My Next.js14.2.35 middleware stopped executing on production. After extensive debugging, I traced it to a regression in Vercel CLI50.28.0.
Evidence
I have two deployments of the exact same commit (d14ff83):
Original build (Vercel CLI50.27.1) → middleware works perfectly
Fresh rebuild (Vercel CLI50.28.0) → middleware never executes
Both builds are identical — same Next.js version (14.2.35), same ƒ Middleware 49.8 kB in build output, same routes, same everything. The only difference is the Vercel CLI version.
Symptoms
Middleware compiles successfully and appears in deployment summary under “Routing Middleware” with correct matcher
But it never executes at runtime — no headers set, no logs, no side effects
Middleware does NOT appear in the deployment Functions tab (no Edge function listed)
Even a minimal 5-line middleware (just sets one header, zero dependencies) doesn’t execute
Fails on both custom domains and .vercel.app URL
Clean redeploy without build cache doesn’t help
Tried VERCEL_CLI_VERSION=50.27.1 env var but the version isn’t available on the registry
Middleware location:src/middleware.ts (also tested at project root — same result)
Workaround
Promoting the old deployment built with CLI 50.27.1 restores functionality.
Environment
Framework:Next.js14.2.35 (App Router)
Plan: Hobby
Structure:src/ directory
Is this a known regression in CLI 50.28.0? Is there a way to pin the build CLI version to 50.27.1?
Same problems on my side. Seems that 50.28.0 broke something with the middleware. My multi-tenants app is not redirecting the users to their own sub-domains.
Same issue here. Next.js 15.5.12 with next-intl middleware (localePrefix: ‘as-needed’). All new deployments since
March 6 ignore middleware.ts — unprefixed routes 404 while /en/* works. Vercel AI support confirmed
NEXT_ENABLE_ADAPTER is being injected by the platform, causing Next.js 16 proxy.ts behavior on a Next.js 15 project.
Production site is down. Vercel CLI 50.28.0, Node 24.x.
Same issue, but on 15.5.9 I’m getting this error from clerk
Clerk: auth() was called but Clerk can’t detect usage of clerkMiddleware(). Please ensure the following:
Your Middleware exists at ./middleware.(ts|js)
clerkMiddleware() is used in your Next.js Middleware.
Your Middleware matcher is configured to match this route or page.
If you are using the src directory, make sure the Middleware file is inside of it.
For more details, see https://clerk.com/err/auth-middleware
I am not using the Vercel CLI… just pushing to GitHub… and observe that my middleware seems out of order in the recent deployments…
The Vercel Help bot found that between my working deployments (yesterday) and today’s an env variable was added: VERCEL_SKIP_EDGE_FUNCTION_ENDPOINT
No idea if it’s related or not…
Next.js Middleware fails on Edge Runtime but works with runtime: 'nodejs' on Vercel.
I’m experiencing an issue where Next.js Middleware (middleware.ts) does not execute at all when deployed to Vercel using the default Edge Runtime. However, adding export const runtime = 'nodejs' makes it work correctly.
Environment
Framework:Next.js15.5.9 (App Router)
Deployment:Vercel (Production & Preview)
Dependencies:@clerk/nextjs6.36.5, but issue persists even with minimal middleware
Local dev: Works fine with Edge Runtime (next dev)
Configuration
// middleware.ts (Edge - NOT working on Vercel)
import { clerkMiddleware } from '@clerk/nextjs/server'
export default clerkMiddleware()
export const config = {
matcher: ['/((?!_next/static|_next/image|favicon.ico).*)'],
}
// middleware.ts (Node.js - WORKING on Vercel)
export const runtime = 'nodejs' // Adding this fixes it
import { clerkMiddleware } from '@clerk/nextjs/server'
export default clerkMiddleware()
Observed Behavior
With default Edge Runtime: Middleware never executes (no logs in Vercel Function Logs).
Error:auth() throws:
“can’t detect usage of clerkMiddleware()”
(because the middleware chain is broken).
With runtime = 'nodejs': Middleware executes correctly on every matched request.
Steps Tried
Simplified matcher to catch-all patterns
Cleared Vercel build cache & redeployed
Upgraded to latest Next.js and @clerk/nextjs versions
Verified file location (src/middleware.ts at project root level)
Expected Behavior
Edge Runtime should work as documented for Middleware, or documentation should clarify when Node.js runtime is required.
Additional Context
Issue appears specific to Vercel build environment; local next dev works fine with Edge Runtime.
Running build in Washington, D.C., USA (East) – iad1
Build machine configuration: 2 cores, 8 GB
Cloning github.com/RCFans/StrategyLogic (Branch: main, Commit: 8a6fc5f)
Cloning completed: 1.806s
Restored build cache from previous deployment (DQrH1rmBSHDcQhpyaYjNHWWAEPRd)
Running "vercel build"
Vercel CLI 50.28.0
Detected `pnpm-lock.yaml` 9 which may be generated by pnpm@9.x or pnpm@10.x
Using pnpm@9.x based on project creation date
Same here, this is is crashing our site. I was able to promote a previous deployment from a few hours ago and that has at least brought the site back up.
Strangely, that deployment also use CLI 50.28.0 about 5 hours ago and succeeded. Everything after that suffered the issue discussed here - no middleware invocation whatsoever.
Also for future reference, I checked the Vercel status page frequently over the past hour and there was no mention of this - would have been nice to at least have some mention of an investigation instead of me debugging alone, diagnosing the issue, then doing a general search to find this community thread.
But yeah, heard. Appreciate the feedback, Dalyan! 