Appearance
OSC 633;A prompt start
ESC ] 633 ; A BELOSC 633;A is VS Code's prompt start marker, mirroring OSC 133;A. It marks the beginning of a shell prompt so VS Code's integrated terminal (and other OSC 633-aware terminals) can identify where prompts start in scrollback.
VS Code defined OSC 633 as a parallel namespace to OSC 133 so it could add VS Code-specific extensions without conflicting with the FinalTerm spec. Shells configured with VS Code's shell integration scripts emit both 133 and 633 markers, so the terminal works with whichever protocol is supported.
How this is testedpartial
Send
Send
OSC 633 ; A BEL and verify the terminal consumes the sequence (cursor doesn't advance, terminal remains responsive).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 9 tested terminals — universal adoption. Part of the Rich TUI baseline.
Supported by 11 of 14 backends (79%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| Terminal.app | 2.15 | ✓ 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 |