Anvia

Transports ​

JSONL and SSE carry the same event values with different framing.

JSONL ​

ts
return createEventStreamResponse({ events, format: 'jsonl' })

Each event is serialized to JSON and followed by \n. The response content type is application/x-ndjson; charset=utf-8. JSONL is compact and is the default for Anvia React clients.

Use jsonl.serialize only when both ends agree on a custom representation:

ts
createEventStreamResponse({
  events,
  jsonl: {
    serialize: (event) => JSON.stringify(event),
  },
})

The serializer also receives the final server error event when iteration throws. Well-known diagnostic fields (code, retryable, JSON-safe details) survive on JSONL and SSE error events — including errors from runtime-specific subclasses whose prototype fields JSON.stringify would drop — and non-JSON-safe thrown values degrade to a { message } payload. The errorEvent helper is public.

Server-Sent Events ​

ts
return createEventStreamResponse({
  events,
  format: 'sse',
  sse: {
    eventName: (event) => 'type' in event ? String(event.type) : undefined,
    retry: 3_000,
  },
})

SSE writes serialized JSON as data: lines and uses text/event-stream; charset=utf-8. eventName can be static or computed per event. The implementation validates event names and retry values before streaming.

The package does not emit heartbeat comments. Add a heartbeat at the application event-source layer when a proxy requires traffic during long idle periods.

Custom response metadata ​

headers, status, and statusText pass through to the Response. Existing transport headers are respected rather than overwritten. Authentication and CORS headers remain route-owned.

Pair client-protocol responses with createHttpClientTransport({ format }) from @anvia/client. Generic stream readers are available from @anvia/client/transport.

Built for Anvia.