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, or the language guide for the language itself.

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.

Browse all recordings

Accelerate Promise

Promise is built by AI agents directed by one maintainer, and everything here — the compiler, the standard library, the toolchain — was built on a single ~$200/month subscription. The maintainer sets direction but isn't in the loop that writes, tests, and fixes the code, so progress isn't gated on how much one person can review. The budget, not anyone's time, is the speed limit — which makes the math unusually simple: roughly every $250/month is one more agent working full time. The first $250 is close to a doubling. Whether it keeps scaling past that is an open question — some of the work is serial no matter how many agents you have — and measuring it is part of the point. What the money bought gets published monthly, including when it hits a ceiling.

Sponsor Promise

Install

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 or arm64):

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. Prebuilt binaries for every supported target are on the releases page.

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