Item 'rs_...' of type 'reasoning' was provided without its required following item #7099
Description
Description
When using the openai.responses() API with a reasoning model, a tool call results in an error.
However, using openai.chat() avoids the error — but tool calling and reasoning streaming are not available in that mode.
Code
import { openai } from "@ai-sdk/openai";
import { streamText, Output, stepCountIs, convertToModelMessages } from "ai";
import { devTools } from "../tools";
import { z } from "zod";
// Allow streaming responses up to 60 seconds for more complex generations
export const maxDuration = 60;
export function errorHandler(error: unknown) {
if (error == null) {
return "unknown error";
}
if (typeof error === "string") {
return error;
}
if (error instanceof Error) {
return error.message;
}
return JSON.stringify(error);
}
// Structured output schema for website code
const WebsiteSchema = z.object({
html: z.string().describe("Whole HTML code"),
});
export async function POST(req: Request) {
try {
const { messages } = await req.json();
// Validate messages
if (!Array.isArray(messages)) {
return new Response("Invalid messages format", { status: 400 });
}
const result = streamText({
model: openai.responses(process.env.OPENAI_MODEL || "gpt-4o"),
system: "...",
messages: convertToModelMessages(messages),
stopWhen: stepCountIs(100),
tools: devTools,
abortSignal: req.signal, // Add abort signal for proper cancellation
experimental_output: Output.object({
schema: WebsiteSchema,
}),
});
return result.toUIMessageStreamResponse({
onError: errorHandler,
});
} catch (error) {
console.error("Dev API error:", error);
return new Response(errorHandler(error), { status: 500 });
}
}Problem
When using reasoning models with openai.responses(), calling a tool throws the following error:
[Error [AI_APICallError]: Item 'rs_...' of type 'reasoning' was provided without its required following item.] {
cause: undefined,
url: 'https://api.openai.com/v1/responses',
requestBodyValues: [Object],
statusCode: 400,
responseHeaders: [Object],
responseBody: '{
"error": {
"message": "Item 'rs_...' of type 'reasoning' was provided without its required following item.",
"type": "invalid_request_error",
"param": "input",
"code": null
}
}',
isRetryable: false,
data: [Object]
}
Workaround
Using openai.chat() avoids the error entirely, but does not support streaming reasoning or tool calls, which limits its utility in certain applications.
AI SDK Versions
ai:^5.0.0-beta.7@ai-sdk/openai:^2.0.0-beta.5@ai-sdk/react:^2.0.0-beta.7