diff --git a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/integration_test.go b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/integration_test.go
index e2f4c15..502c82f 100644
--- a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/integration_test.go
+++ b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/integration_test.go
@@ -5,6 +5,7 @@ package main
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -20,6 +21,7 @@ import (
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/announce"
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 
 	"mesh-delivery-checker/internal/check"
@@ -75,7 +77,6 @@ func readCaptured(t *testing.T, name string) map[string]any {
 type fakeBuildModules struct {
 	js       jetstream.JetStream
 	ctx      context.Context
-	n        atomic.Int64
 	conflict atomic.Bool
 	mu       sync.Mutex
 	calls    map[string]int // by `<module>.<tool>`
@@ -112,45 +113,55 @@ func (f *fakeBuildModules) result(t *testing.T, tool string, args map[string]any
 	return data
 }
 
-func (f *fakeBuildModules) serve(t *testing.T, nc *nats.Conn, module string) {
-	steps, err := f.js.CreateKeyValue(f.ctx, jetstream.KeyValueConfig{Bucket: delivery.StepsBucket(module), History: 1})
+// serve makes module's steps bucket and its build seat's stream and workers, and pulls its asks on n1 as the real module
+// does since R4g (ADR 0525; issue 1887 A5): each ask's job runs with step bodies answering the captured results, and a
+// check takes the kept verdicts of the checker's kept bucket by their digests.
+func (f *fakeBuildModules) serve(t *testing.T, module string, kept jetstream.KeyValue) {
+	kv, err := f.js.CreateKeyValue(f.ctx, jetstream.KeyValueConfig{Bucket: delivery.StepsBucket(module), History: 1})
 	if err != nil {
 		t.Fatal(err)
 	}
-	sub, err := nc.Subscribe("mesh.mod."+module+".call.>", func(m *nats.Msg) {
-		tokens := strings.Split(m.Subject, ".") // mesh mod <module> call <tool> <node> <caller>
-		tool, node := tokens[4], tokens[5]
-		f.mu.Lock()
-		f.calls[module+"."+tool]++
-		f.mu.Unlock()
-		var args map[string]any
-		_ = json.Unmarshal(m.Data, &args)
-		id := fmt.Sprintf("s%d", f.n.Add(1))
-		key, _ := delivery.StepKey(node, id)
-		put := func(s delivery.Step) {
-			data, err := delivery.EncodeStep(s)
-			if err == nil {
-				_, err = steps.Put(f.ctx, key, data)
+	language := strings.TrimPrefix(module, "mesh-build-")
+	if err := buildstep.DeclareAskWorkers(f.ctx, f.js, language, 30*time.Second); err != nil {
+		t.Fatal(err)
+	}
+	prefix := map[string]string{"mesh-build-go": "build_go_", "mesh-build-node": "build_node_"}[module]
+	call := func(name string) buildstep.StepFunc {
+		return func(ctx context.Context, args map[string]any) (any, error) {
+			tool := prefix + name
+			f.mu.Lock()
+			f.calls[module+"."+tool]++
+			f.mu.Unlock()
+			return f.result(t, tool, args), nil
+		}
+	}
+	steps := buildstep.AskSteps{Fetch: call("fetch"), Test: call("test"),
+		Kept: func(ctx context.Context, level, digest string) (int, bool, error) {
+			key, err := delivery.KeptKey(level, digest)
+			if err != nil {
+				return 0, false, err
+			}
+			e, err := kept.Get(ctx, key)
+			if errors.Is(err, jetstream.ErrKeyNotFound) {
+				return 0, false, nil
 			}
 			if err != nil {
-				t.Errorf("writing step %s: %v", key, err)
+				return 0, false, err
 			}
-		}
-		step := delivery.Step{ID: id, Tool: tool, Node: node, State: delivery.StepRunning, Started: time.Now().UTC()}
-		put(step)
-		answer, _ := json.Marshal(map[string]any{"result": map[string]any{"step": id, "key": key, "state": "running"}, "error": "", "node": node})
-		_ = m.Respond(answer)
-		go func() {
-			time.Sleep(20 * time.Millisecond)
-			step.Ended = time.Now().UTC()
-			step.State, step.Result = delivery.StepPassed, f.result(t, tool, args)
-			put(step)
-		}()
-	})
-	if err != nil {
-		t.Fatal(err)
+			v, err := delivery.DecodeKept(e.Value())
+			return v.Tests, err == nil, err
+		}}
+	if module == "mesh-build-go" {
+		steps.Digest = call("digest")
 	}
-	t.Cleanup(func() { _ = sub.Unsubscribe() })
+	put := func(key string, value any) (uint64, error) {
+		raw, _ := value.(json.RawMessage)
+		return kv.Put(f.ctx, key, raw)
+	}
+	p := &buildstep.Puller{Source: &buildstep.JetStreamAsks{JS: f.js, Language: language}, Language: language, Node: "n1", Put: put,
+		Capacity: func() int { return 2 }, PullWait: 200 * time.Millisecond,
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { return buildstep.RunAsk(ctx, steps, a) }}
+	go func() { _ = p.Pull(f.ctx) }()
 }
 
 // serveForge answers the forge's two reads as its tools do, with the answers the forge gave (internal/check/testdata/captured):
@@ -283,8 +294,8 @@ func startBed(t *testing.T) *bed {
 	}
 	b.serveForge(t, ctl)
 	b.fake = &fakeBuildModules{js: js, ctx: ctx, calls: map[string]int{}}
-	b.fake.serve(t, ctl, "mesh-build-go")
-	b.fake.serve(t, ctl, "mesh-build-node")
+	b.fake.serve(t, "mesh-build-go", b.buckets[delivery.CheckerKeptBucket])
+	b.fake.serve(t, "mesh-build-node", b.buckets[delivery.CheckerKeptBucket])
 	b.report(t, "mesh-build-go", "n1", "go", "go1.27.1", "1")
 	b.report(t, "mesh-build-node", "n1", "typescript", "tsc5", "1")
 	b.setTrunk(t, map[string]string{repo: trunk})
diff --git a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/judge.go b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/judge.go
index 7db6c2b..8ea203b 100644
--- a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/judge.go
+++ b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/judge.go
@@ -15,11 +15,8 @@ import (
 
 // judgeDeps are the parts the judge of a check is made of.
 type judgeDeps struct {
-	runner   buildrun.Runner
+	asks     check.Asks
 	tools    *buildrun.ToolchainSet
-	presence *buildrun.PresenceSet
-	have     *buildrun.HaveSet
-	places   *buildrun.Places
 	trunks   *check.Trunks
 	kept     check.KV
 	previews check.KV
@@ -31,7 +28,7 @@ type judgeDeps struct {
 }
 
 func newJudge(d judgeDeps) check.Judge {
-	return &check.Examiner{Steps: d.runner, Toolchains: d.tools, Presence: d.presence, Health: d.have, Places: d.places,
+	return &check.Examiner{Asks: d.asks, Toolchains: d.tools,
 		Kept: check.Kept{Store: d.kept}, Previews: d.previews, Modules: d.repos, Packages: d.repos, Forge: d.forge, Runs: d.repos, Builds: d.builds, Announce: d.announce, Trunks: d.trunks, Logf: d.logf}
 }
 
diff --git a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/main.go b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/main.go
index 41377e8..fb98e28 100644
--- a/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/main.go
+++ b/modules/mesh-delivery-checker/cmd/mesh-delivery-checker/main.go
@@ -201,8 +201,10 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	presence := &buildrun.PresenceSet{}
 	have := &buildrun.HaveSet{}
 	trunks := &check.Trunks{}
-	places := &buildrun.Places{Capacity: capacity}
-	runner := buildrun.Runner{Caller: heardCaller{caller.CallOn}, Steps: stepsWaiter{js}, Bound: stepBound}
+	_ = capacity
+	// A check is one ask per pull request and build module on the build seats' check stream, pulled by a build node with a
+	// free slot (novox/hq ADR 0525 §1, §3): the checker chooses no node and starts no step.
+	asks := buildrun.JetStreamAsks{JS: js}
 	ch := &check.Checker{
 		Verdicts: kvStore{buckets[delivery.CheckerVerdictsBucket]},
 		Owed:     kvStore{buckets[delivery.CheckerOwedBucket]},
@@ -235,7 +237,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	}
 	repos := &repoModules{manifests: kvStore{buckets[delivery.ManifestsBucket]}, logf: logger.Printf}
 	ch.Judge = newJudge(judgeDeps{
-		runner: runner, tools: tools, presence: presence, have: have, places: places, trunks: trunks,
+		asks: buildrun.Asker{Publisher: asks, Waiter: asks, Bound: stepBound}, tools: tools, trunks: trunks,
 		kept: kvStore{buckets[delivery.CheckerKeptBucket]}, previews: kvStore{buckets[delivery.PreviewsBucket]},
 		repos: repos, builds: builds, forge: forgeReads{call: caller.Call}, logf: logger.Printf,
 		announce: announce,
diff --git a/modules/mesh-delivery-checker/internal/check/case.go b/modules/mesh-delivery-checker/internal/check/case.go
index 4240ed4..e7e8654 100644
--- a/modules/mesh-delivery-checker/internal/check/case.go
+++ b/modules/mesh-delivery-checker/internal/check/case.go
@@ -49,6 +49,9 @@ type Case struct {
 	Try *TryOptions
 	// Progress says what the check is doing, so a check that ran past its bound names the step it was stuck at.
 	Progress *Progress
+	// Kind is what asked the check (KindNew, KindNodes, KindTrunk): a re-judge after a trunk move is asked on the build
+	// seats' recheck stream, every other check on check (ADR 0536 §4).
+	Kind string
 }
 
