Major Rails upgrades can be exciting.
New features, better performance, security improvements, and that satisfying feeling of keeping your codebase modern. But anyone who has been through enough Ruby on Rails upgrades knows that the process can also be unpredictable.
Yes, it is true...
Sometimes, it’s the smallest, most invisible thing that cause the biggest setbacks.
At RailsFactory, we’ve handled several major Rails upgrades across both legacy and greenfield applications this year. Despite our experience, one upgrade last month really humbled us.
The codebase was clean, test coverage was solid, and everything looked routine. But after the upgrade, we found ourselves chasing a frustrating regression for days. It wasn’t a complex issue. It wasn’t even an exotic edge case. It came from an overlooked initializer. Yes, a tiny, quiet part of the application that silently broke under the new version.
It took nearly a week to track down something that ultimately required a one-line fix.
That experience was a wake-up call. It reminded us that even when you think you’ve “seen everything” with Rails upgrades, there’s always something capable of slipping past your radar.
So instead of treating upgrades with ad-hoc troubleshooting bursts, we decided to build a structured process around them, starting with a pre-upgrade checklist.
Why a Rails Upgrade Checklist?
Checklists are powerful not because they handle complexity, but because they eliminate human inconsistency. Pilots use them. Surgeons use them. DevOps teams use them. And now, our Rails team does too.
The goal wasn’t to create another heavy, bureaucratic document. We wanted something lightweight, practical, and repeatable. A list of essential checks that would save us from the “we should have caught that” headaches.
What the Checklist Covers (High-Level)
Here’s a quick snapshot of what the 2026 version of our Rails Upgrade Checklist focuses on:
- Key Rails version changes that can silently break existing behavior.
- Initializers and config files most teams forget to review before upgrading.
- Gem compatibility checks to avoid dependency deadlocks.
- Database and ActiveRecord risks that surface only after migration.
- Caching, background jobs, and API behavior that may shift between versions.
- Deployment considerations for downtime-free upgrades.
- Greenfield app guardrails to keep future upgrades painless.
A Living Checklist, Updated for 2026
We’ve refined the checklist across multiple upgrades, and we’ll keep updating it as Rails evolves in 2026. If you want to explore or adapt it for your team, you can grab Rails Upgrade Checklist for 2026 here and save it for future.
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