diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
index 5f0c0ede..0686c755 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
@@ -289,14 +289,17 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	// The inputs of the composition steps it asks a build seat to run: the seat mesh-wants' verb input is answered here in chunks
 	// of the core connection, of any size (design 47 G §354, §712, A-237).
 	inputs := inputsOver(kvs[buckets.Inputs], js, account.Module, logger.Printf)
+	// The seat list (seatlist.go), followed in follow over the connection and the hub: the verb input's callers are checked
+	// against the seat's definition it holds (A-186).
+	gate := seatlist.NewPart("assigner", seatListAgainCallers)
 	if inputs != nil {
-		stopInput, err := said.AnswerSeat(meshwants.Seat, map[string]process.SeatHandler{meshwants.VerbInput: inputs.verb(conn, buscalls.SeatAckWithin)})
+		stopInput, err := said.AnswerSeat(meshwants.Seat, seatDefinition(gate, meshwants.Seat), map[string]process.SeatHandler{meshwants.VerbInput: inputs.verb(conn, buscalls.SeatAckWithin)})
 		if err != nil {
 			return fmt.Errorf("answering the verb input: %w", err)
 		}
 		defer stopInput()
 	}
-	return follow(ctx, js, conn, kvs, findings.Say(sayVia(ctx, js)), findings, emitting{said}, iv, inputs, logger, getenv)
+	return follow(ctx, js, conn, kvs, findings.Say(sayVia(ctx, js)), findings, emitting{said}, iv, inputs, gate, logger, getenv)
 }
 
 // findingsOf is where the assigner's said conditions go as findings (issue 1952 WM6): its findings bucket, which the
@@ -379,7 +382,7 @@ var watched = []string{
 
 // follow watches every bucket a pass reads and makes a pass at start, once every watch handed what stands, and after
 // each change; changes that come during a pass make one more. It returns when ctx ends or a watch ends.
-func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber, kvs kvSet, say func(oc.Condition) error, findings assign.Findings, bus caller, iv *catalogViews, inputs *inputKeeper, logger *log.Logger, getenv func(string) string) error {
+func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber, kvs kvSet, say func(oc.Condition) error, findings assign.Findings, bus caller, iv *catalogViews, inputs *inputKeeper, gate *seatlist.Part, logger *log.Logger, getenv func(string) string) error {
 	w := newWorld()
 	dirty := make(chan struct{}, 1)
 	wake := func() {
@@ -498,7 +501,6 @@ func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber,
 	hub := process.NewEventHub(logger.Printf)
 	// The seat list (seatlist.go), read over the connection and heard on the hub, given to catalogue at every change, and a
 	// pass made then: registered before the hub starts.
-	gate := seatlist.NewPart("assigner", seatListAgainCallers)
 	if bus != nil {
 		gate.Follow(seatlist.ProcessBus(bus.Call, hub), wake, logger.Printf)
 	}
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main_test.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main_test.go
index 31676cef..5c0c3c8a 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main_test.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main_test.go
@@ -28,6 +28,7 @@ import (
 	oc "git.novox.be/novox/mesh-contracts/operator-and-conversation/go/seats/operatorchannel"
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
 )
 
 // 1297/B2a: the buckets the program opens are exactly the manifest's reads and states, as the broker names them
@@ -124,7 +125,7 @@ func TestOpensWhatItsManifestNames(t *testing.T) {
 	}
 	kvs[buckets.Puts].(*watchKV).closed = true
 	kvs[buckets.Wants].(*watchKV).wrote = wrote
-	go follow(ctx, nil, nil, kvs, func(oc.Condition) error { return nil }, assign.Findings{}, nil, nil, nil, log.New(io.Discard, "", 0), func(string) string { return "" })
+	go follow(ctx, nil, nil, kvs, func(oc.Condition) error { return nil }, assign.Findings{}, nil, nil, nil, seatlist.NewPart("assigner", seatListAgainCallers), log.New(io.Discard, "", 0), func(string) string { return "" })
 	select {
 	case key := <-wrote:
 		if key != "want.ace.node" {
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist.go
index 61e8d076..2c045320 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist.go
@@ -1,6 +1,11 @@
 package main
 
