Transport

Transport is the part that receives MLForm values and returns model output. It can call HTTP, GraphQL, gRPC, a worker, a browser model, or your own async function.

Every normal transport has one main job:

async submit(request) {
  return { reports: { prediction: { label: "Approved", confidence: 0.92 } } };
}

request contains serialized field values plus metadata. The response feeds reports. The runtime does not care which protocol produced it.

Transport options add policy around that contract:

Concept	Meaning
capability	What a transport can safely do: submit, stream, retry, cache, auth, limits.
middleware	Auth, timeout, retry, cache, tracing, metrics, rate limit, circuit breaker.
orchestration	Routing, fallback, fanout, quorum, hedging, load balancing.
policy backend	Shared cache, limiter, breaker, or health state outside one form instance.

Use createJsonTransport() for the usual backend endpoint. Reach for custom transports when submission already belongs to another app service or local model.