Pronounced "jee-macs".
A self-editable Emacs-like editor where JavaScript replaces Emacs Lisp and pluggable frontends render the UI: OpenTUI (terminal) and Electron (GUI).
This is a work-in-progress and doesn't have a major release yet. Lots of rough edges and have generally implemented the feature set that I need for work instead of all of Emacs's functionality.
We've implemented some default plugins in plugins/. You can find additional ones in https://github.com/stephenjayakar/jemacs-packages/.
The core installs independently of user config and packages:
./scripts/install.shBy default this links the current checkout at
${XDG_DATA_HOME:-~/.local/share}/jemacs and installs the launcher at
~/.local/bin/jemacs. The checkout may live anywhere; neither the core nor the
launcher assumes sibling config/package repositories.
User-owned files remain under ~/.jemacs:
~/.jemacs/init.ts startup config
~/.jemacs/packages/ out-of-tree packages
~/.jemacs/*.json persisted editor state
The config and packages repositories each provide their own scripts/install.sh.
Set JEMACS_HOME or BIN_DIR to override the core installation paths.
Terminal (default):
bun run dev
# or open a file
bun run src/main.ts README.mdGUI (Electron):
bun run build:gui # once, or before first GUI launch
bun run dev:gui
# same as: JEMACS_UI=electron bun run dev
# or: bun run src/main.ts --guiBoth hosts share the same kernel (src/kernel/), display model (src/display/), and bootstrap (src/run.ts).
The global launcher accepts jemacs --gui --nobuild to reuse the existing GUI
build without rebuilding or installing dependencies. If no GUI build exists,
it exits with instructions to build once. jemacs --nobuild launches the terminal
editor from source and skips dependency installation. Other arguments, such as
filenames, are passed through as usual.
Use Emacs TRAMP filenames with C-x C-f or as a command-line file. Jemacs
prompts for new host keys and passwords in the minibuffer and reuses SSH
connections:
/ssh:user@example.com:/home/user/file.txt
/ssh:user@example.com#2222:/home/user/file.txt
A persistent local Docker target is available for real SSH/filesystem testing. It listens only on localhost; its password is intentionally test-only.
scripts/tramp-ssh-target.sh start # prints the filename and credentials
scripts/tramp-ssh-target.sh test # real transport/editor integration test
scripts/tramp-ssh-target.sh reset # recreate its named filesystem volume
scripts/tramp-ssh-target.sh stopOptional: native OpenTUI editor surface for the selected window (no font-lock in that pane):
JEMACS_USE_TEXTAREA=1 bun run devCommands use GNU Emacs function names (find-file, kill-region, execute-extended-command, …). Full tables with implementation status: DEFAULT_KEYBINDINGS.md.
| Key | Emacs command |
|---|---|
| Type printable keys | self-insert-command |
| Return or Ctrl-J/Ctrl-M | newline / newline-and-indent |
| Backspace | delete-backward-char |
| Left/Right or Ctrl-B/Ctrl-F | backward-char / forward-char |
| Up/Down or Ctrl-P/Ctrl-N | previous-line / next-line |
| Ctrl-A / Ctrl-E | move-beginning-of-line / move-end-of-line |
| Meta-B / Meta-F | backward-word / forward-word |
| Ctrl-D | delete-char |
| Ctrl-K / Ctrl-Y | kill-line / yank |
| Ctrl-W / Meta-W | kill-region / kill-ring-save |
| Ctrl-X Ctrl-S | save-buffer |
| Ctrl-X Ctrl-E | eval-region |
| Ctrl-X B | switch-to-buffer |
| Ctrl-X Ctrl-B | list-buffers |
| Ctrl-X Ctrl-F | find-file |
| Ctrl-Space | set-mark-command |
| Ctrl-G | keyboard-quit |
| Meta-X / Alt-X / Esc X | execute-extended-command |
| Ctrl-H E | view-echo-area-messages |
| Ctrl-H C | describe-mode |
| Ctrl-H B | describe-bindings |
| Ctrl-H F | describe-function (RET → source) |
| Ctrl-H V | describe-variable |
| Ctrl-H K | describe-key |
| C-M-x | eval-defun |
| Meta-G G | goto-line |
| Ctrl-X 2 / Ctrl-X 3 | split-window-below / split-window-right |
