[BUG] AltGr characters (€, @) broken in WSL2: Ctrl+Alt synthesis conflicts with TUI readline shortcuts

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?

AltGr-based characters (e.g. € via AltGr+E, @ via AltGr+Q on German/European layouts) cannot be typed in the Claude Code input prompt when running inside WSL2 on Windows Terminal.

The same characters work correctly:

• In plain bash in the same WSL2 session
• In any other terminal application

Root Cause

Windows internally represents AltGr as Ctrl + Alt (a synthetic key combination). The key event reaching Claude Code's Ink-based TUI therefore carries both the Ctrl and Alt modifiers alongside the character key.

Claude Code's TUI processes the Ctrl part first as a readline-style shortcut:

| AltGr combo | Intended char | Ctrl shortcut fired |
|---|---|---|
| AltGr+E | € | Ctrl+E → move-to-end-of-line |
| AltGr+Q | @ | Ctrl+Q → XOFF / quit |

The Alt modifier is then left dangling or ignored. The character is never inserted.

Bash/readline avoids this because it has explicit AltGr-awareness and strips the synthetic Ctrl before routing the key. Claude Code's Ink TUI does not.

What Should Happen?

When the TUI receives Ctrl+Alt+<key>, it should detect this as an AltGr sequence (on Windows/WSL) and not dispatch the Ctrl+<key> readline binding. The composed character should be inserted instead.

Environment

• OS: Windows 11 + WSL2 (kernel 5.15.153.1-microsoft-standard-WSL2)
• Terminal: Windows Terminal
• Keyboard layout: German / European (AltGr used for €, @, [, ], {, }, \, etc.)
• Claude Code version: latest

Workarounds

1. Ctrl+Shift+U → type Unicode codepoint → Enter (e.g. 20ac for €)
2. Type the character in another app and paste with Ctrl+Shift+V
3. stty -ixon in .bashrc frees Ctrl+Q, but does not fix the interception inside Claude Code

Related Issues

• #42523 — @ sign broken on Nordic layout in WSL2 (same root cause, narrower scope)
• #53451 — AltGr broken on native Windows / ConPTY
• #18221 — Alt/Option shortcuts break international layouts (closed stale)