What is openmc CLAUDE.md?

A set of Claude Code instructions for the OpenMC project, including how the coding agent should behave on its first call.

Use it when working with Claude Code in the OpenMC repository.

It gives the agent project-specific guidance instead of leaving it to guess how OpenMC should be handled.

How openmc-dev/openmc configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to openmc-dev/openmc. 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/openmc-dev/openmc/develop/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/openmc-dev/openmc

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/openmc-dev/openmc/claude-md/github.svg)](https://agentmods.dev/instructions/openmc-dev/openmc/claude-md)

Your own site

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

Per session 144 This file is loaded in full into every session.

When invoked 144 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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	$0.00144	$0.00144
Opus 5.5	$0.00058	$0.00058
Sonnet 5.5	$0.00029	$0.00029
Haiku 4.5	$0.00014	$0.00014

Measured 5d ago against content hash 61300dfa30a1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

openmc CLAUDE.md scanned grade A with 0 findings 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 5d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 15 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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.

5d ago First seen · 15 lines · 144 tokens per session scan A 61300dfa30a1

Subscribe to this mod's changes

openmc CLAUDE.md is an instructions file published in the GitHub repository openmc-dev/openmc (1,134 stars, last pushed 4d ago), with no licence file. It adds 144 tokens to every session, about $0.0006 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-11-01.

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