Issue Summary

After auto-conversion Phase 2 (legacy editor deprecation), file attachments on Confluence Cloud pages fail to (inline) preview and display the error message "We couldn't load the file." This affects sites that were migrated from Confluence Server or Data Center to Cloud and was solved on CONFCLOUD-84110, but the unkown file download remains

Steps to Reproduce

1. Navigate to a Confluence Cloud page with file attachments that has been through auto-conversion Phase 2.
2. Attempt to view the inline file preview of any attached document.
3. download it.

Expected Results

The file downloa successfully and the attachment is viewable inline on the Confluence page.

Actual Results

The file download fails and is downloaded with "Unkown" file name

Root Cause

During migration from Confluence Server/Data Center to Cloud, the filename metadata for some attachments was not correctly recorded in the underlying media storage service. Before auto-conversion Phase 2, this was not visible to users because the old editor read attachment information directly from Confluence's own database. After conversion, inline file attachments retrieve their metadata from the media storage service directly — where the filename is missing — causing the preview to fail.

The attachment files themselves are intact and accessible (they are visible on the page's attachment list and can be downloaded normally).

Workaround

Download the affected attachment and re-upload it to the page. This will correctly register the filename in the media storage service and restore inline preview functionality.

Fix

A backend fix is being investigated to retroactively correct the missing filename metadata for affected attachments without requiring users to re-upload files.