Also receiving this error on a dataset the same size as ones uploaded in the last 2 weeks without issue.
Topic summary
Issue: Bulk item file uploads via staged links return “Bad Request: Metadata part is too large,” disrupting previously successful workflows. Errors occur intermittently—smaller batches may succeed before failing again.
Context: Multiple users report new occurrences on datasets similar in size to recent successful uploads. Some suspect problems since Shopify’s storage backend change to Google Cloud Storage, though this is not confirmed.
Proposed fix: Specify an explicit file name in the multipart/form-data (FormData) upload. References provided: Stack Overflow guidance and MDN FormData docs.
Outcome: The file name fix resolved the error for at least one participant. However, the original reporter already includes file names, so the fix did not help in their case.
Workarounds: The original reporter shifted from bulk updates to single updates to avoid failures. Another participant is building a custom staged upload directly on Google Cloud Storage to improve control and debugging.
Status: No definitive root cause identified; partial workarounds exist. Open questions include why bulk uploads exceed metadata limits despite proper file naming and whether Shopify will document/stabilize staged uploads.