Occasional garbled Chinese characters in streaming output

Description

When Claude Code streams responses containing Chinese text, occasionally a few characters appear garbled/mojibake (e.g., "看下���果" instead of "看下效果") while all surrounding characters render correctly.

Environment

• Claude Code CLI (macOS)
• Terminal: default zsh
• Model: claude-opus-4-6

Root cause hypothesis

UTF-8 Chinese characters are 3 bytes each. When the streaming response chunks happen to split at a byte boundary within a multi-byte character, the terminal renders the incomplete bytes as replacement characters (�).

Reproduction

• Not reliably reproducible — it's a race condition dependent on where chunk boundaries fall
• Happens occasionally in longer responses mixing Chinese and ASCII text
• Only a few characters are affected per occurrence, not entire lines

Expected behavior

All multi-byte characters should be buffered correctly before rendering, regardless of chunk boundaries.