feat: optional per-room JetStream persistence (history + offline replay), gated by RoomPolicy.Persist

app.md

@@ -17,7 +17,7 @@ uses_types: []
 framework: ""
 entry_point: "cmd/membershipd"
 dir_path: "projects/message_bus/apps/unibus"
-repo_url: ""
+repo_url: "https://gitea-dgg044oo04woo4ggcsws4gk0.organic-machine.com/dataforge/unibus"
 service:
   port: 8470
   health_endpoint: /healthz

go.mod

@@ -25,6 +25,7 @@ require (
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	golang.org/x/crypto v0.51.0 // indirect
 	golang.org/x/sys v0.44.0 // indirect
+	golang.org/x/text v0.37.0 // indirect
 	golang.org/x/time v0.7.0 // indirect
 	modernc.org/libc v1.70.0 // indirect
 	modernc.org/mathutil v1.7.1 // indirect

go.sum

@@ -39,6 +39,8 @@ golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
 golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/text v0.37.0 h1:Cqjiwd9eSg8e0QAkyCaQTNHFIIzWtidPahFWR83rTrc=
+golang.org/x/text v0.37.0/go.mod h1:a5sjxXGs9hsn/AJVwuElvCAo9v8QYLzvavO5z2PiM38=
 golang.org/x/time v0.7.0 h1:ntUhktv3OPE6TgYxXWv9vKvUSJyIFJlyohwbkEwPrKQ=
 golang.org/x/time v0.7.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
 golang.org/x/tools v0.45.0 h1:18qN3FAooORvApf5XjCXgsuayZOEtXf6JK18I3+ONa8=

pkg/client/client.go

@@ -14,6 +14,7 @@ package client
 
 import (
 	"bytes"
+	"context"
 	"crypto/rand"
 	"encoding/json"
 	"fmt"
@@ -27,6 +28,7 @@ import (
 	"github.com/enmanuel/unibus/pkg/frame"
 	"github.com/enmanuel/unibus/pkg/room"
 	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
 )
 
 // Endpoint is the public identity of a peer.
@@ -41,6 +43,7 @@ type Client struct {
 	id       cs.Identity
 	endpoint string
 	nc       *nats.Conn
+	js       jetstream.JetStream // durable plane for rooms with Policy.Persist
 	ctrlURL  string
 	http     *http.Client
 
@@ -56,10 +59,19 @@ func New(natsURL, ctrlURL string, id cs.Identity) (*Client, error) {
 	if err != nil {
 		return nil, fmt.Errorf("client: connect nats %q: %w", natsURL, err)
 	}
+	// JetStream context for the durable plane. Obtaining it does not require any
+	// stream to exist yet and has no effect on cleartext/ephemeral rooms — those
+	// keep using core nc.Publish / nc.Subscribe untouched.
+	js, err := jetstream.New(nc)
+	if err != nil {
+		nc.Close()
+		return nil, fmt.Errorf("client: init jetstream: %w", err)
+	}
 	return &Client{
 		id:        id,
 		endpoint:  frame.EndpointID(id.SignPub),
 		nc:        nc,
+		js:        js,
 		ctrlURL:   ctrlURL,
 		http:      &http.Client{Timeout: 10 * time.Second},
 		keyCache:  map[string]map[int][]byte{},
@@ -257,6 +269,15 @@ func (c *Client) CreateRoom(subject string, p room.Policy) (string, error) {
 	if p.Encrypt {
 		c.cacheKey(resp.RoomID, 1, k)
 	}
+	// For persisted rooms, provision the durable JetStream stream up front so the
+	// first publish (even before any subscriber exists) is captured for history.
+	if p.Persist {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := c.ensureStream(ctx, resp.RoomID, subject); err != nil {
+			return "", err
+		}
+	}
 	return resp.RoomID, nil
 }
 
@@ -406,20 +427,82 @@ func (c *Client) Publish(roomID string, plaintext []byte) error {
 	if err != nil {
 		return fmt.Errorf("client: marshal frame: %w", err)
 	}
+	// Persisted rooms go through JetStream (durable, acked); ephemeral rooms keep
+	// the exact core-NATS publish they had before.
+	if info.Policy.Persist {
+		return c.publishPersistent(roomID, info.Subject, b)
+	}
 	return c.nc.Publish(info.Subject, b)
 }
 
