Multiple Parallel AI Streams with the Vercel AI SDK

export function GenerationForm() {
    // State and other info will be defined here...

        return (
        

          

            Generate News & Weather
          

          {isGenerating ? (
            

              
            
          ) : null}

          
Historical Weather
          

            {weather ? weather : null}
          

          
Historical News
          
{news ? news : null}
        
      )
}

export async function streamAnswer(question: string) {
    // Booleans for indicating whether each stream is currently streaming
  const isGeneratingStream1 = createStreamableValue(true);
  const isGeneratingStream2 = createStreamableValue(true);

  // The current stream values
  const weatherStream = createStreamableValue("");
  const newsStream = createStreamableValue("");

    // Create the first stream. Notice that we don't use await here, so that we
    //  don't block the rest of this function from running.
    streamText({
        // ... params, including the LLM prompt
  }).then(async (result) => {
          // Read from the async iterator. Set the stream value to each new word
          //  received.
      for await (const value of result.textStream) {
        weatherStream.update(value || "");
      }
    } finally {
        // Set isGenerating to false, and close that stream.
      isGeneratingStream1.update(false);
      isGeneratingStream1.done();

      // Close the given stream so the request doesn't hang.
      weatherStream.done();
    }
  });

  // Same thing for the second stream.
    streamText({
        // ... params
  }).then(async (result) => {
      // ...
  })

  // Return any streams we want to read on the client.
  return {
    isGeneratingStream1: isGeneratingStream1.value,
    isGeneratingStream2: isGeneratingStream2.value,
    weatherStream: weatherStream.value,
    newsStream: newsStream.value,
  };
}

"use client";

import { SyntheticEvent, useState } from "react";
import { Button } from "./ui/button";
import { readStreamableValue, useUIState } from "ai/rsc";
import { streamAnswer } from "@/app/actions";
import { Spinner } from "./svgs/Spinner";

export function GenerationForm() {
    // State for loading flags
  const [isGeneratingStream1, setIsGeneratingStream1] = useState(false);
  const [isGeneratingStream2, setIsGeneratingStream2] = useState(false);

  // State for the LLM output streams
  const [weather, setWeather] = useState("");
  const [news, setNews] = useState("");

  // We'll hide the loader when both streams are done.
  const isGenerating = isGeneratingStream1 || isGeneratingStream2;

  async function onSubmit(e: SyntheticEvent) {
    e.preventDefault();

    // Clear previous results.
    setNews("");
    setWeather("");

        // Call the server action. The returned object will have all the streams in it.
    const result = await streamAnswer(question);

    // Translate each stream into an async iterator so we can loop through
    //  the values as they are generated.
    const isGeneratingStream1 = readStreamableValue(result.isGeneratingStream1);
    const isGeneratingStream2 = readStreamableValue(result.isGeneratingStream2);
    const weatherStream = readStreamableValue(result.weatherStream);
    const newsStream = readStreamableValue(result.newsStream);

        // Iterate through each stream, putting its values into state one by one.
        //  Notice the IIFEs again! As on the server, these allow us to prevent blocking
        //   the function, so that we can run these iterators in parallel.
    (async () => {
      for await (const value of isGeneratingStream1) {
        if (value != null) {
          setIsGeneratingStream1(value);
        }
      }
    })();

    (async () => {
      for await (const value of isGeneratingStream2) {
        if (value != null) {
          setIsGeneratingStream2(value);
        }
      }
    })();

    (async () => {
      for await (const value of weatherStream) {
        setWeather((existing) => (existing + value) as string);
      }
    })();

    (async () => {
      for await (const value of newsStream) {
        setNews((existing) => (existing + value) as string);
      }
    })();
  }

  return (
    // ... The form code from before.
  );
}