[BUG] File preview split-panel no longer opens when clicking file links in chat

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?

Environment

• OS: Windows 11 Pro (10.0.26200)
• App: Claude Desktop
• App version: [please fill in — Settings/About]
• Claude Code CLI version (if relevant): [please fill in]

Expected behavior
Previously, when Claude Code output a message containing a markdown link to a local file (e.g. [foo.ts](path/to/foo.ts)), clicking that link would split the main window: the chat conversation stayed on the left, and a preview panel showing the file's content opened on the right.

Actual behavior
Clicking the same kind of file link no longer opens the preview panel at all — nothing happens.

Steps to reproduce

1. Ask Claude Code to reference any local file so it outputs a markdown link to it.
2. Click the link in the chat.
3. Expected: split-panel view opens with file content on the right.
4. Actual: no panel opens, no visible response to the click.

Troubleshooting already tried

• Confirmed the target file exists and is readable (verified independently via the CLI's file tools).
• Tested with a link to a file with a simple ASCII filename (no spaces/diacritics) — same failure.
• Restarted the application.
• No obvious related toggle found in visible app Settings.

Additional notes
This appears to be an app-level regression rather than an issue with the file path or link formatting, since simple ASCII filenames fail the same way as filenames with spaces/Vietnamese diacritics.

What Should Happen?

Previously, when Claude Code output a message containing a markdown link to a local file (e.g. [foo.ts](path/to/foo.ts)), clicking that link would split the main window: the chat conversation stayed on the left, and a preview panel showing the file's content opened on the right.

Error Messages/Logs

Steps to Reproduce

1. Ask Claude Code to reference any local file so it outputs a markdown link to it.
2. Click the link in the chat.
3. Expected: split-panel view opens with file content on the right.
4. Actual: no panel opens, no visible response to the click.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.24012.1.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_