Serve a module from a runtime on its own account instead of switching users, keep bus words from bundles, and never give up a channel's work (hq ADR 0259 revision)

merge-check.sh

@@ -33,6 +33,9 @@ if ! command -v node >/dev/null 2>&1 || [ ! -d node_modules/@novox/mesh-sdk ]; t
 	# What of the console launches no bundle runs anyway: how an address resolves (novox/hq issue 287),
 	# and how a search ranks (novox/hq ADR 0245).
 	bundleless='^(TestASeatAndAModuleOfOneNameAreEachReached|TestSearch.*|TestASearchByCommandSaysWhatItReplaces)$'
+	# And what of the runtime launches no bundle: how a bundle's seat traffic reaches the bus, what its
+	# environment holds, and what a runtime on a module's own account serves (novox/hq ADR 0259).
+	runtimeless='^(TestARuntimeOnAModulesOwnAccountServesThatModuleAlone|TestNoBusWordReachesABundle|TestAToolCallNeverReachesASeatsEventAcceptOrProof|TestABundlesSeatTrafficGoesThroughItsModulesBus|TestALostCompareAndSetCarriesItsCode)$'
 fi
 if command -v gcc >/dev/null 2>&1; then
 	CGO_ENABLED=1 go test -race -count=1 $packages
@@ -43,4 +46,7 @@ fi
 if [ -n "$bundleless" ]; then
 	CGO_ENABLED=0 go test -count=1 -run "$bundleless" ./internal/console
 fi
+if [ -n "${runtimeless:-}" ]; then
+	CGO_ENABLED=0 go test -count=1 -run "$runtimeless" ./internal/runtime
+fi
 echo "NOT TESTED HERE: node-tools/src (TypeScript) needs @novox/mesh-sdk from the package registry"

node-tools/internal/bus/bus.go

@@ -64,6 +64,9 @@ type Membership struct {
 	Tools   string              `json:"tools"`
 	// State is every bucket the module's code may reach, by the name it uses (novox/hq ADR 0201).
 	State []StateIssued `json:"state,omitempty"`
+	// SeatTraffic is what the module's code may submit, say, take, ask, answer and read on seats that name
+	// their caller or their kind (novox/hq ADR 0259): the runtime does for it only what is listed here.
+	SeatTraffic *SeatTraffic `json:"seat-traffic,omitempty"`
 }
 
 // Served is an address a tool is answered on; `{tool}` stands for the tool's name.

