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Request Setting (DECRQSS)
ESC P $ q setting ESC \\DECRQSS (DCS $ q Pt ST) queries the current value of a terminal setting. For example, querying DECSCL returns the current conformance level. Useful for terminals that want to verify their configuration programmatically.
DECRQSS lets software ask the terminal for the current value of a setting instead of guessing. It is framed as a DCS string rather than a simple CSI reply, which makes parser support more demanding. Applications use it sparingly, but high-fidelity emulators need it for compatibility with tools that verify DEC private state.
How this is testedautomated
Send DCS $ q " p ST to query DECSCL, check for a DCS response.
Send DCS $ q " p ST to query DECSCL, check for a DCS response.
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.
Analysis2026-05-17
Supported by 8 of 14 backends (57%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | ✓ yes | ||
| Cursor | ✓ yes | ||
| Warp | ✗ no | ||
| Kitty | 0.46.2 | ✗ no | Headless mode has no output stream for DECRQSS responses |
| Terminal.app | ✗ no |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| vterm.js | 0.2.0 | ✓ yes | |
| xterm.js | 5.5.0 | ✓ yes | |
| Alacritty | 0.26.0 | ~ partial | Headless mode has no output stream for DECRQSS responses |
| WezTerm | 0.1.0-fork.5 | ~ partial | Headless mode has no output stream for DECRQSS responses |
| vt100.js | 0.2.1 | ✗ no | No output stream — pure TypeScript emulator |