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A Claude Code Skill to Upgrade Rails (From 2.3 to 8.1)

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, specializing in Rails upgrades since 2017

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

Comments

Very cool! I think the “estimated times” in the version upgrade guides may be unnecessary, however. “Estimated Time: 1-2 weeks” for a Rails 6.1 to 7.0 upgrade, for example. For a person, maybe. For an LLM, certainly not :-D

With that said, I am now letting Claude use the version upgrade notes to take a Rails 6 app to 7.1. Let’s see how it goes!

It took less than five minutes and got it 95% of the way there. I had some very ancient Rails 4-isms leaking in behind weird config settings I had to sort out (like belongs_to becoming non-optional by default, and some weird use of OpenStruct that needed replacing) but all in all very smooth.

That’s great to hear! I’m curious, how big was the application? Here is how we usually calculate Rails app size: https://www.fastruby.io/blog/rails/code-quality/how-we-estimate-rails-application-size.html

Not huge. A few thousand lines of code, sixteen declared gems (of 111 total). It’s the sponsor booking and scheduling system we use for our newsletters :)

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