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modifyOtherKeys mode 3
xterm's modifyOtherKeys mode 3 (patch 398, April 2025) makes ALL keyboard input — including unmodified keys — send escape sequences. Mode 2 only affects modified keys (Ctrl+X, Alt+X), while mode 3 extends this to every keypress. The sequence is
CSI > 4 ; 3 m.
Mode 3 also extends modifier encoding to cursor-keys, function-keys, keypad-keys, modifier-keys, and special-keys, with subparameters in XTMODKEYS for selective modifier masking. This provides applications with unambiguous key identification similar to the kitty keyboard protocol, but using xterm's native encoding.How this is tested: Send
CSI > 4 ; 3 m to enable modifyOtherKeys mode 3, verify terminal is responsive, then disable with CSI > 4 ; 0 m.Analysis2026-03-26
Supported by 2 of 18 backends (11%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| cmux | ✓ yes | ||
| iTerm2 | 3.6.9 | ? unknown | |
| Ghostty | 1.3.1 | ? unknown | |
| VS Code | 1.112.0 | ? unknown | |
| Cursor | 2.6.21 | ? unknown | |
| Warp | 0.2026.03.18.08.24.03 | ? unknown | |
| Terminal.app | 2.15 | ? unknown | |
| Kitty | 0.46.2 | ? unknown | modifyOtherKeys mode 3 not exposed via Python batch bridge |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| vterm | 0.2.0 | ✓ yes | |
| Alacritty | 0.26.0 | ~ partial | modifyOtherKeys mode 3 not exposed in headless mode |
| WezTerm | 0.1.0-fork.5 | ~ partial | modifyOtherKeys mode 3 not exposed in headless mode |
| vt100.js | 0.2.1 | ✗ no | Not implemented — pure TypeScript emulator |
| xterm.js | 5.5.0 | ? unknown | modifyOtherKeys mode 3 not implemented in xterm.js |
| xterm.js | 6.0.0 | ? unknown | modifyOtherKeys mode 3 not implemented in xterm.js |
| xterm.js | 5.4.0 | ? unknown | modifyOtherKeys mode 3 not implemented in xterm.js |
| xterm.js | 6.1.0-beta.195 | ? unknown | modifyOtherKeys mode 3 not implemented in xterm.js |