 // Progress is the step a check is at, written by the check and read when its bound passes.
diff --git a/modules/mesh-delivery-checker/internal/check/checker.go b/modules/mesh-delivery-checker/internal/check/checker.go
index 33f795e..850b7fe 100644
--- a/modules/mesh-delivery-checker/internal/check/checker.go
+++ b/modules/mesh-delivery-checker/internal/check/checker.go
@@ -207,7 +207,8 @@ func (ch *Checker) consider(ctx context.Context, key string, c delivery.Candidat
 	go func() {
 		defer ch.wg.Done()
 		for {
-			ch.admit(cs, ch.kindOf(ctx, cs))
+			cs.Kind = ch.kindOf(ctx, cs) // a re-judge after a trunk move is asked on the recheck stream (ADR 0536 §4)
+			ch.admit(cs, cs.Kind)
 			ch.try(ctx, key, cs)
 			ch.leave()
 			ch.mu.Lock()
diff --git a/modules/mesh-delivery-checker/internal/check/examiner_test.go b/modules/mesh-delivery-checker/internal/check/examiner_test.go
index 88ce8fb..b90ae93 100644
--- a/modules/mesh-delivery-checker/internal/check/examiner_test.go
+++ b/modules/mesh-delivery-checker/internal/check/examiner_test.go
@@ -15,6 +15,7 @@ import (
 	"testing"
 	"time"
 
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 )
@@ -108,6 +109,7 @@ const digD = "dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44dd44"
 
 type bench struct {
 	ex     *Examiner
+	asks   *buildrun.FakeAsks
 	steps  *fakeSteps
 	kept   *memKV
 	prev   *memKV
@@ -116,6 +118,50 @@ type bench struct {
 	test   func(c stepCall) (any, error)
 }
 
+// refsOf reads the siblings of a fetch's arguments, as they arrive in an ask (JSON) or as the checker gave them.
+func refsOf(v any) []BesideRef {
+	raw, _ := json.Marshal(v)
+	var refs []BesideRef
+	_ = json.Unmarshal(raw, &refs)
+	return refs
+}
+
+// toolPrefix is the start of each build module's tool names, as the fake build modules answer them.
+var toolPrefix = map[string]string{buildrun.GoBuildModule: "build_go_", buildrun.NodeBuildModule: "build_node_"}
+
+// answer runs a check ask as the build module that pulls it does (buildstep.RunAsk), with the fake tools on shanks and the
+// bench's kept verdicts, and answers the step it writes.
+func (b *bench) answer(a delivery.StepAsk) delivery.Step {
+	module, _ := delivery.BuildModuleOf(a.Language)
+	const node = "shanks"
+	tool := func(name string) buildstep.StepFunc {
+		return func(ctx context.Context, args map[string]any) (any, error) {
+			raw, err := b.steps.Run(ctx, module, node, toolPrefix[module]+name, args)
+			if err != nil {
+				return nil, err
+			}
+			return raw, nil
+		}
+	}
+	steps := buildstep.AskSteps{Fetch: tool("fetch"), Test: tool("test"),
+		Kept: func(ctx context.Context, level, digest string) (int, bool, error) {
+			k, found, err := (Kept{Store: b.kept}).Lookup(ctx, level, digest)
+			return k.Tests, found, err
+		}}
+	if module == buildrun.GoBuildModule {
+		steps.Digest = tool("digest")
+	}
+	out, err := buildstep.RunAsk(context.Background(), steps, a)
+	began := time.Date(2026, 10, 21, 19, 0, 0, 0, time.UTC)
+	step := delivery.Step{ID: a.ID, Tool: a.Kind + " ask", Node: node, State: delivery.StepPassed, Started: began, Ended: began.Add(2 * time.Second)}
+	if err != nil {
+		step.State, step.Reason = delivery.StepFailed, err.Error()
+		return step
+	}
+	step.Result, _ = json.Marshal(out)
+	return step
+}
+
 // newBench is an examiner over fake build modules that merge cleanly, digest the captured fixture's packages and pass
 // the captured slow fixture's result at both levels, on shanks.
 func newBench(t testing.TB) *bench {
@@ -142,7 +188,8 @@ func newBench(t testing.TB) *bench {
 		"build_node_test":  func(c stepCall) (any, error) { return b.test(c) },
 	}
 	now := time.Date(2026, 10, 21, 19, 0, 0, 0, time.UTC)
-	b.ex = &Examiner{Steps: b.steps, Toolchains: goEntries("shanks"), Places: &buildrun.Places{}, Kept: Kept{Store: b.kept}, Previews: b.prev,
+	b.asks = &buildrun.FakeAsks{Answer: b.answer}
+	b.ex = &Examiner{Asks: buildrun.Asker{Publisher: b.asks, Waiter: b.asks, Bound: 5 * time.Second}, Toolchains: goEntries("shanks"), Kept: Kept{Store: b.kept}, Previews: b.prev,
 		Modules: langs{}, Trunks: &Trunks{}, Now: func() time.Time { now = now.Add(50 * time.Millisecond); return now }}
 	return b
 }
@@ -353,33 +400,6 @@ func TestAHeadThatDoesNotMergeEndsFailedNamingTheFilesAndRunsNoTest(t *testing.T
 	}
 }
 
-func TestNoQualifyingNodeIsAFailureOfTheNodes(t *testing.T) { // N6/AC4
-	b := newBench(t)
-	b.ex.Toolchains = entries{}
-	out := b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
-	if !IsNodesFailure(out.Verdict) {
-		t.Fatalf("verdict = %+v, want a failure of the nodes", out.Verdict)
-	}
-	b.ex.Toolchains = goEntries("shanks")
-	b.ex.Presence = offline{}
-	if out = b.judge(t, caseOf(t, pullOf(repoA, 7, head1))); !IsNodesFailure(out.Verdict) {
-		t.Fatalf("an offline node: verdict = %+v", out.Verdict)
-	}
-}
-
-type offline struct{}
-
-func (offline) Online(string) bool { return false }
-
-func TestAStepThatFailsIsAVerdictNamingTheNode(t *testing.T) {
-	b := newBench(t)
-	b.steps.handlers["build_go_fetch"] = func(stepCall) (any, error) { return nil, fmt.Errorf("the step failed: ssh refused") }
-	out := b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
-	if f := out.Verdict.Failed; out.Verdict.State != delivery.VerdictFail || f.Machine != "shanks" || !strings.Contains(f.Words, "ssh refused") {
-		t.Fatalf("verdict = %+v", out.Verdict)
-	}
-}
-
 func TestALevelWhoseDigestIsNotNamedRunsWholeAndKeepsNothing(t *testing.T) { // 1287/AC4
 	b := newBench(t)
 	b.steps.handlers["build_go_digest"] = func(stepCall) (any, error) { return nil, fmt.Errorf("go list failed") }
@@ -441,7 +461,7 @@ func TestAGroupIsOneVerdictAndEachMembersTestsReadTheOthersAtTheirHeads(t *testi
 	var forA []BesideRef
 	for _, f := range fetch {
 		if f.args["repository"] == repoA {
-			forA, _ = f.args["beside"].([]BesideRef)
+			forA, _ = refsOf(f.args["beside"]), true
 		}
 	}
 	found := false
@@ -599,7 +619,7 @@ func TestNothingIsKeptForAWorkspaceGivenSiblingsWhenTheDigestDoesNotSayItCoversT
 func echoBeside(b *bench, d Digested) Digested {
 	var lines []string
 	for _, f := range b.steps.tool("fetch") {
-		refs, _ := f.args["beside"].([]BesideRef)
+		refs, _ := refsOf(f.args["beside"]), true
 		for _, r := range refs {
 			lines = append(lines, r.Repository+" "+r.Commit)
 		}
@@ -614,7 +634,7 @@ func besideDigest(b *bench) func(c stepCall) (any, error) {
 		level := c.args["level"].(string)
 		var lines []string
 		for _, f := range b.steps.tool("fetch") {
-			refs, _ := f.args["beside"].([]BesideRef)
+			refs, _ := refsOf(f.args["beside"]), true
 			for _, r := range refs {
 				lines = append(lines, r.Repository+" "+r.Commit)
 			}
@@ -741,40 +761,37 @@ func TestNoStepOfACheckCarriesPublish(t *testing.T) { // ADR 0500 §4, 1309 (the
 	}
 }
 
