias that resolves to it forever. Nothing
+-- downstream has to change — a manifest goes on claiming the old name, the build machine goes on
+-- validating it — and a rename is one operation: set the new name, remember the old.
+create table seat_alias (
+  alias text primary key,       -- a former name of a seat
+  seat  text not null           -- the seat's current canonical name it resolves to
+);
@@ -0,0 +1,13 @@
+-- A node has an operator account: the human login on it (novox/hq to-be 29).
+--
+-- The mesh modelled the machine but not the person on it — `jochens` on novox, `ace` on ace,
+-- `jochen` on shanks and g14. That name decides who a file under a home is owned by and which
+-- account `ssh <node>` logs in as; it was silently lost when the predecessor's per-node `user:`
+-- was not carried over, and `ssh ace` failed to `ace` because nothing here said so.
+--
+-- Empty rather than null and defaulted, because "no operator account known yet" is a real state
+-- (a freshly enrolled machine, a headless box). The home is stored too rather than always assumed
+-- to be /home/<account>, because root's is /root and a machine may put a home elsewhere; empty
+-- means "derive it" (/root for root, /home/<account> otherwise), so the common case needs no entry.
+alter table node add column account text not null default '';
+alter table node add column account_home text not null default '';
@@ -0,0 +1,36 @@
+-- Every bus user's password hash, because the file has to be written again.
+--
+-- novox/hq design 25 §4, task 1.7. On the bus the mesh runs on today an account is created by a
+-- management call: the mesh mints a password, hands it over, seals the plaintext to whoever will
+-- use it, and keeps nothing. That works because the broker remembers.
+--
+-- The bus being built has no management call — its users are a file the controller composes, and
+-- **the whole file is written every time any of it changes**. So the first person's access change
+-- would silently blank every module's password. The hash has to outlive its own minting, which is
+-- state the mesh did not need before and does now.
+--
+-- Keyed by username, because the username is exactly what the composed file needs and what a
+-- principal derives from its own identity. Nothing else about the user is here: **permissions are
+-- not stored.** They are derived from what each module declares, every time the file is written
+-- (ADR 0043) — a stored copy would be a second account of a user's authority, able to disagree
+-- with the first, and the disagreement would be invisible until somebody compared a file with a
+-- manifest.
+--
+-- The hash and not the password. A file on a node's disk holds the hash, and so does this: a
+-- credential recoverable from the mesh's store is one whose blast radius is the store's.
+create table bus_user (
+    username      text primary key,
+    -- kind and what it names, so a user whose subject is gone can be found and removed: a module
+    -- unassigned, a node forgotten, a token spent. Recorded rather than parsed back out of the
+    -- username, because a name is for the server and a parser over it would be a second grammar.
+    kind          text        not null,
+    node          text        not null default '',
+    module        text        not null default '',
+    password_hash text        not null,
+    minted_at     timestamptz not null default now()
+);
+
+-- Finding every user of one kind, and every user belonging to one node — which is what removing a
+-- node, or composing after an assignment, asks.
+create index bus_user_kind on bus_user (kind);
+create index bus_user_node on bus_user (node) where node <> '';
@@ -0,0 +1,19 @@
+-- A person who may call the mesh's tools from a workstation.
+--
+-- novox/hq design 25 §7. Everything else that reaches the bus is a machine or a module running on
+-- one; this is the exception the mesh has always had informally — somebody at a terminal — and never
+-- recorded. Until now "the operator" meant whoever held the keys, which is a role and not a record,
+-- so nothing could say who may call what.
+--
+-- **The authority is a list of tools and nothing else.** A person is not a module: they hold no seat,
+-- nothing is addressed to them, nothing is delivered to them, and they have no consumer to
+-- acknowledge. What they have is permission to ask. That is why there is no scope column and no node
+-- column — a person is not on a machine.
+create table person (
+    name    text        primary key,
+    -- The tools this person may invoke, each `<module>.<tool>`, or the single entry `*` for an
+    -- administrator. Stored as given: the permission is derived from it at every composition, so a
+    -- normalised form here would be a second opinion about authority (novox/hq ADR 0043).
