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Color palette (OSC 4)
ESC ] 4 ; c ; spec BELOSC 4 changes or queries individual entries in the 256-color palette (indices 0-255). To set a color:
ESC ] 4 ; c ; spec BEL where c is the palette index and spec is an X11 color specification (e.g. rgb:FF/00/00). To query: ESC ] 4 ; c ; ? BEL — the terminal responds with the current color in rgb:RR/GG/BB format. Applications use this to customize the terminal palette at runtime, e.g. for theme switching or to ensure specific colors match a design system.How this is tested: Query palette color 0 with
OSC 4 ; 0 ; ? BEL, verify response matches OSC 4 ; 0 ; rgb:... pattern.Analysis2026-04-06
Supported by 3 of 14 backends (21%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| Kitty | 0.46.2 | ✓ yes | OSC 4 color query requires a real display — headless backends have no color palette to query |
| 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 |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| Alacritty | 0.26.0 | ✗ no | OSC 4 color query requires a real display — headless backends have no color palette to query |
| vt100.js | 0.2.1 | ✗ no | Not implemented — pure TypeScript emulator |
| vterm | 0.2.0 | ✗ no | OSC 4 color query not implemented in vterm.js |
| WezTerm | 0.1.0-fork.5 | ✗ no | OSC 4 color query requires a real display — headless backends have no color palette to query |
| xterm.js | 5.5.0 | ✗ no | OSC 4 color query requires a real display — headless backends have no color palette to query |