Xz

A general-purpose programming language for code that machines write and people have to trust.

AI models write production code faster than anyone can read it. Writing is no longer the bottleneck; deciding what to trust is. Xz is built around that shift, so a reviewer can answer the important questions from the signature instead of the body:

Reviewer's question	Where Xz answers it
What does it do?	@intent, checked against the code
What can it change?	mut bindings and @effects
What are its guarantees?	pre / post contracts
What can go wrong?	Result[T, E] on a single error channel

A documented claim that the code does not satisfy fails the build. A claim the compiler cannot prove needs a human @trusted stamp. A comment cannot quietly lie about the code it describes.

A look at the language

/// Returns the principal square root of x.
/// @intent  Returns the square root of a non-negative number.
/// @requires x is non-negative
/// @ensures result is ok implies result.value >= 0.0
/// @effects none
func sqrt(x: Float) -> Result[Float, DomainError]
    pre  x >= 0.0
    post result is ok implies result.value >= 0.0
{
    if x < 0.0 {
        err(DomainError("negative input"))
    } else {
        ok(approx_sqrt(x))
    }
}

The contract is not a convention someone may forget. The compiler reads it.

Build and run

Xz needs a current Rust toolchain and a portable LLVM 17 install. The setup script checks the LLVM install and prints the two environment variables the backend expects.

git clone https://github.com/x1zzdev/Xz.git
cd Xz/xz-cli
scripts/setup-llvm.sh
cargo run -- run ../examples/hello.xz

The same command works for the other examples: contracts.xz, concurrency.xz, async.xz, ffi.xz, lists.xz, maps.xz, sets.xz, io.xz, time.xz. See examples/README.md for what each one shows.

Status

The compiler is usable today. The front end (xz check) and the LLVM JIT backend (xz run) work. The C ABI bridge, shared-library output (xz build --shared), and generated Python ctypes bindings (xz bind --lang python) are in. Typed channels, a deterministic task scheduler, and async/await run on the JIT path. The language server (xz lsp), the formatter (xz fmt), and the package commands (xz pkg gen, xz pkg add) are available.

Phases 1 through 4 are complete, and the remaining phases are partly implemented. The real state of each phase is tracked in docs/08-roadmap.md, not in a status table that goes stale.

Documentation

The specification lives in docs/. Start with the philosophy, then read the part that matches your interest.

Document	Contents
01-philosophy.md	The thesis and the reviewer's questions
02-syntax.md	Syntax and the shape of a program
03-type-system.md	Types and contract-point explicitness
04-memory-model.md	Value semantics and explicit mutation
05-concurrency.md	Structured concurrency and typed channels
06-error-handling.md	Result types and one error channel
07-compiler.md	Diagnostics, formatter, and language server
08-roadmap.md	What is done and what is next
09-intent-verification.md	How declared behavior is checked
10-ffi-interop.md	C ABI bridge and Python bindings
11-grammar.md	The authoritative grammar
12-stdlib.md	The standard library surface
13-codegen.md	The LLVM backend and runtime
14-codegen-notes.md	Backend problems and the decisions that settled them
15-ecosystem.md	Host integrations built on the Xz core

A Korean overview is available at README_kr.md.

Ecosystem

Xz is the language and the compiler. Frameworks connect to it through the C ABI and the .xzint interface format, so a host integration can be built without changing the language itself.

Project	Host	Role
Xz (this repository)	none	Language, specification, compiler, LLVM backend, C ABI, .xzint
next.xz	Next.js / TypeScript	Binding generation, Bun FFI and Wasm loader, agent loop, /___audit overlay
rails.xz	Ruby on Rails	Ruby FFI bridge, ActiveJob agent loop, /xz_audit engine

Each toolkit follows the same path: an agent writes a contracted .xz module, xz check-json drives the repair loop, xz build --shared produces the library, and a human approves the contracts in the host's audit view. The core does not change for each framework, and that is the point. See docs/15-ecosystem.md.

Contributing

Contributions are welcome, and the process is meant to be boring. Read CONTRIBUTING.md for the build, the test loop, and the two rules that matter: spec before implementation, and one logical change per commit. Everyone participating agrees to the Code of Conduct.

Support and security

Questions and ideas go to GitHub Discussions or the issue tracker. Report vulnerabilities privately as described in SECURITY.md, never in a public issue.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option. Unless you explicitly state otherwise, any contribution you submit for inclusion in this project, as defined in the Apache-2.0 license, is dual licensed as above, with no additional terms.

Xz is a programming language and is unrelated to the xz compression utility.