[BUG] File pane fails to open files with Cyrillic characters in path ("File could not be read")

Summary

When clicking a file path in the chat that contains Cyrillic (non-ASCII) characters, the File pane in the Desktop app displays:

"File could not be read. It may have been deleted or moved, or it lives outside the session folder."

even though the file exists on disk, the project folder of the session is correctly set to an ancestor directory, and the same File pane successfully opens files in the same session when their paths contain only ASCII characters.

Reproduction

1. Create a file with Cyrillic characters in both directory and filename, e.g.:

/Users/USER/Documents/cc/personal/blog/ии-в-файлах/ролик-4-desktop-vs-cli.md

1. Start a Claude Code Desktop session with /Users/USER/Documents/cc as project folder.
2. Have Claude create or reference the file via a relative markdown link in the chat.
3. Click the markdown link in the chat.

Expected: file opens in the File pane.
Actual: File pane shows "File could not be read..." error.

Verification that it is a Cyrillic-specific issue

• File exists on disk, readable via shell (cat works, 343 lines, 28987 bytes)
• Read tool in the same session reads the same file correctly
• Session project folder is correctly set to /Users/USER/Documents/cc
• A markdown file in the same session with ASCII-only path opens in File pane correctly (e.g. personal/blog/hAIperfocus-brand.md)
• Switching only the filename from Cyrillic to Latin fixes the issue

Suspected cause

Likely Unicode normalization mismatch (NFC vs NFD) in Electron path resolution on macOS, where HFS+/APFS stores filenames in decomposed form but the File pane may look them up in composed form or vice versa. May be related to #30244 (lossy path normalization) and #45718 (project path encoding), but affects a different component (File pane, not session resume).

Environment

• Claude Desktop: 1.3561.0
• Claude Code CLI: 2.1.116
• macOS: 26.3.1 (Apple Silicon)
• Locale: ru_RU.UTF-8

Workarounds

• Open file via right-click → "Open in" → Obsidian / VS Code → works
• Ask Claude to Read the file — content shown in chat
• Rename files to ASCII — works but defeats multilingual workflows (common for Russian / Ukrainian / Greek / etc. users using Obsidian-style vaults)