+// Sub is a transport-agnostic handle to an active room subscription. It wraps
+// either a core NATS subscription (ephemeral rooms) or a JetStream durable
+// consumer (persisted rooms) behind a single Unsubscribe() method, so callers
+// (and tests) treat both planes uniformly. For a persisted room, Unsubscribe
+// stops local delivery but leaves the durable consumer's ack position on the
+// server, so a later Subscribe with the same peer resumes (offline replay).
+type Sub struct {
+	nsub *nats.Subscription
+	cc   jetstream.ConsumeContext
+}
+
+// Unsubscribe stops delivery for this subscription. The error return keeps the
+// signature compatible with *nats.Subscription's Unsubscribe.
+func (s *Sub) Unsubscribe() error {
+	if s == nil {
+		return nil
+	}
+	if s.nsub != nil {
+		return s.nsub.Unsubscribe()
+	}
+	if s.cc != nil {
+		s.cc.Stop()
+	}
+	return nil
+}
+
 // Subscribe subscribes to a room and invokes handler for each message with the
 // decoded frame and (for encrypted rooms) the decrypted plaintext. Signature
 // verification and epoch-driven key refresh happen transparently. Messages that
 // fail verification or decryption are dropped (handler not called).
-func (c *Client) Subscribe(roomID string, handler func(f frame.Frame, plaintext []byte)) (*nats.Subscription, error) {
+//
+// For ephemeral rooms (Policy.Persist == false) this is a plain core-NATS
+// subscription, identical to before. For persisted rooms it binds a per-peer
+// durable JetStream consumer with DeliverAll, so a late joiner receives the
+// full history (scrollback) and a reconnecting peer resumes from its last ack
+// (offline replay). The frame-decode / verify / decrypt logic is shared between
+// both planes via processFrame.
+func (c *Client) Subscribe(roomID string, handler func(f frame.Frame, plaintext []byte)) (*Sub, error) {
 	info, err := c.fetchRoom(roomID)
 	if err != nil {
 		return nil, err
 	}
-	return c.nc.Subscribe(info.Subject, func(msg *nats.Msg) {
+	deliver := func(data []byte) {
-		f, err := frame.Unmarshal(msg.Data)
+		c.processFrame(roomID, info, data, handler)
+	}
+	if info.Policy.Persist {
+		cc, err := c.subscribePersistent(roomID, info.Subject, deliver)
+		if err != nil {
+			return nil, err
+		}
+		return &Sub{cc: cc}, nil
+	}
+	nsub, err := c.nc.Subscribe(info.Subject, func(msg *nats.Msg) {
+		deliver(msg.Data)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &Sub{nsub: nsub}, nil
+}
+
+// processFrame decodes one wire message, verifies its signature and (for
+// encrypted rooms) decrypts its inline payload, then invokes handler. Messages
+// that fail verification or decryption are dropped (handler not called). This
+// is the single code path shared by the ephemeral and persisted subscribe
+// planes so their decode/verify/decrypt semantics never drift apart.
+func (c *Client) processFrame(roomID string, info roomView, data []byte, handler func(f frame.Frame, plaintext []byte)) {
+	f, err := frame.Unmarshal(data)
 	if err != nil {
 		return
 	}
@@ -440,17 +523,21 @@ func (c *Client) Subscribe(roomID string, handler func(f frame.Frame, plaintext
 			// Sender used a newer (or unknown) epoch: refresh K from the control plane.
 			k, _, err = c.fetchKey(roomID, f.Epoch)
 			if err != nil {
-					return // cannot obtain key for this epoch (e.g. we were kicked): drop
+				// Cannot obtain the key for this epoch. For persisted history this is
+				// expected and NOT fatal: a member invited at a later epoch reading
+				// older history (or a kicked peer) simply cannot read those frames.
+				// Skip this message and keep processing the rest (megolm semantics:
+				// new members do not read prior history).
+				return
 			}
 		}
 		pt, err := cs.OpenAEAD(k, f.Nonce, f.Payload, []byte(info.Subject))
 		if err != nil {
-				return // cannot decrypt (wrong epoch/kicked): drop
+			return // cannot decrypt (wrong epoch/kicked): skip this frame, continue
 		}
 		plaintext = pt
 	}
 	handler(f, plaintext)
-	})
 }
 
