Why exporting WHEELS_ENV=production doesn't flip your app into production — and everything else about the config pipeline: the three-file load order, the .env chain that shadows OS variables, what production mode really changes, and the reload gate's fail-closed mechanics.
Three small pieces of plumbing turn 'the site gave me an error around lunchtime' into a single grep: the RequestId middleware, the /up health endpoint your app already ships, and a forty-line JSON logging pattern. Plus the two health-endpoint mistakes everyone makes once.
Wheels 4 denies cross-origin requests until you say otherwise — and the Cors middleware refuses the popular ways of saying it wrong. The deny-all breaking change, single-origin resolution, Vary: Origin, preflight handling, and the legacy-settings trap the framework defuses for you.
Wheels 4 ships session, API-token, and JWT authentication as pluggable strategies behind one Authenticator registry. Wiring up all three doors — with the sharp edges: private filters, dynamic finders, the 32-byte JWT secret minimum, and the inline-closure constructor that crashes Adobe ColdFusion.
The manual install that took the community two days to reverse-engineer in Wheels 3 is now two zip files and zero external dependencies. How to install, migrate, test, seed, and upgrade a Wheels 4 app with no CLI, no CommandBox, and no package manager — plus the new guides that document every step.
A complete how-to for sending email in Wheels 4.0 — the sendEmail controller helper, how email view templates resolve, multipart text+html, attachments, and the correct way to deliver mail from a background job. Includes the sharp edges that actually bite.
Wheels 4.0 has no ActiveStorage-style attachment system — and that's fine. This how-to walks the honest idiomatic upload flow end to end: fileField/fileFieldTag form helpers, the startFormTag multipart trap, native cffile in the controller, model validation over the result, and traversal-safe downloads with sendFile.
A practical, source-grounded tour of every cache Wheels 4.0 actually ships — action caching, query caching, partial and page caching — plus the honest truth about invalidation: there's no clearCache(key), so you live on short expiry times and full reloads.
A comprehensive Wheels 4.0 guide to model associations — hasMany, belongsTo, and hasOne, the exact dynamic methods each one generates, dependent-delete cascades, nested properties from form params, eager loading with include=, has-many-through, and polymorphic associations — with the sharp edges that bite in practice.
A worked how-to on Wheels 4.0 form helpers: object-bound fields that round-trip into params.user.email, the real HTML5 single-input helpers, and the two error-rendering helpers — plus the sharp edges that bite first.