littrs 0.3.0

A minimal, secure Python sandbox for AI agents

littrs

A minimal, secure Python sandbox for AI agents.

Installation

pip install littrs

Quick Start

from littrs import Sandbox, WasmSandbox

# Simple sandbox (fast, in-process)
sandbox = Sandbox()
sandbox.execute("x = 10")
result = sandbox.execute("x * 2")
print(result)  # 20

# WASM sandbox (stronger isolation, recommended for untrusted code)
wasm = WasmSandbox()
result = wasm.execute("sum(range(100))")
print(result)  # 4950

Features

• Secure by default: No file system, network, or OS access
• Two isolation levels:
  • Sandbox: Fast, in-process execution
  • WasmSandbox: WebAssembly isolation (recommended for untrusted code)
• Tool registration: Register Python functions callable from the sandbox
• Resource limits: Control computation (fuel) and memory usage

Registering Tools

from littrs import Sandbox

def fetch_data(args):
    id = args[0] if args else 0
    return {"id": id, "name": "Example"}

sandbox = Sandbox()
sandbox.register_function("fetch_data", fetch_data)

result = sandbox.execute("fetch_data(42)")
print(result)  # {'id': 42, 'name': 'Example'}

WASM Sandbox with Limits

from littrs import WasmSandbox, WasmSandboxConfig

# Configure resource limits
config = WasmSandboxConfig() \
    .with_fuel(1_000_000) \
    .with_max_memory(32 * 1024 * 1024)  # 32MB

sandbox = WasmSandbox(config)

# This will run out of fuel and raise an error
try:
    sandbox.execute("while True: pass")
except RuntimeError as e:
    print("Stopped:", e)

Supported Python Features

• Basic types: None, bool, int, float, str, list, dict
• Arithmetic, comparison, and boolean operators
• Control flow: if/elif/else, for, while
• Built-in functions: len(), range(), str(), int(), print(), etc.

Not Supported

• import statements
• Class definitions
• File I/O
• Network access
• Any standard library

License

Apache-2.0