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CUU stops at top
CUU (Cursor Up, CSI Pn A) should stop at the top margin of the scroll region, or row 1 if no scroll region is set. Moving up with a count exceeding the current row should clamp to row 0 rather than wrapping to the bottom. This prevents cursor escape from the visible area and is relied upon by screen-clearing routines that use large CUU counts.
How this is testedautomated
Position at row 3, send
Position at row 3, send
\x1b[999A (CUU with count 999), verify cursor stopped at row 0.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 Core TUI baseline.
Supported by 14 of 14 backends (100%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Cursor | ✓ yes | ||
| Terminal.app | ✓ yes |