Borrowing it
Nothing to install: this file belongs to steveclarke/real-world-rails. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/steveclarke/real-world-rails/main/CLAUDE.mdgit clone --depth 1 https://github.com/steveclarke/real-world-railsWrote 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.
[](https://agentmods.dev/instructions/steveclarke/real-world-rails/claude-md)<a href="https://agentmods.dev/instructions/steveclarke/real-world-rails/claude-md"><img src="https://agentmods.dev/badge/instructions/steveclarke/real-world-rails/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.
<a href="https://agentmods.dev/instructions/steveclarke/real-world-rails/claude-md"><img src="https://agentmods.dev/badge/instructions/steveclarke/real-world-rails/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00270 | $0.00270 |
| Opus 5 | $0.00135 | $0.00135 |
| Sonnet 5 | $0.00054 | $0.00054 |
| Haiku 4.5 | $0.00027 | $0.00027 |
Grade A, and why
real-world-rails 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 10d 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.
What it actually says
Real World Rails
This repository contains 200+ production open source Rails applications and engines as git submodules.
apps/— Full source code of Rails applications (Discourse, Mastodon, GitLab, Gumroad, Chatwoot, Spree, Solidus, Canvas LMS, and many more)engines/— Rails engines (Blazer, PgHero, Ahoy, Chartkick, Thredded, etc.)repos.md— Full list with descriptionsanalyses/— Git-ignored directory for local research (not committed)
How to use this repo
Search across all apps to find how production codebases implement patterns. For example:
- Grep for gem usage: search
Gemfile.lockfiles acrossapps/ - Find model patterns: search
app/models/across all apps - Compare approaches: look at how multiple apps solve the same problem
- Study migrations, concerns, service objects, jobs, mailers, etc.
Key details
- Submodules point to specific commits; run
bin/updateto get the latest - Some apps are very large (GitLab, Canvas LMS, Discourse) — searches may take time
- The
analyses/directory is git-ignored for storing local research
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.
- 10d ago First seen · 24 lines · 270 tokens per session scan A 8be57f961d15
real-world-rails CLAUDE.md is an instructions file published in the GitHub repository steveclarke/real-world-rails (538 stars, last pushed 2d ago), licensed MIT. It adds 270 tokens to every session, about $0.0014 per session on Opus 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 2026-08-30.
Other instructions, from other repositories
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.