Rule 1 of 8 · Chapter I — App Architecture
Model-driven for process, canvas for task — never one mega-canvas for everything.
Why this rule exists
Canvas apps buckle under process complexity: security modeling, business rules, and form logic all become hand-rolled. Model-driven gives those for free but fights you on bespoke UX. One giant canvas app trying to be an ERP is the most expensive artifact in the platform.
In practice
Start from the data and process: if the core is records moving through stages with security roles, it is model-driven with canvas pages for the bespoke bits. If it is one focused task, canvas.