vercel/ai

Description

After migrating from AI SDK v6 (ai@6, @ai-sdk/openai@3, @ai-sdk/react@3) to v7 ([email protected], @ai-sdk/[email protected], @ai-sdk/[email protected]), streamText tool calls execute correctly but the assistant's text output is silently dropped — the chat UI renders tool badges (e.g. createJob done, searchJobs done) but no text content.

This affects both streamText + toUIMessageStream and ToolLoopAgent + createAgentUIStreamResponse — same underlying pipeline.

generateText works correctly on the same provider and model.

Environment

• ai: 7.0.0
• @ai-sdk/openai: 4.0.0
• @ai-sdk/react: 4.0.0
• Next.js: 16.2.7
• Node.js: 24.x
• Runtime: Vercel (Node.js)
• Provider: OpenAI-compatible endpoint via createOpenAI({ apiKey, baseURL }) with a custom baseURL (not api.openai.com)

Reproduction

Server (app/api/chat/route.ts)

import { streamText, isStepCount, convertToModelMessages, toUIMessageStream, createUIMessageStreamResponse } from "ai";
import { createOpenAI } from "@ai-sdk/openai";

const provider = createOpenAI({
  apiKey: process.env.AI_API_KEY,
  baseURL: process.env.AI_BASE_URL, // custom OpenAI-compatible endpoint
});
const model = provider("gpt-4o-mini"); // or any model the endpoint supports

const myTool = tool({
  description: "Create something",
  inputSchema: z.object({ name: z.string() }),
  execute: async ({ name }) => ({ ok: true, name }),
});

export async function POST(req: Request) {
  const { messages } = await req.json();

  const result = streamText({
    model,
    instructions: "You are a helpful assistant.",
    messages: await convertToModelMessages(messages),
    tools: { myTool },
    stopWhen: isStepCount(5),
  });

  // BOTH of these produce the same bug:

  // Option 1: deprecated instance method
  return result.toUIMessageStreamResponse();

  // Option 2: standalone v7 pattern
  // return createUIMessageStreamResponse({
  //   stream: toUIMessageStream({ stream: result.stream, tools: { myTool } }),
  // });
}