arf is a modern, cross-platform R console written in Rust. It provides a rich interactive experience with fuzzy help search, intelligent history navigation, and syntax highlighting—all with fast startup times.

[!WARNING] arf is under active development. The configuration file format and history file format are not yet stable and may change without notice in future versions.

Highlights

• Single Binary, Zero Dependencies — One small executable with no runtime dependencies. Just download and run.

• rig Integration — Seamless rig (R Installation Manager) support. Switch R versions with --with-r-version flag, or use the :switch meta command to change versions within a running session.

• Fuzzy History Search — fzf-style history search with Ctrl+R. Type fragments to find past commands quickly. Import your existing history from radian or R's .Rhistory.

• Syntax Highlighting — Tree-sitter based highlighting for R code with customizable colors.

• Interactive Help Browser — Fuzzy search through R documentation with :help or :h. Find any function across all installed packages instantly.

Features

• Cross-platform: Linux, macOS, and Windows
• Vi and Emacs editing modes
• Multiline editing with proper indentation
• Auto-matching brackets and quotes (with smart skip-over)
• Tab completion for R objects, functions, and file paths inside strings
• Customizable keyboard shortcuts (Alt+- → <-, Alt+P → |>)
• Command status indicator (shows error symbol when previous command failed)
• Reprex mode with optional auto-formatting via Air
• Shell mode (:shell to enter, :r to return)
• Configurable prompts and colors with placeholders ({version}, {cwd}, {status})
• Syntax highlighting with customizable colors
• SQLite-backed persistent history with import/export support
• IPC server for AI agent and CI integration
• Headless mode for non-interactive environments (CI, background jobs)

Installation

Pre-built binaries are available from GitHub Releases. You can install them using one of the following methods:

Shell Installer (Linux/macOS)

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/eitsupi/arf/releases/latest/download/arf-console-installer.sh | sh

winget (Windows)

winget install --id eitsupi.arf

cargo-binstall

cargo binstall --git https://github.com/eitsupi/arf arf-console

Manual Download

Download the archive for your platform from GitHub Releases and extract the binary to a directory in your PATH.

Build from Source

cargo install --git https://github.com/eitsupi/arf.git

Quick Start

# Launch arf
arf
Use a specific R version (requires rig)
arf --with-r-version 4.4
Enable reprex mode for reproducible examples
arf --reprex

Interactive Help

Press :h or :help to open the fuzzy help browser:

─ Help Search [12345 topics] ─────────────────────────
  Filter: mutate_
> dplyr::mutate           Create, modify, and delete columns
dplyr::mutate_all       Mutate multiple columns
dplyr::mutate_at        Mutate multiple columns
dplyr::mutate_if        Mutate multiple columns
─────────────────────────────────────────────────────
↑↓ navigate  Tab/Enter select  Esc exit

Meta Commands

Command	Description
:help, :h	Open interactive help browser
:info, :session	Show session information (version, config path, etc.)
:shell	Enter shell mode
:r	Return to R mode
:system <cmd>	Execute a single shell command inline
:reprex	Toggle reprex mode
:autoformat, :format	Toggle auto-formatting (requires Air)
:switch <version>	Restart with different R version (requires rig)
:restart	Restart R session
:cd [path]	Change working directory (no args → home)
:pushd <path>	Push current directory to stack and change to path
:popd	Pop directory from stack and change to it
:history browse	Browse and manage command history
:history clear	Clear command history (supports r, shell, all targets)
:history schema	Display history database schema and R examples
:commands, :cmds	Show available commands
:quit, :exit	Exit arf

Configuration

arf uses a TOML configuration file located at:

• Linux: ~/.config/arf/arf.toml
• macOS: ~/Library/Application Support/arf/arf.toml
• Windows: %APPDATA%\arf\arf.toml

