Split VPN fabric batches by stream

agents/rap-node-agent/internal/vpnruntime/fabric_session_transport.go

@@ -67,14 +67,15 @@ func (t *FabricSessionPacketTransport) SendGatewayPacketBatch(ctx context.Contex
 	if direction == "" {
 		direction = FabricDirectionGatewayToClient
 	}
-	streamID, trafficClass := t.selectStreamForPackets(packets)
+	groups := t.groupPacketsByStream(packets)
+	for _, group := range groups {
 		frame, err := NewFabricVPNPacketDataFrame(FabricVPNPacketFrameInput{
-		StreamID:        streamID,
+			StreamID:        group.StreamID,
-		Sequence:        t.nextSequence(streamID),
+			Sequence:        t.nextSequence(group.StreamID),
 			VPNConnectionID: t.VPNConnectionID,
 			Direction:       direction,
-		TrafficClass:    trafficClass,
+			TrafficClass:    group.TrafficClass,
-		Packets:         packets,
+			Packets:         group.Packets,
 		})
 		if err != nil {
 			return err
@@ -82,7 +83,8 @@ func (t *FabricSessionPacketTransport) SendGatewayPacketBatch(ctx context.Contex
 		if err := t.Sender.Send(ctx, frame); err != nil {
 			return err
 		}
-	t.recordSend(streamID, trafficClass, len(packets))
+		t.recordSend(group.StreamID, group.TrafficClass, len(group.Packets))
+	}
 	return nil
 }
 
@@ -227,6 +229,32 @@ func (t *FabricSessionPacketTransport) selectStreamForPackets(packets [][]byte)
 	return t.StreamID, trafficClass
 }
 
+type fabricSessionPacketGroup struct {
+	StreamID     uint64
+	TrafficClass string
+	Packets      [][]byte
+}
+
+func (t *FabricSessionPacketTransport) groupPacketsByStream(packets [][]byte) []fabricSessionPacketGroup {
+	groups := []fabricSessionPacketGroup{}
+	indexByKey := map[string]int{}
+	for _, packet := range packets {
+		streamID, trafficClass := t.selectStreamForPackets([][]byte{packet})
+		key := fmt.Sprintf("%d\x00%s", streamID, trafficClass)
+		index, ok := indexByKey[key]
+		if !ok {
+			index = len(groups)
+			indexByKey[key] = index
+			groups = append(groups, fabricSessionPacketGroup{
+				StreamID:     streamID,
+				TrafficClass: trafficClass,
+			})
+		}
+		groups[index].Packets = append(groups[index].Packets, packet)
+	}
+	return groups
+}
+
 func (t *FabricSessionPacketTransport) allStreamIDs() []uint64 {
 	if t == nil {
 		return nil

agents/rap-node-agent/internal/vpnruntime/fabric_transport_test.go

@@ -284,6 +284,43 @@ func TestFabricSessionPacketTransportShardsStreamsByTrafficClass(t *testing.T) {
 	}
 }
 
+func TestFabricSessionPacketTransportSplitsMixedBatchByStream(t *testing.T) {
+	sender := &captureFabricSessionSender{}
+	transport := &FabricSessionPacketTransport{
+		Sender:          sender,
+		VPNConnectionID: "vpn-1",
+		SendDirection:   FabricDirectionClientToGateway,
+		StreamIDsByTrafficClass: map[string][]uint64{
+			FabricTrafficClassInteractive: []uint64{801},
+			FabricTrafficClassBulk:        []uint64{901, 902},
+		},
+	}
+	bulkA := testIPv4TCPPacket([4]byte{10, 77, 0, 2}, [4]byte{192, 168, 200, 95}, 51000, 443)
+	bulkB := packetWithDifferentShard(bulkA, 2)
+	control := testIPv4TCPPacket([4]byte{10, 77, 0, 2}, [4]byte{192, 168, 200, 95}, 51001, 3389)
+	control[33] = 0x02
+
+	if err := transport.SendGatewayPacketBatch(context.Background(), [][]byte{bulkA, bulkB, control}); err != nil {
+		t.Fatalf("send mixed batch: %v", err)
+	}
+	if len(sender.frames) != 3 {
+		t.Fatalf("sent frames = %d, want 3: %+v", len(sender.frames), sender.frames)
+	}
+	streams := map[uint64]fabricproto.TrafficClass{}
+	for _, frame := range sender.frames {
+		streams[frame.StreamID] = frame.TrafficClass
+	}
+	if streams[801] != fabricproto.TrafficClassInteractive ||
+		streams[901] != fabricproto.TrafficClassBulk ||
+		streams[902] != fabricproto.TrafficClassBulk {
+		t.Fatalf("unexpected stream/class split: %+v", sender.frames)
+	}
+	snapshot := transport.Snapshot()
+	if snapshot["send_stream_count"] != 3 || snapshot["send_class_count"] != 2 {
+		t.Fatalf("unexpected mixed-batch shard summary: %+v", snapshot)
+	}
+}
+
 func TestFabricSessionPacketTransportClosesAllStreamShards(t *testing.T) {
 	sender := &captureFabricSessionSender{}
 	transport := &FabricSessionPacketTransport{

docs/architecture/DISTRIBUTED_FABRIC_NODE_PROTOCOL_PLAN.md

@@ -399,6 +399,9 @@ when either direction exits, so transport cleanup runs promptly on one-sided
 TUN or carrier failures.
 Fabric-session packet transport snapshots include close-frame and close-error
 counters for verifying that stream shard cleanup is actually happening.
+Outgoing VPN packet batches are split by traffic class and selected stream
+before they are framed, so one gateway batch containing many browser flows does
+not collapse onto the first packet's logical stream.
 Endpoint ranking treats `capacity_limited` observations as a soft pressure
 penalty instead of a hard recent failure, enabling load spreading without
 marking the carrier unhealthy.