Deploying nextjs turbopack application returns 404 error

I have a Next.js 15 application that builds successfully on AWS Amplify but returns a 404 error when accessing the deployed site. The build completes without errors, but the homepage and other routes are not accessible.

Project Structure

frontend/feedal/
├── apps/
│   ├── landing/ # Landing page app
│   └── web/ # Main dashboard app (this one has the issue)
│       ├── app/
│       │   ├── (dashboard)/
│       │   │   ├── forms/
│       │   │   │   └──── page.tsx
│       │   │   ├── account/
│       │   │   ├── new/
│       │   │   └── layout.tsx
│       │   ├── layout.tsx
│       │   └── page.tsx # ← This was missing initially
│       ├── components/
│       ├── public/
│       └── package.json
├── packages/
│   ├── ui/
│   └── eslint-config/
├── package.json
├── turbo.json
└── amplify.yml

Build Configuration

amplify.yml:

version: 1
applications:
  - frontend:
      phases:
        preBuild:
          commands:
            - npm install -g pnpm
            - pnpm install
        build:
          commands:
            - pnpm run build
            - pwd
            - ls -la
      artifacts:
        baseDirectory: .next
        files:
          - "**/*"
      cache:
        paths:
          - node_modules/**/*
    appRoot: frontend/feedal/apps/web

apps/web/next.config.ts:

import { withSentryConfig } from "@sentry/nextjs";
import type { NextConfig } from "next";

const apiHost = process.env.NEXT_PUBLIC_API_HOST;

const nextConfig: NextConfig = {
  // Your existing Next.js configuration
  transpilePackages: ["@workspace/ui"],
  output: undefined,
  images: {
    remotePatterns: [
      new URL(`${apiHost}/**`),
    ],
  },
};

// Make sure adding Sentry options is the last code to run before exporting
export default withSentryConfig(nextConfig, {
  org: "org",
  project: "org-frontend",

  // Only print logs for uploading source maps in CI
  silent: !process.env.CI,

  // Upload a larger set of source maps for prettier stack traces (increases build time)
  widenClientFileUpload: true,

  // Route browser requests to Sentry through a Next.js rewrite to circumvent ad-blockers.
  tunnelRoute: "/monitoring",

  // Automatically tree-shake Sentry logger statements to reduce bundle size
  disableLogger: true,

  // Enables automatic instrumentation of Vercel Cron Monitors.
  automaticVercelMonitors: true,
});

.npmrc

node-linker=hoisted

I output of pwd and ls -la in the amplify.yml file is

# Executing command: pwd
   /codebuild/output/src2944845910/src/feedal-app/frontend/feedal/apps/web
# Executing command: ls -la
total 68
drwxr-xr-x 13 amplify amplify 4096 Aug  7 07:35 .
drwxr-xr-x  4 amplify amplify   32 Aug  7 07:35 ..
-rw-r--r--  1 amplify amplify  939 Aug  7 07:35 .env.sentry-build-plugin
drwxr-xr-x  8 amplify amplify 4096 Aug  7 07:38 .next
-rwxrwxrwx  1 amplify amplify 1495 Aug  7 07:35 amplify.sh
drwxr-xr-x  7 amplify amplify  252 Aug  7 07:35 app
drwxr-xr-x 17 amplify amplify 4096 Aug  7 07:35 components
-rw-r--r--  1 amplify amplify  455 Aug  7 07:35 components.json
drwxr-xr-x  2 amplify amplify  120 Aug  7 07:35 context
-rw-r--r--  1 amplify amplify  139 Aug  7 07:35 eslint.config.js
drwxr-xr-x  2 amplify amplify  290 Aug  7 07:35 hooks
-rw-r--r--  1 amplify amplify 1225 Aug  7 07:35 instrumentation-client.ts
-rw-r--r--  1 amplify amplify  326 Aug  7 07:35 instrumentation.ts
drwxr-xr-x  2 amplify amplify  169 Aug  7 07:35 lib
drwxr-xr-x  2 amplify amplify  287 Aug  7 07:35 models
-rw-r--r--  1 amplify amplify  211 Aug  7 07:35 next-env.d.ts
-rw-r--r--  1 amplify amplify 1934 Aug  7 07:35 next.config.ts
drwxr-xr-x  3 amplify amplify   24 Aug  7 07:35 node_modules
-rw-r--r--  1 amplify amplify 1902 Aug  7 07:35 package.json
-rw-r--r--  1 amplify amplify   55 Aug  7 07:35 postcss.config.mjs
drwxr-xr-x  6 amplify amplify  239 Aug  7 07:35 public
-rw-r--r--  1 amplify amplify  860 Aug  7 07:35 sentry.edge.config.ts
-rw-r--r--  1 amplify amplify  705 Aug  7 07:35 sentry.server.config.ts
drwxr-xr-x  2 amplify amplify 4096 Aug  7 07:35 services
drwxr-xr-x  2 amplify amplify  115 Aug  7 07:35 styles
-rw-r--r--  1 amplify amplify  418 Aug  7 07:35 tsconfig.json

When built locally, the hierarchy of the .next directory in the turbopack project is

What I've Tried

1. Verified build success: The build completes successfully with all pages generated
2. Checked file structure: All expected files are present in the build output
3. Tested locally: The app runs fine locally with pnpm run dev and pnpm run start
4. Verified routing: All routes work correctly in development
5. Checked Amplify logs: No errors in build or deployment logs

Build Output

The build shows successful compilation:

✓ Compiled successfully in 47s
✓ Linting and checking validity of types
✓ Collecting page data
✓ Generating static pages (39/39)
✓ Collecting build traces
✓ Finalizing page optimization
Route (app) Size First Load JS
┌ ○ / 359 B 216 kB
├ ○ /forms 8.36 kB 350 kB
├ ○ /account 9.72 kB 283 kB
└ ... (other routes)

Environment Details

• Next.js: 15.4.5
• Node.js: 18.x (Amplify default)
• Package Manager: pnpm
• Monorepo: Turborepo
• Deployment: AWS Amplify
• App Router: Yes (using app/ directory)

Questions

1. What could cause a 404 error when the build is successful and all files are present?
2. Is there a specific configuration needed for Next.js 15 on Amplify?
3. Could the monorepo structure be causing routing issues?
4. Are there any Amplify-specific settings I should check?

Additional Context

• The app uses Next.js App Router with route groups (dashboard)
• It's part of a monorepo with multiple apps
• The build artifacts include the .next directory and public folder
• All environment variables are properly configured