| Ctrl-X K | kill-buffer |
| Ctrl-C Ctrl-R | revert-buffer |
| Ctrl-X Ctrl-C or Ctrl-C Ctrl-Q | save-buffers-kill-terminal |
Everything registered through the public extension API is live, source-tracked, and patchable:
| Kind | Define with | Describe | Patch at point | Revert |
|---|---|---|---|---|
| Command | editor.command(...) |
C-h f |
C-M-x (eval-defun) |
M-x jemacs-revert-function |
| Variable | defcustom / defvar |
C-h v |
C-M-x |
M-x jemacs-revert-definition |
| Key | editor.key / editor.defineKey |
C-h k |
C-M-x |
M-x jemacs-revert-definition |
| Mode | defineMode(...) |
C-h c |
C-M-x |
M-x jemacs-revert-definition |
| Hook | addHook(...) |
M-x jemacs-find-definition |
C-M-x |
M-x jemacs-revert-definition |
| Advice | addAdvice(...) |
M-x jemacs-find-definition |
C-M-x |
M-x jemacs-revert-definition |
Help buffers use help mode: put point on a Source: line (or the described name) and press RET (help-follow) to jump to the definition. M-x jemacs-find-definition covers any registered kind.
Temporary changes: C-M-x on a definition form (or C-x C-e on a region). Permanent: edit the file, C-x C-s, then M-x load-file. Loading clears all temporary patches first, then re-imports the module.
Eval and plugins receive the full runtime (src/runtime/jemacs-runtime.ts): defcustom, defineMode, addHook, addAdvice, Editor, and more. You can also patch Editor.prototype in a scratch buffer for kernel-level experiments (advanced; restart Jemacs to fully reset class state).
bun run dev:self # opens src/main.ts
bun run src/main.ts path/to/file.tsStartup config modules can be loaded with --config <path>. ~/.jemacs/init.ts is auto-loaded when present. Config modules should export install(editor) or installDefaultConfig(editor).
Module and config files: M-x load-file when the file exports install(editor) or installDefaultConfig(editor).
On macOS, some terminals send Option-key characters instead of Meta events, for example Option-X as ≈, Option-v as √, and Option-. as ≥. Jemacs maps the common Option encodings (including M-v from √); the Electron GUI uses the physical key (KeyboardEvent.code) for Option chords. Esc plus the key (e.g. Esc . for xref) works as a terminal-portable Meta fallback.
C-tab / C-S-tab run GNU other-window and previous-window-any-frame (cycle Emacs windows). Jemacs enables Kitty’s keyboard protocol when OpenTUI supports it.
Kitty binds Ctrl+Tab to its own tab bar by default, so the keys may never reach Jemacs. Add to ~/.config/kitty/kitty.conf:
map ctrl+tab
map ctrl+shift+tab
(Empty map lines remove Kitty’s binding.) Restart Kitty, then split a window in Jemacs (C-x 2) and try again. Fallback: C-x o (forward) — always works.
If a key still fails, check the echo area after pressing it: unbound keys show the resolved token and raw escape sequence.
The editor kernel deliberately avoids OpenTUI and Electron imports. Display output is built in src/display/build-display-model.ts as a host-agnostic DisplayModel; hosts only paint it:
| Host | Module |
|---|---|
| Terminal | src/ui/opentui-host.ts (OpenTuiHost) |
| GUI | src/ui/electron-host.ts (ElectronHost) |
OpenTUI key translation stays in src/ui/opentui-key.ts. Entry: src/main.ts (TUI or --gui) / src/main-electron.ts (GUI-only).
Core vs config: Interactive commands live in src/core/commands.ts (no key bindings). Default GNU keybindings are in src/config/default-bindings.ts using the same editor.key() / editor.defineKey() API as plugins and user config. Startup calls installDefaultConfig(editor) from src/config/index.ts. Override keys in a plugin or ~/.jemacs/init.ts by calling editor.key(...) after defaults load.
The evaluator uses Bun's dynamic Function constructor rather than a hard security sandbox. Treat evaluated code and plugins as trusted user config, like Emacs Lisp. Do not run hostile plugins.