-import stdio "git.novox.be/novox/mesh-sdk/go"
+import (
+	"git.novox.be/novox/mesh-sdk/go/seatdef"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
 
 // The assigner reads the seat list as every part does, through mesh-sdk's one wiring (go/seatlist.Part; design 47 G §204): its
 // reader over the seat mesh-catalog's verb seat-definitions and its two events, its tools `assigner_seat_list` and
@@ -11,3 +16,17 @@ import stdio "git.novox.be/novox/mesh-sdk/go"
 // A call through the mesh MCP server is proved only as its machine's tool runner (<node>.node-tools, issue 627), so
 // node-tools stands for an operator's session until a session is proved (issue 1966).
 var seatListAgainCallers = []string{stdio.AnyPerson, "node-tools", "mesh-healers"}
+
+// seatDefinition is the definition of seat the gate's seat list holds, which the seat's verbs answered here check their
+// callers against (process.Conn.AnswerSeat; design 47 G lead answers A-179, A-186): false until the seat mesh-catalog has
+// answered the list, so the assigner answers a verb only once its seat list is read, and false for a seat it does not hold.
+func seatDefinition(gate *seatlist.Part, seat string) func() (seatdef.Definition, bool) {
+	return func() (seatdef.Definition, bool) {
+		r := gate.Reader()
+		if r == nil || !r.Status().Heard {
+			return seatdef.Definition{}, false
+		}
+		d, ok := r.Definitions()[seat]
+		return d, ok
+	}
+}
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist_test.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist_test.go
index 8cf119c9..65e7e7e5 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist_test.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seatlist_test.go
@@ -94,3 +94,21 @@ func TestTheSeatListIsWiredByTheSDKAlone(t *testing.T) {
 		}
 	}
 }
+
+// A-179, A-186: the definition the verb input's callers are checked against is the seat list's, none before the reader starts
+// or while the seat mesh-catalog has not answered, and none for a seat the list does not hold.
+func TestTheAnsweredSeatsDefinitionIsTheSeatListsOnceRead(t *testing.T) {
+	if _, ok := seatDefinition(seatlist.NewPart("assigner", seatListAgainCallers), "mesh-wants")(); ok {
+		t.Error("a definition is answered before the seat list's reader started")
+	}
+	if _, ok := seatDefinition(gateOver(t, true), "mesh-wants")(); ok {
+		t.Error("a definition is answered while the seat mesh-catalog has not answered the list")
+	}
+	read := gateOver(t, false)
+	if d, ok := seatDefinition(read, "mesh-wants")(); !ok || d.Seat != "mesh-wants" {
+		t.Errorf("the read list's mesh-wants is answered as %v, %v", d.Seat, ok)
+	}
+	if _, ok := seatDefinition(read, "no-such-seat")(); ok {
+		t.Error("a seat the list does not hold is answered a definition")
+	}
+}
diff --git a/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/main.go b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/main.go
index 4aaa8bc2..28b1a2f2 100644
--- a/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/main.go
+++ b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/main.go
@@ -405,7 +405,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	b.StepEntry = newEntryWaits(branches, half.manifests).entry
 	// The seat mesh-builds' verb reserved, answered here (A-115, A-127): the reservations, the catalog half's carriers and the seat
 	// mesh-catalog's versions.
-	stopReserved, err := calls.AnswerSeat(meshbuilds.Seat, map[string]process.SeatHandler{
+	stopReserved, err := calls.AnswerSeat(meshbuilds.Seat, seatGate.definition(meshbuilds.Seat), map[string]process.SeatHandler{
 		meshbuilds.VerbReserved: reservedVerb(ctx, reservedReader(ctx, reserved.r.Store), versions.CarriersFrom(versions.EntriesOf(branches)), catalogReleased(calls.Call))})
 	if err != nil {
 		return fmt.Errorf("answering the verb reserved: %w", err)
diff --git a/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist.go b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist.go
index 7d96edc9..76a12f0a 100644
--- a/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist.go
+++ b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist.go
@@ -24,3 +24,17 @@ func (g *seatGate) definitions() map[string]seatdef.Definition {
 	}
 	return nil
 }
+
+// definition is the definition of seat the list holds, which the seat's verbs answered here check their callers against
+// (process.Conn.AnswerSeat; design 47 G lead answers A-179, A-186): false until the seat mesh-catalog has answered the list, so
+// the builder answers a verb only once its seat list is read, and false for a seat it does not hold.
+func (g *seatGate) definition(seat string) func() (seatdef.Definition, bool) {
+	return func() (seatdef.Definition, bool) {
+		r := g.Reader()
+		if r == nil || !r.Status().Heard {
+			return seatdef.Definition{}, false
+		}
+		d, ok := r.Definitions()[seat]
+		return d, ok
+	}
+}
diff --git a/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist_test.go b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist_test.go
new file mode 100644
index 00000000..a5e1d795
--- /dev/null
+++ b/modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seatlist_test.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/busretry"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
+)
+
+// listingCatalog is the seat mesh-catalog as the reader asks it: an empty listing, so the bootstrapped definitions stand, or,
+// silent, no answer at all.
+type listingCatalog struct{ silent bool }
+
+func (c listingCatalog) Ask(string, any) (json.RawMessage, error) {
+	if c.silent {
+		return nil, errors.New("no responders")
+	}
+	return json.Marshal(seatlist.Listing{Revision: 1})
+}
+
+func (listingCatalog) Subscribe(string, func(string, json.RawMessage) error) error { return nil }
+
+// A-179, A-186: the definition the verb reserved's callers are checked against is the seat list's, none before the reader
+// starts or while the seat mesh-catalog has not answered, and none for a seat the list does not hold.
+func TestTheAnsweredSeatsDefinitionIsTheSeatListsOnceRead(t *testing.T) {
+	t.Cleanup(busretry.Waits(20*time.Millisecond, time.Millisecond, 5*time.Millisecond))
+	follow := func(silent bool) *seatGate {
+		g := newSeatGate()
+		if r := g.Follow(listingCatalog{silent: silent}, nil, t.Logf); r != nil {
+			<-r.Ready()
+		}
+		return g
+	}
+	if _, ok := newSeatGate().definition(seatlist.Seat)(); ok {
+		t.Error("a definition is answered before the seat list's reader started")
+	}
+	if _, ok := follow(true).definition(seatlist.Seat)(); ok {
+		t.Error("a definition is answered while the seat mesh-catalog has not answered the list")
+	}
+	read := follow(false)
+	if d, ok := read.definition(seatlist.Seat)(); !ok || d.Seat != seatlist.Seat {
+		t.Errorf("the read list's %s is answered as %q, %v", seatlist.Seat, d.Seat, ok)
+	}
+	if _, ok := read.definition("no-such-seat")(); ok {
+		t.Error("a seat the list does not hold is answered a definition")
+	}
+}
diff --git a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/input_integration_test.go b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/input_integration_test.go
index 91048da9..79cc3adc 100644
--- a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/input_integration_test.go
+++ b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/input_integration_test.go
@@ -10,6 +10,8 @@ import (
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
+	"strings"
 	"testing"
 	"time"
 
