[BUG] When terminal sends Focus In/Out events (DECSET 1004), [ I / [ O appear in input. Expected: handled/ignored.

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?

<img width="167" height="102" alt="Image" src="https://github.com/user-attachments/assets/af04673a-ed6f-488e-86ce-bc0b9d6e43c6" />

When I blur the terminal pane (WezTerm), [O shows up in the input; when I focus the terminal pane (WezTerm), [I shows up in the input. These two reporting are activated when there are multiple terminal panes in the same tab on WezTerm.

What Should Happen?

These two events should be handled gracefully by Claude Code. It could also be explored as user behavioral metrics.

Error Messages/Logs

Steps to Reproduce

1. Open WezTerm
2. Run claude
3. Split the tab window using Shift + Ctrl + Alt + %
4. Use Shift + Ctrl + Arrow Keys to jump between the two windows, or simply click around with mouse
5. See focus event characters pop up in Claude Code input box

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.36

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_