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CUP with DECOM
When DECOM (Origin Mode, CSI ? 6 h) is set, CUP coordinates become relative to the current scroll region set by DECSTBM. With a scroll region of rows 5-15 and DECOM enabled,
CSI 1 ; 1 H moves the cursor to row 5 (the top of the scroll region) rather than the absolute top of the screen. This interaction between DECSTBM and DECOM is fundamental to how full-screen applications partition the terminal into independently scrolling regions.How this is testedautomated
Set DECSTBM 5;15, enable DECOM, send
Set DECSTBM 5;15, enable DECOM, send
\x1b[1;1H, verify cursor is at row 4 (0-based scroll region top). Disable DECOM and reset scroll region.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 9 of 14 backends (64%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Cursor | ✓ yes | ||
| iTerm2 | 3.6.9 | ✗ no | got 1;1, expected 5;1 |
| Ghostty | 1.3.1 | ✗ no | got 1;1, expected 5;1 |
| Terminal.app | ✗ no |