A held stream's size cap is raised to its manifest's when larger, never lowered (issue 1966)

The operator, 2026-11-09 09:07: raise only. The grants part's assert raises it, says it in its asserted event and the
journal with the old and new cap, and grants_assert asks it by hand.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-grants/cmd/mesh-grants/create.go

@@ -88,6 +88,28 @@ func (c creating) AddSubjects(stream string, add []string) error {
 	return err
 }
 
+// RaiseMaxBytes raises a held stream's size cap to `to` when that is larger than the cap it holds, and changes nothing
+// else: it reads the stream's configuration and updates with the rest as it was. An unbounded stream (-1) and a cap that
+// is larger or equal are left as they are.
+func (c creating) RaiseMaxBytes(stream string, to int64) (int64, bool, error) {
+	ctx, cancel := context.WithTimeout(c.ctx, requestWithin)
+	defer cancel()
+	s, err := c.js.Stream(ctx, stream)
+	if err != nil {
+		return 0, false, err
+	}
+	cfg := s.CachedInfo().Config
+	if cfg.MaxBytes <= 0 || cfg.MaxBytes >= to {
+		return cfg.MaxBytes, false, nil
+	}
+	from := cfg.MaxBytes
+	cfg.MaxBytes = to
+	if _, err := c.js.UpdateStream(ctx, cfg); err != nil {
+		return from, false, err
+	}
+	return from, true, nil
+}
+
 // AddFilters adds filter subjects to a held consumer and changes nothing else.
 func (c creating) AddFilters(stream, name string, add []string) error {
 	ctx, cancel := context.WithTimeout(c.ctx, requestWithin)

modules/mesh-grants/cmd/mesh-grants/integration_test.go

@@ -324,7 +324,7 @@ func TestTheGrantsPartWhole(t *testing.T) {
 	// ADR 0640 §5: the real additions change the subjects and the filters and nothing else, and recreate nothing.
 	t.Run("adding subjects and filters changes only those", func(t *testing.T) {
 		stream, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: "ADDS", Subjects: []string{"a.>"}, MaxAge: time.Hour, MaxMsgs: 100,
-			Retention: jetstream.LimitsPolicy, Discard: jetstream.DiscardNew})
+			Retention: jetstream.LimitsPolicy, Discard: jetstream.DiscardNew, MaxBytes: 1 << 20})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -368,6 +368,21 @@ func TestTheGrantsPartWhole(t *testing.T) {
 			cafter.Delivered.Stream != cbefore.Delivered.Stream || cafter.AckFloor.Stream != cbefore.AckFloor.Stream || !cafter.Created.Equal(cbefore.Created) {
 			t.Errorf("the consumer after: %+v delivered %d created %v, before %+v delivered %d created %v", ca, cafter.Delivered.Stream, cafter.Created, cb, cbefore.Delivered.Stream, cbefore.Created)
 		}
+		// A size cap is only ever raised, and nothing else changes with it (the operator, 2026-11-09).
+		for _, row := range []struct {
+			to, from, want int64
+			raised         bool
+		}{{4 << 20, 1 << 20, 4 << 20, true}, {2 << 20, 4 << 20, 4 << 20, false}} {
+			from, raised, err := c.RaiseMaxBytes("ADDS", row.to)
+			if err != nil {
+				t.Fatal(err)
+			}
+			now, _ := stream.Info(ctx)
+			if from != row.from || raised != row.raised || now.Config.MaxBytes != row.want || now.Config.MaxAge != b.MaxAge ||
+				!slices.Equal(now.Config.Subjects, []string{"a.>", "b.>"}) || !now.Created.Equal(before.Created) || now.State.Msgs != before.State.Msgs {
+				t.Errorf("raise to %d: from %d raised %v, config %+v", row.to, from, raised, now.Config)
+			}
+		}
 		// Nothing is removed: a second addition of the same and of a subset keeps what is there.
 		if err := c.AddSubjects("ADDS", []string{"a.>"}); err != nil {
 			t.Fatal(err)