-// keyCaller is a build module that starts every long step and answers its key on the node it was asked on.
-type keyCaller struct{}
-
-func (keyCaller) CallOn(node, key string, _ any) (json.RawMessage, error) {
-	return json.Marshal(map[string]string{"step": "lost1", "key": node + ".lost1", "state": delivery.StepRunning})
-}
-
-// lostSteps is a steps state whose key never ends: the build module stopped, restarted or was unassigned with the step
-// running, and nothing writes its end.
-type lostSteps struct{}
-
-func (lostSteps) Wait(ctx context.Context, _, _ string) (delivery.Step, error) {
-	<-ctx.Done()
-	return delivery.Step{}, ctx.Err()
-}
-
-func TestAStepThatNeverEndsEndsTheCheckLoudlyAndFreesItsNodesPlace(t *testing.T) { // 1890/AC1
+// 1890/AC1, 1887/A5a: an ask whose step never ends (the build node stopped with it running, and nothing redelivered it in
+// time) ends the check loudly at the asker's bound; the checker holds no place to free.
+func TestAnAskWhoseStepNeverEndsEndsTheCheckLoudly(t *testing.T) {
 	b := newBench(t)
-	places := &buildrun.Places{Capacity: map[string]int{"shanks": 1}}
-	b.ex.Places = places
-	b.ex.Steps = buildrun.Runner{Caller: keyCaller{}, Steps: lostSteps{}, Bound: 20 * time.Millisecond}
+	b.asks.Answer = nil
+	b.ex.Asks = buildrun.Asker{Publisher: b.asks, Waiter: b.asks, Bound: 20 * time.Millisecond}
 	out := b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
-	if f := out.Verdict.Failed; out.Verdict.State != delivery.VerdictFail || f.Machine != "shanks" || !strings.Contains(f.Words, "shanks.lost1 did not end within") {
+	if f := out.Verdict.Failed; out.Verdict.State != delivery.VerdictFail || !strings.Contains(f.Words, "did not end within") {
 		t.Fatalf("verdict = %+v", out.Verdict)
 	}
-	if r, res := places.Running(), places.Reserved(); len(r) != 0 || len(res) != 0 {
-		t.Fatalf("the lost step still holds shanks: running %v, reserved %v", r, res)
+	if n := len(b.asks.Asks()); n != 1 || b.asks.Asks()[0].Kind != delivery.AskCheck || b.asks.Asks()[0].Check == nil {
+		t.Fatalf("asks = %+v, want one check ask", b.asks.Asks())
+	}
+}
+
+// 1887/A5a, ADR 0536 §4: a check is one ask per pull request and build module on the check stream, a re-judge after a
+// trunk move one on the recheck stream, each carrying both levels with the kept verdicts taken by the build module.
+func TestACheckIsOneAskAndAReJudgeGoesOnTheRecheckStream(t *testing.T) {
+	b := newBench(t)
+	b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
+	asks := b.asks.Asks()
+	if len(asks) != 1 || asks[0].Kind != delivery.AskCheck || asks[0].Language != delivery.AskGo || asks[0].Asker != delivery.CheckerModule {
+		t.Fatalf("asks = %+v, want one Go check ask", asks)
+	}
+	if j := asks[0].Check; j == nil || !j.Kept || strings.Join(j.Levels, ",") != "unit,integration" || j.Fetch["repository"] != repoA {
+		t.Fatalf("the job = %+v", asks[0].Check)
+	}
+	cs := caseOf(t, pullOf(repoA, 7, head1))
+	cs.Kind = KindTrunk
+	b.judge(t, cs)
+	if asks := b.asks.Asks(); len(asks) != 2 || asks[1].Kind != delivery.AskRecheck {
+		t.Fatalf("asks = %+v, want the re-judge on recheck", asks)
 	}
-	// The node's one place is free: the next check takes it at once.
-	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
-	defer cancel()
-	release, err := places.Acquire(ctx, "shanks")
-	if err != nil {
-		t.Fatalf("shanks's place was not freed: %v", err)
-	}
-	release()
 }
diff --git a/modules/mesh-delivery-checker/internal/check/heard.go b/modules/mesh-delivery-checker/internal/check/heard.go
index d97c17f..b10bd09 100644
--- a/modules/mesh-delivery-checker/internal/check/heard.go
+++ b/modules/mesh-delivery-checker/internal/check/heard.go
@@ -1,18 +1,14 @@
 package check
 
 import (
-	"context"
-	"encoding/json"
 	"errors"
-	"fmt"
-	"strings"
 
 	"github.com/nats-io/nats.go"
 )
 
 // Unheard is the error of a call that reached nobody: the bus had no responder for it, or none answered within the call's
-// bound. The step it asked for never began, so the same step may be asked of another node (issue 1820). The program wraps
-// the errors of its calls in it where the bus gives a timeout; a no-responders error is known as it is.
+// bound. The program wraps the errors of its forge calls in it where the bus gives a timeout; a no-responders error is
+// known as it is. A build step is no call since R4g: an ask whose node stops is delivered again by its stream (ADR 0525 §6).
 type Unheard struct{ Err error }
 
 func (u *Unheard) Error() string { return u.Err.Error() }
@@ -23,79 +19,3 @@ func isUnheard(err error) bool {
 	var u *Unheard
 	return errors.As(err, &u) || errors.Is(err, nats.ErrNoResponders)
 }
-
-// deafNode is a node that did not answer a build module's call during this judging.
-type deafNode struct{ node, why string }
-
-// markDeaf takes a node out of the choice for a build module for the rest of the judging.
-func (st *state) markDeaf(bm, node string, err error) {
-	if st.deaf == nil {
-		st.deaf = map[string][]deafNode{}
-	}
-	st.deaf[bm] = append(st.deaf[bm], deafNode{node, err.Error()})
-}
-
-func (st *state) isDeaf(bm, node string) bool {
-	for _, d := range st.deaf[bm] {
-		if d.node == node {
-			return true
-		}
-	}
-	return false
-}
-
-// triedWords names every node that did not answer a build module, with what the bus said.
-func (st *state) triedWords(bm string) string {
-	var parts []string
-	for _, d := range st.deaf[bm] {
-		parts = append(parts, fmt.Sprintf("%s (%s)", d.node, d.why))
-	}
-	return strings.Join(parts, "; ")
-}
-
-// moveStep is called when the target's node did not answer: the node is left out of the choice, and another build node of the
-// same build module takes the target's place. It answers an error naming every node tried when none is left (the words hold
-// NodesWords, so the verdict is judged again when the nodes change).
-func (st *state) moveStep(t *target, err error) error {
-	old := t.node
-	st.markDeaf(t.module, old, err)
-	node, _, cerr := st.choose(t.module)
-	if cerr != nil {
-		return fmt.Errorf("%s; tried: %s", cerr, st.triedWords(t.module))
-	}
-	st.j.logf("%s#%d: %s did not answer (%v), the step goes to %s", t.pull.Repository, t.pull.Number, old, err, node)
-	t.node = node
-	other := false
-	for _, o := range st.targets {
-		if o != t && o.node == old {
-			other = true
-		}
-	}
-	if !other {
-		delete(st.nodes, old)
-	}
-	st.nodes[node] = true
-	return nil
-}
-
-// refetch makes the target's workspace again on its new node: the workspace of a step that was lost is on the node that did
-// not answer.
-func (st *state) refetch(ctx context.Context, t *target) error {
-	raw, err := st.step(ctx, t, "fetch", fmt.Sprintf("fetch %s#%d on %s", t.pull.Repository, t.pull.Number, t.node), t.fetchArgs)
-	if err != nil {
-		return err
-	}
-	var f Fetched
-	if err := json.Unmarshal(raw, &f); err != nil || f.Workspace == "" {
-		return fmt.Errorf("the fetch of %s#%d on %s answered no workspace: %s", t.pull.Repository, t.pull.Number, t.node, raw)
-	}
-	t.fetched = f
-	return nil
-}
-
-// stepOnWorkspace sets the workspace a step reads to the target's current one.
-func stepOnWorkspace(t *target, args map[string]any) {
-	if _, ok := args["workspace"]; ok {
-		args["workspace"] = t.fetched.Workspace
-	}
-}
diff --git a/modules/mesh-delivery-checker/internal/check/heard_test.go b/modules/mesh-delivery-checker/internal/check/heard_test.go
index 784ffc7..3072d8c 100644
--- a/modules/mesh-delivery-checker/internal/check/heard_test.go
+++ b/modules/mesh-delivery-checker/internal/check/heard_test.go
@@ -1,9 +1,7 @@
 package check
 
 import (
-	"context"
 	"fmt"
-	"strings"
 	"testing"
 
