useStream

React binding for the v2-native stream runtime.

useStream exposes three always-on projections (values / messages / toolCalls) at the thread root plus cheap discovery maps for subagents / subgraphs. Scoped views of subagents, subgraphs, or any namespaced projection are surfaced via the companion selector hooks:

const stream = useStream({ assistantId: "deep-agent" });

// Root messages — always on, already class instances.
stream.messages.map((m) => <Bubble key={m.id} msg={m} />);

// Subagent view — mount = subscribe, unmount = unsubscribe.
function SubagentCard({ subagent }) {
  const messages = useMessages(stream, subagent);
  const toolCalls = useToolCalls(stream, subagent);
  return <>{messages.map(...)}</>;
}

The first generic accepts either a plain state type (useStream<MyState>()) or a compiled graph type (useStream<typeof agent>()); in the latter case the state shape is unwrapped from the graph via InferStateType, so stream.values is always typed as the state, never as the graph class itself.