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Vercel Functions using Node.js can now detect when a request is cancelled and stop execution before completion. This is configurable on a per-path basis, and includes actions like navigating away, closing a tab, or hitting stop on an AI chat to terminate compute processing early.
This reduces unnecessary compute, token generation, and sending data the user would never see.
To enable cancellation, add "supportsCancellation": true to your vercel.json configuration. You can apply it to specific paths or all functions:
vercel.json
{ "functions": { "api/*": { "supportsCancellation": true } }}Once enabled, you can listen for cancellation using Request.signal.aborted or the abort event:
export const GET = async (req: Request) => { const abortController = new AbortController();
req.signal.addEventListener("abort", () => { console.log("request aborted"); abortController.abort(); });
const res = await fetch("https://my-backend-service.example.com", { headers: { Authorization: `Bearer ${process.env.AUTH_TOKEN}`, }, signal: abortController.signal, });
return new Response(res.body, { status: res.status, headers: res.headers, });};If you’re using the AI SDK, forward the abortSignal to your stream:
import { openai } from '@ai-sdk/openai';import { streamText } from 'ai';
export async function POST(req: Request) { const { prompt } = await req.json(); const result = streamText({ model: openai('gpt-4-turbo'), prompt, // forward the abort signal abortSignal: req.signal, }); return result.toTextStreamResponse();}Learn more about cancelling Function requests.