The control plane pins the bus's certificate, and keeps its password out of errors

The bus presents the mesh's own certificate, which names nothing a public verifier
accepts; the client verified by name and failed against a bus that was answering
("certificate is not valid for any names", 2026-09-28). It now pins the leaf's
fingerprint from MESH_BROKER_CERTIFICATE, as every host does. And a connection
error named the whole URL, password included — 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()
 

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 +30,58 @@ 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))
+	}
+	// 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/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.