modules/mesh-grants/cmd/mesh-grants/tools.go

@@ -192,8 +192,9 @@ func toolsOf(p *grants.Part) []stdio.Tool {
 			"the indexer's trunk with their limits, beside what the bus holds (through the bus module's nats_streams). When the " +
 			"bus lacks one, asks the part's process (which alone holds the grant) to create it now with the manifest's limits, " +
 			"as it does by itself when a manifest is registered (issue 1790), and says asserted. A stream the bus holds gains the " +
-			"subjects its manifest adds (and a consumer the filters its module's consumes adds), only ever adding: it never removes " +
-			"a subject, changes a limit or retention, deletes or recreates one; any other difference is only said. Answers the comparison and the ask; call again to see what the bus holds.",
+			"subjects its manifest adds (and a consumer the filters its module's consumes adds) and has its size cap RAISED to the " +
+			"manifest's when that is larger (said as an asserted event and in the journal, with the old and new cap), only ever adding or raising: it never removes " +
+			"a subject, lowers a cap or any other limit, changes retention, deletes or recreates one; any other difference is only said. Answers the comparison and the ask; call again to see what the bus holds.",
 			Input: schema(map[string]string{"module": "the module"}, "module"),
 			Run:   func(a map[string]any) (any, error) { return p.AssertOne(grants.Answer(a, "module")) }},
 		{Name: grants.ToolAccounts, Description: "The bus accounts the mesh wants (novox/hq ADR 0561 §2, §9): every account the vault " +

modules/mesh-grants/grants_test.go

@@ -72,9 +72,11 @@ type fakeBus struct {
 	creates []string
 	// subjectAdds and filterAdds are the additions the part asked of a held stream and a held consumer.
 	subjectAdds, filterAdds []string
-	refuseAdd               string
-	createdAge              map[string]time.Duration
-	refuseCreate            bool
+	// raises are the size caps the part raised on a held stream, as "stream from to".
+	raises       []string
+	refuseAdd    string
+	createdAge   map[string]time.Duration
+	refuseCreate bool
 	// refuseUsers refuses the bus module's nats_users: the loaded list cannot be read.
 	refuseUsers bool
 	// rootFree answers a machine's engine's root-free verb: nil is no answerer at all (no responders).
@@ -145,6 +147,26 @@ func (b *fakeBus) AddSubjects(stream string, add []string) error {
 	return errors.New("stream not found")
 }
 
