[BUG] Claude design 503 error for all html files

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

503 in network tab with payload - Request URL https://65cba994-7e01-4a3d-81c2-86f39bb2e888.claudeusercontent.com/ Request Method HEAD Status Code 503 Service Unavailable Remote Address 160.79.104.10:443
the rendered page errors with message "unconditional drop overload"

<img width="1105" height="529" alt="Image" src="https://github.com/user-attachments/assets/361cdb52-0b6e-4204-8dbc-a5277d275016" />

What Should Happen?

I should preview html I generate

Error Messages/Logs

unconditional drop overload

Steps to Reproduce

minimal repro - disable all my design systems; start new claude design project / page (with prompt: "create an empty page with Hello World"); claude design failed to render HTML page.
try download the above page html, the html is correctly rendered in native chrome
Observed error:

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.0.123

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_