[BUG] File viewer fails to open files with non-ASCII (Japanese) filenames on Windows

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 Claude Code outputs a file link in the chat response and the filename contains non-ASCII characters (e.g. Japanese), clicking the link opens the right-side file viewer panel but shows an error instead of the file contents.

The file exists on disk and can be verified through the OS file explorer or other applications. Files with ASCII-only filenames in the same directory open correctly in the viewer.

Environment: Claude Code desktop app on Windows 11, project folder contains files with Japanese filenames.

What Should Happen?

Clicking a file link with a non-ASCII (Japanese) filename in Claude Code's chat response should open the file correctly in the right-side viewer panel, the same way ASCII-named files do.

Error Messages/Logs

Error shown in the right-side file viewer panel (UI message, not a terminal error):
"File could not be loaded. It may have been deleted or moved, or it may be outside the session folder."
(Original Japanese UI text: ファイルを読み込めませんでした。削除または移動されたか、セッションフォルダーの外にある可能性があります。)

Steps to Reproduce

1. Open Claude Code desktop app on Windows 11
2. Open a project that contains files with non-ASCII (Japanese) filenames
3. Ask Claude to create or reference one of those files (e.g. a Markdown file with a Japanese name)
4. In Claude's response, click the file link that appears in the chat
5. The right-side file viewer panel opens but shows an error instead of the file contents

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.70 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_