Embedded Browser pane shows blank content even though the page loads fine

What happened

The built-in Browser pane (the new in-app browser feature) showed a completely blank/empty pane on my screen, even though the page it was pointed at was working correctly.

Steps to reproduce

1. Start a local static file server (via .claude/launch.json + the preview tool).
2. Open a self-contained HTML file (plain HTML/CSS/JS, no build step) in the Browser pane.
3. The pane shows blank/dark, no visible content.

What I checked to rule out an actual page bug

• Network requests for the page and its JSON data all returned 200 OK.
• No errors in the console.
• Reading the page's DOM (accessibility tree) showed all expected content present and correct.
• A screenshot taken via the Claude tool itself showed the page rendering correctly.
• Opening the exact same URL in my regular Chrome browser rendered the page perfectly.

Troubleshooting already tried (none fixed it)

• Reloading the same tab.
• Closing the tab and opening a brand new one.
• Fully restarting the Claude Code desktop app and starting a new browser session.

The problem persisted across all of these. Only opening the URL in a completely separate, regular browser worked.

Expected behavior

The embedded Browser pane should render the same content that (a) network/DOM inspection confirms is present, and (b) a regular browser confirms renders correctly.

Environment

• Platform: macOS (Darwin 24.6.0)
• Claude Code desktop app, "Claude now has a browser" feature (marked "New" in the UI)