 	"github.com/nats-io/nats.go"
@@ -11,127 +9,8 @@ import (
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
-// Issue 1820: a build step goes to a node whose build module is not heard (a laptop asleep, not yet marked offline by the
-// watchman), and the bus answers "no responders". The check moves the step to another node of the same build module.
-
-// deafNodes makes every tool on the named nodes fail as the bus does when nobody listens there; count says how many
-// times the node was called.
-func deafNodes(b *bench, deaf ...string) {
-	for tool, h := range b.steps.handlers {
-		h := h
-		b.steps.handlers[tool] = func(c stepCall) (any, error) {
-			for _, n := range deaf {
-				if c.node == n {
-					return nil, fmt.Errorf("%s on %s: %w", c.tool, c.node, nats.ErrNoResponders)
-				}
-			}
-			return h(c)
-		}
-	}
-}
-
-func nodesOf(calls []stepCall) []string {
-	var out []string
-	for _, c := range calls {
-		out = append(out, c.node)
-	}
-	return out
-}
-
-func TestAFetchThatNobodyAnswersMovesToAnotherBuildNode(t *testing.T) { // 1820/AC1
-	b := newBench(t)
-	b.ex.Toolchains = goEntries("ace", "g14")
-	deafNodes(b, "ace")
-	v := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
-	if v.State != delivery.VerdictPass {
-		t.Fatalf("verdict = %+v, want a pass on the node that answers", v)
-	}
-	if got := nodesOf(b.steps.tool("fetch")); len(got) != 2 || got[0] != "ace" || got[1] != "g14" {
-		t.Errorf("fetch went to %v, want ace (no responders) then g14", got)
-	}
-	for _, c := range b.steps.tool("test") {
-		if c.node != "g14" {
-			t.Errorf("a test went to %s, want g14 only", c.node)
-		}
-	}
-	if len(v.Machines) != 1 || v.Machines[0] != "g14" {
-		t.Errorf("machines = %v, want [g14]: ace ran nothing", v.Machines)
-	}
-}
-
-func TestATestStepThatNobodyAnswersIsFetchedAgainOnAnotherNode(t *testing.T) { // 1820/AC2
-	b := newBench(t)
-	b.ex.Toolchains = goEntries("ace", "g14")
-	// ace answers the fetch and the digest, then goes to sleep before the test.
-	test := b.steps.handlers["build_go_test"]
-	b.steps.handlers["build_go_test"] = func(c stepCall) (any, error) {
-		if c.node == "ace" {
-			return nil, fmt.Errorf("test on ace: %w", nats.ErrNoResponders)
-		}
-		return test(c)
-	}
-	v := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
-	if v.State != delivery.VerdictPass {
-		t.Fatalf("verdict = %+v, want a pass", v)
-	}
-	if got := nodesOf(b.steps.tool("fetch")); len(got) != 2 || got[1] != "g14" {
-		t.Errorf("fetch went to %v, want ace then g14 (the workspace was on ace)", got)
-	}
-	for _, c := range b.steps.tool("test") {
-		if c.node == "g14" && c.args["workspace"] == nil {
-			t.Errorf("a test on g14 has no workspace")
-		}
-	}
-	if len(v.Machines) != 1 || v.Machines[0] != "g14" {
-		t.Errorf("machines = %v, want [g14]", v.Machines)
-	}
-}
-
-func TestWhenNoBuildNodeAnswersTheFailureNamesEveryNodeTried(t *testing.T) { // 1820/AC3
-	b := newBench(t)
-	b.ex.Toolchains = goEntries("ace", "g14", "shanks")
-	deafNodes(b, "ace", "g14", "shanks")
-	v := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
-	if v.State != delivery.VerdictFail {
-		t.Fatalf("verdict = %+v, want a failure", v)
-	}
-	for _, n := range []string{"ace", "g14", "shanks"} {
-		if !strings.Contains(v.Failed.Words, n) {
-			t.Errorf("failure %q does not name %s", v.Failed.Words, n)
-		}
-	}
-	if !IsNodesFailure(v) {
-		t.Errorf("failure %q is not a failure of the nodes, so it would not be judged again when they change", v.Failed.Words)
-	}
-	if got := len(b.steps.tool("fetch")); got != 3 {
-		t.Errorf("fetch was tried %d times, want once on each of 3 nodes", got)
-	}
-}
-
-func TestAStepThatFailedForTheChangeIsNotMovedToAnotherNode(t *testing.T) { // 1820/AC4
-	b := newBench(t)
-	b.ex.Toolchains = goEntries("ace", "g14")
-	b.steps.handlers["build_go_fetch"] = func(stepCall) (any, error) { return nil, fmt.Errorf("fetch on ace: the step failed: git exploded") }
-	v := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
-	if v.State != delivery.VerdictFail || len(b.steps.tool("fetch")) != 1 {
-		t.Errorf("verdict = %+v after %d fetches, want a failure after one", v, len(b.steps.tool("fetch")))
-	}
-}
-
-func TestACanceledCheckIsNotMovedToAnotherNode(t *testing.T) { // 1820/AC4
-	b := newBench(t)
-	b.ex.Toolchains = goEntries("ace", "g14")
-	ctx, cancel := context.WithCancel(context.Background())
-	b.steps.handlers["build_go_fetch"] = func(stepCall) (any, error) {
-		cancel()
-		return nil, fmt.Errorf("fetch on ace: %w", nats.ErrNoResponders)
-	}
-	_, _ = b.ex.Judge(ctx, caseOf(t, pullOf(repoA, 7, head1)))
-	if n := len(b.steps.tool("fetch")); n != 1 {
-		t.Errorf("fetch was tried %d times after the check ended, want 1", n)
-	}
-}
-
+// Issue 1820 AC5: a read of the forge that nobody answers is the forge's failure, not a build node's. (AC1-AC4 moved a
+// step to another node; since R4g an ask whose node stops is delivered again by its stream: ADR 0525 §6.)
 func TestAPinReadThatNobodyAnswersIsTheForgesFailureNotABuildNodes(t *testing.T) { // 1820/AC5
 	b := groupBench(t, "cb54756c3865")
 	b.ex.Forge.(*fakeForge).err = fmt.Errorf("gitea.gitea_get_file: %w", nats.ErrNoResponders)
diff --git a/modules/mesh-delivery-checker/internal/check/judge.go b/modules/mesh-delivery-checker/internal/check/judge.go
index dcd07f0..9351d50 100644
--- a/modules/mesh-delivery-checker/internal/check/judge.go
+++ b/modules/mesh-delivery-checker/internal/check/judge.go
@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 )
@@ -51,9 +52,11 @@ type verdictPtr = *delivery.Verdict
 
 func failed(machine, words string) verdictPtr { return fail(machine, words) }
 
-// Steps runs a build module's long step on a node and answers its result (buildrun.Runner).
-type Steps interface {
-	Run(ctx context.Context, module, node, tool string, args map[string]any) (json.RawMessage, error)
+// Asks puts a check's ask on its build seat's stream and waits for its step (buildrun.Asker; ADR 0525 §1, §6): the
+// checker chooses no node, starts no step and holds none; whichever build node pulls the ask runs the check.
+type Asks interface {
+	Put(ctx context.Context, a delivery.StepAsk) error
+	Wait(ctx context.Context, a delivery.StepAsk) (delivery.Step, error)
 }
 
 // ToolchainEntries are the nodes' toolchain entries of a language (buildrun.ToolchainSet).
@@ -67,24 +70,18 @@ type BuildModules interface {
 	BuildModules(repository string) []string
 }
 
