Upgrade Rails Without the Guesswork: rails-upgrade Skill

Where this fits

You're maintaining a legacy Rails 4.2 app that's been running in production for years. The team knows you need to upgrade, but the thought of manually tracking every breaking change, deprecation, and gem incompatibility across multiple major versions is paralyzing. You want a plan—not a vague roadmap, but a concrete, version-by-version migration path that your AI agent can execute and verify. That's exactly where rails-upgrade steps in: it turns a sprawling upgrade project into a structured, sequential checklist tailored to your codebase.

Why agents benefit

• Audits the entire application — reads your Gemfile, config/, and app/ to identify version-specific pain points, not just generic upgrade notes.
• Generates a sequential upgrade plan — enforces the “no skipping versions” rule, breaking a 4.2 → 8.1 journey into safe hops (4.2 → 5.0 → 5.1 → …).
• Surfaces breaking changes and deprecations — pinpoints exact code patterns that will fail or emit warnings in the target version, with references to the official changelog.
• Produces step-by-step migration guides — each step includes concrete code changes, gem updates, and test strategies, so the agent can execute and verify incrementally.
• Works with dual-boot setups — integrates with the next_rails gem and the companion dual-boot skill, letting you run both old and new Rails versions side-by-side in CI.

Practical scenarios

Multi-hop upgrade from Rails 4.2 to 6.1

Your agent runs rails-upgrade on a large e-commerce app. It produces a report listing all 4.2-specific deprecations (e.g., render :text, before_filter) and then walks through each intermediate version, checking your code against each target's breaking changes. The agent can apply patches, run the test suite, and commit after each successful hop—reducing the risk of a monolithic, error-prone migration.

Auditing a Rails 5.2 app before a planned upgrade

You're evaluating whether to upgrade to 6.1 or 7.0. The skill analyzes your current codebase and flags issues that would require significant refactoring (like ActiveRecord deprecations or Webpacker changes). This gives you a cost estimate before committing to a timeline.

Querying version-specific changes for a quick fix

You're not ready to upgrade, but you need to know if a particular method changed in Rails 6.0. Instead of digging through changelogs, you ask your agent: “What changed in ActiveSupport::TimeWithZone in Rails 6.0?” The skill retrieves the relevant section from its knowledge base (based on FastRuby.io's guide) and gives you a precise answer.

Add it to your agent workflow

Install it via npx:

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

Then invoke it in your agent conversation:

> Run the rails-upgrade skill on my project at ./my_app. Generate a report for upgrading from Rails 6.0 to 7.0.

The agent will analyze the app, produce a structured report, and start executing the first migration step.

Compare before adopting

Before you commit, evaluate against these criteria:

• Quality signals — Is the skill actively maintained? Check the commit history and issue responses. Does it reference official Rails guides and changelogs?
• Maintenance freshness — Rails releases are frequent; a skill that lags behind (e.g., doesn't cover Rails 8.1) will give stale advice.
• Alternatives — There are generic upgrade checklists and DSLs, but few are as deeply integrated with agent workflows. Compare with the official Rails upgrade guide or custom scripts.
• Workflow fit — Does it integrate with your CI and dual-boot setup? If you're already using next_rails, this skill is a natural companion.

Why it is worth tracking

With 381 stars and a clear methodology derived from FastRuby.io's production experience, rails-upgrade is a credible, battle-tested skill. It's not just a static document—it's an actionable, agent-friendly tool that turns a feared upgrade into a manageable process. Track it if you work on Rails apps that are more than one major version behind, or if you want to automate upgrade planning for multiple clients. When you're ready, the skill page on OpenAgentSkill has more details and community feedback.