node-tools/internal/bus/seat.go

@@ -0,0 +1,439 @@
+package bus
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+// A bundle's traffic on seats that name their caller or their kind (novox/hq ADR 0259 §3): submitting an
+// accept and saying an event under its own name or kind, taking a held seat's work from its worker, asking a
+// proof and answering one, and reading a record kept for it.
+//
+// **The runtime keeps each module to its own name and kind.** One account per machine carries every module
+// on it, so the bus enforces only the union; what one module may reach is its membership's `seat-traffic`,
+// and anything else is refused here, with the reason, before it is sent. A bundle reaches this only through
+// its own standard input and output: no tool call does.
+
+// SeatTraffic is what a membership lists of a module's seat traffic (the controller's broker.SeatTraffic).
+type SeatTraffic struct {
+	Publish   []string     `json:"publish,omitempty"`
+	Subscribe []string     `json:"subscribe,omitempty"`
+	Answers   []string     `json:"answers,omitempty"`
+	Workers   []SeatWorker `json:"workers,omitempty"`
+	Records   []string     `json:"records,omitempty"`
+	// Kinds are the holders of every kinded bench the module uses or watches, with what each promises: the
+	// controller's record of their claims (novox/hq ADR 0259 §5).
+	Kinds []KindHeld `json:"kinds,omitempty"`
+}
+
+// KindHeld is one kind of a kinded bench and who holds it.
+type KindHeld struct {
+	Seat         string   `json:"seat"`
+	Kind         string   `json:"kind"`
+	Module       string   `json:"module"`
+	Node         string   `json:"node"`
+	Capabilities []string `json:"capabilities,omitempty"`
+}
+
+// SeatKinds is the kinds the module's membership names, as the controller issued them.
+func (c *Conn) SeatKinds(module string) ([]KindHeld, error) {
+	t, err := c.trafficOf(module)
+	if err != nil {
+		return nil, err
+	}
+	return append([]KindHeld{}, t.Kinds...), nil
+}
+
+// SeatWorker is one work queue a holder takes from.
+type SeatWorker struct {
+	Stream   string `json:"Stream"`
+	Consumer string `json:"Consumer"`
+	Filter   string `json:"Filter"`
+}
+
+// ProofTimeout bounds how long a proof waits for its answer.
+var ProofTimeout = 15 * time.Second
+
+// WorkHeartbeat is how often work a bundle is still doing is said to be in progress, well inside the
+// worker's ack wait.
+var WorkHeartbeat = 15 * time.Second
+
+// WorkBackoff is how long a piece of work the bundle did not take waits before it is offered again: from
+// five seconds, doubling, to ten minutes.
+func WorkBackoff(delivered uint64) time.Duration {
+	wait := 5 * time.Second
+	for i := uint64(1); i < delivered && wait < 10*time.Minute; i++ {
+		wait *= 2
+	}
+	return min(wait, 10*time.Minute)
+}
+
+// SubjectMatches is a subject against a permission pattern, in the server's wildcards.
+func SubjectMatches(pattern, subject string) bool {
+	p, s := strings.Split(pattern, "."), strings.Split(subject, ".")
+	for i, part := range p {
+		if part == ">" {
+			return len(s) > i
+		}
+		if i >= len(s) || (part != "*" && part != s[i]) {
+			return false
+		}
+	}
+	return len(p) == len(s)
+}
+
+func (c *Conn) trafficOf(module string) (*SeatTraffic, error) {
+	m := c.Membership(module)
+	if m == nil {
+		return nil, fmt.Errorf("%s has no membership issued on %s yet, so it reaches no seat (novox/hq ADR 0259)",
+			module, c.node)
+	}
+	if m.SeatTraffic == nil {
+		return nil, fmt.Errorf("%s holds, uses and watches no seat that names its caller or its kind (novox/hq "+
+			"ADR 0259): its manifest says so under `uses`, `claims` and `consumes`", module)
+	}
+	return m.SeatTraffic, nil
+}
+
+func listed(patterns []string, subject string) bool {
+	for _, p := range patterns {
+		if SubjectMatches(p, subject) {
+			return true
+		}
+	}
+	return false
+}
+
+// mayPublish refuses a subject the module's seat traffic does not list. A wildcard is never published.
+func (c *Conn) mayPublish(module, subject string) error {
+	t, err := c.trafficOf(module)
+	if err != nil {
+		return err
+	}
+	if strings.ContainsAny(subject, "*>") || !listed(t.Publish, subject) {
+		return fmt.Errorf("%s may not publish %s: a module submits and says only under its own name or kind, "+
+			"and its membership lists %s (novox/hq ADR 0259)", module, subject, strings.Join(t.Publish, ", "))
+	}
+	return nil
+}
+
+func newID() string {
+	var b [16]byte
+	_, _ = rand.Read(b[:])
+	return hex.EncodeToString(b[:])
+}
+
+// SeatPublish submits an accept or says an event on a seat, as the module, into the stream that keeps it,
+// awaited and de-duplicated by its id: the same id twice is one message. A proof is never published here.
+func (c *Conn) SeatPublish(module, subject string, body json.RawMessage, id string) (uint64, error) {
+	seq, _, err := c.SeatPublishSaid(module, subject, body, id)
+	return seq, err
+}
+
+// SeatPublishSaid is SeatPublish, also saying whether the bus took it as a duplicate of one published before
+// under the same id: the same message, kept once.
+func (c *Conn) SeatPublishSaid(module, subject string, body json.RawMessage, id string) (uint64, bool, error) {
+	if strings.Contains(subject, ".proof.") {
+		return 0, false, fmt.Errorf("%s is a proof, asked and answered, never kept: ask it as one", subject)
+	}
+	if err := c.mayPublish(module, subject); err != nil {
+		return 0, false, err
+	}
+	if len(body) == 0 || !json.Valid(body) {
+		return 0, false, fmt.Errorf("what is said on %s is JSON", subject)
+	}
+	if id == "" {
+		id = newID()
+	}
+	// **The publisher's name is part of the id the bus de-duplicates by** (security review 2026-10-08): ids
+	// are the publisher's own, and one module could otherwise suppress another's warrant by publishing first
+	// under the same id.
+	id = module + "." + id
+	msg := nats.NewMsg(subject)
+	msg.Header.Set("x-event-id", id)
+	msg.Header.Set("x-source", module)
+	msg.Header.Set("x-node", c.node)
+	msg.Header.Set("x-time", time.Now().UTC().Format(time.RFC3339Nano))
+	msg.Header.Set("content-type", "application/json")
+	msg.Data = body
+	ack, err := c.js.PublishMsg(msg, nats.MsgId(id))
+	if err != nil {
+		return 0, false, err
+	}
+	return ack.Sequence, ack.Duplicate, nil
+}
+
+// SeatProve asks a proof and answers its reply: core request and reply, on no stream.
+func (c *Conn) SeatProve(module, subject string, body json.RawMessage) (json.RawMessage, error) {
+	if !strings.Contains(subject, ".proof.") {
+		return nil, fmt.Errorf("%s is not a proof", subject)
+	}
+	if err := c.mayPublish(module, subject); err != nil {
+		return nil, err
+	}
+	reply, err := c.nc.Request(subject, body, ProofTimeout)
+	if errors.Is(err, nats.ErrNoResponders) {
+		return nil, fmt.Errorf("nothing answers %s: the module watching the seat is not running", subject)
+	}
+	if err != nil {
+		return nil, err
+	}
+	if !json.Valid(reply.Data) {
+		return nil, fmt.Errorf("the answer to %s is not JSON", subject)
+	}
+	return json.RawMessage(reply.Data), nil
+}
+
+// SeatAnswer answers every proof on a subject the module's seat traffic lists among its answers, with what
+// answer returns. A returned error is answered as `{"error": "<words>"}`, never as silence.
+func (c *Conn) SeatAnswer(module, subject string, answer func(subject string, body json.RawMessage) (json.RawMessage, error)) (func(), error) {
+	t, err := c.trafficOf(module)
+	if err != nil {
+		return nil, err
+	}
+	allowed := false
+	for _, a := range t.Answers {
+		allowed = allowed || a == subject
+	}
+	if !allowed {
+		return nil, fmt.Errorf("%s does not answer %s: its membership lists %s (novox/hq ADR 0259)", module,
+			subject, strings.Join(t.Answers, ", "))
+	}
+	sub, err := c.nc.Subscribe(subject, func(msg *nats.Msg) {
+		if msg.Reply == "" {
+			return
+		}
+		body := json.RawMessage(msg.Data)
+		if !json.Valid(body) {
+			_ = msg.Respond([]byte(`{"error":"a proof is JSON"}`))
+			return
+		}
+		out, err := answer(msg.Subject, body)
+		if err != nil {
+			b, _ := json.Marshal(map[string]string{"error": err.Error()})
