The node's own key says its agent keeps the bus server, so the assigner writes the bus want only to such a node (ADR 0594 §8)

internal/link/have.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -55,6 +56,9 @@ type haveState struct {
 	// nodeComposes and nodeComposesWhy are whose compositions the node applies and why (HaveNode.Composes), written into
 	// its key.
 	nodeComposes, nodeComposesWhy string
+	// nodeKeeps is what the node agent keeps as it runs on a want without the warrant's mark (HaveNode.Keeps, novox/hq
+	// ADR 0594 §8), written into its key.
+	nodeKeeps []string
 	// written is the build of each module this node-engine wrote a have key for and that the declaration it applied
 	// still holds; removed is each such module the latest declaration no longer holds, with the build its key last
 	// said, until the key is written once with the phase removed (issue 1369, novox/hq ADR 0408 §4: never deleted).
@@ -428,6 +432,7 @@ func (q *Session) writeHaves(ctx context.Context, bus Bus) {
 			facts.SealedAt = s.nodeSealed
 			facts.Candidates = s.nodeCandidates
 			facts.Composes, facts.ComposesWhy = s.nodeComposes, s.nodeComposesWhy
+			facts.Keeps = s.nodeKeeps
 			if raw, err = delivery.EncodeHaveNode(facts); err == nil {
 				want := facts
 				if !q.putHave(write, bucket, key, raw, func(current []byte) bool {
@@ -757,14 +762,17 @@ func (q *Session) NoteCandidates(ctx context.Context, answers map[string]deliver
 	q.writeHaves(ctx, bus)
 }
 
-// NoteComposes says, in the node's own key, whose compositions the node applies (delivery.ComposesOwn) and why: written
-// at each start of its agent, where every have is read (issue 1126).
-func (q *Session) NoteComposes(ctx context.Context, composes, why string) {
+// NoteComposes says, in the node's own key, whose compositions the node applies (delivery.ComposesOwn) and why, and what
+// its agent keeps as it runs on a want without the warrant's mark (delivery.KeepsBusServer, novox/hq ADR 0594 §8): written
+// at each start of its agent, where every have is read (issue 1126). The assigner writes the bus module's want only to
+// a node whose key says it keeps the bus server.
+func (q *Session) NoteComposes(ctx context.Context, composes, why string, keeps ...string) {
 	q.init()
 	s := &q.haves
 	s.mu.Lock()
-	changed := s.nodeComposes != composes || s.nodeComposesWhy != why
+	changed := s.nodeComposes != composes || s.nodeComposesWhy != why || !slices.Equal(s.nodeKeeps, keeps)
 	s.nodeComposes, s.nodeComposesWhy = composes, why
+	s.nodeKeeps = slices.Clone(keeps)
 	known := s.node != nil
 	s.mu.Unlock()
 	if !known || !changed {

internal/link/have_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"strings"
 	"sync"
 	"testing"
@@ -579,6 +580,17 @@ func TestAnAppliedModulesHaveNamesTheFingerprintAndTheDigestAndFollowsItsHealth(
 	if n, _ := delivery.DecodeHaveNode(l.kv["n1.node"].value); n.Candidates != nil {
 		t.Fatalf("an answer left after its group went: %+v", n.Candidates)
 	}
+	// Issue 774, ADR 0594 §4, §8: the bus module's have names what its server runs beside the fingerprint applied, and the
+	// node's key says its agent keeps the bus server.
+	q.NoteModule(context.Background(), ModuleFact{Module: "nats", FP: fp, Composed: dig, Server: "build-1792674595610176744"})
+	if got := l.have(t, "n1.nats"); got.FP != fp || got.Server != "build-1792674595610176744" {
+		t.Fatalf("the bus's have: %+v", got)
+	}
+	q.NoteComposes(context.Background(), delivery.ComposesOwn, "it composes its own", delivery.KeepsBusServer)
+	if n, err := delivery.DecodeHaveNode(l.kv["n1.node"].value); err != nil || !slices.Equal(n.Keeps, []string{delivery.KeepsBusServer}) ||
+		n.Composes != delivery.ComposesOwn {
+		t.Fatalf("the node key does not say it keeps the bus server: %+v %v", n, err)
+	}
 }
 
 // A module applied and running that has nothing long-running to judge is ok once the engine has looked: there is nothing