Generate a default configuration with:

arf config init

Example Configuration

[startup]
r_source = "auto"       # "auto", "rig", or { path = "/path/to/R" }
show_banner = true
Initial mode settings (can be toggled at runtime)
[startup.mode]
reprex = false
autoformat = false      # Requires Air CLI
[editor]
mode = "emacs"          # "emacs" or "vi"
auto_match = true       # Auto-close brackets and quotes
auto_suggestions = "all" # "none", "all", or "cwd"
Keyboard shortcuts (crokey format)
[editor.key_map]
alt-hyphen = " <- "
alt-p = " |> "          # Use "ctrl-shift-m" for RStudio-style
[prompt]
format = "{status}R {version}> "
continuation = "+  "
shell_format = "[{shell}] $ "
mode_indicator = "prefix"   # "prefix", "suffix", or "none"
Command status indicator
[prompt.status]
symbol = { error = "✗ " }   # success = "" (empty) by default
override_prompt_color = false
R runtime configuration
[r]
auto_width = true       # Sync options(width) with terminal size
Reprex static configuration
[mode.reprex]
comment = "#> "
Syntax highlighting colors
[colors.r]
keyword = "LightBlue"
string = "Green"
comment = "DarkGray"
number = "LightMagenta"
operator = "Yellow"
[colors.prompt]
main = "LightGreen"

See the full Configuration Guide for all options.

Headless Mode & IPC

[!NOTE] This feature is experimental and may change in future versions.

Run R without a terminal and interact via IPC — useful for AI agents, CI, and editor extensions. Unlike MCP-based solutions that require R package installation and an MCP client, arf provides a single binary with a simple CLI for programmatic R access:

# Start headless R with IPC server
arf headless
From another terminal, evaluate R code
arf ipc eval '1 + 1'
Get session info as JSON
arf ipc session | jq '.r.version'
Shut down when done
arf ipc shutdown

See the full IPC & Headless Mode Guide for details.

Experimental Features

Features in this section are under development and may change or be removed in future versions. Configure them under the [experimental] section.

Spinner

Displays an animated spinner at the start of the line while R is evaluating code, providing visual feedback that the system is busy. Disabled by default.

To enable, set the frames option:

[experimental.prompt_spinner]
frames = "⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏"  # Braille dots
color = "Cyan"              # Spinner color (default: Cyan)

Configuration options:

Option	Default	Description
frames	"" (disabled)	Animation frames (each character is one frame).
color	"Cyan"	Spinner color. Accepts standard ANSI color names: Black, Red, Green, Yellow, Blue, Magenta, Cyan, White, and their Light variants (e.g., LightBlue).

Frame style examples:

# Braille dots (recommended)
frames = "⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏"
ASCII spinner (works in all terminals)
frames = "|/-\"
Block spinner
frames = "▖▘▝▗"

Auto-completion while typing

Show the completion menu automatically after typing a minimum number of characters, without requiring Tab.

[experimental]
completion_min_chars = 3  # Show completions after 3 characters

When not set, completion requires pressing Tab (the default behavior). This is similar to radian's complete_while_typing feature.

Fuzzy R completion

Use fuzzy matching for R code completions. When enabled, typing sf::geo can match sf::st_geometry and library(dpl can match dplyr. Disabled by default.

[experimental.r_completion]
fuzzy = true

Both :: (exported names) and ::: (internal names) are supported. Package exports are cached per-package with a 5-minute TTL for performance.

The package_functions option controls which function calls trigger package-name fuzzy completion (defaults to ["library", "require"]). Users can add custom functions like "box::use":

[experimental.r_completion]
fuzzy = true
package_functions = ["library", "require", "box::use"]

History forget

Automatically remove commands that produced errors from history. Similar to fish's sponge plugin.

[experimental.history_forget]
enabled = true
delay = 2          # Keep last N failed commands for quick retry
on_exit_only = false  # Purge on each prompt (false) or only on exit (true)

Configuration options:

Option	Default	Description
enabled	false	Enable automatic removal of failed commands.
delay	2	Number of recent failed commands to keep accessible for retry. Older failed commands are purged.
on_exit_only	false	If true, only purge when session ends. If false, purge on each prompt.

History export/import

[!CAUTION] These features are experimental and have not been thoroughly tested. The format and behavior may change in future versions.