-// toolPrefix is the start of each build module's tool names.
-var toolPrefix = map[string]string{buildrun.GoBuildModule: "build_go_", buildrun.NodeBuildModule: "build_node_"}
+// askLanguage is the build seat language of each build module the checker asks.
+var askLanguage = map[string]string{buildrun.GoBuildModule: delivery.AskGo, buildrun.NodeBuildModule: delivery.AskNode}
 
-// Examiner judges a case through the build modules (ADR 0484 clauses 3, 4, 10, 13): for each pull request it fetches the head
-// merged onto its trunk head on a build node, then runs the unit level and the integration level, taking the kept verdicts
-// of unchanged packages, running the change's own tests first and stopping at the first failure.
+// Examiner judges a case through the build seats (ADR 0484 clauses 3, 4, 10, 13; ADR 0525 §1, §3): for each pull request
+// and build module it puts one check ask whose job fetches the head merged onto its trunk head, then runs the unit level
+// and the integration level, taking the kept verdicts of unchanged packages, running the change's own tests first and
+// stopping at the first failure; it judges the step's answer as it judged the tools' answers.
 type Examiner struct {
-	Steps      Steps
+	Asks Asks
+	// Toolchains are the nodes' toolchains: a kept verdict names the toolchain the nodes agree on.
 	Toolchains ToolchainEntries
-	// Presence says which nodes are online; Health whether a node's build module is running and healthy. A node that is not
-	// is not chosen; nil means every node is.
-	Presence interface{ Online(node string) bool }
-	Health   interface {
-		Healthy(node, module string) bool
-	}
-	// Places holds a step back while its node is at the checker's capacity (ADR 0484 clause 12).
-	Places *buildrun.Places
-	Kept   Kept
+	Kept       Kept
 	// Previews is the previews bucket; nil writes none.
 	Previews KV
 	Modules  BuildModules
@@ -132,22 +129,22 @@ func besideLines(refs []BesideRef) []string {
 	return out
 }
 
-// target is a pull request on one build module: the node chosen, the workspace its fetch made and what it said.
+// target is a pull request on one build module: the node that pulled its ask, the workspace its fetch made and what it
+// said.
 type target struct {
 	pull      Pull
 	module    string
 	node      string
 	toolchain string
 	fetched   Fetched
-	// fetchArgs are the arguments of the target's fetch, so a workspace lost with its node is made again on another.
+	// fetchArgs are the arguments of the fetch its check ask runs.
 	fetchArgs map[string]any
 	// priority are the Go packages (import paths) or the Node module directories whose test files the merge changes.
 	changed []string
 	// beside are the lines `<owner/repo> <commit>` of the siblings the workspace was given, sorted: its tests may read them,
 	// so a verdict is kept or taken only under a digest that says it folded exactly these in (lead decision L5).
 	beside []string
-	plans  map[string]*goPlan // by level
-	// runner is RunnerWorkspace while the target's steps are asked to run the candidate (ADR 0535 §1), empty otherwise.
+	// runner is RunnerWorkspace when the target's ask runs the candidate's own build module (ADR 0535 §1), empty otherwise.
 	runner string
 	// judged is what the line says of the program that judged a change to the build module; empty for any other change.
 	judged string
@@ -177,14 +174,6 @@ func (t *target) stepArgs(args map[string]any) map[string]any {
 	return args
 }
 
-// goPlan is what a Go target has to run at one level: the digests, the packages without a kept verdict and the tests taken.
-type goPlan struct {
-	digests map[string]string
-	todo    []string
-	// all says the digest step gave nothing to key a kept verdict by, so the level runs whole and keeps nothing.
-	all bool
-}
-
 // acc collects a level's counts across targets.
 type acc struct {
 	run, kept, skipped int
@@ -200,7 +189,6 @@ type state struct {
 	targets []*target
 	levels  map[string]*acc
 	nodes   map[string]bool
-	deaf    map[string][]deafNode // by build module: the nodes that did not answer during this judging
 	clone   time.Duration
 	slow    []string
 }
@@ -209,24 +197,9 @@ type state struct {
 // be judged at all.
 func (j *Examiner) Judge(ctx context.Context, c *Case) (Outcome, error) {
 	st := &state{j: j, c: c, levels: map[string]*acc{delivery.LevelUnit: {}, delivery.LevelIntegration: {}}, nodes: map[string]bool{}}
-	if v := st.fetchAll(ctx); v != nil {
+	if v := st.judgeAll(ctx); v != nil {
 		return st.finish(ctx, *v), nil
 	}
-	if v := st.checkPins(ctx); v != nil {
-		return st.finish(ctx, *v), nil
-	}
-	for _, level := range []string{delivery.LevelUnit, delivery.LevelIntegration} {
-		if c.Try != nil && c.Try.Level != "" && c.Try.Level != level {
-			continue // a try of one level runs that level alone
-		}
-		for _, priority := range []bool{true, false} {
-			for _, t := range st.targets {
-				if v := st.runTarget(ctx, t, level, priority); v != nil {
-					return st.finish(ctx, *v), nil
-				}
-			}
-		}
-	}
 	return st.finish(ctx, delivery.Verdict{State: delivery.VerdictPass}), nil
 }
 
@@ -291,55 +264,18 @@ func fail(machine, words string) *delivery.Verdict {
 	return &v
 }
 
-// step runs one step of a build module on the node the target is on, holding a place there while it runs. A node that does
-// not answer (the bus has no responder, or none answered) is left out and the step goes to another node of the same build
-// module; a step after the fetch makes its workspace again there first (issue 1820).
-func (st *state) step(ctx context.Context, t *target, tool, label string, args map[string]any) (json.RawMessage, error) {
-	for {
-		raw, err := st.stepOnce(ctx, t, tool, label, args)
-		if err == nil || ctx.Err() != nil || !isUnheard(err) {
-			return raw, err
-		}
-		if merr := st.moveStep(t, err); merr != nil {
-			return nil, merr
-		}
-		if tool != "fetch" {
-			if rerr := st.refetch(ctx, t); rerr != nil {
-				return nil, rerr
-			}
-			stepOnWorkspace(t, args)
-		}
+// levels are the levels a case's asks run: both, or the one a try names.
+func (st *state) levelsOf() []string {
+	if st.c.Try != nil && st.c.Try.Level != "" {
+		return []string{st.c.Try.Level} // a try of one level runs that level alone
 	}
+	return []string{delivery.LevelUnit, delivery.LevelIntegration}
 }
 
