[BUG] MultiEdit UTF-8 Encoding Bug Report

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x] Other: Claude Code CLI with MultiEdit tool
• Claude CLI version: 1.0.24 (Claude Code)
• Operating System: Linux (root@build) Alpine Linux ^3.22.0
• Terminal: Fish Shell 4.0.2+

Bug Description

The MultiEdit tool incorrectly handles UTF-8 encoded content when writing files, resulting in corrupted characters (mojibake). Chinese characters and special UTF-8 symbols are replaced with replacement characters (�) in the written files, while the same content displays correctly in the Claude interface.

Steps to Reproduce

1. Use Claude Code to create a new markdown file with Chinese content:

``
MultiEdit prompt/skeleton 3.1.3.md
``

1. Include Chinese characters in the content, such as:

• "骨架屏" (skeleton screen)
• "中文文档" (Chinese documentation)
• Special characters like "—" (em dash) or "•" (bullet)

1. Save the file using MultiEdit
2. Read the file back using:

``
Read prompt/skeleton 3.1.3.md
``

Expected Behavior

• File should be saved with proper UTF-8 encoding
• Chinese characters and special symbols should be preserved
• Reading the file should display the same content that was written

Actual Behavior

• Chinese characters are replaced with � (replacement character)
• Special UTF-8 characters are corrupted
• File content shows mojibake when read back
• Example: "骨架屏" becomes "��架��"

Additional Context

Test Case Evidence:

• Claude interface displays: "骨架屏（Skeleton Screen）"
• File contains: "��架��（Skeleton Screen）"

System Encoding:

$ echo $LANG
en_US.UTF-8

File Encoding Check:

$ file -bi "prompt/skeleton 3.1.3.md"
text/plain; charset=utf-8

Workaround:
Currently avoiding Chinese characters and using only ASCII in documentation files.

Impact:
This bug prevents creating multilingual documentation or using special UTF-8 characters through Claude Code's MultiEdit tool, limiting its usefulness for international users and technical documentation that requires special symbols.

Suggested Fix:
Ensure MultiEdit tool explicitly uses UTF-8 encoding when writing files, possibly by:

• Setting encoding explicitly in file write operations
• Using Buffer.from(content, 'utf8') when handling string content
• Ensuring all string transformations preserve UTF-8 encoding