+			_ = msg.Respond(b)
+			return
+		}
+		if len(out) == 0 {
+			out = json.RawMessage(`{}`)
+		}
+		if err := msg.Respond(out); err != nil {
+			c.Logf("[mesh-tools] %s could not answer the proof on %s: %v", module, msg.Subject, err)
+		}
+	})
+	if err != nil {
+		return nil, err
+	}
+	c.track(sub)
+	var once sync.Once
+	return func() { once.Do(func() { _ = sub.Unsubscribe() }) }, nil
+}
+
+// Work is one message a holder took from a seat's work queue.
+type Work struct {
+	Worker  string            `json:"worker"`
+	Subject string            `json:"subject"`
+	Body    json.RawMessage   `json:"body"`
+	Headers map[string]string `json:"headers,omitempty"`
+}
+
+// SeatTake reads a worker the module's seat traffic lists and hands each message to deliver: acknowledged
+// when deliver returns nil, offered again after NakDelay when it returns an error, ended when it is not
+// JSON. The worker is the controller's to create; this binds to it by name and never makes one.
+func (c *Conn) SeatTake(module, consumer string, deliver func(Work) error) (func(), error) {
+	t, err := c.trafficOf(module)
+	if err != nil {
+		return nil, err
+	}
+	var w *SeatWorker
+	for i := range t.Workers {
+		if t.Workers[i].Consumer == consumer {
+			w = &t.Workers[i]
+		}
+	}
+	if w == nil {
+		var names []string
+		for _, x := range t.Workers {
+			names = append(names, x.Consumer)
+		}
+		return nil, fmt.Errorf("%s takes no work from %s: its membership lists %s (novox/hq ADR 0259)", module,
+			consumer, strings.Join(names, ", "))
+	}
+	js, err := jetstream.New(c.nc)
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	bound, err := js.Consumer(ctx, w.Stream, w.Consumer)
+	if err != nil {
+		return nil, fmt.Errorf("binding %s's worker %s on %s: %w", module, w.Consumer, w.Stream, err)
+	}
+	reading, err := bound.Consume(func(msg jetstream.Msg) {
+		if !json.Valid(msg.Data()) {
+			_ = msg.Term()
+			return
+		}
+		headers := map[string]string{}
+		for k := range msg.Headers() {
+			headers[k] = msg.Headers().Get(k)
+		}
+		// Kept alive while the bundle works on it, however long that takes: the ack wait is for a holder
+		// that died, not one that is slow.
+		done := make(chan struct{})
+		go func() {
+			tick := time.NewTicker(WorkHeartbeat)
+			defer tick.Stop()
+			for {
+				select {
+				case <-done:
+					return
+				case <-tick.C:
+					_ = msg.InProgress()
+				}
+			}
+		}()
+		err := deliver(Work{Worker: w.Consumer, Subject: msg.Subject(), Body: json.RawMessage(msg.Data()), Headers: headers})
+		close(done)
+		if err != nil {
+			// Offered again later and later, never given up on: a channel that is away keeps its work
+			// (security and correctness reviews of 2026-10-08).
+			delivered := uint64(1)
+			if meta, merr := msg.Metadata(); merr == nil {
+				delivered = meta.NumDelivered
+			}
+			_ = msg.NakWithDelay(WorkBackoff(delivered))
+			return
+		}
+		_ = msg.Ack()
+	}, jetstream.ConsumeErrHandler(func(_ jetstream.ConsumeContext, err error) {
+		// A worker deleted, or the bus refusing it, is said — never a holder that silently takes nothing.
+		c.Logf("[mesh-tools] %s's worker %s: %v", module, w.Consumer, err)
+	}))
+	if err != nil {
+		return nil, fmt.Errorf("reading %s's worker %s: %w", module, w.Consumer, err)
+	}
+	var once sync.Once
+	return func() { once.Do(reading.Stop) }, nil
+}
+
+// SeatRecord reads one key of a record a seat keeps for the module, under its own name: the bucket's
+// current value of `<module>.<key>`, or nil when there is none.
+func (c *Conn) SeatRecord(module, bucket, key string) (*StateEntry, error) {
+	t, err := c.trafficOf(module)
+	if err != nil {
+		return nil, err
+	}
+	if err := checkKey(key); err != nil {
+		return nil, err
+	}
+	if bucket == "" {
+		// The one record its membership lists, when it lists one: an asker reads the router's asks without
+		// knowing the router's name.
+		var named []string
+		for _, r := range t.Records {
+			if b, _, ok := strings.Cut(strings.TrimPrefix(r, "$JS.API.DIRECT.GET.KV_"), "."); ok {
+				named = append(named, b)
+			}
+		}
+		if len(named) != 1 {
+			return nil, fmt.Errorf("%s reads %d records under its name; name the one meant", module, len(named))
+		}
+		bucket = named[0]
+	}
+	subject := "$JS.API.DIRECT.GET.KV_" + bucket + ".$KV." + bucket + "." + module + "." + key
+	if !listed(t.Records, subject) {
+		return nil, fmt.Errorf("%s reads no record of %s under its name: its membership lists %s (novox/hq ADR 0259)",
+			module, bucket, strings.Join(t.Records, ", "))
+	}
+	reply, err := c.nc.Request(subject, nil, StateTimeout)
+	if err != nil {
+		return nil, err
+	}
+	if status := reply.Header.Get("Status"); status == "404" {
+		return nil, nil
+	} else if status != "" {
+		return nil, fmt.Errorf("the record %s.%s could not be read: %s %s", module, key, status, reply.Header.Get("Description"))
+	}
+	if op := reply.Header.Get("KV-Operation"); op == "DEL" || op == "PURGE" {
+		return nil, nil
+	}
+	var revision uint64
+	fmt.Sscan(reply.Header.Get("Nats-Sequence"), &revision)
+	return &StateEntry{Key: module + "." + key, Value: valueOf(reply.Data), Revision: revision}, nil
+}
+
+// StateCreate writes one key only when it has no value, and answers its revision; a key that has one is
+// refused, naming it, so two writers racing to make it are one winner and one refusal.
+func (c *Conn) StateCreate(module, name, key string, value json.RawMessage) (uint64, error) {
+	return c.stateWrite(module, name, key, value, func(ctx context.Context, kv jetstream.KeyValue) (uint64, error) {
+		return kv.Create(ctx, key, value)
+	})
+}
+
+// StateUpdate writes one key only when its revision is still the one given, and answers the new revision;
+// a key changed meanwhile is refused, so of two writers that read one value only the first writes.
+func (c *Conn) StateUpdate(module, name, key string, value json.RawMessage, revision uint64) (uint64, error) {
+	if revision == 0 {
+		// Revision zero would be read by the server as "the key is new": an update names the value it read.
+		return 0, fmt.Errorf("an update names the revision it read; zero is none — create the key instead")
+	}
+	return c.stateWrite(module, name, key, value, func(ctx context.Context, kv jetstream.KeyValue) (uint64, error) {
+		return kv.Update(ctx, key, value, revision)
+	})
+}
+
+// ErrStateChanged is a compare-and-set that lost: the key was made or changed by another writer first.
+var ErrStateChanged = errors.New("the key was written by another writer first")
+
+// changed is ErrStateChanged naming the key, with the code a bundle is answered it by.
+type changed struct{ key string }
+
+func (e changed) Error() string        { return e.key + ": " + ErrStateChanged.Error() }
+func (e changed) Is(target error) bool { return target == ErrStateChanged }
+func (e changed) ErrorCode() int       { return -32010 }
+
+func (c *Conn) stateWrite(module, name, key string, value json.RawMessage,
+	write func(context.Context, jetstream.KeyValue) (uint64, error)) (uint64, error) {
+	s, err := c.writable(module, name)
+	if err != nil {
+		return 0, err
+	}
+	if err := checkKey(key); err != nil {
+		return 0, err
+	}
+	if len(value) == 0 || !json.Valid(value) {
+		return 0, fmt.Errorf("a state value is JSON")
+	}
+	if field := credentialField(value); field != "" {
+		return 0, fmt.Errorf("%s's %s.%s carries a field %q, which names a credential: no secret is kept in state "+
+			"(novox/hq ADR 0201)", module, name, key, field)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), StateTimeout)
+	defer cancel()
+	kv, err := c.bucket(ctx, s)
+	if err != nil {
+		return 0, err
+	}
+	rev, err := write(ctx, kv)
+	if errors.Is(err, jetstream.ErrKeyExists) || isWrongSequence(err) {
+		return 0, changed{name + "." + key}
+	}
+	return rev, err
+}
+
+// isWrongSequence is the server's refusal of an update whose revision is not the key's last.
+func isWrongSequence(err error) bool {
+	var api *jetstream.APIError
+	return errors.As(err, &api) && api.ErrorCode == jetstream.JSErrCodeStreamWrongLastSequence
+}