@@ -38,6 +40,10 @@ func TestIndexerAnswersARunsInputOverOneMiBInChunks(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
+		// The indexer's own seat list (A-186), its state seat-definitions: empty, so the bootstrapped mesh-catalog stands.
+		if _, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: index.SeatDefinitionsBucket, History: 5}); err != nil {
+			t.Fatal(err)
+		}
 		objs, err := js.CreateObjectStore(ctx, jetstream.ObjectStoreConfig{Bucket: catalogue.BusName(index.Module, catalogue.StateObjectsName(index.InputsState))})
 		if err != nil {
 			t.Fatal(err)
@@ -62,12 +68,17 @@ func TestIndexerAnswersARunsInputOverOneMiBInChunks(t *testing.T) {
 		Error  string                  `json:"error"`
 	}
 	for deadline := time.Now().Add(30 * time.Second); ; time.Sleep(100 * time.Millisecond) {
-		m, err := nc.Request("mesh.seat.mesh-catalog.tool.input", req, 5*time.Second)
+		// A caller the bus proved, on the subject naming it (A-179); refused while the indexer's seat list is unread (A-186).
+		m, err := nc.Request("mesh.seat.mesh-catalog.call.input.agent~dev", req, 5*time.Second)
 		if err == nil {
+			reply.Error = ""
 			if err := json.Unmarshal(m.Data, &reply); err != nil {
 				t.Fatal(err)
 			}
-			break
+			if !strings.Contains(reply.Error, "not yet read") {
+				break
+			}
+			err = errors.New(reply.Error)
 		}
 		if time.Now().After(deadline) {
 			t.Fatalf("the verb input is not answered within 30 s: %v", err)
diff --git a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main.go b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main.go
index 0c37ff93..8acd43e2 100644
--- a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main.go
+++ b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/main.go
@@ -450,7 +450,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	// connection, of any size (design 47 G §712, A-237).
 	inputsStore := awaitedStore{b: process.AwaitBucket(ctx, js, conn, index.InputsBucket, "no input of a run ask is kept, so the verb input answers none", logger.Printf)}
 	inObjects := &inputObjects{js: js, module: cred.Module}
-	stopInput, err := calls.AnswerSeat(meshcatalog.Seat, map[string]process.SeatHandler{
+	stopInput, err := calls.AnswerSeat(meshcatalog.Seat, seatDefinition(seatReader, meshcatalog.Seat), map[string]process.SeatHandler{
 		meshcatalog.VerbInput: index.InputVerb(inputsStore, inObjects, conn, buscalls.SeatAckWithin, logger.Printf)})
 	if err != nil {
 		return fmt.Errorf("answering the verb input: %w", err)
diff --git a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist.go b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist.go
index 8a2ebea9..759a039b 100644
--- a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist.go
+++ b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist.go
@@ -10,6 +10,7 @@ import (
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/seatdef"
 	"git.novox.be/novox/mesh-sdk/go/seatlist"
 	"git.novox.be/novox/mesh-sdk/go/views"
 
