Features›Extensions›Sixel geometry report (CSI ? Pi;Pa;Pv S)

Sixel geometry report (CSI ? Pi;Pa;Pv S)

Category: extensions · Baseline: rich · Tags: Sixel Graphics, Xterm Extensions · Specification ↗

CSI ? Pi ; Pa ; Pv S

Queries xterm for sixel graphics geometry. Added in xterm patch 402 (2025-06-22). The Pi parameter specifies the item being queried (color registers, geometry, etc.), Pa is the action (read/reset/set), and Pv is the value. The response reports current sixel capability values so applications can size sixel images to match the terminal's maximum supported dimensions. Support: xterm only as of 2026. Mentioned in xterm ChangeLog patch 402.

How this is testedautomated
Send CSI ? 1 ; 1 ; 0 S (read color register count), verify response matches CSI ? 1 ; ... S.

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.

Analysis2026-05-17

Supported by 3 of 12 terminals (25%). Part of the Rich TUI baseline. Notes: Kitty: Sixel geometry report not supported; Alacritty: Sixel geometry report not supported; WezTerm: Sixel geometry report not supported.

Supported by 4 of 14 backends (29%)

Terminal Applications

Terminal	Version	Support	Notes
iTerm2	3.6.9	✗ no	Sequence consumed but no sixel geometry response
Ghostty	1.3.1	✗ no	Sequence consumed but no sixel geometry response
VS Code		✗ no
Warp		✗ no
Kitty	0.46.2	✗ no	Sixel geometry report not supported
Cursor		✗ no
Terminal.app		✗ no

Headless Backends

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

Backend	Version	Support	Notes
vt100.js	0.2.1	✓ yes
vterm.js	0.2.0	✓ yes
xterm.js	5.5.0	✓ yes
Alacritty	0.26.0	✗ no	Sixel geometry report not supported
WezTerm	0.1.0-fork.5	✗ no	Sixel geometry report not supported

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