TUI editor hides some double-byte characters in the input field

[nogataka]

• Symptom
  Certain double-byte characters entered in the input field are not visible.

  This issue occurs because macOS’s native Terminal handles CJK full-width characters and combining marks more consistently, while VS Code and Cursor (VS Code–based integrated terminals, powered by xterm.js) are more prone to misalignment depending on configuration.

  (CJK stands for Chinese, Japanese, and Korean — languages that use full-width characters which typically occupy two cells in a fixed-width terminal.)

• Steps to Reproduce

  1. Launch the TUI via the opencode command.
  2. Using a keyboard capable of double-byte input, enter four or more double-byte characters.
  3. Observe that some of the characters fail to render in the input field.

• Expected Result
  All double-byte characters entered in the field should be displayed.

Here are screenshots:

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Icons/Unicode characters cause file editing failures #2904: Icons/Unicode characters cause file editing failures
• [bug] opencode produces gabled text when input containing non-ascii characters #2593: [bug] opencode produces garbled text when input containing non-ascii characters
• Korean characters disappear in the input prompt when using WezTerm/Ghostty #2013: Korean characters disappear in the input prompt when using WezTerm/Ghostty
• Cyrillic characters are not displayed correctly in diff view #379: Cyrillic characters are not displayed correctly in diff view

Feel free to ignore if none of these address your specific case.