[BUG] /copy command mangles UTF-8/Unicode characters in WSL

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?

Description

The native /copy command in Claude Code mangles UTF-8/Unicode characters when running in WSL (Windows Subsystem for Linux). It appears to use clip.exe under the hood, which does not handle UTF-8 encoding properly.

Steps to Reproduce

1. Run Claude Code in WSL
2. Have Claude output text containing Unicode characters (e.g., emoji, CJK, Arabic, math symbols, accented characters)
3. Run /copy
4. Paste the clipboard contents

Expected Behavior

All characters should be preserved correctly in the clipboard.

Actual Behavior

Non-ASCII characters are garbled. For example:

| Original | Copied |
|---|---|
| cafe resumer | café résumé |
| 🎉 🚀 💻 | ≡ƒÄë ≡ƒÜÇ ≡ƒÆ╗ |
| こんにちは世界 | πüôπéôπü½πüíπü»Σ╕ûτòî |
| € £ ¥ ₹ | Γé¼ ┬ú ┬Ñ Γé╣ |
| — – … | ΓÇö ΓÇô ΓǪ |

Workaround

Using PowerShell with explicit UTF-8 encoding works correctly:

powershell.exe -NoProfile -Command "Set-Clipboard (Get-Content -Raw -Encoding UTF8 \"$(wslpath -w /path/to/file)\")"

Environment

• Platform: WSL2 (Linux 6.6.87.2-microsoft-standard-WSL2)
• Shell: zsh

What Should Happen?

All characters should be copied to the clipboard exactly as displayed in the terminal, preserving Unicode/UTF-8 encoding.

Error Messages/Logs

Steps to Reproduce

1. Run Claude Code v2.1.45 in WSL2
2. Ask Claude to output text with Unicode characters (emoji, CJK, accented characters, math symbols, etc.)
3. Run /copy
4. Paste the clipboard contents somewhere (e.g., a text editor)
5. Observe that non-ASCII characters are garbled

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.45

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Windows Terminal

Additional Information

_No response_