[BUG] Desktop app missing slash commands available in CLI (/btw, /compact, /diff, etc.)

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?

The Claude Code Desktop app is missing many slash commands that work in the CLI (TUI). Typing / in the Desktop app shows a reduced set of commands compared to the CLI. Commands like /btw, /compact, /diff, /branch, /effort, /security-review, and others are available in the TUI but not in the Desktop app.

Previously reported in #24873, #18811, #15301, #10294 — all were auto-closed by the duplicate/stale bot without any human response from the team.

Expected Behavior

All slash commands available in the CLI should also be available in the Desktop app, since they share the same core engine.

How to Reproduce

1. Open Claude Code Desktop app (macOS)
2. Type / to see available slash commands
3. Compare to running claude in terminal and typing /
4. Desktop app is missing many commands

CLI version

Latest (TUI has full slash command support)

Desktop app version

Latest (missing commands)

Operating System

macOS