@@ -141,3 +142,17 @@ func readWhenBound(part *seatlist.Part, states ...bucket) {
 
 // toolPrefix is the prefix of the indexer's tools, its manifest's slug.
 const toolPrefix = "indexer"
+
+// seatDefinition is the definition of seat the indexer's seat list holds, which the seat's verbs answered here check their
+// callers against (process.Conn.AnswerSeat; design 47 G lead answers A-179, A-186): false until the list is read, so the
+// indexer answers a verb only once its seat list is read, and false for a seat it does not hold.
+func seatDefinition(part *seatlist.Part, seat string) func() (seatdef.Definition, bool) {
+	return func() (seatdef.Definition, bool) {
+		r := part.Reader()
+		if r == nil || !r.Status().Heard {
+			return seatdef.Definition{}, false
+		}
+		d, ok := r.Definitions()[seat]
+		return d, ok
+	}
+}
diff --git a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist_test.go b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist_test.go
index 1773a17b..e12a1dba 100644
--- a/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist_test.go
+++ b/modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/seatlist_test.go
@@ -50,6 +50,13 @@ func TestTheSeatListIsReadAgainWhenItsStatesAreBound(t *testing.T) {
 	if reader.Status().Heard {
 		t.Fatal("the list was read with its states missing")
 	}
+	// A-179, A-186: the definition the verb input's callers are checked against is the list's once read, none before.
+	if _, ok := seatDefinition(seatlist.NewPart(toolPrefix, nil), seatlist.Seat)(); ok {
+		t.Error("a definition is answered before the seat list's reader started")
+	}
+	if _, ok := seatDefinition(part, seatlist.Seat)(); ok {
+		t.Error("a definition is answered while the list is unread")
+	}
 	b := &awaitedFake{}
 	readWhenBound(part, b)
 	src.mu.Lock()
@@ -63,5 +70,11 @@ func TestTheSeatListIsReadAgainWhenItsStatesAreBound(t *testing.T) {
 			t.Fatal("the list was not read after its states were bound")
 		}
 	}
+	if d, ok := seatDefinition(part, seatlist.Seat)(); !ok || d.Seat != seatlist.Seat {
+		t.Errorf("the read list's %s is answered as %q, %v", seatlist.Seat, d.Seat, ok)
+	}
+	if _, ok := seatDefinition(part, "no-such-seat")(); ok {
+		t.Error("a seat the list does not hold is answered a definition")
+	}
 	var _ seatlist.Bus = bus
 }
diff --git a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/main.go b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/main.go
index 8e593380..024d800d 100644
--- a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/main.go
+++ b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/main.go
@@ -21,6 +21,7 @@ import (
 	catalog "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshcatalog"
 	seat "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshpipelinerunner"
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
 
