[BUG] Numpad keys display raw CSI u escape sequences instead of characters

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:

• Terminal: iTerm2
• OS: macOS
• Claude Code version: 2.1.1

Bug Description:
When using numpad keys inside Claude Code, raw CSI u (kitty keyboard protocol) escape sequences are displayed instead of the expected characters.

Examples:

• Numpad / shows [57410u
• Numpad 1 shows [57401u
• All numpad keys appear affected

Expected behavior:
Numpad keys should produce the same characters as their main keyboard equivalents.

Actual behavior:
Raw escape sequences are printed to the input.

Notes:

• This does NOT happen in iTerm2 directly, only inside Claude Code
• Suggests Claude Code is enabling CSI u protocol but not handling numpad key codes

What Should Happen?

Numpad keys should produce the same characters as their main keyboard equivalents.

Error Messages/Logs

Steps to Reproduce

Open claude, use numpad keys, see weird codes showing up; see screenshot

<img width="1141" height="161" alt="Image" src="https://github.com/user-attachments/assets/8accf3b5-70c5-4fcd-8ee9-076759706d67" />

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.1

Platform

Google Vertex AI

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

_No response_