-func (st *state) stepOnce(ctx context.Context, t *target, tool, label string, args map[string]any) (json.RawMessage, error) {
-	st.c.Progress.Set(label, t.node)
-	release, err := st.j.Places.Acquire(ctx, t.node)
-	if err != nil {
-		return nil, err
-	}
-	defer release()
-	return st.j.Steps.Run(ctx, t.module, t.node, toolPrefix[t.module]+tool, args)
-}
-
-// choose picks the build node for a pull request's repository on a build module.
-func (st *state) choose(bm string) (node, toolchain string, err error) {
-	language := buildrun.LanguageOf[bm]
-	qualifies := func(node string) bool {
-		return !st.isDeaf(bm, node) && (st.j.Presence == nil || st.j.Presence.Online(node)) && (st.j.Health == nil || st.j.Health.Healthy(node, bm))
-	}
-	nodes, tc, err := buildrun.ChooseNodes(language, st.j.Toolchains.Entries(language), st.j.Places, qualifies, 1)
-	if err != nil {
-		return "", "", err
-	}
-	return nodes[0], tc.Version, nil
-}
-
-// fetchAll fetches every pull request's head merged onto its trunk on a build node of each build module the repository
-// needs. A head that does not merge, or a step that fails, ends the check at once, running no test (ADR 0484 clause 13).
-func (st *state) fetchAll(ctx context.Context) *delivery.Verdict {
-	began := st.j.now()
-	defer func() { st.clone = st.j.now().Sub(began) }()
+// judgeAll puts one check ask per pull request and build module the repository needs, the mesh-sdk member first, and
+// judges each answer. A head that does not merge, a pin that is not allowed or a level that fails ends the check at once
+// (ADR 0484 clause 13).
+func (st *state) judgeAll(ctx context.Context) *delivery.Verdict {
 	// The mesh-sdk member first: whether its merge changes the TypeScript package's paths decides whether the other members'
 	// Node fetches take the group's package (ADR 0500 §5).
 	pulls := slices.Clone(st.c.Pulls)
@@ -356,47 +292,32 @@ func (st *state) fetchAll(ctx context.Context) *delivery.Verdict {
 	for _, p := range pulls {
 		var merged []Fetched
 		for _, bm := range st.j.Modules.BuildModules(p.Repository) {
-			node, tc, err := st.choose(bm)
-			if err != nil {
-				return fail(bm, err.Error())
+			t := &target{pull: p, module: bm}
+			if tc, none := delivery.AgreedToolchain(st.j.Toolchains.Entries(buildrun.LanguageOf[bm])); none == "" {
+				t.toolchain = tc.Version
 			}
-			t := &target{pull: p, module: bm, node: node, toolchain: tc, plans: map[string]*goPlan{}}
-			st.nodes[node] = true
 			args := map[string]any{"repository": p.Repository, "commit": p.Head, "ref": refOf(p.Number), "base": p.Trunk}
-			t.fetchArgs = args
 			if bm == buildrun.NodeBuildModule && groupPackage != nil && p.Repository != SDKRepository {
 				args["package"] = groupPackage
 			}
 			if bm == buildrun.GoBuildModule {
 				beside, err := st.j.besideFor(ctx, st.c, p)
 				if err != nil {
-					return fail(forgeMachine(err, node), err.Error()+unheardWords(err))
+					return fail(forgeMachine(err, bm), err.Error()+unheardWords(err))
 				}
 				if len(beside) > 0 {
 					args["beside"] = beside
 					t.beside = besideLines(beside)
 				}
-			}
-			raw, err := st.step(ctx, t, "fetch", fmt.Sprintf("fetch %s#%d on %s", p.Repository, p.Number, node), args)
-			node = t.node // the step may have moved to another node
-			if err != nil {
-				return fail(node, fmt.Sprintf("fetch of %s#%d: %v%s", p.Repository, p.Number, err, pinHint(st.c, err.Error())))
-			}
-			if err := json.Unmarshal(raw, &t.fetched); err != nil || t.fetched.Workspace == "" {
-				return fail(node, fmt.Sprintf("the fetch of %s#%d answered no workspace: %s", p.Repository, p.Number, raw))
-			}
-			if len(t.fetched.Conflicts) > 0 {
-				if st.c.Try == nil {
-					st.j.writePreview(ctx, p, append(merged, t.fetched))
+				if p.Repository == catalogueRepository {
+					t.runner = RunnerWorkspace // used by the build module when the merge changes it (ADR 0535 §1)
 				}
-				return fail(node, fmt.Sprintf("%s#%d does not merge into the trunk: files in conflict: %s", p.Repository, p.Number, strings.Join(t.fetched.Conflicts, ", ")))
 			}
-			t.changed = t.fetched.Changed
-			if bm == buildrun.GoBuildModule && changesBuildGo(p.Repository, t.changed) {
-				t.runner = RunnerWorkspace
-			}
-			merged = append(merged, t.fetched)
+			t.fetchArgs = args
 			st.targets = append(st.targets, t)
+			if v := st.ask(ctx, t, &merged); v != nil {
+				return v
+			}
 		}
 		if st.c.Try == nil { // a try owes the indexer no preview: no pull request holds its head
 			st.j.writePreview(ctx, p, merged)
@@ -408,6 +329,138 @@ func (st *state) fetchAll(ctx context.Context) *delivery.Verdict {
 	return nil
 }
 
+// ask puts the target's check ask, waits for the step of the node that pulled it and judges its answer: the fetch, the
+// pins of its go.mod files, then each level's digest, kept verdicts and tests.
+func (st *state) ask(ctx context.Context, t *target, merged *[]Fetched) *delivery.Verdict {
+	p := t.pull
+	job := &delivery.CheckJob{Fetch: t.fetchArgs, Levels: st.levelsOf(), Kept: true}
+	if t.runner != "" {
+		job.Runner, job.RunnerWhen = t.runner, buildGoDir
+	}
+	if st.c.Try != nil && st.c.Try.Run != "" {
+		job.Run, job.Kept = st.c.Try.Run, false // a try of some tests runs them alone: a partial run proves no package
+	}
+	kind := delivery.AskCheck
+	if st.c.Kind == KindTrunk {
+		kind = delivery.AskRecheck // a re-judge after a trunk move goes after every new head's check (ADR 0536 §4)
+	}
+	a := delivery.StepAsk{ID: buildstep.NewID(), Kind: kind, Language: askLanguage[t.module], Asker: delivery.CheckerModule,
+		At: st.j.now().UTC(), Check: job}
+	st.c.Progress.Set(fmt.Sprintf("the %s ask %s of %s#%d", kind, a.ID, p.Repository, p.Number), "")
+	if err := st.j.Asks.Put(ctx, a); err != nil {
+		return fail(t.module, fmt.Sprintf("the check of %s#%d could not be asked: %v", p.Repository, p.Number, err))
+	}
+	step, err := st.j.Asks.Wait(ctx, a)
+	if err != nil {
+		if ctx.Err() != nil {
+			return fail(t.module, ctx.Err().Error())
+		}
+		return fail(t.module, fmt.Sprintf("the check of %s#%d: %v", p.Repository, p.Number, err))
+	}
+	// The fetch and the digests are what of the ask's time its levels' running did not take (Took.Clone).
+	took := time.Duration(0)
+	if !step.Started.IsZero() && step.Ended.After(step.Started) {
+		took = step.Ended.Sub(step.Started)
+	}
+	t.node = step.Node
+	st.nodes[step.Node] = true
+	st.c.Progress.Set(fmt.Sprintf("judge the check of %s#%d", p.Repository, p.Number), step.Node)
+	if step.State != delivery.StepPassed {
+		return fail(step.Node, fmt.Sprintf("the check of %s#%d %s: %s%s", p.Repository, p.Number, step.State, step.Reason, pinHint(st.c, step.Reason)))
+	}
+	var answer delivery.CheckAnswer
+	if err := json.Unmarshal(step.Result, &answer); err != nil {
+		return fail(step.Node, fmt.Sprintf("the check of %s#%d answered what is not a check: %s", p.Repository, p.Number, step.Result))
+	}
+	if err := json.Unmarshal(answer.Fetch, &t.fetched); err != nil || t.fetched.Workspace == "" {
+		return fail(step.Node, fmt.Sprintf("the fetch of %s#%d answered no workspace: %s", p.Repository, p.Number, answer.Fetch))
+	}
+	if len(t.fetched.Conflicts) > 0 {
+		if st.c.Try == nil {
+			st.j.writePreview(ctx, p, append(*merged, t.fetched))
+		}
+		return fail(step.Node, fmt.Sprintf("%s#%d does not merge into the trunk: files in conflict: %s", p.Repository, p.Number, strings.Join(t.fetched.Conflicts, ", ")))
+	}
+	t.changed = t.fetched.Changed
+	if !changesBuildGo(p.Repository, t.changed) {
+		t.runner = "" // the build module used no runner: the merge does not change it
+	}
+	*merged = append(*merged, t.fetched)
+	if v := st.checkPinsOf(ctx, t); v != nil {
+		return v
+	}
+	ran := 0.0
+	for _, la := range answer.Levels {
+		v, elapsed := st.level(ctx, t, la)
+		ran += elapsed
+		if v != nil {
+			st.clone += max(0, took-time.Duration(ran*float64(time.Second)))
+			return v
+		}
+	}
+	st.clone += max(0, took-time.Duration(ran*float64(time.Second)))
+	return nil
+}
+
+// level judges one level of a check ask's answer as the tools' answers were judged: the digest keys the kept verdicts
+// of the packages that passed, the kept ones taken are counted, and the first test result that did not pass is the
+// verdict. It answers the level's running time (its tests' and setup's).
+func (st *state) level(ctx context.Context, t *target, la delivery.LevelAnswer) (*delivery.Verdict, float64) {
+	level := la.Level
+	a := st.levels[level]
+	if a == nil {
+		return fail(t.node, fmt.Sprintf("the check of %s#%d answered the level %q, which is no level", t.pull.Repository, t.pull.Number, level)), 0
+	}
+	var digests map[string]string
+	if t.module == buildrun.GoBuildModule && len(la.Digest) > 0 {
+		var d Digested
+		if err := json.Unmarshal(la.Digest, &d); err == nil {
+			digests = d.Packages
+			if t.runner != "" {
+				t.judgedBy(d.JudgedBy) // the installed module judged it: the runner is not used again
+			}
+		}
+	}
+	if t.runner != "" && la.Judged != "" {
+		t.judgedBy(la.Judged) // the candidate judged the level: nothing is kept (ADR 0535 §4)
+	}
+	for _, k := range la.Kept {
+		a.kept += k.Tests
+	}
+	elapsed := 0.0
+	for _, raw := range la.Tests {
+		var res Tested
+		if err := json.Unmarshal(raw, &res); err != nil {
+			return fail(t.node, fmt.Sprintf("the %s level of %s#%d answered what is not a result: %v", level, t.pull.Repository, t.pull.Number, err)), elapsed
+		}
+		if t.runner != "" {
+			t.judgedBy(res.JudgedBy)
+		}
+		elapsed += res.Elapsed + res.Setup
+		if t.module == buildrun.NodeBuildModule {
+			if !res.NoTests {
+				a.run++ // a Node package is counted whole: its build module counts no tests (ADR 0484 clause 10)
+			}
+		} else {
+			a.run += res.Tests
+			a.skipped += res.Skipped
+			a.slowest = append(a.slowest, res.Slowest...)
+		}
+		a.elapsed += res.Elapsed
+		a.setup += res.Setup
+		a.over = a.over || res.OverBound
+		if len(digests) > 0 {
+			if _, err := st.j.Kept.KeepPasses(ctx, t.pull.Repository, level, t.toolchain, res, digests, st.j.now()); err != nil {
+				st.j.logf("%s#%d: a passing package could not be kept: %v", t.pull.Repository, t.pull.Number, err)
+			}
+		}
+		if !res.Passed {
+			return levelFailure(t, level, res), elapsed
+		}
+	}
+	return nil, elapsed
+}
+
 // changesPackage says whether the merge of a pull request changes a file inside the named paths of one of its repository's
 // TypeScript packages: a change of the manifest alone, or of files outside those paths, does not (ADR 0500 §5).
 func (j *Examiner) changesPackage(p Pull, merged []Fetched) bool {
@@ -428,51 +481,6 @@ func (j *Examiner) changesPackage(p Pull, merged []Fetched) bool {
 	return false
 }
 
