Upgrade Rails

Upgrade Rails

When to use

Use this skill when upgrading Rails to a newer minor or patch version.

Background

Based on the Smooth Ruby and Rails Upgrades methodology. Key principles:

• Move by minor versions — upgrade incrementally through each minor version to the latest patch, never skip minors
• Separate Ruby and Rails upgrades — never combine them in one step
• Backport-first — preparatory commits (gem updates, deprecation fixes) land on main first, then the version bump is a small final step
• Small, reversible changes — each commit leaves tests green and is independently deployable

Upgrade strategy

For a Rails upgrade from e.g. 7.0.x to 7.2.x:

1. 7.0.x → 7.0.latest (patch only)
2. 7.0.latest → 7.1.latest (minor bump)
3. 7.1.latest → 7.2.latest (minor bump)

Never jump multiple minors at once.

Upgrade process

1. Pre-flight checks

cd apps/rails_application
bundle outdated rails
rails -v

Check current version, target version, and plan the minor-version steps.

2. Audit dependencies before the bump

bundle exec bundler-audit check --update

Address any CVEs in separate preparatory commits. Then attempt the update to see if gems conflict:

bundle update rails --conservative

If gems conflict, update blocking gems first in separate commits on main.

3. Fix deprecation warnings first

Run the full test suite and grep for deprecation warnings:

make test 2>&1 | grep -i deprecat

Fix each deprecation in its own commit, deployed to main before the version bump. This is the backport-first approach — preparatory work lands independently.

4. Update the Rails version constraint

In apps/rails_application/Gemfile, update:

gem "rails", "~> X.Y.0"

Then:

cd apps/rails_application
bundle update rails --conservative

Use --conservative to minimize collateral gem updates.

5. Run the full test suite

make test

Integration tests are the most critical — they exercise the full HTTP stack. Fix any failures before proceeding.

6. Check for deprecation warnings in the new version

make test 2>&1 | grep -i deprecat

Note these for fixing before the next minor bump.

7. Commit the version bump

Use the /commit skill. Good message example: "Upgrade Rails from 8.0.3 to 8.1.3"

8. Bump config.load_defaults (separate commit)

Bump config.load_defaults in config/application.rb to the new minor version. Before bumping:

1. Check the new defaults (search for new_framework_defaults_X_Y.rb in Rails source)
2. Grep the codebase for patterns that could break (e.g. unscoped .first/.last for raise_on_missing_required_finder_order_columns, path-relative redirects)
3. Bump, run make test, commit separately

9. (Optional) Run rails app:update

For minor version bumps, Rails provides an update task:

bin/rails app:update

This project has minimal Rails config surface (event-sourced architecture), so this is often unnecessary. Only run if the upgrade guide mentions config changes that matter.

Key areas to verify if tests fail

• config/application.rb — load_defaults, config changes
• config/environments/*.rb — new or changed settings
• config/initializers/ — framework initializers that may need updating
• bin/ scripts — may need regeneration
• Asset pipeline / CSS / JS tooling — often changes between minors

Important notes

• Always keep Ruby and Rails upgrades separate
• If a gem blocks the upgrade, update that gem first in a separate commit
• Each step must leave the test suite green
• Check stdgems.org when upgrading Ruby (separate from this skill)

Source: RailsEventStore/ecommerce — distributed by TomeVault.