+    invokes text[]      not null default '{}',
+    created timestamptz not null default now()
+);
@@ -0,0 +1,24 @@
+-- A seat's holder is a recorded fact, not a derivation (novox/hq ADR 0131, design 26).
+--
+-- Until this, "which assignment holds the seat" was derived: the module that is assigned and
+-- claims the seat holds it, and a second eligible assignment was refused at resolution. That has no
+-- way to hand a seat from one holder to the next without a moment where nothing holds it — and the
+-- control plane finds its own bus through one of these seats, so that moment was an outage
+-- (2026-09-27). Now the holder is one row here, changed by `seat <name> --to <node>/<module>` as one
+-- act, and other assignments whose module could hold the seat are simply eligible and silent.
+--
+-- No row means what it always meant: the sole eligible assignment holds the seat, and two eligible
+-- ones are refused. So a mesh that has never handed a seat over behaves exactly as before, and the
+-- row appears the first time somebody does.
+--
+-- The seat is referenced by name because claims still are (0034); the rename cascades here so a
+-- handed-over seat survives being renamed. The holder is the assignment itself, so unassigning it
+-- takes the holding with it and the seat falls back to derivation rather than pointing at nothing.
+create table seat_holding (
+  seat   text        primary key references seat(name) on update cascade on delete cascade,
+  scope  text        not null,
+  node   uuid        not null,
+  module text        not null,
+  since  timestamptz not null default now(),
+  foreign key (node, module) references assignment(node, module) on delete cascade
+);
@@ -0,0 +1,12 @@
+-- The bus seat's holder answers for the mesh's bus, not for a wire protocol (novox/hq ADR 0131).
+--
+-- The row said `amqp`, which is the protocol the old broker spoke, and so only that broker could hold
+-- the seat that names the mesh's bus — while the module that will carry the bus could not. The seat
+-- delivers `mesh-bus`; whichever module provides that may hold it, and today that is one module.
+--
+-- Safe under the current holder: the control plane composes its own bus address through the seat by
+-- name, and the overview derives holders by name. Only registration and provision-to-seat resolution
+-- read this column. So the row changes, the current holder keeps holding by derivation, the next one
+-- can register its claim, and the handover (0039) moves the seat when both are running. What must
+-- not happen in between is re-registering the current holder — registration would now refuse it.
+update seat set delivers = 'mesh-bus' where name = 'mesh-broker' and delivers = 'amqp';
@@ -0,0 +1,11 @@
+-- A machine already enrolled is moved to the new bus by being told its membership for it
+-- (novox/hq design 28, task 5.2). Until this, a membership — bus address, fingerprint, password,
+-- transport — existed only in the enrolment reply, and nothing could hand one to a machine that
+-- had already joined. The row is the membership sealed to that machine, composed into its
+-- declaration as a file it reads after applying; the plaintext exists once, at minting, and then
+-- only on the machine. One per node: the mesh moves to one bus.
+create table bus_membership (
+  node   uuid        primary key references node(id) on delete cascade,
+  sealed text        not null,
+  since  timestamptz not null default now()
+);
@@ -55,6 +55,29 @@ type Node struct {
 	// AdoptedSince is when it last became so; zero for a converged node.
 	Adopted      bool
 	AdoptedSince time.Time
+
+	// Account is the operator's login on this machine — `jochens` on novox, `ace` on ace (novox/hq
+	// to-be 29). Empty when none is known yet. AccountHome is where that account's home is; empty
+	// means derive it (/root for root, /home/<account> otherwise), so the common case needs no
+	// entry. What decides who a file under a home is owned by, and which account `ssh <node>` uses.
+	Account     string
+	AccountHome string
+}
+
+// Home is the account's home directory, derived when not stored: /root for root, /home/<account>
+// otherwise. Empty only when there is no account at all.
+func (n Node) Home() string {
+	if n.AccountHome != "" {
+		return n.AccountHome
+	}
+	switch n.Account {
+	case "":
+		return ""
+	case "root":
+		return "/root"
+	default:
+		return "/home/" + n.Account
+	}
 }

 // Silent is how long since this node was last heard from, and whether it ever was.
@@ -112,12 +135,13 @@ func (i *Inventory) AddNodeAs(ctx context.Context, name string, adopted bool) (N

 // nodeColumns and scanNode are the one reading of a node row, so every way of finding a node
 // says whether it is adopted.