node-tools/internal/bus/seat_test.go

@@ -0,0 +1,239 @@
+package bus_test
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+
+	"github.com/novox/mesh-tools/node-tools/internal/bus"
+	mt "github.com/novox/mesh-tools/node-tools/internal/meshtest"
+)
+
+// The seats of novox/hq ADR 0259 §3 as the controller issues them: an asker, the router, and a channel of
+// kind telegram, each with the seat traffic its membership lists.
+func seatMesh(t *testing.T) (*mt.Mesh, *bus.Conn, nats.JetStreamContext) {
+	t.Helper()
+	mesh := mt.New(t)
+	nc, err := nats.Connect(mt.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(nc.Close)
+	js, _ := nc.JetStream()
+	for _, s := range []*nats.StreamConfig{
+		{Name: "SEAT_OPERATOR_CHANNEL", Subjects: []string{"mesh.seat.operator-channel.accept.>"}, Retention: nats.WorkQueuePolicy},
+		{Name: "SEAT_CHANNEL", Subjects: []string{"mesh.seat.channel.accept.>"}, Retention: nats.WorkQueuePolicy},
+		{Name: "SEAT_EVENTS", Subjects: []string{"mesh.seat.*.event.>"}},
+	} {
+		if _, err := js.AddStream(s); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for stream, c := range map[string]*nats.ConsumerConfig{
+		"SEAT_OPERATOR_CHANNEL": {Durable: "SEAT_OPERATOR_CHANNEL_worker", AckPolicy: nats.AckExplicitPolicy,
+			FilterSubject: "mesh.seat.operator-channel.accept.>", AckWait: 2 * time.Second},
+		"SEAT_CHANNEL": {Durable: "SEAT_CHANNEL_TELEGRAM_worker", AckPolicy: nats.AckExplicitPolicy,
+			FilterSubject: "mesh.seat.channel.accept.*.telegram", AckWait: 2 * time.Second},
+	} {
+		if _, err := js.AddConsumer(stream, c); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if _, err := js.CreateKeyValue(&nats.KeyValueConfig{Bucket: "messenger_asks"}); err != nil {
+		t.Fatal(err)
+	}
+
+	asker := mt.MembershipOf("mesh-delivery", "anchor", false, nil)
+	asker.SeatTraffic = &bus.SeatTraffic{
+		Publish:   []string{"mesh.seat.operator-channel.accept.ask.mesh-delivery"},
+		Subscribe: []string{"mesh.seat.operator-channel.event.decided.mesh-delivery"},
+		Records:   []string{"$JS.API.DIRECT.GET.KV_messenger_asks.$KV.messenger_asks.mesh-delivery.>"},
+	}
+	router := mt.MembershipOf("messenger", "anchor", false, nil)
+	router.SeatTraffic = &bus.SeatTraffic{
+		Publish: []string{"mesh.seat.operator-channel.event.decided.*", "mesh.seat.channel.accept.show.*"},
+		Answers: []string{"mesh.seat.intake.proof.code.*"},
+		Workers: []bus.SeatWorker{{Stream: "SEAT_OPERATOR_CHANNEL", Consumer: "SEAT_OPERATOR_CHANNEL_worker",
+			Filter: "mesh.seat.operator-channel.accept.>"}},
+	}
+	router.State = []bus.StateIssued{{Name: "asks", Bucket: "messenger_asks", Writes: true}}
+	telegram := mt.MembershipOf("telegram", "anchor", false, nil)
+	telegram.SeatTraffic = &bus.SeatTraffic{
+		Publish: []string{"mesh.seat.intake.event.choice.telegram", "mesh.seat.intake.proof.code.telegram"},
+		Workers: []bus.SeatWorker{{Stream: "SEAT_CHANNEL", Consumer: "SEAT_CHANNEL_TELEGRAM_worker",
+			Filter: "mesh.seat.channel.accept.*.telegram"}},
+	}
+	for _, m := range []bus.Membership{asker, router, telegram} {
+		mesh.Issue(t, m)
+	}
+	conn, err := bus.Connect(bus.Credential{URL: mt.URL(t), Module: "node-tools", Node: "anchor"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.Logf = func(string, ...any) {}
+	t.Cleanup(conn.Close)
+	for _, m := range []string{"mesh-delivery", "messenger", "telegram"} {
+		conn.Follow(m)
+	}
+	mt.Until(t, func() error {
+		for _, m := range []string{"mesh-delivery", "messenger", "telegram"} {
+			if conn.Membership(m) == nil {
+				return errors.New(m + " not issued yet")
+			}
+		}
+		return nil
+	})
+	return mesh, conn, js
+}
+
+func TestAModuleSubmitsAndSaysOnlyUnderItsOwnNameAndKind(t *testing.T) {
+	_, conn, _ := seatMesh(t)
+	body := json.RawMessage(`{"id":"a1"}`)
+	if _, err := conn.SeatPublish("mesh-delivery", "mesh.seat.operator-channel.accept.ask.mesh-delivery", body, "a1"); err != nil {
+		t.Fatalf("an asker could not ask under its own name: %v", err)
+	}
+	for module, subject := range map[string]string{
+		"mesh-delivery": "mesh.seat.operator-channel.accept.ask.mesh-controller",
+		"telegram":      "mesh.seat.intake.event.choice.desktop",
+		"messenger":     "mesh.seat.intake.event.choice.telegram",
+	} {
+		if _, err := conn.SeatPublish(module, subject, body, ""); err == nil || !strings.Contains(err.Error(), "may not publish") {
+			t.Errorf("%s published %s: %v", module, subject, err)
+		}
+	}
+	if _, err := conn.SeatPublish("messenger", "mesh.seat.operator-channel.event.decided.*", body, ""); err == nil {
+		t.Error("a wildcard was published")
+	}
+	if _, err := conn.SeatPublish("telegram", "mesh.seat.intake.proof.code.telegram", body, ""); err == nil ||
+		!strings.Contains(err.Error(), "never kept") {
+		t.Errorf("a proof was published onto a stream: %v", err)
+	}
+}
+
+func TestTheHolderTakesItsWorkOnceAndAFailureComesBack(t *testing.T) {
+	_, conn, _ := seatMesh(t)
+	if _, err := conn.SeatPublish("mesh-delivery", "mesh.seat.operator-channel.accept.ask.mesh-delivery",
+		json.RawMessage(`{"id":"a1"}`), "a1"); err != nil {
+		t.Fatal(err)
+	}
+	// The same id again is one ask: a retry after a lost answer does not ask twice.
+	if _, err := conn.SeatPublish("mesh-delivery", "mesh.seat.operator-channel.accept.ask.mesh-delivery",
+		json.RawMessage(`{"id":"a1"}`), "a1"); err != nil {
+		t.Fatal(err)
+	}
+	var mu sync.Mutex
+	var got []string
+	fail := true
+	stop, err := conn.SeatTake("messenger", "SEAT_OPERATOR_CHANNEL_worker", func(w bus.Work) error {
+		mu.Lock()
+		defer mu.Unlock()
+		got = append(got, w.Subject+" from "+w.Headers["x-source"])
+		if fail {
+			fail = false
+			return errors.New("not recorded")
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stop()
+	deadline := time.Now().Add(15 * time.Second)
+	for {
+		mu.Lock()
+		n := len(got)
+		mu.Unlock()
+		if n >= 2 || time.Now().After(deadline) {
+			break
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+	time.Sleep(500 * time.Millisecond)
+	mu.Lock()
+	defer mu.Unlock()
+	if len(got) != 2 || got[0] != "mesh.seat.operator-channel.accept.ask.mesh-delivery from mesh-delivery" || got[0] != got[1] {
+		t.Fatalf("want the one ask, offered again after the failure: %v", got)
+	}
+	if _, err := conn.SeatTake("telegram", "SEAT_OPERATOR_CHANNEL_worker", func(bus.Work) error { return nil }); err == nil {
+		t.Error("a channel took the router's work")
+	}
+}
+
+func TestAProofIsAskedAndAnsweredAndNeverKept(t *testing.T) {
+	_, conn, js := seatMesh(t)
+	stop, err := conn.SeatAnswer("messenger", "mesh.seat.intake.proof.code.*", func(subject string, body json.RawMessage) (json.RawMessage, error) {
+		if !strings.HasSuffix(subject, ".telegram") {
+			return nil, errors.New("asked by another kind")
+		}
+		return json.RawMessage(`{"linked":true}`), nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stop()
+	var answer json.RawMessage
+	mt.Until(t, func() error {
+		answer, err = conn.SeatProve("telegram", "mesh.seat.intake.proof.code.telegram", json.RawMessage(`{"code":"123456"}`))
+		return err
+	})
+	if string(answer) != `{"linked":true}` {
+		t.Fatalf("the proof was answered %s", answer)
+	}
+	if _, err := conn.SeatProve("telegram", "mesh.seat.intake.proof.code.desktop", json.RawMessage(`{}`)); err == nil {
+		t.Error("a channel asked a proof as another kind")
+	}
+	if _, err := conn.SeatAnswer("telegram", "mesh.seat.intake.proof.code.*", nil); err == nil {
+		t.Error("a channel answers proofs")
+	}
+	for name := range js.StreamNames() {
+		info, _ := js.StreamInfo(name)
+		for _, s := range info.Config.Subjects {
+			if bus.SubjectMatches(s, "mesh.seat.intake.proof.code.telegram") {
+				t.Errorf("%s keeps proofs", name)
+			}
+		}
+	}
+}
+
+func TestAnAskerReadsItsOwnRecordAndNoOther(t *testing.T) {
+	_, conn, js := seatMesh(t)
+	kv, _ := js.KeyValue("messenger_asks")
+	if _, err := kv.Put("mesh-delivery.a1", []byte(`{"state":"open"}`)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := kv.Put("mesh-controller.a1", []byte(`{"state":"open"}`)); err != nil {
+		t.Fatal(err)
+	}
+	got, err := conn.SeatRecord("mesh-delivery", "messenger_asks", "a1")
+	if err != nil || got == nil || string(got.Value) != `{"state":"open"}` {
+		t.Fatalf("the asker could not read its own ask: %v %v", got, err)
+	}
+	if missing, err := conn.SeatRecord("mesh-delivery", "messenger_asks", "a2"); err != nil || missing != nil {
+		t.Fatalf("a missing ask read as %v, %v", missing, err)
+	}
+	if _, err := conn.SeatRecord("telegram", "messenger_asks", "a1"); err == nil {
+		t.Error("a module read records it is not given")
+	}
+}
+
+func TestOfTwoAnswersToOneAskOnlyTheFirstIsWritten(t *testing.T) {
+	_, conn, _ := seatMesh(t)
+	rev, err := conn.StateCreate("messenger", "asks", "mesh-delivery.a1", json.RawMessage(`{"state":"open"}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := conn.StateCreate("messenger", "asks", "mesh-delivery.a1", json.RawMessage(`{"state":"open"}`)); !errors.Is(err, bus.ErrStateChanged) {
+		t.Errorf("a second create stood: %v", err)
+	}
+	if _, err := conn.StateUpdate("messenger", "asks", "mesh-delivery.a1", json.RawMessage(`{"state":"answered"}`), rev); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := conn.StateUpdate("messenger", "asks", "mesh-delivery.a1", json.RawMessage(`{"state":"answered"}`), rev); !errors.Is(err, bus.ErrStateChanged) {
+		t.Errorf("a second answer from the same revision stood: %v", err)
+	}
+}