 // ---- request/reply (cleartext v1) ----------------------------------------
@@ -570,6 +657,12 @@ func (c *Client) PublishMedia(roomID string, data []byte) error {
 	if err != nil {
 		return fmt.Errorf("client: marshal media frame: %w", err)
 	}
+	// Persisted rooms route the media frame (the BlobRef envelope, not the blob
+	// bytes) through JetStream so it appears in history/replay like any other
+	// frame; ephemeral rooms keep the original core-NATS publish.
+	if info.Policy.Persist {
+		return c.publishPersistent(roomID, info.Subject, b)
+	}
 	return c.nc.Publish(info.Subject, b)
 }
 

pkg/client/persist.go

@@ -0,0 +1,134 @@
+// This file adds optional per-room durable persistence on top of the core
+// (ephemeral) NATS data plane. Persistence is gated entirely by the per-room
+// RoomPolicy.Persist flag:
+//
+//   - Persist == false (room.ModeNATS): nothing here runs. Publish/Subscribe
+//     use plain core NATS exactly as before — fast, fan-out, no history.
+//   - Persist == true (room.ModeMatrix): the room's subject is captured by a
+//     durable JetStream stream. Late joiners receive the full backlog
+//     (scrollback) and a peer that was offline resumes from its last ack
+//     (replay). The Frame, the encryption and the signature are identical to
+//     the ephemeral path; only the transport changes.
+//
+// We use the modern github.com/nats-io/nats.go/jetstream API throughout (not
+// the legacy nc.JetStream() context), and we are consistent about it across
+// the whole client.
+package client
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+// streamName derives a JetStream stream name from a room id. JetStream stream
+// (and durable consumer) names cannot contain '.', '*', '>', path separators
+// or whitespace, so we sanitize any char outside [A-Za-z0-9_] to '_' and prefix
+// with "UNIBUS_" to namespace the bus's streams.
+func streamName(roomID string) string {
+	return "UNIBUS_" + sanitizeJSName(roomID)
+}
+
+// sanitizeJSName replaces every rune outside [A-Za-z0-9_] with '_' so the
+// result is a legal JetStream stream/consumer name token.
+func sanitizeJSName(s string) string {
+	var b strings.Builder
+	b.Grow(len(s))
+	for _, r := range s {
+		switch {
+		case r >= 'a' && r <= 'z', r >= 'A' && r <= 'Z', r >= '0' && r <= '9', r == '_':
+			b.WriteRune(r)
+		default:
+			b.WriteRune('_')
+		}
+	}
+	return b.String()
+}
+
+// durableName derives a per-peer durable consumer name for a room. The same
+// (roomID, endpointID) pair always maps to the same durable, so a peer that
+// reconnects continues from its last acked message → replay of what it missed.
+func durableName(roomID, endpointID string) string {
+	return sanitizeJSName(roomID) + "_" + sanitizeJSName(endpointID)
+}
+
+// ensureStream idempotently creates (or no-ops on) a file-backed JetStream
+// stream that captures the given subject for a persisted room. It is safe to
+// call repeatedly: CreateOrUpdateStream returns the existing stream unchanged
+// when the config matches. Called from CreateRoom(Persist), and defensively
+// from the first Publish/Subscribe to a persisted room.
+func (c *Client) ensureStream(ctx context.Context, roomID, subject string) error {
+	if c.js == nil {
+		return errors.New("client: JetStream not initialized")
+	}
+	cfg := jetstream.StreamConfig{
+		Name:      streamName(roomID),
+		Subjects:  []string{subject},
+		Retention: jetstream.LimitsPolicy,
+		Storage:   jetstream.FileStorage,
+	}
+	if _, err := c.js.CreateOrUpdateStream(ctx, cfg); err != nil {
+		return fmt.Errorf("client: ensure stream for room %s: %w", roomID, err)
+	}
+	return nil
+}
+
+// publishPersistent publishes a frame to a persisted room via JetStream and
+// waits for the server ack, guaranteeing the message is durably stored before
+// returning. The stream is ensured first so the very first publish to a freshly
+// created room (or after a restart) cannot be lost for lack of a stream.
+func (c *Client) publishPersistent(roomID, subject string, frameBytes []byte) error {
+	if c.js == nil {
+		return errors.New("client: JetStream not initialized")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if err := c.ensureStream(ctx, roomID, subject); err != nil {
+		return err
+	}
+	if _, err := c.js.Publish(ctx, subject, frameBytes); err != nil {
+		return fmt.Errorf("client: jetstream publish to room %s: %w", roomID, err)
+	}
+	return nil
+}
+
+// subscribePersistent binds a per-peer durable consumer to the room's stream
+// with DeliverAll + explicit ack. DeliverAll delivers the full backlog
+// (scrollback) on first bind and then live messages; the durable name makes a
+// reconnecting peer resume from its last ack (offline replay). Each delivered
+// message is acked only after the supplied onMsg callback has processed it.
+func (c *Client) subscribePersistent(roomID, subject string, onMsg func(data []byte)) (jetstream.ConsumeContext, error) {
+	if c.js == nil {
+		return nil, errors.New("client: JetStream not initialized")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := c.ensureStream(ctx, roomID, subject); err != nil {
+		return nil, err
+	}
+	stream, err := c.js.Stream(ctx, streamName(roomID))
+	if err != nil {
+		return nil, fmt.Errorf("client: lookup stream for room %s: %w", roomID, err)
+	}
+	cons, err := stream.CreateOrUpdateConsumer(ctx, jetstream.ConsumerConfig{
+		Durable:       durableName(roomID, c.endpoint),
+		DeliverPolicy: jetstream.DeliverAllPolicy,
+		AckPolicy:     jetstream.AckExplicitPolicy,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("client: ensure durable consumer for room %s: %w", roomID, err)
+	}
+	cc, err := cons.Consume(func(msg jetstream.Msg) {
+		onMsg(msg.Data())
+		_ = msg.Ack()
+	})
+	if err != nil {
+		return nil, fmt.Errorf("client: consume room %s: %w", roomID, err)
+	}
+	return cc, nil
+}

