Auto-switch to an ASCII input source while prefix mode is active (macOS, CJK IME)

[sf-jin-ku]

idea / problem

I use a Korean IME most of the day, and prefix commands are painful because of it.

When I'm typing Korean in a pane and hit ctrl+b, the prefix key gets through fine, but the next key (c, v, h/j/k/l, …) often gets eaten by the IME and composed as a Korean character instead of being read as a command. So I either have to switch to English first, or the command just doesn't land. This happens with any non-Latin IME, not just Korean.

requested change

While prefix mode is active, Herdr briefly switches the system input source to an ASCII-capable layout, runs the command, then restores my IME to whatever it was when prefix mode ends. Pane text input stays exactly as it is now — only the prefix command layer changes.

I'd keep it small to start: macOS only, prefix mode only, best-effort (no-op if switching fails), restore on exit/cancel. On macOS this maps cleanly to the Text Input Source APIs — save the current source, select the current ASCII-capable layout, restore on exit — so it doesn't hard-code ABC/US, it uses whatever ASCII layout the user already has.

why you want this

For anyone on a non-Latin IME, prefix commands feel unreliable right now — the command layer should be as predictable as it is in English input mode, without touching how panes handle text.

It's also not a new idea. The modal-editor world has done this for years (command mode = ASCII, text mode = keep my IME):

• vim-barbaric — switches input method when you leave insert mode (https://github.com/rlue/vim-barbaric)
• vim-xkbswitch — switches layout on insert enter/leave, restores on the way back (https://github.com/lyokha/vim-xkbswitch)
• VSCodeVim's vim.autoSwitchInputMethod — drops the IME when you exit insert mode (https://github.com/VSCodeVim/Vim)
• im-select / macism — the CLI switchers those plugins lean on (https://github.com/daipeihust/im-select, https://github.com/laishulu/macism)

Happy to work on it if the direction sounds good.

[ogulcancelik]

thanks for the offer, converted this to an issue #400 please see my comment