+// RaiseMaxBytes is the bus's raise of a held stream's size cap: only to a larger cap, an unbounded stream and every other
+// setting kept.
+func (b *fakeBus) RaiseMaxBytes(stream string, to int64) (int64, bool, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	for _, s := range b.streams {
+		if s["name"] != stream {
+			continue
+		}
+		have, _ := s["max_bytes"].(int64)
+		if have <= 0 || have >= to {
+			return have, false, nil
+		}
+		s["max_bytes"] = to
+		b.raises = append(b.raises, fmt.Sprintf("%s %d %d", stream, have, to))
+		return have, true, nil
+	}
+	return 0, false, errors.New("stream not found")
+}
+
 // AddFilters is the bus's addition of filters to a held consumer: the union, max deliver and the rest kept.
 func (b *fakeBus) AddFilters(stream, name string, add []string) error {
 	b.mu.Lock()
@@ -583,9 +605,10 @@ func TestGrants(t *testing.T) {
 				if n := strings.Count(string(src), "CreateStream"); (path == createOnly && n != 1) || (path != createOnly && n != 0) {
 					t.Errorf("%s holds CreateStream %d times: only create.go creates, once", path, n)
 				}
-				// The one update of a stream: adding subjects to a held one, in create.go (the operator, 2026-11-05).
-				if n := strings.Count(string(src), "UpdateStream("); (path == createOnly && n != 1) || (path != createOnly && n != 0) {
-					t.Errorf("%s holds UpdateStream %d times: only create.go updates a stream, once, to add subjects", path, n)
+				// The two updates of a stream: adding subjects to a held one (the operator, 2026-11-05) and raising its size cap
+				// (2026-11-09), both in create.go.
+				if n := strings.Count(string(src), "UpdateStream("); (path == createOnly && n != 2) || (path != createOnly && n != 0) {
+					t.Errorf("%s holds UpdateStream %d times: only create.go updates a stream, twice, to add subjects and to raise a size cap", path, n)
 				}
 				// The one object bucket: the part's own, of the user list sealed to the bus node, in sealed.go (ADR 0547 clause 7).
 				if path == sealedOnly {
@@ -2044,7 +2067,7 @@ func TestGrants(t *testing.T) {
 	t.Run("assertions: a held stream gains the subjects its manifest names, and loses, changes nothing else", func(t *testing.T) {
 		b := fixture()
 		b.loaded = shadowOf(t, b)
-		b.streams = []map[string]any{{"name": "THINGS", "subjects": []string{"dropped.subject"}, "retention": "limits", "max_age_hours": 24}}
+		b.streams = []map[string]any{{"name": "THINGS", "subjects": []string{"dropped.subject"}, "retention": "limits", "max_age_hours": 24, "max_bytes": int64(1 << 20)}}
 		p := partOn(b)
 		p.Create = b
 		var logged []string
@@ -2062,6 +2085,11 @@ func TestGrants(t *testing.T) {
 				}
 			}
 		}
+		// Its size cap, smaller than the manifest's 5 MiB, is raised to it, said as an event with the old and new cap and in the journal.
+		if len(b.raises) != 1 || b.raises[0] != fmt.Sprintf("THINGS %d %d", 1<<20, 5<<20) ||
+			!strings.Contains(strings.Join(res.Asserted, " "), "raised from 1048576 to 5242880") || !strings.Contains(strings.Join(logged, " "), "raised from 1048576 to 5242880") {
+			t.Errorf("the cap was not raised or not said: %v, %v, %v", b.raises, res.Asserted, logged)
+		}
 		if again := p.Compose(); len(b.subjectAdds) != 1 || len(again.Asserted) != 0 {
 			t.Errorf("a stream that holds every subject was added to again: %v, %v", b.subjectAdds, again.Asserted)
 		}
@@ -2086,11 +2114,25 @@ func TestGrants(t *testing.T) {
 		if other := strings.Join(p.Compose().NotAsserted, " "); !strings.Contains(other, "permissions violation") {
 			t.Errorf("a refusal for another reason was not said: %q", other)
 		}
-		// A limit the manifest changed (the held max age is not the manifest's) is not touched; only subjects are ever added.
+		// A limit the manifest changed (the held max age is not the manifest's) is not touched; only subjects are ever added
+		// and a size cap raised: a held cap larger than the manifest's is never lowered, at a hand assert too.
 		b.mu.Lock()
 		b.refuseAdd = ""
+		for _, s := range b.streams {
+			if s["name"] == "THINGS" {
+				s["max_bytes"] = int64(9 << 20)
+			}
+		}
 		b.mu.Unlock()
+		if _, err := partOn(b).AssertOne("mod-x"); err != nil {
+			t.Fatal(err)
+		}
 		p.Compose()
+		for _, s := range b.streams {
+			if s["name"] == "THINGS" && (s["max_bytes"] != int64(9<<20) || len(b.raises) != 1) {
+				t.Errorf("a larger held cap was lowered: %v, %v", s, b.raises)
+			}
+		}
 		for _, s := range b.streams {
 			if s["name"] == "THINGS" && (s["max_age_hours"] != 24 || s["retention"] != "limits") {
 				t.Errorf("a limit or retention changed with the subjects: %v", s)

modules/mesh-grants/internal/buscompose/nats.go

@@ -1506,8 +1506,9 @@ const WatchmanModule = "mesh-delivery-watchman"
 // CreateStreamGrants is what creating each named stream needs, and nothing wider (novox/hq ADR 0547 §5; the operator,
 // 2026-10-26 08:54): its create, and its information to read back what it holds. Each by its own name: a name that
 // is not one plain subject token is left out, since a wildcard there would be every stream. Its update is granted for the one
-// act the part does on a held stream: adding the subjects a manifest's new events need (grants.Creator.AddSubjects); it
-// never removes a subject, changes a limit or recreates the stream, and never deletes or purges one.
+// acts the part does on a held stream: adding the subjects a manifest's new events need (grants.Creator.AddSubjects) and
+// raising its size cap to the manifest's when larger (grants.Creator.RaiseMaxBytes; the operator, 2026-11-09); it never
+// removes a subject, lowers a limit or recreates the stream, and never deletes or purges one.
 func CreateStreamGrants(streams []string) []string {
 	var out []string
 	for _, s := range streams {

modules/mesh-grants/internal/grants/assertions.go

@@ -54,7 +54,8 @@ const ShadowAsserts = "in the tools: composed and compared, nothing asserted (th
 