 	"mesh-delivery-pipeline/internal/pipeline"
 )
@@ -246,11 +247,15 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	// An entry whose step ended and was not appended is appended at the start, in order (§606, §549).
 	hearer.AppendUnlogged()
 	go whileTheLogIsFull(ctx, fills, hearer, time.Minute)
-	if err := hub.StartUntilBound(ctx, js, cred, nil, nil); err != nil {
+	// The seat list, read over the calls connection and heard on the hub (seatlist.Part), which the seat's write verbs check
+	// their callers against (A-186): registered before the hub starts, read again once its events are live.
+	seats := seatlist.NewPart("runner", nil)
+	seats.Follow(seatlist.ProcessBus(calls.Call, hub), nil, logger.Printf)
+	if err := hub.StartUntilBound(ctx, js, cred, nil, seats.EventsLive); err != nil {
 		logger.Printf("the consumer %s is not bound yet (%v): bound once the bus makes it", cred.EventConsumerName(), err)
 	}
 	// The seat's write verbs are answered here, by the process that holds the pipelines (A-107).
-	stopVerbs, err := answerVerbs(calls, writeVerbs(ctx, hearer, starter, func(branch string) (pipeline.Half, bool) { return rv.Catalog.View(branch) }, calls, bounds))
+	stopVerbs, err := answerVerbs(calls, seats, writeVerbs(ctx, hearer, starter, func(branch string) (pipeline.Half, bool) { return rv.Catalog.View(branch) }, calls, bounds))
 	if err != nil {
 		return err
 	}
diff --git a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/run_integration_test.go b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/run_integration_test.go
index 293c9da3..1f3f9581 100644
--- a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/run_integration_test.go
+++ b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/run_integration_test.go
@@ -9,6 +9,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -21,6 +22,7 @@ import (
 	seat "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshpipelinerunner"
 	"git.novox.be/novox/mesh-sdk/go/buscompose"
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
 	"git.novox.be/novox/mesh-sdk/go/testbus"
 
 	"mesh-delivery-pipeline/internal/pipeline"
@@ -94,6 +96,28 @@ func TestTheRunnerPlacesAPipelineAsksItsBuildTakesItsEndAndAnswersAReview(t *tes
 	answer("mesh.seat.mesh-catalog.call.registrations.*", catalog.RegistrationsAnswer{Registrations: []catalog.Registration{reg}})
 	answer("mesh.seat.mesh-catalog.call.revision.*", catalog.RevisionAnswer{NoneYet: true})
 	answer("mesh.seat.mesh-hand-acts.call.hand-act.*", map[string]any{})
+	// The seat list (A-186): the seat mesh-catalog's seat-definitions names the runner's seat, whose definition its write
+	// verbs' callers are checked against, as the contracts' file holds it.
+	def, err := os.ReadFile("../../../mesh-delivery-contracts/seats/mesh-pipeline-runner/seat.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := nc.Subscribe("mesh.seat.mesh-catalog.call."+seatlist.Verb+".*", func(m *nats.Msg) {
+		var in struct {
+			Seat string `json:"seat"`
+		}
+		_ = json.Unmarshal(m.Data, &in)
+		entry := seatlist.Entry{Seat: seat.Seat, Source: seatlist.SourceTrunk, Digest: "sha256:runner"}
+		var result any = seatlist.Listing{Revision: 1, Seats: []seatlist.Entry{entry}}
+		if in.Seat != "" {
+			entry.Definition = def
+			result = seatlist.Answer{Seat: in.Seat, Found: in.Seat == seat.Seat, Entry: &entry, Revision: 1}
+		}
+		raw, _ := json.Marshal(map[string]any{"result": result})
+		_ = m.Respond(raw)
+	}); err != nil {
+		t.Fatal(err)
+	}
 
