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

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.

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.