I'm implementing PHBackgroundResourceUploadExtension to back up photos and videos to our cloud storage service. During testing, I observed that iCloud-optimized photos (where the full-resolution original is stored in iCloud, not on device) do not upload. The upload job appears to silently skip these assets. Questions: Is this behavior intentional/documented? I couldn't find explicit mention of this limitation. If the device only has the optimized/thumbnail version locally, does the system: - Automatically download the full-resolution asset from iCloud before uploading? - Skip the asset entirely? - Return an error via PHAssetResourceUploadJobChangeRequest? For a complete backup solution, should we: - Pre-fetch full-resolution assets using PHAssetResourceManager.requestData(for:options:) before creating upload jobs? - Use a hybrid approach (this extension for local assets + separate logic for iCloud-only assets)? Environment: iOS 26, Xcode 18

I'm implementing a PHBackgroundResourceUploadExtension to back up photos and videos from the user's library to our cloud storage service. Our existing upload infrastructure uses chunked uploads for large files (splitting videos into smaller byte ranges and uploading each chunk separately). This approach: Allows resumable uploads if interrupted Stays within server-side request size limits Provides granular progress tracking Looking at the PHAssetResourceUploadJobChangeRequest.createJob(destination:resource:) API, I don't see a way to specify byte ranges or create multiple jobs for chunks of the same resource. Questions: Does the system handle large files (1GB+) automatically under the hood, or is there a recommended maximum file size for a single upload job? Is there a supported pattern for chunked/resumable uploads, or should the destination URL endpoint handle the entire file in one request? If our server requires chunked uploads (e.g., BITS protocol with CreateSession → Fragment → CloseSession), is this extension the right mechanism, or should we use a different approach for large videos? Any guidance on best practices for large asset uploads would be greatly appreciated. Environment: iOS 26, Xcode 18

I'm developing a PHBackgroundResourceUploadExtension and finding it difficult to debug because the system controls when the extension launches. Current experience: The extension starts at unpredictable times (anywhere from 1 minute to several hours after photos are added) By the time I attach the debugger, the upload may have already completed or failed Breakpoints in init() or early lifecycle methods are often missed Questions: Is there a way to force-launch the extension during development (similar to how we can manually trigger Background App Refresh in Xcode)? Are there any launch arguments or environment variables that put the extension in a debug/eager mode? I tried taking photos/videos, but this doesn't trigged app extension in all cases. Any tips for improving the debug cycle would be greatly appreciated. Environment: iOS 26, Xcode 18