CLI Reference#

The Jac CLI provides commands for running, building, testing, and deploying Jac applications.

💡 Enhanced Output: For beautiful, colorful terminal output with Rich formatting, install the optional jac-super plugin: pip install jac-super. All CLI commands will automatically use enhanced output with themes, panels, and spinners.

Quick Reference#

Command	Description
`jac run`	Execute a Jac file
`jac start`	Start REST API server (use `--scale` for K8s deployment)
`jac create`	Create new project
`jac check`	Type check code
`jac test`	Run tests
`jac format`	Format code
`jac clean`	Clean project build artifacts
`jac purge`	Purge global bytecode cache (works even if corrupted)
`jac enter`	Run specific entrypoint
`jac dot`	Generate graph visualization
`jac debug`	Interactive debugger
`jac plugins`	Manage plugins
`jac config`	Manage project configuration
`jac destroy`	Remove Kubernetes deployment (jac-scale)
`jac add`	Add packages to project
`jac install`	Install project dependencies
`jac remove`	Remove packages from project
`jac update`	Update dependencies to latest compatible versions
`jac jacpack`	Manage project templates (.jacpack files)
`jac grammar`	Extract and print the Jac grammar
`jac script`	Run project scripts
`jac py2jac`	Convert Python to Jac
`jac jac2py`	Convert Jac to Python
`jac tool`	Language tools (IR, AST)
`jac lsp`	Language server
`jac js`	JavaScript output
`jac build`	Build for target platform (jac-client)
`jac setup`	Setup build target (jac-client)

Core Commands#

jac run#

Execute a Jac file.

Note: jac <file> is shorthand for jac run <file> - both work identically.

jac run [-h] [-m] [--no-main] [-c] [--no-cache] [--profile PROFILE] filename [args ...]

Option	Description	Default
`filename`	Jac file to run	Required
`-m, --main`	Treat module as `__main__`	`True`
`-c, --cache`	Enable compilation cache	`True`
`--profile`	Configuration profile to load (e.g. prod, staging)	`""`
`args`	Arguments passed to the script (available via `sys.argv[1:]`)

Like Python, everything after the filename is passed to the script. Jac flags must come before the filename.

Examples:

# Run a file
jac run main.jac

# Run without cache (flags before filename)
jac run --no-cache main.jac

# Pass arguments to the script
jac run script.jac arg1 arg2

# Pass flag-like arguments to the script
jac run script.jac --verbose --output result.txt

Passing arguments to scripts:

Arguments after the filename are available in the script via sys.argv:

# greet.jac
import sys;

with entry {
    name = sys.argv[1] if len(sys.argv) > 1 else "World";
    print(f"Hello, {name}!");
}

jac run greet.jac Alice        # Hello, Alice!
jac run greet.jac              # Hello, World!

sys.argv[0] is the script filename (like Python). For scripts that accept flags, use Python's argparse module:

import argparse;

with entry {
    parser = argparse.ArgumentParser();
    parser.add_argument("--name", default="World");
    args = parser.parse_args();
    print(f"Hello, {args.name}!");
}

jac run greet.jac --name Alice

jac start#

Start a Jac application as an HTTP API server. With the jac-scale plugin installed, use --scale to deploy to Kubernetes. Use --dev for Hot Module Replacement (HMR) during development.

jac start [-h] [-p PORT] [-m] [--no-main] [-f] [--no-faux] [-d] [--no-dev] [-a API_PORT] [-n] [--no-no_client] [--scale] [--no-scale] [-b] [--no-build] [filename]

Option	Description	Default
`filename`	Jac file to serve	`main.jac`
`-p, --port`	Port number	`8000`
`-m, --main`	Treat as `__main__`	`True`
`-f, --faux`	Print docs only (no server)	`False`
`-d, --dev`	Enable HMR (Hot Module Replacement) mode	`False`
`--api_port`	Separate API port for HMR mode (0=same as port)	`0`
`--no_client`	Skip client bundling/serving (API only)	`False`
`--scale`	Deploy to Kubernetes (requires jac-scale)	`False`
`-b, --build`	Build Docker image before deploy (with `--scale`)	`False`