-const nodeColumns = `id, name, created, last_seen, adopted, adopted_since`
+const nodeColumns = `id, name, created, last_seen, adopted, adopted_since, account, account_home`

 func scanNode(row pgx.Row) (Node, error) {
 	var n Node
 	var seen, since *time.Time
-	if err := row.Scan(&n.ID, &n.Name, &n.Created, &seen, &n.Adopted, &since); err != nil {
+	if err := row.Scan(&n.ID, &n.Name, &n.Created, &seen, &n.Adopted, &since,
+		&n.Account, &n.AccountHome); err != nil {
 		return Node{}, err
 	}
 	if seen != nil {
@@ -129,6 +153,21 @@ func scanNode(row pgx.Row) (Node, error) {
 	return n, nil
 }

+// SetAccount records the operator account on a node — its human login — and optionally where that
+// account's home is (novox/hq to-be 29). An empty home means the mesh derives it. Clearing the
+// account (empty name) is allowed: a machine may stop having a known operator.
+func (i *Inventory) SetAccount(ctx context.Context, node, account, home string) error {
+	tag, err := i.store.Pool().Exec(ctx,
+		`update node set account = $1, account_home = $2 where name = $3`, account, home, node)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return fmt.Errorf("%w: %s", ErrNoSuchNode, node)
+	}
+	return nil
+}
+
 // Nodes are every node record, oldest first.
 func (i *Inventory) Nodes(ctx context.Context) ([]Node, error) {
 	rows, err := i.store.Pool().Query(ctx,
@@ -782,6 +821,25 @@ func (i *Inventory) RecordSent(ctx context.Context, node, digest string) error {
 	return err
 }

+// Outstanding is the digest of the declaration a machine was last sent, by its name, and empty
+// for one that has never been sent anything.
+//
+// **By name rather than by id**, because the caller is the serving loop and what a node puts in a
+// report is its name. Asked of one machine rather than read from Waiting's sweep, because it is
+// asked per message: a report names the declaration it is about, and a report about one the mesh
+// has already moved past is not acted on (design 25 §3).
+func (i *Inventory) Outstanding(ctx context.Context, name string) (string, error) {
+	var sent string
+	err := i.store.Pool().QueryRow(ctx,
+		`select coalesce(sent, '') from node where name = $1`, name).Scan(&sent)
+	if errors.Is(err, pgx.ErrNoRows) {
+		// Not an error worth carrying up: a report from a machine the mesh has no record of has
+		// nothing to be stale against, and whatever is wrong with it is the listener's to say.
+		return "", nil
+	}
+	return sent, err
+}
+
 // Waiting is every machine whose declaration has changed since it was last sent one.
 //
 // The caller works out what each machine should be now, because only it can — resolution is the
@@ -0,0 +1,120 @@
+package inventory
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/broker"
+)
+
+// Somebody who may call the mesh's tools, and what the bus makes of them.
+
+// A person's authority is a list of tools, and it becomes exactly that on the bus — nothing on
+// control, nothing on nodes, nothing they could publish as a module.
+func TestAPersonMayCallToolsAndNothingElse(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+	if err := inv.RecordPerson(ctx, Person{Name: "ada",
+		Invokes: []string{"mesh-catalog.catalog_tools"}}); err != nil {
+		t.Fatal(err)
+	}
+
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := records.People["ada"]; len(got) != 1 || got[0] != "mesh-catalog.catalog_tools" {
+		t.Fatalf("ada may call %v", got)
+	}
+
+	users, err := broker.Users(records)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found bool
+	for _, u := range users {
+		if u.Username() != "person.ada" {
+			continue
+		}
+		found = true
+		perms, err := broker.PermissionsFor(u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(perms.Publish) != 1 || perms.Publish[0] != "mesh.mod.mesh-catalog.tool.catalog_tools" {
+			t.Errorf("ada may publish %v, which should be the one tool and nothing else", perms.Publish)
+		}
+		for _, s := range perms.Publish {
+			if strings.HasPrefix(s, "mesh.control") || strings.HasPrefix(s, "mesh.node") ||
+				strings.Contains(s, ".event.") {
+				t.Errorf("a person may publish %s — an event would let them claim a module said "+
+					"something, and control is not theirs", s)
+			}
+		}
+		if perms.AllowResponses {
+			t.Error("a person may answer a request, which is impersonating a module on a bus where " +
+				"anyone may serve a tool")
+		}
+	}
+	if !found {
+		t.Fatal("no bus user was derived for a recorded person")
+	}
+}
+
+// Stating what somebody may call replaces what was there. A list that could only grow is a permission
+// nobody can take back.
