Transports

A transport implements ITransportAdapter — subscribe, publish, plus optional extensions (invoke, getWireTopicInfo, etc.). The SDK ships three: an in-process broker for tests and demos, a Node-side NATS adapter for runners and headless tools, and a browser-side NATS adapter that opens a WebSocket and refreshes JWTs.

Pages in this section

Page	What you'll learn
In-memory transport	InMemoryBroker + InMemoryTransport — how the in-process bus works, queueing, latency injection.
NATS transport	NatsTransport — root-prefix grammar, validation, JSON encoding, the INatsLikeConnection adapter.
Browser transport	createBrowserNatsTransport — WebSocket connect, JWT refresh, token/user-pass fallbacks.
Transport testing	Stubbing transports for actor unit tests, real-NATS harness for integration tests.

Picking a transport

Situation	Use
Unit test, single-process actor system	InMemoryTransport (with InMemoryBroker).
Production Node-side runtime, supervised by Host Service	NatsTransport over the bundled NATS sibling (the runner wires it for you).
Browser tab connected to a Host's NATS	createBrowserNatsTransport over /nats-ws.
Federation: actor invokes across roots	FederationTransportAdapter wrapping the underlying transport.

You almost never construct a transport by hand in production code. The runner (Host Service) constructs the right transport and passes it into MatrixRuntime. You construct transports yourself in tests.

Wire format, briefly

All three transports carry MxEnvelope JSON:

{ "op": "market.quote", "payload": { "symbol": "TSLA" }, "from": "<sender>", "lamport": 42 }

InMemoryTransport passes the object reference directly — no serialization. NatsTransport encodes/decodes via TextEncoder/TextDecoder + JSON.stringify/JSON.parse. The browser variant uses the same NATS adapter under the hood with a WebSocket connection.

Subject prefixing

NATS-backed transports prepend an authority root to every subject:

<root>.<mount>.$inbox       ← inbox
<root>.<mount>.$events      ← events
<root>.$reply.<corrId>       ← reply

The root is a DNS-style identifier like COM.NIMBLETEC.RICHARD-SANTOMAURO. InMemoryTransport does not prefix — its topicPrefix is the empty string.

getWireTopicInfo(topic) (ITransportAdapter extension) lets a caller inspect what wire subject a logical topic resolves to. Useful for debugging.

Source: projects/matrix-3/packages/core/src/engine/messaging/TopicRouter.ts (subject grammar), projects/matrix-3/packages/core/src/transport/{InMemoryTransport,NatsTransport,createBrowserNatsTransport}.ts (each adapter).