What is simengine CLAUDE.md?

Repository instructions for SimEngine, a decision-analysis system that simulates many possible futures from JSON-defined variables, logic, and risk limits. They also require the core Python engine to use only the standard library.

Use them when changing SimEngine's Python code, web or MCP/HTTP interfaces, licensing guidance, or optional Rust acceleration.

They help agents preserve the project's dependency-free design, licensing boundaries, and fallback behavior while editing it.

How cogswellspacely8-star/simengine configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to cogswellspacely8-star/simengine. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/cogswellspacely8-star/simengine/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/cogswellspacely8-star/simengine

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/cogswellspacely8-star/simengine/claude-md/github.svg)](https://agentmods.dev/instructions/cogswellspacely8-star/simengine/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/cogswellspacely8-star/simengine/claude-md"><img src="https://agentmods.dev/badge/instructions/cogswellspacely8-star/simengine/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/cogswellspacely8-star/simengine/claude-md"><img src="https://agentmods.dev/badge/instructions/cogswellspacely8-star/simengine/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 2,254 This file is loaded in full into every session.

When invoked 2,254 The same file — it is already loaded in full.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.02254	$0.02254
Opus 5.5	$0.00902	$0.00902
Sonnet 5.5	$0.00451	$0.00451
Haiku 4.5	$0.00225	$0.00225

Measured 2mo ago against content hash 67a50e3fd8ff, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

simengine CLAUDE.md scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

`v3/feeds/` (real-time data adapters like Polymarket Gamma) and `v3/llm/` (the natural-language front door) are also opt-in and network-touching, but stay inside the stdlib promise — they use only `urllib`. The core engi

CLAUDE.md · 125 lines

How it starts

The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md — SimEngine

What this is

A domain-agnostic Monte Carlo simulation and decision intelligence system. Define variables, logic, and risk tolerances in JSON; the engine simulates thousands of futures and (optionally) evolves toward strategies that respect safety constraints. Used both as a standalone web UI and as an MCP/HTTP tool for AI agents.

Open-core licensed. The engine in this repo is Apache 2.0. The hosted MCP service is commercial (see LICENSE-COMMERCIAL.md). Don't conflate the two when modifying licenses or deployment guidance.

Hard constraint: zero Python dependencies

The default engine uses only the Python standard library. This is a load-bearing design choice — it means SimEngine runs anywhere Python 3.8+ runs, no pip install required. Do not add requirements.txt entries or import statements that pull external packages into v3/*.py. If you think you need a third-party lib, you almost certainly don't — check kernel.py and bayesian.py for the pattern.

The Rust acceleration crates under crates/ are the only exception, and they're explicitly opt-in — the Python code falls back gracefully when simengine_native isn't importable.

v3/feeds/ (real-time data adapters like Polymarket Gamma) and v3/llm/ (the natural-language front door) are also opt-in and network-touching, but stay inside the stdlib promise — they use only urllib. The core engine never imports them. Treat any new feed as opt-in and ToS-careful: market data is an internal simulation input, never a rebroadcast feed or trade signal. The llm/ module turns a question into a config via a draft→validate→repair loop; the engine's own validate_config (in validation.py) grounds whatever the model produces.

Stack

Engine: Python 3.8+ stdlib (v3/kernel.py, v3/bayesian.py, v3/diagnostics.py, v3/calibration.py)
Web server: Python stdlib http.server (v3/server.py, port 8420)
UI: Single-page vanilla HTML/JS/CSS (v3/static/index.html) — no React, no framework, no build step
Native acceleration (optional): Rust crates at crates/simengine-core and crates/simengine-py (PyO3), built with maturin
Tests: Python unittest at v3/tests/
MCP server: v3/mcp_server.py (config: v3/mcp_config.json)
Natural-language front door (optional): v3/llm/ + the v3/sim_ask.py CLI + the /api/ask endpoint + the web "Ask anything" tab. Local-first via Ollama; OpenAI/Anthropic via env var.

Read the full file on GitHub · 125 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 125 lines · 2,254 tokens per session scan A 67a50e3fd8ff

Subscribe to this mod's changes

simengine CLAUDE.md is an instructions file published in the GitHub repository cogswellspacely8-star/simengine (0 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 2,254 tokens to every session, about $0.0090 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

simengine CLAUDE.md next to 6 instructions from other repositories
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simengine: Instructions file for Claude Code