 	dir := t.TempDir()
 	broker := filepath.Join(dir, "broker")
@@ -145,7 +169,9 @@ func TestTheRunnerPlacesAPipelineAsksItsBuildTakesItsEndAndAnswersAReview(t *tes
 	}
 	waitFor(t, ctx, logs, func() bool {
 		m, err := nc.Request("mesh.seat.mesh-pipeline-runner.call.review.agent~dev", in, 2*time.Second)
-		return err == nil && json.Unmarshal(m.Data, &reply) == nil
+		reply.Error = ""
+		// Until the runner's seat list is read, every caller is refused (A-186): asked again until it is.
+		return err == nil && json.Unmarshal(m.Data, &reply) == nil && !strings.Contains(reply.Error, "not yet read")
 	})
 	if reply.Error != "" || reply.Result.Pipeline != key || reply.Result.Result.By != "agent.dev" || reply.Result.Result.Outcome != "passed" {
 		t.Fatalf("review answered %+v (%s)", reply.Result, reply.Error)
diff --git a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs.go b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs.go
index a5816073..dbf008e0 100644
--- a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs.go
+++ b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs.go
@@ -12,6 +12,8 @@ import (
 	catalog "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshcatalog"
 	seat "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshpipelinerunner"
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/seatdef"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
 
 	"mesh-delivery-pipeline/internal/pipeline"
 )
@@ -34,9 +36,23 @@ func verbOf[In any](do func(caller string, in In) (any, error)) process.SeatHand
 }
 
 // answerVerbs answers the seat's write verbs over the bus, each writing the state pipelines by compare-and-set (design 47
-// G §22, §70, §306, §482, A-107). The returned stop ends the answers.
-func answerVerbs(conn *process.Conn, v pipeline.Verbs) (func(), error) {
-	return conn.AnswerSeat(seat.Seat, writeHandlers(v))
+// G §22, §70, §306, §482, A-107), each call's caller checked against the seat's definition the runner's seat list holds
+// (A-179, A-186). The returned stop ends the answers.
+func answerVerbs(conn *process.Conn, seats *seatlist.Part, v pipeline.Verbs) (func(), error) {
+	return conn.AnswerSeat(seat.Seat, seatDefinition(seats, seat.Seat), writeHandlers(v))
+}
+
+// seatDefinition is the definition of seat the runner's seat list holds (A-186): false until the seat mesh-catalog has
+// answered the list, so the runner answers a verb only once its seat list is read, and false for a seat it does not hold.
+func seatDefinition(seats *seatlist.Part, name string) func() (seatdef.Definition, bool) {
+	return func() (seatdef.Definition, bool) {
+		r := seats.Reader()
+		if r == nil || !r.Status().Heard {
+			return seatdef.Definition{}, false
+		}
+		d, ok := r.Definitions()[name]
+		return d, ok
+	}
 }
 
 // writeHandlers are the seat's write verbs the process answers: run, review, rerun, accept, cancel, start, ask-again and
diff --git a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs_test.go b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs_test.go
index 9cb87105..6368b5cd 100644
--- a/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs_test.go
+++ b/modules/mesh-delivery-pipeline/cmd/mesh-delivery-pipeline/verbs_test.go
@@ -2,8 +2,13 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"slices"
 	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/busretry"
+	"git.novox.be/novox/mesh-sdk/go/seatlist"
 
 	seat "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshpipelinerunner"
 