node-tools/internal/launch/event_answer_test.go

@@ -40,6 +40,9 @@ func (b *subscribing) State(string, json.RawMessage) (json.RawMessage, error) {
 func (b *subscribing) Watch(json.RawMessage, func(json.RawMessage) error) (func(), error) {
 	return func() {}, nil
 }
+func (b *subscribing) Seat(string, json.RawMessage, func(string, any) (json.RawMessage, error)) (json.RawMessage, error) {
+	return nil, nil
+}
 func (b *subscribing) Subscribe(d func(json.RawMessage) error) error {
 	b.mu.Lock()
 	defer b.mu.Unlock()

node-tools/internal/launch/launch.go

@@ -60,6 +60,10 @@ type Bus interface {
 	Subscribe(deliver func(envelope json.RawMessage) error) error
 	State(verb string, params json.RawMessage) (json.RawMessage, error)
 	Watch(params json.RawMessage, deliver func(change json.RawMessage) error) (stop func(), err error)
+	// Seat answers a bundle's seat traffic (novox/hq ADR 0259 §3): `publish`, `prove` and `record` at once;
+	// `take` and `answer` bind once and hand each message or proof on through handOn, to whichever child
+	// of the module asked last — a restarted child asks again as its code runs again.
+	Seat(verb string, params json.RawMessage, handOn func(method string, params any) (json.RawMessage, error)) (json.RawMessage, error)
 }
 
 // EventTimeout bounds how long a bundle has to handle one event before it is offered again.
@@ -147,6 +151,17 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 	// The child that last subscribed is the one events are handed to: a restarted child subscribes
 	// again as its code is imported, and from then on the module's events are its.
 	var subscriber *child
+	// The child that last asked to take a seat's work or answer its proofs is the one they are handed to.
+	var seatTaker *child
+	handOn := func(method string, params any) (json.RawMessage, error) {
+		mu.Lock()
+		c := seatTaker
+		mu.Unlock()
+		if c == nil {
+			return nil, errors.New(module + "'s bundle is not running to take it")
+		}
+		return c.ask(module, method, params, EventTimeout)
+	}
 	stopped := false
 	deliver := func(envelope json.RawMessage) error {
 		mu.Lock()
@@ -237,7 +252,21 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 							subscriber = c
 							mu.Unlock()
 							err = mesh.Subscribe(deliver)
-						case "mesh/state.get", "mesh/state.put", "mesh/state.delete", "mesh/state.keys":
+						case "mesh/seat.publish", "mesh/seat.prove", "mesh/seat.record", "mesh/seat.kinds":
+							var answered json.RawMessage
+							if answered, err = mesh.Seat(strings.TrimPrefix(m.Method, "mesh/seat."), m.Params, nil); err == nil {
+								result = answered
+							}
+						case "mesh/seat.take", "mesh/seat.answer":
+							mu.Lock()
+							seatTaker = c
+							mu.Unlock()
+							var answered json.RawMessage
+							if answered, err = mesh.Seat(strings.TrimPrefix(m.Method, "mesh/seat."), m.Params, handOn); err == nil {
+								result = answered
+							}
+						case "mesh/state.get", "mesh/state.put", "mesh/state.delete", "mesh/state.keys",
+							"mesh/state.create", "mesh/state.update":
 							var answered json.RawMessage
 							if answered, err = mesh.State(strings.TrimPrefix(m.Method, "mesh/state."), m.Params); err == nil {
 								result = answered
@@ -275,7 +304,7 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 						}
 						if err != nil {
 							_ = c.write(map[string]any{"jsonrpc": "2.0", "id": m.ID,
-								"error": map[string]any{"code": -32000, "message": err.Error()}})
+								"error": map[string]any{"code": errorCode(err), "message": err.Error()}})
 							return
 						}
 						_ = c.write(map[string]any{"jsonrpc": "2.0", "id": m.ID, "result": result})
@@ -329,6 +358,9 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 			if subscriber == c {
 				subscriber = nil
 			}
+			if seatTaker == c {
+				seatTaker = nil
+			}
 			wasStopped := stopped
 			// Started again at once if it ran a while; after a growing pause while it keeps exiting.
 			wait := RestartFirst
@@ -561,3 +593,17 @@ func (c *child) deathReason() error {
 	}
 	return errors.New("the bundle exited")
 }
+
+// CodeChanged is the error code a bundle is answered a lost compare-and-set with (mesh-sdk's
+// stdio.CodeChanged): told by its code, never by its words (novox/hq ADR 0259).
+const CodeChanged = -32010
+
+// errorCode is the code an error is answered to a bundle with: a lost compare-and-set's own, else the
+// general one.
+func errorCode(err error) int {
+	var coded interface{ ErrorCode() int }
+	if errors.As(err, &coded) {
+		return coded.ErrorCode()
+	}
+	return -32000
+}

node-tools/internal/launch/seat_test.go

@@ -0,0 +1,71 @@
+package launch
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+)
+
+// A bundle that asks to take a worker's work and answers each piece it is handed.
+const takingBundle = `#!/bin/sh
+while IFS= read -r line; do
+  id=$(printf '%s' "$line" | sed -n 's/.*"id":\([0-9]*\)[,}].*/\1/p')
+  case "$line" in
+    *'"method":"initialize"'*) printf '{"jsonrpc":"2.0","id":%s,"result":{}}\n' "$id" ;;
+    *'"method":"tools/list"'*)
+      printf '{"jsonrpc":"2.0","id":%s,"result":{"tools":[]}}\n' "$id"
+      printf '{"jsonrpc":"2.0","id":"s1","method":"mesh/seat.take","params":{"worker":"SEAT_CHANNEL_TELEGRAM_worker"}}\n' ;;
+    *'"method":"mesh/work"'*) printf '{"jsonrpc":"2.0","id":%s,"result":{"taken":true}}\n' "$id" ;;
+  esac
+done
+`
+
+type seating struct {
+	subscribing
+	mu     sync.Mutex
+	verb   string
+	params string
+	handOn func(string, any) (json.RawMessage, error)
+}
+
+func (b *seating) Seat(verb string, params json.RawMessage, handOn func(string, any) (json.RawMessage, error)) (json.RawMessage, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.verb, b.params, b.handOn = verb, string(params), handOn
+	return json.RawMessage(`{}`), nil
+}
+
+// novox/hq ADR 0259 §3: a bundle's seat traffic reaches the runtime's bus from its own channel, and the work
+// it takes is handed back to it.
+func TestABundleTakesASeatsWorkThroughItsOwnChannel(t *testing.T) {
+	entry := filepath.Join(t.TempDir(), "bundle")
+	if err := os.WriteFile(entry, []byte(takingBundle), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	b := &seating{}
+	l, err := Start("telegram", entry, os.Environ(), b, t.Logf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(l.Stop)
+	var handOn func(string, any) (json.RawMessage, error)
+	for i := 0; handOn == nil; i++ {
+		if i > 100 {
+			t.Fatal("the bundle never asked to take its work")
+		}
+		time.Sleep(20 * time.Millisecond)
+		b.mu.Lock()
+		handOn = b.handOn
+		b.mu.Unlock()
+	}
+	if b.verb != "take" || b.params != `{"worker":"SEAT_CHANNEL_TELEGRAM_worker"}` {
+		t.Fatalf("asked %s %s", b.verb, b.params)
+	}
+	got, err := handOn("mesh/work", map[string]any{"work": map[string]any{"subject": "mesh.seat.channel.accept.show.telegram"}})
+	if err != nil || string(got) != `{"taken":true}` {
+		t.Fatalf("the work was not handed to the bundle: %s %v", got, err)
+	}
+}