pkg/client/persist_test.go

@@ -0,0 +1,296 @@
+package client_test
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/enmanuel/unibus/pkg/client"
+	"github.com/enmanuel/unibus/pkg/frame"
+	"github.com/enmanuel/unibus/pkg/room"
+)
+
+// modePersistPlain is a persisted-but-unencrypted policy: durable JetStream
+// history, cleartext payloads, no signatures. It exercises the persistence path
+// in isolation from the crypto path.
+var modePersistPlain = room.Policy{Encrypt: false, Persist: true, SignMsgs: false}
+
+// containsAll reports whether every want string appears in got.
+func containsAll(got, want []string) bool {
+	for _, w := range want {
+		found := false
+		for _, g := range got {
+			if g == w {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
+}
+
+// containsAny reports whether any want string appears in got.
+func containsAny(got, want []string) bool {
+	for _, w := range want {
+		for _, g := range got {
+			if g == w {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// TestPersistScrollback: a persisted room delivers prior messages (history) to a
+// peer that subscribes AFTER those messages were published. A publishes 3 before
+// B subscribes; B must receive all 3.
+func TestPersistScrollback(t *testing.T) {
+	h := newHarness(t)
+	waitHealth(t, h.ctrlURL)
+
+	a, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect A: %v", err)
+	}
+	defer a.Close()
+	b, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect B: %v", err)
+	}
+	defer b.Close()
+
+	roomID, err := a.CreateRoom("room.persist", modePersistPlain)
+	if err != nil {
+		t.Fatalf("A create persisted room: %v", err)
+	}
+
+	want := []string{"hist-1", "hist-2", "hist-3"}
+	for _, m := range want {
+		if err := a.Publish(roomID, []byte(m)); err != nil {
+			t.Fatalf("A publish %q: %v", m, err)
+		}
+	}
+
+	// B subscribes only AFTER the 3 messages were published.
+	col := subscribeCollect(t, b, roomID)
+	defer col.sub.Unsubscribe()
+
+	if !waitFor(&col.mu, &col.msgs, func(rs []string) bool {
+		return containsAll(rs, want)
+	}, 5*time.Second) {
+		t.Fatalf("B did not receive full scrollback; want %v got %v", want, snapshot(&col.mu, &col.msgs))
+	}
+}
+
+// TestEphemeralNoScrollback: an ephemeral (Persist=false) room delivers NO prior
+// messages to a late subscriber. A publishes 3; B subscribes after and must see
+// none of them. This guards that the Persist=false path stays plain core NATS.
+func TestEphemeralNoScrollback(t *testing.T) {
+	h := newHarness(t)
+	waitHealth(t, h.ctrlURL)
+
+	a, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect A: %v", err)
+	}
+	defer a.Close()
+	b, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect B: %v", err)
+	}
+	defer b.Close()
+
+	roomID, err := a.CreateRoom("proc.ephemeral.ticks", room.ModeNATS)
+	if err != nil {
+		t.Fatalf("A create ephemeral room: %v", err)
+	}
+
+	prior := []string{"eph-1", "eph-2", "eph-3"}
+	for _, m := range prior {
+		if err := a.Publish(roomID, []byte(m)); err != nil {
+			t.Fatalf("A publish %q: %v", m, err)
+		}
+	}
+	// Let any (incorrect) delivery settle.
