db0b083a3e
Synapse's thumbnail endpoint returns 400 Bad Request when the allow_redirect=true query parameter is present (added by matrix-js-sdk 41.x for authenticated media). Default allowRedirects to false in our mxcUrlToHttp wrapper so the parameter is never appended. Also extend the downloadMedia legacy-URL fallback to cover 400 in addition to 401, catching any encrypted-media fetches that still carry the old URL shape after a cache refresh. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>