A guide to writing Ruby on Rails applications, a web framework for Ruby, with attention to speed, security, and maintainability. It covers databases, controllers, models, views, APIs, caching, background jobs, and migrations.

Use it when writing, reviewing, or refactoring Rails controllers, models, views, APIs, database queries, caching, migrations, or background jobs.

It helps avoid slow database access, repeated queries, insecure endpoints, difficult-to-maintain business logic, and inefficient page rendering. It also provides patterns for handling work outside the main request, such as background jobs.

rails-dev — Skill for Claude Code and Codex by pproenca: A guide to writing Ruby on Rails applications, a…

Install

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.

agentmods

npx agentmods add skills/pproenca/dot-skills/rails-dev

Any agent

npx skills add pproenca/dot-skills --skill rails-dev

Clone the repo

git clone --depth 1 https://github.com/pproenca/dot-skills

Made for: Claude Code, Codex.

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/skills/pproenca/dot-skills/rails-dev.svg)](https://agentmods.dev/skills/pproenca/dot-skills/rails-dev)

Your own site

<a href="https://agentmods.dev/skills/pproenca/dot-skills/rails-dev"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/rails-dev.svg" alt="Measured on agentmods" height="20"></a>

Per session 94 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,748 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

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	$0.00094	$0.01748
Opus 5	$0.00047	$0.00874
Sonnet 5	$0.00019	$0.00350
Haiku 4.5	$0.00009	$0.00175

Measured 4d ago against content hash 79fda9003216, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

rails-dev 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.

skills/.curated/rails-dev/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Community Ruby on Rails Development Best Practices

Comprehensive performance and maintainability optimization guide for Ruby on Rails applications, maintained by Community. Contains 45 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when:

Writing new Rails controllers, models, or views
Optimizing ActiveRecord queries and database access patterns
Implementing caching strategies (fragment, Russian doll, low-level)
Building or refactoring API endpoints
Adding Turbo Frames and Streams for interactive UIs
Reviewing code for N+1 queries and security vulnerabilities
Designing background jobs with Sidekiq or Active Job
Writing or reviewing database migrations

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Database & ActiveRecord	CRITICAL	`db-`
2	Controllers & Routing	CRITICAL	`ctrl-`
3	Security	HIGH	`sec-`
4	Models & Business Logic	HIGH	`model-`
5	Caching & Performance	HIGH	`cache-`
6	Views & Frontend	MEDIUM-HIGH	`view-`
7	API Design	MEDIUM	`api-`
8	Background Jobs & Async	LOW-MEDIUM	`job-`

Quick Reference

1. Database & ActiveRecord (CRITICAL)

db-eager-load-associations - Eager load associations to eliminate N+1 queries
db-add-database-indexes - Add database indexes on queried columns
db-select-specific-columns - Select only needed columns
db-batch-processing - Use find_each for large dataset iteration
db-avoid-queries-in-loops - Avoid database queries inside loops
db-use-scopes - Define reusable query scopes on models
db-safe-migrations - Write reversible zero-downtime migrations
db-exists-over-count - Use exists? instead of count for existence checks

Read the full file on GitHub · 120 lines

Files

What ships with it

49 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

4d ago First seen · 120 lines · 94 tokens per session scan A 79fda9003216

Subscribe to this mod's changes

rails-dev is a skill published in the GitHub repository pproenca/dot-skills (201 stars, last pushed 18d ago), licensed MIT. It adds 94 tokens to every session and 1,748 once invoked, about $0.0005 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.

Backend and APIs Frontend Writing and docs

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brainstorming

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chat-perf

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chat-pet-sprite-creation

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cpu-profile-analysis

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