+	time.Sleep(200 * time.Millisecond)
+
+	col := subscribeCollect(t, b, roomID)
+	defer col.sub.Unsubscribe()
+	time.Sleep(150 * time.Millisecond)
+
+	// A live message AFTER subscribe proves the subscription works at all.
+	const live = "eph-live"
+	if err := a.Publish(roomID, []byte(live)); err != nil {
+		t.Fatalf("A publish live: %v", err)
+	}
+	if !waitFor(&col.mu, &col.msgs, func(rs []string) bool {
+		return containsAny(rs, []string{live})
+	}, 2*time.Second) {
+		t.Fatalf("B did not receive live message on ephemeral room; got %v", snapshot(&col.mu, &col.msgs))
+	}
+
+	// None of the prior messages must have been replayed.
+	if got := snapshot(&col.mu, &col.msgs); containsAny(got, prior) {
+		t.Fatalf("ephemeral room replayed history (should be impossible); got %v", got)
+	}
+}
+
+// TestOfflineReplay: a peer that goes offline (Unsubscribe) and reconnects with
+// the same durable resumes from its last ack — it receives messages published
+// while it was offline. B subscribes, unsubscribes, A publishes 2, B re-subscribes
+// with the SAME identity (same durable) and must receive both missed messages.
+func TestOfflineReplay(t *testing.T) {
+	h := newHarness(t)
+	waitHealth(t, h.ctrlURL)
+
+	a, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect A: %v", err)
+	}
+	defer a.Close()
+
+	bID := mustIdentity(t)
+	b, err := client.New(h.natsURL, h.ctrlURL, bID)
+	if err != nil {
+		t.Fatalf("connect B: %v", err)
+	}
+	defer b.Close()
+
+	roomID, err := a.CreateRoom("room.replay", modePersistPlain)
+	if err != nil {
+		t.Fatalf("A create persisted room: %v", err)
+	}
+
+	// B comes online once (establishes its durable), receives the first message,
+	// then goes offline.
+	col1 := subscribeCollect(t, b, roomID)
+	const first = "before-offline"
+	if err := a.Publish(roomID, []byte(first)); err != nil {
+		t.Fatalf("A publish first: %v", err)
+	}
+	if !waitFor(&col1.mu, &col1.msgs, func(rs []string) bool {
+		return containsAny(rs, []string{first})
+	}, 5*time.Second) {
+		t.Fatalf("B did not receive first message before going offline; got %v", snapshot(&col1.mu, &col1.msgs))
+	}
+	// B goes offline: stop local delivery but keep the durable's ack position.
+	if err := col1.sub.Unsubscribe(); err != nil {
+		t.Fatalf("B unsubscribe: %v", err)
+	}
+	time.Sleep(150 * time.Millisecond)
+
+	// While B is offline, A publishes 2 more.
+	missed := []string{"missed-1", "missed-2"}
+	for _, m := range missed {
+		if err := a.Publish(roomID, []byte(m)); err != nil {
+			t.Fatalf("A publish %q: %v", m, err)
+		}
+	}
+
+	// B reconnects with the SAME identity → same durable name → resumes from its
+	// last ack and replays exactly the two messages it missed.
+	col2 := subscribeCollect(t, b, roomID)
+	defer col2.sub.Unsubscribe()
+	if !waitFor(&col2.mu, &col2.msgs, func(rs []string) bool {
+		return containsAll(rs, missed)
+	}, 5*time.Second) {
+		t.Fatalf("B did not replay missed messages on reconnect; want %v got %v", missed, snapshot(&col2.mu, &col2.msgs))
+	}
+}
+
+// TestPersistEncryptedNoPanic: a persisted + encrypted room with an epoch change.
