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Total line count

Category: scrollback · Baseline: core · Tags: Xterm Extensions · Specification ↗

Tests whether the terminal can report the total number of lines in the buffer (visible + scrollback). This is used by testing frameworks and terminal introspection tools to verify scrollback behavior.
How this is testedautomated
Write 30 lines, verify total line count is at least 30.

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✓ yesContent written to scrollback
Ghostty1.3.1✓ yesContent written to scrollback
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