Environment

@nativescript/core 9.1.3 (pkg.pr.new runtime abae298/cbec98bb), packaged WinUI 3 MSIX (org.octanexplat.windows61), Windows 11 x64, {N} Windows runtime alpha.

Defects verified on the packaged runtime

packages/core/file-system/file-system-access.windows.js has two defect classes, verified at runtime (not source inspection):

1. Async methods invoked on the pending IAsyncOperation (E_FAIL)

deleteFile, deleteFolder, and rename call StorageFile.GetFileFromPathAsync(path) / StorageFolder.GetFolderFromPathAsync(path) synchronously, then invoke DeleteAsync()/RenameAsync() on the returned operation object rather than the resolved entity:

// deleteFile (windows):
StorageFile.GetFileFromPathAsync(path).DeleteAsync()  // pending op, not the file

Runtime result: File.remove() rejects Error: Unspecified error (HRESULT 0x80004005) and removeSync() silently swallows it — deletes never happen. Verified on MSIX 1.0.0.204/205/209/212; workaround is toPromise(GetFileFromPathAsync(path)) then toPromise(file.DeleteAsync()), which deletes correctly.

2. Fake-sync .done() pattern on a projection that only exposes then

• Folder.getEntities/eachEntity → StorageFolder.GetFolderFromPathAsync(...).done is not a function (the code calls op.done(...)).
• getFileSize → file.size silently returns 0.
• readTextSync/writeTextSync/readBufferSync/writeBufferSync → call .done() and return before completion, so sync reads always yield ''/undefined.
• File.lastModified resolves but the try/catch fallback can hide a real failure behind new Date().

Net working surface on the pinned runtime: File.exists, Folder.exists, path joins, and the real async text/buffer IO (readText/writeText/readBuffer/writeBuffer/appendText). Every delete, rename, enumeration, size, and sync-read member is broken or silent-wrong.

Happy to share the qualification fixture that produced the evidence.