-// isTestFile says whether a repository-relative path is a test file of the languages the checker judges: Go's _test.go and
-// the TypeScript module's .test. and .spec. files and test directories.
-func isTestFile(p string) bool {
-	switch {
-	case strings.HasSuffix(p, "_test.go"):
-		return true
-	case strings.Contains(p, ".test.") || strings.Contains(p, ".spec."):
-		return true
-	}
-	for _, seg := range strings.Split(path.Dir(p), "/") {
-		if seg == "__tests__" || seg == "test" || seg == "tests" {
-			return true
-		}
-	}
-	return false
-}
-
-// changesTestOf says whether the merge changes a test file of the Go package with the import path pkg: the directory of the
-// file and the import path agree on their last segments, whichever holds the module's directory and path in front.
-func changesTestOf(changed []string, pkg string) bool {
-	for _, f := range changed {
-		if !strings.HasSuffix(f, "_test.go") {
-			continue
-		}
-		dir := path.Dir(f)
-		if dir == pkg || strings.HasSuffix(pkg, "/"+dir) || strings.HasSuffix(dir, "/"+pkg) {
-			return true
-		}
-	}
-	return false
-}
-
-// changesTestIn says whether the merge changes a test file inside the directory of a Node module.
-func changesTestIn(changed []string, dir string) bool {
-	for _, f := range changed {
-		if !isTestFile(f) || strings.HasSuffix(f, "_test.go") {
-			continue
-		}
-		if dir == "." || dir == "" || strings.HasPrefix(f, strings.TrimSuffix(dir, "/")+"/") {
-			return true
-		}
-	}
-	return false
-}
-
 // failedName names a failure: its package and test.
 func failedName(f Failure) string {
 	if f.Test == "" {
@@ -514,161 +522,3 @@ func levelFailure(t *target, level string, res Tested) *delivery.Verdict {
 	}
 	return &v
 }
-
-// runTarget runs one level of a target: first the packages the change's own tests are in (priority), then the others.
-func (st *state) runTarget(ctx context.Context, t *target, level string, priority bool) *delivery.Verdict {
-	if t.module == buildrun.NodeBuildModule {
-		return st.runNode(ctx, t, level, priority)
-	}
-	return st.runGo(ctx, t, level, priority)
-}
-
-// A level's work is planned once for a target: the digest of each package, the kept verdicts taken, the packages left to run.
-func (st *state) planGo(ctx context.Context, t *target, level string) *delivery.Verdict {
-	if t.plans[level] != nil {
-		return nil
-	}
-	plan := &goPlan{digests: map[string]string{}}
-	t.plans[level] = plan
-	if st.c.Try != nil && st.c.Try.Run != "" {
-		// A try of some tests runs them alone: a partial run proves no package, so nothing is taken or kept.
-		plan.all = true
-		return nil
-	}
-	raw, err := st.step(ctx, t, "digest", fmt.Sprintf("digest the %s level of %s#%d on %s", level, t.pull.Repository, t.pull.Number, t.node),
-		t.stepArgs(map[string]any{"workspace": t.fetched.Workspace, "level": level}))
-	var d Digested
-	if err == nil {
-		err = json.Unmarshal(raw, &d)
-	}
-	if ctx.Err() != nil {
-		return fail(t.node, ctx.Err().Error())
-	}
-	if err == nil && t.runner != "" && t.judgedBy(d.JudgedBy) {
-		// The candidate's digest decides which verdicts would be taken: every package runs and nothing is kept (ADR 0535 §4).
-		plan.all = true
-		return nil
-	}
-	if err != nil || len(d.Packages) == 0 {
-		// The build module named no digest (a level it cannot digest here): the level runs whole and keeps nothing.
-		if err != nil {
-			st.j.logf("%s#%d: no digest of the %s level, so it runs whole: %v", t.pull.Repository, t.pull.Number, level, err)
-		}
-		plan.all = true
-		return nil
-	}
-	if !slices.Equal(d.Beside, t.beside) {
-		// The siblings the tests read are not all in the digest (a build module before DigestVersion 3, or another set): a
-		// package whose tests read one is never kept, nor taken from a verdict kept for other inputs (ADR 0444, L5).
-		st.j.logf("%s#%d: the %s level's digest covers the siblings %v, not %v, so it runs whole and keeps nothing", t.pull.Repository, t.pull.Number, level, d.Beside, t.beside)
-		plan.all = true
-		return nil
-	}
-	plan.digests = d.Packages
-	a := st.levels[level]
-	pkgs := make([]string, 0, len(d.Packages))
-	for p := range d.Packages {
-		pkgs = append(pkgs, p)
-	}
-	sort.Strings(pkgs)
-	for _, p := range pkgs {
-		k, found, err := st.j.Kept.Lookup(ctx, level, d.Packages[p])
-		if err != nil {
-			st.j.logf("the kept verdict of %s at %s cannot be read, so it runs: %v", p, level, err)
-		}
-		if found {
-			a.kept += k.Tests
-			continue
-		}
-		plan.todo = append(plan.todo, p)
-	}
-	return nil
-}
-
-func (st *state) runGo(ctx context.Context, t *target, level string, priority bool) *delivery.Verdict {
-	if v := st.planGo(ctx, t, level); v != nil {
-		return v
-	}
-	plan := t.plans[level]
-	var run []string
-	switch {
-	case plan.all:
-		if priority {
-			return nil // nothing to put first: the level runs whole after
-		}
-	default:
-		for _, p := range plan.todo {
-			if changesTestOf(t.changed, p) == priority {
-				run = append(run, p)
-			}
-		}
-		if len(run) == 0 {
-			return nil
-		}
-	}
-	args := t.stepArgs(map[string]any{"workspace": t.fetched.Workspace, "level": level})
-	if run != nil {
-		args["packages"] = run
-	}
-	if st.c.Try != nil && st.c.Try.Run != "" {
-		args["run"] = st.c.Try.Run // build_go_test's go test -run pattern
-	}
-	raw, err := st.step(ctx, t, "test", fmt.Sprintf("test the %s level of %s#%d on %s", level, t.pull.Repository, t.pull.Number, t.node), args)
-	if err != nil {
-		return fail(t.node, fmt.Sprintf("the %s level of %s#%d: %v", level, t.pull.Repository, t.pull.Number, err))
-	}
-	var res Tested
-	if err := json.Unmarshal(raw, &res); err != nil {
-		return fail(t.node, fmt.Sprintf("the %s level of %s#%d answered what is not a result: %v", level, t.pull.Repository, t.pull.Number, err))
-	}
-	if t.runner != "" {
-		t.judgedBy(res.JudgedBy)
-	}
-	a := st.levels[level]
-	a.run += res.Tests
-	a.skipped += res.Skipped
-	a.elapsed += res.Elapsed
-	a.setup += res.Setup
-	a.over = a.over || res.OverBound
-	a.slowest = append(a.slowest, res.Slowest...)
-	if len(plan.digests) > 0 {
-		if _, err := st.j.Kept.KeepPasses(ctx, t.pull.Repository, level, t.toolchain, res, plan.digests, st.j.now()); err != nil {
-			st.j.logf("%s#%d: a passing package could not be kept: %v", t.pull.Repository, t.pull.Number, err)
-		}
-	}
-	if !res.Passed {
-		return levelFailure(t, level, res)
-	}
-	return nil
-}
-
-func (st *state) runNode(ctx context.Context, t *target, level string, priority bool) *delivery.Verdict {
-	for _, dir := range t.fetched.Modules {
-		if changesTestIn(t.changed, dir) != priority {
-			continue
-		}
-		raw, err := st.step(ctx, t, "test", fmt.Sprintf("test the %s level of %s#%d (%s) on %s", level, t.pull.Repository, t.pull.Number, dir, t.node),
-			map[string]any{"workspace": t.fetched.Workspace, "module": dir, "level": level})
-		if err != nil {
-			return fail(t.node, fmt.Sprintf("the %s level of %s#%d (%s): %v", level, t.pull.Repository, t.pull.Number, dir, err))
-		}
-		var res Tested
-		if err := json.Unmarshal(raw, &res); err != nil {
-			return fail(t.node, fmt.Sprintf("the %s level of %s#%d (%s) answered what is not a result: %v", level, t.pull.Repository, t.pull.Number, dir, err))
-		}
-		if res.Module == "" {
-			res.Module = dir
-		}
-		a := st.levels[level]
-		if !res.NoTests {
-			a.run++ // a Node package is counted whole: its build module counts no tests (ADR 0484 clause 10)
-		}
-		a.elapsed += res.Elapsed
-		a.setup += res.Setup
-		a.over = a.over || res.OverBound
-		if !res.Passed {
-			return levelFailure(t, level, res)
-		}
-	}
-	return nil
-}
diff --git a/modules/mesh-delivery-checker/internal/check/pins.go b/modules/mesh-delivery-checker/internal/check/pins.go
index f1e2937..c07a8c4 100644
--- a/modules/mesh-delivery-checker/internal/check/pins.go
+++ b/modules/mesh-delivery-checker/internal/check/pins.go
@@ -55,19 +55,19 @@ func SDKPin(goMod string) (commit string, ok bool) {
 	return "", false
 }
 
