`@ag-ui/mastra@0.1.1` still calls `streamVNext`, but Mastra client only exposes `stream`

[Shitaro]

Summary

@ag-ui/mastra@0.1.1 continues to invoke agent.streamVNext(...), but the current Mastra client (@mastra/client-js@0.15.0) renamed the method to stream. As a result, CopilotKit requests fail with:

Error: streamVNext has been renamed to stream. Please use stream instead.
    at Observable._trySubscribe (../../../src/internal/Observable.ts:244:19)
    ...

This issue has been reported at #384 (comment).

Environment

• @ag-ui/mastra: 0.1.1
• @mastra/client-js: 0.15.1
• @copilotkit/runtime: 1.10.5
• Next.js 15.5.4 / React 19.1.0

Steps to Reproduce

1. Install the packages above in a Next.js app.
2. Use MastraAgent.getRemoteAgents({ mastraClient }) as in the CopilotKit guide.
3. Start the app and send a chat request (POST /copilotkit).
4. Check the server logs.

Expected Behavior

MastraAgent should call the new agent.stream(...) (or fall back appropriately) so streaming works with the latest Mastra client.

Actual Behavior

MastraAgent.streamMastraAgent invokes this.agent.streamVNext(...), which throws the error above and prevents responses from streaming.

Workaround

Monkey-patch the returned agents:

Object.values(mastraAgents).forEach((wrapper: any) => {
  if (typeof wrapper?.stream === "function") {
    wrapper.streamVNext = wrapper.stream.bind(wrapper);
  }
  const inner = wrapper.agent ?? wrapper._agent;
  if (inner && typeof inner.stream === "function") {
    inner.streamVNext = inner.stream.bind(inner);
  }
});

Additional Context

PR #384 (feat: support mastra vNext streaming) already replaces the streamVNext call. Could you publish that change (e.g., in 0.1.2) so the workaround is no longer required? Oh, missunderstood

[xmlking]

looks like we also need to patch getNetwork()

@tylerslaton

[xmlking]

couple of Monkey-patches helped bring back basic fictionally:

import { MastraAgent } from "@ag-ui/mastra";
import {
  CopilotRuntime,
  copilotRuntimeNextJSAppRouterEndpoint,
  ExperimentalEmptyAdapter,
  OpenAIAdapter,
} from "@copilotkit/runtime";

import { mastra } from "@repo/mastra";
import type { NextRequest } from "next/server";

//---- Workaround; Monkey-patch ----
// https://github.com/ag-ui-protocol/ag-ui/issues/486

if (!(mastra as any).vnext_getNetworks) {
  (mastra as any).vnext_getNetworks = () => [];
}

const mastraAgents = MastraAgent.getLocalAgents({ mastra });


for (const wrapper of Object.values(mastraAgents) as any[]) {
  if (typeof wrapper?.stream === "function") {
    wrapper.streamVNext = wrapper.stream.bind(wrapper);
  }
  const inner = wrapper.agent ?? wrapper._agent;
  if (inner && typeof inner.stream === "function") {
    inner.streamVNext = inner.stream.bind(inner);
  }
}
//---- Workaround; Monkey-patch ----

const serviceAdapter = new ExperimentalEmptyAdapter();

const runtime = new CopilotRuntime({
  agents: {
    ...mastraAgents,
  },
});


export const POST = (req: NextRequest) => {
  const { handleRequest } = copilotRuntimeNextJSAppRouterEndpoint({
    runtime,
    serviceAdapter,
    endpoint: req.nextUrl.pathname,
  });

  return handleRequest(req);
};

[tylerslaton]

Hi all, just released a fix with the help of a contribution of @ludovicc. You can all use @ag-ui/mastra: 0.2.0.

#507