Hi Guys!

I’m deploying a Next.js 14 app to Railway from a monorepo setup:

/root
  /frontend  ← Next.js app
  /backend   ← separate API

I’ve tried two approaches and both fail:

1. Using railway.toml in the monorepo root

[build]
builder = "NIXPACKS"
buildPath = "frontend"
buildCommand = "cd frontend && npm install && npm run build"

[start]
runDir = "frontend"
cmd = "npm run start"

But the build fails with errors like:

Module not found: Can't resolve '@/lib/navigation'

This happens for any alias imports like @/lib/api, even though everything works locally.

My frontend/tsconfig.json includes:

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}

2. Deploying from the frontend/ folder directly, using Docker

I set the Railway project root to frontend/, added a custom Dockerfile, and still ran into the same module resolution issue with the @ alias.

Everything works fine locally — the issue only happens during Railway builds.

Question:

How can I get Railway (with Nixpacks or Docker) to correctly resolve @ aliases in a monorepo Next.js project?

Any working example or guidance would be appreciated.

Thanks!!