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 9eeb0c8f..05fe877e 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
@@ -15,6 +15,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"testing"
+	"testing/fstest"
 	"time"
 
 	"github.com/nats-io/nats-server/v2/server"
@@ -28,6 +29,7 @@ import (
 	"git.novox.be/novox/mesh-sdk/go/process"
 
 	"mesh-delivery-checker/internal/check"
+	"mesh-delivery-checker/rules"
 )
 
 // busConf is the shape of the composed accounts file (mesh-controller internal/broker): one account with JetStream, the
@@ -91,6 +93,33 @@ type fakeBuildModules struct {
 	beside map[string][]string
 	// names are the nodes' names the last check ask carried, for the names check (ADR 0567 §12).
 	names []string
+	// inputs is the checker's state of run inputs; runs counts the run asks answered, and broken, when set, is why the
+	// checking program does not build (issue 1921).
+	inputs jetstream.KeyValue
+	runs   atomic.Int32
+	broken atomic.Value
+}
+
+// run answers a run ask as mesh-build-go does: the checking program's work (rules.Program) over the input the ask names,
+// read from the checker's state inputs and checked against its digest, with no heads of its own laid.
+func (f *fakeBuildModules) run(ctx context.Context, a delivery.StepAsk) (any, error) {
+	f.runs.Add(1)
+	if why, _ := f.broken.Load().(string); why != "" {
+		return nil, errors.New(why)
+	}
+	answer := delivery.RunAnswer{Built: true, Key: "program-0123456789abcdef"}
+	out, err := rules.Program(a.Run.Args, func() ([]byte, error) {
+		e, err := f.inputs.Get(ctx, a.Run.Input.Digest)
+		if err != nil {
+			return nil, err
+		}
+		return e.Value(), a.Run.Input.Verify(e.Value())
+	}, fstest.MapFS{})
+	if err != nil {
+		answer.Exit, answer.Said = 2, err.Error()
+	}
+	answer.Output = out
+	return answer, nil
 }
 
 func (f *fakeBuildModules) count(tool string) int {
@@ -199,6 +228,9 @@ func (f *fakeBuildModules) serve(t *testing.T, module string, kept jetstream.Key
 				f.names = a.Check.NodeNames
 				f.mu.Unlock()
 			}
+			if a.Run != nil {
+				return f.run(ctx, a)
+			}
 			return gobuild.RunAsk(ctx, steps, a)
 		}}
 	go func() { _ = p.Pull(f.ctx) }()
@@ -398,7 +430,7 @@ func startBed(t *testing.T) *bed {
 		delivery.CheckerOwedBucket: delivery.CheckerOwedHistory, delivery.PreviewsBucket: delivery.PreviewsHistory, delivery.CandidatesBucket: delivery.CandidatesHistory,
 		delivery.ModulesBucket: delivery.ModulesHistory, delivery.ManifestsBucket: delivery.ManifestsHistory, delivery.SourceBucket: delivery.SourceHistory,
 		delivery.PresenceBucket: delivery.PresenceHistory, delivery.HaveBucket: delivery.HaveHistory, check.TriesBucket: 1,
-		delivery.TurnsBucket: delivery.TurnsHistory, delivery.BuilderBuildsBucket: 1} {
+		delivery.TurnsBucket: delivery.TurnsHistory, delivery.BuilderBuildsBucket: 1, check.InputsBucket: 1} {
 		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: name, History: uint8(history)})
 		if err != nil {
 			t.Fatal(err)
@@ -420,7 +452,7 @@ func startBed(t *testing.T) *bed {
 		b.setHealth(t, "n1", module)
 	}
 	b.serveForge(t, ctl)
-	b.fake = &fakeBuildModules{js: js, ctx: ctx, calls: map[string]int{}}
+	b.fake = &fakeBuildModules{js: js, ctx: ctx, calls: map[string]int{}, inputs: b.buckets[check.InputsBucket]}
 	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")
@@ -647,6 +679,15 @@ func TestCheckerJudgesACandidateAndOwesItsStatus(t *testing.T) { // N6/AC5, 1300
 	if got := asked(); len(got) == 0 || got[0].Candidate != key {
 		t.Errorf("n1's engine was asked %+v, want the check's candidate %s", got, key)
 	}
+	// Issue 1921 (B0): the verdict is the checking program's, built at the group's mesh-delivery head over its input kept in
+	// the state inputs, two run asks a check (the seat list, the verdict); the verdict names the program's build.
+	if by := v.JudgedBy; by == nil || by.Program.Commit != head1 || by.Program.Package != check.CheckingProgramPackage ||
+		by.Key != "program-0123456789abcdef" || len(by.Heads) != 1 || by.Heads[0].Commit != head1 {
+		t.Errorf("judged by %+v, want the checking program at the head %s", v.JudgedBy, head1)
+	}
+	if n := b.fake.runs.Load(); n != 4 {
+		t.Errorf("%d run asks, want two for each of the two checks", n)
+	}
 	b.fake.mu.Lock()
 	names := b.fake.names
 	b.fake.mu.Unlock()
@@ -978,7 +1019,7 @@ func TestTheCheckerSaysOwedReadableOnTheBus(t *testing.T) { // R2-1
 	}
 	if said.Module != "mesh-delivery-checker" || said.Node != "n1" || !said.Keeps("owed") || !said.Readable("owed") ||
 		!said.Readable("previews") || !said.Readable("verdicts") || !said.Readable("kept") || !said.Readable("tries") || said.Readable("hearing") ||
-		!said.Keeps("asks") || said.Readable("asks") || len(said.States) != 7 {
-		t.Fatalf("the checker said %+v, want its seven states, asks and hearing its own, with kept, owed, previews, tries and verdicts readable, tries by the delivery view (1929/AC4; 1887 A5b; build_usage)", said)
+		!said.Keeps("asks") || said.Readable("asks") || !said.Readable("inputs") || len(said.States) != 8 {
+		t.Fatalf("the checker said %+v, want its eight states, asks and hearing its own, with inputs, kept, owed, previews, tries and verdicts readable, tries by the delivery view, inputs by the Go build module (1929/AC4; 1887 A5b; build_usage; 1921)", said)
 	}
 }