A principal may hear what its consumer delivers

A push consumer delivers on _DELIVER.<its name>, and a client bound to it
subscribes exactly that. No principal was granted it, and the server refused
every one the first time it bound a consumer: the control plane, each machine,
and a module would have been next. Each kind is granted its own consumers'
delivery subjects and no other's. The line announcing the raised bus printed the
URL with the credential in it; the address alone now.

cmd/mesh-controller/ask.go

@@ -37,7 +37,7 @@ 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
 	}

cmd/mesh-controller/build.go

@@ -368,7 +368,7 @@ 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
 	}
@@ -472,7 +472,7 @@ 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
 	}

cmd/mesh-controller/push.go

@@ -38,6 +38,33 @@ 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, onNATS, err := broker.OnNATS()
+	if err != nil {
+		return nil, err
+	}
+	if err := broker.MustBeOneBus(os.Getenv(broker.AMQPVarName), busAddress); err != nil {
+		return nil, err
+	}
+	if !onNATS {
+		return link.Connect(enroller, listener)
+	}
+	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 {
@@ -90,7 +117,7 @@ func serve(ctx context.Context) error {
 
 	work := link.Enrolment{Inventory: inv, Identity: ident, Management: management, Broker: known,
 		OnNATS: onNATS}
-	server, err := link.Connect(work, work)
+	server, err := connectLink(ctx, inv, work, work)
 	if err != nil {
 		return err
 	}
@@ -100,11 +127,6 @@ func serve(ctx context.Context) error {
 	// 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.
-	if onNATS {
-		if err := raiseTheBus(ctx, inv, busAddress); err != nil {
-			return err
-		}
-	}
 	// 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})
@@ -158,13 +180,13 @@ 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, link.OverCurrent{Channel: 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))
@@ -271,7 +293,7 @@ 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
 	}
@@ -332,7 +354,7 @@ func pushCommand(ctx context.Context, args []string) error {
 		if err != nil {
 			return err
 		}
-		if err := link.Declare(ctx, link.OverCurrent{Channel: 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
@@ -415,7 +437,7 @@ 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, link.OverCurrent{Channel: server.Channel()}, ident, s.node, body,
+					if err := link.Declare(ctx, server.Bus(), ident, s.node, body,
 						15*time.Second); err != nil {
 						return err
 					}
@@ -628,7 +650,7 @@ 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
 	}
@@ -639,7 +661,7 @@ func sendTo(ctx context.Context, open *stores, names []string) error {
 		if err != nil {
 			return err
 		}
-		if err := link.Declare(ctx, link.OverCurrent{Channel: 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)
@@ -704,7 +726,7 @@ func raiseTheBus(ctx context.Context, inv *inventory.Inventory, address string)
 	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",
-			address, err)
+			broker.BareAddress(address), err)
 	}
 	defer js.Close()
 
@@ -743,6 +765,6 @@ func raiseTheBus(ctx context.Context, inv *inventory.Inventory, address string)
 		return err
 	}
 	fmt.Printf("the bus at %s has its streams, and %d machine(s) can hear a declaration\n",
-		address, len(names))
+		broker.BareAddress(address), len(names))
 	return nil
 }

internal/broker/jetstream.go

@@ -1,8 +1,14 @@
 package broker
 
 import (
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/hex"
 	"errors"
 	"fmt"
+	"os"
+	"strings"
 	"time"
 
 	"github.com/nats-io/nats.go"
@@ -24,21 +30,64 @@ type JetStream struct {
 
 // Dial connects and returns the controller's JetStream handle.
 func Dial(url string, opts ...nats.Option) (*JetStream, error) {
-	// A name, because a connection nobody can identify in the server's own monitoring is one
-	// nobody can attribute a problem to.
 	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", url, err)
+		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", url, err)
+		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 &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
+		},
+	}, 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).

