The previous fix only guarded domAppend/domInsertAfter, but many platform JS functions (asyncRenderChildren, asyncRenderElement, asyncRenderMap, render, sxRenderWithEnv) call appendChild directly. Add _spread guards to all direct appendChild sites. For async element rendering, merge spread attrs onto parent (class/style join, others overwrite) matching the sync adapter behavior. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>