Export

Export both R and shell history to a unified SQLite file for backup or transfer:

# Export to a unified file
arf history export --file ~/arf_backup.db
Export with custom table names
arf history export --file ~/arf_backup.db --r-table my_r --shell-table my_shell

Options:

Option	Description
--file	Path to output SQLite file (required)
--r-table	Table name for R history (default: r)
--shell-table	Table name for shell history (default: shell)

Import

Import command history from radian, R's native .Rhistory, or another arf database:

# Preview what would be imported (dry run)
arf history import --from radian --dry-run
Import from radian (default: ~/.radian_history)
arf history import --from radian
Import from R's native history
arf history import --from r --file .Rhistory
Import from a unified export file (restores both R and shell history)
arf history import --from arf --file ~/arf_backup.db
Import from a single-database file (r.db or shell.db)
arf history import --from arf --file /path/to/r.db
Import with custom hostname (to distinguish from native entries)
arf history import --from radian --hostname "radian-import"

Options:

Option	Description
--from	Source format: radian, r, or arf (required)
--file	Path to source file (required for arf, defaults to standard locations for others)
--hostname	Custom hostname to mark imported entries
--dry-run	Preview without importing
--import-duplicates	Import duplicate entries instead of skipping them
--unified	Force unified file mode (import both R and shell from table names)
--r-table	Table name for R history in unified file (default: r)
--shell-table	Table name for shell history in unified file (default: shell)

Supported sources:

Source	Description	Timestamps	Multiline	Mode routing
radian	~/.radian_history	Preserved	Preserved	By # mode:
r	.Rhistory or R_HISTFILE	-	-	→ r.db
arf	SQLite database (--file required)	Preserved	Preserved	By filename or --unified

Mode routing for arf format:

• Files named r.db or shell.db: Single-database import (by filename)
• Other filenames or --unified flag: Unified import (by table names, imports both R and shell)

Notes:

• By default, duplicate entries are skipped during import (matched by command text and timestamp). Use --import-duplicates to import all entries regardless.
• Self-import is detected and rejected when importing from an arf database to the same target file.
• Important: Exit arf before exporting to ensure the source databases are in a consistent state. The export itself uses atomic writes to prevent incomplete output files, but reading while arf is writing may capture inconsistent data.

Restore from backup:

# Restore history from a unified export file
arf history import --from arf --file ~/arf_backup.db

Known Issues

Error detection uses options(error = ...)

arf uses R's options(error = ...) to detect errors from packages like dplyr/rlang that output error messages to stdout instead of stderr. This is necessary for accurate error tracking in command history and the status indicator.

Limitations:

• If you set a custom error handler via options(error = ...), arf will chain to your handler, but arf's handler takes precedence. Your handler will still be called after arf records the error.
• There is a slight performance overhead (~microseconds) on each prompt due to R API calls for checking and resetting error state. This is negligible in practice but may be noticeable in benchmarks.

Related Projects

• radian — A 21st century R console written in Python. arf draws inspiration from radian's design philosophy.

• sircon — Simple R Console. A Windows-only R console with powerful autocomplete and a macro language for custom shortcuts. Some of sircon's advanced features are future goals for arf.

Acknowledgements

arf is built upon the broad Rust ecosystem and the remarkable efforts of those who have created open-source tools for R. In particular, we would like to highlight the following projects:

• ark — The arf-libr and arf-harp crates are derived from ark's libr and harp crates, which provide the foundation for embedding R in Rust applications. Windows initialization follows ark's pattern. tree-sitter-r powers syntax highlighting and code analysis.

• radian — arf's design and many features are inspired by radian, including shell mode, stderr formatting, and tab completion patterns. The feedback and discussions in radian's GitHub issues over the years have also been invaluable.

• felp — The interactive fuzzy help browser concept was inspired by felp's fuzzyhelp() function.

• reedline — The line editor library from the Nushell project that powers arf's interactive editing.

• mcp-repl — The headless mode's pager redirection and graphics device configuration are based on mcp-repl's approach for non-interactive R sessions.

• MCPRepl.jl / Kaimon.jl — The IPC server design (shared REPL with agent code visibility, synchronous evaluation via backend queue) was heavily informed by these Julia MCP server implementations.

License

MIT