diff --git a/modules/mesh-delivery-builder/go.mod b/modules/mesh-delivery-builder/go.mod
index 9b9cb54..f1d1a30 100644
--- a/modules/mesh-delivery-builder/go.mod
+++ b/modules/mesh-delivery-builder/go.mod
@@ -3,7 +3,7 @@ module mesh-delivery-builder
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101085317-790d1c82d027
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )
diff --git a/modules/mesh-delivery-builder/go.sum b/modules/mesh-delivery-builder/go.sum
index 37e06a8..c368184 100644
--- a/modules/mesh-delivery-builder/go.sum
+++ b/modules/mesh-delivery-builder/go.sum
@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101085317-790d1c82d027 h1:a33dsavoaqllh40eVICbhxi6Kero1EGSjt1V+2fa2Hk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101085317-790d1c82d027/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066 h1:rpYDAiJ+245xHvmYdta/hE3gSGEoebglr4ujdOoFH/8=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
diff --git a/modules/mesh-delivery-builder/internal/build/askagain.go b/modules/mesh-delivery-builder/internal/build/askagain.go
index 1b03da9..23a0974 100644
--- a/modules/mesh-delivery-builder/internal/build/askagain.go
+++ b/modules/mesh-delivery-builder/internal/build/askagain.go
@@ -317,6 +317,11 @@ func (b *Builder) waitOnce(ctx context.Context, ask delivery.StepAsk, again <-ch
 		defer stop()
 	}
 	step, err := b.Asks.Wait(wait, ask)
+	if d, declined := delivery.DeclinedOf(step); err == nil && declined {
+		// A build node on another toolchain than the agreed one sat out (ADR 0584 clause 2): the ask is put again, for a node
+		// on the agreed one to take. The most askings stays the bound, and the build then fails with these reasons in it.
+		return step, strings.TrimSpace(step.Node + " declined: " + step.Reason + " (lacks " + strings.Join(d.Lacks, ", ") + ")"), errAgain
+	}
 	if err == nil && buildrun.IsLost(step) {
 		// The build seat gave the ask up (issue 734): it can no longer be answered, so it is asked again now, with the
 		// words of why, not at the check bound.
diff --git a/modules/mesh-delivery-builder/internal/build/run.go b/modules/mesh-delivery-builder/internal/build/run.go
index 4578824..f4c2357 100644
--- a/modules/mesh-delivery-builder/internal/build/run.go
+++ b/modules/mesh-delivery-builder/internal/build/run.go
@@ -506,10 +506,11 @@ func (b *Builder) stale(m delivery.Module, plan Plan) string {
 			continue // an archive is packed with no toolchain
 		}
 		language := buildrun.LanguageOf[bm]
-		tc, none := delivery.AgreedToolchain(b.Toolchains.Entries(language))
-		if none != "" {
-			return fmt.Sprintf("the %s toolchain is not agreed: %s", language, none)
+		ag := delivery.ToolchainAgreement(b.Toolchains.Entries(language))
+		if ag.Wait != "" {
+			return fmt.Sprintf("the %s toolchain is not agreed: %s", language, ag.Wait)
 		}
+		tc := ag.Toolchain
 		want, ok := m.Toolchains[language]
 		if !ok || want.Version != tc.Version || want.Recipe != tc.Recipe {
 			return fmt.Sprintf("the fingerprint names %s %s (recipe %s) and the nodes agree on %s (recipe %s)", language, want.Version, want.Recipe, tc.Version, tc.Recipe)
@@ -543,7 +544,8 @@ func (b *Builder) build(ctx context.Context, module string, m delivery.Module, p
 	repository := delivery.RepositoryName(m.Repository)
 	var lanes []*lane
 	used := map[string]delivery.ToolchainUsed{}
-	var kept []string // build modules whose artifacts stay as the prior done key has them
+	var sitting []string // the nodes that sit out of a language's build, said in the key's step (ADR 0584 clause 2)
+	var kept []string    // build modules whose artifacts stay as the prior done key has them
 	for _, bm := range plan.Modules() {
 		if prior != nil && len(only) > 0 && !only[bm] {
 			kept = append(kept, bm)
@@ -553,10 +555,12 @@ func (b *Builder) build(ctx context.Context, module string, m delivery.Module, p
 		if bm != ImageBuildModule && plan.NeedsToolchain(bm) {
 			// The ask names the toolchain the fingerprint was computed with; a node building with another refuses it.
 			language := buildrun.LanguageOf[bm]
-			tc, none := delivery.AgreedToolchain(b.Toolchains.Entries(language))
-			if none != "" {
-				return failed("the %s toolchain is not agreed: %s", language, none)
+			ag := delivery.ToolchainAgreement(b.Toolchains.Entries(language))
+			if ag.Wait != "" {
+				return failed("the %s toolchain is not agreed: %s", language, ag.Wait)
 			}
+			tc := ag.Toolchain
+			sitting = append(sitting, SittingOutWords(language, ag)...)
