A Node.js module is loaded ('async_hooks' at line 6) which is not supported in the Edge Runtime.

[empz]

Warning during Next.js 14.2.35 (app router) build.

flags: 4.0.1
@flags-sdk/edge-config: 0.1.0

./node_modules/flags/dist/chunk-ISCGLTLL.js
A Node.js module is loaded ('async_hooks' at line 6) which is not supported in the Edge Runtime.
Learn More: https://nextjs.org/docs/messages/node-module-in-edge-runtime

Import trace for requested module:
./node_modules/flags/dist/chunk-ISCGLTLL.js
./node_modules/flags/dist/next.js
./src/lib/flags.ts

import { edgeConfigAdapter } from "@flags-sdk/edge-config";
import { flag } from "flags/next";
import { AppConfig } from "@/config"; // This is just a plain Typescript object export (no imports on this file)

// Maintenance mode flag
const maintenanceModeEnabled = flag({
  key: AppConfig.featureFlags.maintenanceModeEnabled,
  adapter: edgeConfigAdapter(),
  defaultValue: true,
});

// Dual language layout feature flag
const dualLanguageLayoutEnabled = flag({
  key: AppConfig.featureFlags.dualLanguageLayoutEnabled,
  adapter: edgeConfigAdapter(),
  defaultValue: false,
});

// Flags object for clean API access
export const Flags = {
  maintenanceModeEnabled,
  dualLanguageLayoutEnabled,
} as const;

[empz]

Upgraded to latest versions (flags=4.0.2 and @flags-sdk/edge-config=0.1.2) and same issue.

[dferber90]

This is a limitation of the Edge Runtime. I don't think it actually has any effects on the behavior of the Flags SDK.

To get rid of the warning you can start using proxy.ts instead of middleware.ts which will not use Edge Runtime and thus avoid the warning altogether.

Links

• https://x.com/leerob/status/1780705942734331983
• https://nextjs.org/docs/messages/node-module-in-edge-runtime

[empz]

This is a limitation of the Edge Runtime. I don't think it actually has any effects on the behavior of the Flags SDK.

To get rid of the warning you can start using proxy.ts instead of middleware.ts which will not use Edge Runtime and thus avoid the warning altogether.

Links

• x.com/leerob/status/1780705942734331983
• nextjs.org/docs/messages/node-module-in-edge-runtime

I know it's a limitation of the Edge Runtime, but this wasn't happening before I think. Using proxy requires upgrading to Next 16. But okay.

[mischnic]

On Next.js >= 15.5, you can use Middleware with Node.js runtime: https://nextjs.org/blog/next-15-5#nodejs-middleware-stable
The only difference in Next.js 16 is that proxy.js switches the default runtime from Node.js to Edge.

[dferber90]

Closing as we need AsyncLocalStorage for the inner workings of the SDK and thus it's not actionable.