node-tools/internal/runtime/own_account_test.go

@@ -0,0 +1,56 @@
+package runtime
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-tools/node-tools/internal/bus"
+)
+
+// novox/hq ADR 0259 §8: a runtime on a module's own account serves that module alone, and the machine's
+// runtime never serves itself.
+func TestARuntimeOnAModulesOwnAccountServesThatModuleAlone(t *testing.T) {
+	if got, err := ServedModulesFrom("telegram=/b/telegram/tools/telegram", "telegram"); err != nil || len(got) != 1 {
+		t.Fatalf("a module's own runtime could not serve it: %v", err)
+	}
+	if _, err := ServedModulesFrom("telegram=/b/t,dunst=/b/d", "telegram"); err == nil || !strings.Contains(err.Error(), "serves telegram alone") {
+		t.Errorf("a module's own runtime served another: %v", err)
+	}
+	if _, err := ServedModulesFrom("node-tools=/b/n", "node-tools"); err == nil {
+		t.Error("the machine's runtime served itself")
+	}
+}
+
+// No bus word reaches a bundle (security review of 2026-10-08), not even one its module's words name.
+func TestNoBusWordReachesABundle(t *testing.T) {
+	base := []string{"MESH_BROKER_FILE=/etc/mesh/broker", "MESH_BROKER_URL=nats://x", "MESH_TOOL_ENV={}",
+		"MESH_TOOL_MODULES=a=/b", "MESH_CONSOLE_LISTEN=127.0.0.1:1", "PATH=/usr/bin"}
+	env := strings.Join(BundleEnv(base, map[string]string{"MESH_BROKER_FILE": "/again", "OWN": "1"}, "telegram", "anchor"), "\n")
+	for _, never := range []string{"MESH_BROKER_FILE", "MESH_BROKER_URL", "MESH_TOOL_ENV", "MESH_TOOL_MODULES", "MESH_CONSOLE_LISTEN"} {
+		if strings.Contains(env, never+"=") {
+			t.Errorf("%s reached the bundle", never)
+		}
+	}
+	for _, want := range []string{"PATH=/usr/bin", "OWN=1", "MESH_MODULE=telegram", "MESH_NODE=anchor"} {
+		if !strings.Contains(env, want) {
+			t.Errorf("%s did not reach the bundle", want)
+		}
+	}
+}
+
+// A tool call reaches only a tool's subject: whatever key a caller names, it is never a seat's event, accept
+// or proof — so no tool call says a choice, a link or a code, or submits an ask, in anybody's name.
+func TestAToolCallNeverReachesASeatsEventAcceptOrProof(t *testing.T) {
+	for _, key := range []string{"seat:intake.event.choice.telegram", "seat:intake.proof.code.telegram",
+		"seat:operator-channel.accept.ask.mesh-delivery", "intake.event", "seat:operator-channel.event.decided.x@anchor",
+		"telegram.anything", "x"} {
+		subject, err := bus.ToolSubject(key, "node-tools")
+		if err != nil {
+			continue
+		}
+		tokens := strings.Split(subject, ".")
+		if len(tokens) < 4 || tokens[3] != "tool" {
+			t.Errorf("%q reaches %s, which is not a tool's subject", key, subject)
+		}
+	}
+}

node-tools/internal/runtime/runtime.go

@@ -53,6 +53,13 @@ type ListedTool struct {
 	Subjects    []string        `json:"subjects,omitempty"`
 }
 
+// NodeRuntimeModule is the module that is a machine's runtime, serving every module on it.
+const NodeRuntimeModule = "node-tools"
+
+// runtimeOnly are the words of the runtime's own environment no bundle is given.
+var runtimeOnly = map[string]bool{ToolEnv: true, ToolModules: true, "MESH_BROKER_FILE": true,
+	"MESH_BROKER_URL": true, "MESH_CONSOLE_LISTEN": true}
+
 // ServedModulesFrom reads MESH_TOOL_MODULES: `<module>=<entrypoint>` entries, comma-separated, several
 // per module. The one-module form — a bare path, or the runtime's own module — is the per-module
 // containers' (to-be 38 WP4c) and refused here: the node's runtime imports nothing.
@@ -66,9 +73,20 @@ func ServedModulesFrom(spec, own string) ([]Served, error) {
 		}
 		module, path, ok := strings.Cut(entry, "=")
 		module, path = strings.TrimSpace(module), strings.TrimSpace(path)
-		if !ok || module == "" || path == "" || module == own {
-			return nil, fmt.Errorf("%s: %q is not <module>=<entrypoint> of another module; the node's "+
-				"runtime launches the bundles it is given and imports nothing (novox/hq ADR 0193)", ToolModules, entry)
+		if !ok || module == "" || path == "" {
+			return nil, fmt.Errorf("%s: %q is not <module>=<entrypoint>; the runtime launches the bundles it "+
+				"is given and imports nothing (novox/hq ADR 0193)", ToolModules, entry)
+		}
+		// The node's runtime serves the machine's modules and never itself. **A runtime on a module's own
+		// account serves that module and nothing else** (novox/hq ADR 0259 §8): the router and a channel that
+		// proves its sender reach the bus on an account of their own, never the machine's runtime.
+		switch {
+		case own == NodeRuntimeModule && module == own:
+			return nil, fmt.Errorf("%s: %q is the runtime itself; it launches the bundles it is given and "+
+				"imports nothing (novox/hq ADR 0193)", ToolModules, entry)
+		case own != NodeRuntimeModule && module != own:
+			return nil, fmt.Errorf("%s: %q is another module's; a runtime on %s's own account serves %s alone "+
+				"(novox/hq ADR 0259)", ToolModules, entry, own, own)
 		}
 		if _, seen := by[module]; !seen {
 			order = append(order, module)
@@ -135,28 +153,7 @@ func Run(conn *bus.Conn, served []Served, envs map[string]map[string]string, log
 	node := conn.Node()
 
 	base := os.Environ()
-	envFor := func(module string) []string {
-		words := map[string]string{}
-		for _, kv := range base {
-			if k, v, ok := strings.Cut(kv, "="); ok && k != ToolEnv {
-				words[k] = v
-			}
-		}
-		for k, v := range envs[module] {
-			words[k] = v
-		}
-		words["MESH_SERVED_MODULE"] = module
-		words["MESH_MODULE"] = module
-		if node != "" {
-			words["MESH_NODE"] = node
-		}
-		out := make([]string, 0, len(words))
-		for k, v := range words {
-			out = append(out, k+"="+v)
-		}
-		sort.Strings(out)
-		return out
-	}
+	envFor := func(module string) []string { return BundleEnv(base, envs[module], module, node) }
 
