payloadCMS always light theme middleware.

middleware.ts

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

export function middleware(req: NextRequest) {
  const res = NextResponse.next();

  const currentTheme = req.cookies.get("payload-theme");

  if (!req.cookies.has("payload-theme") || currentTheme?.value === "dark") {
    res.cookies.set("payload-theme", "light")
  }

  return res;
}

// Apply middleware to all admin routes
export const config = {
  matcher: "/admin/:path*",
};