Streaming

Streaming leaves provide two views. An accumulated streamed query caches emissions in order. A live query caches the latest value. Use ordinary query hooks or QueryObserver for both. Start with a ready RPC or HTTP utility tree. Here, diagnostics.stream is an inputless RPC emitting strings, and events.watch is an HTTP SSE endpoint declaring query.channel and emitting strings.

Accumulate values

Choose a finite history for a long-running feed:

const history = rpc.diagnostics.stream.streamedOptions({
  maxChunks: 100,
  refetchMode: 'reset',
})

HTTP SSE supports the same history controls and a separate decoder limit:

const sseHistory = http.events.watch.streamedOptions({
  input: { query: { channel: 'news' } },
  maxChunks: 100,
  sseOptions: { maxEventSize: 1024 * 1024 },
})

The first emission makes the query successful while fetching continues. maxChunks bounds cached elements after each emission. If you omit it, history is unlimited. It does not bound bytes or transport buffering.

Refetch mode reset starts a new history, append adds to it, and replace keeps the old history until successful completion. An indefinitely open replacement keeps showing that old history. Accumulated streams can succeed without emissions.

Keep the latest value

Choose live options for current state:

const latest = rpc.diagnostics.stream.liveOptions()
const latestSse = http.events.watch.liveOptions({
  input: { query: { channel: 'news' } },
  sseOptions: { maxEventSize: 1024 * 1024 },
})

Each emission replaces cached data. Completion preserves that data. Live queries convert top-level undefined to null, while accumulated elements retain undefined. Empty live completion raises the adapter’s empty-stream error. Live options accept neither maxChunks nor refetchMode.

Address and stop a view

For exact cache access, reuse the options’ queryKey. Accumulated history policies and HTTP decoder policies affect identity. Live and accumulated views remain separate. Endpoint prefixes match all their views.

Cancellation closes the stream iterator. Your application owns reconnection, resume policy, and client lifetime. HTTP sseOptions.maxEventSize bounds pending parser text in JavaScript string code units. Its default is 10 × 1024 × 1024 code units. Put declared resume headers in input.headers.

See Choose Stream History for retention and buffering, Stream Snapshots for finite server captures, and Client Lifecycle for cleanup ownership.