What is rails-upgrade?

A planning guide for updating Ruby on Rails applications, a framework for building web applications, across versions 2.3 to 8.1. It follows each version in order and documents changes that may affect the application.

Use it to assess an application's upgrade path, plan upgrades across several Rails versions, and create reports with version-specific findings and instructions.

It helps reveal breaking changes and removed or outdated features before an upgrade causes problems. It also turns a large upgrade into documented migration steps.

rails-upgrade — Skill for Claude Code by ombulabs

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.

Any agent

npx skills add ombulabs/claude-code_rails-upgrade-skill --skill rails-upgrade

Clone the repo

git clone --depth 1 https://github.com/ombulabs/claude-code_rails-upgrade-skill

Made for: Claude Code.

Or install rails-upgrade, the plugin that ships this one along with the rest of its 1 skill, 1 plugin.

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/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade/github.svg)](https://agentmods.dev/skills/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade)

Your own site

<a href="https://agentmods.dev/skills/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade"><img src="https://agentmods.dev/badge/skills/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade/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/skills/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade"><img src="https://agentmods.dev/badge/skills/ombulabs/claude-code_rails-upgrade-skill/rails-upgrade.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 7,866 The whole file, excluding the scripts and references it only reads on demand.

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

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high Privilege Escalation · line 124
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 153
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.

How audits are shown

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	$0.00073	$0.07866
Opus 5	$0.00036	$0.03933
Sonnet 5	$0.00015	$0.01573
Haiku 4.5	$0.00007	$0.00787

Measured 11d ago against content hash 442ff55e5a27, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

rails-upgrade 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 11d 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.

rails-upgrade/SKILL.md · 606 lines

How it starts

The opening of the file, as written. The whole thing — 606 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Rails Upgrade Assistant Skill

Skill Identity

Name: Rails Upgrade Assistant
Purpose: Intelligent Rails application upgrades from 2.3 through 8.1
Skill Type: Modular with external workflows and examples
Upgrade Strategy: Sequential only (no version skipping)
Methodology: Based on FastRuby.io upgrade best practices and "The Complete Guide to Upgrade Rails" ebook
Attribution: Content based on "The Complete Guide to Upgrade Rails" by FastRuby.io (OmbuLabs)

Dependencies

dual-boot skill (github.com/ombulabs/claude-code_dual-boot-skill) — Sets up and manages dual-boot environments using the next_rails gem. Covers setup, NextRails.next? code patterns, CI configuration, and post-upgrade cleanup. Must be installed for Step 2 of the upgrade workflow.
rails-load-defaults skill (github.com/ombulabs/claude-code_rails-load-defaults-skill) — Handles incremental load_defaults updates with tiered risk assessment (Tier 1: low-risk, Tier 2: needs codebase grep, Tier 3: requires human review). Used as the final step after the Rails version upgrade is complete.

Core Methodology (FastRuby.io Approach)

This skill follows the proven FastRuby.io upgrade methodology:

Incremental Upgrades - Always upgrade one minor/major version at a time
Assessment First - Understand scope before making changes
Dual-Boot Testing - Test both versions during transition using next_rails gem
Test Coverage - Ensure adequate test coverage before upgrading (aim for 80%+)
Gem Compatibility - Check gem compatibility at each step using RailsBump
Deprecation Warnings - Address deprecations before upgrading
Backwards Compatible Changes - Deploy small changes to production before version bump

Key Resources:

DELEGATE to the dual-boot skill for dual-boot setup with next_rails (see Dependencies)
See references/deprecation-warnings.md for managing deprecations
See references/staying-current.md for maintaining upgrades over time

Read the full file on GitHub · 606 lines

Files

What ships with it

47 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.

11d ago First seen · 606 lines · 73 tokens per session scan A 442ff55e5a27

Subscribe to this mod's changes

rails-upgrade is a skill published in the GitHub repository ombulabs/claude-code_rails-upgrade-skill (382 stars, last pushed yesterday), licensed MIT. It adds 73 tokens to every session and 7,866 once invoked, about $0.0004 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.

Claude Code Languages Planning Ruby claude-code-skill claude-code-skills ruby-on-rails technical-debt

test-driven-development

Strict red-green-refactor TDD workflow for implementing features, fixing bugs, or changing behavior in Rails applications. Enforces the discipline of writing a failing test before any production code. Use whenever you want to implement with TDD — whether a new feature, a bugfix, a refactor, or any behavior change.

thoughtbot/rails-consultant · 68 tokens

rails-conventions

Rootstrap Rails conventions. Use when writing, reviewing, or editing any Rails code — controllers, models, migrations, routes, views, mailers, initializers, locale files, or Rails config. Covers routing, ActiveRecord, migrations, i18n, time zones, mailers, assets, Bundler groups, and logging.

rootstrap/rails_api_base · 71 tokens

rspec-conventions

Rootstrap RSpec conventions. Use when writing, reviewing, or editing RSpec test files (spec//spec.rb, spec/railshelper.rb, spec/spechelper.rb, spec/support//.rb) or factories. Covers describe/context structure, let/subject, matchers, factories, mocking/stubbing, shared examples, and spec types (model, request…

rootstrap/rails_api_base · 82 tokens

ruby-conventions

Rootstrap Ruby style conventions. Use when writing, reviewing, or editing any Ruby source file (.rb, .rake, Gemfile, Rakefile, .gemspec, config.ru) to ensure code follows the Rootstrap Ruby style guide — covers layout, syntax, naming, classes/modules, exceptions, collections, strings, regexes, metaprogramming, and…

rootstrap/rails_api_base · 84 tokens

rails-audit-thoughtbot

Perform comprehensive code audits of Ruby on Rails applications based on thoughtbot best practices. Use this skill when the user requests a code audit, code review, quality assessment, or analysis of a Rails application. The skill analyzes the entire codebase focusing on testing practices (RSpec), security…

thoughtbot/rails-audit-thoughtbot · 130 tokens

rails-load-defaults

Incrementally upgrade Rails config.loaddefaults by walking through each newframeworkdefaults config one at a time. Use this skill whenever the user mentions loaddefaults upgrade, newframeworkdefaults, framework defaults, or wants to bring their Rails app's default configuration up to match their Rails version. Also…

ombulabs/claude-code_rails-load-defaults-skill · 120 tokens