Link to the code that reproduces this issue

https://github.com/stefanprobst/issue-turbopack-subpath-imports

To Reproduce

• clone repo
• pnpm install
• pnpn build

Current vs. Expected behavior

turbopack fails to resolve subpath imports (starting with #/*, configured in package.json) in dynamic import() statements with a placeholder, e.g.:

await import(`#/messages/${locale}/index.json`);

Error:

Error: Module not found: Can't resolve ('#/messages/' <dynamic> '/index.json' | '#/messages/en/index.json')
PackageInternal requests can only be Constant strings

Note that the same works fine when using either relative paths, or typescript path aliases, e.g.:

await import(`../../messages/${locale}/index.json`);
await import(`@/messages/${locale}/index.json`);

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #28~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jul  1 15:50:57 UTC 2
  Available memory (MB): 32035
  Available CPU cores: 4
Binaries:
  Node: 24.19.0
  npm: N/A
  Yarn: N/A
  pnpm: 11.20.0
Relevant Packages:
  next: 16.3.1-canary.21 // There is a newer canary version (16.3.1-canary.24) available, please upgrade! 
  eslint-config-next: N/A
  react: 19.2.8
  react-dom: 19.2.8
  typescript: 7.0.2
Next.js Config:
  output: N/A

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

Turbopack

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

next build (local), next dev (local)

Additional context

No response