Assets url resolution in CSS is different between build and dev (Turbopack)

[cavez86]

Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/recursing-murdock-stq8td

To Reproduce

1. Import a CSS/SCSS containing a url('~@/path/to/asset.svg') (eg a background-image)
2. Start the application in dev mode (with Turbopack)
3. See the error even if the assets exists
4. Remove the ~
5. Dev mode works but build breaks

Current vs. Expected behavior

Turbopack supports only url('@/path/to/asset.svg') syntax.
Otherwise returns error Module not found: Can't resolve '~@/path/to/asset.svg'

Webpack supports only url('~@/path/to/asset.svg') syntax.
Otherwise returns error Module not found: Can't resolve './@/path/to/asset.svg'

A possible workaround is to set in next.config.ts

  experimental: {
    turbo: {
      resolveAlias: {
        '~@/*': '@/*',
      },
    },
  },

and use ~@ syntax.

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32449
  Available CPU cores: 8
Binaries:
  Node: 22.11.0
  npm: 10.9.0
  Yarn: 3.6.1
  pnpm: 10.2.1
Relevant Packages:
  next: 15.1.7 // Latest available version is detected (15.1.7).
  eslint-config-next: 15.1.7
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.7.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

CSS

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

No response

[samcx]

@cavez86 This works fine if you just adjust the paths config in your tsconfig.json.

    "paths": {
      "~@/*": ["./*"]
    }

[cavez86]

@cavez86 This works fine if you just adjust the paths config in your tsconfig.json.

    "paths": {
      "~@/*": ["./*"]
    }

Ok, but shouldn't the same format be supported in dev and build mode by default?

[samcx]

Ok, but shouldn't the same format be supported in dev and build mode by default?

Hmm, I would expect it to not work at all (equally in dev and build) unless explicitly set.