Monty

Detailed Introduction

Monty is a minimal, secure Python interpreter implemented in Rust, designed to safely execute LLM-generated Python code inside agents and model-driven workflows. By restricting the standard library, enforcing explicit external function boundaries, and applying resource limits, Monty avoids exposing the host environment while providing microsecond-level startup and a predictable execution model.

Main Features

• Microsecond startup and a small binary suitable for embedding in agent runtimes.
• Serializable execution snapshots that allow pausing and resuming state externally.
• Strict sandboxing: filesystem, network and env access are only available via developer-provided external functions.
• Optional type checking and bindings for Python, Rust and JavaScript hosts.

Use Cases

• Safely running LLM-generated code within agent architectures to call host-provided tools.
• Low-latency inline code execution where full container sandboxes are too heavy.
• Snapshot-and-resume workflows for suspending long-running tasks and migrating execution across processes.

Technical Features

• Implemented in Rust with no CPython dependency, making it portable across host languages.
• Fine-grained resource tracking (memory, stack depth, execution time) with cancel-on-limit semantics.
• Byte-serializable interpreter state for caching or cross-process transport.
• Intentionally limited language surface (restricted stdlib, limited syntax) to improve safety and auditability.