 // CreatesMissing is what an assertion of the part's process says (the operator, 2026-10-26 08:54; issue 1790).
 const CreatesMissing = "a bucket, log or stream the manifest declares and the bus lacks is created with the manifest's limits, once per " +
-	"manifest; a stream the bus holds only ever gains the subjects its manifest adds, and nothing is removed, deleted or otherwise changed, a difference is only said"
+	"manifest; a stream the bus holds only ever gains the subjects its manifest adds and has its size cap raised to the manifest's when that is larger " +
+	"(never lowered), and nothing is removed, deleted or otherwise changed, a difference is only said"
 
 // Creator creates one stream the bus does not hold, with the configuration given, and never updates or deletes one: the
 // part's process alone, whose account is granted the create of each declared stream by name (the operator, 2026-10-26
@@ -64,6 +65,17 @@ type Creator interface {
 	// AddSubjects adds subjects to a stream the bus holds and nothing else: the stream's subjects become the union of what
 	// it holds and add; no subject is removed, no limit, retention or other setting changed, the stream not recreated.
 	AddSubjects(stream string, add []string) error
+	// RaiseMaxBytes raises the size cap of a stream the bus holds to `to` when `to` is larger than the cap it holds, and
+	// changes nothing else (the operator, 2026-11-09 09:07: "raise only"). It answers the cap it held and whether it
+	// raised; a cap that is larger or equal, or an unbounded stream, is left as it is. It never lowers any limit.
+	RaiseMaxBytes(stream string, to int64) (from int64, raised bool, err error)
+}
+
+// Raise is one held stream's size cap raised to the manifest's, said in the event and the journal.
+type Raise struct {
+	Stream string `json:"stream"`
+	From   int64  `json:"from"`
+	To     int64  `json:"to"`
 }
 
 // ErrHeld is a create refused because the bus holds the stream already (made meanwhile): left as it is.
@@ -103,6 +115,9 @@ func Configs(m catalogue.Manifest, nodes []string) map[string]jetstream.StreamCo
 type creations struct {
 	mu   sync.Mutex
 	made map[string]string
+	// raised is, by stream, the manifest digest at which its size cap was last compared with the manifest's, so the bus is
+	// asked for it once per manifest (a hand assert asks again).
+	raised map[string]string
 	// refused is, by stream, the refusal of the last addition of subjects (an overlap with another stream, say), so a
 	// refusal that stands is said once and not at every pass; a success or a different refusal says again.
 	refused map[string]string
@@ -132,6 +147,21 @@ func (c *creations) madeAt(stream string) string {
 	return c.made[stream]
 }
 
+func (c *creations) raisedAt(stream string) string {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.raised[stream]
+}
+
+func (c *creations) keepRaised(stream, digest string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.raised == nil {
+		c.raised = map[string]string{}
+	}
+	c.raised[stream] = digest
+}
+
 func (c *creations) keep(stream, digest string) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -143,8 +173,8 @@ func (c *creations) keep(stream, digest string) {
 
 // createMissing creates each item of a the bus lacks, with the manifest's limits, and says what became of it. It never
 // touches an item the bus holds, and does nothing when what the bus holds was not read. force asks again a stream
-// created at this manifest and gone since (a hand assert). It answers the streams created.
-func createMissing(c Creator, done *creations, a *Assertion, m catalogue.Manifest, nodes []string, force bool) []string {
+// created at this manifest and gone since (a hand assert). It answers the streams created and the size caps raised.
+func createMissing(c Creator, done *creations, a *Assertion, m catalogue.Manifest, nodes []string, force bool) ([]string, []Raise) {
 	cfgs := Configs(m, nodes)
 	var made []string
 	a.Says = CreatesMissing
@@ -202,10 +232,30 @@ func createMissing(c Creator, done *creations, a *Assertion, m catalogue.Manifes
 		it.Created = "subjects added: " + strings.Join(add, ", ")
 		made = append(made, "stream "+it.Stream+" gained "+strings.Join(add, ", "))
 	}
+	// A held stream, of any kind, whose manifest declares a larger size cap gets that cap, and no other limit changes: a
+	// cap the bus holds that is larger or equal stays (the operator, 2026-11-09 09:07). Compared once per manifest.
+	var raises []Raise
+	for i := range a.Items {
+		it := &a.Items[i]
+		if it.Held == nil || it.Composed.MaxBytes <= 0 || (!force && done.raisedAt(it.Stream) == a.Manifest) {
+			continue
+		}
+		from, raised, err := c.RaiseMaxBytes(it.Stream, it.Composed.MaxBytes)
+		if err != nil {
+			it.Created = ItemNotCreated + "size cap not raised: " + err.Error() + " (tried again at the next event)"
+			continue
+		}
+		done.keepRaised(it.Stream, a.Manifest)
+		if raised {
+			it.Created = fmt.Sprintf("size cap raised from %d to %d bytes", from, it.Composed.MaxBytes)
+			raises = append(raises, Raise{Stream: it.Stream, From: from, To: it.Composed.MaxBytes})
+			made = append(made, fmt.Sprintf("%s %s size cap raised from %d to %d bytes", it.Kind, it.Stream, from, it.Composed.MaxBytes))
+		}
+	}
 	if len(made) > 0 {
 		a.Asserted = true
 	}
-	return made
+	return made, raises
 }
 
