vercel/next.js · error · Error

Not implemented: this behavior is not yet supported when `ex

Error message

Not implemented: this behavior is not yet supported when `experimental.concurrentRouterQueue` is enabled.

What it means

Deliberate stub in the Node-side copy of the concurrent router queue. Every operation routes through notImplemented so that enabling experimental.concurrentRouterQueue in a context that would execute this bundle fails loudly instead of silently falling back to the legacy sequential queue implementation.

Source

Thrown at packages/next/src/client/components/concurrent-router-queue.ts:28

// the pre-compiled app-page runtime bundles (via app-render.tsx), where the
// bundler alias cannot reach. Only the browser copy's operations ever run.
//
// TODO: This is currently a stub. Every operation throws so that enabling
// the flag fails loudly instead of silently running the old implementation.

import type {
  AppHistoryState,
  NavigateAction,
  ScrollBehavior,
} from './router-reducer/router-reducer-types'
import type { NavigateOptions } from '../../shared/lib/app-router-context.shared-runtime'
import type { LinkInstance } from './links'
import type { RouterTransitionPrefetchIntent } from '../router-transition-types'

// Keep in sync with the identical message in concurrent-call-server.ts, so
// all unimplemented behavior shares a single error (and error code).
function notImplemented(): never {
  throw new Error(
    'Not implemented: this behavior is not yet supported when ' +
      '`experimental.concurrentRouterQueue` is enabled.'
  )
}

export function navigate(
  _href: string,
  _navigateType: NavigateAction['navigateType'],
  _scrollBehavior: ScrollBehavior,
  _linkInstanceRef: LinkInstance | null,
  _transitionTypes: string[] | undefined,
  _prefetchIntent: RouterTransitionPrefetchIntent | null
): void {
  notImplemented()
}

export function push(_href: string, _options?: NavigateOptions): void {
  notImplemented()

View on GitHub (pinned to 0eb3775416)

Solutions

1. Disable experimental.concurrentRouterQueue, or avoid the unsupported router operation while it is enabled.

When it happens

Trigger: A router behavior not yet supported is invoked while experimental.concurrentRouterQueue is enabled.

Common situations: Code paths hit an unimplemented branch of the concurrent router queue experiment.

AI-assisted analysis of vercel/next.js@0eb3775416 (2026-08-19). Data as JSON: /api/errors/5a9c4ccc31a5fb9b. Report an issue: GitHub.