[BUG] chat:undo (ctrl+_/ctrl+-) exits Claude Code and closes terminal

Environment

• Platform: Anthropic API
• Claude CLI version: 2.1.42
• Operating System: Linux 6.12 (Debian), GNOME/Wayland
• Terminal: Ghostty 1.1.3

Bug Description

Pressing ctrl+- while in Claude Code's chat input causes Claude Code to exit entirely, which closes the terminal window. On most terminals, ctrl+- produces the same character as ctrl+_ (ASCII 0x1F), which is bound to chat:undo by default.

The expected behavior of chat:undo is to rewind the conversation. Instead, it appears to exit the Claude Code process, causing the terminal to close.

This does not happen in a plain shell — ctrl+- correctly triggers Ghostty's decrease_font_size binding. It only occurs when Claude Code is running and intercepts the keypress.

Steps to Reproduce

1. Open Ghostty (or any terminal where ctrl+- sends ctrl+_)
2. Start Claude Code (claude)
3. Press ctrl+- while in the chat input
4. Claude Code exits and the terminal window closes

Expected Behavior

chat:undo should rewind the conversation, or do nothing if there's nothing to undo. It should never exit the process.

Actual Behavior

Claude Code exits, closing the terminal window. No crash — clean exit (no core dump).

Workaround

Unbind ctrl+_ in ~/.claude/keybindings.json:

{
  "bindings": [
    {
      "context": "Chat",
      "bindings": {
        "ctrl+_": null
      }
    }
  ]
}