pydantic-monty-runtime

The monty command-line binary for the Monty sandboxed Python interpreter.

$ monty -c "print('hello world')"
hello world

Usage

• monty — start an interactive REPL
• monty file.py — run a Python file
• monty -c "<code>" — run a program passed as a string (like python -c)
• -i / --interactive — run the file or -c program in a REPL session (like python -i)
• -t / --type-check — type check (powered by ty) before executing
• -m / --mount /host/path::/virtual/path[::mode[::write_limit_bytes]] — mount a host directory into the sandbox (ro, rw, or overlay)
• --max-memory 10MB, --max-duration 0.5, --max-allocations, --max-recursion-depth, --gc-interval — sandbox resource limits

Worker mode

monty subprocess runs the binary as a wire-protocol child: framed protobuf requests on stdin, framed events on stdout (see the monty-proto crate). This is how the monty-pool crate — and through it the pydantic-monty and @pydantic/monty packages — runs Monty with crash isolation. It is meant to be driven by a parent process, not by hand.

PyPI packaging (pydantic-monty-runtime)

The binary is also packaged for PyPI as pydantic-monty-runtime, the same way uv and ruff package theirs: installing the wheel places the compiled binary in the environment's scripts directory. It exists so that pydantic-monty can find a monty binary without any manual setup, and is installed automatically as a dependency of that package — you normally don't install it directly.

Monty crates

• monty — the core interpreter: Python parser, bytecode VM, and sandbox.
• monty-types — the shared boundary data types (values, exceptions, OS calls, resource limits) hosts use without linking the interpreter.
• monty-fs — host-side filesystem mounts: maps virtual sandbox paths to real host directories.
• monty-runtime — the monty binary: REPL, file runner, and subprocess worker mode. this crate
• monty-pool — an elastic pool of crash-isolated monty worker subprocesses.
• monty-proto — the protobuf wire protocol spoken between pool parents and workers.
• monty-type-checking — type checking of sandboxed code, powered by ty.
• monty-typeshed — the trimmed typeshed stubs describing the stdlib subset Monty implements.
• monty-macros — the proc macros behind monty's argument parsing.