 	// The module's events, for every child of it that subscribes (ADR 0198): one consumer per module,
 	// bound the first time any of its children subscribes, each event handed to every child that did.
@@ -458,6 +455,8 @@ type consumers struct {
 	logf func(string, ...any)
 	mu   sync.Mutex
 	of   map[string]*moduleEvents
+	// seatBound is each module's seat traffic bound once: a worker taken, a proof subject answered.
+	seatBound map[string]func()
 }
 
 type moduleEvents struct {
@@ -475,6 +474,10 @@ func (c *consumers) stopAll() {
 		}
 	}
 	c.of = map[string]*moduleEvents{}
+	for _, stop := range c.seatBound {
+		stop()
+	}
+	c.seatBound = map[string]func(){}
 }
 
 // forModule is the bus one launched bundle of a module reaches the mesh through.
@@ -604,9 +607,10 @@ func eventRef(env bus.Envelope) string {
 // stateAsked is what a bundle names when it reaches its state (ADR 0201): the state by the name its
 // module uses, a key, and for a put the value.
 type stateAsked struct {
-	State string          `json:"state"`
-	Key   string          `json:"key"`
-	Value json.RawMessage `json:"value"`
+	State    string          `json:"state"`
+	Key      string          `json:"key"`
+	Value    json.RawMessage `json:"value"`
+	Revision uint64          `json:"revision"`
 }
 
 // State answers a bundle's `get`, `put`, `delete` and `keys` on its module's state (ADR 0201). The
@@ -645,6 +649,20 @@ func (b *moduleBus) State(verb string, params json.RawMessage) (json.RawMessage,
 			return nil, err
 		}
 		answer = keys
+	case "create":
+		// Only when the key has no value: of two writers making it, one wins (novox/hq ADR 0259).
+		revision, err := conn.StateCreate(b.module, asked.State, asked.Key, asked.Value)
+		if err != nil {
+			return nil, err
+		}
+		answer = map[string]any{"revision": revision}
+	case "update":
+		// Only when the key is still at the revision read: a second answer to one ask loses (ADR 0259).
+		revision, err := conn.StateUpdate(b.module, asked.State, asked.Key, asked.Value, asked.Revision)
+		if err != nil {
+			return nil, err
+		}
+		answer = map[string]any{"revision": revision}
 	default:
 		return nil, fmt.Errorf("the runtime answers no mesh/state.%s", verb)
 	}
@@ -666,3 +684,124 @@ func (b *moduleBus) Watch(params json.RawMessage, deliver func(json.RawMessage)
 		return deliver(raw)
 	})
 }
+
+// seatAsked is what a bundle names for its seat traffic (novox/hq ADR 0259 §3).
+type seatAsked struct {
+	Subject string          `json:"subject"`
+	Body    json.RawMessage `json:"body"`
+	ID      string          `json:"id"`
+	Worker  string          `json:"worker"`
+	Bucket  string          `json:"bucket"`
+	Key     string          `json:"key"`
+}
+
+// Seat answers a bundle's seat traffic, each as the module and only as far as its membership lists:
+// `publish` an accept or an event, `prove` (ask a proof), `record` (read a record kept for it), `take` a
+// worker's work and `answer` a proof subject — the last two bound once per module and subject, each
+// message or proof handed to the module's child that asked last (novox/hq ADR 0259 §3).
+func (b *moduleBus) Seat(verb string, params json.RawMessage, handOn func(string, any) (json.RawMessage, error)) (json.RawMessage, error) {
+	var asked seatAsked
+	if err := json.Unmarshal(params, &asked); err != nil {
+		return nil, fmt.Errorf("mesh/seat.%s: %w", verb, err)
+	}
+	conn := b.all.conn
+	switch verb {
+	case "publish":
+		seq, duplicate, err := conn.SeatPublishSaid(b.module, asked.Subject, asked.Body, asked.ID)
+		if err != nil {
+			return nil, err
+		}
+		return json.Marshal(map[string]any{"sequence": seq, "duplicate": duplicate})
+	case "prove":
+		return conn.SeatProve(b.module, asked.Subject, asked.Body)
+	case "kinds":
+		kinds, err := conn.SeatKinds(b.module)
+		if err != nil {
+			return nil, err
+		}
+		return json.Marshal(kinds)
+	case "record":
+		entry, err := conn.SeatRecord(b.module, asked.Bucket, asked.Key)
+		if err != nil || entry == nil {
+			return json.RawMessage("null"), err
+		}
+		return json.Marshal(entry)
+	case "take":
+		key := "take " + asked.Worker
+		if b.bound(key) {
+			return json.RawMessage(`{}`), nil
+		}
+		stop, err := conn.SeatTake(b.module, asked.Worker, func(w bus.Work) error {
+			_, err := handOn("mesh/work", map[string]any{"work": w})
+			return err
+		})
+		if err != nil {
+			return nil, err
+		}
+		b.bind(key, stop)
+		b.all.logf("[mesh-tools] %s takes its work from %s", b.module, asked.Worker)
+		return json.RawMessage(`{}`), nil
+	case "answer":
+		key := "answer " + asked.Subject
+		if b.bound(key) {
+			return json.RawMessage(`{}`), nil
+		}
+		stop, err := conn.SeatAnswer(b.module, asked.Subject, func(subject string, body json.RawMessage) (json.RawMessage, error) {
+			return handOn("mesh/proof", map[string]any{"subject": subject, "body": body})
+		})
+		if err != nil {
+			return nil, err
+		}
+		b.bind(key, stop)
+		b.all.logf("[mesh-tools] %s answers the proofs on %s", b.module, asked.Subject)
+		return json.RawMessage(`{}`), nil
+	}
+	return nil, fmt.Errorf("the runtime answers no mesh/seat.%s", verb)
+}
+
+// bound and bind keep, per module, what its seat traffic is bound to, so a child that starts again and
+// asks again is handed what is already bound instead of a second reader of it.
+func (b *moduleBus) bound(key string) bool {
+	b.all.mu.Lock()
+	defer b.all.mu.Unlock()
+	_, ok := b.all.seatBound[b.module+" "+key]
+	return ok
+}
+
+func (b *moduleBus) bind(key string, stop func()) {
+	b.all.mu.Lock()
+	defer b.all.mu.Unlock()
+	if b.all.seatBound == nil {
+		b.all.seatBound = map[string]func(){}
+	}
+	b.all.seatBound[b.module+" "+key] = stop
+}
+
+// BundleEnv is what one module's bundle is started with: the runtime's environment without its own words,
+// the module's composed words over it, and the module's and machine's names. **No bus word reaches a
+// bundle** (security review of 2026-10-08): the credential and the bus's address are the runtime's, and a
+// bundle reaches the bus only through the runtime.
+func BundleEnv(base []string, given map[string]string, module, node string) []string {
+	words := map[string]string{}
+	for _, kv := range base {
+		if k, v, ok := strings.Cut(kv, "="); ok && !runtimeOnly[k] {
+			words[k] = v
+		}
+	}
+	for k, v := range given {
+		if !runtimeOnly[k] {
+			words[k] = v
+		}
+	}
+	words["MESH_SERVED_MODULE"] = module
+	words["MESH_MODULE"] = module
+	if node != "" {
+		words["MESH_NODE"] = node
+	}
+	out := make([]string, 0, len(words))
+	for k, v := range words {
+		out = append(out, k+"="+v)
+	}
+	sort.Strings(out)
+	return out
+}

