When publishing an artifact fails because a file's content type isn't one Claude Code can serve, the error message is now far more detailed. It groups servable content types into categories such as pages, styles, scripts, data, images, fonts, media, and documents, lists which file extensions belong to each, and gives targeted advice, for example pointing out when a rejected type has a close servable alternative, or when the file extension is a recognized but unservable type.
Claude Code also now records refused_ext and refused_type details in its artifact_publish / file_not_servable telemetry event.
Instead of a bare rejection, users publishing an artifact now get concrete guidance on why a file's type isn't supported and what servable alternative to use instead.