-// checkPins refuses a Go member whose go.mod names a mesh-sdk commit that is neither on mesh-sdk's trunk nor the head of the
+// checkPinsOf refuses a Go member whose go.mod names a mesh-sdk commit that is neither on mesh-sdk's trunk nor the head of the
 // group's mesh-sdk pull request. It reads each go.mod the fetch named from the forge: the one the check builds, which is the
 // head's when the head holds the file and the trunk's when it does not, since a module added on the trunk after the branch was
 // cut is in the merge and not at the head (issue 1845). It answers nil when every pin is the group's.
-func (st *state) checkPins(ctx context.Context) verdictPtr {
+func (st *state) checkPinsOf(ctx context.Context, t *target) verdictPtr {
 	if st.j.Forge == nil {
 		return nil
 	}
 	sdk := st.c.member(SDKRepository)
-	for _, t := range st.targets {
-		if t.module != goModule || t.pull.Repository == SDKRepository {
-			continue
-		}
+	if t.module != goModule || t.pull.Repository == SDKRepository {
+		return nil
+	}
+	{
 		for _, dir := range t.fetched.Modules {
 			file := path.Join(dir, "go.mod")
 			st.c.Progress.Set(fmt.Sprintf("read %s of %s#%d", file, t.pull.Repository, t.pull.Number), t.node)
diff --git a/modules/mesh-delivery-checker/internal/check/pins_test.go b/modules/mesh-delivery-checker/internal/check/pins_test.go
index 9d0c6bb..ee8f873 100644
--- a/modules/mesh-delivery-checker/internal/check/pins_test.go
+++ b/modules/mesh-delivery-checker/internal/check/pins_test.go
@@ -97,7 +97,7 @@ func TestAMemberPinnedToTheSDKMembersHeadPassesAndIsBuiltAgainstIt(t *testing.T)
 	var besideSDK bool
 	for _, f := range b.steps.tool("fetch") {
 		if f.args["repository"] == repoA {
-			refs, _ := f.args["beside"].([]BesideRef)
+			refs, _ := refsOf(f.args["beside"]), true
 			for _, r := range refs {
 				besideSDK = besideSDK || (r.Repository == repoSDK && r.Commit == head2)
 			}
@@ -116,9 +116,8 @@ func TestAMemberPinnedToAnOlderHeadOfTheSDKMemberFailsNamingTheMemberAndTheCommi
 		!strings.Contains(f.Words, "neither on mesh-sdk's trunk nor the group's head") || !strings.Contains(f.Words, short12(head2)) {
 		t.Fatalf("verdict = %+v", v)
 	}
-	if n := len(b.steps.tool("test")); n != 0 {
-		t.Errorf("%d test steps ran after a stale pin", n)
-	}
+	// Since R4g the levels run in the member's one check ask before its go.mod pins are judged (ADR 0525 §3); the verdict is
+	// still the pin's, whatever the levels said.
 }
 
 func TestAMemberPinnedToACommitOnTheTrunkPasses(t *testing.T) { // 1624/AC2, AC4
@@ -213,7 +212,7 @@ func besideOf(t *testing.T, b *bench, repository string) map[string]BesideRef {
 	out := map[string]BesideRef{}
 	for _, f := range b.steps.tool("fetch") {
 		if f.args["repository"] == repository {
-			refs, _ := f.args["beside"].([]BesideRef)
+			refs, _ := refsOf(f.args["beside"]), true
 			for _, r := range refs {
 				out[r.Repository] = r
 			}
@@ -228,7 +227,8 @@ func TestTheSiblingsAreWhereTheTestsStateThem(t *testing.T) { // review D2, ADR
 	b := newBench(t)
 	b.ex.Trunks = trunksOf(t, map[string]string{controller: trunkA, catalogue: trunkS, host: trunkA2, SDKRepository: "9999999999999999999999999999999999999999"})
 	b.ex.Runs = runsAt{"mesh-host": hostRuns}
-	forge := &fakeForge{goMods: map[string]string{controller + " go.mod " + head1: capturedGoMod(t, "cb54756c3865")}, onTrunk: map[string]bool{"cb54756c3865": true}}
+	forge := &fakeForge{goMods: map[string]string{controller + " go.mod " + head1: capturedGoMod(t, "cb54756c3865"),
+		catalogue + " go.mod " + head2: "module git.novox.be/novox/mesh-catalog\n"}, onTrunk: map[string]bool{"cb54756c3865": true}}
 	b.ex.Forge = forge
 	// A group of the controller and the catalogue: the controller's tests read the catalogue's trunk, not the group's head.
 	b.judge(t, caseOf(t, pullOf(controller, 7, head1), pullOf(catalogue, 12, head2)))
diff --git a/modules/mesh-delivery-checker/internal/check/try_test.go b/modules/mesh-delivery-checker/internal/check/try_test.go
index 65b89b5..5c9e5a0 100644
--- a/modules/mesh-delivery-checker/internal/check/try_test.go
+++ b/modules/mesh-delivery-checker/internal/check/try_test.go
@@ -153,18 +153,7 @@ func TestAFailingTryNamesWhatFailedAndAStepThatCannotRunIsAnError(t *testing.T)
 	if got := readTry(t, kv, id); got.State != TryFail || len(got.Failed) != 1 || !strings.Contains(got.Failed[0], "TestThreeIsFour") {
 		t.Errorf("try = %+v", got)
 	}
-	// No build node: the try could not run, which is an error, not a failure of the change.
-	kv2 := newMemKV()
-	b2 := newBench(t)
-	b2.ex.Toolchains = entries{}
-	id2, _ := AskTry(memTries{kv2}, tryTrunks, TryAsk{Repository: repoA, Head: head1}, time.Now())
-	tr2 := &Tryer{Tries: kv2, Judge: b2.ex}
-	raw, _, _, _ = kv2.Get(ctx, id2)
-	tr2.Put(ctx, id2, raw)
-	tr2.Wait()
-	if got := readTry(t, kv2, id2); got.State != TryError {
-		t.Errorf("try with no node = %+v, want error", got)
-	}
+	// No build node is no error since R4g: the try's ask waits in the check stream until a node pulls it (ADR 0525 §4).
 }
 
 func TestATryWaitsWhileADeliveryBuildsAndATryLeftRunningIsTakenOver(t *testing.T) {