node-tools/internal/runtime/seat_traffic_test.go

@@ -0,0 +1,149 @@
+package runtime
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+
+	"github.com/novox/mesh-tools/node-tools/internal/bus"
+	mt "github.com/novox/mesh-tools/node-tools/internal/meshtest"
+)
+
+// A bundle's seat traffic through moduleBus.Seat (novox/hq ADR 0259 §3), against a real bus: publish under
+// its own name with the id prefixed and a duplicate said; the record read without naming the bucket; a
+// worker and a proof subject bound once however often a restarted child asks; and nothing beyond what the
+// membership lists.
+func TestABundlesSeatTrafficGoesThroughItsModulesBus(t *testing.T) {
+	mesh := mt.New(t)
+	nc, err := nats.Connect(mt.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(nc.Close)
+	js, _ := nc.JetStream()
+	if _, err := js.AddStream(&nats.StreamConfig{Name: "SEAT_OPERATOR_CHANNEL", Retention: nats.WorkQueuePolicy,
+		Subjects: []string{"mesh.seat.operator-channel.accept.>"}}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.AddConsumer("SEAT_OPERATOR_CHANNEL", &nats.ConsumerConfig{Durable: "SEAT_OPERATOR_CHANNEL_worker",
+		AckPolicy: nats.AckExplicitPolicy, FilterSubject: "mesh.seat.operator-channel.accept.>"}); err != nil {
+		t.Fatal(err)
+	}
+	kv, err := js.CreateKeyValue(&nats.KeyValueConfig{Bucket: "messenger_asks"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, _ = kv.Put("mesh-delivery.d-1", []byte(`{"state":"open"}`))
+	asker := mt.MembershipOf("mesh-delivery", "anchor", false, nil)
+	asker.SeatTraffic = &bus.SeatTraffic{Publish: []string{"mesh.seat.operator-channel.accept.ask.mesh-delivery"},
+		Records: []string{"$JS.API.DIRECT.GET.KV_messenger_asks.$KV.messenger_asks.mesh-delivery.>"}}
+	router := mt.MembershipOf("messenger", "anchor", false, nil)
+	router.SeatTraffic = &bus.SeatTraffic{Answers: []string{"mesh.seat.intake.proof.code.*"},
+		Workers: []bus.SeatWorker{{Stream: "SEAT_OPERATOR_CHANNEL", Consumer: "SEAT_OPERATOR_CHANNEL_worker",
+			Filter: "mesh.seat.operator-channel.accept.>"}}}
+	mesh.Issue(t, asker)
+	mesh.Issue(t, router)
+	conn := connect(t, "node-tools", "anchor")
+	conn.Follow("mesh-delivery")
+	conn.Follow("messenger")
+	mt.Until(t, func() error {
+		if conn.Membership("mesh-delivery") == nil || conn.Membership("messenger") == nil {
+			return errors.New("not issued yet")
+		}
+		return nil
+	})
+	all := &consumers{conn: conn, logf: t.Logf, of: map[string]*moduleEvents{}}
+	asking := all.forModule("mesh-delivery").(*moduleBus)
+	routing := all.forModule("messenger").(*moduleBus)
+
+	publish := json.RawMessage(`{"subject":"mesh.seat.operator-channel.accept.ask.mesh-delivery","body":{"id":"d-1"},"id":"d-1"}`)
+	first, err := asking.Seat("publish", publish, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	again, _ := asking.Seat("publish", publish, nil)
+	if !strings.Contains(string(first), `"duplicate":false`) || !strings.Contains(string(again), `"duplicate":true`) {
+		t.Errorf("the same id twice: %s, then %s", first, again)
+	}
+	if _, err := asking.Seat("publish", json.RawMessage(`{"subject":"mesh.seat.operator-channel.accept.ask.mesh-controller","body":{}}`), nil); err == nil {
+		t.Error("a module submitted under another's name")
+	}
+	got, err := asking.Seat("record", json.RawMessage(`{"key":"d-1"}`), nil)
+	if err != nil || !strings.Contains(string(got), `"state":"open"`) {
+		t.Errorf("the record read without its bucket: %s %v", got, err)
+	}
+
+	var mu sync.Mutex
+	var taken []string
+	handOn := func(method string, params any) (json.RawMessage, error) {
+		mu.Lock()
+		defer mu.Unlock()
+		raw, _ := json.Marshal(params)
+		taken = append(taken, method+" "+string(raw))
+		return json.RawMessage(`{}`), nil
+	}
+	for i := 0; i < 2; i++ { // a child that started again asks again
+		if _, err := routing.Seat("take", json.RawMessage(`{"worker":"SEAT_OPERATOR_CHANNEL_worker"}`), handOn); err != nil {
+			t.Fatal(err)
+		}
+	}
+	deadline := time.Now().Add(10 * time.Second)
+	for {
+		mu.Lock()
+		n := len(taken)
+		mu.Unlock()
+		if n >= 1 || time.Now().After(deadline) {
+			break
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+	time.Sleep(300 * time.Millisecond)
+	mu.Lock()
+	if len(taken) != 1 || !strings.Contains(taken[0], "mesh/work") || !strings.Contains(taken[0], `"x-event-id":"mesh-delivery.d-1"`) {
+		t.Errorf("taken %v", taken)
+	}
+	mu.Unlock()
+	if _, err := asking.Seat("take", json.RawMessage(`{"worker":"SEAT_OPERATOR_CHANNEL_worker"}`), handOn); err == nil {
+		t.Error("an asker took the router's work")
+	}
+	if _, err := asking.Seat("answer", json.RawMessage(`{"subject":"mesh.seat.intake.proof.code.*"}`), handOn); err == nil {
+		t.Error("an asker answered proofs")
+	}
+	if _, err := asking.Seat("anything", json.RawMessage(`{}`), nil); err == nil {
+		t.Error("an unknown verb was answered")
+	}
+}
+
+// A lost compare-and-set is answered with its code, so the SDK knows it without reading words.
+func TestALostCompareAndSetCarriesItsCode(t *testing.T) {
+	mesh := mt.New(t)
+	mesh.Bucket(t, "messenger_asks")
+	m := mt.MembershipOf("messenger", "anchor", false, nil)
+	m.State = []bus.StateIssued{{Name: "asks", Bucket: "messenger_asks", Writes: true}}
+	mesh.Issue(t, m)
+	conn := connect(t, "node-tools", "anchor")
+	conn.Follow("messenger")
+	mt.Until(t, func() error {
+		if conn.Membership("messenger") == nil {
+			return errors.New("not issued yet")
+		}
+		return nil
+	})
+	b := (&consumers{conn: conn, logf: t.Logf, of: map[string]*moduleEvents{}}).forModule("messenger")
+	if _, err := b.State("create", json.RawMessage(`{"state":"asks","key":"a","value":{}}`)); err != nil {
+		t.Fatal(err)
+	}
+	_, err := b.State("create", json.RawMessage(`{"state":"asks","key":"a","value":{}}`))
+	var coded interface{ ErrorCode() int }
+	if !errors.As(err, &coded) || coded.ErrorCode() != -32010 || !errors.Is(err, bus.ErrStateChanged) {
+		t.Errorf("a second create: %v", err)
+	}
+	if _, err := b.State("update", json.RawMessage(`{"state":"asks","key":"a","value":{},"revision":0}`)); err == nil {
+		t.Error("an update of revision zero was taken")
+	}
+}