turbopack fails to resolve subpath imports in dynamic `import()` statements with a placeholder

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

Clone the linked reproducer, install with pnpm, and run its build command to confirm the dynamic import failure. Then trace Turbopack’s handling of the package.json #/* subpath alias and compare it with the working relative and TypeScript-alias cases; done means next build and next dev resolve the JSON import without the PackageInternal constant-string error.