Under the hood
Artifact requests now also accept a new 'frame-refusal' response format from the server
What
Requests related to publishing artifacts (generated files or documents Claude Code sends to a server) now include a new content type, application/vnd.ant.frame-refusal+json, in their Accept header alongside the existing application/json.
Why
This lets the server respond with a distinct, structured format specifically for refusals when it can't fulfill an artifact request, rather than only plain JSON.