diff --git a/go/catalogue/busnames.go b/go/catalogue/busnames.go
new file mode 100644
index 00000000..fc1cf052
--- /dev/null
+++ b/go/catalogue/busnames.go
@@ -0,0 +1,88 @@
+package catalogue
+
+import (
+	"regexp"
+	"slices"
+	"sort"
+	"strings"
+)
+
+// The names of what a module keeps on the bus, as one rule (design 25 § 12.1; novox/hq ADR 0666 §16): the bus module
+// creates them from a module's entries and the grants part grants them, and both take the names from here.
+
+// BusNameSeparator joins a module's name and an entry's local name into the name the mesh gives the entry on the bus.
+const BusNameSeparator = "_"
+
+// SentObjectsLocal is the local name of a module's store of sent objects (the bodies of a reply or an event over the
+// per-message limit): the bus module plans `<module>_sent-objects` for every module, and no entry may take the name.
+const SentObjectsLocal = "sent-objects"
+
+// ObjectsSuffix ends the local name of the object store beside a state: `<state>-objects`.
+const ObjectsSuffix = "-objects"
+
+// safeToken is a name that is one plain subject token.
+var safeToken = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
+
+// BusName is `<module>_<local>`, the name the mesh gives an entry on the bus.
+func BusName(module, local string) string { return module + BusNameSeparator + local }
+
+// StateObjectsName is the local name of the object store that holds the large values of the state `state`.
+func StateObjectsName(state string) string { return state + ObjectsSuffix }
+
+// SentObjectsName is the bus name of a module's store of sent objects.
+func SentObjectsName(module string) string { return BusName(module, SentObjectsLocal) }
+
+// BusStateStreams are the streams one bus-state entry of module is kept in on the bus, by the mesh's names
+// `<module>_<local>`: a stream's own; a key-value bucket's KV_ stream with the OBJ_ stream of its object store
+// `<local>-objects`; an object store's OBJ_ stream; a ledger's history stream, its snapshot stream, and its state and
+// index buckets' KV_ streams. A name that is not one plain subject token names nothing.
+func BusStateStreams(module string, e BusStateEntry) []string {
+	base := BusName(module, e.Name)
+	if !safeToken.MatchString(base) || strings.Contains(e.Name, BusNameSeparator) || strings.Contains(module, BusNameSeparator) {
+		return nil
+	}
+	var out []string
+	switch e.Storage {
+	case StorageKeyValue:
+		out = []string{"KV_" + base}
+		if e.Template == TemplateState {
+			out = append(out, "OBJ_"+BusName(module, StateObjectsName(e.Name)))
+		}
+	case StorageObjectStore:
+		out = []string{"OBJ_" + base}
+	case StorageLedger:
+		out = []string{base, base + "_snapshot", "KV_" + base + "_state"}
+		for _, t := range e.Types {
+			for _, ix := range t.Indexes {
+				if safeToken.MatchString(ix.Name) {
+					out = append(out, "KV_"+base+"_index-"+ix.Name)
+				}
+			}
+		}
+	default:
+		out = []string{base}
+	}
+	sort.Strings(out)
+	return slices.Compact(out)
+}
+
+// ObjectNameClashes are the local names of a module's bus-state entries that meet a name the mesh makes itself: the
+// name of a state's object store (`<state>-objects` beside the state `<state>`) and the store of sent objects. The
+// indexer's judge refuses each.
+func ObjectNameClashes(entries []BusStateEntry) []string {
+	states := map[string]bool{}
+	for _, e := range entries {
+		if e.Storage == StorageKeyValue && e.Template == TemplateState {
+			states[e.Name] = true
+		}
+	}
+	var out []string
+	for _, e := range entries {
+		stem, ok := strings.CutSuffix(e.Name, ObjectsSuffix)
+		if e.Name == SentObjectsLocal || (ok && states[stem]) {
+			out = append(out, e.Name)
+		}
+	}
+	sort.Strings(out)
+	return slices.Compact(out)
+}
diff --git a/go/catalogue/busnames_test.go b/go/catalogue/busnames_test.go
new file mode 100644
index 00000000..087b6484
--- /dev/null
+++ b/go/catalogue/busnames_test.go
@@ -0,0 +1,38 @@
+package catalogue
+
+import (
+	"slices"
+	"testing"
+)
+
+// ADR 0666 §16: the bus names of an entry are one rule. A state entry answers its bucket's stream and the stream of
+// its object store; a local name that meets a name the mesh makes is a clash for the judge.
+func TestTheBusNamesOfAnEntryAreOneRule(t *testing.T) {
+	state := BusStateEntry{Name: "views", Storage: StorageKeyValue, Template: TemplateState}
+	rows := []struct {
+		name    string
+		entry   BusStateEntry
+		streams []string
+	}{
+		{"a state: its bucket and its object store", state, []string{"KV_m_views", "OBJ_m_views-objects"}},
+		{"a key-value that is not a state template: its bucket only", BusStateEntry{Name: "x", Storage: StorageKeyValue}, []string{"KV_m_x"}},
+		{"an object store", BusStateEntry{Name: "blobs", Storage: StorageObjectStore, Template: TemplateObjects}, []string{"OBJ_m_blobs"}},
+		{"a stream", BusStateEntry{Name: "log", Storage: StorageStream, Template: TemplateLog}, []string{"m_log"}},
+		{"a ledger", BusStateEntry{Name: "l", Storage: StorageLedger, Template: TemplateLedger}, []string{"KV_m_l_state", "m_l", "m_l_snapshot"}},
+		{"a name that is not one token", BusStateEntry{Name: "a.b", Storage: StorageStream}, nil},
+		{"a local name holding the separator", BusStateEntry{Name: "a_b", Storage: StorageStream}, nil},
+	}
+	for _, r := range rows {
+		if got := BusStateStreams("m", r.entry); !slices.Equal(got, r.streams) {
+			t.Errorf("%s: streams %v, want %v", r.name, got, r.streams)
+		}
+	}
+	if got := SentObjectsName("m"); got != "m_sent-objects" {
+		t.Errorf("sent store %q", got)
+	}
+	clash := []BusStateEntry{state, {Name: "views-objects", Storage: StorageObjectStore}, {Name: "other-objects", Storage: StorageObjectStore},
+		{Name: SentObjectsLocal, Storage: StorageObjectStore}}
+	if got := ObjectNameClashes(clash); !slices.Equal(got, []string{"sent-objects", "views-objects"}) {
+		t.Errorf("clashes %v", got)
+	}
+}