staal

Staal is the programming language for agents, built for what they do: sending messages, moving money, changing records. Its compiler refuses a program that could act without permission, use a model's answer unchecked, let untrusted text instruct a model, or overspend its budget, and its runtime journals every action so a crashed run resumes without repeating one.

This package installs the staalc compiler and runtime, and a Python interface to it. No Rust toolchain is needed.

pip install staal
staalc check program.staal
staalc run program.staal

From Python, through Staal's C interface. Your app decides the policy (here, a refund limit per customer tier) and Staal enforces it:

import staal
lib = staal.Library()          # the library installed with this package
limit = 500 if customer["tier"] == "gold" else 50
out = lib.run("refund.staal", {
    "entry": "main",
    "inputs": {"complaint": complaint},
    "grants": {"pay": {"cap": "payments.refund", "each": {"amount": str(limit), "currency": "USD"}}},
    "model": {"provider": "anthropic", "model": "claude-sonnet-5-5", "api_key": {"env": "ANTHROPIC_API_KEY"}},
}, journal="refund.journal")
if out["status"] == "done":
    print(out["result"])

Every call returns the JSON object described in include/staal.h, as a dict. staalc build also needs a C compiler (cc) to link executables.

Platforms. Python 3.8 or newer, on Linux (x86_64 and arm64, glibc 2.28 or newer) and macOS (Apple Silicon, macOS 11 or newer; Intel, macOS 10.12 or newer), from 0.24.0. Version 0.23.0 has Linux x86_64 and macOS 15 wheels only. Elsewhere, build from source.

Status. A preview: tested on all four platforms above, with no independent security review yet. The tutorial takes about an hour.

Licence. Apache-2.0 WITH LLVM-exception. The package contains staalc and its Rust dependencies, whose licences are in LICENSE-THIRD-PARTY.txt.