universal_storage_mesh_transport

Transport seam for mesh sync (ADR 0010): peer and session interfaces, length-prefixed framing for stream transports, and a deterministic fake transport for headless tests. Real radio transports (LAN mDNS+TCP first, BLE-class later) are separate packages implementing MeshTransport.

North Star: ../universal_storage_mesh/docs/north_star.mdx (the transport seam is one slice of the mesh center).

Contract

abstract interface class MeshTransport {
  /// Sessions initiated by remote peers; every inbound session delivered
  /// exactly once.
  Stream<MeshSession> get incoming;

  /// Opens a session to a previously paired [peer].
  /// Throws [MeshConnectionException] when this transport cannot reach
  /// that peer — never silently connects somewhere else.
  Future<MeshSession> connect(MeshPeerRecord peer);
}

abstract interface class MeshSession {
  String get remotePeerId;
  Stream<Uint8List> get inbound;
  Future<void> send(Uint8List payload);
  Future<void> close();
}

Implementations know nothing about documents or convergence: frames carry convergence-kernel envelopes only. Real transports must establish session keys from pairing material before delivering any inbound bytes; the fake transport used in tests is plaintext by design.

Testing your transport

FakeMeshPair.paired() gives two linked transports for provider tests:

final pair = FakeMeshPair.paired(a: 'device-a', b: 'device-b');
pair.b.incoming.listen(responderHandler);
final session = await pair.a.connect(
  const MeshPeerRecord(peerId: 'device-b', displayName: 'B'),
);

For stream-based real transports, frameMessage + FrameDecoder provide 4-byte big-endian length framing with incremental de-framing.