Append one checksummed bounded export-file chunk

Chunk is durable and Upload-Offset advanced

The multipart shape or Idempotency-Key is malformed

The opaque credential is absent, ambiguous, malformed, expired, revoked, or invalid

The browser mutation did not originate from this application, or the authenticated member lacks the required permission

Duplicate content is disallowed, or an idempotency key was reused for a different request

A configured streaming body or per-file size limit was exceeded. A transport-level rejection may omit the JSON body.

Chunk checksum mismatch

A required core dependency is unavailable; retry with bounded backoff

/api/v1/paperless-imports/:import_id/files/:ordinal