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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.
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.
Analysis2026-04-06
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 | ||
| Terminal.app | ✗ no |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| vterm | 0.2.0 | ✓ yes | |
| xterm.js | 5.5.0 | ✓ yes | |
| Alacritty | 0.26.0 | ~ partial | Headless mode has no output stream for DECRQSS responses |
| Kitty | 0.40.0 | ~ 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 |