worldsim

Simulate how communities react to new rules, events, or policies — in TypeScript, in 5 minutes.

WorldSim is an embeddable multi-agent simulation engine for Node.js. Define agents with distinct personalities, drop in a policy change, and watch coalitions form, conflicts emerge, and consensus build — all powered by LLM reasoning loops.

Quick Start

npm install worldsim
OPENAI_API_KEY=sk-... npx worldsim demo
# Open http://localhost:4400 — watch a village react to water rationing

Or with Docker:

OPENAI_API_KEY=sk-... docker compose up
# Open http://localhost:4400

What You Can Simulate

Community Policy Impact — 8 villagers face a new water rationing policy. The farmer resists, the mayor defends, the priest mediates, the technologist proposes solutions. Who forms coalitions? Who complies?

Market Price Shocks — 10 marketplace agents react when grain prices double overnight. Sellers profit, buyers protest, regulators intervene. Economic reasoning emerges from personality-driven agents.

Information Cascades — 12 agents in 4 social groups. A rumor starts with one person. Watch it spread (or not) through the social graph, distorted by each personality along the way.

See evaluation/ for repeatable scenarios with expected behaviors and quality criteria.

Code Example

import { WorldEngine, ConsoleLoggerPlugin, InMemoryMemoryStore, InMemoryGraphStore } from "worldsim";

const world = new WorldEngine({
  worldId: "my-village",
  maxTicks: 20,
  llm: {
    baseURL: "https://api.openai.com/v1",
    apiKey: process.env.OPENAI_API_KEY!,
    model: "gpt-4o-mini",
  },
  memoryStore: new InMemoryMemoryStore(),
  graphStore: new InMemoryGraphStore(),
});

world.use(ConsoleLoggerPlugin);

world.addAgent({
  id: "maria", role: "person", name: "Maria Rossi",
  iterationsPerTick: 2,
  profile: { name: "Maria Rossi", personality: ["practical", "stubborn"], goals: ["Save the harvest"] },
  systemPrompt: "You are Maria, a farmer worried about water rationing.",
});

// Add more agents...

await world.start();

Studio Dashboard

WorldSim includes a built-in web dashboard for real-time simulation monitoring:

npx worldsim studio
# Open http://localhost:4400
# Optional: --port 5000, --no-open

• Live agent state — mood, energy, goals, status
• Event timeline — every action, every tick
• Relationship graph — force-directed visualization of social connections
• Simulation report — mood heatmaps, energy charts, action distribution, timeline
• Multi-world operations — monitor and compare multiple world runs (city/country shards)

Main sections available in the dashboard:

• Agents — inspect profile, current status, goals, mood and energy in real time
• Timeline — follow what happens at each tick, with a chronological event stream
• Relationship Graph — visualize who influences whom and how social ties evolve
• Report — review post-run metrics, trends, and behavior distribution

import { studioPlugin } from "worldsim";

engine.use(studioPlugin({ engine, port: 4400, memoryStore, graphStore }));

UI Examples

Relationship Graph view (real-time social connection map):

Agent Details view (profile, internal state, and memory timeline):

Architecture

flowchart LR
  WorldEngine --> RulesLoader
  WorldEngine --> PluginRegistry
  WorldEngine --> PersonAgent
  WorldEngine --> ControlAgent
  PersonAgent --> LLM
  ControlAgent --> LLM
  PersonAgent -.-> MemoryStore
  PersonAgent -.-> GraphStore

• WorldEngine orchestrates ticks, agents, plugins, and lifecycle
• PersonAgent — LangGraph-powered agents with personality, mood, energy, goals, and tool use
• ControlAgent — governance agent that monitors rules and can pause/stop violators
• Plugin system — hooks on every world event + registerable tools for agents
• Rules engine — load from JSON or PDF, with priorities and enforcement levels

Key Capabilities

| Feature | Description | | ------- | ----------- | | LLM-agnostic | OpenAI, Anthropic proxies, Ollama — anything OpenAI-compatible | | Personality system | Mood, energy, goals, beliefs, knowledge per agent | | Social dynamics | Relationship tracking with strength decay, neighborhoods | | Rule enforcement | Hard/soft rules, governance agent with autonomous control | | Scalability | 1000+ agents via concurrency caps, activity scheduling, token budgets | | Zero-config persistence | In-memory by default; plug in Redis, Neo4j, PostgreSQL for production | | Real-time streaming | Socket.IO events for live dashboards | | Simulation reports | Auto-generated analysis with mood heatmaps and action metrics |

Documentation

• Architecture & internals
• Persistence & databases
• Scaling to production
• Plugin authoring guide
• Evaluation scenarios
• Development roadmap

Contributing

See CONTRIBUTING.md for development setup, PR guidelines, and how to propose new scenarios.

License

MIT