East Asian Ambiguous width characters (e.g. ⚪︎ U+26AA) rendered at half-width in input area

Description

Certain Unicode characters with East Asian Ambiguous width (e.g. ⚪︎ U+26AA) are displayed at half-width in the Claude Code input area, causing them to appear "squished" — as if the full-width glyph is being crammed into a half-width cell.

The terminal emulator (Ghostty) correctly renders these characters at full-width in normal shell output, but the Claude Code input area treats them as half-width, resulting in a mismatch between the rendered glyph and the allocated cell width.

Screenshot

<img width="122" height="60" alt="Image" src="https://github.com/user-attachments/assets/a98eb9bb-ab2b-4717-b7ff-1ca7a00c29ff" />

As shown above, the ⚪︎ character is squished into a half-width cell in the input area, with the cursor overlapping it.

Steps to Reproduce

1. Open Claude Code in a terminal (tested with Ghostty on macOS)
2. Type or paste a character like ⚪︎ (U+26AA) in the input area
3. The character appears squished/truncated — only occupying a half-width cell while the glyph itself is full-width

Expected Behavior

The character should occupy a full-width (2-cell) space in the input area, matching how the terminal renders it.

Actual Behavior

The character is allocated only 1 cell width, causing the glyph to be cut off or overlapping.

Note: This only affects the input area. Characters in Claude Code's output are displayed correctly.

Environment

• Claude Code v2.1.132
• Terminal: Ghostty (macOS)
• Font: MesloLGS Nerd Font Mono + Hiragino Kaku Gothic ProN (fallback)
• OS: macOS (Darwin 24.6.0)
• Locale: en_US.UTF-8