[BUG] Claude chrome extension cannot execute javascript_tool, computer actions, or screenshots on pages with about:blank iframes

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?

When a web application uses about:blank sub-frames (e.g., about:blank?viewId=logout), the following MCP tools fail with a permissions error: - javascript_tool - computer (screenshot, left_click, key, type)

Tools that DO work on the same page:

• read_page (full DOM/accessibility tree traversal)
• find (element search)
• form_input (can set values on elements)
• scroll_to (can scroll to elements by ref)
• navigate
• read_console_messages
• read_network_requests

This indicates the working tools use CDP (Chrome DevTools Protocol) while the broken tools use content script injection, which Chrome blocks when any iframe has an about:blank origin not listed in the extension manifest.

Suggested fix:

• Add about:blank to the extension's manifest host_permissions
• OR: catch the permission error on inaccessible frames and continue operating on accessible frames
• OR: add a frame parameter to javascript_tool and computer to target a specific frame context

Environment:

• Windows 11 Enterprise 10.0.26200
• Chrome (latest)
• Claude Code with Claude in Chrome MCP

What Should Happen?

Expected behavior:
All tools should work, or at minimum javascript_tool and computer actions should target the main frame and ignore inaccessible about:blank sub-frames.

Error Messages/Logs

Error message:
  Cannot access contents of url "about:blank?viewId=logout".
  Extension manifest must request permission to access this host.

Steps to Reproduce

Steps to reproduce:

1. Navigate to any web application that includes about:blank iframes in its frame structure (common in enterprise apps with multi-frame layouts)
2. Try javascript_tool to run document.title — fails
3. Try computer(action="screenshot") — fails
4. Try computer(action="left_click", ref="ref_X") — fails
5. Try read_page — succeeds, full DOM visible

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.62 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_