Next.js · build warning

The "middleware" file convention is deprecated

⚠ The "middleware" file convention is deprecated. Please use "proxy" instead.

  To migrate automatically, run:
  npx @next/codemod@canary middleware-to-proxy .

What it means

Next.js 16 renamed middleware.ts to proxy.ts. Agents keep creating middleware.ts because most examples predate the rename. Proxy runs on the Node.js runtime, and the runtime option isn't allowed in proxy files.

Common causes

• An agent added auth or redirects in middleware.ts
• Code copied from Next.js 13–15 or Auth.js v4 examples

How to fix it

1. Run npx @next/codemod@canary middleware-to-proxy . or rename the file and the exported function to proxy
2. Remove any export const runtime = "edge" from it
3. Keep matchers in export const config as before

import { NextResponse, type NextRequest } from "next/server";

export function proxy(request: NextRequest) {
  return NextResponse.next();
}

export const config = { matcher: ["/dashboard/:path*"] };

Prompt for Cursor or Claude Code

This is Next.js 16: middleware.ts is deprecated in favor of proxy.ts. Migrate it (rename the file and the exported function to proxy, keep the matcher config, remove any runtime export) and check nothing else imports the old file.

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