Rails 5 → 6 Upgrade

The Zeitwerk autoloader transition is the headline event. Most code works; the breakage is autoload-related and unpredictable.

The opinion

Dual-boot with next_rails. Hop 5.0 → 5.1 → 5.2 → 6.0 → 6.1. Run Zeitwerk in "check" mode before flipping. Migrate Webpacker if needed (but consider deferring to Rails 7's importmap).

The hop sequence

5.0 → 5.1 → 5.2 → 6.0 → 6.1

Core patterns

Pattern 1: 5.x → 5.2 minor hops

Mostly deprecation cleanup. Notable: 5.2 ships Active Storage, encrypted credentials (replaces secrets.yml).