[Self-Hosted] Media URLs hosted by the instance itself are not unfurled/embedded

Observed behaviour

On self-hosted instances if an uploaded media attachment's URL is copied and pasted, that media does not re-embed in the chat. This really often gets in the way of reposting favorited gifs/images.

Commit c01d22d attempted to fix this on Sept 4th, but this does not seem to have worked

Reproduction steps

1. upload a png/jpg attachment in a message
2. post the media URL of that attachment in the chat afterwards

Build information

Stable Web 2026.913.165053, Windows NT 10.0 (x64), Firefox 156.0, Locale en-US

Affected surface

Self-hosted instance

Instance

No response

Evidence

No response

Acknowledgements

• I searched open and closed issues.
• I removed secrets and unrelated personal data from the report.