Agent skill · software engineering · nexu-io
export-download-debugging
Diagnose and fix browser, preview, or Electron export/download failures, especially image export issues involving Save As, Blob/Data URLs, the File System Access API, createWritable failures, and 0 KB files.
Why this skill is useful
Provides detailed debugging procedures and validation steps for handling export/download failures in web applications, which the AI wouldn't reliably generate on its own.
What it needs
About 2k tokens when loaded. Last updated 2026-08-07. 84,236 stars on the source repository.
What this skill does
Export Download Debugging Use this when an export or download appears to run but produces an empty, missing, or unusable file. It is tuned for browser previews, iframe capture, and Electron shells. Core rule Separate capture from save. Prove the export payload has non-zero bytes before debugging the destination path. A 0 KB file often means the native picker or host created the target file, then the write failed or was blocked. Evidence Record the payload type, MIME type, byte length, object URL or data URL path, and thrown error name/message. Check browser console output and app logs around showSaveFilePicker, createWritable, <a download>, URL.createObjectURL, and URL revocation. In Electron, inspect the will-download path: filename, MIME, file extension, save dialog filters, cancellation, and final file size. Confirm the actual downloaded file size on disk and whether it opens in a normal image viewer. Fix order 1. Prepare and validate the export payload first; disable Save until bytes are available. 2. Prefer the simplest stable save channel for the host. If showSaveFilePicker().createWritable() fails, is sandboxed, or creates empty files, route to <a download> or Electron's download manager instead. 3. Avoid opening a native picker before the payload is ready. This prevents the host from creating an empty destination file on later write failure. 4. For PNG fallback, prefer a verified non-empty data URL when blob URLs, revocation timing, CSP, or iframe sandboxing are suspicious. 5. In Electron, add explicit Save As filters for exported image extensions (.png, .jpg, .jpeg, .webp) so users can choose a real image target. 6. Keep the UI restrained: format selection, filename/path hint, clear pending and error states, and one primary save action. Validation Add or update tests for non-empty payload preparation, fallback save behavior, file extension/MIME mapping, and UI disabled/error states. Run focused export tests, then pnpm --filter @open-design/web typecheck. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills nexu-io/export-download-debugging