The OG image was served with the sveltekit-og default Cache-Control: public, immutable, no-transform, max-age=31536000, so once a CDN or scraper fetched a card it never reflected later event edits (renamed event, new date, new thumbnail). Override the header with a short revalidating policy, add a weak ETag derived from the event record CID (with a content hash fallback when the CID is absent), and answer a matching If-None-Match with a bare 304 before rendering. Unchanged cards stay cheap and an edit reaches fresh scrapes in minutes instead of a year. Fixes flo-bit/atmo-events#41.