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East Asian Ambiguous Width
Characters with East_Asian_Width=Ambiguous (e.g., Greek letters, mathematical symbols, box-drawing characters) have context-dependent width. In CJK contexts they're typically rendered as wide (2 cells), in Western contexts as narrow (1 cell). Terminal width calculation must match the terminal's rendering.
How this is testedautomated
Write an Ambiguous-width character (e.g., U+00A7 Section Sign), measure cursor displacement.
Write an Ambiguous-width character (e.g., U+00A7 Section Sign), measure cursor displacement.
The same probe runs against headless backends (via Termless) and real terminal apps (via a daemon launched in each terminal). This lets us distinguish parser correctness from rendering correctness.
Analysis2026-04-06
Supported by all 12 tested terminals — universal adoption. Part of the Unicode baseline.
Supported by 13 of 14 backends (93%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | width=1 (ambiguous chars vary by terminal/locale) |
| Ghostty | 1.3.1 | ✓ yes | width=1 (ambiguous chars vary by terminal/locale) |
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Cursor | ✓ yes | ||
| Terminal.app | ✓ yes |