apply() read the [data-open-slug] marker off the parsed doc after replaceWith() had already reparented #content (and the marker) into the live document, so openSlug came back null and the plate viewer never opened. Read it off the newContent node instead, before the swap. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016h9VwM3YfMpDxaP8KzXcaR