diff --git a/modules/mesh-build-go/buildstep/seatgen/gogen.go b/modules/mesh-build-go/buildstep/seatgen/gogen.go
index 0c231490d..ec0382747 100644
--- a/modules/mesh-build-go/buildstep/seatgen/gogen.go
+++ b/modules/mesh-build-go/buildstep/seatgen/gogen.go
@@ -180,6 +180,13 @@ func goWhole(m *Module, d seatdef.Definition) ([]byte, []byte, error) {
 	}
 	for _, e := range d.Events {
 		subj := seatdef.EventSubject(d.Seat, e.Name)
+		if e.Keep != nil {
+			fmt.Fprintf(&b, "// Stream%s is the stream %s is kept in.\nconst Stream%s = %q\n\n", ident(e.Name), e.Name, ident(e.Name), keptStream(d.Seat, e.Name))
+		}
+		if parts := e.Parts(); len(parts) > 0 {
+			goPartsSubject(&b, d.Seat, e, parts)
+			continue
+		}
 		if e.ByCaller {
 			fmt.Fprintf(&b, "// Subject%s is where %s is published for one caller.\nfunc Subject%s(caller string) string { return %q + caller }\n\n",
 				ident(e.Name), e.Name, ident(e.Name), subj+".")
@@ -424,6 +431,9 @@ func fixtureTarget(d seatdef.Definition, kind, name string) (string, string, err
 		}
 		for _, msg := range ms {
 			if msg.Name == name {
+				if kind == "event" && len(msg.Parts()) > 0 {
+					return ident(name) + suffix, partsPattern(d.Seat, msg), nil
+				}
 				p := "^" + regexp(subj)
 				if msg.ByCaller {
 					p += `\.[A-Za-z0-9_-]+`
@@ -460,3 +470,61 @@ func regexp(s string) string {
 	}
 	return b.String()
 }
+
+// keptStream is the bus's name of the stream an event naming `keep` is kept in: `SEAT_<seat>_<event>`, which the bus
+// takes (no dot) and the grants part makes (design 47 G §260, §396).
+func keptStream(seat, event string) string { return "SEAT_" + seat + "_" + event }
+
+// subjectExpr is the Go or JavaScript string expression of an event's subject with its parts as arguments.
+func subjectExpr(seat string, e seatdef.Message) []string {
+	var expr []string
+	lit := "mesh.seat." + seat + ".event."
+	for i, tok := range strings.Split(e.SubjectPattern(), ".") {
+		if i > 0 {
+			lit += "."
+		}
+		if strings.HasPrefix(tok, "<") {
+			expr = append(expr, fmt.Sprintf("%q", lit), goParam(tok[1:len(tok)-1]))
+			lit = ""
+			continue
+		}
+		lit += tok
+	}
+	if lit != "" {
+		expr = append(expr, fmt.Sprintf("%q", lit))
+	}
+	return expr
+}
+
+// goPartsSubject writes the subject of an event whose subject carries parts (design 47 G §260, §397): a function taking
+// each part in order, and the filter that hears every instance of it.
+func goPartsSubject(b *bytes.Buffer, seat string, e seatdef.Message, parts []string) {
+	args := make([]string, len(parts))
+	for i, p := range parts {
+		args[i] = goParam(p)
+	}
+	fmt.Fprintf(b, "// Subject%s is where %s is published, on %s.\nfunc Subject%s(%s string) string { return %s }\n\n",
+		ident(e.Name), e.Name, "mesh.seat."+seat+".event."+e.SubjectPattern(), ident(e.Name), strings.Join(args, ", "),
+		strings.Join(subjectExpr(seat, e), " + "))
+	fmt.Fprintf(b, "// Subject%sAll hears every %s.\nconst Subject%sAll = %q\n\n", ident(e.Name), e.Name, ident(e.Name),
+		"mesh.seat."+seat+".event."+e.Local())
+}
+
+// goParam is a part's name as a parameter: its words joined, the first lower-case.
+func goParam(part string) string {
+	id := ident(part)
+	return strings.ToLower(id[:1]) + id[1:]
+}
+
+// partsPattern is the pattern a fixture's subject of an event with parts must match: a part is one token.