+func TestChangingWhatAPersonMayCallRemovesWhatIsNotNamed(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+	if err := inv.RecordPerson(ctx, Person{Name: "ada", Invokes: []string{"a.one", "b.two"}}); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.RecordPerson(ctx, Person{Name: "ada", Invokes: []string{"a.one"}}); err != nil {
+		t.Fatal(err)
+	}
+	people, err := inv.People(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(people) != 1 || len(people[0].Invokes) != 1 || people[0].Invokes[0] != "a.one" {
+		t.Fatalf("ada may call %v; the removed tool is still there", people)
+	}
+}
+
+// Somebody who may call nothing is refused: there is no reason for them to reach the mesh, and an
+// empty list is more likely a mistake than an intention.
+func TestSomebodyWhoMayCallNothingIsRefused(t *testing.T) {
+	inv := ForTest(t)
+	if err := inv.RecordPerson(context.Background(), Person{Name: "ada"}); err == nil {
+		t.Fatal("somebody who may call nothing was recorded")
+	}
+}
+
+// Forgetting somebody takes their credential with them. **Both, or it is not a revocation**: a
+// person's row gone and their bus user left behind is a credential that still works and that nothing
+// derives.
+func TestForgettingAPersonTakesTheirCredential(t *testing.T) {
+	inv := ForTest(t)
+	ctx := context.Background()
+	if err := inv.RecordPerson(ctx, Person{Name: "ada", Invokes: []string{"a.one"}}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.MintBusPassword(ctx, BusUser{Username: "person.ada", Kind: BusPerson}); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := inv.ForgetPerson(ctx, "ada"); err != nil {
+		t.Fatal(err)
+	}
+	if _, known, err := inv.BusUserHash(ctx, "person.ada"); err != nil || known {
+		t.Fatalf("a forgotten person's credential still works: %v %v", known, err)
+	}
+	records, err := inv.BusRecords(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, still := records.People["ada"]; still {
+		t.Fatal("a forgotten person is still composed into the bus")
+	}
+}
@@ -0,0 +1,149 @@
+package inventory
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// The seats the mesh has, as data (novox/hq ADR 0122).
+//
+// The set the control plane reads is a table here, not a slice compiled into it. It is seeded from
+// the binary's defaults the first time the mesh comes up (SeedSeats), and thereafter it is the live
+// copy: a rename or an added seat is a write here, and the control plane loads it at startup rather
+// than being rebuilt for it.
+
+// Seats is every seat the mesh defines, read from the store.
+func (i *Inventory) Seats(ctx context.Context) ([]catalogue.Seat, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select name, scope, delivers, decided from seat order by name`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var seats []catalogue.Seat
+	for rows.Next() {
+		var s catalogue.Seat
+		if err := rows.Scan(&s.Name, &s.Scope, &s.Delivers, &s.Decision); err != nil {
+			return nil, err
+		}
+		seats = append(seats, s)
+	}
+	return seats, rows.Err()
+}
+
+// SeedSeats writes the mesh's default set into the table where it is not already present.
+//
+// **Idempotent, and never overwriting.** Run every time the control plane migrates, it fills an
+// empty table on first boot and adds a seat a new release ships — but it leaves a row already there
+// exactly as it is, so an operator's rename in the table is not undone by the next deploy putting
+// the old name back. What a release removes from the defaults is not deleted here either; retiring a
+// seat is its own decision, not a silent consequence of it dropping out of the binary.