internal/broker/nats.go

@@ -169,7 +169,11 @@ func PermissionsFor(p Principal) (Permissions, error) {
 		// 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.>", "$JS.API.>"}
-		sub = []string{"mesh.control.>", "$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
@@ -252,7 +256,7 @@ func PermissionsFor(p Principal) (Permissions, error) {
 			"mesh.control." + p.Node + ".>",
 			"$JS.API.CONSUMER.INFO.NODES." + p.Node,
 		}
-		sub = []string{"mesh.node." + p.Node + ".declare"}
+		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
@@ -285,7 +289,12 @@ func PermissionsFor(p Principal) (Permissions, error) {
 		}
 
 		// 3. Seats it holds: full participation.
+		// Its consumer's name, not ConsumerFor: that 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.
+		sub = append(sub, "_DELIVER."+consumerDurable(p))
 		for _, s := range p.Holds {
+			sub = append(sub, "_DELIVER.SEAT_"+upperSnake(s.Name)+"_worker")
 			for _, a := range s.Accepts {
 				sub = append(sub, seatSubject(s, "accept", a))
 			}
@@ -521,7 +530,10 @@ func ComposeAccounts(principals []Principal) (string, error) {
 	// 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.
-	b.WriteString("accounts {\n  MESH {\n    users = [\n")
+	// 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 {

internal/broker/testdata/composed.conf

@@ -21,10 +21,11 @@ jetstream {
 
 accounts {
   MESH {
+    jetstream: enabled
     users = [
       { user: "controller", password: "$2a$11$cccccccccccccccccccccc", permissions: {
         publish: { allow: ["$JS.ACK.CONTROL.controller.>", "$JS.ACK.EVENTS.controller.>", "$JS.API.>", "_INBOX.enrol.>", "mesh.control.>", "mesh.node.>", "mesh.seat.mesh-build-machine.accept.>"] }
-        subscribe: { allow: ["$JS.API.>", "_INBOX.controller.>", "mesh.control.>", "mesh.mod.mesh-catalog.event.catching-up", "mesh.mod.mesh-catalog.event.upgraded", "mesh.seat.mesh-build-machine.event.built"] }
+        subscribe: { allow: ["$JS.API.>", "_DELIVER.controller", "_DELIVER.controller.>", "_INBOX.controller.>", "mesh.control.>", "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: {
@@ -33,20 +34,20 @@ accounts {
       } }
       { 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: ["_INBOX.node.one.>", "mesh.node.one.declare"] }
+        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.>", "mesh.seat.telegram-sender.event.delivered", "mesh.seat.telegram-sender.event.failed"] }
-        subscribe: { allow: ["_INBOX.one.telegram.>", "mesh.mod.telegram.tool.status", "mesh.seat.telegram-sender.accept.send"] }
+        subscribe: { allow: ["_DELIVER.SEAT_TELEGRAM_SENDER_worker", "_DELIVER.one_telegram", "_INBOX.one.telegram.>", "mesh.mod.telegram.tool.status", "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.>"] }
-        subscribe: { allow: ["_INBOX.two.audit.>", "mesh.mod.shop.event.order.placed"] }
+        subscribe: { allow: ["_DELIVER.two_audit", "_INBOX.two.audit.>", "mesh.mod.shop.event.order.placed"] }
       } }
       { user: "two.shop", password: "$2a$11$ssssssssssssssssssssss", permissions: {
         publish: { allow: ["$JS.ACK.EVENTS.two_shop.>", "mesh.mod.shop.event.order.placed", "mesh.seat.telegram-sender.accept.send"] }
-        subscribe: { allow: ["_INBOX.two.shop.>"] }
+        subscribe: { allow: ["_DELIVER.two_shop", "_INBOX.two.shop.>"] }
       } }
     ]
   }

internal/broker/users_test.go

@@ -186,7 +186,13 @@ func TestWhatTheMeshWritesIsUsersAndNothingAboutTheServer(t *testing.T) {
 	}
 	// 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.
-	for _, absent := range []string{"port:", "http:", "jetstream", "tls {", "store_dir", "cert_file"} {
+	// `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)

