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Insert/replace mode (IRM)
IRM (Insert/Replace Mode) controls whether new characters insert (shifting existing content right) or replace (overwriting) at the cursor. Enable insert mode with
ESC [ 4 h, disable (replace mode) with ESC [ 4 l. Replace mode is the default. Most modern TUI applications use explicit ICH/DCH sequences rather than IRM.Supported by 4 of 6 backends (67%)
Support Matrix
| Backend | Version | Support | Notes |
|---|---|---|---|
| Alacritty | 0.26.0 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| WezTerm | 0.1.0-fork.5 | ✓ yes | |
| xterm.js | 5.5.0 | ✓ yes | |
| Kitty | 0.40.0 | ~ partial | Not exposed via Python batch bridge |
| vt100 | 0.1.0 | ✗ no | IRM not implemented — pure TypeScript emulator |