@@ -40,3 +45,42 @@ func TestAVerbIsAnsweredOnlyForAProvedCallerAndItsOwnInput(t *testing.T) {
 		t.Errorf("answer = %v, %v, input %+v", out, err, got)
 	}
 }
+
+// listingCatalog is the seat mesh-catalog as the reader asks it: an empty listing, so the bootstrapped definitions stand, or,
+// silent, no answer at all.
+type listingCatalog struct{ silent bool }
+
+func (c listingCatalog) Ask(string, any) (json.RawMessage, error) {
+	if c.silent {
+		return nil, errors.New("no responders")
+	}
+	return json.Marshal(seatlist.Listing{Revision: 1})
+}
+
+func (listingCatalog) Subscribe(string, func(string, json.RawMessage) error) error { return nil }
+
+// A-179, A-186: the definition the write verbs' callers are checked against is the seat list's, none before the reader starts
+// or while the seat mesh-catalog has not answered, and none for a seat the list does not hold.
+func TestTheAnsweredSeatsDefinitionIsTheSeatListsOnceRead(t *testing.T) {
+	t.Cleanup(busretry.Waits(20*time.Millisecond, time.Millisecond, 5*time.Millisecond))
+	follow := func(silent bool) *seatlist.Part {
+		p := seatlist.NewPart("runner", nil)
+		if r := p.Follow(listingCatalog{silent: silent}, nil, t.Logf); r != nil {
+			<-r.Ready()
+		}
+		return p
+	}
+	if _, ok := seatDefinition(seatlist.NewPart("runner", nil), seatlist.Seat)(); ok {
+		t.Error("a definition is answered before the seat list's reader started")
+	}
+	if _, ok := seatDefinition(follow(true), seatlist.Seat)(); ok {
+		t.Error("a definition is answered while the seat mesh-catalog has not answered the list")
+	}
+	read := follow(false)
+	if d, ok := seatDefinition(read, seatlist.Seat)(); !ok || d.Seat != seatlist.Seat {
+		t.Errorf("the read list's %s is answered as %q, %v", seatlist.Seat, d.Seat, ok)
+	}
+	if _, ok := seatDefinition(read, seat.Seat)(); ok {
+		t.Error("a seat the list does not hold is answered a definition")
+	}
+}
diff --git a/modules/mesh-delivery-pipeline/manifest_test.go b/modules/mesh-delivery-pipeline/manifest_test.go
index 81f65253..ea6925a7 100644
--- a/modules/mesh-delivery-pipeline/manifest_test.go
+++ b/modules/mesh-delivery-pipeline/manifest_test.go
@@ -78,10 +78,14 @@ func TestManifest(t *testing.T) {
 			"mesh-delivery-indexer.take-in.taken", "mesh-builds.package-published", "mesh-builds.toolchain-agreed", "mesh-builds.step-ended", "mesh-delivery-builder.build.ended.**",
 			"operator-channel.decided", "node-build-go.step-ended", "node-build-node.step-ended",
 			"node-build-image.step-ended", "node-build-go.ask-taken", "node-build-node.ask-taken", "node-build-image.ask-taken", "node-engine.running", "mesh-wants.step-ended", "mesh-catalog.registration-changed",
-			"mesh-catalog.catalog-revision", "mesh-conditions.findings-asked", "mesh-delivery.recovery-merged"})},
+			"mesh-catalog.catalog-revision", "mesh-conditions.findings-asked", "mesh-delivery.recovery-merged",
+			// A-186: the seat list its write verbs' callers are checked against, heard as it changes.
+			"mesh-catalog.seat-definition-changed", "mesh-catalog.seat-definition-removed"})},
 		// RN2 (§21, §195, §200, §77): the registrations and the catalog half asked by their verbs, the first views read and
 		// asked again by hand (a hand act).
-		{"invokes", equalSets(m.Invokes, []string{"seat:mesh-catalog.registrations", "seat:mesh-catalog.revision", "seat:mesh-hand-acts.hand-act",
+		{"invokes", equalSets(m.Invokes, []string{"seat:mesh-catalog.registrations",
+			// A-186: the seat list, read by its verb.
+			"seat:mesh-catalog.seat-definitions", "seat:mesh-catalog.revision", "seat:mesh-hand-acts.hand-act",
 			// RN3 (§53, §334): a publication's dependents behind.
 			"seat:mesh-catalog.outdated",
 			// RN10 (§71, §441, A-207): the permissions a change widens, asked of the grants part.
diff --git a/modules/mesh-delivery-pipeline/module.json b/modules/mesh-delivery-pipeline/module.json
index 37a6d125..665b4fd9 100644
--- a/modules/mesh-delivery-pipeline/module.json
+++ b/modules/mesh-delivery-pipeline/module.json
@@ -50,9 +50,12 @@
     "mesh-catalog.registration-changed",
     "mesh-catalog.catalog-revision",
     "mesh-conditions.findings-asked",
-    "mesh-delivery.recovery-merged"
+    "mesh-delivery.recovery-merged",
+    "mesh-catalog.seat-definition-changed",
+    "mesh-catalog.seat-definition-removed"
   ],
   "invokes": [
+    "seat:mesh-catalog.seat-definitions",
     "seat:mesh-catalog.registrations",
     "seat:mesh-catalog.revision",
     "seat:mesh-hand-acts.hand-act",