Backup with attachments fails with "Error building backup file" after lazy S3 stream change

Description

Backup with attachments fails during the ZIP compression stage with "Error building backup file" error. The backup completes issue export (reaches 20-50% progress) but crashes when building the final backup file.

Backups without attachments succeed.

How to reproduce

1. Navigate to Jira Settings > Marketplace apps > Backup (under Xray)
2. Check the "With attachments" option
3. Click Create Backup

Actual result/Attachments

Backup fails with error "Error building backup file". The /api/internal/export/issues/status endpoint returns HTTP 200 with job status "failed" and the file object reports non-existent. Grafana logs show the job running to 20% progress, uploading S3 metadata files, but then failing during the ZIP compression step.

Expected result

Backup should complete successfully and produce a downloadable ZIP file containing issues and their attachments.

Version

Xray Cloud (regressed in 12.0.0; known working in 11.0.0)

Workaround

Create backups without the "With attachments" option as a temporary workaround.