Completed Upgrading to Ruby 4.0.5 Using OpenCode Skills

Ruby Version Upgrade Completed in 10 Minutes

Previously running on Ruby3.4, I upgraded to Ruby4.0.5 today.
It took about 10 minutes. AI is intimidating.

Execution with Skills

Before performing the version upgrade, I created a skill for upgrading Ruby versions.
Here’s the beginning of the skill:

---
name: ruby-upgrade
description: Defines all procedures for Ruby version upgrades. Covers research, impact analysis, version switching, code fixes, testing, static analysis, and security checks.
---

When performing a major Ruby version upgrade (e.g., 3.4.x → 4.0.x), follow the steps in this skill.

## Workflow Overview

Research (destructive changes & impact investigation)
  ↓
Present investigation results → confirm with user to proceed/abort
  ↓
List of required modifications
  ↓
Check version (rbenv install --list)
  ↓
Modify .ruby-version
  ↓
(Ask user to install Ruby if necessary)
  ↓
Modification loop: fix one file → test → rubocop → security → review
  ↓
Final verification (all tests & static analysis)
  ↓
Commit & report


## Phase 1: Research

### 1.1 Determine Current Version and Target Upgrade Version

Check the current version from the following files:

- `.ruby-version`
- `Dockerfile`'s `ARG RUBY_VERSION`
- `Gemfile.lock`'s bundler version (indirectly)

Full skill details here
Ruby Version Upgrade Skill

Then executed the skill via OpenCode:

/ruby-upgrade Please upgrade to Ruby 4.0.5

Also Created a Rails Version Upgrade Skill

Getting carried away, I also created a Rails version upgrade skill. I haven’t tested it yet.
Rails Version Upgrade Skill

Upgrading Rails applications is one of the most challenging tasks, but having skills like this could make it easier. I think the key is the “repeat” instructions in the skill. This time I used DeepSeekV4. I’m gradually getting used to using cheaper models for looping tasks.