led

A lightweight, fast text editor for the terminal, written in Rust.

Warning

Vibe coded. This project is an experiment in getting an AI assistant to follow Functional Reactive Programming (FRP) principles and produce reasonable code within that discipline. I've focused on the overall architecture rather than reviewing the code output in detail. For projects I've mostly written by hand, see ureq and str0m.

led is built on a functional reactive programming (FRP) architecture where the model is a pure reducer, all side effects live in drivers, and the UI is a derived function of state. The result is a responsive editor with rich features and a small footprint.

Features

Language Server Protocol

Full LSP integration with out-of-the-box support for:

Language	Server
Rust	rust-analyzer
TypeScript/JavaScript	typescript-language-server
Python	pyright
C/C++	clangd
Swift	sourcekit-lsp
TOML	taplo
JSON	vscode-json-language-server
Bash	bash-language-server

Language servers are not bundled — install them separately and make sure they are on your PATH. led will automatically start the right server when you open a file.

# Rust
rustup component add rust-analyzer

# TypeScript / JavaScript
npm install -g typescript-language-server typescript

# Python
npm install -g pyright

# C / C++
brew install llvm            # macOS
apt install clangd           # Debian/Ubuntu

# Swift (included with Xcode)
# sourcekit-lsp is available after installing Xcode or the Swift toolchain

# TOML
cargo install taplo-cli --locked

# JSON
npm install -g vscode-langservers-extracted

# Bash
npm install -g bash-language-server

• Completions — fuzzy-filtered popup with auto-imports
• Go to definition
• Rename — workspace-wide symbol rename
• Code actions — quick fixes and refactors
• Diagnostics — inline errors and warnings with gutter indicators
• Inlay hints — toggleable type annotations
• Format — on-demand formatting with import sorting
• Progress — spinner in status bar during long operations

Syntax Highlighting

Tree-sitter powered highlighting for Bash, C, C++, JavaScript, JSON, Make, Markdown, Python, Ruby, Rust, Swift, TOML, and TypeScript. Rainbow bracket coloring with matching bracket highlighting.

Language Detection

led detects a file's language using three methods, in priority order:

1. File extension — .rs → Rust, .py → Python, .rb → Ruby, etc.
2. Filename — Makefile, Gemfile, Rakefile, Vagrantfile
3. Editor modeline — if the extension and filename don't match a known language, led scans the first 5 lines for Emacs or Vim modelines:

# -*- mode: ruby -*-
# vim: set ft=ruby :

This is useful for scripts and config files that lack a recognized extension.

The following mode strings are recognized in modelines:

Mode string	Language
rust	Rust
python	Python
javascript, js	JavaScript
typescript, ts	TypeScript
tsx	TSX
json	JSON
toml	TOML
markdown, md	Markdown
bash, sh	Bash
c	C
cpp, c++	C++
swift	Swift
make	Make
ruby	Ruby

Search

• Project search (Ctrl+f) — ripgrep-powered search across the workspace with case and regex toggles. Results grouped by file with a live preview pane.
• Buffer search (Ctrl+s) — incremental search within the current file with match highlighting and wrap-around navigation.
• Find file (Ctrl+x Ctrl+f) — fuzzy path completion for quick file opening.

File Browser

Side panel file tree with expand/collapse, file preview on selection, and background open. Toggle with Ctrl+b.

Git Integration

Current branch in the status bar. Per-file status (modified, staged, untracked) shown in the file browser. Line-level change indicators in the editor gutter.

Session Persistence

led automatically saves and restores your session — open files, cursor positions, scroll positions, tab order, and undo history are preserved across restarts via a per-workspace SQLite database.

Multiple editor instances on the same workspace are supported. The primary instance holds a lock; secondary instances sync edits through the workspace database.

Editing

• Undo/redo with Emacs-style linear history
• Mark and region (set mark, kill region, yank)
• Kill ring with text accumulation across consecutive deletes
• Smart indentation on newline
• Jump list — navigate back and forth through your position history
• Symbol outline via LSP document symbols
• Bracket matching and jump-to-matching-bracket
• Auto-close buffers to prevent resource exhaustion

Install

cargo install --path led

Or build from source:

git clone https://github.com/user/led.git
cd led
cargo build --release

The binary will be at target/release/led.

Usage

led [path]

Open a file or directory. With no argument, led opens the current directory.

Flag	Description
--log-file PATH	Write debug logs to a file
--reset-config	Reset keybindings and theme to defaults, clear session DB

Configuration

Configuration lives in ~/.config/led/.