 			if want := m.Toolchains[language]; want.Version != tc.Version || want.Recipe != tc.Recipe {
 				return delivery.BuilderBuild{} // the agreed toolchain moved since try looked: nothing is written
 			}
@@ -653,6 +657,9 @@ func (b *Builder) build(ctx context.Context, module string, m delivery.Module, p
 		}
 	}
 	step := "built " + strings.Join(steps, "; ")
+	if len(sitting) > 0 {
+		step += " (" + strings.Join(sitting, "; ") + ")"
+	}
 	if len(used) == 0 {
 		used = nil
 	}
@@ -942,3 +949,13 @@ func LogEnded(module string, m delivery.Module, ref, by string, at time.Time, re
 	e.Made = append([]delivery.BuiltArtifact(nil), result.Artifacts...)
 	return e
 }
+
+// SittingOutWords says, per node that is not on the agreed toolchain of a language, that it sits out and which version
+// it has against the agreed one: "ace sits out: typescript 26.12.1, agreed 26.13.0" (novox/hq ADR 0584 clause 2).
+func SittingOutWords(language string, a delivery.Agreement) []string {
+	var out []string
+	for _, s := range a.SittingOut {
+		out = append(out, fmt.Sprintf("%s sits out: %s %s, agreed %s", s.Node, language, s.Version, a.Toolchain.Version))
+	}
+	return out
+}
diff --git a/modules/mesh-delivery-builder/internal/build/run_test.go b/modules/mesh-delivery-builder/internal/build/run_test.go
index c05901d..2eeb07d 100644
--- a/modules/mesh-delivery-builder/internal/build/run_test.go
+++ b/modules/mesh-delivery-builder/internal/build/run_test.go
@@ -223,6 +223,14 @@ var (
 
 func TestABundleAndAnArchiveAreBuiltOnOneNodeAndDone(t *testing.T) { // 1607/AC7, ADR 0478 clauses 1, 4
 	r := newRig(t, goBundle, archiveA, tsBundle)
+	// ADR 0584: a third node agrees with novox and ace's typescript is the odd one; the build is done and its step says ace sits out.
+	r.tools.Put(buildrun.NodeBuildModule, "g14.typescript", tcValue(t, "typescript", "tsc5"), false)
+	r.tools.Put(buildrun.NodeBuildModule, "ace.typescript", tcValue(t, "typescript", "tsc4"), false)
+	defer func() {
+		if st := r.st.vals[r.key]; !strings.Contains(string(st), "ace sits out: typescript tsc4, agreed tsc5") {
+			t.Errorf("the key does not say ace sits out: %s", st)
+		}
+	}()
 	var logged []delivery.BuildLogEntry
 	var lmu sync.Mutex
 	r.b.Node, r.b.Log = "novox", func(e delivery.BuildLogEntry) { lmu.Lock(); logged = append(logged, e); lmu.Unlock() }
diff --git a/modules/mesh-delivery-checker/go.mod b/modules/mesh-delivery-checker/go.mod
index ce26061..487fb8d 100644
--- a/modules/mesh-delivery-checker/go.mod
+++ b/modules/mesh-delivery-checker/go.mod
@@ -3,7 +3,7 @@ module mesh-delivery-checker
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )
diff --git a/modules/mesh-delivery-checker/go.sum b/modules/mesh-delivery-checker/go.sum
index 5fc11b2..c368184 100644
--- a/modules/mesh-delivery-checker/go.sum
+++ b/modules/mesh-delivery-checker/go.sum
@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915 h1:x8k7IeMirMTxUo8BH+xUO+MDnHYgU+636jl1NIw1wvs=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066 h1:rpYDAiJ+245xHvmYdta/hE3gSGEoebglr4ujdOoFH/8=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
diff --git a/modules/mesh-delivery-indexer/go.mod b/modules/mesh-delivery-indexer/go.mod
index 10c900e..5c3e040 100644
--- a/modules/mesh-delivery-indexer/go.mod
+++ b/modules/mesh-delivery-indexer/go.mod
@@ -3,7 +3,7 @@ module mesh-delivery-indexer
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )
diff --git a/modules/mesh-delivery-indexer/go.sum b/modules/mesh-delivery-indexer/go.sum
index 5fc11b2..c368184 100644
--- a/modules/mesh-delivery-indexer/go.sum
+++ b/modules/mesh-delivery-indexer/go.sum
@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915 h1:x8k7IeMirMTxUo8BH+xUO+MDnHYgU+636jl1NIw1wvs=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101022206-8af6e7266915/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066 h1:rpYDAiJ+245xHvmYdta/hE3gSGEoebglr4ujdOoFH/8=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261101142413-71be15f53066/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=