 // notCreated is each item of a creation refused, with why, as `<stream>: <why>`.

modules/mesh-grants/internal/grants/part.go

@@ -503,12 +503,12 @@ func (p *Part) Compose() Result {
 		a := Assert(module, in.Digests[module], in.Manifests[module], in.Nodes, held, heldErr)
 		// Created only where the bus was read and lacks it, never changed where it holds it (issue 1790).
 		if p.Create != nil && heldErr == nil {
-			if made := createMissing(p.Create, &p.made, &a, in.Manifests[module], in.Nodes, forced == module); len(made) > 0 {
+			if made, raises := createMissing(p.Create, &p.made, &a, in.Manifests[module], in.Nodes, forced == module); len(made) > 0 {
 				res.Asserted = append(res.Asserted, fmt.Sprintf("%s at %s: created %s", module, a.Manifest, strings.Join(made, ", ")))
 				if p.Logf != nil {
 					p.Logf("%s at %s: asserted on the bus: %s", module, a.Manifest, strings.Join(made, ", "))
 				}
-				p.say(&res, EventAsserted, map[string]any{"module": module, "manifest": a.Manifest, "created": made})
+				p.say(&res, EventAsserted, map[string]any{"module": module, "manifest": a.Manifest, "created": made, "raised": raises})
 			}
 			for _, why := range notCreated(a) {
 				res.NotAsserted = append(res.NotAsserted, module+" "+why)

modules/mesh-grants/internal/grants/tools.go

@@ -258,8 +258,8 @@ func (p *Part) UserList() (any, error) {
 
 // AssertOne answers the tool assert: one module's buckets, logs and streams as composed from its manifest at the
 // indexer's trunk, beside what the bus holds, and asks the part's process (which alone holds the grant to create) to
-// create what the bus lacks now, even one it created at this manifest and that is gone since (issue 1790). It changes no
-// stream the bus holds. Here, in the tools, it creates nothing itself: the answer names the ask.
+// create what the bus lacks now, even one it created at this manifest and that is gone since (issue 1790), and to raise a
+// held stream's size cap to the manifest's where that is larger (the operator, 2026-11-09). It lowers no limit. Here, in the tools, it creates nothing itself: the answer names the ask.
 func (p *Part) AssertOne(module string) (any, error) {
 	if module == "" {
 		return nil, errors.New("assert names a module")
@@ -292,16 +292,17 @@ func (p *Part) AssertOne(module string) (any, error) {
 			missing++
 		}
 	}
-	if missing == 0 {
-		out["says"] = "the bus holds every bucket, log and stream the manifest declares: nothing to create; a held stream only ever gains the subjects a manifest adds, any other difference is only said"
-		return out, nil
-	}
 	ask, _ := json.Marshal(Ask{By: "grants_assert", At: p.now(), Assert: module})
 	rev, err := p.Store.Put(StateUserList, KeyAsked, ask)
 	if err != nil {
 		return nil, fmt.Errorf("the ask to create could not be written: %w", err)
 	}
 	out["asked"] = rev
+	if missing == 0 {
+		out["says"] = "the bus holds every bucket, log and stream the manifest declares: nothing to create; asked the part's process to raise " +
+			"a held stream's size cap to the manifest's where that is larger (never lower), and to add the subjects a manifest adds; any other difference is only said"
+		return out, nil
+	}
 	out["says"] = fmt.Sprintf("%d the bus lacks: the part's process creates them at this ask if %s is placed (its grant names only placed "+
 		"modules' streams) and says asserted; grants_assert again shows what the bus holds then", missing, module)
 	return out, nil