handleChatStream()

Framework-agnostic handler for streaming agent chat in AI SDK-compatible format. Use this function directly when you need to handle chat streaming outside Hono or Mastra's own apiRoutes feature.

handleChatStream() returns a ReadableStream that you can wrap with createUIMessageStreamResponse().

Use chatRoute() if you want to create a chat route inside a Mastra server.

Usage example

Next.js App Router example:

app/api/chat/route.ts

import { handleChatStream } from '@mastra/ai-sdk';
import { createUIMessageStreamResponse } from 'ai';
import { mastra } from '@/src/mastra';

export async function POST(req: Request) {
  const params = await req.json();
  const stream = await handleChatStream({
    mastra,
    agentId: 'weatherAgent',
    params,
  });
  return createUIMessageStreamResponse({ stream });
}

Parameters

mastra:

Mastra

The Mastra instance containing registered agents.

agentId:

string

The ID of the agent to use for chat.

params:

ChatStreamHandlerParams

Parameters for the chat stream, including messages and optional resume data.

params.messages:

UIMessage[]

Array of messages in the conversation.

params.resumeData?:

Record<string, any>

Data for resuming a suspended agent execution. Requires `runId` to be set.

params.runId?:

string

The run ID. Required when `resumeData` is provided.

params.requestContext?:

RequestContext

Request context to pass to the agent execution.

defaultOptions?:

AgentExecutionOptions

Default options passed to agent execution. These are merged with params, with params taking precedence.

sendStart?:

boolean

= true

Whether to send start events in the stream.

sendFinish?:

boolean

= true

Whether to send finish events in the stream.

sendReasoning?:

boolean

= false

Whether to include reasoning steps in the stream.

sendSources?:

boolean

= false

Whether to include source citations in the stream.