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)

node-tools/internal/bus/seat.go

@@ -64,6 +64,20 @@ type SeatWorker struct {
 // 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, ".")
@@ -122,18 +136,29 @@ func newID() string {
 // 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, fmt.Errorf("%s is a proof, asked and answered, never kept: ask it as one", subject)
+		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, err
+		return 0, false, err
 	}
 	if len(body) == 0 || !json.Valid(body) {
-		return 0, fmt.Errorf("what is said on %s is JSON", subject)
+		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)
@@ -143,9 +168,9 @@ func (c *Conn) SeatPublish(module, subject string, body json.RawMessage, id stri
 	msg.Data = body
 	ack, err := c.js.PublishMsg(msg, nats.MsgId(id))
 	if err != nil {
-		return 0, err
+		return 0, false, err
 	}
-	return ack.Sequence, nil
+	return ack.Sequence, ack.Duplicate, nil
 }
 
 // SeatProve asks a proof and answers its reply: core request and reply, on no stream.
@@ -263,12 +288,38 @@ func (c *Conn) SeatTake(module, consumer string, deliver func(Work) error) (func
 		for k := range msg.Headers() {
 			headers[k] = msg.Headers().Get(k)
 		}
-		if err := deliver(Work{Worker: w.Consumer, Subject: msg.Subject(), Body: json.RawMessage(msg.Data()), Headers: headers}); err != nil {
-			_ = msg.NakWithDelay(NakDelay)
+		// 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)
 	}
@@ -286,6 +337,20 @@ func (c *Conn) SeatRecord(module, bucket, key string) (*StateEntry, error) {
 	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)",
@@ -319,6 +384,10 @@ func (c *Conn) StateCreate(module, name, key string, value json.RawMessage) (uin
 // 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)
 	})
@@ -327,6 +396,13 @@ func (c *Conn) StateUpdate(module, name, key string, value json.RawMessage, revi
 // 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)
@@ -351,7 +427,7 @@ func (c *Conn) stateWrite(module, name, key string, value json.RawMessage,
 	}
 	rev, err := write(ctx, kv)
 	if errors.Is(err, jetstream.ErrKeyExists) || isWrongSequence(err) {
-		return 0, fmt.Errorf("%s.%s: %w", name, key, ErrStateChanged)
+		return 0, changed{name + "." + key}
 	}
 	return rev, err
 }

node-tools/internal/launch/launch.go

@@ -181,12 +181,6 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 	start := func() (*child, error) {
 		cmd := exec.Command(entry)
 		cmd.Env = env
-		// **A module that names an account of its own runs as it** (novox/hq ADR 0259 §8): its secrets and
-		// state are that account's, and the operator's account — which every agent runs as — reaches
-		// neither. Never root, never the operator's.
-		if err := runAs(cmd, env); err != nil {
-			return nil, err
-		}
 		stdin, err := cmd.StdinPipe()
 		if err != nil {
 			return nil, err
@@ -310,7 +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})
@@ -599,3 +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/runas.go

@@ -1,68 +0,0 @@
-package launch
-
-import (
-	"fmt"
-	"os/exec"
-	"os/user"
-	"strconv"
-	"strings"
-	"syscall"
-)
-
-// RunAs is the word in a bundle's environment naming the account it runs as (novox/hq ADR 0259 §8), and
-// OperatorAccount the word naming the operator's account on this machine, which the runtime is given.
-const (
-	RunAs           = "MESH_RUN_AS"
-	OperatorAccount = "MESH_OPERATOR_ACCOUNT"
-)
-
-// lookupUser is user.Lookup, a variable so a test can name accounts this machine does not have.
-var lookupUser = user.Lookup
-
-func word(env []string, name string) string {
-	for _, kv := range env {
-		if k, v, ok := strings.Cut(kv, "="); ok && k == name {
-			return v
-		}
-	}
-	return ""
-}
-
-// runAs starts cmd as the account its environment names, with that account's home, or leaves it as the
-// runtime's own when none is named. It refuses root and the operator's account: a module asks for an
-// account of its own to keep what it holds from the agents, and every agent runs as the operator.
-func runAs(cmd *exec.Cmd, env []string) error {
-	name := word(env, RunAs)
-	if name == "" {
-		return nil
-	}
-	if operator := word(env, OperatorAccount); operator != "" && name == operator {
-		return fmt.Errorf("%s names the operator's account %s; a module runs as an account of its own, never "+
-			"the one every agent runs as (novox/hq ADR 0259)", RunAs, name)
-	}
-	u, err := lookupUser(name)
-	if err != nil {
-		return fmt.Errorf("%s names the account %s, which this machine does not have: the module makes it with "+
-			"a user resource (novox/hq ADR 0259): %w", RunAs, name, err)
-	}
-	uid, err := strconv.ParseUint(u.Uid, 10, 32)
-	if err != nil {
-		return fmt.Errorf("the account %s has no usable uid %q", name, u.Uid)
-	}
-	gid, err := strconv.ParseUint(u.Gid, 10, 32)
-	if err != nil {
-		return fmt.Errorf("the account %s has no usable gid %q", name, u.Gid)
-	}
-	if uid == 0 || name == "root" {
-		return fmt.Errorf("%s names root; a module that asks for an account of its own is not given root", RunAs)
-	}
-	cmd.SysProcAttr = &syscall.SysProcAttr{Credential: &syscall.Credential{Uid: uint32(uid), Gid: uint32(gid)}}
-	var kept []string
-	for _, kv := range cmd.Env {
-		if !strings.HasPrefix(kv, "HOME=") && !strings.HasPrefix(kv, "USER=") && !strings.HasPrefix(kv, "LOGNAME=") {
-			kept = append(kept, kv)
-		}
-	}
-	cmd.Env = append(kept, "HOME="+u.HomeDir, "USER="+name, "LOGNAME="+name)
-	return nil
-}

