[BUG] [Claude Desktop / macOS / Cowork] File card "Open in" label shows Microsoft Word for .md, although the OS default (and the actual open) is Cursor

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?

Routing note

This is Claude Desktop (Cowork mode) on macOS, not the Claude Code CLI. Filing here because Desktop has no public issue tracker (same as #95567, #72439).

What's wrong

When Claude presents a Markdown (.md) file as a file card in Cowork, the card's open button is labeled "Microsoft Word". The actual open action follows the macOS default handler and opens the file in Cursor. So only the label is wrong, but it misleads users about which app will open.

Until recently the label showed Cursor. It changed right after Microsoft Word updated to 16.113.2, which newly declares Markdown support (CFBundleDocumentTypes for md/markdown with LSHandlerRank "Default", plus an imported UTType "public.markdown").

Verified on the machine

• Launch Services default handler for net.daringfireball.markdown and public.markdown: Cursor (com.todesktop.230313mzl4w4u92)
• NSWorkspace URLForApplicationToOpenURL for a .md file: /Applications/Cursor.app
• Clicking the card's button: opens in Cursor (the Desktop main process calls shell.openPath via openSessionFileInDefaultApp)
• The label still says Microsoft Word, even after the handler was explicitly set to Cursor for both UTIs

What Should Happen?

The label should show the app that will actually open the file (the OS default handler), or offer a user-configurable choice (related: #72439).

Error Messages/Logs

None. No error is shown; only the button label is wrong.

Steps to Reproduce

1. macOS with Cursor set as the default app for .md
2. Install or update Microsoft Word to 16.113.2 or later
3. In Cowork, have Claude create a .md file and present it as a file card
4. Observe the button label: "Microsoft Word"
5. Click it: the file opens in Cursor

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Desktop 2.2553.13 (Cowork mode)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Environment

• Claude Desktop 2.2553.13 (Cowork mode)
• macOS 26 (Darwin 25.3.0), Apple Silicon
• Microsoft Word 16.113.2
• Cursor 3.21.18

Related

• #72439 Hardcoded "Open in..." app list doesn't respect OS default app
• #95567 Claude Desktop registers as default handler for .md without consent