How to keep context and continue same chat?

[AlexanderTserkovniy]

Simple as is:

1. I create model:

const vertex = createVertex({
  project: '...',
  location: 'us-central1',
});
const vertexModel = vertex('gemini-2.0-flash-exp');

2. On user request I generate response:

if (!currentChats.has(data.chatId)) {
    const streamObjectResp = streamObject({
      model: vertexModel,
      messages: [
        { role: 'system', content: securityPrompts },
        { role: 'system', content: memoryInstructions },
        ...(data.messages.map((message) => ({ role: 'user', content: message.content }))),
      ],
      schema: z.object({
        // valid schema
      }),
    });

    currentChats.set(data.chatId, streamObjectResp);
  }

3. On consequent request I would like to continue in the same chatId so that it keeps context.

According to this (https://sdk.vercel.ai/docs/ai-sdk-ui/storing-messages) example we store previous call parts but where and how do we retrieve them to actually continue?

[AlexanderTserkovniy]

What I did, is I just record messages and response from model onFinish and then provide all these messages with responses to streamObject again when same chat is requested example below.

QUESTION: Does it expected way of doing this, or there is something more mature?

  let messages: CoreMessage[];

  if (!currentChats.has(data.chatId)) {
    console.log("chat not found, creating new");

    messages = [
      {role: 'system', content: securityPrompts},
      {role: 'system', content: memoryInstructions},
      ...(data.messages.map(mapMessageType)),
    ];

  } else {
    messages = currentChats.get(data.chatId)!.messages;
    messages = [
      ...messages,
      ...(data.messages.map(mapMessageType)),
    ];
  }
  
  const streamObjectResp = streamObject({
    model: vertexModel,
    messages: messages,
    schema: z.object({
      // ...
    }),
    onFinish: async (resp) => {
      // update messages
      currentChats.set(data.chatId, {
        status: 'FINISHED',
        resp: streamObjectResp,
        messages: [...messages, {
          role: 'assistant',
          content: `Previous response: ${JSON.stringify(resp.object)}`,
        }]
      });
    }
  });