Examples:

# Start with default main.jac on default port
jac start

# Start on custom port
jac start -p 3000

# Start with Hot Module Replacement (development)
jac start --dev

# HMR mode without client bundling (API only)
jac start --dev --no-client

# Deploy to Kubernetes (requires jac-scale plugin)
jac start --scale

# Build and deploy to Kubernetes
jac start --scale --build

Note:

If your project uses a different entry file (e.g., app.jac, server.jac), you can specify it explicitly: jac start app.jac

jac create#

Initialize a new Jac project with configuration. Creates a project folder with the given name containing the project files.

jac create [-h] [-f] [-u USE] [-l] [name]

Option	Description	Default
`name`	Project name (creates folder with this name)	Current directory name
`-f, --force`	Overwrite existing project	`False`
`-u, --use`	Jacpac template: registered name, file path, or URL	`default`
`-l, --list-jacpacks`	List available jacpack templates	`False`

Examples:

# Create basic project (creates myapp/ folder)
jac create myapp
cd myapp

# Create full-stack project with client template (requires jac-client)
jac create myapp --use client

# Create from a local .jacpack file
jac create myapp --use ./my-template.jacpack

# Create from a local template directory
jac create myapp --use ./my-template/

# Create from a URL
jac create myapp --use https://example.com/template.jacpack

# List available jacpack templates
jac create --list-jacpacks

# Force overwrite existing
jac create myapp --force

# Create in current directory
jac create

See Also: Use jac jacpack to create and bundle custom templates.

jac check#

Type check Jac code for errors.

jac check [-h] [-e] [-w] [--ignore PATTERNS] [-p] [--nowarn] paths [paths ...]

Option	Description	Default
`paths`	Files/directories to check	Required
`-e, --print_errs`	Print detailed error messages	`True`
`-w, --warnonly`	Treat errors as warnings	`False`
`--ignore`	Comma-separated list of files/folders to ignore	None
`-p, --parse_only`	Only check syntax (skip type checking)	`False`
`--nowarn`	Suppress warning output	`False`

Examples:

# Check a file
jac check main.jac

# Check a directory
jac check src/

# Warnings only mode
jac check main.jac -w

# Check directory excluding specific folders/files
jac check myproject/ --ignore fixtures,tests

# Check excluding multiple patterns
jac check . --ignore node_modules,dist,__pycache__

jac test#

Run tests in Jac files.

jac test [-h] [-t TEST_NAME] [-f FILTER] [-x] [-m MAXFAIL] [-d DIRECTORY] [-v] [filepath]

Option	Description	Default
`filepath`	Test file to run	None
`-t, --test_name`	Specific test name	None
`-f, --filter`	Filter tests by pattern	None
`-x, --xit`	Exit on first failure	`False`
`-m, --maxfail`	Max failures before stop	None
`-d, --directory`	Test directory	None
`-v, --verbose`	Verbose output	`False`

Examples:

# Run all tests in a file
jac test main.jac

# Run tests in directory
jac test -d tests/

# Run specific test
jac test main.jac -t my_test

# Stop on first failure
jac test main.jac -x

# Verbose output
jac test main.jac -v

jac format#

Format Jac code according to style guidelines. For auto-linting (code corrections like combining consecutive has statements, converting @staticmethod to static), use jac lint --fix instead.

jac format [-h] [-s] [-l] paths [paths ...]

Option	Description	Default
`paths`	Files/directories to format	Required
`-s, --to_screen`	Print to stdout instead of writing	`False`
`-l, --lintfix`	Also apply auto-lint fixes in the same pass	`False`

Examples:

# Preview formatting
jac format main.jac -t

# Apply formatting
jac format main.jac

# Format entire directory
jac format .

Note: For auto-linting (code corrections), use jac lint --fix instead. See jac lint below.

jac lint#

Lint Jac files and report violations. Use --fix to auto-fix violations.

jac lint [-h] [-f] [--ignore IGNORE] paths [paths ...]

