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Explore French benefit rules as executable models, and trace their answers back to published legal sources.

Explore the demo · Run an example · Read the book

First of all, a demonstration. This repository shows what modelling legislation with Arxo can do: French family-benefit law written as executable canons, with the source of every answer. It is an independent model built from published French law for teaching and demonstration. It does not claim legal accuracy or completeness, it is not an implementation by or for the Cnaf or any French authority, and its answers are not legal advice. For a real file, rely on the official texts and the competent bodies.

Choose your starting point

French Benefits Lab, captured on 12 October 2026. Open the demo and choose “Explore a saved family case” to inspect its inputs, answer and French sources. The lab presents its own recorded evidence release; its coverage and version are separate from this repository's export.

What it answers

The browser examples belong to the lab's recorded release. The local APL example below belongs to this repository's pinned model.

Use from Node.js

Node.js 20+. The pinned models are available as @arxo/canon-fr-benefits. Load one world and ask it through the common @arxo/law API:

npm install @arxo/law@0.4.2 @arxo/canon-fr-benefits@0.1.1

import { open } from '@arxo/law';
import { loadModel } from '@arxo/canon-fr-benefits/apl';
import { household, caseInput } from '@arxo/canon-fr-benefits/examples/apl';

const model = await loadModel();
const apl = await open(model.spec, {
  offline: true,
  local: { packages: { [model.spec]: model.package } },
});
const answer = await apl.collect('aide_formule', [household, '?amount'], caseInput);
console.log(answer.evaluationStatus); // COMPUTED
console.log(answer.value[0].value);   // '20.17' (EUR, formula amount)
console.log(apl.unfold('aide_formule', { depth: 2 }).text);

The input is the technical APL case below, with PpPlancherFinal selected. The answer includes the engine's canonical document, proof and hashes. This is a formula amount, not a final payable benefit. The package contains all 21 models; loading a subpath parses only the selected world.

Package API, model exports, TypeScript and verification limits. For maintainers: how to ship a canon with several models. Source models are pinned to the original public export; npm delivery checks are separate from full corpus acceptance, which remains not checked.

Quick start

You need Git, Node.js 20+ and npm. This example uses the released law 0.2.2 command-line tool, which executes the models. The package already includes its pinned dependency; no Python, source restoration or registry installation is needed for this scenario.

npm install -g @arxo/cli@0.2.2
law --version

git clone https://github.com/arxohq/arxo-cnaf.git
cd arxo-cnaf/packages/fr.apl

law test . --file tests/finish-lecture-pp.lawtest --json

This runs seven scenarios about the personal contribution in housing aid (article D. 823-17). Success means the command exits with code 0 and the JSON report records no failed scenarios. These are checks against the model's declared expectations, not certification of legal accuracy. The successful report includes these fields:

{"ok": true, "passed": 7, "failed": 0, "notRun": 0, "total": 7}

What to explore next: compare the readings, then open the scenario file.

Need help getting started? See Troubleshooting.

Example: one case, two readings

The model records two readings of the personal contribution in article D. 823-17. The choice enters at SensMinimumPp, an interpretation group that requires exactly one of PpPlancherFinal or PpLitteral.

The scenario fixes a single person with no dependants, zone II in metropolitan France, legal date 15 June 2024, supplied resources of €4,000 and zero rent. It also supplies ordinary housing, sole tenancy, zero solidarity rent reduction and no AAH/AEEH beneficiary. Zero rent deliberately isolates the reading difference; this is a technical probe, not a realistic aid claim.

The pinned parameters used in this probe are P0 = €37.91, Tp = 0.0283, R0 = €5,186, L = €0 and C = €58.08.

Both readings feed the same participation_personnelle relation. The same AideFormule rule then uses Af = L + C − Pp. These are exact formula amounts in the probe; neither is presented as the final payable benefit. The model leaves the choice explicit rather than selecting a reading for you.

The rules behind the amount

This is the native unfold response for aide_formule, rendered as a tree from the published fr.apl@0.1.0 world. Each rule exposes its premises, strength and source anchors. The two contribution producers are both visible: ParticipationPersonnelle and ParticipationPersonnelleLitterale.

No case, legal date or reading is selected. This shows the model's available rules, not which rules applied to a particular answer. The depth-limit markers come from the engine. Repeated article locators are grouped visually; the JSON retains every dated source anchor.

