[BUG] Fullscreen mode: mouse wheel interpreted as arrow keys in Tabby + WSL2 (v2.1.173)

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?

In fullscreen rendering mode (/tui fullscreen or "tui": "fullscreen" in settings.json), mouse wheel scrolling is interpreted as arrow key events in Tabby terminal on WSL2. The scroll wheel does not scroll the conversation; instead, it triggers the "Scroll wheel is sending arrow keys · use PgUp/PgDn to scroll" warning message.

Diagnostic details:

| Input | Behavior |
|---|---|
| Mouse wheel | Interpreted as arrow keys, shows warning message |
| PgUp / PgDn | Works correctly |
| Standard mode (no fullscreen) | Mouse wheel works correctly |

This appears to be similar to #60789 (VS Code terminal + Windows), but affects a different terminal emulator (Tabby) on WSL2.

What Should Happen?

Mouse wheel scrolling should work the same way in fullscreen mode as it does in standard mode. The scroll wheel should scroll through the conversation history smoothly.

Steps to Reproduce

1. Launch Tabby terminal on Windows with WSL2
2. Start Claude Code: claude
3. Switch to fullscreen mode: /tui fullscreen
4. Try to scroll with the mouse wheel → observe warning message
5. Switch back to standard mode: /tui fullscreen (toggle)
6. Try to scroll with the mouse wheel → works correctly

Claude Code Version

v2.1.173

Platform

Anthropic API (via custom endpoint)

Operating System

Ubuntu on WSL2 (Kernel 6.6.87.2-microsoft-standard-WSL2)

Terminal/Shell

Tabby terminal (Windows host) + zsh (WSL2 guest)

Is this a regression?

I don't know

Additional Information

Environment details:

• TERM: xterm-256color
• Tabby is running on Windows 11, connecting to WSL2
• The issue only occurs in fullscreen mode (tui: "fullscreen")
• Standard mode works perfectly with mouse wheel scrolling

Related issues:

• #60789: Same symptom but in VS Code integrated terminal (Windows)
• This report adds Tabby + WSL2 as another affected environment

Workaround:

• Use standard mode (remove "tui": "fullscreen" from settings.json)
• Use PgUp/PgDn for keyboard scrolling in fullscreen mode