Option	Description	Default
`paths`	Files/directories to lint	Required
`-f, --fix`	Auto-fix lint violations	`False`
`--ignore`	Comma-separated files/folders to ignore	`""`

Examples:

# Report lint violations
jac lint main.jac

# Auto-fix violations
jac lint main.jac --fix

# Lint entire directory
jac lint .

# Lint excluding folders
jac lint . --ignore fixtures

Lint Rules: Configure rules via [check.lint] in jac.toml. All enabled rules are treated as errors.

jac enter#

Run a specific entrypoint in a Jac file.

jac enter [-h] [-m] [-r ROOT] [-n NODE] filename entrypoint [args ...]

Option	Description	Default
`filename`	Jac file	Required
`entrypoint`	Function/walker to invoke (positional)	Required
`args`	Arguments to pass	None
`-m, --main`	Treat as `__main__`	`True`
`-r, --root`	Root executor ID	None
`-n, --node`	Starting node ID	None

Examples:

# Run specific entrypoint
jac enter main.jac my_walker

# With arguments
jac enter main.jac process_data arg1 arg2

# With root and node
jac enter main.jac my_walker -r root_id -n node_id

Visualization & Debug#

jac dot#

Generate DOT graph visualization.

jac dot [-h] [-s SESSION] [-i INITIAL] [-d DEPTH] [-t] [-b] [-e EDGE_LIMIT] [-n NODE_LIMIT] [-o SAVETO] [-p] [-f FORMAT] filename [connection ...]

Option	Description	Default
`filename`	Jac file	Required
`-s, --session`	Session identifier	None
`-i, --initial`	Initial node ID	None
`-d, --depth`	Max traversal depth	`-1` (unlimited)
`-t, --traverse`	Enable traversal mode	`False`
`-c, --connection`	Connection filters	None
`-b, --bfs`	Use BFS traversal	`False`
`-e, --edge_limit`	Max edges	`512`
`-n, --node_limit`	Max nodes	`512`
`-o, --saveto`	Output file path	None
`-p, --to_screen`	Print to stdout	`False`
`-f, --format`	Output format	`dot`

Examples:

# Generate DOT output
jac dot main.jac -s my_session --to_screen

# Save to file
jac dot main.jac -s my_session --saveto graph.dot

# Limit depth
jac dot main.jac -s my_session -d 3

jac debug#

Start interactive debugger.

jac debug [-h] [-m] [-c] filename

Option	Description	Default
`filename`	Jac file to debug	Required
`-m, --main`	Run main entry	`True`
`-c, --cache`	Use cache	`False`

Examples:

# Start debugger
jac debug main.jac

Plugin Management#

jac plugins#

Manage Jac plugins.

jac plugins [-h] [-v] [action] [names ...]

Action	Description
`list`	List installed plugins (default)
`info`	Show plugin information
`enable`	Enable plugins
`disable`	Disable plugins
`disabled`	List disabled plugins

Option	Description	Default
`-v, --verbose`	Verbose output	`False`

Examples:

# List plugins (action defaults to 'list')
jac plugins

# Explicitly list plugins
jac plugins list

# Show info about a plugin
jac plugins info byllm

# Disable a plugin
jac plugins disable byllm

# Enable a plugin
jac plugins enable byllm

# List disabled plugins
jac plugins disabled

Note: To install or uninstall plugins, use pip install / pip uninstall directly. The jac plugins command manages enabled/disabled state for already-installed plugins.

💡 Popular Plugins:

jac-super: Enhanced console output with Rich formatting, colors, and spinners (pip install jac-super)

jac-client: Full-stack web development with client-side rendering (pip install jac-client)

jac-scale: Kubernetes deployment and scaling (pip install jac-scale)

Configuration Management#

jac config#

View and modify project configuration settings in jac.toml.

jac config [action] [key] [value] [-g GROUP] [-o FORMAT]

Action	Description
`show`	Display explicitly set configuration values (default)
`list`	Display all settings including defaults
`get`	Get a specific setting value
`set`	Set a configuration value
`unset`	Remove a configuration value (revert to default)
`path`	Show path to config file
`groups`	List available configuration groups