Full native JSON · Native text and labels · Reproduce these trees

Follow the map in the actual model:

Rules and exceptions

The same view for droit_ouvert shows a defeasible opening rule alongside its exception rules (defeater). Expanding surface_insuffisante exposes its own producers and an exception to that condition. fact, derived, judgment and test are distinct kinds of premise in the native response.

This is a map of declared rule structure across the published world, not an eligibility finding for a person. No case, date or reading is selected.

Full native JSON · Native text and labels · Declared exception scenarios

How to read a model

Published text → executable rules → dated case facts → answer and evidence.

A canon is a package containing a legal model, its source references and checks. A scenario supplies facts, dates and any selected interpretation, then states the expected answer. A pinned source is a captured publication identified by its provenance and a content hash, so the model's input can be checked later.

The rules are data in .law files, executed by law. This repository carries no separate implementation of the benefit formulas in application code. Models have individual scope and date boundaries; read a package's source and scenarios before applying its answers to a different case.

At a glance

Browse the models

The names below identify the subject of each model, not a claim of complete coverage of that benefit. The version and scenario inventory records the exported package versions and dependency counts.

Housing

Family and children

Disability and care

Income support

Shared rules and parameters

Formalization depth

Depth is recorded per model, against source revision f2efcc6. The unit is an article in a pinned publication edition: the same article can occur in several editions. Identical document bytes are counted once per package. Imports are excluded.

Executable / measured counts units with at least one deriving node. The other levels are I — executable only under an explicit interpretation; A — anchored without a deriving rule; S — source fragment only; N — no model node. An executable unit can still be only partly expressed. These counts describe the pinned excerpts, not the percentage of a benefit or of French law that is completely formalized.

† Partial measurement: some own publications or declared documents are outside the measured units; the report identifies them. Not measured means no declared source-document division was available for this method, not that the model has no executable rules. Rules / norms count own rule nodes and norm templates separately. Scenarios are the recorded export inventory; they were not rerun for this documentation update.

Method, boundaries and reproduction · Per-unit evidence

Find your way around the repository

The packages contain the public consumer kit; authoring reports and maintenance scripts are excluded. See public package contents for the preservation rules and the read-only guard.

For a case package that consumes these canons, follow Install the book examples. For compilation, scenario checks, replay and release rebuilds, follow Rebuild a source package.

Release and verification

Published with Law as Code in Practice: French Family Benefits (Law as Code by Country · Volume 1), available at Arxo Books.

The canons were exported on 12 October 2026 from Arxo commit 7206473829, with 1,985 scenarios passing on law 0.2.1 (law.core/0.2.11). The book's reproduction kit was checked with released law 0.2.2. These are recorded execution results for this export.

The packages workflow compiles each package, runs its scenarios on both evaluators, replays saved evaluations and rebuilds from the release using pinned law-package-tools 0.3.0. The registry workflow checks schemas, addresses and hashes. See the reproducibility guide for requirements and commands.

Found an error?

You do not need to know the rule language to report a problem. Open an issue with:

1. Where: the package, article or scenario, and the legal date.
2. What happened: fictional or anonymized input facts, the selected reading, your law --version, and the returned answer or test report.
3. What you expected: the relevant published source, its date/version, and the reasoning that leads to a different result.

Use fictional or anonymized examples; omit personal records and identifiers. If you mean the browser lab, include its page link and recorded release. A difference between readings may need an explicit alternative rather than a change to a shared rule. A confirmed defect should be accompanied by a scenario that reproduces it.

Cite this snapshot

Arxo (2026). French benefit rules on Arxo: executable, source-linked models. Canon export of 12 October 2026, public source revision f2efcc6788465484f145146a3ed5f76b13d41703.

@software{arxo_french_benefits_2026,
  author = {Arxo},
  title  = {French benefit rules on Arxo: executable, source-linked models},
  year   = {2026},
  url    = {https://github.com/arxohq/arxo-cnaf/tree/f2efcc6788465484f145146a3ed5f76b13d41703},
  note   = {Canon export: 12 October 2026; semantics: law.core/0.2.11}
}

For a particular result, also identify its package version, scenario or case, legal date and selected reading, and retain the execution evidence and hashes. The source revision above pins the exported canons; the lab is a separate release.

Rights and contact

Code and model: Apache-2.0. Captured publisher texts retain their own reproduction terms, listed per package in NOTICE; the code licence does not cover those texts. Some source files are withheld from redistribution.

Maintainer: Rifat Dzhumagulov · hi@arxo.io.