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Desktop notifications (OSC 99)
ESC ] 99 ; params BELOSC 99 is Kitty's rich desktop notification protocol, extending simple notification sequences (OSC 9, OSC 777) with structured metadata. The sequence
ESC ] 99 ; params BEL supports key-value parameters including notification identifiers, action buttons, custom icons, urgency levels, and sound control. Identifiers allow updating or closing existing notifications. The protocol defines a capability query so applications can discover which notification features the terminal supports. Currently supported by Kitty, with partial adoption by other terminals.How this is testedpartial
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OSC 99 ; i=1:d=0:p=body;test BEL and verify the terminal consumes the notification 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 |