internal/link/bus_nats.go

@@ -0,0 +1,73 @@
+package link
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/nats-io/nats.go"
+
+	"github.com/novox/mesh-controller/internal/broker"
+)
+
+// OverNats is the controller's outbound on the bus being built: the same three acts the other
+// transport has, on the subjects the permissions were derived for (design 25). A declaration is a
+// JetStream publish into NODES, where the node's own consumer waits for it; an event is announced on
+// the subject its name derives to; a tool is asked by request and reply on the module's tool subject.
+type OverNats struct{ JS *broker.JetStream }
+
+// declareSubject is where one node's declaration lands — the NODES stream's subject for it, and the
+// only subject that node's consumer delivers. The host subscribes exactly this.
+func declareSubject(node string) string { return "mesh.node." + node + ".declare" }
+
+func (b OverNats) PublishDeclaration(ctx context.Context, node string, body []byte) error {
+	publish, cancel := context.WithTimeout(ctx, 15*time.Second)
+	defer cancel()
+	if _, err := b.JS.Context().Publish(declareSubject(node), body, nats.Context(publish)); err != nil {
+		return fmt.Errorf("declaring to %s: %w", node, err)
+	}
+	return nil
+}
+
+func (b OverNats) PublishEvent(ctx context.Context, key, source, node string, body []byte) error {
+	// The key is the subject: the controller's own events are named in full, and what a module
+	// emits is derived before it reaches here. Headers carry the envelope the other transport put
+	// in message properties (ADR 0042), so a consumer reads who and when without the payload.
+	msg := nats.NewMsg(key)
+	msg.Data = body
+	msg.Header.Set("x-source", source)
+	msg.Header.Set("x-node", node)
+	msg.Header.Set("x-time", time.Now().UTC().Format(time.RFC3339Nano))
+	if err := b.JS.Conn().PublishMsg(msg); err != nil {
+		return fmt.Errorf("announcing %s: %w", key, err)
+	}
+	return nil
+}
+
+func (b OverNats) AskTool(ctx context.Context, module, tool string, args []byte, timeout time.Duration) ([]byte, error) {
+	ask, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+	reply, err := b.JS.Conn().RequestWithContext(ask, "mesh.mod."+module+".tool."+tool, args)
+	if err != nil {
+		return nil, fmt.Errorf("asking %s.%s: %w", module, tool, err)
+	}
+	return reply.Data, nil
+}
+
+// ConnectNats is Connect for the bus being built: the controller's inbound and outbound over one
+// JetStream connection the caller has already raised the streams on. Nothing is declared here —
+// the streams and the controller's consumers are asserted by Raise, before anything is served.
+func ConnectNats(js *broker.JetStream, enroller Enroller, listener Listener) *Server {
+	return &Server{
+		inbound:  Nats(js),
+		bus:      OverNats{JS: js},
+		js:       js,
+		enroller: enroller,
+		listener: listener,
+		log:      newLog(),
+	}
+}
+
+// Bus is the controller's outbound, whichever transport it connected over. Callers that send a
+// declaration or ask a tool use this rather than the channel, which one transport does not have.
+func (s *Server) Bus() Bus { return s.bus }

internal/link/serve.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/novox/mesh-controller/internal/broker"
 	"log"
 	"os"
 	"time"
@@ -70,6 +71,7 @@ type Server struct {
 	bus     Bus
 	conn    *amqp.Connection
 	channel *amqp.Channel
+	js      *broker.JetStream
 
 	enroller Enroller
 	listener Listener
@@ -180,10 +182,12 @@ func Connect(enroller Enroller, listener Listener) (*Server, error) {
 		channel:  channel,
 		enroller: enroller,
 		listener: listener,
-		log:      log.New(os.Stdout, "", log.LstdFlags),
+		log:      newLog(),
 	}, nil
 }
 
+func newLog() *log.Logger { return log.New(os.Stdout, "", log.LstdFlags) }
+
 // Channel is the controller's channel, for the command line's own publishing.
 func (s *Server) Channel() *amqp.Channel { return s.channel }
 
@@ -197,6 +201,9 @@ func (s *Server) Close() {
 	if s.conn != nil {
 		_ = s.conn.Close()
 	}
+	if s.js != nil {
+		s.js.Close()
+	}
 }
 
 // Serve acts on what arrives until the context ends.