+func (i *Inventory) SeedSeats(ctx context.Context, defaults []catalogue.Seat) (int, error) {
+	var added int
+	for _, s := range defaults {
+		tag, err := i.store.Pool().Exec(ctx,
+			`insert into seat (name, scope, delivers, decided) values ($1, $2, $3, $4)
+			 on conflict (name) do nothing`,
+			s.Name, s.Scope, s.Delivers, s.Decision)
+		if err != nil {
+			return added, err
+		}
+		added += int(tag.RowsAffected())
+	}
+	return added, nil
+}
+
+// Aliases is every former seat name and the seat it now resolves to (novox/hq ADR 0122).
+func (i *Inventory) Aliases(ctx context.Context) (map[string]string, error) {
+	rows, err := i.store.Pool().Query(ctx, `select alias, seat from seat_alias`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	aliases := map[string]string{}
+	for rows.Next() {
+		var alias, seat string
+		if err := rows.Scan(&alias, &seat); err != nil {
+			return nil, err
+		}
+		aliases[alias] = seat
+	}
+	return aliases, rows.Err()
+}
+
+// RenameSeat gives a seat a new name and keeps the old one as an alias (novox/hq ADR 0122).
+//
+// **This is the whole of a rename.** The seat's canonical name becomes `to`; `from` is remembered as
+// an alias so every reference to it — a manifest's claim, a held record, the build machine's
+// embedded set — goes on resolving to the same seat, unchanged. Nothing is rebuilt and nothing
+// freezes. Any alias that pointed to `from` is repointed to `to`, so a chain of renames does not
+// leave an older name resolving to a name that no longer exists.
+func (i *Inventory) RenameSeat(ctx context.Context, from, to string) error {
+	if from == to {
+		return fmt.Errorf("a seat is renamed to a different name; %q is already its name", to)
+	}
+	tag, err := i.store.Pool().Exec(ctx, `update seat set name = $1 where name = $2`, to, from)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return fmt.Errorf("no seat named %q to rename", from)
+	}
+	// The old name resolves to the new one; and any name that resolved to the old one now resolves
+	// to the new one, so no alias is left pointing at a name that is gone.
+	if _, err := i.store.Pool().Exec(ctx,
+		`insert into seat_alias (alias, seat) values ($1, $2)
+		 on conflict (alias) do update set seat = excluded.seat`, from, to); err != nil {
+		return err
+	}
+	if _, err := i.store.Pool().Exec(ctx,
+		`update seat_alias set seat = $1 where seat = $2`, to, from); err != nil {
+		return err
+	}
+	return nil
+}
+
+// HoldSeat records that one assignment holds a seat, replacing whoever held it — as one write, so
+// the seat is never without a holder in between (novox/hq ADR 0131, design 28 task 5.3). The
+// assignment must exist; the store refuses otherwise, and that refusal is the right one: a seat
+// cannot be handed to something that is not running anywhere.
+func (i *Inventory) HoldSeat(ctx context.Context, seat, scope, nodeName, module string) error {
+	node, err := i.NodeByName(ctx, nodeName)
+	if err != nil {
+		return err
+	}
+	_, err = i.store.Pool().Exec(ctx,
+		`insert into seat_holding (seat, scope, node, module) values ($1, $2, $3, $4)
+		 on conflict (seat) do update set scope = excluded.scope, node = excluded.node,
+		   module = excluded.module, since = now()`,
+		seat, scope, node.ID, module)
+	if err != nil {
+		return fmt.Errorf("recording %s on %s as the holder of %s: %w", module, nodeName, seat, err)
+	}
+	return nil
+}
+
+// Holdings is every seat whose holder is on record, as the resolver reads it. A seat with no row here
+// is held by derivation, exactly as before the table existed.
+func (i *Inventory) Holdings(ctx context.Context) ([]catalogue.Held, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select h.seat, h.scope, n.name, h.module, coalesce(n.site, '')
+		   from seat_holding h join node n on n.id = h.node order by h.seat`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []catalogue.Held
+	for rows.Next() {
+		var h catalogue.Held
+		if err := rows.Scan(&h.Claim, &h.Scope, &h.Node, &h.Module, &h.Site); err != nil {
+			return nil, err
+		}
+		out = append(out, h)
+	}
+	return out, rows.Err()
+}
@@ -0,0 +1,115 @@
+package inventory
+
+import (
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// The seat set is data the control plane owns (novox/hq ADR 0122): seeded from the binary's
+// defaults, read back as the working set, and thereafter an operator's to change without a rebuild.
