Promise Lang

A statically-typed language designed for AI-agent efficiency.

Explicit ownership (like Rust), structured concurrency (like Go), algebraic error handling, generics, and exhaustive pattern matching — with zero hidden effects. Reading a single .pr file tells you exactly what it does. Native LLVM compilation to Linux, macOS, Windows, and WASM. Read the language design for the rationale behind these choices.

type Circle {
  f64 radius;
  get area f64 => 3.14159 * this.radius * this.radius;
}

main() {
  c := Circle(radius: 5.0);
  print_line("Area: {c.area}");
}

See agents build it

The Promise Zoo is a gallery of real programs built by AI agents — each learns Promise from the toolchain, then builds something end to end, recorded so you can watch exactly how it went.

A terminal recording of an AI agent building “hello, world” in Promise

Browse all recordings →

Install

Promise Lang is under active development — not for production use

To get started, install the VS Code extension (open source) — installing it sets up the Promise language for you, along with syntax highlighting and editor support.

Or install the toolchain directly. macOS (Apple Silicon) or Linux (x86_64):

curl -sSfL https://github.com/promise-language/promise/releases/latest/download/install.sh | sh

Windows (PowerShell):

irm https://github.com/promise-language/promise/releases/latest/download/install.ps1 | iex

The installer downloads a self-contained binary — compiler, stdlib, and LLVM toolchain — verifies its checksum, and sets up ~/.promise/. Then run promise version to verify.

GitHub Language Guide White paper Recordings