Terminal Standards, Escape Sequences, and Capability Negotiation

Use this skill when code emits or parses terminal control sequences, depends on terminal features, or must behave across emulators, multiplexers, and Windows console hosts.

Standards hierarchy

Think in layers:

1. Baseline: printable text, carriage return, newline, backspace, tab.
2. ECMA-48 / ANSI / ISO 6429: CSI controls and SGR attributes.
3. DEC VT lineage: cursor movement, alternate keypad modes, device status patterns, private modes.
4. xterm conventions: alternate screen, mouse modes, focus events, bracketed paste, OSC extensions.
5. Modern emulator extensions: Kitty keyboard/graphics, iTerm2 images, sixel, OSC 8 hyperlinks, OSC 52 clipboard, theme queries.
6. Platform host behavior: Windows virtual terminal processing, ConPTY, tmux/screen filtering, SSH latency.

The further down this stack you go, the more you need detection, fallbacks, and cleanup.

Safer defaults