File	Purpose
keys.toml	Key bindings
theme.toml	Color theme
db.sqlite	Session database

Run led --reset-config to restore default keybindings and theme.

Custom Key Bindings

Key bindings are defined in TOML. Modifiers are ctrl, alt, and shift. Chord sequences use sub-tables.

[keys]
"ctrl+s" = "in_buffer_search"
"alt+enter" = "lsp_goto_definition"

# Chord: Ctrl+x followed by Ctrl+s
[keys."ctrl+x"]
"ctrl+s" = "save"

Context-specific bindings for the file browser and search panel use [browser] and [file_search] sections.

Default Key Bindings

Editing

Key	Action
Enter	Insert newline
Backspace	Delete backward
Delete / Ctrl+d	Delete forward
Tab	Insert tab / accept completion
Ctrl+k	Kill line
Ctrl+/ / Ctrl+_ / Ctrl+7	Undo
Ctrl+Space	Set mark
Ctrl+w	Kill region
Ctrl+y	Yank (paste)
Ctrl+x (	Start recording macro
Ctrl+x )	Stop recording macro
Ctrl+x e	Play macro (e repeats)
Ctrl+x N e	Play macro N times (0=until error)

Navigation

Key	Action
Up / Down	Move up / down
Left / Right	Move left / right
Home / Ctrl+a	Line start
End / Ctrl+e	Line end
Page Up / Alt+v	Page up
Page Down / Ctrl+v	Page down
Ctrl+Home / Alt+<	File start
Ctrl+End / Alt+>	File end
Alt+]	Jump to matching bracket

Tabs & Buffers

Key	Action
Ctrl+Left	Previous tab
Ctrl+Right	Next tab
Ctrl+x k	Kill buffer

Files

Key	Action
Ctrl+x Ctrl+s	Save
Ctrl+x Ctrl+a	Save all
Ctrl+x Ctrl+d	Save (no format)
Ctrl+x Ctrl+w	Save as
Ctrl+x Ctrl+f	Find file

Search

Key	Action
Ctrl+f	Project search
Ctrl+s	Buffer search
Alt+1 (in search)	Toggle case sensitivity
Alt+2 (in search)	Toggle regex
Alt+3 (in search)	Toggle replace mode
Alt+Enter (in search)	Replace all

In replace mode, the search input, replace input, and results form a single vertical list navigated with Up/Down. Tab switches between the search and replace inputs. On a result row, Right replaces the selected match, Left undoes the last replace. Enter closes the panel. Alt+Enter replaces all remaining matches and closes.

LSP

Key	Action
Alt+Enter	Go to definition
Ctrl+r	Rename symbol
Alt+i	Code action
Ctrl+t	Toggle inlay hints
Ctrl+x i	Sort imports

Issues

Key	Action
Alt+.	Next issue
Alt+,	Previous issue

"Issue" navigation cycles through LSP errors and warnings, unstaged and staged git changes, and PR diff lines and review comments — in that priority order.

Git & GitHub

Key	Action
Ctrl+x Ctrl+p	Open PR / comment URL

Ctrl+x Ctrl+p opens the current pull request in the browser. If the cursor is on a line with a PR review comment, that comment's URL is opened instead.

Jump List

Key	Action
Alt+b / Alt+Left	Jump back
Alt+f / Alt+Right	Jump forward
Alt+o	Outline

UI

Key	Action
Ctrl+b	Toggle side panel
Alt+Tab	Toggle focus (editor / side panel)
Ctrl+h e	Open messages
Esc / Ctrl+g	Abort / cancel
Ctrl+z	Suspend
Ctrl+x Ctrl+c	Quit

File Browser (when focused)

Key	Action
Left	Collapse directory
Right	Expand directory
Enter	Open selected
Alt+Enter	Open in background
Ctrl+q	Collapse all

Architecture

led follows a strict FRP cycle:

State → Derived → Drivers → Model → State

• State — a single immutable AppState containing all editor state
• Derived — pure transforms from state into driver commands (no business logic)
• Drivers — handle side effects: terminal I/O, file system, LSP, git, syntax parsing, clipboard, timers, session persistence
• Model — a pure reducer (State, Mutation) → State composed from combinator chains

The codebase is organized as a Cargo workspace with 15 crates — each driver (LSP, git, syntax, file search, clipboard, etc.) is its own crate with a clean boundary.

License

MIT