Quick dip: Use Google Cloud Vertex AI SDK with the Vercel AI SDK

// app/api/chat/route.ts

import { VertexAI } from "@google-cloud/vertexai";

import { GoogleGenerativeAIStream, Message, StreamingTextResponse } from "ai";



const project = process.env.GOOGLE_CLOUD_PROJECT || "";

const location = "us-central1";



const vertexAI = new VertexAI({ project: project, location: location });



// Google GenAI API can use the edge runtime. This will not work with Vertex AI

// export const runtime = 'edge';



// Instantiate Gemini models

const generativeModel = vertexAI.getGenerativeModel({

  model: "gemini-pro",

});



const buildGoogleGenAIPrompt = (messages: Message[]) => ({

  contents: messages

    .filter(

      (message) => message.role === "user" || message.role === "assistant"

    )

    .map((message) => ({

      role: message.role === "user" ? "user" : "model",

      parts: [{ text: message.content }],

    })),

});



export async function POST(req: Request) {

  // Extract the `prompt` from the body of the request

  const { messages } = await req.json();



  const geminiStream = await generativeModel.generateContentStream(

    buildGoogleGenAIPrompt(messages)

  );



  // Convert the response into a friendly text-stream

  // GoogleGenerativeAIStream class decodes/extracts the text tokens in the

  // response and then re-encodes them properly for simple consumption.

  const stream = GoogleGenerativeAIStream(geminiStream);



  // Respond with the stream

  return new StreamingTextResponse(stream);

}