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agent.stream returns an async iterable that emits tokens while exposing promises to retrieve the final state. 
const stream = await assistant.stream({
  prompt: "Draft an outline for an AI Kit guide.",
  temperature: 0.5,
});

for await (const chunk of stream.textStream) {
  process.stdout.write(chunk);
}

const finalText = await stream.text;
console.log("\n---\n", finalText);

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Key properties

  • textStream – AsyncIterable<string> with generated tokens.
  • fullStream – complete stream (text, reasoning, tool calls, errors).
  • text, response, usage, steps – promises that resolve once the stream completes.
  • loopTool – boolean flag set when the tool loop runs.
  • toAIStreamResponse() / toDataStreamResponse() – pipe the stream into HTTP responses (Next.js, Remix, …).

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Conversational streaming

const streamedChat = await assistant.stream({
  messages: [
    { role: "user", content: "Describe the lifecycle of an AI Kit agent." },
  ],
});

for await (const delta of streamedChat.textStream) {
  process.stdout.write(delta);
}

​
Structured outputs while streaming

Combine agent.stream with structuredOutput to receive partial fragments during the stream and the validated object at the end. 
const streamWithSchema = await assistant.stream({
  prompt: "Provide a structured test profile.",
  structuredOutput: personSpec,
});

let lastPartial;
for await (const partial of streamWithSchema.experimental_partialOutputStream) {
  lastPartial = partial;
  console.log("partial", partial);
}

const parsedOutput = await personSpec.parseOutput(
  { text: await streamWithSchema.text },
  {
    response: await streamWithSchema.response,
    usage: await streamWithSchema.usage,
    finishReason: await streamWithSchema.finishReason,
  },
);

console.log({ lastPartial, parsedOutput });
experimental_partialOutputStream emits schema-compliant fragments. Cache the last one for a provisional UI, then call parseOutput to obtain the final typed object.
Structured streaming is experimental—plan retries when parsing fails.