+func partsPattern(seat string, e seatdef.Message) string {
+	toks := strings.Split(e.SubjectPattern(), ".")
+	for i, tok := range toks {
+		if strings.HasPrefix(tok, "<") {
+			toks[i] = `[^.*> ]+`
+		} else {
+			toks[i] = regexp(tok)
+		}
+	}
+	return "^" + regexp("mesh.seat."+seat+".event.") + strings.Join(toks, `\.`) + "$"
+}
diff --git a/modules/mesh-build-go/buildstep/seatgen/layout_test.go b/modules/mesh-build-go/buildstep/seatgen/layout_test.go
index 4f097012c..6c714b9a2 100644
--- a/modules/mesh-build-go/buildstep/seatgen/layout_test.go
+++ b/modules/mesh-build-go/buildstep/seatgen/layout_test.go
@@ -291,3 +291,49 @@ func TestATypeScriptContractIsJavaScriptWithItsDeclarations(t *testing.T) {
 		t.Error("the declarations do not import the part")
 	}
 }
+
+// TestADefinitionsActsSubjectsKeepAndCallersAreRead is design 47 G §89, §203, §260, §324, §331's check for the
+// generator: it reads `acts` (a step on every, a language and `kind: image`), `subject`, `keep` and `callers`, and
+// writes each event's subject and the stream `SEAT_<seat>_<event>` of one that names `keep`.
+func TestADefinitionsActsSubjectsKeepAndCallersAreRead(t *testing.T) {
+	m, err := Load("testdata/contracts", "example.org/contracts/go", "@example/contracts")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if acts := m.Seats["a-registry"].Acts; len(acts) != 3 || acts[0].On != "kind:image" || acts[1].On != "every" || acts[2].On != "go" {
+		t.Errorf("acts read as %+v", acts)
+	}
+	files, err := Generate(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	src := string(files["go/seats/aregistry/contract.go"])
+	for _, want := range []string{
+		`const StreamMilestoneAsked = "SEAT_a-registry_milestone-asked"`,
+		`const StreamOwed = "SEAT_a-registry_owed"`,
+		"func SubjectMilestoneAsked(milestone string) string {\n\treturn \"mesh.seat.a-registry.event.milestone-asked.\" + milestone\n}",
+		`SubjectMilestoneAskedAll = "mesh.seat.a-registry.event.milestone-asked.*"`,
+		`func SubjectOwed(repository, number string) string {`,
+		"func SubjectStepEnded(node string) string { return \"mesh.seat.a-registry.event.step-ended.\" + node }",
+	} {
+		if !strings.Contains(src, want) {
+			t.Errorf("the Go contract lacks %q:\n%s", want, src)
+		}
+	}
+	if strings.Contains(src, "StreamStepEnded") {
+		t.Error("an event naming no keep has a stream of its own")
+	}
+	js := string(files["ts/seats/aregistry/index.js"])
+	dts := string(files["ts/seats/aregistry/index.d.ts"])
+	for _, want := range []string{`export const milestoneAskedStream = "SEAT_a-registry_milestone-asked";`,
+		`export function stepEndedSubject(node) {`, `export const milestoneAskedSubjectAll = "mesh.seat.a-registry.event.milestone-asked.*";`} {
+		if !strings.Contains(js, want) {
+			t.Errorf("index.js lacks %q:\n%s", want, js)
+		}
+	}
+	for _, want := range []string{`export declare const owedStream: "SEAT_a-registry_owed";`, `export declare function owedSubject(repository: string, number: string): string;`} {
+		if !strings.Contains(dts, want) {
+			t.Errorf("index.d.ts lacks %q:\n%s", want, dts)
+		}
+	}
+}
diff --git a/modules/mesh-build-go/buildstep/seatgen/testdata/contracts/seats/a-registry/seat.json b/modules/mesh-build-go/buildstep/seatgen/testdata/contracts/seats/a-registry/seat.json
