Rails 7 → 8 Upgrade

Upgrade a Rails 7.x app to Rails 8.0. The hop is smaller than 6→7 but has real choices: Solid Queue vs your existing job backend, Propshaft vs Sprockets, the new authentication generator vs Devise. This skill walks the hop with the dual-boot pattern.

Why this matters

Rails 8 doesn't break much code. But the new defaults (Solid Queue, Solid Cache, Propshaft, Kamal 2) are adoptable — and "adopt all at once" is the wrong move. Stage the adoption.

The opinion

Dual-boot with next_rails. Hop 7.x → 7.1 → 7.2 → 8.0 (one minor at a time). Adopt Solid Queue / Cache / Cable only after the version is green — these aren't required by Rails 8, just the default for rails new. Keep Sprockets if you have a complex asset pipeline; migrate to Propshaft as a separate project. Skip the built-in bin/rails generate authentication if you have Devise.

Counter-position: a small app on Rails 7.x can do the upgrade in one PR. Dual-boot is for non-trivial apps where breaking master for a week is unacceptable.

The hop sequence

7.0 → 7.1 → 7.2 → 8.0