Option	Description	Default
`key`	Configuration key (positional, e.g., `project.name`)	None
`value`	Value to set (positional)	None
`-g, --group`	Filter by configuration group	None
`-o, --output`	Output format (`table`, `json`, `toml`)	`table`

Configuration Groups:

project - Project metadata (name, version, description)
run - Runtime settings (cache, session)
build - Build settings (typecheck, output directory)
test - Test settings (verbose, filters)
serve - Server settings (port, host)
format - Formatting options
check - Type checking options
dot - Graph visualization settings
cache - Cache configuration
plugins - Plugin management
environment - Environment variables

Examples:

# Show explicitly set configuration
jac config show

# Show all settings including defaults
jac config list

# Show settings for a specific group
jac config show -g project

# Get a specific value
jac config get project.name

# Set a value
jac config set project.version "2.0.0"

# Remove a value (revert to default)
jac config unset run.cache

# Show config file path
jac config path

# List available groups
jac config groups

# Output as JSON
jac config show -o json

# Output as TOML
jac config list -o toml

Deployment (jac-scale)#

jac start --scale#

Deploy to Kubernetes using the jac-scale plugin. See the jac start command above for full options.

jac start --scale           # Deploy without building
jac start --scale --build   # Build and deploy

jac destroy#

Remove a deployment.

jac destroy [-h] file_path

Option	Description	Default
`file_path`	Jac file to undeploy	Required

Examples:

jac destroy main.jac

Package Management#

jac add#

Add packages to your project's dependencies. Requires at least one package argument (use jac install to install all existing dependencies). When no version is specified, the package is installed unconstrained and then the installed version is queried to record a ~=X.Y compatible-release spec in jac.toml.

jac add [-h] [-d] [-g GIT] [-v] [packages ...]

Option	Description	Default
`packages`	Package specifications (required)	None
`-d, --dev`	Add as dev dependency	`False`
`-g, --git`	Git repository URL	None
`-v, --verbose`	Show detailed output	`False`

With jac-client plugin:

Option	Description	Default
`--npm`	Add as client-side (npm) package	`False`

Examples:

# Add a package (records ~=2.32 based on installed version)
jac add requests

# Add with explicit version constraint
jac add "numpy>=1.24"

# Add multiple packages
jac add numpy pandas scipy

# Add as dev dependency
jac add pytest --dev

# Add from git repository
jac add --git https://github.com/user/package.git

# Add npm package (requires jac-client)
jac add react --npm

jac install#

Sync the project environment to jac.toml. Installs all Python (pip), git, and plugin-provided (npm, etc.) dependencies in one command. Creates or validates the project virtual environment at .jac/venv/.

jac install [-h] [-d] [-v]

Option	Description	Default
`-d, --dev`	Include dev dependencies	`False`
`-v, --verbose`	Show detailed output	`False`

Examples:

# Install all dependencies
jac install

# Install including dev dependencies
jac install --dev

# Install with verbose output
jac install -v

jac remove#

Remove packages from your project's dependencies.

jac remove [-h] [-d] [packages ...]

Option	Description	Default
`packages`	Package names to remove	None
`-d, --dev`	Remove from dev dependencies	`False`

With jac-client plugin:

Option	Description	Default
`--npm`	Remove client-side (npm) package	`False`

Examples:

# Remove a package
jac remove requests

# Remove multiple packages
jac remove numpy pandas

# Remove dev dependency
jac remove pytest --dev

# Remove npm package (requires jac-client)
jac remove react --npm

jac update#

Update dependencies to their latest compatible versions. For each updated package, the installed version is queried and a ~=X.Y compatible-release spec is written back to jac.toml.

jac update [-h] [-d] [-v] [packages ...]

