Law Client

Arxo Law

Run a rule. See the answer and why. Replay the result.

Checks npm Arxo on DevHunt

Try in browser · Run locally · Write rules · Publish a package · Install in VS Code · Connect MCP

SDK and CLI packages are available. Engine source is planned.

Run locally

With Node.js 20 or newer:

git clone \
  https://github.com/arxohq/law \
  arxo-law
cd arxo-law
npm ci --ignore-scripts
npm start

Your first rule
  Rule      Adult
  Input     Alice, age 20
  Answer    adult = yes
  Why       Applied Adult
  Missing   unknown (no age fact)
  Replay    identical evaluation bytes

Try npm start -- --age 16. The answer becomes unknown: this model has no rule establishing adulthood below 18. Then edit the rule and run again. Walk through the example →

Modelling on Arxo: public demonstrations

These public model repositories are demonstrations: a small sample of a much larger corpus of models on Arxo, chosen to show what modelling looks like across subjects. They share one language and runtime; each pins its sources, records its cases with their answers and states its scope per package.

One recorded question from five of them:

Start with chess in a fresh directory:

npm init -y
npm install --ignore-scripts @arxo/[email protected] @arxo/[email protected]

Save the chess README's example as example.mjs and run node example.mjs. Most other repositories run with the CLI: npm install -g @arxo/cli, clone the repository, then law eval examples/<case> as each README shows. The full list with observation details is in the ecosystem page.

Choose your next step

How an answer is built

Arxo compiles rules into a model, applies the supplied facts and attaches an explanation and canonical evaluation document. The examples execute locally after installation. Law is the first domain; standards and other rulebooks use the same machinery. A proof explains the selected model's answer.

Packages

npm and Python packages → · Editors, installations, browser tools and learning →

Explore and contribute

• npm run examples — run all three examples with readable output.
• npm --silent start -- --json — inspect the result summary, statuses and full hash.
• Example commands and expected results.
• Report a problem or ask a question.
• Contribution guide · source availability.

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Community · Books · Writings

arxo.io · Documentation · Apache-2.0