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VTE termprop (OSC 666)
ESC ] 666 ; key=value BELOSC 666 is the VTE terminal property protocol, allowing applications to set typed key-value metadata on the terminal session. The sequence
ESC ] 666 ; key=value BEL sets a named property. Properties are typed (string, boolean, integer, color, UUID) and can be queried by the terminal emulator or desktop environment. Designed for integration between terminal applications and the GNOME desktop — properties can signal the shell type, current context, user identity, and session metadata. Defined by VTE (the GNOME terminal widget) and supported by GNOME Terminal, Prompt (GNOME's new terminal), and kgx.How this is testedpartial
Send
Send
OSC 666 ; test-prop=value BEL and verify the terminal consumes the sequence (cursor position unchanged).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 3 tested terminals — universal adoption. Part of the Rich TUI baseline.
Supported by 5 of 14 backends (36%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| Kitty | 0.46.2 | ✓ yes | |
| VS Code | 1.113.0 | ? unknown | |
| Warp | 0.2026.03.18.08.24.03 | ? unknown | |
| Cursor | 2.6.21 | ? unknown | |
| Terminal.app | 2.15 | ? unknown |