Option	Description	Default
`packages`	Specific packages to update (all if empty)	None
`-d, --dev`	Include dev dependencies	`False`
`-v, --verbose`	Show detailed output	`False`

Examples:

# Update all dependencies to latest compatible versions
jac update

# Update a specific package
jac update requests

# Update all including dev dependencies
jac update --dev

jac clean#

Clean project build artifacts from the .jac/ directory.

jac clean [-h] [-a] [-d] [-c] [-p] [-f]

Option	Description	Default
`-a, --all`	Clean all `.jac` artifacts (data, cache, packages, client)	`False`
`-d, --data`	Clean data directory (`.jac/data`)	`False`
`-c, --cache`	Clean cache directory (`.jac/cache`)	`False`
`-p, --packages`	Clean virtual environment (`.jac/venv`)	`False`
`-f, --force`	Force clean without confirmation prompt	`False`

By default (no flags), jac clean removes only the data directory (.jac/data).

Examples:

# Clean data directory (default)
jac clean

# Clean all build artifacts
jac clean --all

# Clean only cache
jac clean --cache

# Clean data and cache directories
jac clean --data --cache

# Force clean without confirmation
jac clean --all --force

💡 Troubleshooting Tip: If you encounter unexpected syntax errors, "NodeAnchor is not a valid reference" errors, or other strange behavior after modifying your code, try clearing the cache with jac clean --cache (rm -rf .jac) or jac purge. Stale bytecode can cause issues when source files change.

jac purge#

Purge the global bytecode cache. Works even when the cache is corrupted.

jac purge

When to use:

After upgrading Jaseci packages
When encountering cache-related errors (jaclang.pycore, NodeAnchor, etc.)
When setup stalls during first-time compilation

Command	Scope
`jac clean --cache`	Local project (`.jac/cache/`)
`jac purge`	Global system cache

Template Management#

jac jacpack#

Manage project templates. Bundle template directories into distributable .jacpack files or list available templates.

jac jacpack [action] [path] [-o OUTPUT]

Action	Description
`pack`	Bundle a template directory into a `.jacpack` file
`list`	List available templates (default)
`info`	Show information about a template

Option	Description	Default
`path`	Template directory (for pack) or `.jacpack` file (for info)	None
`-o, --output`	Output file path for bundled template	`<name>.jacpack`

Template Directory Structure:

A template directory should contain:

jac.toml - Project config with a [jacpack] section for metadata
Template files (.jac, .md, etc.) with {{name}} placeholders

To make any Jac project packable as a template, simply add a [jacpack] section to your jac.toml. All other sections become the config for created projects.

Example jac.toml for a template:

# Standard project config (becomes the created project's jac.toml)
[project]
name = "{{name}}"
version = "0.1.0"
entry-point = "main.jac"

[dependencies]

# Jacpac metadata - used when packing, stripped from created projects
[jacpack]
name = "mytemplate"
description = "My custom project template"
jaclang = "0.9.0"

[[jacpack.plugins]]
name = "jac-client"
version = "0.1.0"

[jacpack.options]
directories = [".jac"]
root_gitignore_entries = [".jac/"]

Examples:

# List available templates
jac jacpack list

# Bundle a template directory
jac jacpack pack ./my-template

# Bundle with custom output path
jac jacpack pack ./my-template -o custom-name.jacpack

# Show template info
jac jacpack info ./my-template
jac jacpack info mytemplate.jacpack

Using Templates with jac create:

Once a template is registered, use it with the --use flag:

jac create myproject --use mytemplate

jac js#

Generate JavaScript output from Jac code (used for jac-client frontend compilation).

jac js [-h] filename

Option	Description	Default
`filename`	Jac file to compile to JS	Required

Examples:

# Generate JS from Jac file
jac js app.jac

Utility Commands#

jac grammar#

Extract and print the Jac grammar.

jac grammar [-h] [--lark] [-o OUTPUT]

Option	Description	Default
`--lark`	Output in Lark format instead of EBNF	`False`
`-o, --output`	Write output to file instead of stdout	None

Examples:

# Print grammar in EBNF format
jac grammar

# Print in Lark format
jac grammar --lark

# Save to file
jac grammar -o grammar.ebnf

jac script#

Run custom scripts defined in the [scripts] section of jac.toml.

jac script [-h] [-l] [name]

Option	Description	Default
`name`	Script name to run	None
`-l, --list_scripts`	List available scripts	`False`

Examples:

# Run a script
jac script dev

# List available scripts
jac script --list

See Configuration: Scripts for defining scripts in jac.toml.

jac py2jac#

Convert Python code to Jac.

jac py2jac filename

Examples:

jac py2jac script.py

jac jac2py#

Convert Jac code to Python.

jac jac2py filename

Examples:

jac jac2py main.jac

jac tool#

Access language tools (IR, AST, etc.).

jac tool tool [args ...]

