LaskTasks in pinned containers, checked before they run

Tasks are typed functions in one file. Their commands run in container images pinned by digest, the same on your laptop and in CI, and never on the host unless the file says so.

Get started

Why Lask

GitHub

// main.lask
alpine = #alpine:3.22.2

// Say hello from a container.
greet(--name = "World") =
  $[alpine] echo "Hello, #{name}!"

$ lask check
$ lask sync
$ lask run greet --name Lask

Checked before it runs

lask check resolves every name, argument and type, and the environment of every command, without running anything. Your editor shows the same errors as you type.

Pinned images

Declare once that go comes from #golang:1.25. lask sync records the image's digest, and every machine runs that image.

No implicit host

A command whose program has no declared environment is a check error. Commands run on the host only where you write #local.

Tasks are functions

Tasks have typed parameters, defaults and return values. if, case, try/catch and async are part of the language, so there is no shell glue to get wrong.

A command line for every task

deploy(dry_run = true) in Lask is the same call as lask run deploy --dry-run true from the shell, and the comment above the task is its --help.

Reuse across projects

Import tasks, and the images they run in, from other repositories. The lock file pins each one by content hash.

Lask in one minute, in five steps: try a command in the REPL, keep it as a task, run it, run the same thing on a laptop and in CI, and keep secrets in Vault.

A main.lask that lints and tests a Python project, with neither Python nor the linter installed:

lask

// Each program comes from a pinned image.
command { "python" } on #python:3.13.7-alpine3.22
command { "ruff" } on #ghcr.io/astral-sh/ruff:0.13.3-alpine

// Lint and test at the same time.
ci() = do {
  lint = async $ ruff check app
  test = async $ python -m unittest discover -s app
  all([lint, test])
}

bash

$ lask sync      # pull both images and pin their digests in lask.lock.json
$ lask run ci    # run both commands, each in its own container

Misspell python as pyhton on line 8, and lask check reports it before anything runs:

text

$ lask check
main.lask:8:16-8:52: E-TYPE-COMMAND-NOENV [static]: 'pyhton' is not a declared command; ...

Your first real task file builds this file step by step.