Rails Upgrade Assistant Skill

A Claude Code skill that helps you upgrade Ruby on Rails applications from version 2.3 through 8.1.

What Does This Skill Do?

The Rails Upgrade Assistant analyzes your Rails application and generates:

• Detection Scripts - Bash scripts that scan your codebase for breaking changes specific to your target Rails version
• Comprehensive Upgrade Reports - Detailed migration guides with OLD vs NEW code examples from your actual codebase
• app:update Previews - Shows exactly what configuration files will change when you run rails app:update

The skill follows a sequential upgrade strategy—you upgrade one minor/major version at a time (e.g., 5.2 → 6.0 → 6.1 → 7.0), never skipping versions.

Why Trust This Skill?

This skill is built on real-world experience, not just documentation:

• 60,000+ developer hours of Rails upgrade experience
• Upgrades from Rails 2.3 to Rails 8.1 for clients worldwide
• Based on the methodology documented in "The Complete Guide to Upgrade Rails" ebook
• Created by the team at FastRuby.io, specialists in Rails upgrades since 2017

We've encountered (and solved) edge cases that don't appear in any documentation. This skill encapsulates that hard-won knowledge.

How to Use This Skill

Installation

Add this skill to your Claude Code configuration:

# Clone the repository
git clone https://github.com/ombulabs/claude-code_rails-upgrade-skill.git

# Add to your Claude Code skills directory
cp -r claude-code_rails-upgrade-skill/rails-upgrade ~/.claude/skills/

Basic Usage

In Claude Code, navigate to your Rails application directory and use natural language:

"Upgrade my Rails app to 7.2"
"Help me upgrade from Rails 6.1 to 7.0"
"What breaking changes are in Rails 8.0?"
"Create a detection script for Rails 7.1"

Workflow

1. Ask for an upgrade → Claude generates a detection script
2. Run the script → Script outputs rails_{version}_upgrade_findings.txt
3. Share the findings → Claude generates detailed reports based on your actual code
4. Implement the changes → Follow the step-by-step migration plan

Available Commands

Command	Description
/rails-upgrade	Start the upgrade assistant
"Upgrade to Rails X.Y"	Generate detection script for target version
"Here's my findings.txt"	Generate reports from detection results
"Show app:update changes"	Preview configuration file changes
"Plan upgrade from X to Y"	Get multi-hop upgrade strategy

Design Decisions & Best Practices

This skill implements the FastRuby.io upgrade methodology, which includes:

Dual-Boot Strategy

Run your application with two versions of Rails simultaneously using the next_rails gem:

# Gemfile
if next?
  gem 'rails', '~> 7.1.0'
else
  gem 'rails', '~> 7.0.0'
end

This allows you to:

• Run bundle install with two different dependency sets
• Execute bundle exec rake test against both Rails versions
• Deploy backwards-compatible changes to production before the version bump
• Catch compatibility issues early in CI

Sequential Upgrades Only

We never skip versions. Each Rails minor/major version introduces changes that build on previous versions. Skipping creates compound issues that are nearly impossible to debug.

✅ Correct: 6.0 → 6.1 → 7.0 → 7.1
❌ Wrong:   6.0 → 7.1 (skipping 6.1 and 7.0)

Deprecation-First Approach

Before upgrading:

1. Enable deprecation warnings in your current version
2. Fix all deprecation warnings
3. Deploy those fixes to production
4. Then bump the Rails version

This reduces the upgrade to a single Gemfile change.

What This Skill Doesn't Do

Be aware of these limitations:

Limitation	Explanation
Gradual deployments	This skill focuses on code changes, not deployment strategies. Rolling deployments, canary releases, and feature flags are outside its scope.
Debugging monkeypatching issues	If gems or your code monkeypatch Rails internals, you may encounter weird issues that require manual investigation.
Accurate time estimates	The difficulty ratings and time estimates are rough guidelines based on typical applications. Your mileage will vary based on codebase size, test coverage, and custom code complexity.
Automated code changes	The skill provides guidance and examples, but you implement the changes. It won't automatically refactor your code.
Gem compatibility resolution	While we note common gem version requirements, resolving complex dependency conflicts requires manual intervention.

Contributing

We welcome contributions! Here's how you can help:

Adding or Updating Version Guides

1. Fork the repository
2. Create a branch: git checkout -b add-rails-X-Y-guide
3. Add/update files in version-guides/
4. Follow the existing format and structure
5. Submit a pull request

Reporting Issues

• Found incorrect information? Open an issue
• Have a suggestion? We'd love to hear it
• Encountered an edge case? Share your experience

Guidelines

• Keep content factual and based on official Rails documentation
• Include code examples with BEFORE/AFTER patterns
• Test detection patterns against real codebases when possible
• Attribute sources appropriately

License

This project is licensed under the MIT License. See LICENSE for details.

Sponsors

This project is sponsored by:

OmbuLabs.ai | Custom AI Solutions

We build custom AI solutions that integrate with your existing workflows. From Claude Code skills to full AI agent systems.

FastRuby.io | Ruby Maintenance, Done Right

The Rails upgrade experts. We've been upgrading Rails applications professionally since 2017, helping companies stay current and secure.

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Questions? Open an issue or reach out to us at hello@ombulabs.com