+
+func TestSeatsAreSeededFromTheDefaultsAndReadBack(t *testing.T) {
+	inv := ForTest(t)
+	defaults := catalogue.DefaultSeats()
+
+	added, err := inv.SeedSeats(t.Context(), defaults)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if added != len(defaults) {
+		t.Fatalf("seeded %d of %d seats", added, len(defaults))
+	}
+	got, err := inv.Seats(t.Context())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != len(defaults) {
+		t.Fatalf("read back %d seats, seeded %d", len(got), len(defaults))
+	}
+	// The set round-trips: name, scope and what it delivers survive the store.
+	by := map[string]catalogue.Seat{}
+	for _, s := range got {
+		by[s.Name] = s
+	}
+	for _, d := range defaults {
+		if by[d.Name].Scope != d.Scope || by[d.Name].Delivers != d.Delivers {
+			t.Errorf("%s came back as %+v, seeded %+v", d.Name, by[d.Name], d)
+		}
+	}
+}
+
+// Re-seeding an already-seeded set adds nothing and changes nothing — every deploy runs SeedSeats,
+// and a mesh already holding the set must be left exactly as it is (an operator's edit to a row
+// included). A row's fields are not overwritten: on conflict the insert does nothing.
+//
+// (Phase 1 keys the table by name, so a seat *renamed* in the table would have its old name
+// re-seeded — the move to a stable id a rename does not touch is the next step, ADR 0122. This test
+// asserts only the property that holds now: an unchanged set re-seeds to a no-op.)
+func TestReSeedingAnUnchangedSetIsANoOp(t *testing.T) {
+	inv := ForTest(t)
+	defaults := catalogue.DefaultSeats()
+	if _, err := inv.SeedSeats(t.Context(), defaults); err != nil {
+		t.Fatal(err)
+	}
+
+	// An operator changes a row's scope in the table — the point of it being data.
+	if _, err := inv.store.Pool().Exec(t.Context(),
+		`update seat set scope = 'mesh' where name = 'node-uplink'`); err != nil {
+		t.Fatal(err)
+	}
+
+	added, err := inv.SeedSeats(t.Context(), defaults)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if added != 0 {
+		t.Fatalf("re-seeding an already-present set added %d rows", added)
+	}
+	got, err := inv.Seats(t.Context())
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, s := range got {
+		if s.Name == "node-uplink" && s.Scope != "mesh" {
+			t.Fatalf("re-seeding overwrote the operator's change: node-uplink scope is %q", s.Scope)
+		}
+	}
+}
+
+// A rename is one operation: the seat gets the new name, the old name becomes an alias that still
+// resolves to it (novox/hq ADR 0122).
+func TestRenameSeatKeepsTheFormerNameAsAnAlias(t *testing.T) {
+	inv := ForTest(t)
+	if _, err := inv.SeedSeats(t.Context(), catalogue.DefaultSeats()); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.RenameSeat(t.Context(), "node-packet-filter", "node-firewall"); err != nil {
+		t.Fatal(err)
+	}
+	seats, err := inv.Seats(t.Context())
+	if err != nil {
+		t.Fatal(err)
+	}
+	names := map[string]bool{}
+	for _, s := range seats {
+		names[s.Name] = true
+	}
+	if !names["node-firewall"] || names["node-packet-filter"] {
+		t.Fatalf("the seat was not renamed in place: %v", names)
+	}
+	aliases, err := inv.Aliases(t.Context())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if aliases["node-packet-filter"] != "node-firewall" {
+		t.Fatalf("the former name is not an alias of the new one: %v", aliases)
+	}
+	// Renaming what has no seat is refused; renaming to the same name is refused.
+	if err := inv.RenameSeat(t.Context(), "no-such-seat", "x"); err == nil {
+		t.Fatal("renaming a seat that does not exist was accepted")
+	}
+	if err := inv.RenameSeat(t.Context(), "node-firewall", "node-firewall"); err == nil {
+		t.Fatal("renaming a seat to its own name was accepted")
+	}
+}
--- a/Show More
+++ b/Show More