index 42259601e..f992622b6 100644
--- a/modules/mesh-build-go/buildstep/seatgen/testdata/contracts/seats/a-registry/seat.json
+++ b/modules/mesh-build-go/buildstep/seatgen/testdata/contracts/seats/a-registry/seat.json
@@ -1,5 +1,10 @@
 {"format":1,"seat":"a-registry","scope":"mesh","grain":"whole","domain":"Module","decision":"ADR 1","includes":["registry"],
- "verbs":[{"name":"hold","input":{"type":"object"},"answer":{"type":"object"}}],
+ "verbs":[{"name":"hold","class":"read","callers":["invokers","persons","sessions","seat:b-registry","module:gitea","operator","healers","holder:node-backup@same-node"],"input":{"type":"object"},"answer":{"type":"object"}}],
+ "acts":[{"step":"build","on":"kind:image","bound":"60m"},{"step":"check","on":"every"},{"step":"build","on":"go"}],
+ "events":[
+  {"name":"milestone-asked","subject":"milestone-asked.<milestone>","body":{"type":"object"},"keep":{"max-age-days":90,"max-mib":16,"last-per-subject":true}},
+  {"name":"owed","subject":"owed.<repository>.<number>","body":{"type":"object"},"keep":{"max-age-days":7,"max-mib":64}},
+  {"name":"step-ended","subject":"step-ended.<node>","body":{"type":"object"}}],
  "family":{"name":"a-registry.events","max-age-days":7},
  "states":[
   {"name":"asks","template":"state","description":"the asks held, one key per asker and ask",
diff --git a/modules/mesh-build-go/buildstep/seatgen/tsgen.go b/modules/mesh-build-go/buildstep/seatgen/tsgen.go
index a4476b22c..b1b655b12 100644
--- a/modules/mesh-build-go/buildstep/seatgen/tsgen.go
+++ b/modules/mesh-build-go/buildstep/seatgen/tsgen.go
@@ -110,6 +110,14 @@ func tsFiles(m *Module, out map[string][]byte) error {
 			fmt.Fprintf(&o.dts, "export declare const family: { readonly name: %q; readonly maxAgeDays: %d };\n\n", f.Name, f.MaxAgeDays)
 		}
 		for _, e := range d.Events {
+			if e.Keep != nil {
+				fmt.Fprintf(&o.js, "export const %sStream = %q;\n\n", tsName(e.Name), keptStream(d.Seat, e.Name))
+				fmt.Fprintf(&o.dts, "export declare const %sStream: %q;\n\n", tsName(e.Name), keptStream(d.Seat, e.Name))
+			}
+			if parts := e.Parts(); len(parts) > 0 {
+				tsPartsSubject(o, d.Seat, e, parts)
+				continue
+			}
 			tsSubject(o, tsName(e.Name), seatdef.EventSubject(d.Seat, e.Name), e.ByCaller)
 		}
 		for _, a := range d.Accepts {
@@ -235,3 +243,18 @@ func tsType(t *typ) string {
 	}
 	return "unknown"
 }
+
+// tsPartsSubject writes the subject of an event whose subject carries parts, as goPartsSubject does.
+func tsPartsSubject(o *tsOut, seat string, e seatdef.Message, parts []string) {
+	args := make([]string, len(parts))
+	names := make([]string, len(parts))
+	for i, p := range parts {
+		names[i] = goParam(p)
+		args[i] = names[i] + ": string"
+	}
+	all := "mesh.seat." + seat + ".event." + e.Local()
+	fmt.Fprintf(&o.js, "export function %sSubject(%s) {\n  return %s;\n}\n\n", tsName(e.Name), strings.Join(names, ", "), strings.Join(subjectExpr(seat, e), " + "))
+	fmt.Fprintf(&o.js, "export const %sSubjectAll = %q;\n\n", tsName(e.Name), all)
+	fmt.Fprintf(&o.dts, "export declare function %sSubject(%s): string;\n\n", tsName(e.Name), strings.Join(args, ", "))
+	fmt.Fprintf(&o.dts, "export declare const %sSubjectAll: %q;\n\n", tsName(e.Name), all)
+}