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ED at scroll region boundary

Category: erase · Baseline: core · Tags: ECMA-48 Standard, VT100 · Specification ↗

ED (Erase in Display) behavior when a scroll region (DECSTBM) is active varies by terminal. Some terminals erase only within the scroll region, while others erase the full screen regardless. The key edge case is that content outside the scroll region should generally be preserved by ED operations performed inside the region. This matters for applications that use scroll regions with fixed header/footer areas.
How this is testedautomated
Write "KEEP_THIS" on row 0, set scroll region 3;10, move cursor inside region, send \x1b[J (ED 0), verify row 0 still contains "KEEP_THIS".

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

TerminalVersionSupportNotes
iTerm23.6.9✓ yes
Ghostty1.3.1✓ yes
VS Code✓ yes
Warp✓ yes
Cursor✓ yes
Terminal.app✓ yes

Headless Backends

Parser correctness only — a means the parser accepts the sequence.

BackendVersionSupportNotes
Alacritty0.26.0✓ yes
Kitty0.40.0✓ yes
vt100.js0.2.1✓ yes
vterm0.2.0✓ yes
WezTerm0.1.0-fork.5✓ yes
xterm.js5.5.0✓ yes