[BUG] Preview tool screenshot always returns black image after browser gets into broken state

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?

The preview tool's internal browser gets stuck and screenshots always return a completely black image. Even when the server is running and window.location.href shows the correct localhost URL, the screenshot capture is broken.

<img width="651" height="1120" alt="Image" src="https://github.com/user-attachments/assets/e4c5ca52-f77e-4814-912a-c21eef79abaf" />

What Should Happen?

Screenshots should show the actual rendered app.

Error Messages/Logs

chrome-error://chromewebdata/ — the internal browser gets stuck on this URL and cannot navigate to localhost.

Steps to Reproduce

Start a Vite dev server via preview_start
The internal browser fails to load localhost (stuck on chrome-error://chromewebdata/)
Navigate via preview_eval → location.href shows the correct URL
Call preview_screenshot → returns completely black image
Restarting Mac does not fix it within the same Claude Code session

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

4.6

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_