Available tools:

# View IR options
jac tool ir

# View AST
jac tool ir ast main.jac

# View symbol table
jac tool ir sym main.jac

# View generated Python
jac tool ir py main.jac

jac completions#

Generate and install shell completion scripts for the jac CLI.

jac completions [-h] [-s SHELL] [-i] [--no-install]

Option	Description	Default
`-s, --shell`	Shell type (`bash`, `zsh`, `fish`)	`bash`
`-i, --install`	Auto-install completion to shell config	`False`

When --install is used, the completion script is written to ~/.jac/completions.<shell> (e.g. ~/.jac/completions.bash) and a source line is added to your shell config file (~/.bashrc, ~/.zshrc, or ~/.config/fish/config.fish).

Installed files:

Shell	Completion script	Config modified
bash	`~/.jac/completions.bash`	`~/.bashrc`
zsh	`~/.jac/completions.zsh`	`~/.zshrc`
fish	`~/.jac/completions.fish`	`~/.config/fish/config.fish`

Examples:

# Print bash completion script to stdout
jac completions

# Auto-install for bash (writes to ~/.jac/completions.bash)
jac completions --install

# Generate zsh completions
jac completions --shell zsh

# Auto-install for fish
jac completions --shell fish --install

Note: After installing, run source ~/.bashrc (or restart your shell) to activate completions. Completions cover subcommands, options, and file paths.

jac lsp#

Start the Language Server Protocol server (for IDE integration).

jac lsp

Plugin Commands#

Plugins can add new commands and extend existing ones. These commands are available when the corresponding plugin is installed.

jac-client Commands#

Requires: pip install jac-client

jac build#

Build a Jac application for a specific target.

jac build [filename] [--client TARGET] [-p PLATFORM]

Option	Description	Default
`filename`	Path to .jac file	`main.jac`
`--client`	Build target (`web`, `desktop`)	`web`
`-p, --platform`	Desktop platform (`windows`, `macos`, `linux`, `all`)	Current platform

Examples:

# Build web target (default)
jac build

# Build desktop app
jac build --client desktop

# Build for Windows
jac build --client desktop --platform windows

jac setup#

One-time initialization for a build target.

jac setup <target>

Examples:

# Setup Tauri for desktop builds
jac setup desktop

Extended Flags#

Base Command	Added Flag	Description
`jac create`	`--use client`	Create full-stack project template
`jac create`	`--skip`	Skip npm package installation
`jac start`	`--client <target>`	Client build target for dev server
`jac add`	`--npm`	Add npm (client-side) dependency
`jac remove`	`--npm`	Remove npm (client-side) dependency

Common Workflows#

Development#

# Create project
jac create myapp
cd myapp

# Run
jac run main.jac

# Test
jac test -v

# Lint and fix
jac lint . --fix

Production#

# Start locally
jac start -p 8000

# Deploy to Kubernetes
jac start main.jac --scale

# Remove deployment
jac destroy main.jac

CLI Reference#

Quick Reference#

Core Commands#

jac run#

jac start#

jac create#

jac check#

jac test#

jac format#

jac lint#

jac enter#

Visualization & Debug#

jac dot#

jac debug#

Plugin Management#

jac plugins#

Configuration Management#

jac config#

Deployment (jac-scale)#

jac start --scale#

jac destroy#

Package Management#

jac add#

jac install#

jac remove#

jac update#

jac clean#

jac purge#

Template Management#

jac jacpack#

jac js#

Utility Commands#

jac grammar#

jac script#

jac py2jac#

jac jac2py#

jac tool#

jac completions#

jac lsp#

Plugin Commands#

jac-client Commands#

jac build#

jac setup#

Extended Flags#

Common Workflows#

Development#

Production#

See Also#