emacs-keys-mode (the `<C-x>` leader)

The emacs-keys tribute: a default-on, configurable <C-x> leader binding emacs-style buffer / file / window chords on top of vim modal editing.

Lattice is a vim-modal editor (see modal-editing). But emacs's C-x prefix map — C-x C-f to find a file, C-x b to switch buffer, C-x 2 to split a window — is muscle memory for a lot of people, and the two vocabularies don't actually collide: vim owns the alphabetic Normal-mode keys, emacs's window/buffer verbs live behind a Ctrl-prefix leader. So Lattice ships both.

emacs-keys-mode is a small tribute minor mode. It contributes one thing: a configurable <C-x> leader (prefix key) whose chord map mirrors the most-used entries of emacs's C-x keymap. It does not replace vim modal editing, remap your alphabetic motions, or touch Insert mode. It layers a handful of Ctrl-prefixed window/buffer chords on top.

This is an optional convenience, not a paramount feature. If you don't want it, one :set noemacs-keys reclaims <C-x> for plain Normal-mode input. The vim grammar is the canonical command API; this is a second entry point to commands you already have.

Enabling it

It's on by default (emacs-keys = true). Two typed options control it, both live (:set re-pushes the leader map immediately — no restart):

:set noemacs-keys              " turn the tribute off (reclaim <C-x>)
:set emacs-keys                " turn it back on
:set emacs-keys-prefix=<C-z>   " move the whole leader to <C-z>

Disabling doesn't churn the mode set — the mode stays registered and active; the layer carries the gate, so toggling it off just rebuilds the leader map empty and <C-x> falls through to ordinary Normal-mode resolution. Re-targeting the prefix rebuilds the whole map under the new chord live; the old prefix stops responding. A malformed prefix degrades to an empty tribute (logged, never a panic) rather than breaking boot.

The emacs-keys option and the emacs-keys-mode mode are distinct names (the -mode suffix is the mode-id convention — see modes). You toggle the feature with :set emacs-keys, not :emacs-keys-mode.

It's live everywhere — not just code buffers

emacs-keys-mode is a Universal-activation mode: the leader is live in every buffer you can focus, including synthetic buffers like *messages*, help, and the file tree — exactly like emacs, whose C-x map works in *Messages* too. (Most minor modes are document-only; this one is deliberately universal because a window/buffer leader that died in synthetic buffers would be a worse tribute.)

The <C-x> leader and its chord map

Press the leader (<C-x> by default), then a suffix key. The bare leader is a partial chord — Lattice waits for the suffix (or <Esc> to abort), the same partial-chord state any multi-key vim chord uses.

The map has two tiers. Tier 1 is buffer / file / save / quit; Tier 2 is window (pane) management. Every chord is a second entry point to an ex-command or action you already have — the leader introduces no new commands of its own.

Tier 1 — file / buffer / save / quit

<C-x>b (switch) and <C-x><C-b> (list) are distinct chords, mirroring emacs's switch-to-buffer vs list-buffers.

<C-x><C-c> is emacs's save-buffers-kill-emacs. It routes to the dirty-guarded :qa (quit every pane and tab), not the brute <C-c> quit — unsaved changes are honoured exactly as :qa honours them. Plain <C-c> (no leader) keeps its usual meaning.

Tier 2 — window (pane) management

These mirror emacs's C-x 2 / C-x 3 / C-x 0 / C-x 1 / C-x o and reuse the same pane actions the vim <C-w> family binds — the leader is just a second doorway to them.

Digit suffixes don't become counts. <C-x>2 and <C-x>3 are matched as literal second chords after the leader, so the digit never enters vim count accumulation. A bare digit (no leader pending) still starts a count as usual — 2j is two-lines-down, untouched.

<C-g> is not part of this mode

<C-g> (emacs's keyboard-quit) cancels a running operation and returns you to Normal — see modal-editing. It is a builtin binding, not part of the tribute, so :set noemacs-keys does not take it away.

It is called out here because it is the one emacs chord you get regardless of this setting, and because it is not under the <C-x> leader.

The window/buffer ex-commands

The pane operations the Tier-2 chords reach also exist as plain ex-commands, with vim-conventional names — useful from the : line, in macros, and in config:

:qa is the editor-wide quit: it ignores pane and tab count and shuts everything down (subject to the dirty guard). Contrast plain :q, which closes a single pane — or the current tab page if it's the tab's last pane — and only quits when it's the last pane of the last tab.

How it coexists with vim modal editing

The tribute is additive. It does not change the vim grammar:

• The leader layer is Normal-mode only. It binds chords in Normal mode and nowhere else. Insert mode is untouched — <C-x> there keeps whatever Insert-mode meaning it has (e.g. completion triggers), and so does every other key. Visual / Operator-Pending / Replace / the : and / lines are all unaffected.
• No alphabetic motion is remapped. h j k l, w b e, operators, text objects, counts — all exactly as modal-editing describes. The tribute lives behind a Ctrl-prefix leader, off in its own corner of the keymap.
• It's one minor mode among many. It shows up in :list-modes, carries metadata in :describe-mode emacs-keys-mode, and its chords appear in :describe-key / :keymap with their source — the same introspection every mode gets. :describe-key <C-x>b tells you exactly what the chord does under your active modes.

If a chord ever feels like it's shadowing something, that's what the introspection is for: :describe-key replays the live precedence fold and names the binding that actually fires. And the escape hatch is always one option away — :set noemacs-keys.

See also

• modal-editing — the vim grammar this layers on top of (Normal / Insert / Visual, operators, motions).
• modes — major + minor modes, :<mode-name> toggles, the option-resolution model, and the keymap-precedence rules the leader plays by.
• options — :set + :customize, the typed options emacs-keys and emacs-keys-prefix live in.
• docs/dev/architecture/emacs-keys.md — the design fragment (the what and why); docs/dev/operations/slice-plans/archive/emacs-keys.md is the implementation record.