node-tools/internal/launch/runas_test.go

@@ -1,48 +0,0 @@
-package launch
-
-import (
-	"errors"
-	"os/exec"
-	"os/user"
-	"strings"
-	"testing"
-)
-
-// novox/hq ADR 0259 §8: a module naming an account of its own runs as it, never as root or the operator.
-func TestABundleRunsAsTheAccountItNamesAndNeverRootOrTheOperator(t *testing.T) {
-	was := lookupUser
-	t.Cleanup(func() { lookupUser = was })
-	lookupUser = func(name string) (*user.User, error) {
-		switch name {
-		case "telegram":
-			return &user.User{Username: "telegram", Uid: "961", Gid: "961", HomeDir: "/var/lib/telegram"}, nil
-		case "root":
-			return &user.User{Username: "root", Uid: "0", Gid: "0", HomeDir: "/root"}, nil
-		case "toor":
-			return &user.User{Username: "toor", Uid: "0", Gid: "0", HomeDir: "/root"}, nil
-		}
-		return nil, errors.New("unknown user")
-	}
-	cmd := exec.Command("/bin/true")
-	cmd.Env = []string{"HOME=/root", "PATH=/usr/bin"}
-	if err := runAs(cmd, []string{RunAs + "=telegram", OperatorAccount + "=jo"}); err != nil {
-		t.Fatal(err)
-	}
-	if c := cmd.SysProcAttr.Credential; c == nil || c.Uid != 961 || c.Gid != 961 {
-		t.Fatalf("not started as telegram: %+v", cmd.SysProcAttr)
-	}
-	if env := strings.Join(cmd.Env, " "); !strings.Contains(env, "HOME=/var/lib/telegram") || strings.Contains(env, "HOME=/root") {
-		t.Fatalf("the account's home is not its own: %s", env)
-	}
-	for name, want := range map[string]string{"jo": "operator's account", "root": "names root", "toor": "names root",
-		"nobody-here": "does not have"} {
-		err := runAs(exec.Command("/bin/true"), []string{RunAs + "=" + name, OperatorAccount + "=jo"})
-		if err == nil || !strings.Contains(err.Error(), want) {
-			t.Errorf("%s: %v, want a refusal saying %q", name, err, want)
-		}
-	}
-	plain := exec.Command("/bin/true")
-	if err := runAs(plain, nil); err != nil || plain.SysProcAttr != nil {
-		t.Error("a bundle naming no account was changed")
-	}
-}

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.
@@ -710,11 +707,11 @@ func (b *moduleBus) Seat(verb string, params json.RawMessage, handOn func(string
 	conn := b.all.conn
 	switch verb {
 	case "publish":
-		seq, err := conn.SeatPublish(b.module, asked.Subject, asked.Body, asked.ID)
+		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})
+		return json.Marshal(map[string]any{"sequence": seq, "duplicate": duplicate})
 	case "prove":
 		return conn.SeatProve(b.module, asked.Subject, asked.Body)
 	case "kinds":
@@ -779,3 +776,32 @@ func (b *moduleBus) bind(key string, stop 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")
+	}
+}