What
When Claude Code composes an automatic reply to a comment thread on an artifact (a generated piece of content like a webpage), it now fetches the current HTML of that artifact's page and includes it, truncated and marked as untrusted, in the prompt it uses to write the reply. A new check now catches and discards replies that simply echo that fenced content back instead of actually responding to it. Prompt caching is also conditionally enabled for this reply path.
Why
This grounds automatic replies in what the artifact page actually shows, rather than letting Claude guess, and prevents low-quality replies that just parrot the input back.