pydantic-monty-runtime

The monty command-line binary for the Monty sandbox.

Installing the wheel puts the compiled binary in the environment's scripts directory.

You normally don't install this directly — the pydantic-monty metapackage pulls it in alongside the Python bindings, which need it to spawn worker subprocesses. Install it on its own to get just the CLI, or to supply the binary to an existing pydantic-monty-client install:

uv add pydantic-monty-runtime
# or
pip install pydantic-monty-runtime

Or to install the monty binary as a tool

uv tool install pydantic-monty-runtime
monty --help

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
• --type-check-format — diagnostic format: full (default), concise, json, github and the other ty formats (requires --type-check)
• -m / --mount /host/path::/virtual/path[::mode[::write_limit_bytes]] — mount a host directory into the sandbox (ro, rw, or overlay); repeat for several, which need distinct virtual paths and disjoint host directories; an import of a module the sandbox does not bundle runs <cwd>/name/__init__.py, else <cwd>/name.py, from them, raising ModuleNotFoundError when neither exists
• --cwd /virtual/path — the sandbox's working directory (default: the first mount's virtual path, else /); relative paths resolve against it
• --max-memory 10MB, --max-feed-duration 0.5, --max-turn-duration, --max-recursion-depth, --gc-interval, --max-suspensions — sandbox resource limits
• --max-sleep 10 — longest wait a time.sleep() / asyncio.sleep() performs, in seconds; longer sleeps are cut short (inf for no limit)
• --max-total-sleep 30 — maximum cumulative time the host waits for those sleeps, in seconds; a sleep that would go over is refused (off unless given)

date.today(), datetime.now() and time.localtime() use the system clock in UTC; astimezone() and time.tzname also report that zone; time.time(), time.monotonic() and time.perf_counter() all return Unix epoch seconds. time.process_time() is always 0.0. time.sleep() and asyncio.sleep() wait for at most --max-sleep seconds each. An unseeded random draw uses system entropy. Rust embedders can change these defaults with MontyRun::with_os_policy; the CLI only exposes the sleep limits. os.urandom() raises NotImplementedError (or RuntimeError under --mount) because the CLI has no handler for it.

Worker mode

monty subprocess runs the binary as a wire-protocol child: framed protobuf requests on stdin, framed events on stdout. This is how pydantic-monty runs sandboxed code with crash isolation, and is meant to be driven by a parent process, not by hand.

The wheels are built from the monty-runtime crate; see its readme for cargo features, telemetry, and the rest of the Rust-side detail.