Add Emacs/readline editing mode

[colonelpanic8]

Summary

• add a persisted client-local keyboard editing mode with Browser default and Emacs / readline options
• support common readline movement, deletion, kill/yank, transpose, and word-navigation bindings across text inputs and contenteditable editors
• make Control-N and Control-P navigate command palettes, comboboxes, selects, menus, and other candidate lists while the mode is active
• preserve terminal-native key handling

Why

Browser text controls do not consistently provide Emacs/readline editing shortcuts across platforms, and candidate-selection surfaces only respond to arrow keys. This mode provides a consistent opt-in editing experience throughout T3 Code.

Validation

• vp test run packages/contracts/src/settings.test.ts apps/web/src/emacsReadlineBindings.test.ts apps/web/src/AppRoot.test.tsx (39 tests)
• targeted contracts and web type checks
• targeted formatter and lint checks
• isolated live web verification of mode persistence, Control-A, Control-E, Control-W, Control-Y, and Control-N/Control-P command-palette navigation

Exact-head evidence

Revalidated at 4189d3c on current main (9a0a071): focused tests, vp check, and vp run typecheck passed. The capture uses only disposable local projects.

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Note

Medium Risk
Global capture-phase key handling can shadow browser or app shortcuts when emacs mode is on; composer Lexical mutations add regression surface for chips and prompt sync.

Overview
Adds an opt-in keyboard editing mode (default | emacs) on client settings, with a General settings control and restore-defaults support.

When Emacs / readline is enabled, a capture-phase EmacsReadlineBindings host applies readline chords to plain inputs, generic contenteditables, and the Lexical composer via ComposerEmacsReadlinePlugin, including kill/yank that keeps mention/skill chips and terminal context placeholders. Ctrl-N / Ctrl-P move focus in open candidate surfaces (composer command menu, comboboxes, etc.) instead of only arrow keys; terminals and keybinding-capture fields are excluded.

Keybindings gain optional source (default | user) through contracts, server persistence, and compilation. resolveCustomShortcutCommand lets readline consume chords that match built-in defaults while still yielding to custom or explicitly user shortcuts (with when context from terminal/preview/model picker state). Settings reset/save paths pass source so default vs custom rows stay accurate.

^{Reviewed by Cursor Bugbot for commit 4401e9d. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add Emacs/readline editing mode to the composer and global keybinding system

• Adds a new EmacsReadlineBindings component (mounted in AppRoot) that intercepts keydown events globally and applies Emacs/readline chords (Ctrl-A/E/B/F/K/U/W/Y, Alt-B/F/D, transpose-chars, etc.) to focused inputs, textareas, and contenteditables.
• Adds a ComposerEmacsReadlinePlugin inside the rich-text composer that maps readline actions onto Lexical nodes, preserving mention/skill chips and terminal context placeholders during kill/yank and movement.
• Adds a keyboardEditingMode setting ('default' | 'emacs') to ClientSettings and exposes a selector in the General settings panel so users can enable or reset the mode.
• Extends keybinding rules with an optional source field ('default' | 'user') across contracts, server persistence, and runtime compilation, enabling resolveCustomShortcutCommand to skip defaults when checking for application-shortcut precedence over readline chords.
• Behavioral Change: when emacs mode is enabled, many Ctrl/Alt key combinations are consumed by the readline handler before reaching the browser or application, which may shadow OS-level or application shortcuts not explicitly registered as custom bindings.

^{Macroscope summarized 4401e9d.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new user-facing feature (Emacs/readline editing mode) with ~2500 lines of new code across multiple new files, new keyboard event handling, and new settings. New capabilities of this scope warrant human review.

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

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^{Reviewed by Cursor Bugbot for commit 4401e9d. Configure here.}

[cursor]

Composer readiness uses stale root

Medium Severity

ComposerEmacsReadlinePlugin captures editor.getRootElement() once and writes data-emacs-readline-ready on that snapshot, without registerRootListener (used elsewhere in this file). If the root is null at effect time or later replaced, readiness never attaches. Capture then sees a managed host that is not ready and returns without handling, so composer-focused readline chords fall through to app shortcuts.

Additional Locations (1)

• apps/web/src/emacsReadlineBindings.ts#L739-L744

 

^{Reviewed by Cursor Bugbot for commit 4401e9d. Configure here.}

[cursor]

Model picker list not selected

Medium Severity

CANDIDATE_SURFACE_SELECTOR matches portaled combobox-popup and command-list, but the model picker’s inline list only exposes data-slot="combobox-list". Candidate detection then depends solely on a generic role="listbox" match. If that role is absent or hidden, Control-N/P are applied as line motion on the single-line search input, consumed, and never move the model highlight.

 

^{Reviewed by Cursor Bugbot for commit 4401e9d. Configure here.}