Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/levifig/rails-instructions/rails-securitygit clone --depth 1 https://github.com/levifig/rails-instructionsWrote 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/levifig/rails-instructions/rails-security)<a href="https://agentmods.dev/instructions/levifig/rails-instructions/rails-security"><img src="https://agentmods.dev/badge/instructions/levifig/rails-instructions/rails-security.svg" alt="Measured on agentmods" 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 | $0.01088 | $0.01088 |
| Opus 5 | $0.00544 | $0.00544 |
| Sonnet 5 | $0.00218 | $0.00218 |
| Haiku 4.5 | $0.00109 | $0.00109 |
Grade A, and why
rails-instructions rails-security.instructions.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 4d 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.
How it starts
The opening of the file, as written. The whole thing — 238 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Security Guide
Core Philosophy
- Security is not optional, it's fundamental
- Follow the principle of least privilege
- Never trust user input
- Defense in depth - multiple layers of security
- Stay updated with security best practices
Authentication Principles
- Use Rails built-in authentication generator
- Implement secure password requirements
- Use has_secure_password for password handling
- Implement session timeouts
- Support multi-factor authentication when needed
Authorization Strategy
- Authenticate every request
- Authorize every action
- Fail closed - deny by default
- Check permissions at multiple levels
- Log authorization failures
Strong Parameters
- Always use strong parameters
- Whitelist allowed attributes explicitly
- Never permit entire parameter hashes
- Handle nested attributes carefully
- Document permitted parameters
SQL Injection Prevention
- Use parameterized queries always
- Avoid string interpolation in queries
- Use Active Record query interface
- Sanitize user input when necessary
- Review raw SQL carefully
Cross-Site Scripting (XSS)
- Escape output by default
- Use Rails sanitize helpers appropriately
- Be careful with raw and html_safe
- Implement Content Security Policy
- Validate and sanitize user input
Cross-Site Request Forgery (CSRF)
- Enable CSRF protection globally
- Include tokens in all forms
- Verify tokens on state-changing requests
- Handle AJAX requests properly
- Document any CSRF exceptions
Session Security
- Use secure session storage
- Implement session expiration
- Regenerate session IDs after login
- Clear sessions on logout
- Monitor for session hijacking
Password Management
- Enforce strong password policies
- Never store passwords in plain text
- Use bcrypt for password hashing
- Implement password reset securely
- Support password managers
API Security
- Use token-based authentication
- Implement rate limiting
- Version APIs from the start
- Use HTTPS exclusively
- Validate API input thoroughly
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.
- 4d ago First seen · 238 lines · 1,088 tokens per session scan A eafa6a98e8d7
rails-instructions rails-security.instructions.md is an instructions file published in the GitHub repository levifig/rails-instructions (54 stars, last pushed 1y ago), licensed MIT. It adds 1,088 tokens to every session, about $0.0054 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.
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