Troubleshooting broken routes after deploying V0 to Vercel

Why routes break after deploying V0 to Vercel

V0's Vercel Sandbox preview runs code differently from a production Vercel deployment. The preview may handle routing more leniently, resolve missing pages silently, or proxy requests in ways that production does not. The most common issues are: V0 generates client-side navigation that works in preview but has no corresponding page.tsx file in the App Router structure, dynamic routes with incorrectly named folder segments, middleware that blocks routes it should not, and environment-dependent redirects that differ between preview and production. V0 also sometimes creates a phantom /app directory at the root that conflicts with the actual app router structure.

• V0 creates navigation links to pages that do not have corresponding page.tsx files in the app directory
• Dynamic route folders are named incorrectly (e.g., :id instead of [id] in App Router convention)
• middleware.ts intercepts and redirects routes that should be public
• Environment variables differ between V0 preview, Vercel Preview, and Vercel Production
• V0 creates a phantom /app directory at root level that conflicts with the real app router structure

Error messages you might see

Before you start

• A V0 project deployed to Vercel where some routes return 404 or redirect incorrectly
• Access to the Vercel dashboard and deployment logs
• The V0 code editor or exported GitHub repository

How to fix it

// Link exists but no page file:
<Link href="/pricing">Pricing</Link>
// app/pricing/page.tsx does NOT exist → 404 on Vercel

// Create the missing page file:
// app/pricing/page.tsx
export default function PricingPage() {
  return (
    <div className="max-w-4xl mx-auto p-6">
      <h1 className="text-3xl font-bold">Pricing</h1>
      {/* Pricing content */}
    </div>
  )
}

app/
  products/
    :id/          ← Wrong: Express-style colon
      page.tsx
  blog/
    slug/         ← Wrong: no brackets
      page.tsx

app/
  products/
    [id]/          ← Correct: square brackets
      page.tsx
  blog/
    [slug]/        ← Correct: square brackets
      page.tsx

// middleware.ts — too broad, blocks everything
export const config = {
  matcher: "/:path*",  // Matches ALL routes including login
}

// middleware.ts — targeted matching
export const config = {
  matcher: [
    "/dashboard/:path*",
    "/settings/:path*",
    "/api/protected/:path*",
  ],
  // Explicitly excludes: /, /login, /signup, /api/auth/*, /api/webhooks/*
}

// Phantom directory conflict:
project-root/
  app/           ← Real app router
    page.tsx
  /app/          ← Phantom, created by V0 bug
    page.tsx     ← Conflicts with real app/

// Clean structure:
project-root/
  app/           ← Only one app directory
    page.tsx
    layout.tsx
    dashboard/
      page.tsx

Complete code example

1import { NextResponse } from "next/server"
2import type { NextRequest } from "next/server"
3
4// Routes that should never be intercepted by middleware
5const publicRoutes = [
6  "/",
7  "/login",
8  "/signup",
9  "/pricing",
10  "/about",
11  "/api/auth",
12  "/api/webhooks",
13]
14
15function isPublicRoute(pathname: string): boolean {
16  return publicRoutes.some(
17    (route) => pathname === route || pathname.startsWith(route + "/")
18  )
19}
20
21export function middleware(request: NextRequest) {
22  const { pathname } = request.nextUrl
23
24  // Skip middleware for public routes
25  if (isPublicRoute(pathname)) {
26    return NextResponse.next()
27  }
28
29  // Skip middleware for static assets
30  if (
31    pathname.startsWith("/_next") ||
32    pathname.startsWith("/favicon") ||
33    pathname.includes(".")
34  ) {
35    return NextResponse.next()
36  }
37
38  // Check auth for protected routes
39  const token = request.cookies.get("access_token")?.value
40
41  if (!token) {
42    const loginUrl = new URL("/login", request.url)
43    loginUrl.searchParams.set("redirect", pathname)
44    return NextResponse.redirect(loginUrl)
45  }
46
47  return NextResponse.next()
48}
49
50export const config = {
51  matcher: [
52    "/((?!_next/static|_next/image|favicon.ico).*)",
53  ],
54}

Best practices to prevent this

• Verify every navigation Link has a corresponding page.tsx in the app directory before deploying
• Use square brackets [param] for dynamic route segments — never colons or plain text
• Keep middleware.ts matchers narrow and explicitly exclude public routes, static assets, and API endpoints
• Set all environment variables in Vercel dashboard for both Production and Preview environments
• Test the Vercel Preview deployment from every V0 PR before merging to main
• Check for phantom /app directories that V0 may have created as a known bug
• Use Vercel's deployment logs and function logs to debug 500 errors that do not appear in V0 preview

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