loom-engine-rpg 3.0.0

Deterministic TTRPG simulation core for AI-run games - the Python surface of loom-engine. Engine-is-truth: seeded, replay-safe rules the AI narrates but cannot invent.

loom-engine (Python)

The Python surface of loom-engine - a deterministic rules core for AI-run tabletop and RPG games.

pip install loom-engine-rpg   # the bare 'loom-engine' name is taken on PyPI

import loom_engine            # the import name is loom_engine

The design principle: the engine is truth. Dice, action economy, initiative, range, conditions, reactions, and validation are resolved by pure, replay-safe code. An AI narrator can describe the outcome, but it never gets to invent the roll, change the numbers, or rewrite what happened.

This package is a byte-parity port of the TypeScript engine: the same inputs produce identical results in Python (your server/backend) and TypeScript (the browser), so a server-authoritative resolution and a client one can never disagree. That parity is enforced by a shared cross-language golden-vector suite.

Modules (v2.3.0)

• loom_engine.range_bands - grid-free Engaged/Near/Far positioning.
• loom_engine.reaction_economy - the per-round "1 reaction per combatant" ceiling.
• loom_engine.narration_contract - find_invented_number: reject prose that states a mechanics number the engine never produced (numerals and number-words).
• loom_engine.ruleset - 5e + PF2e action economy, initiative ordering, conditions.

Pure stdlib, zero runtime dependencies. Compatible with the D&D 5e SRD (CC-BY-4.0) and the Pathfinder 2e Remaster ruleset (ORC License); see ../NOTICE.md. Not affiliated with or endorsed by Wizards of the Coast or Paizo.

Determinism

These modules use ordered dicts + explicit sorts for all logic (never hash() ordering). For any cross-language hashing, serialize with json.dumps(obj, sort_keys=True, separators=(',', ':')) and run with PYTHONHASHSEED=0. Floats are banned in deterministic paths.