+// A publishes at epoch 1, kicks B (rotating to epoch 2), publishes at epoch 2.
+// A freshly invited peer C (which only holds epoch-2 K) reads the full history:
+// it must NOT panic on the epoch-1 frame it cannot decrypt, and must only surface
+// the epoch-2 message it can decrypt (megolm: new members do not read prior
+// history). This exercises both the OpenAEAD-fails-skip path and empty/foreign
+// frames during scrollback without crashing.
+func TestPersistEncryptedNoPanic(t *testing.T) {
+	h := newHarness(t)
+	waitHealth(t, h.ctrlURL)
+
+	a, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect A: %v", err)
+	}
+	defer a.Close()
+	b, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect B: %v", err)
+	}
+	defer b.Close()
+	c, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect C: %v", err)
+	}
+	defer c.Close()
+
+	// ModeMatrix is encrypted + persisted + signed.
+	roomID, err := a.CreateRoom("room.secret", room.ModeMatrix)
+	if err != nil {
+		t.Fatalf("A create encrypted persisted room: %v", err)
+	}
+	if err := a.Invite(roomID, b.Endpoint()); err != nil {
+		t.Fatalf("A invite B: %v", err)
+	}
+	if err := b.Join(roomID); err != nil {
+		t.Fatalf("B join: %v", err)
+	}
+
+	const epoch1Msg = "epoch1-secret"
+	if err := a.Publish(roomID, []byte(epoch1Msg)); err != nil {
+		t.Fatalf("A publish epoch1: %v", err)
+	}
+
+	// Kick B → key rotates to epoch 2.
+	if err := a.Kick(roomID, b.Endpoint().ID); err != nil {
+		t.Fatalf("A kick B: %v", err)
+	}
+	time.Sleep(150 * time.Millisecond)
+
+	const epoch2Msg = "epoch2-secret"
+	if err := a.Publish(roomID, []byte(epoch2Msg)); err != nil {
+		t.Fatalf("A publish epoch2: %v", err)
+	}
+
+	// C is invited only at the current (epoch 2) key, so it CANNOT decrypt the
+	// epoch-1 history frame but CAN decrypt the epoch-2 one.
+	if err := a.Invite(roomID, c.Endpoint()); err != nil {
+		t.Fatalf("A invite C: %v", err)
+	}
+	if err := c.Join(roomID); err != nil {
+		t.Fatalf("C join: %v", err)
+	}
+
+	var mu sync.Mutex
+	var seen []string
+	// The handler must never be invoked with undecryptable garbage, and the
+	// subscribe path must never panic while scrolling through history that mixes
+	// epoch-1 (foreign) and epoch-2 (readable) frames.
+	sub, err := c.Subscribe(roomID, func(f frame.Frame, plaintext []byte) {
+		mu.Lock()
+		seen = append(seen, string(plaintext))
+		mu.Unlock()
+	})
+	if err != nil {
+		t.Fatalf("C subscribe: %v", err)
+	}
+	defer sub.Unsubscribe()
+
+	// C should surface the epoch-2 message from history (it holds K2).
+	if !waitFor(&mu, &seen, func(rs []string) bool {
+		return containsAny(rs, []string{epoch2Msg})
+	}, 5*time.Second) {
+		t.Fatalf("C did not decrypt epoch-2 history message; got %v", snapshot(&mu, &seen))
+	}
+
+	// Give scrollback time to fully drain, then assert C never saw the epoch-1
+	// secret (it lacks K1) and that no crash occurred (we got here).
+	time.Sleep(500 * time.Millisecond)
+	if got := snapshot(&mu, &seen); containsAny(got, []string{epoch1Msg}) {
+		t.Fatalf("forward secrecy broken in history: C read epoch-1 secret without K1; got %v", got)
+	}
+}

