Installation

The canonical channel

cargo install axon-lang

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

The historical PyPI line is closed. The Python interpreter was retired in v2.0.0 and the package is now a tombstone that redirects here. The language implementation is 100% Rust + C23.

Prerequisites

Requirement	Why
Rust 1.95+	The rust-version in every manifest. An older toolchain fails with an MSRV error, not a compile error.
A working C compiler (MSVC / clang / gcc)	ring — reached through rustls, which is how this compiler speaks HTTPS to every model provider — compiles C unconditionally in its build script. On Windows the MSVC Build Tools suffice; on Debian or Ubuntu, build-essential.

These are checked at build time, not install time. If cargo install stops with a cc or linker error rather than a Rust error, the C toolchain is what is missing.

On the C requirement, precisely. There used to be two sources of it. One was ours: axon-csys, which compiles the C23 tokenizer and cryptographic kernels, was a hard dependency — so a machine without cc did not get a slow install, it got exit 101. That one is gone. The kernels now live behind --features csys-native, and the default build serves the same API from pure-Rust twins that the same drift gates judge.

The other source is ring, and it is not ours to remove.

Features

The default install is the compiler and the governance CLI — check, compile, run, dossier, sbom, audit, pcc prove, pcc verify — and it adds no dependencies beyond that. Everything heavier is opt-in:

Feature	What it turns on	What it costs
cli (default)	the compiler + governance surface	—
server	the HTTP / SSE / NDJSON / WebSocket server, and the axon-server binary	the axum service stack
postgres	the axonstore data plane against real PostgreSQL	~36 crates — the single largest lever on install time
documents	the OOXML surface and axon evidence-package	pure-Rust compression
csys-native	the C23 kernels: exact BPE token counts, the crypto boundary	needs a C toolchain

Leaving csys-native off is bounded and labelled, not silent: count_tokens returns an estimate instead of an exact BPE count, and mandate drops its Tier 1 logit-bias bans — while Tier 2, the refinement loop that is the guarantee, is untouched.

Verify the install

axon --version
axon check app.axon

Both axon --version and axon version print the same string.