ironclaw/crates/ironclaw_engine/MONTY.md

Monty Integration

Monty is the embedded Python interpreter used for Tier 1 (CodeAct) execution. It's a lightweight Rust-native Python implementation — not CPython — so it has a restricted feature set.

Source: git = "https://github.com/pydantic/monty.git", tag = "v0.0.16" Pinned at: v0.0.16 (2026-04-19)

Upgrade Process

1. Update the pin: cargo update -p monty
2. Check for new features: cd ~/.cargo/git/checkouts/monty-*/*/ and git log --oneline since last pin
3. Update the preamble: If a previously-unsupported feature now works, remove it from the "Runtime environment" section in prompts/codeact_preamble.md
4. Update this file: Record the new pin and what changed
5. Run tests: cargo test -p ironclaw_engine
6. Watch traces: After deploying, check traces for new NotImplementedError patterns (self-improvement mission catches these)

Current Limitations (as of pin v0.0.16)

These are documented in prompts/codeact_preamble.md so the LLM avoids them:

Syntax not supported

Feature	Workaround
class Foo:	Use functions and dicts (host-provided dataclasses work)
with statements	Use try/finally or direct calls
match statements	Use if/elif chains
del statement	Reassign to None
yield / yield from statements	Generator expressions (x for x in ...) work; use lists for the rest
Type aliases (type X = ...)	Omit type annotations
Template strings (t-strings)	Use f-strings
Complex number literals	Use floats
Exception groups (try*/except*)	Use regular try/except

Limited standard library

import csv, import io, etc. still fail.

import os succeeds but all operations (os.getenv(), Path.*) are blocked by the executor — OSError: OS operations are not permitted in CodeAct scripts. This is intentional: agents must use injected tools (shell, read_file, etc.) instead.

Available built-in modules:

• asyncio — asyncio.gather() for parallel execution
• datetime — date and time handling
• json — JSON encoding/decoding
• math — standard math functions
• os.path — path string manipulation only (no I/O)
• re — regex (basic)
• sys — system info (limited)
• typing — type hints (limited, for annotation only)

Available builtins

abs, all, any, bin, chr, divmod, enumerate, filter, getattr, hasattr, hash, hex, id, isinstance, len, map, min, max, next, oct, ord, pow, print, repr, reversed, round, sorted, sum, type, zip

Host-provided functions (always available)

These are injected by the IronClaw executor, not by Monty:

• FINAL(answer) / FINAL_VAR(name) — terminate with result
• llm_query(prompt, context) — recursive LLM sub-call
• llm_query_batched(prompts) — parallel sub-calls
• rlm_query(prompt) — full sub-agent with tools
• globals() / locals() — returns dict of known tool names
• All tool functions (web_search, http, time, etc.)

Upgrade Changelog

Date	Pin	Notable changes
2026-04-19	v0.0.16	Mixed asyncio.gather() future-resolution panic fix, hasattr builtin, and input-safety hardening.
2026-04-10	v0.0.11	JSON perf improvements (~2x loads, ~1.6x dumps), filesystem mounting, Rust-side async API, mount edge case fixes.
2026-03-29	7a0d4b7	Multi-module imports, datetime module, json module, nested subscript assignment, str.expandtabs().
2026-03-20	6053820	Initial integration. max() kwargs support.