playground/index.html

@@ -166,6 +166,13 @@
         <input id="roomEncrypt" type="checkbox" />
         <label for="roomEncrypt">&#128274; encrypted (E2E)</label>
       </div>
+      <div class="checkrow">
+        <input id="roomPersist" type="checkbox" />
+        <label for="roomPersist">&#128450; persistente (historial)</label>
+      </div>
+      <div class="help" style="margin:-4px 0 8px; font-size:12px; color:var(--muted)">
+        persistente = quien se une despues ve el historial; sin persistir = solo mensajes nuevos (NATS simple).
+      </div>
       <button id="createRoomBtn" disabled>Create room</button>
       <div style="border-top:1px solid var(--border); margin:12px 0"></div>
       <label>Join by room_id</label>
@@ -370,16 +377,17 @@ $("connectBtn").onclick = async () => {
 $("createRoomBtn").onclick = async () => {
   const subject = $("roomSubject").value.trim();
   const encrypt = $("roomEncrypt").checked;
+  const persist = $("roomPersist").checked;
   if (!subject) { setStatus("roomStatus", "subject required", "bad"); return; }
   try {
-    const res = await api("/api/room", { peer: state.peer, subject, encrypt });
+    const res = await api("/api/room", { peer: state.peer, subject, encrypt, persist });
     state.rooms[res.room_id] = { subject: res.subject, encrypt: res.encrypt };
     refreshRoomSelect();
     $("activeRoom").value = res.room_id;
     setStatus("roomStatus", "created " + res.room_id + " (click to copy)", "ok");
     $("roomStatus").style.cursor = "pointer";
     $("roomStatus").onclick = () => navigator.clipboard.writeText(res.room_id);
-    logSys("created room " + res.subject + " [" + short(res.room_id) + "]" + (encrypt ? " 🔒" : ""));
+    logSys("created room " + res.subject + " [" + short(res.room_id) + "]" + (encrypt ? " 🔒" : "") + (res.persist ? " 🗄" : ""));
   } catch (e) {
     setStatus("roomStatus", e.message, "bad");
   }

playground/server.go

@@ -34,8 +34,6 @@ import (
 
 	_ "embed"
 
-	"github.com/nats-io/nats.go"
-
 	"github.com/enmanuel/unibus/pkg/blobstore"
 	"github.com/enmanuel/unibus/pkg/client"
 	"github.com/enmanuel/unibus/pkg/embeddednats"
@@ -86,7 +84,7 @@ type peerState struct {
 	endpoint client.Endpoint
 
 	mu        sync.Mutex
-	subs      map[string]*nats.Subscription // roomID -> subscription
+	subs      map[string]*client.Sub  // roomID -> subscription
 	rooms     map[string]roomInfo     // roomID -> subject/encrypt
 	listeners map[chan Event]struct{} // attached SSE channels
 }
@@ -155,7 +153,7 @@ func (h *Hub) getOrCreate(name string) (*peerState, error) {
 		name:      name,
 		client:    c,
 		endpoint:  c.Endpoint(),
-		subs:      map[string]*nats.Subscription{},
+		subs:      map[string]*client.Sub{},
 		rooms:     map[string]roomInfo{},
 		listeners: map[chan Event]struct{}{},
 	}
@@ -311,6 +309,7 @@ func (h *Hub) handleRoom(w http.ResponseWriter, r *http.Request) {
 		Peer    string `json:"peer"`
 		Subject string `json:"subject"`
 		Encrypt bool   `json:"encrypt"`
+		Persist bool   `json:"persist"`
 	}
 	if err := decodeBody(r, &req); err != nil || req.Peer == "" || req.Subject == "" {
 		writeErr(w, http.StatusBadRequest, "peer and subject required")
@@ -321,10 +320,10 @@ func (h *Hub) handleRoom(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, http.StatusBadRequest, "unknown peer "+req.Peer)
 		return
 	}
-	policy := room.ModeNATS
+	// The two checkboxes map to an explicit per-room policy. encrypt drives both
-	if req.Encrypt {
+	// encryption and per-message signing; persist (default false) independently
-		policy = room.ModeMatrix
+	// toggles durable JetStream history. persist=false keeps plain ephemeral NATS.
-	}
+	policy := room.Policy{Encrypt: req.Encrypt, Persist: req.Persist, SignMsgs: req.Encrypt}
 	roomID, err := p.client.CreateRoom(req.Subject, policy)
 	if err != nil {
 		writeErr(w, http.StatusInternalServerError, err.Error())
@@ -336,7 +335,7 @@ func (h *Hub) handleRoom(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	writeJSON(w, http.StatusOK, map[string]any{
-		"room_id": roomID, "subject": req.Subject, "encrypt": req.Encrypt,
+		"room_id": roomID, "subject": req.Subject, "encrypt": req.Encrypt, "persist": req.Persist,
 	})
 }