Command Line

Lattice's command line is a rich editing surface — a real buffer with a major mode, not a single-line widget. It supports the full vim grammar, syntax highlighting, live error indication, and fuzzy history browsing. This is the rich minibuffer (docs/dev/architecture/rich-minibuffer.md).

The : line (tier 1)

Press : (Normal mode) to open the command line. It is a one-line readline buffer (*command-line* with command-line-mode major) edited through the universal Insert grammar:

All universal Insert-mode readline chords work: <C-a> (start of line), <C-e> (end of line), <C-b> (back one char), <C-f> (forward one char), <C-w> (delete word backward), <C-u> (delete to start of line), <Left> / <Right> cursor keys, <Del>.

The : line has live syntax highlighting (command word, range prefix, bang, :s/// pattern·replacement·flags), a live error indicator (unknown command, bad args), and parameter hints (from the resolved command's ArgSpec). :s/// shows a substitution preview on the target buffer as you type.

Expanding the command line (<C-x><C-e>, tier 2)

<C-x><C-e> grows the one-row : line in place into a full-width multi-row mini-buffer band at the bottom of the frame, pushing the panes and mode-lines up. The band enables the full vim grammar on the command text:

• When expanded, the *command-line* buffer switches its major mode to command-line-expand-mode (a dedicated tier-2 mode with isolated option overrides — line numbers, sign column, and wrap are all off, scoped to the band only, never leaking to the document pane). Collapsing reactivates command-line-mode.
• Normal / Insert / Visual modal editing
• Motions, operators, registers, undo, multi-line editing
• <CR> inserts a newline (multi-line commands)
• <C-x><C-e> again (or from Normal mode) collapses the band back to the one-row line without executing — review, then <CR> to run. <C-c> cancels (discards expanded edits).
• : is a no-op inside the band (already in the command line)

The expanded band height is controlled by command-line.expand-height (:set command-line.expand-height=full or =10 for 10 rows; default is half).

Command history

The : line keeps a history ring (command_history, in-memory, oldest-first, cap 100, dedup on consecutive identical). Two surfaces:

• Walk: <C-p>/<C-n> in the : line. The first <C-p> saves your in-progress text; <C-n> walks back down to it.
• Picker: q: (Normal chord) or :history or :history commands opens a fuzzy picker over command history, newest first. <CR> loads the chosen command into the : line without executing — tweak it (or expand), then <CR> to run. From inside the expanded band, q: seeds the filter with whatever you've typed so far.

The / ? search line

The search line works the same way: a buffer-backed readline surface (*search-line* with search-line-mode major).

Typing in the search line shows live match highlighting (incsearch): matches are painted on the document as you type. <CR> jumps to the first match; <Esc> cancels and returns you to where you started.

Search history

Search terms are stored in a separate search_history ring (same dedup and cap as command history). Browse via:

• Walk: <C-p>/<C-n> in the / / ? line.
• Picker: q/ q? (Normal chords) or :history searches opens a fuzzy picker over search history. <CR> loads into the / line (Forward direction) for editing.

Completions and live feedback

Options

• command-line.expand-height — half (default), full, or a fixed row count. Controls how tall the expanded band grows. :set command-line.expand-height=10

See also

• ex-commands — full ex-command reference.
• modal-editing — the keymap-side of the editor.
• options — :set + :customize deep dive.