axon-lang

AXON — the formal cognitive language: a deterministic, proof-carrying AI runtime.

AXON is a programming language for AI cognition in which the properties you care about — this endpoint may not leak regulated data, this agent may not exceed this budget, this credential may not outlive this session — are type errors, checked before anything runs, rather than conventions enforced by code review.

The crate publishes as axon-lang; the library import is use axon::*.

The language reference, the design papers and the full documentation live in the repository README. This page is the crate's landing page: what you get, how to install it, and how to watch it refuse something.

Install

cargo install axon-lang

This installs the axon binary. If the build stops with a cc/linker error rather than a Rust error, the C toolchain is what is missing.

See it work

echo 'type PatientRecord compliance [HIPAA, GDPR] { ssn: String }
shield PHIShield { scan: [pii_leak] on_breach: halt severity: critical
                   compliance: [HIPAA, GDPR] }
axonendpoint Api { method: POST path: "/p" body: PatientRecord
                   execute: F output: FlowEnvelope<PatientRecord> shield: PHIShield
                   backend: anthropic compliance: [HIPAA, GDPR] }
flow F(ssn: String) -> PatientRecord {
  step R { ask: "summarize" output: PatientRecord } }' > app.axon


axon check   app.axon                  # compile-time compliance verification

axon dossier app.axon                  # regulatory posture, as JSON

axon audit   app.axon --framework all  # per-framework gap analysis

Now delete shield: PHIShield from the endpoint and check again:

X app.axon  1 error(s)
  error [line 4]: axon-T957 axonendpoint 'Api' carries regulated data
  (kappa = {GDPR, HIPAA}) across a trust boundary but declares no `shield:`.
  Regulated boundaries require a shield whose `compliance:` covers the type's
  kappa — ESK Fase 6.1 coverage rule. […] Declaring the classes on the
  endpoint's own `compliance:` does NOT cover them: that list is a label,
  the shield is the control that acts on a breach.

axon check exits 1. That is the whole idea: the regulatory property rides on the type system, so it holds at compile time or it does not hold at all.

What's in the box

One binary, 28 subcommands. The ones you are most likely to reach for:

axon --help lists all of them.

As a library

[dependencies]

axon-lang = "2"

use axon::*;

Building tooling rather than running programs? The compiler frontend — lexer, parser, AST, epistemic type system, type checker, IR generator — is a separate crate, axon-frontend, with zero runtime dependencies. An LSP, a linter or an analyzer should depend on that and skip the server, database and HTTP stack entirely.

API keys

Only needed to execute flows against real backends — never for axon check, axon compile, axon dossier, axon audit or axon run --tool-mode stub. Seven backends are supported (Anthropic, OpenAI, Gemini, Kimi, GLM, OpenRouter, Ollama); see the repository README for the environment variables each expects.

License

AGPL-3.0-or-later — see LICENSE. Commercial licensing and the enterprise layer are described in the repository.